Loopy Ideas Are Fine, If You’re an Entrepreneur

There is a belief within American media that a successful person can succeed at anything. He (and it’s invariably he) is omnicompetent, and people who question him and laugh at his outlandish ideas will invariably fail and end up working for him. If he cares about something, it’s important; if he says something can be done, it can. The people who are already doing the same thing are peons and their opinions are to be discounted, since they are biased and he never is. He doesn’t need to provide references or evidence – even supposedly scientific science fiction falls into this trope, in which the hero gets ideas from his gut, is always right, and never needs to do experiments.

Thus we get Hyperloop, a loopy intercity rail transit idea proposed by Tesla Motors’ Elon Musk, an entrepreneur who hopes to make a living some day building cars. And thus a fair amount of the media coverage is analysis-free summary of what Tesla already said: see stenography by ABC, Forbes, the Washington Post’s Wonkblog, and even BusinessWeek (which added that critics deal with “limited information”). Some media channels are more nuanced, sometimes even critical; the Wall Street Journal deserves especial credit, but Wonkblog also has a second, mildly critical post. But none has pressed Musk or Tesla about the inconsistencies in his proposal, which far exceed the obvious questions about the proposed $6 billion price tag (compare $53 billion in today’s money for California HSR). For better prior criticism, see James Sinclair’s post and Clem Tillier’s comment on California HSR Blog.

My specific problems are that Hyperloop a) made up the cost projections, b) has awful passenger comfort, c) has very little capacity, and d) lies about energy consumption of conventional HSR. All of these come from Musk’s complex in which he must reinvent everything and ignore prior work done in the field; these also raise doubts about the systems safety that he claims is impeccable.

In principle, Hyperloop is supposed to get people from Los Angeles to San Francisco in half an hour, running in a tube with near-vacuum at speeds topping at 1,220 km/h. In practice, both the costs and the running times are full of magic asterisks. The LA end is really Sylmar, at the edge of the LA Basin; with additional access time and security checks, this is no faster than conventional HSR doing the trip in 2:40. There is a crossing of the San Francisco Bay, but there’s no mention of the high cost of bridging over or tunneling under the Bay – we’re supposed to take it on faith the unit cost is the same as along the I-5 corridor in the Central Valley.

There is no systematic attempt at figuring out standard practices for cost, or earthquake safety (about which the report is full of FUD about the risks of a “ground-based system”). There are no references for anything; they’re beneath the entrepreneur’s dignity. It’s fine if Musk thinks he can build certain structures for lower cost than is normal, or achieve better safety, but he should at least mention how. Instead, we get “it is expected” and “targeted” language. On Wikipedia, it would get hammered with “citation needed” and “avoid weasel words.”

The worst is the cost of the civil infrastructure, the dominant term in any major transportation project’s cost. Hundreds of years of incrementally-built expertise in bridge building is brushed aside with the following passage:

The pods and linear motors are relatively minor expenses compared to the tube itself – several hundred million dollars at most, compared with several billion dollars for the tube. Even several billion is a low number when compared with several tens of billion proposed for the track of the California rail project.

The key advantages of a tube vs. a railway track are that it can be built above the ground on pylons and it can be built in prefabricated sections that are dropped in place and joined with an orbital seam welder. By building it on pylons, you can almost entirely avoid the need to buy land by following alongside the mostly very straight California Interstate 5 highway, with only minor deviations when the highway makes a sharp turn.

In reality, an all-elevated system is a bug rather than a feature. Central Valley land is cheap; pylons are expensive, as can be readily seen by the costs of elevated highways and trains all over the world. The unit costs for viaducts on California HSR, without overhead and management fees, are already several times as high as Musk’s cost: as per PDF-page 15 of the cost overrun breakdown, unit costs for viaducts range from $50 million to $80 million per mile. Overheads and contingencies convert per-mile cost almost perfectly to per-km costs. And yet Musk thinks he can build more than 500 km of viaduct for $2.5 billion, as per PDF-page 28 of his proposal: a tenth the unit cost. The unrealistically low tunnel unit cost is at least excused on PDF-page 31 on the grounds that the tunnel diameter is low (this can also be done with trains if they’re as narrow as Hyperloop, whose capsule seating is 2-abreast rather than 4- or 5-abreast as on HSR; see below on capacity). The low viaduct unit cost is not.

This alone suggests that the real cost of constructing civil infrastructure for Hyperloop is ten times as high as advertised, to say nothing of the Bay crossing. So it’s the same cost as standard HSR. It’s supposedly faster, but since it doesn’t go all the way to Downtown Los Angeles it doesn’t actually provide faster door-to-door trip times.

Nor is the system more comfortable for the passenger. Levitating systems can get away with higher cant than conventional rail because they sway less: Transrapid’s lateral acceleration in the horizontal plane is about 3.6 m/s^2 in Shanghai, and the company claims 4.37 m/s^2 is possible. On standard-gauge rail, the conversion rate is approximately 150 mm of total equivalent cant per 1 m/s^2. HSR cant tops at 180-200 mm, and cant deficiency tops at 180 mm for Talgos and 270-300 mm for medium-speed Pendolinos, so about 2.5 m/s^2 at high speed; this was shown safe by simulation in Martin Lindahl’s thesis, which is also a good source for track construction standards.

But Hyperloop goes one step further and proposes a lateral acceleration of 4.9 m/s^2: 0.5 g. This is after canting, according to the standards proposed:

The Hyperloop will be capable of traveling between Los Angeles and San Francisco in approximately 35 minutes. This requirement tends to size other portions of the system. Given the performance specification of the Hyperloop, a route has been devised to satisfy this design requirement. The Hyperloop route should be based on several considerations, including:

  1. Maintaining the tube as closely as possible to existing rights of way (e.g., following the I-5).
  2. Limiting the maximum capsule speed to 760 mph (1,220 kph) for aerodynamic considerations.
  3. Limiting accelerations on the passengers to 0.5g.
  4. Optimizing locations of the linear motor tube sections driving the capsules.
  5. Local geographical constraints, including location of urban areas, mountain ranges, reservoirs, national parks, roads, railroads, airports, etc. The route must respect existing structures.

For aerodynamic efficiency, the velocity of a capsule in the Hyperloop is

  • 300 mph (480 kph) where local geography necessitates a tube bend radii < 1.0 mile (1.6 km)
  • 760 mph (1,220 kph) where local geography allows a tube bend > 3.0 miles (4.8 km) or where local geography permits a straight tube.

These bend radii have been calculated so that the passenger does not experience inertial accelerations that exceed 0.5 g. This is deemed the maximum inertial acceleration that can be comfortably sustained by humans for short periods. To further reduce the inertial acceleration experienced by passengers, the capsule and/or tube will incorporate a mechanism that will allow a degree of ‘banking’.

0.5 g, or 4.9 m/s^2, is extreme. Non-tilting trains do not accelerate laterally at more than 1.2 m/s^2 in the plane of the track (i.e. after accounting for cant), and at high speed they have lower lateral acceleration, about 0.67 m/s^2 with limiting cases of about 0.8 for some tilting trains relative to the plane of the train floor. For example, the Tokaido Shinkansen has 200 mm of cant and maximum speed of 255 km/h on non-tilting trains on 2,500-meter curves, for 100 mm of cant deficiency, or 0.67 m/s^2.

The proposed relationship between curve radius and speed in the Hyperloop standards is for a lateral acceleration much greater than 4.9 m/s^2 in the horizontal plane: 480 km/h at 1,600 meters is 11.1 m/s^2. This only drops to 5 m/s^2 after perfectly canting the track, converting the downward 9.8 m/s^2 gravity and the sideways acceleration into a single 14.8 m/s^2 acceleration vector downward in the plane of the capsule floor, or 5 m/s^2 more than passengers are used to. This is worse than sideways acceleration: track standards for vertical acceleration are tighter than for horizontal acceleration, about 0.5-0.67 m/s^2, one tenth to one seventh what Musk wants to subject his passengers to. It’s not transportation; it’s a barf ride.

Even 4.9 m/s^2 in the horizontal plane is too much. With perfect canting, it combines with gravity to accelerate passengers downward by 11 m/s^2, 1.2 m/s^2 more than the usual, twice as high as the usual standards. Motion sickness is still to be fully expected in such a case. Transrapid’s 4.37 m/s^2, which adds 0.93 m/s^2 in the vertical component with perfect canting, is the limit of what’s possible.

Speaking of vertical acceleration, this gets no comment at all in the Hyperloop proposal. At 1,220 km/h, it is very hard to climb grades, which would require very tall viaducts and deep tunnels under mountains. Climbing grades is easy, but vertical acceleration is such that the vertical curve radius has to be very large. A lateral acceleration of 0.67 m/s^2 would impose a minimum vertical curve radius of 170 km, versus 15 km at 360 km/h HSR speed. Changing the grade from flat to 2% would take 3.4 km, and changing back would take the same, so for climbing small hills, the effective average grade is very low (it takes 6.8 km to climb 68 meters).

Nor does jerk get any treatment. Reversing a curve takes several seconds at the cant and cant deficiency of conventional HSR (about 3 seconds by Swedish standards, more by German ones); reversing a curve with the extreme canting levels of Hyperloop would take much longer. Maintaining comfort at high total equivalent cant requires tight control of the third derivative as well as the second one; see a tilting train thesis for references.

The barf ride that is as expensive as California HSR and takes as long door-to-door is also very low-capacity. The capsules are inexplicably very short, with 28 passengers per capsule. The proposed headway is 30 seconds, for 3,360 passengers per direction per hour. A freeway lane can do better: about 2,000 vehicles, with an average intercity car occupancy of 2. HSR can do 12,000 passengers per direction per hour: 12 trains per hour is possible, and each train can easily fit 1,000 people (the Tokaido Shinkansen tops at 14 tph and 1,323 passengers per train).

But even 30 seconds appears well beyond the limit of emergency braking. It’s common in gadgetbahn to propose extremely tight headways, presuming computerized control allowing vehicles to behave as if they’re connected by a rod. Personal rapid transit proponents argue the same. In reality, such systems have been a subject of research for train control for quite a while now, with no positive results so far. Safety today still means safe stopping distances. If vehicles brake at a constant rate, the safe headway is half the total deceleration time; if a vehicle brakes from 1,220 km/h to zero in 60 seconds, the average acceleration is more than 5 m/s^2, twice the current regulatory safety limit for passengers with seat belts.

Most of this could be chalked to the feeling of some entrepreneurs that they must reinvent everything. The indifference to civil engineering costs, passenger comfort issues, and signal safety could all be chalked to this. So could the FUD about earthquake safety of HSR on PDF-page 5.

However, one thing could not: the chart on PDF-page 9 showing that only the Hyperloop is energy-efficient. The chart has a train consuming nearly 900 megajoules per person for an LA-San Francisco trip, about as much as a car or a plane; this is about 1,300 kJ per passenger-km. This may be true of Amtrak’s diesel locomotives; but energy consumption for HSR in Spain is on average 73 Watt-hour (263 kJ) per passenger-km (see PDF-page 17 on a UIC paper on the subject of HSR carbon emissions), one fifth as much as Tesla claims. Tesla either engages in fraud or is channeling dodgy research about the electricity consumption of high-speed trains.

Indeed, a train with a thousand seats, 20 MW of power drawn, 60% seat occupancy, and a speed of 360 km/h can only ever expend 333 kJ per passenger-km while accelerating, and much less while cruising (acceleration at lower speed requires more energy per unit of distance, but cruising at lower speed expends only a fraction of the energy of full-power acceleration). Tesla’s train energy consumption numbers do not pass a sanity check, which suggests either reckless disregard for the research or fraud. I wouldn’t put either past Musk: the lack of references is consistent with the former, and the fact that Musk’s current primary endeavor is a car company is consistent with the latter.

There is no redeeming feature of Hyperloop. Small things can possibly be fixed; the cost problems, the locations of the stations, and the passenger comfort issues given cost constraints can’t. Industry insiders with ties to other speculative proposals meant to replace conventional rail, such as maglev, are in fact skeptical of Hyperloop’s promises of perfect safety.

It’s possible to discover something new, but people who do almost always realize the context of the discovery. If Musk really found a way to build viaducts for $5 million per kilometer, this is a huge thing for civil engineering in general and he should announce this in the most general context of urban transportation, rather than the niche of intercity transportation. If Musk has experiments showing that it’s possible to have sharper turns or faster deceleration than claimed by Transrapid, then he’s made a major discovery in aviation and should announce it as such. That he thinks it just applies to his project suggests he doesn’t really have any real improvement.

In math, one common sanity check on a result is, “does it prove too much?” If my ten-page paper proves a result that implies a famous open problem, then either my paper is wrong or I’ve proved the famous open problem, and it’s up to me to take extra care to make sure I did not miss anything. Most people in this situation do this extra step and then realize that they were subtly wrong. If a famous question could be solved in ten pages, it probably wouldn’t still be open. The same is even true in undergrad-level proof classes: if your homework answer proves things that are too strong, you’ve almost certainly made a mistake.

Musk’s real sin is not the elementary mistakes; it’s this lack of context. The lack of references comes from the same place, and so does the utter indifference to the unrealistically low costs. This turns it from a wrong idea that still has interesting contributions to make to a hackneyed proposal that should be dismissed and forgotten as soon as possible.

I write this not to help bury Musk; I’m not nearly famous enough to even hit a nail in his coffin. I write this to point out that, in the US, people will treat any crank seriously if he has enough money or enough prowess in another field. A sufficiently rich person is surrounded by sycophants and stenographers who won’t check his numbers against anything.

There are two stories here. In the less interesting one, Musk is a modern-day streetcar conspiracy mogul: he has a car company, he hopes to make money off of it in the future and uses non-generally accepted accounting to claim he already does, and he constantly trash-talks high-speed rail, which competes with his product. Since he’s not proposing to build Hyperloop soon, it could be viewed as clever distraction or FUD.

The more interesting possibility, which I am inclined toward, is that this is not fraud, or not primarily fraud. Musk is the sort of person who thinks he can wend his way from starting online companies to building cars and selling them without dealerships. I have not seen a single defense of the technical details of the proposal except for one Facebook comment that claims, doubly erroneously, that the high lateral acceleration is no problem because the tubes can be canted. Everyone, including the Facebook comment, instead gushes about Musk personally. The thinking is that he’s rich, so he must always have something interesting to say; he can’t be a huckster when venturing outside his field. It would be unthinkable to treat people as professionals in their own fields, who take years to make a successful sideways move and who need to be extremely careful not to make elementary mistakes. The superheros of American media coverage would instantly collapse, relegated to a specialized role while mere mortals take over most functions.

This culture of superstars is a major obstacle frustrating any attempt to improve existing technology. It more or less works for commercial websites, where the startup capital requirements are low, profits per employee are vast, and employee turnover is such that corporate culture is impossible. People get extremely rich for doing something first, even if in their absence their competitors would’ve done the same six months later. Valve, a video game company that recognizes this, oriented its entire structure around having no formal management at all, but for the most part what this leads to is extremely rich people like Bill Gates and Mark Zuckerberg who get treated like superstars and think they can do anything.

In infrastructure, this is not workable. Trains are 19th-century technology, as are cars and buses. Planes are from the 20th century. Companies can get extremely successful improving the technology somehow, but this works differently from the kind of entrepreneurship that’s successful in the software and internet sectors. The most important airline invention since the jet engine is either the widebody (i.e. more capacity) or the suite of features that make for low-cost flights, such as quick turnarounds. What Southwest and its ultra low-cost successors have done is precious: they’ve figured how to trim every airline expense, from better crew utilization to incentives for lower-transaction cost booking methods. This requires perfect knowledge of preexisting practices and still takes decades to do. The growth rate of Microsoft, Google, and Facebook is not possible in such an environment, and so the individual superstar matters far less than a positive corporate culture that can transmit itself over multiple generations of managers.

There is plenty of room for improvement in HSR technology, then, but it’s of a different kind. It involves adapting techniques used by low-cost airlines to reduce costs, as SNCF is doing right now with its new low-cost TGV product. It perhaps involves controlling construction costs more tightly, though $5 million per km for viaducts seems like an impossible fantasy. But it has to come from within the business, or from someone who intimately understands the business.

And with the kind of success that US media harps on, this is almost impossible to do domestically. Someone as smart as Musk, or any of many other Silicon Valley entrepreneurs, could find a detailed breakdown of the operating and construction costs of civil infrastructure, and figure out ways of reducing them, Megabus- or Southwest-style. That’s what I would do if I had the unlimited resources Musk has: I’d obtain unit costs at far greater detail than “X meters of tunnel cost $Y” and compare what New York is doing wrong that Madrid is doing right. But I don’t have the resources – in money, in ability to manage people, in time. And the people who do are constantly told that they don’t need to do that, that they’re smart enough they can reinvent everything and that the world will bow to their greatness.

Update: people all over the Internet, including in comments below, defend the low cost projections on the grounds that the system is lighter and thinner than your average train. The proposal itself also defends the low tunneling costs on those same grounds. To see to what extent Musk takes his own idea seriously, compare the two proposals: the first for a passenger-only tube, and the second for a larger tube capable of carrying both passengers and vehicles. On PDF-pp. 25-26, the proposal states that the passenger-only tube would have an internal diameter of 2.23 meters and the passenger-plus-vehicle tube would have an internal diameter of 3.3 meters, 47% more. Despite that, the tunneling costs on PDF-p. 28 are $600 and $700 million, a difference of just 17%.

The same is true of the “but the Hyperloop capsule is lighter than a train” argument for lower pylon construction costs. Together with the differences in tube thickness posited on PDF-p. 27, 20-23 mm versus 23-25, there is 60% more tube lining in the passenger-plus-vehicle version, but the tube and pylons are projected to cost just 24% more. In this larger version, the twin tube has 0.025*3.3*pi*2 = 0.5 cubic meters of steel per meter of length, weighing about 4 tons. This ranges from a bit less than twice to a bit more than twice the weight of a train. To say nothing of the pylons’ need to support their own considerable weight, which is larger than for HSR due to the need for taller viaducts coming from the constrained ability to change grade. They are far more obtrusive than trees and telephone poles, contra the claims of minimal obtrusiveness and disruption.

Update update (12/24): Hyperloop is in the news again; I’ve been getting a lot of pingbacks copying this article. You can read the plan here; the construction costs are now up from a laughable sub-$10 million per kilometer to $10-30 million, which is perfectly feasible if you’re building in flat terrain and if what you’re building is conventional rail and not a vactrain. There’s virtually no discussion of why the costs are so much lower, just an assurance that the team ran the numbers and that they’re looking into minimizing the costs of the construction material (costs that, for conventional HSR, are a small proportion of the total construction costs – concrete is cheap, it’s pouring it that’s expensive). On PDF-p. 19 of the new plan, the accelerations are explicitly stated to be 0.5 g in normal service, which the person heading the team trying to build it claims is not a barf ride in the article, but which is in reality is again worse than the acceleration felt by passengers on an airplane taking off. There already exists a mode of transportation that involves security theater, travel at 1,000 km/h, poor comfort, and motion sickness.


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  2. Brett

    To be fair to Musk, the released proposal seemed about two steps away from writing down the thing on a restaurant napkin. I don’t think any of the numbers on how much it would cost were intended to be taken seriously.

    Good post, though. Would putting a whole train line inside of a tube defray some of the NIMBYism that occasionally pops up in response to these projects? It might reduce noise complaints.

    • Alon Levy

      The problem with putting everything in a tube is that it’s expensive – all the ventilation and evacuation issues arising from tunnels are present, much in the same way a tunnel is more expensive than a trench. It also increases air resistance, which requires a much larger tube diameter than the minimum necessary to enclose the train, which increases costs even more.

      If the point is to reduce noise, there are noise barriers, which are way cheaper than enclosing everything.

      • Charles Smith

        All serious proposals for high speed tubes that I’ve seen assumed evacuation, with the vehicles carrying their own atmosphere.

        • Barry

          Which means an extremely heavy tube, with nearly perfect sealing. Any failure in the sealing would mean that the capsule is now trying to travel at hundreds of mph in a tube with air, with the air basically confined in front of it. IOW, crushed.

          • tigertoo

            I guess you didn’t read the spec of the hyper loop. Its not a total vacuum its partial to reduce resistance. And also elevate the need for a complete seal. Air infront of the capsule is drawn in and compressed. then pushed out for acceleration and provide the air bearing frictionless cushion. simple

      • Wilson

        This comment seems to suggest that you didn’t understand the main point of the proposal, which was partially evacuating the tube to not only reduce drag but also allow for the use of air bearings.

        • cosmicbuzz

          Good point. I didn’t realize that the differentials between low air pressure at top of pod and air bearings is important for levitation.

          I also spotted Alon’s “It also increases air resistance, which requires a much larger tube diameter than the minimum necessary to enclose the train, which increases costs even more.”

          Alon obviously did not understand that the air intake of the pod designed by Musk solve the problem, and provided several benefits.

          • Alon Levy

            The point about air resistance is specific to non-evacuated transportation, such as any proposals to put HSR in a (non-evacuated) tube.

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  4. danR

    Regarding safety, consider the following which I’ve posted elsewhere in one form or another:

    If you see the graphic of this thing in the tube, it’s actually more train-like than ‘capsule’.

    When a normal train goes into a bunching-up failure, it spreads itself all over the roadbed or the neighborhood. In a tunnel, the tunnel is massively strong and the debris just jams to a stop.

    This thing is going along with the kinetic energy of a bus traveling at around 250 meters per second. If it bunch-jams, from some transient instability and then positive feedback oscillation (will it happen? build it and find out later, riiighht…. ) it will take the whole tube with it at the point.

    What happens to the those passengers will be a footnote to the chain-reaction of what then happens with the open tube behind, as the open air finds a sudden vacuum at its mouth. It accelerates down the tube to the next capsule, and the tube again ruptures, with equally gratifying CGI movie action. And so forth.

    • Billy

      Very fertile imagination you have.

      This thing is sliding on a smooth surface with very little air pressure in front of it. There is no vacuum, so a rupture will merely cause re-pressurization while the trains behind have already braked.

      “build it and find out later” applies to everything humanity has built, doesn’t it?

      • Barry

        “This thing is sliding on a smooth surface with very little air pressure in front of it. There is no vacuum, so a rupture will merely cause re-pressurization while the trains behind have already braked.”

        Which means in a best plausible case scenario, the system has incredible down-time, since it needs to be an evacuated tube hundreds of kilometers long.

        • danR

          Billy has missed the point altogether. As far as the ambient pressure is concerned, that tube is a vacuum. Not a ‘hard’ vacuum, but let’s not quibble about mere millibars. As that massive plug of air races back up the open tube, it forward edge will quickly reach the speed of sound and it won’t matter how much residual air will build up in front of the next pod. It will be slammed by a gaseous piston and that section of tube will burst open like a bomb went off. The chain reaction would go right up the tube.

          If emergency gates were to be installed (hundreds of them) kicked in, that air-piston would at least blow out the tube ahead of the gates unless a hundred feet or more of the tube ahead of the gate were heavily reinforced. Meaning more weight to support. Meaning mounting costs.

          He’s also missed the point of my ‘footnote’ understatement. If that single event alone were to happen, the whole system would be shut down permanently, and it would be history the next day. Nobody would ever trust that thing again, however much more money they threw at it.

  5. JJJJ

    I glossed over all your math, well beyond my understanding. I’ll assume it’s all correct.

    I do think you’re 100% right on in your analysis of the culture around rich people, successful inventors, and the media. It was shocking how many people took every claim as the gospel because it came from someone who is very successful in a completely different industry.

    And not just random comments on articles – there were many – but legitimate media sources assuming every word was true. Sort of in the same way they reprint press releases without even a cursory fact check… It’s a serious problem in the tech world. Most tech websites are 70% press release re-writes, 25% hands-on and reviews, and 5% actual reporting. Maybe less.

    I was amused by one string of comments in an article where person A focused on a tiny detail (ie, bathrooms) and person B would come in and say “stop being skeptical! hes a genius! He though of everything! Look at page 15, bathrooms are addressed! He brought up every concern before you could and solved it!” Both person A and B, meanwhile, sort of missed out that the GIANT details, like crossing the Sf Bay, were not addressed. It’s fascinating.

    • Alon Levy

      Metafilter has a much better thread on this. The equivalents of Person A talk about costs and such – one of the posters there noted how even with the smaller tube diameter, the tunnel cost assumption is fantastically low – and then the equivalents of Person B say Musk is a genius and must not be criticized by mortals without superpowers.

      • Nathanael

        Yeah. *sigh*.

        After some fairly detailed analysis, I understand the business model of all four of Elon Musk’s successful companies.

        In the case of SpaceX, the business model is “use computers to do all the rocketry stuff which was previously done with complicated electromechanical devices, it should be cheaper”. It was cheaper, therefore the company was successful at selling its services for satellite launches.

        In the case of Tesla, the business model is “Electric cars are already solved technology, but for some reason nobody else is selling them to the rich, so build them starting at the top of the market and working down, like all the car companies from 1890-1930 did.” This should obviously work, and so it has been working.

        In the case of Solar City, the business model is “Finance solar panels the way people finance cars and houses. Solar panels have a payback over the course of years, therefore you can get people to finance them.” This should obviously work, though it has all the risks inherent in a financing business.

        PayPal pretty much speaks for itself: allow people to make online payments with lower overhead than the very-high-overhead credit card companies.

        By contrast, the Hyperloop is just fantasy material. The failure to actually look at civil engineering costs is pathetic. It *is* absolutely typical for Musk to lowball cost estimates, and he’s done so repeatedly, including at least two high-profile cases with Tesla Motors alone.

        • Barry

          “In the case of Tesla, the business model is “Electric cars are already solved technology, but for some reason nobody else is selling them to the rich, so build them starting at the top of the market and working down, like all the car companies from 1890-1930 did.” This should obviously work, and so it has been working.”

          Actually, it’s ‘set up a tiny car company selling exotic niche cars to the rich.’ That might make money, and in an incredibly good situation might allow expansion, although my money would be on a growing Tesla Corp. simply being copied by the existing car companies.

          • Nathanael

            Tesla is going to have no trouble whatsoever moving down into the $50K car market, though it will take a while.

            There is a fundamental institutional attitude problem among the existing car companies which is causing them to sabotage themselves and be unable to compete with Tesla. It’s been very interesting to watch. It’s pretty obvious how to design an electric car “from the ground up”, but every last one of them has insisted on modifying a gasoline car design. It’s institutional culture. Eventually this may change but it’s going to take years, possibly decades.

            As for the sub-$50K car market (and Tesla will have trouble getting into that market), I’m not sure it’s even going to exist in 20 years. With today’s income distribution, if you can’t afford to spend $50K on a car, you probably can’t really afford to insure a car or buy gas for it, either.

        • al

          SpaceX also used a very high power to weight ratio rocket engine NASA developed as the basis of their rocket engine family. They also have most of the business activity (except the engine test firing and space launch) at one site. The same can be said for Tesla. Everything from design, manufacturing, launch control and various corporate offices are there. If you look at the other space launch providers, they’re spread out. It cuts down on communication and drives up overhead and logistical costs. There is also the Pork attached to legacy space launch providers. The Space Launch System, that is derogatorily referred to as the Senate Launch System, is just such a pork barrel project. That business as usual drives up costs.

        • harshsingh08

          $52B dollars to build a HSR railway is pathetic. It’s not the actual material required to build the job, it’s the incredulous waste created by state departments to over-inflate their ego and fill the pocketbooks of useless contractors.

          400 mile long pipelines used to transport crude and gas can be built for $2B, so when a number like $52B comes up, and a proposed amount of $6B for a plastic tube seems pretty reasonable to me.

      • Oliver

        Congratulations Jake – you closed the loop 😉
        I came here through a link posted by PHK in a Danish tech forum.

  6. Charles Smith

    If one wished to do something hyperloop like, there was a well thought out piece on it in Scientific American based on some work from ?Northwestern?. But, that was 20 years ago, when men were men and passengers weren’t Col. Stapp.

    • Rick LaPlace

      Think about 50 years ago when men were men and the US dreamed about new frontiers. Today everything is too expensive or too dangerous or too threatening to the planet for the helmet-wearing knee-pad clad bicycling citizens to consider.

      • Oliver

        Rick, I believe you’re missing the point – this is not about danger, it’s about comfort. Musk (in his presentation) targets the hyperloop at commuters – business customers, essentially. Not test pilots or astronauts. They’ll expect to be able to have a coffee and make some powerpoints / do their email on the way to their office / next meeting / whatever. That’s what they’re used to from flying or taking HSR.
        With g-forces that high, you can’t do work during the ride and many people will get motion sickness.

        • John

          A typical airliner will do +.4gs for takeoff and +-.25 in turns/changes in altitude. Hyperloop can be tuned to come down to these levels if need be and still be much faster than HSR. All of this talk of a horrible barf-inducing roller-coaster ride is silly. Especially since the forces are completely predictable and riders could be shown some kind of display giving them feedback (the most unpleasant thing on an airliner IMHO is *unanticipated forces*).

          I also find it strange that the assumption is that this would be all business people. When I look at a typical airplane flight between LA-SF or Boston-NYC, it is typically at least 50% “civilians”. On a 35 minute ride (or lets say 40 to bring down the g-forces), I don’t know that anyone is going to be *so worried* about drinking coffee or making slides. I can easily spend almost that much time riding the subway into Boston on a typical day.

          Let’s say you treble the $20 fare that Musk is talking about, it is *still $40+ cheaper* than Acela between Boston and NYC. That opens it up to a lot of people beyond business people.

          • Alon Levy

            How about raising the fare by a factor of 100? Or cutting it by a factor of 10? Why accept $20 as a meaningful number?

            In reality, the capacity of Hyperloop is so low that the market-clearing fares would be high. If you can’t have lots of passengers, you can price things higher: that’s what Acela does, due to its laughably low capacity (304 people per train, vs. more than 1,000 for Shinkansen and TGV, with average fares of $0.53 per passenger-km vs. $0.2-0.24 and an upper bound of $0.18 respectively). You also have to charge more to pay off construction costs. California HSR is capable of spreading construction costs among more passengers.

            Avoiding barfy deceleration rates would reduce capacity even more – no 30-second headways for you unless you decelerate at a constant rate of 5.6 m/s^2. The snarky comment is that with so little passenger comfort, the market-clearing fare might just be $20.

            The most unpleasant parts on an airplane, at least for me, are takeoff and landing. I can anticipate them just fine visually, which is a lot better than merely being told about them in advance – in fact, on tilting trains, the tilt mechanism is set up to compensate only 80% centrifugal force so that passengers have some visual feedback. The problem is that the acceleration force I’m subjected to is still very large.

      • ianbrettcooper

        I’ve been a cyclist for over 40 years. I’ve yet to meet anyone who cycles in kneepads.

  7. JCW

    It’s pretty obvious why Musk’s infrastructure could plausibly be substantially cheaper than conventional rail’s: it’s all about scale. The low-mass “Hyperloop” capsules would generate substantially lower forces than conventional heavy locomotive-driven passenger trains, and so the infrastructure would need less reinforcement.

    Clearly Musk’s 500kg per seat is only slightly lower than the Shinkansen’s, but the total mass of the vehicles differs by two orders of magnitude — so of course the infrastructure costs will be different! (consider tramways vs passenger rail). I don’t claim Musk’s right, but you’re not presently comparing like with like.

    Much of the rest of your post seems a touch muddled in the same vein. Your principal mistake is treating the proposal as a refinement of elevated rail. It’s not; it’s different in almost every detail. This is why you are confused about the “short” capsules, and about the stopping distances (though Musk also seems confused — he mentions an emergency mechanical brake, but supplies no details: how, hovering in a partially-evacuated tube with no propulsion?)

    As for your suggestion that Musk should instead be content to pick over the details of existing schemes and refine them incrementally, that’s certainly a job worth doing — but perhaps not one for an innovator who employs many highly-trained, highly-intelligent, and imaginative engineers.

    [on a final more pleasant note, as a maths graduate I enjoyed your aside about proofs, though I’ve never thought I’d solved a famous open problem…]

    • JCW

      One more thing: you mention a crossing of the SF bay. In the map on page 40 the route appears not to cross the bay; in the map on page 49 it looks as though the route does cross the bay, but on closer inspection this looks like an error (as the red circles do not extend all the way up).

      If the present intention (which I claim is ambiguous) is not to cross the bay then your objection to that is also invalid (and those in the media not making a fuss about it are perhaps correct not to until clarification is received).

      • Jeff L

        If Musk’s plan doesn’t go to downtown LA or downtown SF, why does he insist on comparing costs to the HSR which does that? Also where is his discussion of the practical problems of having such terminus locations within the broader transportation system?

        • Oliver

          …which matches quite well with the slighly unfair comparison of transit times in his presentation: Plane is airport to airport (we all know this isn’t even close to the total transit time), hyperloop is suburb to suburb while HSR is downtown to downtown.

        • tjm

          Oh, it’s no problem–once you get off at the edge of town, there’ll be a fleet of Tesla electric cars that you can rent and go downtown. (You can even rent them using PayPal while you’re still in the Hyperloop.) Elon’s a genius, he’s thought of everything.

    • Alon Levy

      The mass of the tube per unit of length is comparable to the mass of an HSR train, because the tube needs to be strong enough to protect the near-vacuum. So it’s not a difference of orders of magnitude at all. The pylons will need to support a similar mass, which means the civil infrastructure cost is the same as that of elevated rail. If anything, the pylons should be more expensive, because the earthquake safety system needs to be more delicate, again to protect the near-vacuum.

      There’s a large range of mass for vehicles that run on viaducts, but it barely if at all affects the cost of the infrastructure. The extra cost from making the Initial Construction Segment compatible with heavier FRA-compliant trains in case there’s no more money and they can only run Amtrak San Joaquins on the line is small – and that’s for a train that weighs nearly twice as much as a TGV or Shinkansen per unit of length. And Vancouver’s saving a lot of money on station construction by running very short trains, but it’s saving none on the viaducts. Likewise, mainline rail and tramways cost approximately the same within each category of civil infrastructure – elevated, underground, at-grade on an existing railroad right-of-way, at-grade in a new right-of-way.

      • Phil

        >The mass of the tube per unit of length is comparable to the mass of an HSR train

        The important thing is how it compares to the mass of the concrete trackway, not the train. How heavy is that again?

        Also live loads != dead loads, so you’re still a factor of >2 off.

        • Alon Levy

          Fair. I do not know the standards for slab thickness for HSR, so I’m going to use low-speed standards instead; the cost of low-speed urban rail viaducts are also quite high, in the same ballpark as urban HSR viaducts. In Barcelona, the Line 9 subway is in a double-deck tunnel, with a 40 cm wide concrete slab separating the two levels (link). So, 40 cm times about 4 m track spacing times 2,500 kg/m^3 yields 4,000 kg/m per track. That’s 8 t/m for a two-track system, which is twice as heavy as the tube. The concrete sleepers add less than a ton between the two tracks, and rail tracks weigh at the heaviest 60 kg/m. So perhaps 9 t/m for both tracks, still about twice as heavy.

          A factor of two mass difference does not translate to a factor of ten cost difference. It doesn’t come close to translating to a factor of two cost difference. Musk doesn’t believe that of his own system – his larger-diameter version has 60% more mass per unit of length than his smaller-diameter version but costs only 24% more. The extra costs California HSR has to incur to make the system compatible with the heavier loads of Amtrak trains in case there is no further funding and Initial Construction Segment is only used by Amtrak diesels are small.

          • Alon Levy

            First, HSR can use slab track. CAHSR’s cost estimates now assume it; slab track does not have the extra ballast weight, but it’s still more expensive up-front than ballast, though its maintenance costs are lower.

            Second, I’m specifically mentioning things that aren’t just HSR, since the costs for elevated structures that are less heavily built aren’t magically lower than for HSR. The grade separations on Metro-North often have neither concrete nor gravel, and the same is true of some steel els in New York: there’s track, wooden sleepers underneath, and structures supporting them, but no ballast or slab. These don’t cost $5 million per kilometer to construct – check e.g. the Penn Design cost estimates for suburban grade separations, or Amtrak’s costs of rebuilding (but not raising) low bridges over water that are similarly light.

            Third, CAHSR claims 25 t/m on PDF-page 27 of technical memo 2.3.3, but this appears to include the box girder, for which the equivalent structure in Hyperloop is part of the pylon itself so it’s not part of the calculated tube mass.

          • Joey

            Phil: the CAHSR design standards are far from ideal, but even still, did you account for the fact that most of that space is hollow? Also, actually putting gravel and ballasted track on top of a viaduct isn’t common anymore. Slab track is much more common, in which the rails are fastened directly to a concrete railbed.

          • Phil

            Alon Levy: Your argument that “the pillars are too cheap” is that the >5x heavier CAHSR isn’t that cheap (which kind of begs the question, don’t you think?) and weight doesn’t matter because lighter urban elevated rail isn’t any cheaper (duh, because it’s urban construction)

            Joey: Yep, I know they’re hollow, and accounted for it. Realize that it’s just an estimate, as I said. I’ll be the first to admit that my pixel-counting isn’t perfect. 😉

          • Alon Levy

            First, Musk himself doesn’t believe in a linear cost-weight relationship.

            Second, some of this supposedly urban elevated rail isn’t actually all that urban. It’s cheaper than inner-urban elevated rail, but still not cheap. And the Metro-North grade separations in Connecticut are mostly not urban, but suburban.

            EDIT: I forgot: third, it’s not actually a factor of 5. Once you account for the box girder, the HSR pylon is simpler because it’s just one concrete pile. The Hyperloop pylon widens substantially at the top, to say nothing of the HSR pylon’s greater height because of the inability to hug the terrain as well as HSR. (Of course cost grows far more slowly than linearly in height, but this is just extra evidence the weight of the tube isn’t a major factor.)

          • Phil

            Alon Levy: You keep saying that Hyperloop can’t hug the ground, but have you looked at the route? The high speed part isn’t hilly, and the hilly part isn’t high-speed (300 mph vs. 760 mph). The Hyperloop alpha document has a breakdown of pylon heights, and ~90% of them are 20 ft high.

            You’re assuming that the 0.67 m/s^2 track construction limit is due to motion sickness, but the track construction standards PDF you linked to mentions derailment and wind loads. Constraining the Hyperloop design because of rail implementation details—again—seems to be begging the question.

            Great discussion, btw, and thank you for engaging in this way. Just so you know where I stand, I think Musk’s estimate is on the low side, but more like 2-3x too low rather than 10x.

          • Alon Levy

            The document says nothing about vertical curve radii, so it’s quite possibly an underestimate of pylon height. The I-5 corridor is mostly flat, but it gets a bit hilly from Kings County north. The grades are easy enough to accommodate, but the transitions may not be.

            In Lindahl’s thesis the reason for vertical curve radius isn’t given; the part about wind loads is a separate part of the thesis, investigating the possibility of tilting at very high speed. The safety issue for vertical curve radius is that a change in the train’s weight will change how it rides on the rails; on a conventional train failure generally leads to derailment, but the same issue could equally happen in a tube, with the train swaying into a tube as the air pressure doesn’t perfectly balance the weight anymore. This should be investigated with a simulation and tested rather than handwaved.

          • Phil

            Of course the alpha document doesn’t mention vertical acceletation — it’s pretty obviously assumed at 0.5g. As far as motion sickness goes, remember also that the passengers are reclined, so vertical acceleration is substantially experienced as *longitudinal* acceleration. The big nausea problem is “heave” (vertical *oscillation*), as detailed here: http://www.ilo.org/safework_bookshelf/english?content&nd=857170582

            Lindhal’s thesis mentions the reason on PDF-page 18. Quoting:

            “A vertical curve provides a smooth transition between successive tangent gradients in the railway profile. In changes of gradients a suitable radius must be used. If the vertical acceleration on a crest is too great, the loads on the vehicle wheels can cause the wheels to climb the rail and thus cause a derailment. Furthermore, the resistance against vehicle overturning at side-winds will be lower It is also important that passenger comfort is being ensured.”

            I completely agree that dynamic stability needs more analysis in general. It just seems odd to insist that the Hyperloop must be constrained by rail’s limitations, and to apply that limitation so inconsistently. You say the pylons must be taller due to vertical acceleration, but since the capsules bank, *all curves* are vertical from the capsule’s perspective. So either the overall curve radius (horizontal and vertical) is unworkable, or neither is.

            Upon further reflection, it’s a bit disingenuous to jump straight to “taller pylons” (the expensive part) when tweaking the speed with a deceleration section, or even a longer coast section, would almost certainly be cheaper. Obviously if this actually got built you would optimize those parameters to achieve the lowest total cost. Be careful not to reverse that optimization just because it advances an argument.

          • Alon Levy

            Wait, what? I’m attacking any attempt to make passengers feel 5 m/s^2 acceleration, in any direction. Try 1 m/s^2.

            But in fact, with such standards, horizontal and vertical curves are not the same. Perfect banking allows raising lateral acceleration to more than 4 m/s^2 while the passengers would only feel 1 m/s^2 additional force. It can do no such thing for vertical curves, and as a result vertical curves have to be much wider. So vertical curves of radius 170 km are required if the additional force is 0.67 m/s^2, or 114 if it’s 1 m/s^2. The issue here is that passenger-felt acceleration is the difference between the combined gravity and acceleration vector and the expected 1-g-downward vector; an acceleration vector parallel to the weight vector can’t be canceled away, whereas an acceleration vector orthogonal to it partially can, especially if it is much smaller in magnitude.

            Your link doesn’t work. At any rate, with tilting trains, the problem isn’t just oscillation, but also the suddenness of the changes and the lack of relationship between them and the observed horizon. Tilting trains nowadays compensate at most 80% of the cant deficiency, not 100% of it, because just seeing the horizon move without feeling anything is enough to induce motion sickness.

            Re taller pylons, they’d appear in the middle of the route, not just at its ends. If the Hyperloop has to lose a significant portion of its speed in the middle just to have shorter pylons, then together with realistic, barf-free acceleration rates (could be more than 1 m/s^2: 1.3 is standard on high-performance trains, and judging by acceleration graphs, JR-Maglev has initial acceleration of about 2), this kills the entire speed advantage of the system over flying. And without the ability to use legacy rail routes into Downtown LA and SF, it also has no advantage over HSR anymore.

            And all this of course hinges on assuming a strong weight-cost relationship, stronger than assumed in the document itself for its two alternatives. Since \log_{1.6}1.24 \approx 0.46, we get an exponent of 0.46. So if you pretend the box girder is part of the weight to be supported but the Y-shaped upper part of the Hyperloop pylon isn’t, it’s still a factor-of-5 difference in weight, which translates to a factor-of-2.1 difference in cost. That’s five to seven times more expensive than Musk claims. “It’s just an alpha” doesn’t justify this; heads have rolled about factor-of-2 cost overruns.

          • Phil

            Alon Levy:

            >I’m attacking any attempt to make passengers feel 5 m/s^2 acceleration, in any direction.

            You better get down to your local airport and stop those planes taking off then. 😉 And yes, I understand force vectors.

            >Your link doesn’t work.

            Works for me. Try the internet archive: http://web.archive.org/web/20110501175337/http://www.ilo.org/safework_bookshelf/english?content&nd=857170582

            I think it’s obvious that horizon mismatch isn’t a problem for the hyperloop.

            >this kills the entire speed advantage of the system over flying.

            Do you have numbers here, or are you just guessing? Remember to assume best-value-proposition optimization here.

            >weight-cost relationship

            You’re overstretching. Without knowing the mass of the two different kinds of hyperloop pylons themselves your analysis is at best woefully incomplete. Rather than mathematical hand-waving, how about digging up the cost breakdown of that $50m/mi? If the pylon portion of that cost is small (say, $10m/mi) then this argument against the Hyperloop evaporates.

          • Alon Levy

            The argument about weight-cost is that the tube is light, not that the pylons are light.

            The horizon mismatch is very much a problem for Hyperloop – people won’t be able to see out at all, and acceleration up and down has no visual cues. From your link,

            The essential characteristics of stimuli that induce motion sickness is that they generate discordant information from the sensory systems that provide the brain with information about the spatial orientation and motion of the body. The principal feature of this discord is a mismatch between the signals provided, principally, by the eyes and inner ear, and those that the central nervous system “expects” to receive and to be correlated.

            Several categories of mismatch can be identified. Most important is the mismatch of signals from the vestibular apparatus (labyrinth) of the inner ear, in which the semicircular canals (the specialized receptors of angular accelerations) and the otolith organs (the specialized receptors of translational accelerations) do not provide concordant information. For example, when a head movement is made in a car or aircraft which is turning, both the semicircular canals and the otoliths are stimulated in an atypical manner and provide erroneous and incompatible information, information that differs substantially from that generated by the same head movement in a stable, 1-G gravity environment. Likewise, low-frequency (below 0.5 Hz) linear accelerations, such as occur aboard ship in rough seas or in an aircraft during flight through turbulent air, also generate conflicting vestibular signals and, hence, are a potent cause of motion sickness.

            The mismatch of visual and vestibular information can also be an important contributory factor. The occupant of a moving vehicle who cannot see out is more likely to suffer from motion sickness than one who has a good external visual reference [emphasis added]. The passenger below deck or in an aircraft cabin senses motion of the vehicle by vestibular cues, but he or she receives visual information only of his or her relative movement within the vehicle. The absence of an “expected” and concordant signal in a particular sensory modality is also considered to be the essential feature of visually induced motion sickness, because the visual motion cues are not accompanied by the vestibular signals that the individual “expects” to occur when subjected to the motion indicated by the visual display.

            As for your comment about planes, planes taking off generate less acceleration than 5 m/s^2, and even that acceleration is instantaneous and is a short portion of the trip. On Hyperloop passengers are expected to be hit with this acceleration periodically, at every curve, every change in speed zone, and (probably, it’s not mentioned) every vertical curve.

        • cosmicbuzz

          ” on a conventional train failure generally leads to derailment, but the same issue could equally happen in a tube”
          Alon, you already knew about my idea of having an oscillating container within the pod shell to maintain passenger comfort. There is no derailment for tube because the pylon could be a triangle that have enough supporting margins. Also, the air ski at both side can be adjusted when the weight sways. The document is not perfect, but surely is improved every moment by the open source community, like now.

          • Alon Levy

            Can you explain how oscillation can dampen g-forces? Not merely modify their direction, but change their magnitude?

          • Joey

            What is this “oscillation” you keep talking about. Do you mean tilting or canting into the curve? This is done on railways, it’s even done on roads. And it’s fully accounted for in all of Alon’s calculations. “Oscillation” implies something completely different.

            And what does a triangle have to do with anything? The pod is not touching the tube at any point – it is suspended, so support points mean nothing. But the risk of crashing into the tube wall is still there. Any number of events could cause a sudden change in the tube’s alignment – an earthquake, for instance, or a drunk driver crashing into one of the pillars. Any contact between the vehicle and the tube wall is likely to be fatal at such a speed, so just saying “it’s going to blow out a bunch of air to keep itself stable,” is not sufficient.

            The document is not perfect, but surely is improved every moment by the open source community, like now.

            That doesn’t change the fact the the document has serious handwaves and outright factual errors. If Musk had said “this is an interesting concept that might be possible at some point in the future, let’s start developing it” that would have been reasonable. But instead he said “this is buildable in a few years and we don’t need HSR,” when in reality the technology is decades out (and that’s assuming it’s developed aggressively). It will become feasible eventually, though I’m betting that magnetic levitation will be used rather than pneumatic levitation, and this has already been played out to an extent in the real world.

            The reason I’m so intent on debunking this is because it carries a real risk to the actual HSR project. The funding situation is already shaky, and the fact that people believe Musk makes it even worse. This proposal has achieved a dangerous level of publicity, and there’s a real risk that we get nothing built because of it. Musk should have known better than to frame it in the way he did.

          • cosmicbuzz

            I did not claim oscillation dampen g-force, it ensure the g force is downward for passenger reclining on his back (45 degree?). Knee should be higher than normal to reduce blood flowing to feet. So blood flow to the head is roughly same as standing up. It is the triangular shape of pylon that holds up the g force extra weight.

          • cosmicbuzz

            More illustration:
            * Passenger A recline on chair attached to oscillating container B.
            * Oscillating container B oscillate within pod shell C. Of course this modifies the document.
            * C’s position does not change at cross section view. C both side has air ski, if one side sustain more force, air flow gain stronger to balance it.
            * C flow inside tube D.
            * Tube D is supported by triangular shape pylon E at bend points. This enhance the document.
            * When pod approach an E pylon with its weight and g force, one side of the triangular pylon exert more support.

          • cosmicbuzz

            Let me talk about debunking to save HSR.

            At $100B construction cost and operation cost over 50 years, and $100 per ride, it will have to be 20 million ridership per year, ~50k per day. I can drive my car taking 4 people with ~$100 gas, much cheaper than $400. Reducing fee will need to be compensated by more ridership. I got some figure that European ridership is 7 million per year. Voters will vote it down at those cost.

            If proven much cheaper and faster, hyperloop could work economically. I will opt for 1 hour end-to-end hyperloop ride than driving or taking expensive+slow HSR.

          • Alon Levy

            “European ridership”? There is more than 1 HSR line in Europe. Some of them have 2 million riders a year, some have 30 million. It depends on whether they connect Paris with Lyon or Madrid with a random resort town. If you scale the ridership of the domestic lines to the population of the cities they serve, the California HSR ridership estimates check out. Los Angeles is a huge city, and San Francisco is also quite large.

          • Joey

            Except that it has not been demonstrated to be cheaper or even feasible within the next 30 years. And if the stops are at the edges of urban areas rather than city centers, then access time is going to play a significant role. This is precisely why HSR is competitive with flying – even though you spend more time on the vehicle, it gets you closer to your destination (origin is somewhat less important) and you spend less time in the station than at the airport.

        • Falstaff

          “The important thing is how it compares to the mass of the concrete trackway, not the train.”

          Yes, like to like, and HSR rolling stock is heavier than Hyperloop’s.
          o Hyperloop capsule, no car, full: 15t (pg 22), ~14m @ 2 passengers per m., or 1 t/m.
          o TGV full: ~2 t/m.

          • Falstaff

            “…weight of the structure dominates either way.”
            The static mass of the structure is clearly greater; it is not clear that structure mass “dominates” the various forces, given the capsule/HSR carriage is a live load.

  8. Brian Dang

    I like all mass transit system, as oppose to single person commute in a car. But in this case, Hyperloop is better than bullet train.
    1) Train rail completely divides the land to two inaccessible parts, as a barrier for both human and animals. Hyperloop pillars do not.
    2) Hyperloop tube is cheaper to build than train rail way: capsules are lighter than train, hence the tubes can be prefabricated, assembled, and cost less to structural support, while the rail requires major land/structure engineering to support the massive train mass. The author unfairly compare the tube/pillar as costly as elevated highway. A highway is a massive structure hundreds of feet wide while the tube is less than 10 feet and light weight, easily supported by pillars.
    3) Hyperloop is more energy efficient than train: In ambient air pressure, much of the energy is wasted in overcome the air resistance by the train aerodynamic drag. In partial vacuum, capsules needs less energy to travel. The roof top solar panel is a major plus here.
    4) 3 hrs on the train vs 30 minutes riding roller coaster? I will take the roller coaster (it’s not as bad as roller coaster really).

    • Alon Levy

      You are wrong.

      1. Viaducts allow roads to pass through. At-grade infrastructure doesn’t. The extra cost of viaducts is invariably higher than the cost of building at-grade with a few grade separations and buying out the farmers.

      2. Rail elements can be prefabricated. Vacuum tubes, maybe, but there isn’t a preexisting industry for it. The tube itself is quite heavy, as heavy as a train of equivalent length. A two-track railroad, contra the “100′ wide” part in the Hyperloop proposal, is about 8-9 meters wide: check aerial photos of the Shinkansen viaducts. They use wider ROWs in locations with cheap land, like rural France, where they might want to also put power lines next to it.

      3. It is not that energy-efficient to accelerate to 1,220 km/h. Acceleration is an energy hog. Look at actual HSR energy consumption, not at the false numbers presented in the Hyperloop proposal.

      4. 30 minutes roller coaster, plus an hour station access because the LA station is in Sylmar, plus an hour security and check-in. That’s the kind of transportation HSR is designed to avoid. It’s a marginal improvement over flying, which is the same only the in-vehicle time is an hour and there’s way less motion sickness.

      • Brian Dang

        1) what is your point? I was trying to say high speed train track is very bad as of the “Berlin Wall” for both human and animals.
        2) Tube might be heavy, but it is going moving at high speed as a moving train. Supporting a fast heavy moving train isn’t the same as supporting a non-moving tube.
        3) accelerate an object in low air pressure used less energy than in ambient pressure, period. For the Hyperloop, most of this energy would be recovered as in Hybrid or Electric cars.
        4) the LA station is in Sylmar issue — I think it could located any where that makes sense. It’s not a technical issue.

        • Alon Levy

          1. My point is that at-grade is cheaper and lower-impact than elevated, contra Musk’s FUD. It’s harder to cross, but in France SNCF organizes land swap deals that minimize farmers’ need to cross the tracks. When there are good freeway ROWs, HSR lines can follow them (alongside, never in their medians) to reduce impact. Ultimately, occasional rural grade separations, including crossings for migrating animals and mitigations for people who need to cross, are much cheaper than viaducts. The cost blowouts for California HSR actually came from magically discovering that more viaducts and more tunnels were needed than thought.

          2. The dynamic loads grow with speed, but not all that much. An 80 km/h urban rail viaduct and a 350 km/h HSR viaduct will cost approximately the same.

          3. Regenerative braking recovers ~20% of electricity, not “most.” The same technology exists on conventional trains nowadays, and still operators try to limit the aggressiveness of acceleration and deceleration cycles.

          4. It is a technical issue; it’s much easier for trains to get to Sylmar than for passengers, because urban infrastructure for Sylmar-LA is expensive. HSR can piggyback on the Metrolink line once FRA regulations are changed – all it takes is electrification, which is cheap. A system that’s not compatible with conventional rail can’t. Passengers are exceptionally sensitive to egress time (though not access time), and any additional minute they have to spend between the LA-end station and their final destination costs a meaningful amount of revenue; the same is true to a lesser extent of the SF-end station. This ability to run on conventional tracks is precious. Otherwise, Transrapid and JR-Maglev are both better than conventional HSR on every single measure except for their vendor lock, and unlike Hyperloop actually have a track record of technical success and accurately-estimable construction costs.

          The Shinkansen, which runs on a separate gauge from the Japanese legacy network, took a long while to get to Tokyo from the north because of the same incompatibility, and in the years it terminated outside Central Tokyo the Tohoku Shinkansen was economically marginal, and regarded as a political vanity project. It only became more successful once it got to where the people wanted to go. And for most of those bad years, its southern terminus was Ueno, which is 4 kilometers north of Tokyo Station and is connected to Central Tokyo by more high-frequency rapid transit lines than Sylmar will ever have.

          • nickikt

            Maybe its me beeing not american. Why do you need security checks for hyperloop? Do you guys have security checks for every single train or metro in the country?

            That seams idiotic to have airport securty at a train or hyperloop station.

            I can see your argument about going to the station takes some time but at least in my case going to the airport with existing system car/metro is a small part of the wait, standing in line for securty, staning in line to get into gate, stading in line to get into airplane, wait for airplane to actually fly is much worse. These would all fall away, and be reduced to wait untily you can get into a coupsle.

          • Will Brown

            You are just plain jealous that Musk came in and got all the attention. You complain about Musk not doing cost projections properly, when in fact the HSR, with *ALL* the resources it had in preparing the proposal, went from $45B (ballot) to $98B(reality) to $68B(fudged, to make it palatable to voters) over the span of a couple of years.
            But your responses above are funny, to say the least.
            1. “SNCF does this in France”… “… happens in Spain”… last I checked, we weren’t living in Europe. Secondly: SNCF proposed a totally private HSR, but was ignored by CHSR.
            2. Sounds like “because I said so”.
            3. Accelarating something that’s in a (basically) frictionless environment (no air, suspended above the flat surface) takes _much_ less energy than a train on wheels.
            4. “All it takes is electrification, which is cheap”. Tell that to the CalTrain people, who’ve been talking about electrifying the SF-SJ section for decades.

            Your entire gripe is with the fact that Musk is famous and you are not. Well, you got your wish: you are also “famous” now, but for the wrong reasons.

            There are 2 types of people in this world: those that build, and those that sit on the sidelines and criticize. We both know which group you are in.

          • dhogaza

            “Maybe its me beeing not american. Why do you need security checks for hyperloop? Do you guys have security checks for every single train or metro in the country?”

            Spain does for every AVE (their HSR) train. It’s minimal compared to airport security, though, just a bag scan, you can keep your shoes on …

          • Nathanael

            I see the Elon-worshipping fantasists are out in full force.

            This has been checked over by people from multiple disciplines, and all of them have pointed out serious defects. The “Hyperloop” (a) does not work (there’s a heat dissipation problem), and (b) would cost just as much to build as CAHSR (because all the cost is in the civil engineering, and Musk hasn’t found any way to make that cheaper). Those are just the two most serious defects in this napkin design.

        • danR

          Most of the kinetic energy at catastrophic failure will be recovered by the ground as a huge mass of jammed train+tube rips away from the preceding length. The chain-reaction I’ve outlined above would make for a good disaster flick, but a horrible ride.

          Nobody should ever consider building any vacuum or near-vacuum train-like vehicle in an open-air tube, Musk’s or anyone else’.

  9. beowulf

    “and people who question him and laugh at his outlandish ideas will invariably fail and end up working for him”
    Your analysis of how to upgrade Amtrak on the cheap was so stellar, Musk may yet offer you a job.

    “There is a crossing of the San Francisco Bay, but there’s no mention of the high cost of bridging over or tunneling under the Bay – we’re supposed to take it on faith the unit cost is the same as along the I-5 corridor in the Central Valley.”
    Tunneling the Bay will never happen. BART already runs to Oakland, it’d be crazy not to start from there like Amtrak does now. The interesting thing is that Musk might have just (metaphorically) blown up every high speed rail project in the country. Congressmen and voters are going to be start asking why they should pay for something that’s more expensive and much slower than the Hyperloop. It’ll be the only game in town, you’d almost have to go work for him then.

    • dhogaza

      “The interesting thing is that Musk might have just (metaphorically) blown up every high speed rail project in the country. Congressmen and voters are going to be start asking why they should pay for something that’s more expensive and much slower than the Hyperloop.”

      Of course, one can answer “why can’t one ride the hyperloop to see how it works in person, while one can choose from hundreds of HSR routes to ride in Europe?”

      BTW, I can build a hypersonic airplane that can do LA to Japan in an hour flat, for a mere $2 billion dollars. Quit spending money on on 787s NOW!

    • foljs

      You mean: “I hate Musk, and am sick of hearing of this thing, and wanted someone to affirm my biases”.

      • doublewilf

        I’d never even heard of Musk. I read about the proposal, and thought it insane/silly.

      • Ben Phelps

        I don’t hate him. He’s made me some good money on my Tesla stock. But this idea doesn’t solve a single one of the things that makes infrastructure problems so expensive or hard to build. And yet it was reported it like he’d just cured cancer.

  10. Jeff L

    Excellent writeup.

    I’m trying to understand the costs of tunneling under the SF Bay. There is an interesting 2002 study that addresses a new BART tunnel at a cost of about 14X what Musk seems to imply. I can’t believe the somewhat narrower diameter of the Musk tube would save that much. Any thoughts on the function of tunnel diameter (or area) to cost of tunneling? Also, I assume the Musk tubes also need galleries, drainage and space for maintenance/operations equipment.

    Check on the PDF on the line saying “Cost Report 6-20-02” right here:


    The BART detail section starts at the bottom of page 12 on the PDF

    • Alon Levy

      I have heard (on other blog comments) is that cost is proportional to tunnel diameter, since the lining is proportional to diameter rather than to cross-sectional area. I’ve also heard otherwise, i.e. that cost is proportional to tunnel cross-sectional area. However, that is just the TBM part, which is the easiest part of any such project. A station cavern in San Francisco would be a nightmare (and in fact is, with the $4 billion Transbay Terminal project) regardless of tunnel diameter.

      That said, the MeFi people have done some digging and the proposed mountain tunneling cost is outlandishly low compared to water tunnels as well.

      • Jeff L


        BTW, there are some examples of other tunnel actual costs around the world in that doc I mentioned.

  11. Richard

    Sylmar is 24 miles from Union Station in LA. How does this increase travel time to 2:40 from below thirty minutes?

    • Alon Levy

      First, it starts at 35 minutes, not below 30. Second, the proposal explicitly assumes airline-style security theater (most HSR systems in the world have no security theater, and the few that do have a minimal procedure that takes 10 minutes), so add an hour. Third, traffic in the LA area can add an hour at rush hour, and it’s not as if there’s any public transit at Sylmar to speak of.

      All this assumes the SF station is in SF and not somewhere in the East Bay.

      • nickikt

        Why would you need securty? Ok its in the proposal but why would you need it?

        I dont know the technology but if you can kill many people by blowing the tube up, its just as easy to get in a truck drive to a pillar and shot it with a rocket luncher.

        • Alon Levy

          The idea is that a bomb is catastrophic: decompression is not survivable since the air pressure is so low (much lower than at airline cruise altitude), and neither is a collision between the capsule and the tube since the speed is so high. This is not the case on HSR, where high-speed derailments are zero-fatality if the system has appropriate safeguards, and bombs are ineffective at killing more than a handful of people.

          But you’re right that you can just as effectively throw a bomb at the steel tube.

          • ajay

            “This is not the case on HSR, where high-speed derailments are zero-fatality if the system has appropriate safeguards, and bombs are ineffective at killing more than a handful of people.”

            This doesn’t quite ring true. However good the safeguards, I am sceptical that if you have a train going at more than 150 mph, and it leaves the tracks, you can be sure that no one on that train is going to die. A train going at 120 mph came off the rails in Spain last month and 79 people were killed. (Yes, I know that he shouldn’t have been going that fast. That’s not the point. The point is not “can we put rules in place that should stop trains derailing at 120 mph” but “what happens when they do”.)

            I’m also sceptical that a bomb on a train – of whatever type – will kill no more than “a handful” of people. Again, experience indicates differently. Madrid and Mumbai saw an average of 20-30 people killed by each explosion. That’s quite a lot.

          • Alon Levy

            Bombs on HSR kill very few people. Bombs on crowded commuter trains kill more. The Spanish derailment involved extreme lateral acceleration, whereas high-speed derailments have happened on the TGV without fatalities, as the train stayed upright and did not leave the track area.

          • BruceMcF

            ajay, bear in mind that the HSR corridor by design does not have such tight curves in it. Also, if the approach to the curve had been fitted with three digital transponders as opposed to the analog transponder it was equipped with, emergency brakes would have been applied in time for the derailment to have happened at a much lower speed or prevented entirely. And that is not even the primary PTC system itself, but rather its back-up.

          • Falstaff

            “The idea is that a bomb is catastrophic: decompression is not survivable since the air pressure is so low ”

            That seems a little dogmatic.
            1) Even the vacuum of space does not kill immediately, the human body has 10-30 seconds before the various catastrophic effects take hold.[1] But unlike even a jetliner at altitude, a ruptured capsule is unlikely to be exposed to the tube pressure for any length of time.
            2) Any explosion that ruptures the tube also rapidly raises the pressure.
            3) The hyperloop proposal calls Oxygen masks deployed as on aircraft.
            4) The remedy given in the proposal for “a large scale capsule depressurization,” is that “other capsules in the tube would automatically begin emergency braking whilst the Hyperloop tube would undergo rapid re-pressurization along its entire length.”


            “This is not the case on HSR, where high-speed derailments are zero-fatality if the system has appropriate safeguards, and bombs are ineffective at killing more than a handful of people.”

            And this information is gleaned from explosive tests of HSR rolling stock? Certainly the London 7/7 attacks, show where the bomb detonated in one carriage does heavy damage to an adjacent carriage.

  12. Les Roark

    I started out pretty interested in this blog, but as it became obvious that a fraud was calling, “fraud”, I began to reread the claims. I have to wonder at YOUR motives and tend to believe that in your assertation that you have no interest in burying Musk, you’re not being truthful. For my part, I have no “idol worshipping” belief in the future success of Musk’s present companies, but do hope they succeed, while betting that you do not. I often read articles on “scientific” research which are nothing more than a search for facts which can be assembled in such a way as to support the previously held viewpoint of the researcher. I feel cheated of the time I have to spend on such articles before discovering the fraud, like this one.
    Musk’s proposal is very rough, obviously, and just as almost all new ideas capable of real world shaking application will need much change and refinement, if it’s workable. I didn’t find in your blog any reason to think that it would fail, I suspect the hyperloop would cost at least three times his estimate, but would also end up being more capable than described. I tend to think that HSR will double in cost and unless America has another economic balloon to make us all feel richer than we are, and it’s built quick, I doubt the HSR will ever be completed as planned, if at all.

    • Alon Levy

      Musk’s proposal understates the cost of viaducts by a factor of ten. That’s not “rough”; that kills the entire supposed cost advantage over HSR.

      But what do I know, I’m a fraud. Probably every source I’ve linked to is, too.

      • Phil

        >Musk’s proposal understates the cost of viaducts by a factor of ten.

        By “the cost of viaducts” you mean “the cost of the CA HSR viaducts”. You’re begging the question.

        • Joey

          He fails to demonstrate why there would be a factor of 10 cost difference from any other viaduct.

    • Joey

      Okay, how about instead of bashing science in general you point out which of Alon’s cited rebuttals of Musk’s uncited claims you think is wrong, and provide a citation to back it up?

      • Les Roark

        I’m not an engineer nor scientist, but have been reading science and tech articles and some scientific papers for 40+ years. There isn’t any science in this article. Just gathered info being used as a cluib. It’s attacking a general plan/idea which hasn’t been developed to any great extent with studies and facts, stating that they are empirical proof that something’s impossible. As far as I can see, they are good points to attack as problems, not reasons to call musk and his people frauds.
        It may not work. So what?
        It may not work due to issue’s brought up by this author. He sounds as if he’d be a good source of critical feedback.
        But when I discover that facts are being brought forth just to prove something wrong, with questionable motives:
        statements about a gullible public
        making thinly veiled statements about other’s character.
        Pontious Pilate rationalizations of one’s own motives
        I’ve read too many articles like this one in the past where it becomes apparent that the purpose is to attack, not critique, and often enough wrong to place no big importance on because there’s no way to judge without becoming an expert, oneself.
        This article didnt prove the impossibility of anything while stating that it does. I doubt that you’d find a well scientist well respected by peers who would think so.

        • Joey

          The problem is that Musk isn’t saying “this would be cool at some point in the future when the technology is ready,” he is saying “we can build this right now for super cheap,” which is exactly what Alon demonstrates to be impossible. I don’t think he has anything personal against Musk but I think there is good reason to be critical of the fact that Musk even floated this proposal – if people believe the unrealistic cost estimates and construction timetable, then they won’t fund high speed rail and then we get nothing. Musk should know better than to do something like this. And it’s not like this kind of thing hasn’t been proposed before.

          • Tim

            The problem is that Musk isn’t saying “this would be cool at some point in the future
            when the technology is ready,” he is saying “we can build this right now for super cheap,”

            Is that what “alpha plan” means? really?.

          • Joey

            It’s how he’s framed it. He proposed a cost and construction timetable, neither of which are remotely consistent with the idea of an “alpha plan”

          • ant6n

            ”’The problem is that Musk isn’t saying “this would be cool at some point in the future when the technology is ready,” he is saying “we can build this right now for super cheap,” ”’ – hit the nail in the head.

        • Nathanael

          This article conclusively proved that you cannot build Musk’s proposal for significantly less than ten times the cost which Musk claims it will cost, because *Musk got the civil engineering construction prices wrong by a factor of 10*.

          If Musk has discovered some way to make civil engineering cheap, he should have published it.

    • dhogaza

      “Musk’s proposal is very rough, obviously”

      That’s not how he presents it.

  13. Pingback: Elon Musk’s hyperloop
  14. Pingback: Elon Musk’s hyperloop | Symposium Magazine
  15. a Skeptic

    Well written. Musk’s economics also assume no right-of-way costs which is either a massive implicit subsidy or assumes that a public good will be willingly turned over at no cost.

  16. Ross Judson

    I’m a software engineer, so I don’t have the background to properly assess any of this. What I’m wondering is this:

    The pylons hold up the steel tube. The steel tube is more rigid due to its shape, where rails are not. The pylons are 30m apart. Why would the cost of building pylons that can hold a tube be the same as the cost of building a viaduct structure that must create a continuous flat surface to support rails?

    The question for me is, where do we look for cost estimates?

    I googled two terms for images: ‘elevated rail’ and ‘elevated pipeline’. The companies that build long-haul transport pipelines aren’t paying anything close to 50m per mile to construct them. There are obvious differences and a hyperloop is clearly a much more refined structure, but wouldn’t the general techniques from that industry apply here?

    • Alon Levy

      That continuous flat surface to support rail isn’t actually all that massive. Slab can be surprisingly thin. Trains running on the upper level of Barcelona’s large-diameter tunnels are supported on a 40 cm thick slab (see PDF-p. 5 of this paper). It doesn’t matter that much on els – a thicker structure with more concrete and less steel is sometimes more desirable for noise mitigation purposes, and the cost difference isn’t that big.

      Standards for oil pipelines are far lower than for passenger transportation. A Hyperloop system would need more reliability than leak-prone pipelines. Oil doesn’t have a minimum curve radius and is much more tolerant of geometric irregularities. The pylons depicted in the Hyperloop proposal look as massive as the ones on SkyTrain of the JFK AirTrain.

    • Nathanael

      Given that the “tube” is subject to strong lateral forces, the pylons have to be at least as solid as the ones for elevated trains or elevated highways — probably more solid.

  17. Pingback: Symptoms of Stardom | The Cranky Professor
  18. Federico

    would flexing (through wind buffeting, unequal thermal expansion, pylon vibrations etc) of the pipe be a problem?

  19. Pingback: The difference between thinking big and thinking too big :: Second Ave. Sagas
    • Jim

      All we need to do is invent transparent aluminum and we can have all the windows we want…..

  20. Rational Plan

    Thanks for this it will save me time to just link to this article in the future. Ever since the hype cycle started all I’ve seen is endless fanboys going ‘wow what a genius’ and ‘he started project x he knows what he talking about’. I’ve tried pointing out it just vapourware but to no avail. I should just nickname name Lyle Landley and post the Simpson clip of the Monorail song.

  21. Pingback: The barf ride t… | Straßgefühl
  22. Pingback: “Hyperloop”: Not Quite Shovel-Ready | Streetsblog.net
  23. Digital Cosmology (@DCosmology)

    This is an excellent analysis of a very old idea that was abandoned due to the problems exposed and analyzed in detail.

    I asked my nephew who is in college to calculate accelerations for given distances and speeds just to compare to the numbers in this article but he told me he did not have an app in his ipad yet for doing that. I hope the message is clear.

  24. Daniel Einspanjer

    In your article, you mention that several assumptions in the Hyperloop proposal regarding the cost, energy consumption, and limitations of the HSR are wildly inaccurate, and you cite several comparisons to various other HSR installations in the world.

    I’ve read in the past that rail in North America does not compare favorably to rail in other parts of the world, HSR or otherwise due to regulations that some call antiquated regarding the weight, speed, and structure of all trains running on North American rail. Are these comparisons generally accepted, or do you feel they are misleading? Will the HSR that is proposed for California actually be equivalent to HSR installations elsewhere in terms of speed, energy efficiency, and structure, or will it be a much heavier, expensive, and less efficient version that seems to be standard for rail vehicles in North America?

    • Alon Levy

      Those comparisons are perfectly correct. I’ve written some posts and many comments on other blogs attacking proposals for unreformed conventional rail in the US on those grounds.

      However, California HSR is planned to be different. The technical standards are cribbed from European and Japanese HSR systems, and the FRA appears to be fine with the trains’ running unmodified or barely modified European equipment.

      I’m skeptical that California HSR will be as good as elsewhere on matters of integration with other rail systems and such, and the system is quite expensive, but the cost comparisons I’m doing in this post are specifically to California HSR costs, not Spanish HSR costs.

  25. Yan

    Looks like someone stole your thunder because he is able to break through walls you can’t make a dent in, and you are mad about it… possibly rightly so, because in this society some are more equal than others despite the aired professions to the contrary. In other words, you just had the public say to you, by the voice of a silent comparison, that you are just a piece of shit. Because Musk is treated on a whole different level, the level of someone that puts his money where his mouth is.

    Meanwhile I think you are a little too mad. HSR is also engineering madness, in the sense of putting a stupid stage-coach on a track an running it faster and faster. And faster. Just throw something on the track, like an animal, to see what I mean. Musk is right on about the advantages of a tube. If his solution costs the same, it still is preferable, because it doesn’t scar the landscape.

    I’d take a fast somewhat bumpy ride any day, did you ever take a bus in the “rush” hour to get an idea of how maddening and sickening that is??

    BTW, the way the pods are sketched, the diameter of the tube could be 1.5m tops. Everyone I know mostly travels alone, so tube diameter could be even less, say 1m. Just teleport me.

    • Chris W

      “Because Musk is treated on a whole different level, the level of someone that puts his money where his mouth is.”

      You do realize that Musk is explicitly NOT putting his money where his mouth is here, right?

    • Joey

      Looks like someone stole your thunder because he is able to break through walls you can’t make a dent in, and you are mad about it…

      Which wall has he broken through? None of Musk’s claims have any real technical backing.

      If his solution costs the same, it still is preferable, because it doesn’t scar the landscape.

      It won’t, and it has the exact same footprint as HSR. Rails can exist on a viaduct or at-grade. Tubes can exist on a viaduct or at-grade. Either way, must of the weight is the structure, not the vehicles.

      I’d take a fast somewhat bumpy ride any day

      If it’s bumpy you’re going to crash into the tube walls. The alignment tolerance for regular high speed rail is already tiny (a few mm for the rails), and at higher speeds it’s even smaller. That kind of precision can be achieved with magnetic levitation, but can it with air suspension? What happens in the even of an earthquake, which could shift the tube horizontally by a significant amount, or a sudden loss of power which would cause the air suspension to fail?

      BTW, the way the pods are sketched, the diameter of the tube could be 1.5m tops. Everyone I know mostly travels alone, so tube diameter could be even less, say 1m. Just teleport me.

      Please read Alon’s section about capacity. Musk’s proposal already has capacity problems, even with an unrealistic distance between pods, and if you reduce that even more then it’s going to be completely ineffective at getting any significant number of people between SF and LA.

  26. M Robert Carr

    Congratulations on a post and comments on something more thoughtful (notwithstanding some colorful language) on the topic than is usually seen on the Internet.

    We owe a lot to dreamers. But perhaps we owe a lot more to healthy, thoughtful skepticism, yes, to include motives and support.

    Elevated guideways have long been known to cost more than twice at grade level guideways. Without redundant elevated guideways security, safety and operations problems tend to rise exponentially beyond the times two amount. In other words real-world operability would require not a single guideway, but multiple guideways. Ask the people at Disney what happens when the monorail breaks down. As one Disney person told me*, their monorail was more amusement ride than serious transportation. Maybe that is an overstatement. But the truth is that operational costs are usually greatly discounted as part of the equation

    History has no shortage of TechoSpeed Dreamers with some intriguing ideas and lots of promotionally-biased, cost-benefit analysis to tease out scarce, public funding for first-in risk taking.

    To point this out often gets slammed as horse and buggy thinking. Well, it wasn’t horse and buggy thinking that stopped the Super Sonic Transport (SST) boondoggle and others. It was hard, common sense analysis of whether the technology was appropriate. Let’s not confuse “we can do it” with “let’s do it.” Ask the British and French how their SST bet paid off.

    *(My qualifications: former member of the US House of Representatives Transportation Appropriations Subcommittee & Chairman, 1993-1994, adjunct professor, George Washington University and someone who understands the appeal of leapfrogging technology, but who’d really like Amtrak to get to 150 mph.)

  27. Stephen Corwin

    1) The guy never came out and said, “Here’s my foolproof, ready-to-execute plan for how to replace the rail project.” Stop acting like he did. Obviously any new technology is going to require extensive research.

    2) Regardless of whether or not this is currently feasible, can you not respect that this is the type of technology that we should be researching? Or would you prefer that we continue building maxed-out versions of outdated technologies for perpetuity?

    3) Most importantly, the hyperloop announcement, at the very minimum, has gotten the entire community excited and talking about alternatives. Elon has opened our minds to the idea that current technologies do not have to be the end all be all of existence, and he’s kickstarted a pathway to a brighter future. How could you possibly misconstrue that to be a bad thing?

    America stopped innovating in our cities at some point in the 20th century. This needs to change. But it’s pessimistic people like you, people who would rather shoot down ideas for their faults rather then praising them for their potential, that are hindering our progress as a country. How about instead of writing giant articles trying to squash innovation, you use your clearly reasonably intelligent mind to try and solve the problems you’re finding with the project and bringing it closer to feasibility?

    Or are you one of those people that derives so much satisfaction from playing devil’s advocate that you simply can’t ever let anyone be excited about anything?

    Get it together man. Support innovation in all forms. And make your criticisms constructive, not cynical.

    • Alon Levy

      He constantly denigrated California HSR, using the fraudulent claim that he has an alternative that costs a tenth as much. He doesn’t. He doesn’t even have a proof of concept; he has cost numbers he pulled from his ass, capacity figures that are both insufficient and pulled from his ass, and wrong figures and FUD to bash conventional rail. He might as well have said, “Assume we’ve proven P = NP.”

      As for constructive criticism, there’s plenty in the post, starting with the idea that innovation has to be about speed and technology. With mature technologies, this is almost never the case. Might as well try to reinvent the jet engine, or food, or housing. There are some amazing innovations in all three, both technological (e.g. ways to boost agricultural productivity) and social and political (e.g. political systems that prevent famine from happening). Transportation is similar, and there are some amazing things done in terms of tunneling technology, train aerodynamics, signaling, and ride comfort, as well as sociopolitical and managerial improvements regarding lowering construction costs, building passenger-friendlier schedules, and increasing cooperation between complementary transit modes.

      However, none of this innovation is a reinvention. It doesn’t need to be, because mechanized transportation is a 183-year-old technology. The actual obstacles to having this innovation happen in the US are that there’s no internal market for it nor any foreign buyer crazy enough to buy rail technology from a US startup, and that US business culture is heavily focused on reinvention and thinks that mature technology is too boring. In reality, backward-compatibility is precious – that’s how HSR can serve Downtown LA and SF with just Sylmar-to-San Jose HSR infrastructure whereas Hyperloop awkwardly terminates at Sylmar.

    • JJJJ

      1) The guy never came out and said, “Here’s my foolproof, ready-to-execute plan for how to replace the rail project.” Stop acting like he did. Obviously any new technology is going to require extensive research.

      Actually he did. hes saying this can be done in less than 10 years, and we should build it instead of HSR.

      This guy made a pre-anouncement announcement, hyped the big reveal, and then had a press conference about it.

      Someone whos interested in getting the community excited and pushing innovation and research submits an article to a Science magazine. This guy didn’t; it was a grenade-launching attack at HSR. Thats the big problem here.

      “Build mine because its better!”

      And then we cancel HSR, try to build his, realize it cant be done, and are left with nothing.

    • Ben Phelps

      If you want this thing to get built, somebody has to point out all the problems. Then somebody has to come back and solve them or point out why the second person was wrong in their criticisms. I’m waiting for a single commentator to do so here. “You just don’t like him,” while it very well could be true, is not a refutation of the arguments presented here.

    • kevin

      Haha you are completely full of bullshit. “Get it together man. Support innovation in all forms. And make your criticisms constructive, not cynical.” Way to completely ignore the entirety of this article, you worthless nay-saying tool! haha seriously who even says “Or are you one of those people that derives so much satisfaction from playing devil’s advocate that you simply can’t ever let anyone be excited about anything?” in response to PAGES AND PAGES OF MATH AND TECHNICAL COMPLAINTS ABOUT INFEASIBILITY.

      Seriously, you are terrible and this is the worst comment possible. HOW DARE YOU NOT SUPPORT INDEPENDENT RESEARCH WITH YOUR EVIL AND POINTLESSLY HARSH PEER REVIEW.

      • kevin

        hahahaha I’m still laughing! You absolutely proved this authors point about mainstream dullards thinking that “Getting excited” about something is the only important part about SCIENCE.

    • dhogaza

      Stephen Corwin:

      “Regardless of whether or not this is currently feasible, can you not respect that this is the type of technology that we should be researching?”

      I don’t think anyone’s claiming this shouldn’t be *researched*.

      Musk’s proposal isn’t a *research* proposal. It’s a proposal to replace the CA HSR project with with a transportation system that has not been researched. Must less engineered, prototyped, tested etc.

      I’d love to see the concept researched, and if research suggests it might pan out, to see that followed by prototype tubeways being engineered and built, along with the necessary pods, communications and control systems, etc.

      Such research and testing must include testing to failure, such as is done with other modern transportation systems, from the car you drive (subjected to an extensive series of crash tests during development), airliners (tested to destruction on static testbeds before they ever fly), etc.

      The research and engineering programs that led to HSR and maglev trains serve as a reasonable template as to what kind of timeframe and cost would be necessary to turn Musk’s dream into a robust, reliable, well-engineered transportation system.

      Though of course such a research and engineering program might just as easily tell us that such a system is not an economically sound alternative to HSR.

  28. formid0

    Your detailed knowledge of mass transit is to your credit. With something so difficult and complex as what Musk proposes, it’s not hard for you to write a critical analysis that sounds convincing to those of us (almost all of us) who aren’t as well acquainted. That being the case, the things that give me pause are:

    1. When one has strong biases, it’s easy to lie to themselves about complex issues. Your side trips to tie your criticism of the proposal to what you consider misguided trust in American exceptionalism undermines your objectivity. [ https://pedestrianobservations.wordpress.com/about/ ]
    2. Tesla Motors may not be profitable, but it sure has come much further and much faster than I thought was possible. What was your prediction?
    3. SpaceX can’t be described as anything other than successful. What was your prediction? http://en.wikipedia.org/wiki/SpaceX
    4. Experts in a field or industry tend to be very conservative about the field or industry. Examples from history are legion with outsiders coming in and making breakthroughs.
    5. Rather than denotative words, you continually use connotative words like “barf ride”, a style which typically is used to elicit an emotional response to sway the reader to one’s side. It’s good for entertainment, but I distrust this.

    You may well be right, but I can’t tell. I know that people have often succeeded at completing seemingly impossible projects despite experts, and most people, doubting them and doubting them with very good reasons. Sometimes you just have to be brave and go for it and the problems sort themselves out.

    Also, as a citizen of California, I’m against the proposed HSR project regardless, as it’s a probable boondoggle. If you’re against boondoggles, I hope you are too.

    • Ben Phelps

      The question still remains: why on Earth would HSR be a boondoggle but not the hyperloop? What really makes it so much different? That’s the heart of the argument- that the hyperloop is actually not different enough for the same problems that plague HSR to plague it as well. The hyperloop very well could be faster than HSR, but in order for that to be true, it would have to have less capacity, have less stops (serving fewer people), and be much straighter, making it less useful and much more expensive. It’s not possible, with this proposed technology, to have it both ways.

      With Tesla motors, Musk took an existing technology- the car- and improved its efficiency and its battery life. (Let’s assume for argument Tesla is an unbridled, continual success). A similar breakthrough here would be if he figured out a new way to build Pylons for like 1/10th the cost of what they actually cost, which he seems to suggest in his paper. Why in the world would this also not benefit HSR if he had done it? Hallelujah! We just figured out a way to substantially REDUCE the cost HSR!

      The problem isn’t that it’s not an impossible technology, just that it doesn’t actually solve the problems that make traditional HSR really expensive. If one is a boondoggle, the other is a boondoggle as well for the same reasons.

      And that’s assuming all the technical gotchas are solved easily with an unproven new technology.

      • Nathanael

        Yep. This:
        “With Tesla motors, Musk took an existing technology- the car- and improved its efficiency and its battery life.”

        Actually, I’ll go further: there is nothing original about the Tesla Model S except the combination. It’s all proven tech.
        (1) AC induction motors — used on every modern train
        (2) Standard automotive rear-wheel drive train
        (3) Standard automotive front-wheel steering
        (4) Standard automotive suspension
        (5) Standard automotive frame
        (6) Standard automotive body
        (7) Off-the-shelf batteries
        (8) Standard electrical engineering connecting batteries to motor
        (9) Off-the-shelf inverters connecting wall current to batteries

        Really, the thing about Tesla is that it’s all so *obvious* technically. Musk even gave a lecture where he said something which I’ll paraphrase:

        “GM was producing the EV-1, Toyota was producing the RAV4-EV, etc., and I figured I didn’t need to do anything, electric cars would take over without me lifting a finger. Then I looked back 10 years later and said, wait a sec — who killed the electric car? So I funded an electric car company.”

        “A similar breakthrough here would be if he figured out a new way to build Pylons for like 1/10th the cost of what they actually cost, which he seems to suggest in his paper. ”

        Yep. Would love it if that happened, but it hasn’t.

        • Adirondacker12800

          (7) Off-the-shelf batteries

          Which didn’t exist when GM and Toyota were producing.

  29. Pingback: The buzz about the loop | The Mongrel Dogs Who Teach
  30. Charlie Green

    Mr. Levy,

    Your blog entry is the most devastating debunking of Hyperloop that I’ve read. However, the persuasive power of this piece stems from the analytical (and empirically-sourced) take-downs of Musk’s proposals. Put simply: your scientific rebuttals are impeccable. However, in my humble opinion, you go off the rails (intended) when you resort to ad hominem attacks upon Musk’s motivations and/or character. (I ascribe Musk’s faults to hubris rather than 3-dimensional marketing chess…) It leads many readers to question YOUR motivations and consequently devalue what you have to say. Certainly, it cannot be fun to be an expert in mass transit and view a dilettante interloper garnering so much attention with a proposal that seems so laughable. However, your approach allows critics to paint your arguments as simple ‘sour grapes’. Perhaps, they will say, this is simply someone with a vested interest in HSR consulting fees (see how that ad hominem tactic leads to ad infinitum unpleasantness?)

    Unlike a significant majority of the population engaged in political and religious discourse, I find that I am more persuaded by reason and analytics than by recourse to calling an opponent ‘an asshole’.

    The most constructive thing you can do is post your technical critiques on the Tesla website. Venting your spleen is not good for either your health or the advancement of your valid points.

    • marty fouts

      I strongly concur. Had this post not been pointed out to me by someone I respect, and I had come across it randomly, I would have stopped reading after the first paragraph because of the sour grapes. As it is, I’m having trouble accepting the criticism that I’m not competent to judge, because of the personal attack on Musk, and because some of the criticism I am competent to judge is in error. I don’t know Musk, but he does have a track record of walking into a field he is unfamiliar with and accomplishing what established experts dismiss as impossible, such as having made a lot of money from Tesla, which itself has had a recent profitable quarter.

      • dhogaza

        “I don’t know Musk, but he does have a track record of walking into a field he is unfamiliar with and accomplishing what established experts dismiss as impossible, such as having made a lot of money from Tesla”

        How does solving a business problem (electric cars are old hat, the Tesla is an evolutionary step forward, not revolutionary) relate to what’s being discussed here, i.e. the engineering issues involved with his scheme and the costs associated with them?

        BTW, the valley is filled with dotcom types who made large sums of money only to see their companies quickly disappear. They still made a lot of money, though. This makes them geniuses?

  31. LDL

    > internal diameter of 2.23 meters and the passenger-plus-vehicle tube would have an internal diameter of 3.3 meters, 47% more. Despite that, the tunneling costs on PDF-p. 28 are $600 and $700 million, a difference of just 17%.

    Wouldn’t tunnel cost scale with cross-sectional area, not diameter? 3.3^2 / 2.23^2 = a factor of 2.2 or +120%, so it’s even worse than what you criticise.

    • Alon Levy

      I think the costs actually scale with diameter more, because the amount of lining required is linear in diameter. At least, a BART proposal quoted upthread scales with diameter and not cross-sectional area: see the bottom two lines of the table in PDF-page 20 here.

      • LDL

        Seems to be something between radius^1 and radius^2, depending on some factors that are not detailed in the pdf. Interesting. I thought the digging / material removal would be far more expensive than anything else. Interesting, thanks.
        BTW, for the benefit of others: It is pdf-page 20, which is page 19 according to page numbers.

          • Richard Gadsden

            I’ve been watching Crossrail (in London) very closely, and TBMs are incredibly efficient. For just digging, once you’ve built the TBM (they’re not cheap, but not bad if you’re digging lots of tunnel), a longer tunnel costs very little more. A wider tunnel just means a bigger TBM (and they scale up well). But the concrete lining is not only more expensive, it’s a much more manual process than the digging, so you have a lot of labour costs.

  32. Greg

    Fascinating analysis. FWIW, I think your strident tone makes it harder for a lot of people to accept your arguments. Musk’s proposal does seem to include a lot of hand-waving, but to be fair, I think Space X and Tesla give him a lot more credibility than your average “successful person.”

    The details of hyperloop and California HSR aside, what’s your opinion on the promise of evacuated tube concepts versus traditional HSR as a paradigm for the future of middle-distance public transportation?

    • Alon Levy

      I was debating whether to write just a factual rebuttal or put it in what I think is the sociopolitical context in which people listen to Musk. Ultimately I think the context also matters for too many other things in the politics of transit, intercity rail, and urbanism: I think the idea that he’s a tech billionaire who’s building cars so he obviously knows what he’s talking about with rail comes from the same place that leads people to wish for an autocratic mayor who will Just Get Things Built.

      Re evacuated tube concepts, I think very little of their applicability for medium-distance travel. As long as security checks are required, the time it takes to wait at the vactrain station is going to eat most of the time savings at the LA-SF scale. The final approaches at the city ends, which HSR can more or less do on legacy track, are also a bigger slice of the cost. At longer range, the primary competition becomes airplanes, and then vactrains start looking better. Extreme Engineering had it right when it was focusing on a trans-Atlantic tunnel. Nothing that people should worry too much about now, but it could be a worthy international project in 30-50 years, especially if Transrapid and JR-Maglev evolve into more mature and hopefully multi-vendor technologies.

      • marty fouts

        I think you are underestimating Musk’s audience. Those who accepted the proposal uncritically did so because it is a slick well put together presentation. Musk’s status got him noticed, but his presentation sold the deal. For comparison, think back a few presidential elections to how people dealt with a tech billionaire whose presentation was terrible.

        I don’t know the LA end of the HSR plan very well, but there’s definitely going to be no use of legacy tracks along the proposed right-of-way into San Francisco, The SP track in place doesn’t meet the grade separation requirements and would end up with a mix of freight, low speed passenger, and HS traffic. The right-of-way is used, but new trackage is intended along that route.

        • Joey

          Low speed grade crossings are no object for high speed trains. Of more concern is the fact that the gates would be down longer since there are more trains. Total grade separation should probably happen eventually, but it’s not a priority. And large portions will be quad-tracked, but there are sections (Bayshore-Transbay) which don’t need additional tracks any time in the foreseeable future.

        • Ted K.

          Re: “SP track”
          I believe most, if not all of Southern Pacific’s rails were replaced by Caltrain in the 1980’s / 1990’s. The old tunnels in San Francisco could do with substantial upgrades though.

          Re: “doesn’t meet the grade separation requirements”
          First, HSR consists can transit level crossings – it just must be at a slower speed. Second, the Caltrain corridor is in the midst of a multi-decade campaign to eliminate level crossings. The latest separation to enter service is in San Bruno. Part of the problem is that some of the crossings are [a] clustered and [b] in high-NIMBY towns.
          More: Grade Separation: The Decadal View (29 Dec. 2012)

        • BruceMcF

          Joey is quite right, you are behind the HSR plan into SF by several iterations ~ the plan at present is to run HSR, Express and Local on the existing corridor, adding track to expand capacity as the frequency of the HSR services is ramped up, and to run the freight on the corridor in the middle of the night during the HSR curfew. Caltrain is presently applying for Tiger funding for the electrification.

  33. Digital Cosmology (@DCosmology)

    Hi again. You wrote:

    “The proposed relationship between curve radius and speed in the Hyperloop standards is for a lateral acceleration much greater than 4.9 m/s^2 in the horizontal plane: 480 km/h at 1,600 meters is 11.1 m/s^2. This only drops to 5 m/s^2 after perfectly canting the track, converting the downward 9.8 m/s^2 gravity and the sideways acceleration into a single 14.8 m/s^2 acceleration vector downward in the plane of the capsule floor, or 5 m/s^2 more than passengers are used to”

    IMO the above statements must be clarified a little. At the frame of reference of the capsule, there is a gravitation acceleration on the passenger, 9.81m/s^2, and a (ficticious) centrifugal acceleration of 11.1m/s^2 due to the lateral acceleration imposed by curvilinear motion. Imo this is the proper frame to evaluate the forces on the passengers, not the ground. These accelerations are nearly opposite, save a very small angle between them. Therefore, the net acceleration along the vertical plane with respect to the capsule is about 1.3 m/s^2 and along the plane of travel the inertial acceleration is just the component of the gravitational force, which for a very small angle is much smaller than 9.81m/s^2 (it gets to g when the capsule is on a free fall).

  34. cosmicbuzz

    If Alon extract only the technical content from this post to a separate post it will be a lot better. I found it so hard to search for the cost breakdown of the HSR. It is very useful for a normal engineer (I am software engineer) to estimate and work on the cost breakdown of a 30 meter section, which is very comprehensible for a lay person. Please help me (as many others) to visualize the cost estimate.
    For ~600km hyperloop from LA to SF, if the tube/land cost is targeted at $12B, that is roughly $600k per 30 meter. What is the cost breakdown of land (in middle or along freeway), 1 prefab pylon, 2 prefab tube (10ft wide), construction(man-date and machines), and misc? Is it more expensive than constructing 3 houses? What would be the realistic cost? Maybe 4 tubes might work out too.
    For the same route/rail/land, what does HSR cost per 30 meter currently?
    What does a train cost?
    Most will not mind sitting a 30 minute ride time, much better than a comfortable 2.5 hour ride. Fast security check lane with one laptop bag should not take long. 30 min is huge difference from 2.5hr. Most can work at home few days in LA, and for few days take 2 hour round trip to SF for cool jobs/fun. Can’t do that with HSR. The life/job style change will be much bigger.
    In my opinion, terrorism/fear is the main cost. Let’s say a tube is bombed, the air rush in pushing in both directions, slowing down the pod approaching the bombed section. The pod emergency break. The pod screech against tube or even dangle with the tube. But my guess is that there might not be death, or not many. Replacing tube/pylon and inspection would not take too long. Video/pattern recognition technology advance so fast that it will be virtually guarded at all time. If a suicide bomber bomb inside a pod, he kills himself and 27 people. He can do a lot more damage in other places.
    I, and many others, will highly appreciate effective technical analysis.
    Anyhow, I believe China will be the first to build hyperloop. Another kick at US doesn’t add too much hurt.

    • Alon Levy

      Don’t think of it as just 1 prefab pylon and 2 prefab tubes. Those are just the raw materials; they also need to be assembled with sub-millimeter tolerances, and that’s hard. For the same reason, a highway viaduct is much more than prefab pylons, slabs of concrete, and compacted asphalt, and an HSR viaduct is much more than prefab pylons, slabs of concrete, concrete sleepers, steel rails, prefab poles, and copper wire.

      Re video recognition, we’ll see where right-of-way security progresses. When François Hollande took a presidential trip on the TGV rather than on a plane, they posted a guard at every railroad bridge, but that’s security for just one person. HSR track damage is easily survivable, since HSR has much shorter stopping distance and is already at atmospheric pressure; in contrast, at Hyperloop speed, heating of air due to compression is an issue at full atmospheric pressure, and a tube breach may be unsurvivable for the first capsule even if it is a stopping distance away.

      For the 4/1 vactrain post I had, I imagined steel doors spaced around the tube that would seal behind and ahead of any rupture, a stopping distance apart, so that at the very least, only one train would be affected.

      • cosmicbuzz

        Thanks for the reply. For the breakdown of land, pylon, tube, construction machines, and assembly, you emphasize that assembly is hard. So the key point boil down to: how many man-dates to assemble a 30 meter section?

        Let me try: out of the $600k budget per 30 meter, let’s say $200k goes to assembly only. Supposed $1000/man-date, then it is 200 mandates. That is 20 man working for 2 weeks. Is it a good estimate? If it make sense, then $12B to build the length of tube is not bad. If not make sense, then what is the right man-date? Is it 30 man working for a month to put up and align the tube? That is $600k per assembly per 30 meter, total tube route is $24B. Even so, it is still much cheaper than HSR.

        As for terrorism, compared to other possible bombing/shooting in mass gathering, the worst case of 28 death for first pod is about average.

        • Joey

          Musk’s proposal has much less than a stopping distance between pods, i.e. the next pod will not be able to stop before it hits the carnage of the first one. And that already has capacity problems…

          • cosmicbuzz

            Stoppage in a tube is different from in highway. The air between pods is the best crash prevention. It is almost impossible to compress those air to 0, provided that the later pod shutdown the air intake soon enough. You can do the experiment easily.

            I get an idea, deploy several airbags inside the tube to stifle the air, let the pod hit several airbags and stop.

            Come on, it is so much fun to innovate than giving up.

          • Joey

            I don’t think you understand what I’m saying. The pods have some distance that they must travel to stop in an emergency. It doesn’t matter exactly how you stop, though putting a bunch of air in front of the pod is probably a bad idea because of the heat arising from air friction. But in any case, this distance exists, and the proposed system has less than this distance between pods. The limiting factor on decreasing this distance is the fact that the pods contain people. Even at a roller-coaster scale 0.5g, it takes nearly 8 km to come to a full stop, which happens in just over a minute. Any more than that and you have to restrain the passengers to their chairs (much in the same way a roller coaster does) or risk serious injuries from deceleration. And I’m not even sure 0.5g is safe with only seatbelts.

        • Alon Levy

          Don’t try to do it from first principles unless you’re extremely familiar with civil engineering and construction (I’m not, and neither are the people I’m referencing on this). This is why looking at HSR costs is such an important sanity check: the civil infrastructure required for a given viaduct height is similar – the pylons depicted in the proposal look similar to the pylons supporting elevated conventional trains – and so the costs should be similar.

          The reason I bring up viaduct height is that Hyperloop has much larger vertical curve radius, so it can’t climb grades as easily and so to avoid going below ground it requires taller pylons on average.

          • cosmicbuzz

            Thanks for the reply. So we do arrive to the real gut of the problem. Good estimation of the cost of civil engineering per 30 meter is FAR more important than other debates. Without this estimate it is a waste of time. Without civil engineering expert we should just stop debating the feasibility of the cost.

            Let’s bump up the budget, how about $1million per 30 meter? It just seem too big for me. Even with that, it is still cheap at $20B total for the tube. How about $1.5million/30meter … 😉

          • Alon Levy

            Including overhead, management, and contingency, the cost range for California HSR’s elevated segments is $1.5-2.5 million for 30 meters. The tunnels, the Bay crossing, and the urban segments in LA and SF that Musk is neglecting are extra. And since Hyperloop is not technically compatible with legacy rail, those urban segments are unusually expensive since they require new els or tunnels. HSR can share tracks with commuter rail on approaches, which is a huge advantage over maglev and other more modern technologies.

          • Joey

            Why the obsession with 30m? Isn’t it easier to work with something that scales better with distance, i.e. cost per km? If you want to know the cost for one segment of viaduct it’s easy to multiply by 0.03, but if you’re trying to do large scale cost estimates it makes sense to work with something larger and more standardized.

          • cosmicbuzz

            I am not obsessed with 30m (1 pylon, 2 tubes). For lay person to visualize it and understand it, it is much easier to work with 30m scenario. We just help each other to get a good feel of the problem (knowledge is gratifying), none of us will do the actual work.

  35. Ian S.

    As a professional mechanical engineering working in to aerospace sector for a smallish private company, I find this pretty typical of white papers that come from CEOs. We make our living by winning contracts and to do that we need someone finding them. In our case, its the CEO with the industry connections and knowledge. The people on the receiving end of proposals such as Musk’s HyperLoop are almost always the people who have control of the purse springs. Its meant to sell a concept, be mostly defensible, and hopefully get money into our pocket.

    This can be frustrating for engineers, but often times rooms full of engineers lack direction – and we certainly lack the star power required to get gobs of money moving. Given a nudge in a certain direction, however, engineers can spur on great things from those working out the details.

    Many of your thoughts on budgeting may amount to a lack insight as to what differentiates Tesla and SpaceX (you know, the private company launching people into space) from many comparable companies. These ventures took pains to redevelop, if needed, entire processes that were seen as inefficient. They may be unattainable given the current state of art, but what if you advance the state of art?

  36. Max Schlienger

    Thanks for providing a more realistic review of Musk’s technology. We agree with your mathematical analysis of acceleration rates and passenger comfort levels. However, we do not agree with all of your thoughts especially as related to elevated vs. ground level tracks and the use of traction and conventional rails.

    We are a small operation, self-funded. Take a look at http://www.flightrail.com when you have a chance to see our atmospheric propulsion transportation system with passenger modules operating above but magnetically coupled to the pneumatic tube. If you are ever traveling in the San Francisco/North Bay area, please visit our 1/6 scale pilot model VECTORR™ system. (Also note that atmospheric propulsion goes back to the 1840 era in England – Isambard Brunel).

    • Digital Cosmology (@DCosmology)

      Are you saying you agree with him that

      ““The proposed relationship between curve radius and speed in the Hyperloop standards is for a lateral acceleration much greater than 4.9 m/s^2 in the horizontal plane: 480 km/h at 1,600 meters is 11.1 m/s^2. This only drops to 5 m/s^2 after perfectly canting the track, converting the downward 9.8 m/s^2 gravity and the sideways acceleration into a single 14.8 m/s^2 acceleration vector downward in the plane of the capsule floor, or 5 m/s^2 more than passengers are used to”

      meaning that lateral acceleration and the acceleration of gravity add up in the frame of reference of the tube?

      • Scott Andrews

        YOu are sort of correct, but there is no free lunch here. If the vehicle were canted 30 degrees (I am using this number to keep the arithmetic simple, not because it might be the proper angle), the force of gravity would be decomposed into two parts, a component normal to the vehicle will be 9.8cos30 (8.5 m/s^), and an inward and downward acceleration will be 9.8sin30 (4.9 m/s^) lateral to the vehicle frame of reference. The 11.1 m/s^2 lateral acceleration can also be decomposed into two vectors in the same tilted frame. The normal component will be 11.1sin30 (5.6 m/s^2), and the “lateral” component will be 11.1cos30 (9.6 m/s^2). So the net accelerations felt by the passengers will be: normal=8.5+5.6=14.1 (1.6G), and the net lateral acceleration will be 5.6-4.9=0.7 m/s^2. So the lateral acceleration felt by the passengers would not be too much, but they would weigh more than half again as much. A200 Lb person would weigh about 320 Lb. That 12 ounce Starbuck’s coffee would feel more like a 20 ounce big gulp.

        The real issue here is that under this sort of acceleration transformation, life would not be normal. Obese people would be at risk, pregnant people would probably be disadvised to ride, etc.. It might not be Alon’s “barf ride”. but it would not be the silky smooth Shinkansen either (I have ridden thousands of miles on that train).

        I agree that Alon’s approach has been a bit histrionic, but the fact is that Elon’s concept is chock full of wishful thinking and ignored realities. Lots of folks will object that these reality checks are just out of date “old think”, but the reality is that concrete costs what it costs. If you need more to do X, then it will cost more. If you say you will do it somehow cheaper, then it will either be less effective, or you have some new innovation that allows you to do it better for less.

        One post above noted that if there are improvements that can reduce the cost of hypeloop, then to the extent that they relate to the structural and grade elements of the system (not the vehicle elements), then they will presumably reduce the cost of HSR too.
        From my reading of this, the value added by HL is speed, and (supposedly) reduced energy, but the cost for this is comfort, capacity, safety, and technical risk. In addition, the energy costs are somewhat suspect. The tube will leak, so there will be a finite and sizable cost to maintaining the low pressure. The NTSB will not allow thew following distances proposed due to insufficient stopping distance, and the potential for catastrophic failure, so the capacity will decline further.

        It is arguably a cool idea. My original musings on this are for an underwater tube from Japan to LA, with 1G acceleration over half the trip and 1G deceleration over the other half. Cool. 18K mph peak, 2 hours trans pac…nearly dead passengers at either end (praying for a 10 hour flight on the return trip!) , huge costs and horrific failure modes.

        It’s true, innovators don’t follow the rules, bit at some point, when lives are at stake, the rules of physics still apply.

        I look for Tesla, as cool as it is, to suffer horribly under the coming weight of warranty returns and liability lawsuits..because in engineering there is no free lunch..


        • Scott Andrews

          Correction.. The net lateral acceleration will be 9.6-4.9=4.7 m/s^2 (about 0.5 G)..so this will be something of a roller coaster ride.. Maybe it’s just me, but after years riding the silky smooth Shinkansen, I find the Acela (DC-NY) and the Thalys (Paris-Brussels) to be jarring and uncomfortable… this will be 10 X worse..Personally, I’d rather take the extra, net 30 minutes and ride in comfort with a coffee in the AM and a beer in the evening…

  37. cosmicbuzz

    Can anyone give an answer to this?
    For ~600km hyperloop from LA to SF, if the tube/land cost is targeted at $12B, that is roughly $600k per 30 meter. What is the cost breakdown of land (in middle or along freeway), 1 prefab pylon, 2 prefab tube (10ft wide), construction (man-date and machines), and misc? Does the number make sense?
    For the same route/rail/land, what does HSR cost per 30 meter currently?

    • Ben Phelps

      Unless someone can explain convincingly why building a viaduct and pylons for two tubes is manifestly different or cheaper than building a viaduct and pylons for two tracks, I don’t see why you can’t just use the HSR estimates for how much a viaduct costs per mile in the central valley. Unfortunately doing a little googling myself on this has proved pretty futile, so right now I’m deferring to Alon. The numbers I’m finding on blogs of various bias and dates are all over the map. $44 million per mile?

      But I’m pretty skeptical the Musk has somehow swooped in and solved a problem that transportation wonks and experts have spent a lot of time thinking about. And the bottom line is also in line with common sense: I mean come on, at grade is just cheaper than building pylons and viaducts. It’s obvious. Where the HSR is on the ground, it’s far far cheaper per mile than when it’s not.

      As for prefab pylons saving money: as someone who’s driven up and down the 5 many times, I think this is pretty wishful thinking. If you’re actually following the 5, much of it is quite hilly. For instance, the entire segment North of Coalinga to the 580 split. I do believe this is another reason the HSRA chose NOT to pursue the 5 as a viable route. If you’re dealing with these hills, prefabbing a bunch of pylons doesn’t seem practical or at least useful since they will all have to be a slightly different exact height.

      Here’s some numbers for reference. The current cost of adding a lane to the 405 through the sepulveda pass in LA is estimated at $1.34 billion (well over budget). The Bay Bridge replacement is coming in at over $6.3 billion. The transbay terminal and Caltrain extension is estimated to cost $4.185 billion. And I’m expected to believe we can build a Hyperloop 700 miles long for $7 billion?

      • Arche Leach

        As a note: IF the day actually arrives for the actual trains for the CAHSR, the trains are to be the EMU Shinkansen/ICE3 types with distributed traction and those types of trains are rather good with inclines. The actual reason the CAHSR goes thru the 99 corridor is because we know from the French TGV and now the Chinese HSR that HSR can make places like Merced and Fresno into the bedroom communities for the the Bay Area and Southern California and that would result in bringing big economic benefits to those areas and HSR was sold to those areas as for why to build HSR in California.

  38. Keep Houston Houston

    Hyperloop doesn’t sound like fun. So I cram into this pod that’s 4.3′ wide – two feet narrower than my Crown Vic. Then I recline way the fuck back because the ceiling is too low to stand up. Of course this means bathrooms are a foregone conclusion. I look forward, but you can’t see in front of you. I look out the side, but the tubes are solid metal – yeah, they were glass in the visuals, but that shit got value engineered out right quick. Whatever. Nothing to see. Only going to be 30 minutes until we’re in SF, right?

    I reach over to grab my girl’s ass, except I can’t, because a big chunk of the propulsion is in between the seats. So I fold my hands across my chest to enjoy the g forces which I’ll spend the next 30 minutes experiencing with no visual frame of reference. Thankfully, I haven’t eaten in several hours. But the guy sitting behind me thought it’d be good to get a double double before he got on the train, and after 10 minutes of being thrown around the inside of the pod, he pukes.

    Of course he can’t take the barf bag to the bathroom because there is no bathroom. I look at my female companion and scratch her shoulder since that’s about all I can reach. Over the next 20 minutes two more people barf as the cabin fills with the smell of upchuck. We arrive in SF. She suggests maybe next time we just take my Ford up the Grapevine. I emphatically agree.

  39. Ben

    Let me start off by saying that this is a fascinating analysis of the hyperloop white paper. Well done.

    Also, i want to make clear that I
    a) have no horse in this race (I love new tech and I love HSR) and
    b) I have no expertise in this area.

    That out of the way, I have a couple of questions based on a first reading of your post.

    Land Cost
    You say “Central Valley land is cheap; pylons are expensive, as can be readily seen by the costs of elevated highways and trains all over the world.”

    But isn’t that comparing apples and oranges (or at least, apples and some orange colored apples)? You should really be comparing two things separately:

    a) the cost of a full right of way vs. the cost of leasing enough land to hold the pylons that are not located on public land.


    b) the cost of manufacturing and placing the pylons vs. the cost of laying down and reinforcing a proper rail bed including all elevated crossings.

    G Forces
    You say “Even 4.9 m/s^2 in the horizontal plane is too much. With perfect canting, it combines with gravity to accelerate passengers downward by 11 m/s^2, 1.2 m/s^2 more than the usual, twice as high as the usual standards. Motion sickness is still to be fully expected in such a case. Transrapid’s 4.37 m/s^2, which adds 0.93 m/s^2 in the vertical component with perfect canting, is the limit of what’s possible.”

    But there seems to me to be some assumtions here that may not be appropriate (and again, I am no expert so please excuse me if I get this wrong).

    First there is the discussion of lateral g forces but no mention of the frequency of oscillations. If a train sways back and forth then even minor g forces will lead to motion sickness. But if the g forces are constant over a slightly longer period of time, does that change the amount that passengers can comfortably tolerate? This is an honest question. I don’t know.

    Some googling tells me that airlines regularly subject their passengers to vertical g forces that are easily .25 on either side of normal on a regular basis throughout a normal flight (mostly at take off and landing) and can briefly go a fair bit higher for brief moments in time. Yet you are suggesting that the maximum is 1.094 g’s. How do you account for this discrepancy?

    • Alon Levy

      The cost of the ROW is small either way, though the idea that you could save money by only buying land at the pylon footprint is at odds with past experience with elevated transportation projects. If an authority tried to buy only the pylon footprint, the landowners would sue for reverse condemnation and win. That’s why elevated highway and rail builders buy continuous corridors of land.

      As for reinforcing a rail bed, it’s not much harder than reinforcing a steel tube, assuming equal tolerances. But the railbed has laxer tolerances because speeds are much lower and there’s no need to maintain a near-vacuum.

      Re g-forces and motion sickness, the oscillations add to the motion sickness, yes, but this depends on train suspension. Borrowing from French regulations, the FRA’s ongoing rule revision puts the limit at 0.15 g for a perfectly rigidly suspended train; but even trains with active suspension, i.e. tilting into the inside of the curve, can’t achieve such high rates, topping at about 0.12 g. To ensure passenger comfort, this requires smooth spirals to limit jerk, which the proposal ignores. The other coefficient I borrowed from is the coefficient for vertical acceleration, which is less dependent on oscillation since the train doesn’t sway forward or backward, only sideways. That coefficient is actually less than 0.094 g, at most 0.068 g.

      Airplanes subject their passengers to higher forces at takeoff and landing, but they also induce more motion sickness than trains, by a large margin. And Hyperloop proposes to subject passengers to even greater forces throughout the trip.

      • cosmicbuzz

        To acquire land for small pylon footprint at, along, or closed to highway should be cheaper than current HSR route.

        To solve oscillation problem, can easily modify the pod design to allow a passenger container that can semi-suspend and oscillate inside the pod shell to cancel out the forces, so passenger will hardly notice the sway inside the pod, without outside reference.

        • Alon Levy

          Land acquisition is about 10% of the cost estimate of HSR, and Musk is cheating by not even serving any of the cities where land has nontrivial cost. Dublin and Sylmar are cities only in the technical sense. The dominant cost factor is civil infrastructure.

          • cosmicbuzz

            If land is $7B cost, so that really means civil engineering the tube is the most important cost factor. I think $1million budget for 30m 10ft tube (skinnier and less complex than other viaduct) is enough. An expert calculation will prove it right or wrong.

            Do you agree my idea of having passenger container oscillating/moving inside the pod shell will make it comfortable enough?

          • Jacob

            So it could be feasible but cannot be financially viable?

            The CGI photo of the Hyperloop looks as if it is a glass tube. Yet the 58 page document never mentions the word “glass”! That is very dishonest. If the entire system is in steel tubes, a lot of people wont want to use it.

            It would be great if Musk could slash the cost of Maglev, like he slashed the cost of space rockets and electric car batteries. Because unlike Hyperloop, maglev has already been built and is not in claustrophobic opaque tubes.

      • Ben

        But the proposal suggests (whether realistically or not) to primarily use the ROW between the two I5 lanes and to only move onto open land when it is technically infeasible to maintain a curve with as tight a radius as the freeway exhibits. In these cases the white paper seems (to my recollection) to suggest leasing space on private land similar to the way it is done with some wind arms. The idea is not to purchase land or to use eminent domain.

        With regard to the g forces: Assuming you bank the capsules in a way completely analogous to an airplane, you wouldn’t have any lateral g forces. It would all be “up and down”. In those cases, you could sustain higher g forces for a period of time without unduly discomforting the passengers. And unlike an airplane, there would not be any sharp changes in these forces which is, I suspect, what causes much of the motion sickness. A slow, smooth buildup of forces to the maximum (say, .25 g’s above or below normal) shouldn’t be an issue any more than it is in an airplane.

        Now whether the proposal Musk puts forth manages to do that or not, I don’t know. But it seems to me that using a standard HSR benchmark for g forces does not make sense here.

        • Joey

          What Musk proposes would amount to an additional 0.5g if canted perfectly. Alon talks about this specifically in his post.

          • ben

            Agreed. And that may make the whole thing a non starter. But I was referring to the idea that the maximum g forces had to be on par with those of a high speed rail system when in fact it could actually approach that of a commercial airliner. Once you decide that that is acceptable then maybe you can go backwards and actually design a system that uses much of what was proposed, but modifying it enough to keep the forces within this higher limit.

          • Joey

            The problem is that at those speeds, curve radii are on the order of tens of kilometers and there’s no way to avoid objects like small towns and mountains which might be in the way without tunneling. It also has to be extremely flat because changing grades takes even more distance.

          • cosmicbuzz

            pdf p42 has a graph of step-up speed. From LA, at ~8min, it accelerate to top speed of 760mph because of the bigger radii. I did not check and match the route section map and radii. The speed can vary depend on radii.

            The pylon need to be constructed to consider the cant and leave a wide margin. In my other comment, I propose a modification that inside the pod, the inner container that contain passenger and major weight can oscillate/move inside the pod, and will meet the comfort requirement. Train can not oscillate so only rely on perfect cant to provide the comfort.

          • Joey

            Again, you’re experiencing 150% normal gravity if it’s canted perfectly. That’s not within most definitions of comfortable.

          • cosmicbuzz

            If you look at the p42 graph, there are only total ~2~3minutes that are accelerated. To reduce g, you always can prolong the acceleration time with lower acceleration rate. If the expectation is like ~3 times of airplane ascend time, I think most people can deal with that. If the result is 40min travel time, it is still very fast.

            Again, cant is mostly for comfort, an oscillating inner container inside pod solve it.

            I drove on I5, it is very flat. The route shall be by the side of I5, so some part is at high pylons, some part is down to earth, but not costly as tunnel. It is only 10ft wide, very narrow by comparison.

            I truly believe that when you are positive and try to solve problems, and face problem honestly, there are so many options to choose from and get few very good ones, and throw away many not so good ones.

          • Alon Levy

            When you add a downward weight vector of magnitude 9.8 m/s^2, and a sideways centrifugal force vector of magnitude 11.1 m/s^2, the resulting vector has magnitude 14.8 m/s^2. No way around it; best you can do is change the vector’s direction. Oscillation is not going to produce any downward acceleration, so it’s not going to produce anything counteracting this force vector.

          • Ben


            Yeah. I started to do some of the calculations and there are significant forces involved. But if the system were to be scaled (performance wise) could you design it to get half the speeds (and by that I mean, half everywhere: dropping to 250 kph in the bends) and still make it economical?

            Tolerances would lessened. Your pressure could be 4 times higher and still maintain the same air resistance. Pumps would be less expensive. The danger of decompression is much less (though the vacuum is still 20 times greater than an airliner at 50K ft). Energy use would more or less be the same depending on how often you had to re-accelerate the pod and how the air bearings would work at this speed.

            I have no idea if this makes any sense to do. I’m just speculating.

          • Joey

            250 kph? That’s well below the limit of even regular old HSR today (which is pushing 400 now).

          • Ben

            Well then ramp the speed back up then. Physics is physics and if you can do a gentle bend on HSR (which, by the way I am very much in favor of), then you can do a gentle bend with the hyperloop as well. If the hyperloop can only climb at a specific rate due to speed, then the train cannot do it any faster. But the flip side may not be true. If the hyperloop can bank into a turn more aggressively than the train, it can turn on a tighter radius. If the hyperloop car is lighter then it may be able to accelerate to a faster speed along sections where it wouldn’t encounter any bends. Note that I say “may”. I really have no idea. I’m just wondering out loud.

            To try these scenarios out, I finally had a bit of time and put together a spreadsheet that lets you play with different G forces and velocities and get back out bend radii both horizontal and vertical that will produce those G forces. I saved it as a google document here:


            I would be delighted if smarter folk than I (which is most of you here) looked at it and made sure I am not spewing complete nonsense.

            Some results:

            All of these assume the following:

            1) The hyperloop banks at the perfect angle so that all G forces are experienced in the “downward” direction (i.e. down from the frame of reference of a passenger).

            2) The hyperloop will either change direction in the horizontal plane OR it will change elevation in the vertical plane. It will not do both. (The only reason I am making this assumption is to make my math efforts easier – I am not arguing that that is how the actual system would be designed).

            At 540 Kph, assuming a maximum “downward” G force of 1.25 (similar to what you get on a regular airplane) you would have to have horizontal bend radii no less than 3.29 Km and vertical bend radii no less than 9.88 Km.

            At 1000 Kph, assuming a maximum “downward” G force of 1.25 you would have to have a horizontal bend radii no less than 10.5 Km and a vertical bend radii of no less than 31.49 Km.

            The smaller number (540 Kph) really does seem doable to me (I’m only speaking with regard to G forces here). So, as far as these forces are concerned, it really doesn’t seem like they will require anything nearly as bad as people seem to make them out to be (unless, of course, my numbers are complete nonsense. I would happily stand to be corrected if I have done something wrong here).

          • Joey

            Sure, but the same is true of Maglev compared to conventional HSR. That doesn’t mean that Musk’s proposal doesn’t have basic factual errors and it doesn’t mean vactrains are feasible with today’s technology.

          • cosmicbuzz

            Ben, good job putting up the spreadsheet.

            As for downward G, I am not sure if you know my suggested modification: Passenger and other weights are inside an oscillating/movable container within the pod shell.

            With oscillating container, passenger always experience downward G (remind me of the free swaying Ninja ride in Magic Mountain, it was so comfortable and Ninja fun) . There are air skis at both side of pod shell, one side will have more g force. Maybe the air skis can move too.

            It is just a 30 minute ride. You recline on the chair feeling the back and hip heavier, the drink is heavier and you drink from the straw, no big deal.

          • Ben

            That is true. But now that I’ve been able to do the actual calculations myself this doesn’t seem like such an unsurmountable problem (or at least half of what Musk describes seems ok).

            First, using the values Musk supplies in his white paper, the maximum *downward* forces in a perfectly canted pod would be 1.5 G’s. That is using his values for moving at 480 Kph and traversing a bend radius of 1.6 Km. This is still within the values that commercial airline passengers feel for brief periods of time. At that speed (and that bend radius) the passengers would feel the G forces build up from 1 G to 1.5 G’s over the period of 6 seconds only to have it start to fall off again back to 1 G over the following 6 seconds. This is hardly egregious.

            Unfortunately, the second set of values that Musk uses seems a bit more off to me. He suggests a top speed of 1220 Kph for areas that have bend radii less than 4.8 Km. Under these conditions the passengers will experience a G force load of 2.65 G’s – progressing along a similar ramp on and off curve as to what I describe above.

            Regardless. Let’s return to the first set of numbers. Assume you want to reduce the G forces to a much more common 1.25 G’s as a maximum. Keeping your overall speed the same (480 Kph) during these bends, you can have a bend radii of 2.42 Km in the horizontal plane and 7.2 Km in the vertical. The ride is then very very comfortable and the radii are not out of the question technically. These gentle G forces would ramp up over 9 seconds and then fall back to 1 G over another 9 seconds.

            Furthermore, Alon makes a very good point. If ROW costs are as low as he says (and I have absolutely no reason not to believe him – he is one of the few critics of Musk’s plan that I have read that seem to have actually done some homework) then by not slavishly sticking to the I5 corridor, these bends could be kept to an absolute minimum.

            With regard to stopping. At 1,220 Kph you can brake to a stop in 30 seconds and still only experience 1.15 G’s. It is extreme, yes. But still well within the tolerances of a human body. And remember, this is full emergency braking in 30 seconds. But the capsules will be more than 30 seconds apart even at the peak rush hour because they are *leaving* 30 seconds apart at the slow end of the tube. Once at speed they will spread out, only bunching up again to 30 second intervals when speeds are much lower and stopping forces much less.

            So… again, I have no idea if the hyperloop plan is the start of a good idea or not. But (with the exception of the one set of numbers that don’t seem to make sense to me) the G forces on the passengers do not seem to be anything to worry about.

          • Ben


            I understand what you are describing, but it won’t make any difference in the actual G forces experienced. Tilting the entire pod (aka banking into a turn) does the same thing.

          • Mirco

            @Ben: If the pods leave every 30s, there will also be a pod passing every 30s in the middle of the line. Its the same as in a water pipe, where the water might flow faster in a section that is thinner, but where the same amount of water passes every point, assuming there are no junctions.

            About the emergency stop: There should be a time budget for the signaling system to order an emergency break, and for the breaks to engage. Also, I think you calculated the additional horizontal acceleration, not the total acceleration experienced during an emergency stop:

            >>> v_kmph = 1220

            >>> v_ms = v_kmph * 1000.0 / 60 / 60


            >>> a_horizontal = v_ms / 30


            >>> a_g = math.sqrt((a_horizontal / 9.8)**2 + 1)


            (The acceleration experienced is given by sqrt(a_horizontal^2 + a_vertical^2)

          • Ben

            @ Mirco

            Thanks for commenting about the time between pods in the high speed section. I was wondering about that as I was writing it. I still have to think that one through for a moment because it isn’t completely clear to me what is happening between the pods as they accelerate. This was something that nagged at me as I was writing it (and your water analogy explains what was bothering me). But that said, I can’t let go of the idea that for a period of time one pod is accelerating to a higher speed while the other is moving at a constant velocity.

            For example: PodA leaves the station and (for the purposes of argument) accelerates instantly (in 0 seconds) to 100 m/s (Meters per second). 30 seconds later, PodB leaves the station and also accelerates instantly to the same velocity. Under this situation, both pods are 30 seconds apart. Then, 100 m down the line, PodA instantly accelerates to 1000 m/s. It now has 30 seconds to pull away from PodB. So for 30 seconds it travels an additional 27000 m vs. what PodB is doing (so PodA is 30000 m ahead of PodB). Then PodB instantly accelerates to the same velocity…

            …oh. I see. Once PodB gets up to speed it will be further behind, but it will be traveling at the higher velocity too and so the greater distance is made up by the increased velocity (1000 m/s will cover the 30000 m gap in 30 seconds). Distances between pods go up, but time between pods does not change (except for the brief periods during acceleration changes – on the other end of the line pods will be less than 30 seconds apart for brief intervals). Ok, that makes sense. Thanks for the heads up.

            With regard to the acceleration due to braking, I think the only interesting number is the horizontal component because the capsule does not tilt backward when slowing down. It is similar to if an airplane didn’t bank into a turn. At that point we would only talk about the horizontal acceleration because the vertical acceleration would remain constant. In this case, under braking, the vertical acceleration does not change and so the only interesting feature (and the only force that changes over time for the passenger) is the horizontal component. Does that make sense?

            Overall it seems to me that the biggest issues (from a physics standpoint, not cost/political/comfort) stem from the extreme high end of the speed discussed. If the top speed were to be dropped to something more reasonable (say, 700 Kph) then a lot of the tolerances and timing issues can be dealt with in a manner that is within reason (again, technically. Not necessarily from a cost basis).

        • Alon Levy

          What Joey said.

          But independently of lateral acceleration and cant, there are standards for upward and downward acceleration caused by vertical curves. Hyperloop ignores them, even though those standards can’t be compromised in any way due to banking.

          On another note, using the ROW between two freeway lanes isn’t how anyone outside the US builds HSR. A lot of lines are next to freeways, but not between them: it’s too constrained and deviations from the freeway’s geometry require grade separations over a busy road, which are expensive. Florida HSR was supposed to be in a freeway median and as a result had some speed-constraining curves, and the same is true of Xpress West. In contrast, French and German HSR lines are sometimes alongside freeways, since those corridors are already impacted so that mitigation costs are lower. The gentle curves required for HSR would require a very low angle of crossing, complicating the placement of pylons, and the gentler curves required for Hyperloop would be even worse than those required for conventional HSR.

          The land acquisition costs near I-5 are low. It’s mad to go there and not near Route 99, which allows for intermediate stops in Bakersfield and Fresno, or even a completely greenfield route (farmland is cheap even around 99); but if the decision to go on I-5 is made, it should go alongside the road and not between the two carriageways. Alongside also allows HSR to be largely at-grade. I’m not sure whether Hyperloop, which would need much larger vertical curve radius, could do the same – it might be possible if the route is extraordinarily flat, which is true of most but not all of the Central Valley, or it might still be possible with some earthworks but no viaducts.

  40. James Nowell

    The Hyperloop proposal has nothing to do with Tesla. Elon Musk released his information on the SpaceX site, and has no plans of attaching the idea to any of his companies. I suspect Tesla’s investors would shoot down the idea anyway (and are also probably upset the idea is being attributed to their company).

  41. DaveM

    I’m a little surprised that so little attention is paid to the intrinsically unsafe concept of traveling in a reduced pressure atmosphere protected only by the integrity of the small capsule. If that capsule were to spring a leak during the ride in the reduced pressure environment contemplated, the passengers will die a horrible death as their blood begins to boil (see Payne Stewart). An emergency oxygen supply is inadequate at the pressure contemplated and it’s difficult to imagine a quick (instantaneous) means of egress from a hundreds mile long pressure vessel.

    • cosmicbuzz

      Musk builds rocket that deal with more serious leaks. So I am not concerned.

      Also, the design already carry compressed air tank, mainly for suspension, but also can be used for emergency air.

      There will be emergency exit for every said distance.

      • Joey

        How long does the onboard air supply last? How long does it take to pressurize the tubes so that passengers can exit safely? How do passengers get out of the pod if there’s a turbine in the front and equipment in the back and the tube doesn’t provide room for the doors to open?

          • Jon Romig

            In addition to air tanks you would also need a spacesuitif exposed to the near vacuum.

    • Joey

      More worrying than the prospect of air leaking out of the capsule is the prospect of air leaking into the tube from the outside, which could rapidly cause overheating due to air friction.

      • cosmicbuzz

        There are plenty of self sealing technology to solve it. Also there definitely will be multi-layers of sealing. Also I propose the idea of deploying/withdrawing airbags to stifle/control the tube to slowdown air flow and pod, of course only when pods are at a safe distance away.

        • Joey

          Colliding with an airbag at 1000 km/h isn’t going to be safe, nor is it going to do much to your overall speed.

          • cosmicbuzz

            Try using a tube yourself: stuck piston like object A in one side, try to push a piston like object B far from another end as fast and as hard as you can, B will push A forward even though it is far away, A and B will not collide hard, because it is very hard to compress the air to 0 between them.

            Air bag or an air stifler might or might not work, just to play with an idea because it does have the effect of stifling air flow and cause an object very far away to slow down. I do not fall in love with any thing, even though it is mine.

          • Alon Levy

            The tube isn’t quite a piston – the cross-sectional area of the capsule is less than half that of the tube (see PDF-pp. 27-28).

          • cosmicbuzz

            So modify the design so it is more fitting like a piston, with the air intake to control air to serve as a break or faster than air column, and also as a way to push the pod in front to reduce collision. Adjustable piston effect is an important safety and control feature in a tube. One interesting effect is that if my pod air intake is shut and is reversed slowed down by propulsion backward, the piston effect will also drag and slow down the pod (air intake is shut too) in front of me though he is far away and not in the propulsion section. The challenge is that the whole system and communication need to work together.

            This is getting more fun 😉

          • Joey

            If you’re air braking you still have issues with heat dissipation, but it barely matters. It’s easy to decelerate the pod quickly simply using linear motors, but it’s difficult to do so without injuring the passengers inside.

          • Jesse

            At speeds above sonic this effect does not apply. You get no force acting from the piston on the object until the sonic shock wave slams into the object in front… In a tube there is no easy way for the shock wave to dissipate either. That and an debris in the tube would have an effect similar to a rifle bullet.

          • cosmicbuzz

            Remember the key point, the air column moves below sonic speed. The pod move relative to air column below sonic speed. The combined speed is above sonic speed. When 2 pods both travel below sonic speed relative to air column, they can affect each other if they activate piston effect to achieve safety distance.

          • Alon Levy

            What piston effect? The air column’s not obstructed enough for it.

            But let’s say it is. If the distance between two capsules is halved, there’s 100 Pa overpressure. That’s 100 N/m^2, which given capsule cross-sectional area is 400 N for the bigger version. The weight is 27,000 kg, so the acceleration is 0.015 m/s^2, i.e. trivial. For the smaller version, make it 140 N and 15,000 kg, so 0.009 m/s^2. It’s not going to splatter the passengers. On the contrary, it won’t do enough to slow a capsule down. If a capsule crashes and the one behind it relies only on a piston effect to brake, then the braking capsule will not feel a force noticeable by passengers until perhaps the last 2 seconds, during which acceleration will grow from about 0.25 m/s^2 to a large power of 2 (not hard to bound it from below by a billion m/s^2), ejecting the capsule backward at relativistic speeds. This is not survivable to anyone in the capsule affected or in any capsule behind it.

          • Joey

            Well, the capsule might stop, but it’ll be partially melted and the passengers inside will be splattered against the front wall due to the acceleration.

          • cosmicbuzz

            With piston effect, the air column behind my pod (actually the slowing pod behind me) will help drag me down too. Provided the electronic auto-communication is good.

            Leakage can be dealt with and do not cause death. Only terrorism will cause mass death, it is about how many 28/pod death. I don’t think other factor can cause death within seconds.

            Activating piston effect is only one of the breaking option. Splattering injury is better than death.

            Again, terrorist is better off blowing something else and cause a lot more death. The fact that there aren’t mass terror death in past 12 years tells it is not a big deal.

          • Joey

            Emergency stops need to be possible regardless of the specific terrorist threat (even in the absence of one). I hate to invoke Murphy’s law, but the truth is that in any complex mechanical system, you can’t rely on all of the components to work 100% of the time. Switches fail to move fully, signaling systems experience computer glitches – these events are extremely rare but if not accounted for the damage caused can be catastrophic. So a safe stopping distance has to be maintained between vehicles, and the system cannot be considered safe if an emergency stop would cause injuries. So unless you are proposing roller-coaster style restraints, 30 second headways are not safe.

          • cosmicbuzz

            If there is no terrorist blowing holes in the strong tube that cause a dead stoppage at one point within seconds, other type of problem will have the tube mostly intact within a minute. All pods slow down yet still stop over a long distance. The activated piston effect ensures no 2 pod can collide hard, that is what matters, not the hard stopping distance.

          • Joey

            You demonstrate a clear lack of understanding of the concept of safety.

          • cosmicbuzz

            “You demonstrate a clear lack of understanding of the concept of safety.”

            Joey, I am disappointed that you resort to personal attack. I will not downgrade myself.

            The non-personal matter is: “The activated piston effect ensures no 2 pod can collide hard”. That will achieve what you said “So a safe stopping distance has to be maintained between vehicles”.

          • Alon Levy

            Go ahead, solve the differential equation for piston action,

            s'' = -\frac{10000}{10000 - s}

            Here, 10000 meters is the distance required to maintain 30-second headways at the desired speed. The initial velocity represents the initial closing speed, and by the brick wall rule it should be the full speed of a capsule, 338 m/s.

            It doesn’t have an exact solution and Wolfram Alpha gives me a timeout error, but there are easy lower bounds that can be proven for what the maximum velocity will be and what the acceleration will be. They’re relativistic. I think I’ve managed to convince myself the peak acceleration is at least a billion m/s. Of course it’s not going to actually be relativistic – the air pressure would cause either the tube or the capsule to burst first.

            And all this assumes there’s a piston action, which there isn’t.

          • Joey

            Joey, I am disappointed that you resort to personal attack. I will not downgrade myself.

            I’m sorry, but you keep ignoring what I’m saying. It doesn’t matter how you decelerate. Achieving fast deceleration is easy. The problem is that there are passengers inside the pod which are not nearly as capable of surviving sudden and fast deceleration as the pod itself. And emergency stops have to be safe for the passengers.

          • Jesse

            The air column will be accelerated by the capsule, and then decelerated by the far larger tube. The tube wall imposes resistance to flow and is stationary. Probably the net air velocity would be a hundred miles per hour or so. Of course each acceleration cycle will add heat, and A/C won’t work on the capsules because you don’t have enough air to cool the A/C coils…

          • Joey

            Creating heat is easy, which is what you need in space. Taking heat away is hard – you can’t just make it disappear – you have to pump it somewhere, and you usually generate more heat in the process. Themoelectrics can convert some temperature differential into electricity but only very little and they’re still a long way from being commercially useful.

  42. DaveM

    You seem to get the idea. Riding in the vacuum will carry the same risks attendant with space travel. But you also seem to think each of these hundreds and hundreds of small capsules can be built with the same budget for construction and maintenance and with the same attention to detail as a single rocket capsule? Remember, those space capsules are not used dozens of times a day and the maintenance budget is not funded by $100,000 fares.

  43. Ben Brockert

    The most interesting part of this article is in the last few paragraphs where you completely discount the possibility of disruption in the mass transit market. You could have written the same article in the 1920s, explaining how cars, horses, and trains were the only efficient way to travel, and that the idea of an airline is an elaborate lie.

    • Alon Levy

      Airplanes were a rapidly growing technology already, and were based on decades of experiments with gliders. Hyperloop isn’t; it’s a new propulsion technology, but like maglev, it’s basically a train by another name and should be treated as such.

      In the 1920s, a similar article would note that airplanes are an interesting growing technology, with rapid pace of advancement in speed, capacity, and safety, but at least for the foreseeable future ground and sea transportation would continue to dominate. Conversely, the same article would talk about trains as a mature technology with a slow pace of advancement, such that future investment should be into incremental improvements such as replacing steam power with electric power, building cutoffs of slow lines, quadrupling bottlenecks, and running urban lines with subway-competitive fares and frequencies.

    • nick s

      You could have written the same article in the 1920s, explaining how cars–

      Let me stop you there. The car was certainly not an efficient way to travel long inter-city distances in the 1920s; take a look at archive footage and you’ll see Model Ts negotiating rutted mudpits.


      The disruptive force there was the road, and specifically, massive investment in paving dirt tracks, building parkways and freeways, and levelling poor urban communities.

      • Nathanael

        Interestingly, the road-paving program was initially promoted and funded by bicyclists. (Autos are *far* better than bicycles at handling dirt and gravel roads.)

        • Richard Gadsden

          As an aside, that’s considerably more true of 1920s bikes than 2010s bikes. Full-suspension off-road (“Mountain” or “cyclocross”) bikes deal a lot better with poor surfaces than traditional road bikes.

          Of course, the suspension technologies they move to make ride quality acceptable were invented for cars.

      • Nathanael

        It’s also worth noting that there was a big debate in the 1910s, which you can read in the yearly “World Almanacs”, if you like, over which sort of automobile would win out: electric or steam.

        Gasoline wasn’t even in the running. Gasoline ended up being popular because it was *very cheap*, being a waste byproduct of kerosene production. (Why was kerosene production such a big deal? Because there was no more whale oil, and electrification was still in its infancy.)

        This is an interesting example of path dependency. If widespread rural electrification had been built in the 1900s instead of the 1930s, I expect we would all have been driving electric cars from then until the present day. (Kerosene production would have collapsed, removing the cheap gasoline from the market.)

        To go further back, if the electric generator had been invented 30 years earlier than it actually was, steam engines would never have been successful either. The electric motor *had already been invented* but there was no way to generate electricity for it other than building batteries (not rechargable, because no generator, remember).

  44. Dan

    Interesting points. Still, I don’t think anyone’s addressed a question that comes up before Elon even proposed his idea: I travel from LA->Bay Area at least once-a-month. My flights are usually $59 and take 1 hour. There are multiple flights each hour (and I get to choose SF, San Jose, or Oakland). Why would I ever pay over $100 for a 3-hour trip?

    It might be useful for people who live in the rural areas, but I don’t see anyone using HSR for a roundtrip from SFLA. I guess unless they’re afraid of flying.

    (Also, the TSA seems to be planning to screen all sorts of events and trips. I imagine within 10 years that they’ll be screening HSR trips too.)

    • zog

      Your 1 hour figure does not include the time getting to and from the airport, which is at least 1/2 hour each way, assuming no traffic jam on the 101 to downtown SF or the 110 to downtown LA (hee hee hee!). Nor does it include the 1 hour or so you have to budget for the checkin and the security check.

      In contrast, the CA HSR will have terminals in downtown SF and LA, and if the experience is anything like HSR in Europe or Japan, it’s literally three minutes from the station entrance to getting on the train. OK, five minutes, if you had forgotten to buy tickets at home.

    • Steve S.

      a. What’s the “real” time? 59 mins. is only the flight time; as has already been pointed out, the intermediate “last mile” trips from origin to port and port to terminus are among the biggest time-sucks in airline travel. Also security theater, which absolutely needs to be abolished. I’ll bet you this is indeed closer to three hours.

      b. The TSA really, really, really needs to just go away. It increases nothing more than the perception of security at the cost of efficiency (as in: it takes too long).

      c. The Hyperloop propulsion tech looks to be optimal for airline-competitive very-long-distance runs (as in: between New York and Chicago, New York and LA, New York and London, etc.) That said, at its speeds capacity by short, frequent capsules seems impossible; the proposal already has excessively short headways. And there are plenty of problems of branches, capacity, etc., to be solved before this high concept is anywhere near ready for the real world. By that time CAHSR, overwrought as it is, will be well along in implementation, which of course is a bad case of Reality contra Musk.

      • Richard Gadsden

        NY-Chicago is only 1275km, a little short for Hyperloop / maglev, because it’s (just) inside the capacity of HSR. The longest continuous stretch of HS track in Europe is Amsterdam-Marseille (c. 1240km), which is about six hours – the shortest real-world journey is 6:57, with a change in Brussels and about a dozen stops; a direct service with no more than two/three stops would be around six.

        Six hours from Union Station to Penn Station is pretty tempting. The flight is getting on for five hours for centre-to-centre (an hour to get to O’Hare, another one to check in and fight security theater, a two-hour flight, and an hour back into New York from JFK or LaGuardia)

        • Alon Levy

          Six hours is tempting, but the majority of people would still fly. I’m basing this on Paris-Nice – the TGV does the trip in 5:35 and has a 31% share of the air/rail market. The main use of such a line would be for the intermediate trips: New York-Cleveland, Philadelphia-Cleveland, Pittsburgh-Chicago, maybe Philadelphia-Chicago.

          • Joey

            And about zero hours with teleportation.

            It’s not inconceivable that we might look at building maglev between NY and Chicago some time in the next few decades. That could make it competitive with flying. But anything in evacuated tubes is going to cost even more and isn’t going to be feasible for a while and won’t justify the additional investment for the foreseeable future for a distance like NY-Chicago.

          • Joey

            We have already gone over why it’s not 10x cheaper. There is no basis for Musk’s numbers.

  45. Jonathan

    “There is no redeeming feature of Hyperloop. Small things can possibly be fixed; the cost problems, the locations of the stations, and the passenger comfort issues given cost constraints can’t.”

    I can’t really respond to your technical arguments. All I can do is point to Musk’s records of insisting that these kinds of cost reductions are possible, as he did with his rocket for crissake. And all I hear is a bunch of nay-saying about how these cost problems are deal breakers. And that might have been credible if you hadn’t also insisted that passenger comfort was a dealbreaker. Surely an innovative mind can come up with a way to let people sit comfortably in these capsules for a half an hour!

    • Alon Levy

      An innovative mind can’t make motion sickness disappear, just like it can’t create reactionless drives. That’s why technical knowledge is so important. Someone needs to tell the wheel reinventors that their ideas are quarter-baked. Someone needs to do the sanity checks on civil infrastructure costs, instead of let someone who’s trying to make money on cars anchor their expectations of cost (“if it’s just three times as expensive it’s still a bargain!” – no, it won’t be three times as expensive, that’s still $15 million per km for elevated infrastructure).

      • cosmicbuzz


        If $15mil/km for the tube, then LA-SF 600km X $15mil/km <$10Billion, that is cheaper than HSR! That solve the biggest cost.

        • Alon Levy

          Yeah, that’s still a fraction of how much elevated construction usually costs. I brought it up specifically as an outlandishly low cost; Musk’s $5 million/km bit is a psychological trick.

          And that’s not taking tunnels, stations, and urban approaches into account.

    • Nathanael

      “All I can do is point to Musk’s records of insisting that these kinds of cost reductions are possible, as he did with his rocket for crissake. ”

      He was wrong about most of these claims. Every project he’s done for SpaceX, Tesla, and even SolarCity, has come in costing more than he thought it would. They were only off by percentages, not by factors of 10 like this one, but still, he DOES have a track record.

      I eventually found out where the actual cost reductions came from in the SpaceX rocket design. Most rockets were designed prior to modern electronics. They use complex electromechanical control systems. Eliminating these in favor of computer control saves a bundle, and that’s basically the cost savings, all of it.

  46. Digital Cosmology (@DCosmology)

    You have not answered my questions. You treated the hyperloop as a regular train which is wrong. The capsule does not move on a track but IN A TUBE. Thus, the track plane acceleration of the capsule is of no concern. Then by aligning the passenger seat along the direction of the lateral force the affect is minimized. You wrote:

    “This only drops to 5 m/s^2 after perfectly canting the track, converting the downward 9.8 m/s^2 gravity and the sideways acceleration into a single 14.8 m/s^2 acceleration vector downward in the plane of the capsule floor, or 5 m/s^2 more than passengers are used to.”

    You cannot add vectors like that. You CANNOT do: 9.8 m/s^2 + 5 m/s^2 = 14.8 m/s^2

    these are vectors and you must use a proper coordinate system and the lateral force angle. The correct result for the resultant vector magnitude is 11.1m /s^2. Also, the component perpendicular to the track is given by g x cosF, where F is the angle. Assuming small F then the result is approximately equal to g.

    Therefore, there are no acceleration concerns because your analysis was based on the wrong method of adding vectors. There may be other considerations that make the project not realistic but not any based on accelerations. The ride will be fine and with precise control, as I will explain in more detail in my blog today, any accelebration effects can be minimized to below those experienced by airplanes or even HSR. So I hope you will concede.

    • Alon Levy

      I know how to add vectors. I’m not that bad at applied math.

      If you look at the curve radius standards that I quoted, the acceleration in the horizontal plane is 11.1 m/s^2. The resultant vector magnitude is then 14.8 m/s^2, which differs from normal gravity by 5 m/s^2. This is not below what’s experienced on HSR. It’s several times what’s experienced on HSR, actually – upward and downward acceleration tops at 0.67 m/s^2, lateral acceleration not compensated by tilting or superelevation tops at about 0.83 m/s^2. (Tilting and superelevation at the levels done on HSR produce a negligible downward component, theoretically at most 0.14 m/s^2 and de facto 0.11 m/s^2.) The 5 m/s^2 figure is not the lateral acceleration, but the residual. I can’t find perfectly reliable numbers for commercial airplane acceleration, but the ones I have dug up after a bit of Googling are a bit less than that, at most 3 m/s^2 or a bit more.

      • Digital Cosmology (@DCosmology)

        Then, your statement below is not worded correctly. Please check it out:

        “This only drops to 5 m/s^2 after perfectly canting the track, converting the downward 9.8 m/s^2 gravity and the sideways acceleration into a single 14.8 m/s^2 acceleration vector downward in the plane of the capsule floor, or 5 m/s^2 more than passengers are used to.”

        This is the maximum, not after canting perfectly the track. It just happens that the wrong addition produces the maximum vector resultant! However, this can be minimized by banking. I argue that there are no serious acceleration (g-force) concerns in the project. Your other considerations are excellent and things I cannot judge due to my complete lack of knowledge in that area. (I worked with high speed linear motors in robotics).

        • Alon Levy

          The standards explicitly call for 5 m/s^2 of additional acceleration felt by passengers, and the curve geometry standards seem to bear this out: 480 km/h on a 1.6 km curve induces a centrifugal force of 11.1 m/s^2, which combines with 9.8 m/s^2 of gravity to form a vector of magnitude 14.8 m/s^2. Banking of course doesn’t change the magnitude, just the direction. At the low lateral acceleration rates of regular trains, changing the direction almost eliminates the difference with normal gravitational acceleration, but when lateral acceleration is stronger than gravity, banking can merely change the additional force passengers feel from 1.1 g sideways to 0.5 g downward.

          • Digital Cosmology (@DCosmology)

            I agree but you stil do not spot the error in your statement

            ““This only drops to 5 m/s^2 after perfectly canting the track, converting the downward 9.8 m/s^2 gravity and the sideways acceleration into a single 14.8 m/s^2 acceleration vector downward in the plane of the capsule floor, or 5 m/s^2 more than passengers are used to.”

            If it drops to 5m/s^2 then the resultant is 11.1 m/s^2 not 14.8 m/s^2

          • Alon Levy

            The resultant is 14.8 m/s^2. The number 5 m/s^2 is the magnitude of the difference of the resultant vector with the standard gravity vector. This is what’s called G-force – in this case it’s about 1.5 G, or 0.5 G, depending on conventions. When I say “drops to 5 m/s^2” what I mean is that canting reduces the magnitude of this difference vector to 5 m/s^2.

    • Joey

      Seriously read Alon’s post all the way through. If you had you would know that Alon has accounted for what you are saying. The acceleration in the horizontal plane is 11.1 m/s for the curves Musk proposes. The magnitude of acceleration experienced by the passengers is 14.8 m/s.

        • Joey

          With no superelevation you experience 9.8 m/s downward and 11.1 m/s horizontally. If you tilt all the way into the curve you experience 14.8 m/s downward. The only other place you can be is somewhere in between

          • Digital Cosmology (@DCosmology)

            If you tilt all the way into the curve you have a component of centrifugal force that reduces gravity and a much smaller lateral acceleration.

            Hey, I am not saying this is easy by the way, It is rollercoaster technology still.

          • Joey

            Gravity and centrifugal acceleration are perpendicular regardless. You can’t avoid that in a curve which is parallel to the ground. And rotating your coordinate system isn’t going to change it either. Draw a free body diagram. Let’s phrase the problem in a different way. The net acceleration is 14.8 m/s. Find an angle x such that (14.8 m/s)*cos(x) is approximately 9.8 m/s and (14 m/s)*sin(x) is approximately zero. These represent the vertical and horizontal forces felt by the passengers, with x measured relative to the direction of net acceleration.

          • Joey

            Actually we all need to clarify the physics terminology we are using. The net acceleration is 11.1 m/s parallel to the ground. The force which the vehicle exerts on the passenger must cancel gravity, which is invariably perpendicular to the ground, as well as provide this centripetal acceleration horizontal to the ground. The magnitude of this force is still 14.8 m/s.

          • Joey

            Buh. I said the magnitude of force is acceleration. But the mass of the passenger is irrelevant in this case, so you know what I mean.

  47. Eric

    There is a belief within American media that a successful person can succeed at anything. He (and it’s invariably he) is omnicompetent, … The people who are already doing the same thing are peons and their opinions are to be discounted, since they are biased and he never is.

    Well, he is more competent at this field than the journalists writing about him. And try asking Richard Mlynarik about the people already doing the same thing. He’ll tell you they ARE biased peons whose opinions are to be discounted.

    • Alon Levy

      Yeah. And Richard takes great pains to learn what rail engineers in Switzerland do. Given American transportation inefficiency, you could analogize the American transportation system to Soviet industry. There’s a mountain of difference between a Soviet planner who sees that the Western bloc is more efficient at producing something and proposes reforms to copy Western technology and manufacturing practices and a Soviet planner who tries to reinvent something and poo-poohs existing Western technology as old and inferior to his inventions.

  48. Emily

    Many good points, in the article and comments. My question, along the lines of Dan’s comment – why is it so important to get to LA from SF?

    My further comment is that for safety and speed, nothing beats the ‘Net. Set up a web conference from SF and I’m in LA in seconds. True, I can’t drive around LA (feature) or go out to lunch. And of course that doesn’t address the real need to be in one city or the other, nor the need for innovation re: mass transit.

    In fact, what Hyperloop reminds me of is the science in Star Trek – outlandish in the present, perhaps conceivable in the future. The proposal perhaps best serves to foster, rather than function as, innovation.

  49. aj

    Had to stop reading fairly early on due to all the snark. Seriously, rewrite your intro, making a living selling cars? You must be very wealthy to be so dismissive.

  50. Pingback: Hyperloop’s Real Problem | lessbull.com
  51. Pingback: The Hyperloop Idea May Fit in the Matrix | Digital Cosmology Blog
    • Joey

      You’re still getting the basic physics wrong. The acceleration that the vehicle exerts on the passengers still has to have a magnitude of 14.8 m/s in order to cancel gravity and provide centripetal acceleration parallel to the ground. Again, I implore you to draw a free body diagram of the forces on the passengers. Rotating your coordinate system won’t change the vectors at all – it will only change how much is felt along each axis.

      • Digital Cosmology (@DCosmology)

        First of all, the centripetal acceleration is not directed “parallel to the ground” but towards an imaginary center of rotation, wherever it is located in space. You have the basic physics wrong. If you rotate a bucket with water tied to a string above your head, the centripetal acceleration, which is caused by the changes of tangential velocity towards the center of rotation, is directed towards that center of rotation.

        Now, if you get this right, we can talk about the rest.

        • Joey

          The centripetal acceleration is parallel to the ground unless the curve is not parallel to the ground, in which case you’d have to deal with a significant elevation change over the length of the curve.

        • Joey

          In other words, the net force must be up or down otherwise you’re going to start accelerating up or down.

    • Ummon

      Take it from a someone who majored in aerospace physics: you’re flat out wrong. The hyperloop calls for 11.1 m/s in the horizontal plane, in addition to the existing 9.8 m/s of vertical gravity. By the pythagorean theorem, the magnitude of the total acceleration is 14.8 m/s. Banking the train will be nice, as then people won’t feel any sideways acceleration, but they’ll still feel 14.8 m/s in their vertical direction, which is far too much.

      • Digital Cosmology (@DCosmology)

        If you bank the train, the centripetal force that is directed towards the center of curvature will be in an angle more than 90 degrees with gravitational acceleration. A resolved component of the centrifugal force on the passenger along the axis of gravitational force reduces the effect of gravity, resulting in a smaller net effect. Think of it this way: if the train is banked completely so that the centrifugal is along the direction of gravity, you can even get free-fall conditions at suitable speeds (i.e. when the centrifugal acceleration cancels gravity). In a hyperloop, nobody will understand anything, actually, it will be a pleasant feeling losing some of the weight.

        • Ummon

          Banking cannot change the direction of the curvature. In the Earth-frame of reference, the acceleration due to horizontal curvature will perpendicular to the acceleration due to gravity. Bank angle merely changes the direction of the total acceleration in the passenger’s frame of reference.

          Also, your claim that it would be a pleasant feeling to lose some of the weight is quite laughable. There is a reason people tend to throw up on Roller Coaster rides.

        • Digital Cosmology (@DCosmology)

          Right. And the 11.1 m/s^2 is without banking, i.e. parallel to the ground. They say explicitly in the project report that banking can reduce that. Actually, in a tube you can even bank the rails to an angle more than 90 degrees because you have no serious derailment issues. The centrifugal is no more parallel to the ground and this is what those guys who claim they know physics do not understand. If it is not parallel to the ground the resultant g-force is much smaller. Besides I think that g-force impact on humans is more psychological than physical. It is more because of fear than anything else and it also has to do with eye movement when focusing on objects outside a vehicle. Inside a tube these are not the case. It takes many Gs to start affecting blood circulation.

          • Joey

            If the net force is not parallel to the ground you are going to start accelerating up or down. Again, I implore you to draw a free body diagram.

          • Nathanael

            You do not understand motion sickness, “Digital Cosmology”. I suggest you do some research and learn about it. In short, people are far worse off inside a tube with no point of visual reference.

  52. Pingback: Here’s an idea, South Africa | Johan Fourie's blog
  53. cosmicbuzz

    Thanks Alon Levy for starting this in depth brainstorm, and many capable peers that contributed to either sides, before massive open source peer reviews start. The brainstorm hammer out high priority problems and solutions. I believe if this is a larger, much better working peer group, a large percentage of peers will be convinced that many solutions to the problems are highly feasible, and will only get substantially better after full dedication. Here is my own summary of high priorities to mark my own milestone. It is only 3 days after the announcement. Knowledge is gratifying 🙂

    * Cost of civil engineering of 600km tubes:
    Not including cost of material consumption, it is purely labor (man-dates) and machine amortization; it will be the most critical portion of the project. For total cost of $15B tube route, the current visualized estimate of assembling 30 meter section of 1 pylon and 2 tubes, is about $0.5million. This is a number with no material consumption (I consider high). I can visualize that it will be much cheaper after full improvement. (The pylon can be a pole, triangle, or spanning ‘n’ shape)

    That is ~20,000 unit sections of work, each unit section is 2 tube (30 meter) unit assembly. It is massive repetition not seen in other viaduct assembly. It surely begs higher efficiency. What likely will happen is that the open source/contractors will fully optimize the unit section assembly process, and develop assembly machines that will do most of the precision assembly work. It will be a race of how many shorter days man and machine can assemble a unit section. I even think 4 tubes might be feasible.

    Visualize the steps: erect pylon, lift tube, then machine precision fit 2 tubes and joining materials. It is simple by comparison to other viaduct assembly. A viaduct that require support for heavy train/derailment and track fitting is multitude more costly, how many more steps/materials are involved?

    * Cost of ROW:
    In middle of freeway or beside it. Some sections high above ground, some dig into earth to maximize radii.

    * Safety:
    There are many solutions to solve safety: seat belt, backward facing seat, strong movable/huggable pillow in front of chest, airbag in front of seat, maintain distance between 2 pods, friction-based break, linear motor break, parachute, activate piston effect (reduce/block air flow), air blockers inside tube, multiple air tanks for breathing, injury not death.

    If terrorist do blow a hole in the tube, use solution to reduce death, though there might be injury. Worst case <28 death in first pod, and few in second pod (how will it happen if backward face seating and with airbag?). It is no more damaging than a bomb in subway.

    * Jerks and G-force:
    Oscillating passenger compartment inside pod shell will eliminate side way jerks and ensure G is downward for comfort. Front and back compartment spring reduce forward/backward jerks.

    Reclining seat/high knee greatly offset G force's effect on blood flow to the head. Ben has a very good write up on G-force and the small percentage of time for acceleration. https://pedestrianobservations.wordpress.com/2013/08/13/loopy-ideas-are-fine-if-youre-an-entrepreneur/#comment-10367

    If I travel from SF-LA and enter I5, from the video screen I see the far away mountain before LA, my pod accelerate like roller coaster, zoom past cars on the freeway and planes in the sky. Cool! I can shoot down the planes? or tease their avatars, or shoot at other pods, or dodge morphable alien birds flying against my pod. … Damn it, we reach and slow down near the mountain and enter death star flight episode. 20 minute is too short to win the title in central valley. I will beat the guys next time I ride again. Heck, it is just 20 bucks a ride. …. What? G force? I didn't notice it.

    Don't have time to summarize many other lower priority items. I will next search for open source forum for hyperloop.

    The google founders are outlandish and rich, and can join the fun. They can modify Gmap streetview vans to plot the whole 3D terrain model. Plenty of free source people can share and simulate the whole 3d or real scaled-down ride and all kinds of faults. (Use railguns to shoot 3 small pods in tube with running low pressure airs, pods record the data.) Using 3D printers, people can build all kinds of tube assembly robots and compete in contests….. My 11 year old son read hyperloop alongside me. He might do something relevant.

    • cosmicbuzz

      30 minute near sonic travel from SF to LA, which is feasible and green, that is life style changing future. (half sonic air + half sonic pod = near sonic travel)

      Politically and culturally, the open source is radically more resourceful.

      It is a fact that for many years it was so hard for voters to find appropriate materials to understand why HSR is so expensive. In Hyperloop open source, the voters will get plenty of facts, examine prototypes, contribute (freely), and support. Even if it is not built in CA, it will be built somewhere else futuristic (China?).

      Establishments always have hard time understanding how open source people rapidly and massively evolve high efficiency technology without delay by big institutions.

      If $70B HSR is delayed for another 10 years waiting for better technology, voters don’t mind the $70B and huge debt interests off their back. We have been flying and driving and got by just fine.

      At the meantime, I will pay particular attention to open source development of the highly efficient robots that precisely assemble 1 pylon and 2 tubes per 30 meter, repeating 20,000 times. The robots will solve the biggest cost that make it feasible.

      • Joey

        The robots will be even more awesome and efficient if we put rockets and lasers on them. And SpaceX already develops space rockets so building small ones to put on the robots should cost almost nothing right? Right?

        • cosmicbuzz

          For the 2 major summaries I wrote above, one on cost of hyperloop, one on politics, I received no criticism, except Joey’s sarcasm. (I have the advantage of having my 11yr son alongside me to keep me sane.)

          With absolutely no prior knowledge, this week I understand that CAHSR debt of $7000 per family can bankrupt California. Considering the current cost, plus magical material technology (how about graphene? ;-)) and other convergent technology improving rapidly, it truly is worthwhile to wait more years.

          Adding up other few summary comments (https://pedestrianobservations.wordpress.com/2013/08/13/loopy-ideas-are-fine-if-youre-an-entrepreneur/#comment-10451), I guess it pretty much conclude most major threads of debates stem from Alon’s post. Hopefully I can find a good open source community for hyperloop soon. The innovations I made here maybe able to prevent patents and keep new technology free for open source projects.

          After 4 days of fun brainstorming since Hyperloop announcement, thanks all and have a good weekend!

          • Alon Levy

            For all the talk about “convergent technology improving rapidly,” civil engineering has no gamechangers happening right now. That’s why I made that point about mature technologies in the original post. There’s an enormous market and an enormous set of engineers all over the world working on this, such that change has to be incremental and come from applying techniques used elsewhere. You can very accurately estimate costs by looking at the costs of other viaduct structures – and the global trend is up, not down, with most cities spending more today per kilometer than they did 10 or 20 years ago. (No, the weight isn’t a major cost saver; for easily accessible cost numbers of monorails that turn out to be as expensive as heavier els, look at the Moscow Monorail, KL Monorail, and Chongqing Line 3.)

          • cosmicbuzz

            As someone else pointed out, you are disingenuous. When somebody make some important points, you chose to respond to some but ignore the more important points, like my above “* Cost of civil engineering of 600km tubes”. That is not honest debate. You said “civil engineering has no gamechangers happening right now”. The topic is not about “right now”. Before airplane, model T, iphone, etc., establishments only talked about “right now” and “references”, then later were run over by the future.

            None of the current references use robots in a big way, and none of them do massive (20,000), repetitive unit work (30meter section). They use human like busy worker ants that eat up most of the money, and treat each pylon/tube as a unique branch to tackle. It surely calls for a revolution, though not “right now”, but likely will happen soon because of powerful proponents.

            Imagine you are on a helicopter looking down, the human worker ants dig a big hole that can bury them, move machine to firm it up, put down the huge foundation slap, crane erect the huge pylon, adjust the angle, crane up the huge tube, align them. Do it so slowly to avoid being crushed, repeat 20,000 times. The worst of all, the guys who control these workers make calls in a recliner and get and bribe lots of money without a sweat. …. It looks so stupid.

            The improved crane shall be like the arms of a giant, the robots (don’t look like humanoid) are the sensors and fingers of the giant to do all the assembly and better alignment. Human simply install sensors correctly, and get out of the way of the giant. Repeat 20,000 times. Oh, we pay the robots very cheaply, just give it electricity and it will work day and night. More robots are a lot more complicated that these robots, which just have bigger muscles. I am sure open source and best companies can nail this in few years. They might even be able to do 4 tubes cheaply. As a citizen, I can search for tons of easily understood open information.

            The technology will rescue my family from $7000+ debt. Instead pay for my son’s college that he will pay back a lot more in tax. When I want to see his free flying pod competition, I can take 1.5hr end-to-end travel via Hyperloop to visit him in UCLA, not the 3.3hr end-to-end via HSR.

            Here is the excerpt of the important points in my above comment that you chose not to respond:
            “* Cost of civil engineering of 600km tubes:
            Not including cost of material consumption, it is purely labor (man-dates) and machine amortization; it will be the most critical portion of the project. For total cost of $15B tube route, the current visualized estimate of assembling 30 meter section of 1 pylon and 2 tubes, is about $0.5million. This is a number with no material consumption (I consider high). I can visualize that it will be much cheaper after full improvement. (The pylon can be a pole, triangle, or spanning ‘n’ shape)
            That is ~20,000 unit sections of work, each unit section is 2 tube (30 meter) unit assembly. It is massive repetition not seen in other viaduct assembly. It surely begs higher efficiency. What likely will happen is that the open source/contractors will fully optimize the unit section assembly process, and develop assembly machines that will do most of the precision assembly work. It will be a race of how many shorter days man and machine can assemble a unit section. I even think 4 tubes might be feasible.
            Visualize the steps: erect pylon, lift tube, then machine precision fit 2 tubes and joining materials. It is simple by comparison to other viaduct assembly. A viaduct that require support for heavy train/derailment and track fitting is multitude more costly, how many more steps/materials are involved?

          • Alon Levy

            People do in fact build very long repetitive viaducts. “I can visualize X” doesn’t mean X is actually feasible. I can visualize building streetcar tracks with a 100-person team working overnight to build a single-track block’s worth, which works out to $375,000 per single track-km in labor costs. Streetcar tracks do not actually cost $375,000 per single track-km – try $15,000,000.

            The issue with robot construction is what I was talking about in the part of the post about proving too much. The construction industry is huge. If Musk found a way to build things super-cheaply with robots, he also found a way to build houses with robots, and roads, and conventional rail, and bridges, and water works.

          • Adirondacker12800

            ” Oh, we pay the robots very cheaply, just give it electricity and it will work day and night. ”

            it won’t care if it’s building for tubes or tracks or paved lanes.
            Some rainy afternoon when you don’t have anything better to do go wander the archives for Popular Science or Popular Mechanics from the 60s and 70s. We were all going to whisking between cities on maglev trains in four or five years.

          • Nathanael

            “The issue with robot construction is what I was talking about in the part of the post about proving too much. The construction industry is huge. If Musk found a way to build things super-cheaply with robots, he also found a way to build houses with robots, and roads, and conventional rail, and bridges, and water works.”

            Yep. In fact, there is a known way to build long elevated tracks with pre-fabricated segments, and it *is* cheaper than building bridges in place, which is why it was used (for instance) on large hunks of Seattle’s Central Link. There is a known way to plant pylons automatically in some places, and it *is* cheaper than building pylons in place, *if your geology is suitable for it*, which it usually isn’t. There’s a lot to be said for using these techniques, but we know how much they save, and they aren’t going to save that much.

          • cosmicbuzz

            After I pressed, you finally responded to one of my important point, the robot. Thank you for responding.

            Your saying: “I can visualize X” “found a way to build houses with robots, and roads, and conventional rail, and bridges, and water works”

            Your arguments obviously show that you don’t know (or don’t use) creative and analytic visualization. How will a robot visualize? It senses the sensors on the ground, the foundation slab, pylon, tube, and join/alignment pieces. The number of sensors can be estimated, MUCH less than other complex robotic systems. How much differences are there between the geometric sensor points on a Pylon and on a plant of wood? Not much. How about between one pylon and a hundred planks of wood for a house? So the more sensors are required for number of objects, the more complex the robotic system will be. “roads, and conventional rail (track and slabs and other geometric pieces), and bridges, and water works” are ignorant references.

            The main difference of such robots from others is that they use crane power and their own power to manipulate very heavy, yet simple objects. The joining and alignment work are the most complex part. Yet such robots are vastly simpler than other advanced robots that are smaller. They are just enlarged robots.

            The expensive robot is worthy for the 20,000 repetition, it will later revolutionize construction business in a gradual way or a fast way.

            Pylon and tubes are cheap concrete and steel that cost ~$120k in mass production. In your references, labors to construct a 30 meter section are ~$0.7million to $2 million. For 20,000 times, replacing repetitive labor with machine is a golden opportunity to save and make huge money. If I have found such company hitting the sweet spot between robotics and civil engineering, I wound be very interested in it.

            All the most successful tech companies in silicon valley have been through the stage of “proving too much”. Successful founders/leaders never invent everything, they inspire smarter people (around them) to do better than them. You can win arguments by rigidly reading Musk’s first draft, but rapidly evolving history will soon forget you because you intend not to contribute to it. Many open source people (including me) will argue to him and work out modifications, like those I made here.

      • Anon256

        You keep saying “open source”. I do not think it means what you think it means. http://opensource.org/docs/osd
        In particular it does not mean “Copyright Tesla Motors, Inc. All Rights Reserved” on a PDF with no source code (i.e. the engineering calculations that were presumably used to create the proposal and would be necessary to create serious derivative works).

  54. Steven Harrell

    I’ll say this for Musk: in one fell swoop he has converted me into a CAHSR supporter. CAHSR is suddenly conservative and old-fashioned. I like it.

    I get that a lot of serious transportation, planning and physics bloggers find Musk’s handwaving and mushy math frustrating; his swipes at HSR are infuriating, and his fawning fans are annoying. However…to the extent that this post indicts American (and only American) culture and media over this Musk business…please. We’ve always loved hucksters and visionaries. We find them entertaining. We’re entertained when they win, and we’re even more entertained when they fail. We’re probably not going to buy what they’re selling, but damned if we’re not going to drop everything and watch what happens next. I don’t think that’s unique to this particular corner of the planet, either.

    I don’t buy Musk’s argument. But If he’s right, he also doesn’t need my support: he should be able to find $6 Billion from private investors. He won’t need (and shouldn’t get) government subsidies or ROW.

    Besides, CAHSR isn’t planning to serve the Dublin-Sylmar market any time soon; and if hyperloop is up and running by then, even better! Because someone has got to ferry those hyperloop passengers between Transbay and Dublin (or Gilroy) and Fresno and Bakersfield and Palmdale and Sylmar and LAUS…and it’s gonna be CAHSR. Finally–as I know from reading this blog…big fan here–mass transit connections to airports aren’t necessarily good investments, and airports don’t really support TOD. But presumably a hyperloop station (even a relatively remote one) is going to support TOD and mass transit at least marginally better than the airport it might replace…and significantly better than the car trip that it might replace. In my book, that’s a win.

    And anyway, despite all of Musk’s insults to trains, science and modest journalism–I’m an American, so I’m planning to sit back and be entertained either way.

  55. Ashok

    I am amazed at the number of people who are commenting about this. Actually I wonder if there was a platform(kind of like Wikipedia), where people would comment and improve on the design, cost estimates, planning, critical comparison with other choices and even ask companies to give proposals for each aspect of the Project, it would help channel this awesome interest on this into a productive project.

    Blog: http://www.azuyo.com/blogs

    • Nathanael

      Hmm. Step one: replace the jet-powered tube with a pair of steel rails, and run conical-wheeled trains on them. This should solve a lot of the technical problems in one fell swoop, as well as massively increasing capacity. 😛

  56. Andrew Palfreyman

    I read the report and think that it has a good chance of success. It certainly puts the state-approved scheme to absolute shame, being cheaper to build (10x), faster (5x), cheaper ticket price (5x), safer, more energy-efficient, less environmentally demanding, quicker to build and quicker to board. I hope there are sufficient red faces in Sacramento this week (assuming that politicians are capable of experiencing shame) to kick them into action on scrapping that boondoggle they recently approved, which would end up costing not $68B, but more likely over $100B.

    The aerodynamic control and the thermal issues may be problematic, but I see no technical showstoppers here. So let’s get this show on the road!

    • Joey

      This is precisely why I think Musk was irresponsible in framing this report the way he did. If you don’t know any better, you might believe the cost estimates and construction timetable, even though both have no grounding in reality. If HSR gets defunded because of this, then we get nothing.

      • Andrew Palfreyman

        So a grounding in reality is what’s missing here and HSR is consequently stolen away? HSR was sold at $33B, is now $68B, and will be over $100B. It is a BOONDOGGLE. and I do not want it.

        Compared to TGV or MagLev, Hyperloop promises to be:

        – cheaper to build
        – travel speed (at least 3x faster)
        – cheaper fares
        – less waiting time to board
        – less environmental impact (e.g. noise, rights of way, etc.)
        – safer (e.g. independence from weather)
        – more energy-efficient
        – quicker to build

        Normally, we have to pick and choose and trade off such characteristics. But in this case, and assuming that the technology can be made to work, it’s a slam dunk for Hyperloop by any measure.

        • Joey

          The technology can’t be made to work. Not within the next few decades (and then, only if we research it aggressively). Please read Alon’s full post if you’re curious as to why. Musk makes up cost numbers, lies about the energy consumption of HSR, assumes roller coaster acceleration, and glosses over important alignment and safety issues which would, in reality, bring up costs significantly even if they weren’t artificially low to begin with. Those artificially low cost numbers also only account for construction to the edges of the SF and LA areas, meaning that you have the exact same last-mile problem as with air travel.

          That’s not to say that the current HSR project doesn’t have issues. A lot of poor engineering and routing choices have been made. If foreign examples (esp. Spain and Switzerland) were followed, the cost could easily be halved at no detriment to the project. But putting faith in an infeasible alternative simply guarantees that nothing gets built.

          • Andrew Palfreyman

            It has a good chance to be made to work. That has nothing to do with inaccurate costing and irrelevant remarks about the boondoggle. Half a gee acceleration for a very small percentage of the total trip time is acceptable. This thing is supposed to be fast, so that comes with the territory. Or you could take the bus.

            This is not about faith – it’s about kicking the tyres in public debate. However, even it costs $12B, if it succeeds in shutting down a $100B boondoggle, the public is well served and money has been saved.

          • Joey

            Money is saved because nothing gets built. The cost projections aren’t a factor of two off, they’re a factor of 10 off, since Musk has not proposed a new and revolutionary way of anchoring concrete pillars in the ground. And that’s ignoring the fact that the alignment tolerances for 1000 km/h running are insane and not achievable using any relatively cheap construction technology.

          • Andrew Palfreyman

            “.. the alignment tolerances for 1000 km/h running are insane and not achievable using any relatively cheap construction technology.” That’s a good point, although I automatically question the hyperbole. I’d like to take a closer look at that. Do you have any data to share?

          • Joey

            Musk doesn’t propose a way to keep the pod in horizontal alignment within the tube (a significant, challenging, and costly problem), but he does mention that the the pod would hover about a mm above the guideway. If one tube segment is anywhere close to a mm out of alignment with the next, it will result in a (fatal) crash with the floor of the tube. The proposal does not quantify how much restoring force the air bearing provides, so it’s difficult to say how much misalignment would cause a crash how quickly.

            To be fair this is a complicated fluid dynamics problem which can only be approximated with computer models. But the fact that this proposal doesn’t even address it should tell you something. We don’t have the technology to send objects though tubes at anywhere close to that speed, even if the objects don’t contain passengers. Getting this to work will require many years of research and prototyping, and many years after that to make it cheap.

            Of even more pressing concern is what happens if the structure is sent out of alignment after construction, which could happen as a result of any number of events, included but not limited to earthquakes and vehicles colliding with the support pillars. Again, the alignment tolerance is sub-mm, which is far less than the amount of movement these types of events are capable of generating. The proposal handwaves this by saying that the connection between the pillars and the tube will be “dampened.” So what does this mean? It surely can’t be passive shock absorbers, because those wouldn’t be sufficient to keep the tube in alignment. And it surely couldn’t mean active suspension capable of responding to tiny shifts in alignment in fractions of a second, because that would be expensive. Again, years of research and prototyping, and many more to make it commercially viable.

          • Andrew Palfreyman

            That’s an excellent answer – thanks. I have saved it and will use it to think about. I do mention the navigational aerodynamics issue (along with the thermal issues) in my original post, so I share that concern.

            Perhaps the best way to cut the Gordian knot here is to get the air cushion thicker so as to be able to tolerate bigger misalignments. Since the incoming air is divided up between flow-through and cushion, this might simply mean diverting more to the cushion.

          • Nathanael

            Andrew, pneumatic tubes are a well-researched technology. There’s a reason they aren’t used, and Musk has not changed that.

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  58. ED

    The canting is, in fact, effectively perfect. The capsule is banking inside a cylindrical tube. The calculations of side-forces allegedly felt by passengers are therefore based on a simple misunderstanding of the nature of the vehicle and track.

    Regarding cost comparisons to a viaduct, presumably the weight has something to do with the cost of a structure, and the tube has a comparatively low weight. The viaduct comparisons is an overestimate, a very spacious upper bound. To bracket the cost with a spacious lower bound, consider the cost of a high-voltage transmission line: a cross country structure with pylons supporting a very low weight. I somehow suspect that it is a small fraction of the cost of a viaduct — less than half, more than 1/100.

    In short, the acceleration calculations use the wrong basis, and the cost estimates are based on a biased comparison.

    • Alon Levy

      Both of your points are addressed in the post. Viaduct costs depend on much more than weight, and to the extent they do depend on weight, the dependence is much weaker than linear even according to the proposal. And perfect canting still produces some downward acceleration as perceived by passengers; 0.5 g is the acceleration passengers are expected to perceive after perfect canting.

      • cosmicbuzz

        Alon, Joey,
        You two already knew that I and other people already argued that reclining (~45 degree), knee higher, and pattern of blood flowing to the head basically cancel out the biological effect of 0.5g on passenger. You ignored these sound reasoning and never include them in your arguments, for obvious intentions.

        If standing with 0.5 extra g, blood flow more to the feet and maybe causing some people to have less blood in their head and feel uncomfortable. Blood in leg is roughly 1/2 height below heart. In reclining position suggested, the head is only at 1/3 of the normal height, the knee is higher so blood in leg is roughly 1/7 height below heart. So blood flow to the head (when reclining and 0.5g extra) is roughly same as standing up with normal g, maybe even more.

        You spent way too much time arguing the 0.5g. I accept the 0.5g early on, and already find solutions and reason the effect on human.

        0.5g extra does exist, but simply do not cause meaningful discomfort when reclining.

        Hope this will stop the waste of time on 0.5g.

        Should spend more time solving the hard alignment problem of mm gap of air cushion. I am trying to work out the combined solution of extra air cushion gap, front angle of air cushion, toothbrush-like air cushion, Halbach permanent magnet array (can be at top of pod), inductrack levitation, aerodynamic lift, with acceptable power consumption.

        • cosmicbuzz

          The open source people will setup experiment early on to prove it.

          They can rent time of an amusement park spinning/hanging capsule, fully enclose it so you can not see outside from inside, and put old people and all types of people into it, in reclining position, experiment with different g, then record biological data and feeling.

          Professors and students can review it thoroughly.

          • Joey

            Significant research has already been done about motion sickness. You would know this if you read Alon’s post, or bothered to look at Wikipedia, for that matter. The cause is a disconnect between visually perceived motion and motion sensed by the vestibular system. If you see motion but feel none it may cause motion sickness. If you feel motion but see none you are also likely to get motion sick. This is why tilting trains only compensate 80% of the centrifugal force (as Alon has mentioned elsewhere in this thread) – if passengers see the train curving but get no vestibular feedback, motion sickness is induced. Of course, if there’s enough acceleration, then even perfectly matched visual and vestibular perception will result in motion sickness, which is what happens on roller coasters.

        • Joey

          1) The discomfort at 0.5g has very little to do with blood flow and more to do with the fact that you can feel acceleration and that makes many people motion sick. Acceleration is sensed by the vestibular system in the inner ear. 0.5g in the horizontal direction would be nearly as bad as 0.5g in the vertical direction, especially without any visual cues. Adjusting the passenger’s position isn’t going to change any of that.

          2) Magnetic levitation is a real thing which is actively being developed and has even started to go beyond the prototype stage (albeit just barely). You may have heard the term maglev. It’s still significantly more expensive than HSR, but it promises faster speeds and very low power consumption even without enclosing it in a vacuum. Personally I’m betting on this technology over pneumatic levitation, partially because past experiments with pneumatic levitation haven’t really gone anywhere outside of short shuttle systems. Maglev in evacuated tubes (you may have heard the term vactrain) is still a long way out though. I would encourage you to read up on existing maglev developments – the Transrapid system currently has a commercial deployment in Shanghai, and the JR-Maglev project is expanding it’s successful test track into a revenue line.

          • Nathanael

            The Transrapid in Shanghai is a passively stabilized design and has real potential. The main problem there is, bluntly, the cost of magnets. If someone manages to make magnets much, much cheaper, then Transrapid-style maglevs will become quite viable.

        • cosmicbuzz

          So do you mean that it is the process of gaining to 0.5g cause the problem, but a mostly constant 0.5g does not cause problem?

          The time and intensity of gaining to 0.5g can be planned and can be anticipated. When I ride maglev in Shanghai, the gaining of speed is noticeable and short, when it is top speed, it is smooth. There are 20 minute top speed in p42.

          More on inductrack maglev combining with air cushion, later.

          • Joey

            The acceleration is never constant because the route is not uniformly curved, both vertically or horizontally. I don’t know if a person feeling 0.5g over a long period of time would get motion sick, but that’s not what we’re talking about here.

            Anticipating the acceleration isn not going to prevent people from getting motion sick. Motion sickness is not a conscious response.

            And the acceleration you feel on the Shanghai Maglev is nothing close to 0.5g. Closer to 0.2g linear acceleration I think, and much less than that on curves (less than 0.1).

          • Alon Levy

            When I timed the acceleration on the Shanghai maglev, it was less than 0.1 g – it just remained just less than 0.1g at far higher speeds than for conventional HSR. I do not remember how the sideways acceleration was: Transrapid claims to tilt 12 degrees or 16 in special circumstances, which would mean 1.67 m/s^2 of uncompensated acceleration, but it could be missing an additional cant, I’m not sure.

            However, the initial acceleration on JR-Maglev appears to be 0.2 g.

            Also, re anticipating acceleration and motion sickness, elevators for the most part let you anticipate acceleration. When you’re going up to the 35th floor and you see that the elevator is on floor 32, you know you’re about to experience less weight briefly.

        • Ricardo B

          Your reasoning is not sound. In fact, you’re barking at the wrong tree.
          Reclining the seats helps with lack/excess of blood in the brain due to vertical g-force, as experience by fighter aircraft pilots.
          However, 0.5g isn’t a problem. Regular healthy humans can handle +5g before blacking out.

          The problem here is that these forces messing up with the sense of balance and inducing motion sickness.
          AFAIK, there isn’t anything supporting the idea that reclining the seats will allow passengers to experience those accelerations with a minimal risk of motion sickness.
          As an example, people can get motion sickness if they’re in a car which repeatedly accelerates and brakes in a straight line (no vertical and no sideways acceleration).

  59. J Roam

    Interesting article, thanks for writing it. I analyzed only the vacuum part of the white paper and came up with a cost about 12x higher than what they had, and I was not being lavish at all. There is also a severe dynamic loading problem for the pumps with the pressure wave as each car passes. It could be damped but that is more money….

    I think the attitude of Musk is summed up in the first page of the white paper, when he mentions teleporting and says someone please invent this…. Basically entrepreneurs like him assume that scientists and engineers are generally as stupid as most of their fellow suits. Not even the same order of magnitude.

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  61. JB

    Why would security take just as long when there are only 6 passengers per departure? I don’t think this is supposed to be a mass transit train, more like how flying on the Concorde was.

    • Alon Levy

      It doesn’t matter how many passengers there are per vehicle, but how many there are per unit of time. Security lines don’t take longer if airlines replace three 737s with a 380.

  62. Alon Levy

    To everyone who’s discussing comfort issues and acceleration:

    I think I finally understood the point about tilting the passengers. On fighter jets and spaceships, the acceleration limit is based on the ability of the pilot to survive. People can survive larger forces forward and backward than upward or downward, so tilting helps orient people in a direction that makes sure the strongest acceleration will be dorsal or ventral rather than anterior or posterior.

    This does not work for Hyperloop. The problem is that the assumed deceleration rate for headway purposes is the same as the proposed downward acceleration rate after fully tilting the capsules. Passengers could feel the same acceleration in any direction.

  63. cosmicbuzz

    As with any open source turned real, the original draft is totally non-existent in working one, but the disrupted idea usually remains. If you only criticize at the pdf by Musk, open source people and I can grant you (Alon, Joey) the winner of the debate right now and you can continue bashing Musk (the public figure) any way you want. Because all we care is how far and how solid we can explore to make the general idea turned real, and have tons of fun. We understand the positives and negatives of leaders and don’t have to love them, but we do love the discovery of the beautiful fact of technology hidden somewhere, we love knowledge a lot more than hating people. However we truly thank you, and people like you, for playing the necessary roles of giving criticism that force open source (OS) people to explore and solidify solutions.

    The current draft route and radii by Musk and his engineers is likely a barf ride. Because of my idea of oscillating inner cabin almost eliminate the sideway G and turn them into downward G for passenger, we only have to deal with downward G (caused by centrifugal force) and forward/backward G (caused by linear motor) as 2 axis, and plot along time axis, we get a 3D graph. I am sure OS people will find the optimal route, curves, and speed control, so the 3D G force graph is most smooth.

    You can picture that the trajectory of the passenger inside inner oscillating cabin look like the trajectory of the person inside a bobsleigh (pod shell is not like a bobsleigh), except that passenger cannot see the track, only feel the downward G.

    When there is predominant downward G gain, we can show a video screen of a space elevator. In the screen, my avatar currently is sitting at 28th floor not moving up for 1 minutes, then an up arrow flashes, and it is showing I am going up to 70th floor (so I have an expectation), the elevator gives me clue how the elevator is moving up at the moment, closely match the downward G I am experiencing. From 50 floor to 70th floor it gradually slow down. When I reach 70th floor, it tells me I will stay there for some time. The process repeats and I might get up to 400 floor.

    When there is predominant forward acceleration, it can show a Ferrari, road, prominent speedometer, and gas gauge. You get the picture.

    The current ROW likely will modified by the optimal route. The goal is mostly above freeway, not necessarily at middle, some part needs to buy private land. The pylon can be ‘n’ shape when above freeway lanes, or triangle (against centrifugal force).

    Can we wrap up the issue of comfort now?

    I really want to move on to the very difficult but exciting problem of small gap of air cushion under ski, that I want to combine it with inductrack maglev, and wings inside air duct inside the pod.

    • Ricardo B

      Alon already was assuming perfect canting in his analysis. That is, he was assuming Hyperloop would bank the capsule as much as needed.
      The proposed accelerations are too high and there’s no banking angle that provides an acceptable result.

      And this is not an issue that can be glossed over because, unlike the air cushion, it’s determined by known limits of the humans which we want to transport.

      So yes, we can wrap this issue: at the proposed speeds, Hyperloop will need very very straight track to keep the acceleration within human comfort parameters, much more than a 200 mph railway, much much more than a road designed for 75 mph.

    • cosmicbuzz

      Thanks for wrapping it up.

      Now I am even more convinced about the great advantage of tube-based solution for near sonic transportation.

      Imagine there is inductrack maglev (search for it) pod that is already partially levitating:

      * You put tube to enclose it and embed the coil into tube to remove the track (and alignment cost) because there is no derailment thanks to the tube circular protection and flexible ski positioning.

      * The air pushed is reused and not to waste energy (the inner tube surface can have golf ball-like dimple to make air flow faster).

      * Tube makes low pressure air possible and reduce energy to get to near sonic.

      * Propulsion can have more placement option around the tube. It can be placed on both sides, where each side has 1 rotor (on pod) and 1 stator (on tube), different from Musk pdf to reduce need for tight alignment.

      * And then you add several wings safely inside pod air duct (I will cover the design later). The basic principle is to create low pressure right on top surface and high pressure right below bottom surface of each wing blade.

      * Pod energy and air tank send compress air to ski to help further levitation with a much larger gap than the pdf to allow more margins for tube alignment. 2 sides and back side air aim to the center, not downward, so as to trap the high pressure air within ski area.

      * Safety wheels are around the pod, even on top.

      You see, the tube design eliminates a lot of costly design problems to achieve near sonic.

      I don’t know if it is possible to modify inductrack so it can be attractive at the top of pod, versus repulsive at the bottom. So air cushion and maglev do not have chance to overlap.

      This is basically a plane, hovercraft, inductrack maglev, bobsleigh with large levitation gaps, with safety wheels flying inside a low pressure and propulsion tube that guides and protects the pod, and the air flow energy is recycled green, the best of all, it is near sonic!

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  65. Harvest Zhang

    Your math is faulty.


    The other points may be discussed, but your assertion about the forces involved creating lack of comfort is not backed up by your math.

    The 0.5g figure is BEFORE any cants. Look at his numbers; 760 mph at 23.5 km radius turns. Recall that centripetal acceleration is v^2/r. That comes out to 4.9m/s^2 lateral acceleration BEFORE banking the pod at all. And I’ve shown that if you tilt it, passengers will only feel 1.12g downwards and 0 lateral g.

    Come on now – you can’t blast Musk for suspect numbers and then make a mess of your own 🙂

        • Alon Levy

          Section 4.4, on PDF-pp. 38-39. The graph on PDF-p. 42 also seems consistent with constant 5 m/s^2 acceleration and deceleration (how they’re going to get so much power at top speed and then lose it while decelerating, I’m not sure). The route visualizations are loopy in other ways – they seem to ignore acceleration and deceleration time penalty entirely, so that e.g. the Sylmar-Castaic travel time assumes constant cruising at 480 km/h, without any extra time for accelerating from zero at the Sylmar end.

        • John

          On page 40, they mention a 4.8 km radius at 760mph. My high school physics is rusty, but at 340 m/s and a radius of that size, aren’t we talking about significantly higher GS? A=v squared / r?
          That said, I am confident that passenger comfort issues can be mitigated.
          I would be more interested in hearing from someone in the pipeline industry about the costs and anticipated economies of scale for 25k pylons of a size indicated by the white paper (I tend to think that pipelines are a better analog than HSR for the tube construction).

          • Joey

            Why are pipelined a better comparison? Pipelined don’t care about sharp curves, sub-mm alignment tolerances, and leaks aren’t the end of the world. They’re also usually closer to the ground and have more frequent supports.

          • John

            Because, we ARE talking about a pipeline. So, their are different constraints. Maybe they are usually closer to the ground, but less often than rail. If I remember correctly from my childhood, pretty much the entire Alaskan pipeline is on short pylons. In essence, the engineering is the same. I’ll grant you that the tolerances will be much tighter, but then again these are solvable engineering problems (much the same way the HSR community created automated means for handling its tighter tolerances over traditional rail).

          • Joey

            The engineering is nothing remotely similar. The only similarity is that they both look like tubes. The path constraints (curve radii tend of kilometers), construction techniques, grade separations, materials, safety features, and internal equipment are completely different. And I’m leaving a lot out.

    • Digital Cosmology (@DCosmology)

      I liked you blog post. I have been trying to say this here since day one that the resultant g-force can be manipulated by suitable banking. See my posts above. Most people fee motion sick because of fear and fixation of eye movement in stationary objects. This is not the case inside a tube. You could even rotate the tracks enough to cancel g and provide the sensation of free fall at suitable speeds. G-forces are not an issue but those who are affected by them can take the bus. I am sure many people will get addicted riding in a hyperloop.

      • Joey

        If you feel like you are in free fall in the presence of a gravitational field you are in free fall. Maybe that’s useful if you’re trying to end up underground? Won’t be very useful on horizontal curves though. If nothing said here makes sense go take a physics class – preferably college level, though high school level would be suitable as well.

        • Digital Cosmology (@DCosmology)

          You do not understand physics, not even remotely, and yet you are starting getting ad hominen here. If the rail is banked, as @Zhang wrote and I before him, the instantaneous center of rotation towards which the changes of tangential pod velocity are directed changes and the affect is that the g-forces change. This is no different from banking race tracks. By the way, you are confused with direction. “Downward” is anything you define as being downward and you stick with the definition. If you move on a plane parallel to the Earth’s ground “downward” can mean the direction of the gravity force but in pod dynamics, “downward” can mean the direction of the passenger seat, which can be on an angle with the ground due to banking the tracks.

          I am sure you do not understand 90% of what I wrote above. This is not bad if you are willing to learn and stop being insulting. Print this out along with Zhangs blog and take it to your professor.

          • Joey

            Banking the track does not change where the center of the curve is. The path you are taking is still circular and parallel to the ground. It only changed the direction in which you perceive various forces

            Engineers don’t use free body diagrams for these types of problems because the dynamics are well understood. It doesn’t make it any less of a valid way to describe the dynamics. If you are unable or unwilling to communicate in the universal mechanics language of free body disgtams, this discussion isn’t going to go anywhere. I went ahead and found a page which has some anyway (see especially: frictionless banked turn). Note while you read: what matters is the normal/frictional forces, since these are what passengers feel. Unless the laws of physics apply differently to you, you are making basic mistakes.

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  67. Digital Cosmology (@DCosmology)


    “If the net force is not parallel to the ground you are going to start accelerating up or down. Again, I implore you to draw a free body diagram.”

    Capsule banking affects both the magnitude and direction of g-forces. Free-body diagrams are drawn by students mostly. Professional physicists and engineers work with vectorial equations.
    By the way, when you stand on the ground you are accelerating downwards at 9.81 m/s^2. You are on a free fall and the ground is stopping you by imposing a force on you equal to your weight. What is your point then? That downward acceleration is bad? As Einstein demonstrated with his equivalence principle, in a free fall although you are experiencing the acceleration of gravity you cannot distinguish between that and inertial forces due to linear or curvilinear motion.

    People get motion sick on elevators.

    The sister of a friend gets motion sick only by hearing the word “airplane”. Does this mean we should have never developed this technology?

    Is someone gets sick in an elevator then unfortunately he must walk up the stairs. If someone gets sick in a hyperloop, then he must take the bus. You cannot make any progress by taking into account what makes a small percentage of the people sick. You just accommodate them with alternatives.

    I think the acceleration issue is due to a widespread misunderstanding of inertial dynamics which is tolerated in colleges and universities because the effort needed to explain these concepts will put a strain on students that cannot understand them and make then drop the courses.
    Maybe the project is not feasible due to the other good points you have made which I cannot judge.

    • Alon Levy

      The vectorial equation spits out the same answer about the extra acceleration vector. I don’t want to bore you with how I think of this (on the informal level, it involves Lie algebras; informally I still do it with vanilla vectors).

      The acceleration issue re motion sickness is that it’s not just the same as an airplane or an elevator. It’s much worse – about twice as bad as the worst moments of flying during several acceleration and deceleration cycles, as well as on curves. People would barf. And any attempt to produce a less barfy ride would choke capacity by forcing longer stopping distances. The elevator here is an analogy for why any acceleration produces motion sickness when not accompanied by a change in visual cues; it’s not to say that the amount of motion sickness is the same.

      • Harvest Zhang

        You don’t need “vectorial equations,” much less anything related to Lie algebras. A free body diagram (useful and used by world-class physicists, by the way, not just students) could be used, but this is mostly just basic high school trigonometry and vector manipulation.

        There’s no need to try to sound smarter by introducing a lot of unnecessarily complex buzzwords that don’t add anything. Being smart is being able to find the most elegant solution, which in this case requires no more than high school math. Anything more than that is overcomplication and unnecessary.

        The extent of the computations I had to make, by the way, are contained in the two footnotes in my post. That’s all. They’re very simple.

        • Ummon

          From section 4.1.6 of the report, we see that the capsule is accelerated and deccelerated longitudinally at a maximum of 1 g for comfort.

          Section 4.4 presents a similar result. It shows that for a curve radius of less than 1.6 km, the capsule will be travelling at 300 mph (134 m/s). This results in horizontal acceleration a=v^2/r of at least 1.14 Gs. It also shows that for 760 mph (340 m/s), there can be a tube bend radius of as little as 4.8 km. This results in horizontal acceleration a=v^2/r of as much as 2.46 Gs! I’m assuming this part of the report was in error, as such a high acceleration is inconcievable.

          Now you can use the pythagorean theorem to calculate the total acceleration, and you’ll find that for the 1.6km radius case, the total acceleration is indeed 1.53 Gs (half a G excess).

          • Falstaff

            The minimum bend radii are given for various speeds in Tables 3-5, never exceed 0.5g

          • Alon Levy

            And elsewhere in the document, e.g. on PDF-pp. 39-40, the radii quoted are tighter and give 0.5 g after perfect canting. In addition, I didn’t notice it until just now, but on PDF-pp. 22, 33, and 34 the specs call for 1 g of acceleration. (I’d thought the acceleration was 0.5 g, since that’s the deceleration rate implied by the braking distance.)

  68. Pingback: Elon Musk's Hyperloop: A pipe dream? | Los-Angeles News
  69. Digital Cosmology (@DCosmology)

    “Banking the track does not change where the center of the curve is. The path you are taking is still circular and parallel to the ground. ”

    Think about it like this: increase the banking angle theta slowly to the point that motion is vertical. Do you still think that the centripetal is in the horizontal direction and remains there during the shift? If that were to be true, no motion would take place. Think of it another way, I asked you to do this before but you seem to read only what you want. Take a ball tied to a string and swing it above your head carefully. Where is the direction of the centripetal? It is horizontal. Now tilt the rotation plane. Do you think the centripetal remains horizontal?

    Read this and answer the questions. Then come back and I will explain to you why the physics you were taught and you linked to is wrong. The deeper reasons for that. Of course, they are approximately correct for low speeds and very large radii that minimize the effects of centripetal forces. But not for the project we are talking about.

    • Ricardo B

      If you have an horizontal curve then, the there will be a sideways acceleration of a_h = v²/2 and vertical acceleration a_v = g (gravity).

      If you bank the capsule by an angle phi then then passenger will experience the following accelerations:
      a_h’ = a_h * cos(phi) – a_v * sin(phi)
      a_v’ = a_h * sin(phi) + a_v * sin(phi)

      By banking you can reduce the sideways acceleration the passenger experiences (a_h’), but there’s a trade-of as the passenger experiences increased vertical accelerations (a_b’) .
      There will be a phi angle which makes a_h’ zero, but it also maximizes a_v’.

      As per known passenger comfort limits, a_h’ needs to be 0±1 m.s⁻² and a_v’ needs to be g±0.67 m.s⁻².

      Calculating the limit is quite simple, as a_h² + a_v² = a_h’² + a_v’².
      Thus, the max value of a_h = v²/r = sqrt(1.0² + 0.67²) = 1.2 m.s⁻²

      • Scott Andrews

        I did this same math a couple of days ago..posted somewhere up above. but used Alon’s determination that the lateral acceleration would be 11.1 m/s^2. At that level, the normal acceleration felt by the passengers will be 1.6 G and the lateral acceleration will be about 0.5 G (this was with an assumed 30 degree banking). This is well in excess of the comfort limits you state.

        I am not sure where you get your comfort limits, but on this basis the curve radii will need to be ~10X larger than planned, or the cars will need to slow down to 240 mph for the turns (with a corresponding impact on capacity).

      • Digital Cosmology (@DCosmology)

        If you rotate the coordinate systems but you keep the direction of the centripetal acceleration as initially, horizontal, (parallel to the ground) then the accelerations on the new horizontal axis add and on the new vertical axis subtract. In addition, you are making the same mistake as @Joey and as every other cheap physics text delivered to lazy students by lazy professors: you assume that this is a planar banked track. But this is not the case. The motion of a pod on a arbitrarily banked track is in 3-space and centripetal acceleration will depend on the parametric form of the path, something that @Joey is justified not to know but not justified to turn ad hominen before going to graduate school and getting into some more depth in these matters. For all practical purposes in real-life race tracks the difference will be small and usually about 2% – 5% in the speed due to banking even if the track is not perfectly planar. But when we are talking about rollercoaster, the situation is different. There small errors count and can cause damage.

        • Scott Andrews

          On a momentary basis the track is planar. Since all of the vectors are orthogonal to the curved track tangent, at any instant you can look at these vectors without any concern for the fact that in the next instant their radial angle relative to the track center of curvature has shifted slightly (your “parametric form of the path..”). With a constant speed and constant curve radius, all of the vectors will move in the same way and so their relationships will be static. And yes, the cant will reduce the lateral acceleration in the car frame of reference, but at a cost of much higher normal acceleration (this is why a car on a banked track at speed can actually bottom out on its suspension…).

          And BTW, dissing others is not an effective way to make your point.

          • Digital Cosmology (@DCosmology)

            I was attacked first and your physics is wrong in principle. You are making up things out of who knows what. Write the parametric form of the track path first. What you are describing is a flat planar track.

          • Digital Cosmology (@DCosmology)

            “With a constant speed and constant curve radius, ”

            FYI, nothing of that sort applies in a hyperloop with an arbitrary path. You are oversimplifying things in your mind to fit them to your conceptions.

          • JCW

            But isn’t the problem with your assumptions that the capsule’s speed isn’t constant (though its energy is, roughly), and the curvature of the tube varies? (and not necessarily smoothly)

            Your model will hold for some interval of a sufficiently long segment of constant curvature, but not in general. Of course, it is arguably sufficient to show that the “equilibrium” forces are too great for humans to stand…

      • Digital Cosmology (@DCosmology)

        @Ricardo B.

        From this:

        a_h’ = a_h * cos(phi) – a_v * sin(phi)
        a_v’ = a_h * sin(phi) + a_v * sin(phi)

        you cannot get this:

        a_h² + a_v² = a_h’² + a_v’².

        So try again…

        before you and Scott get too excited…

        • Ummon

          Yes you can (the second equation should read a_v’ = a_h * sin(phi) + a_v * cos(phi)).

          Just square the two equations, then use the sum and difference square rules, cancel out the identical terms, and then use the Pythagorean identity (cos^2+sin^2=1).

          Transformations do preserve magnitude.

    • Scott Andrews

      Your ball on a string analogy, while clever, misses the mark. because the entire reference frame, including the “track” will tilt when you tilt the rotational plane of the string. In the case of the track, that would require that you tilt the gravitational field, or titlt the entire plane of the track. The ball and string undergo these same forces, but a) they are damped by your arm (the center of curvature is actually moving around) and they are small compared to the relatively large centripetal acceleration being applied.

      • Digital Cosmology (@DCosmology)

        So you think the pod of a hyperloop moves on a circular planar track, right? I asked @Joey and now I ask you to take a moment and think: if the track is banked at 180 degrees like that of a rollercoaster, where is the center of rotation at that moment? And if it is not parallel to the ground, when did the change in the direction of the rotational axis takes place.

        Obviously, you have been taught some basic physics a long time ago but not the whole story – and half the story in physics is no story.

        • Joey

          If you bank the track at 180° you are hanging from the track. Banking does not change the path that the vehicle takes in space, or the net force necessary to take that path. It changes the angle at which the various forces are applied.

          So far, this discussion has progressed as “you’re wrong this is how it works” “no you’re wrong this is how it works.” So I took the liberty of finding some references (academic even). They all support what I, Alon, and others have been saying – centripetal force (net force) must be toward the planar center of the curve regardless of the bank angle. I challenge you to find one source which supports what you are saying.

          • Digital Cosmology (@DCosmology)

            I would accept the challenge but first as I noted above we must talk the same physics because when you say that “centripetal force (net force) must be toward the planar center of the curve regardless of the bank angle.” you are talking strange physics in the case of a hyperloop. The center of curvature is where it is and need not to be parallel to the ground. I tried many times to make you think about it by making references to a rollercoaster. Apparently, you think that in a rollercoaster situation the centripetal force always points parallel to the ground. If now you changed your mind after this, think of the hyperloop as made from parts of a rollercoaster. The banking angle can be greater than 90 deg. In this case there will be minimum lateral force on passengers and centrifugal forces will be partly cancelled by gravity and directed along the passenger seat. On the absence of a fixed reference point outside, the motion will not be noticed because most of the motion sickness affects are rather psychological than physical. This is the future of transportation.

          • Ricardo B

            Aparently, wordpress won’t allow further nested comments, so I’ll reply here to DC.
            The radial acceleration is always perpendicular to the curve path. I think we all agree here.
            If you need to take a curve on the horizontal plane, the radial acceleration is parallel to the horizontal plane.
            In order to have a non-horizontal radial acceleration, you need to add a non-horizontal component to your curve.

            Yes, you can use that to further reduce the acceleration experienced by passageners: instead of just curving left, you curve left AND down.
            The problem is, unless that’s what the terrain calls for, the track is now on a downwards slope running into the ground. It’s not a generally usefull solution to the problem of avoiding obstacles in the terrain.

          • Joey

            Yes. You can reduce the apparent magnitude of the force felt by accelerating downward, but you’re going to end up changing elevation rather significantly. Not particularly useful when you actually have to worry about pylon height and the actual height of the terrain you’re crossing.

  70. Johnny Le (@johnny0129)

    Even if the hyperloop costs as much and runs as slow as the high speed train to be safe, I still think we should do it because then we would have a fifth mode of transportation that we can improve and optimize upon and maybe someday it will be truly better than the rail, but more importantly it is a self-powered system with no pollution, not even noise pollution. So imagine a society where we can travel 2-3 times faster than cars but depend on energy as much as when we first invented the bicycle and can too breathe in the air as fresh as the air of that era.

    Our society can’t progress at this pace for long if we don’t become energy independent.

    • Scott Andrews

      And just how is it that this is “self powered”??You will need power to keep the tube de-pressurized, power to move the cars, power to keep the passengers cool, etc, etc..

      I’d like to see the leak rate calculations on the tube.. Each tube represents about 8.1 Million cubic meters of volume (less the volume of the cars). Just maintaining the pressure, especially given the airlocks at the stations, and the 1001 other leak sources, will require some pretty massive vacuum pumps located pretty much all along the tube. How will those be “self powered”?

    • Nathanael

      The “hyperloop” is basically a poorly-thought-out variant of pneumatic tubes. It’s already a “fifth mode”, it’s just one which failed to be commercially viable for most purposes. Musk hasn’t solved any of the problems with pneumatic tubes.

  71. Pingback: Loopy Transportation Ideas
  72. Scott Andrews

    I was thinking about car spacing and boarding time while flying home last night. As long as everyone is synchronized, the cars can decelerate and accelerate without colliding, but any stop time must be added to the spacing. This isn’t an amusement park ride where one group steps out and the next steps in, in a super organized way. The passengers will have luggage, briefcases, shopping bags, etc.
    This scheme has a variety of additional elements that will extend the boarding/deboarding time beyond what we see on trains like the Shinkansen:
    1) The cars are very small and narrow (a 6 foot person will need to stoop to get in)..so getting into the car and to your seat with your stuff will be slow and serial. If you claim that the cars will open up for parallel boarding, then add in a huge new problem for sealing and safety (and multiply the car costs accordingly).
    2) Because of the dynamics (lateral and vertical accelerations), the passengers will likely need to be restrained (we require seat belts on planes that operate at a fraction of the G forces here). This adds time (to restrain them, to check their restraints, and to correct those who are not properly restrained). NTSB will insist on it, probably more so than with airlines, given the potential for catastrophic and cascading failures with this system.
    3) Because they are restrained and the cars are small and narrow, folks getting off will not be able to queue up with their stuff in the car to get off as it approaches the station, and the train will not be able to start while folks are getting situated.
    4) There will be some additional time for the whole airlock process to work. Unless they plan some in-station process (which will mean the entire platform area will be de-pressurized – good luck with that…), the process will require an airlock at the station entrance, and one at the exit. The car will need to stop in the airlock, the door behind will close and seal, and the airlock will pressurize. The door to the station will open, and the car will move into the station. On departure, the car will move into the exit airlock, the door to the station will close and seal. The airlock will be evacuated, and then the forward door will open and the car will depart. I estimate that the practical time for this will be about 105 seconds in each direction (See below).

    The Shinkansen stops for about 90 seconds, and that’s pretty short if you have a bunch of stuff, or folks who are not really crisp in their deboarding and boarding. However, the cars are huge, and there is ample time to get your stuff put away and find your seat while the train is accelerating away from the station. It is not at all uncommon for the door to close behind the last person, and for people to take several minutes to get situated, meanwhile the train is accelerating away from the station. Not so here..

    Under the best conditions, I would suspect that the deboard-board time will be about 2-3 minutes, maybe more. If the system requires some heroic board-deboard process and restrictive luggage requirements, then it will be just that much less attractive to folks. Then you have 1 minute on either end to pressurize and depressurize, so the total station time is about 5 minutes, not 30 seconds…This means the practical capacity is actually about 10 times less than advertised since the car spacing will be much longer. On the up side, this eliminates the stopping-distance-pile-up problem if there is a fault.

    This also raises yet another question which is what do you do at the termini? Here we have assumed that the cars take off after a brief stop, but at either end you will need some large facility where the cars at least get cleaned of the trash (and barf) left by the last passengers. If not then the system will become as delightful as riding a city bus.. . If trains are arriving every 30 seconds there will need to be some substantial facility for storing them while they get cleaned and shifted to the other tunnel Unless you assume some large end loop, which might be practical in Sylmar, but not anywhere in the bay area. In fact the entire car management process will be a challenge since tunnels are not quite the same as rails in terms of switching and sidings, etc)

    And don’t even get me started on passengers cooking in the tube out near Bakersfiled in the summer when the system has an issue and the cars stop for 45 minutes…I’ll do another post on that…
    This entire idea has so many holes it is surprising that anyone (including all of us) are actually giving it any time..

    Evacuation time is given by t = V / q ln(p0 / p1), where V is the volume to be evacuated, q is the flow rate, and p0/p1 is the ratio of the pressures before and after evacuation. If you assume the volume of a car sized section of the tube is about 400 m^3 (15 x 3 m dia), and the car is about 150 m^3 (12 m x 2 m dia), then you need to evacuate about 250 m^3. A 15K cfm pump (weighing 30K Lb) will go from 1 bar to 0.1 bar in about 90 seconds…Then you have the door seal/unseal time, say about 15 seconds on each end…So a total pressurization/depressurization time of about 210 seconds (3.5 min), assuming the pressurization and depressurization rates are the same, which is arguably pessimistic. You might be able to do this faster (like using a 2500m^3 vacuum cylinders to suck the air out of the lock, and this would take 10X as long to evacuate, so you would need a number of them to accommodate the car arrival rate. ). At some point the pressurization and depressurization will be explosive, so there will be a limit to how fast this can be done.

    • aw

      You could improve the airlock cycle time by batching cars. Load some number of cars simultaneously and put them all into the airlock. Evacuate the airlock, have all the cars enter the tube and then close the door to the tube and repressurize the airlock for the next cycle. The cars in the tube are then dispatched one-by-one at the appropriate headway.

      At the destination, do the same process in reverse. Put cars into the airlock one-by-one until it’s full, close the door and repressurize the airlock. Move all the cars out and unload them in parallel.

      There might be some tricks you could use to reduce the cycle time of the airlock. If the cars fit closely to the sides of the airlock it would reduce the volume of air to be evacuated. At the endpoint, cars could tun off their compressor and coast into the airlock, compressing any air in the tube ahead of them. The higher pressure ahead helps with braking.

      At the endpoint the cars will need more service than just cleaning. They will need a battery swap, the cooling water tank will need to be refilled and that giant tank of superheated, high pressure steam will need to be emptied. Maybe that could be dumped into a steam turbine to generate a bit of electricity.

  73. paradoctor

    The big expenses are right-of-way, the closed evacuated tube, and pylons. So here’s my suggestion; forget long-haul and do tens of miles; city-to-suburb, suburb-to-suburb. No pylons, at-grade. Short haul, so you don’t have to go at airline speed; therefore no need for an evacuated tube. If air suspension and linear electric motors still work in a semi-circular trough rather than a closed tube, then you’ve got a system.

    • Joey

      1) Right of way is a small fraction of overall costs; the actual structures dominate in any environment, but especially in urban areas where you have more grade separations to deal with.

      2) Past experiments with pneumatic levitation have demonstrated that it doesn’t really have any advantaged over maglev, or conventional rails for that matter. At this point, for top speeds less than 400 km/h, steel-wheel-on-steel-rail trchnology is still the cheapest.

      • Nathanael

        Too many people underestimate the massive, MASSIVE physics advantages of the conical wheels on the angled pair of rails. This passively stabilizing design has had huge advantages since it was discovered in the early 1800s.

        It’s worth noting that various forms of trains were invented before then (for hundreds of years!) and none of them were commercially successful; the conical wheels on the angled rails are a really big invention, historically. People who think they’ve invented something better are nearly always wrong.

  74. D R Lunsford

    Nice piece. My approach to such things is much more simplistic – what’s the obvious failure mode? In this case it’s sudden breakdown of the vacuum. So here’s a people mover going 800 MPH and it suddenly slams into a big mess of air in a tube. The results would not be pretty.


  75. proenglightenment

    If I had what I believed to be sound physics-based objections to any aspects of Musk’s Hyperloop alpha study, I would certainly be curious to know what his engineering staff had to say about them. Musk put out the open source study to elicit just such comments, or better yet, ideas to improve upon it. Perhaps some of you would be willing to forward your comments to hyperloop@spacex.com. Musk is contemplating building a prototype at some point; you’d do him a service if you could point out any showstoppers.

    • Nathanael

      There are dozens of showstoppers, but the largest is his failure to look up civil engineering costs.

      Musk can read blogs as well as anyone else can, and if he doesn’t want to waste money, I suggest he do so. It is not worth emailing him just to tell him he’s been a complete idiot.

      • proenglightenment

        I think your comment is mean-spirited and small-minded. If you have specific technical objections to the model he proposed, you should send them to his engineering staff. Otherwise, you come across as a person who either harbors jealousy toward Musk or who for whatever reason wishes him to fail. The Hyperloop is a forward-thinking mode of mass transportation. It may be fatally flawed, but I think its proponents, principally Elon Musk, should be treated with respect, given his high-level of technological achievement. Calling him a “complete idiot” is simply nonsensical and juvenile, at best. Shame on you.

        • Joey

          I would have a lot more respect for his proposal if he actually cited sources. As someone who values science I can’t respect this. Especially since many of the things he gets wrong can easily be found in civil engineering literature.

    • Anon256

      There is nothing “open source” about this proposal. The PDF Musk published contains no copyright notice, but as it appears on the Tesla website it is implicitly “Copyright Tesla Motors, Inc. All Rights Reserved,” which is obviously not an open-source license. The document is furthermore severely lacking in the reasoning behind most of its content, most obviously the cost estimates but also apparently arbitrary design decisions like the capacity of the capsules, the top speed, etc. (This reasoning corresponds to the “source code” as it would be necessary to generalise the proposal to other parts of the world or consider the impact of changes.)

      Providing a feedback email address clearly does not make a project “open source”. Even Microsoft does that.

  76. Dr. RTFM

    You said: ‘On Wikipedia, it would get hammered with “citation needed” and “avoid weasel words.”’ And yet the Wikipedia article on hyperloop is positively fawning; any attempts to correct it result in undos with a claim that the editor is doing original research, which is rather sad given that the material cited by Wikipedia is itself all original research.

  77. Darius

    After reading calculations on changing track altitude I stopped looking in your stuff. According you plains should not take off or descend without smashing passangers. The g force effect depends on period of impact on human body as well and in case it is miliseconds it could be even 7 g without any demage just shake. Elon Musk team calculated max 0.5 g limit even for very very short period.

    • Alon Levy

      Wait, what? Planes do take off and land, with maximum acceleration in the 0.3g area. Musk thinks 0.5g is fine, during multiple acceleration and deceleration cycles as well as at every curve.

      • Falstaff

        “maximum acceleration in the 0.3g area.”

        Maximum on take off and landings perhaps, but large passenger aircraft commonly bank up to 25 degrees, producing a load into the seat of 1.1 g, i.e. 1/cos(bank angle). The turn may come on suddenly. For that matter, I would think it clear that passenger aircraft typically maneuver in similar radii as given in the Hyperloop proposal (4 km-480kph, 13 km-900kph, 24 km-1200 kph). They do so with passengers buckled into ‘tubes’ at night and/or with blinds drawn, yet motion sickness seems to be an occurrence overwhelmingly reserved for period of turbulence.

        • Joey

          I’m going to call bullshit on this. 0.5g is already in the range of “I have trouble keeping my body parts where I want them.” At 1.1g you probably wouldn’t be able to stand up.

        • Alon Levy

          The additional load onto the seat is 0.1 g, not 1.1 g. To perfectly bank its turns, Hyperloop would have to bank not 25 degrees but 48.5 degrees, producing the 0.5 g of additional load onto the seat.

          • Falstaff

            “The additional load onto the seat is 0.1 g, not 1.1 g.”


            “Hyperloop would have to bank not 25 degrees but 48.5 degrees, producing the 0.5 g of additional load onto the seat.”

            Perhaps that refers to the apparently self-conflicting tighter radius comment in the proposal. The radius given in the table, e.g. table 4, 555 mph (890 kph), 7.8 miles, requires a 26.7 degree bank to achieve in an aircraft, or 1.2 g into the seat during the bank (total). The other two tables (3, 5) produce similar results.

            See for example:

            The resolution of the radius conflicts depends, I assume, on what minimum radius is actually required over the project. I have not studied the proposed path sufficiently to do so.

          • Joey

            What passengers feel is the force that the seat exerts on them to keep them in motion. If the vehicle is traveling in a straight line at constant speed, this is only the force required to counteract gravity, 1.0g upward, which is what everyone is used to feeling. If you are turning, then you have that force to counteract gravity and a force to provide centripetal acceleration. Let’s say for a given turn you need 1.1g in the horizontal plane. If the vehicle is not banked at all, then the passenger feels 1.0g upward and 1.1g to the side. If the vehicle is banked at the right angle, then the sum of these forces is perceived to be purely vertical, and with magnitude 1.5g (approximately). That’s an additional 0.5g compared to what passengers are used to feeling.

  78. Pingback: A Transitions Perspective on the Hyperloop | Aeleopile Blog
  79. Andrew in Ezo

    Alon, right on with the comments of the “culture of the superstars”- just look at the automatic credibility given to ex-generals and real estate tycoons/CEO’s whenever they put their hat in a presidential race- something about an perceived aura of straight-ahead, from the hip “can-do” around them appeals to the American psyche.

    Living abroad, I also identify with your comments about true progress coming from incremental improvements based on long-term practices and operations- in Japan, the operations of railways at their current efficient levels are based on decades of experience and subtle but consistent improvements, carried out by experienced staff and technocrats with combined countless of years of knowhow “on the job”. The same is true for rolling stock development- it has progressed consistently since the 1950’s in contrast to the devastating contraction and eventual extinction of the once innovative and world-leading indigenous American passenger rolling stock industry.

  80. cosmicbuzz

    @Alon, @Joey @DCosmology @ Harvest Zhang
    Rather than arguing about your calculations, please look at my modification to the route and see if the transitions of G would be sufficiently smooth and comfortable.

    The original pdf (p42, p47) “preliminary route” of the 20 minute top speed central valley section is as follow:
    Pay attention to Musk’s words “preliminary route”, that means open source is free to modify as he advocated.

    In Saturday comment I wrap up the comfort issue (not to waste time debating) and prefer straight lines, large radii, and less alternate curves. Keeping the route at the middle of I5 will cause the radii alternate to both side of the route and will cause motion sickness, especially when transit between 2 radii at each side of the route, when it is hard to keep passenger feel downward g constant during transition. Constant high g or gradual change of g is fine (aided with visual clues I proposed in comments), but not frequent gain or decrease of G.

    In my map the original route SF->LA ABCDE can be modified as AFGCDE. A is at time of about 1670 second of P42. AF is straight acceleration to top speed. AF transit gradually to FGC, FGC is a curve. CDE will be big radii curves. Section near G will need to acquire ROW, which does not cost much.

    Other sections of the modified route could be off to the side of I5 in small percentage of the route, mostly to the west of I5, where there are less expensive ROW hills (I know there is no planting and very few buildings at the hills). From A to D there are hills to the west of I5. ‘n’ shape pylon need to be used frequently to span lanes. Overall, the increase of ROW and pylon cost should not increase much more than preliminary route in central valley, I guess not more than 1.5x.

    This is a obviously workable small modification. I am sure other open source people will optimize comfort/cost even better.

    There are more context of overall issues in my comment https://pedestrianobservations.wordpress.com/2013/08/13/loopy-ideas-are-fine-if-youre-an-entrepreneur/#comment-10381 (several summary comments).


    • Alon Levy

      The problem with any such route is that the Central Valley is flat but not flat enough. ROW isn’t a problem – people think it is because planners and developers overhype NIMBYs as a source of opposition, but farmland is cheap and orders of magnitude more farmland gets lost to sprawl every year and nobody cares. That’s why I keep saying here and elsewhere that any proposal to put California HSR alongside I-5 (let alone in the median) is mad: it saves trivial amounts of money over putting it west of 99 and having stations at the edges of the Bakersfield and Fresno urban areas, and makes it impossible to serve Bakersfield and Fresno on the mainline.

      Rather, the problem with any Hyperloop route is coming up with a route that’s both straight enough and flat enough. The required vertical curve radius is so big that even small changes in elevation turn short pylons into tall pylons, which cost 50% more. If the route hugs the terrain well enough it can be on earthworks, as is planned for HSR in the Central Valley away from the built-up areas, which costs around $20 million per kilometer versus $50-80 million for anything involving viaducts. HSR is in a nice sweet spot of having powerful enough trains with enough preexisting speed that they can climb steep slopes without trouble but still having a vertical curve radius that allows reasonable transitions between different grades.

      The tunnel alignments are also less nimble with respect to requirements of reducing overburden and avoiding fault lines – that’s one of several reasons the $31 million/km tunnel cost estimate in the proposal is bunk. Modern HSR tunnels are often not straight lines, e.g. the (combined HSR and freight) Gotthard Base Tunnel has internal curves to avoid the mountain peaks and reduce rock overburden, and the engineer who proposed the non-straight route ended up saving money this way.

      As for the claim that this plan is open source, I defer to Anon256 on this. Open source means including the source code, which means including what went into the cost estimates, detailed plans for the pylons, etc. This is basically a closed-source system that Musk is saying “someone else should spend money on it while I trash HSR and try to get my car company to start making a profit.”

      • Ricardo B

        A quick note: the Gotthard base tunnels is designed for a max speed of 200 km/h (125 mph), which is not HSR by some definitions. It’s a different beast than 320 km/h (200 mph) rail.

    • Joey

      The central valley is the easy part no matter what you are constructing (noting that even there, elevated anything costs considerably more than at-grade anything). Buy all the farmland in a straight line and it’s still not that expensive, since land acquisition is such a small cost. The most costly parts are the the urban segments, which Musk conveniently ignores, and the mountain crossings.

      • cosmicbuzz

        @Alon, Joey
        So we have agreement that an optimized route in ~250mi central valley out of ~330mi total is feasible and comfortable for near sonic travel for mere ~20 minutes.

        I looked at the LA mountain and SF sections, optimized route will also make it feasible and comfortable with maybe 30% slower speed than the proposed ~15 minutes, still the total 40 minute ride is game changer.

        So all the lengthy discussions on ride comfort are mostly waste of time. Only my anticipation of robot development for route construction in this post truly tried to solve the most critical technical and cost issue. Musk did not do the cost right, but open source people will enhance it and make it work many times better than CAHSR.

        I estimate $15B could be sufficient to cover cost overrun, assuming the robots are made. Near sonic and green travel is great for so many people and the earth. Again, it is absolutely feasible to invent the robots within target cost, simpler than advanced robots, for the target type of repetitive job.

        After so many years, CAHSR made it so hard for voters to find main information to work on and compare with Hyperloop. They want our money, but don’t earn our trust first. Open source is just better in many aspects.

        I know some people would rather take 2.5 hour trip every day merely because they want a big house in remote area. That is bad for their families and earth. If CAHSR stops in central valley, large population of people will sprawl into central valley (with no water). That is very bad! The existing, low percentages of people in central valley generate low percentages of travel business. Taking 2-3 hour car trip to LA is just fine.

        There are 20million people in LA and SF. Scale of innovation, economic, and culture exchange is enormous. It is fair economic to ignore central valley low percentage population. CAHSR still has last mile issue. Metro rapid transit and cars cover the last mile. Fast security line for only 1 laptop bag makes the wait for security check not much an issue. With ~1.5hr end-to-end one way trip via Hyperloop is radically different from ~3.3 hour end-to-end one way trip via CAHSR. One can do a one day round trip easily. I really think 4 tube solution is feasible.

        Near sonic ground traveling is just too cool!

        • Joey

          Ignoring the technical issues with propulsion and levitation, as well as cost, yes, it’s possible to design an alignment through the Central Valley which is capable of 1000 km/h. You might have to ram through a few towns and wetlands along the way though, since the alignment is so inflexible.

          Again, the primary issues in either case stem from the mountain crossings and urban sections. HSR, as planned, will only spend about an hour in the CV. And I don’t know where you’re getting this 3.3 hour end-to-end thing. 2:40 is somewhat unrealistic given current plans (easily fixable), but 3:00 is easily achievable, and that’s CBD to CBD. SF-Hayward and LA-Sylmar are around half an hour each, then you have to add transfer time and security (noting that time spent not moving is perceived by passengers as being more significant than time spent moving). Passengers are better served by allowing through routing to a more complete set of destinations rather than pushing even higher speeds on the already fast segment and then marooning them at the edge of the urban area.

        • cosmicbuzz

          “CBD to CBD”, this is the failed argument.
          Most traveling SF-LA are not “CBD to CBD”. With CAHSR, the last many miles of most traveling SF-LA still require car or metro transit, that do not fair much better than hyperloop’s last miles. Residence/business simply spread too broadly in SF/LA metropolitan areas. In most long distance traveling, high percentage of destination is residence. That is why I roughly added average ~45 minutes to hyperloop, and ~35 minutes to HSR.

          From what were said in this post, I guess the cost of CAHSR’s extra last miles (compared to hyperloop route) might be >$20B. (Damn CAHSR again, it is so hard for average voter to find the info, and we have to guess and suspect.) ~$20B is unnecessarily enormous cost!! ~$2,000 from my pocket!! It does not even solve most of the last miles problem!

          There is virtually continuous boarding for hyperloop, very different from airport boarding. So the continuous security wait line can be optimized easily. For pre-clearance, one small bag passenger (they will be high percentage), it will take roughly 2~4minutes security check. Visualize this, 50 lines of security check lines can easily help 56 mostly pre-clearance passengers through per minute without much wait. Pods do not need high price driver and attendants.

          For continuous boarding of hyperloop, there is no extra budget/wait time due to concern of missing the train schedule. Hyperloop actually is faster than HSR in this regard.

          Another way to look at it is that time = 2 local commute + 45minute hyperloop, compared to 2 slightly shorter local commute + 2:45 minute CAHSR. You really can do 1 day round trip with hyperloop without too much fatigue, reducing the huge cost and inconvenience of arranging places to sleep at both ends. No place is better than home.

          The spontaneous nature of hyperloop traveling are what people are willing to pay for it, though they pay less for it 😉 It is just marvelous.

          My point about sprawling to water-less CV in prior comment is a huge problem caused by CAHSR.

          I think I am done with most point-to-point debating at scale of importance.

          • cosmicbuzz

            @Andrew Palfreyman.
            For your comment about bigger air cushion gap to solve alignment issue
            I thought about the challenge of it, and wrote about several solutions for it. You can search in this page where I mentioned “inductrack” to follow the reasoning.

            I wonder why people wasted too much time with calculation, and are not excited about all the winning features and viability of an improved hyperloop:
            “This is basically a plane, hovercraft, inductrack maglev, bobsleigh with large levitation gaps, with safety wheels, flying inside a low pressure and propulsion tube that guides and protects the pod, and the air flow energy is recycled green, the best of all, it is near sonic!”

          • Joey

            The last mile issue is nowhere near common. Yes, most people won’t originate near the CBD (and many will not have a destination near the CBD). The problem with these edge-of-the-urban-area stations is that they’re farther from most people’s origins/destinations than the CBD which is typically at the center of the region and have few or no connecting services. Los Angeles Union Station is the single largest transit hub on the west coast, with connections to many regions of the LA area. SF Transbay isn’t far behind with direct connections to everywhere in the BART system plus dozens of bus lines to other areas of San Francisco, the inner East Bay, and Marin County. And the “everyone will drive to the station” argument doesn’t work because (a) You then have to factor traffic into station access time and (b) Most people won’t have a car on the destination end of their trip (which ends up being more sensitive to access time). Transit links can be built, but you’ve then eliminated the hypothetical cost advantage of not building in urban areas. And peripheral transit hubs are never going to have the same level of connectivity as CBD transit hubs, simply because intercity connections usually don’t generate enough ridership to justify these link on their own. It’s the same reason why the majority of BART trains entering San Francisco from the East Bay don’t travel to SFO – it’s just not that big of a ridership generator. Rather, to leverage the potential of connecting services, intercity trains must terminate in areas where there is already significant local and regional travel demand, i.e. the CBD.

          • cosmicbuzz

            For CAHSR, what is the time between San Jose and Sylmar? What is the rough cost breakdown for this route? Then we can do fair comparison between HL and HSR.

            Hard to find the information. Damn they will take my money. They deserve the curse every time.

          • Alon Levy

            First, destinations are extremely centralized. If you look at where the top hotels, convention centers, travel-generating office jobs, etc. are, they’re not distributed the same way across the metro area as the residences, or even the jobs. They’re far more concentrated. In the Bay Area this concentration is in Downtown SF and all over Silicon Valley. In LA it’s in Downtown LA and the Westside. The egress time is much smaller with HSR than with anything else even in more decentralized LA (there’s the Red Line and soon the Purple Line), and having multiple stations in each city center also helps. HSR can make stops in Anaheim for the tourists and Orange County residents, Norwalk for the Gateway Cities, LA Union Station for downtown and West Side travelers, and Burbank and Sylmar for the Valley, and in each case the loss of speed is small.

            Second, re continuous boarding, airport security lines are also continuous. At major airports, the time spent waiting in line is much more than the gap between boardings. When it takes 40 minutes to clear security, as just happened to me at JFK (pro-tip: never fly out of Terminal 2), it doesn’t matter whether there’s a departure with 140 seats every 10 minutes or one with 28 seats every 2 minutes.

          • Joey

            Yes, that information is difficult to find now that the CHSRA fucked up their website and made many of the previous EIR materials disappear. But then again, it’s difficult to make any sort of cost comparison when the numbers for the other project are pulled out of thin air.

          • Adirondacker12800

            Second, re continuous boarding, airport security lines are also continuous.

            And there’s never 50 of them. Imagine trying to wedge 50 security lines into something the size of Penn Station in Newark or Union Station Los Angeles. Which are both bigger than what they are imagining for new build stations. And imagine the staffing costs.

          • Joey

            But imagine traveling at 1000 km/h. And imagine it costing less than $10 billion. We can imagine it so it must be achievable in the next ten years, right?

          • cosmicbuzz

            The data on San Jose to Sylmar are practically concealed from voters; CAHSR deserves distrust. When we modify HL open document and cost, at least we can convince people that roughly $15B debt will buy them “45minute Hayward to Sylmar for $20 and back home every night is just marvelous”. The open document is just great for us to learn how to save $5500/family and do more. We will convince voters to guard their money. Also, stop CAHSR to cause the severe harm of sprawling into water-less central valley. High density living is better.

            Many people know how to get around within LA area and SF bay area (via own car, car pool, rented car (could be $30), transit, taxi). Adding the 45minute Hayward to Sylmar for $20 and back home every night is just marvelous. $5500 extra debt, $100 rail ticket, and $100 hotel for CAHSR travel are just ridiculous.

            To improve LA and SF transit is a different local issue. It is related to costly last miles issue of CAHSR. Piling them onto CAHSR $70B+ eventual bankruptcy is very bad.

            Here was my reasoning on security:
            “Visualize this, 50 lines of security check lines can easily help 56 mostly pre-clearance passengers through per minute without much wait ” (and continuously into the pods)
            My argument is direct to the point and can be modified and optimized. Alon’s irrelevant reference of airport security is way off the point.

          • Joey

            1) “Most people know how to get around…” True, but that doesn’t mean it’s fast, cheap, or convenient. If you’re driving you have to worry about traffic on already-congested freeways. If you’re taking transit you are either going to have to deal with dismal (< 1/hr) frequencies or transfer at the CBD station anyway. Passengers care more about time spent waiting than time spent in motion, and more about access time at their destination (where they are less likely to have access to a car) than access time at their origin. HSR has the advantage of not only serving the main CBD transit hubs but also (as Alon mentions) several other points within the region at very little time penalty or additional cost.

            2) Here's something interesting. Read the last sentence of Musk's abstract. The $20 ticket price explicitly does not cover operating costs (maintenance, electricity, staffing, etc). It claims to cover the capital costs, but there’s something odd about that too – 7.4m pax/year * 20 years * $20/pax = $2.96 billion, which is far lower than the already unrealistic capital cost. So the ticket price isn’t going to be anywhere in that ballpark.

            3) The staffing and equipment costs for 50 security lines is, as Adirondacker says, going to be quite large. There’s a reason airports don’t do this.

          • Adirondacker12800

            But imagine traveling at 1000 km/h.

            I don’t have to imagine it. When I want to go that fast I get in a plane. People have been claiming faster, cheaper etc forever. .. when you have a dull afternoon to fill wander the archives of Popular Mechanics and Popular Science. Their are filled with plans that are going to be whisking us along at astoundingly low costs, for decades.

          • cosmicbuzz

            @Joey, Alon,
            You failed to coherently reason point-by-point, deliberately omitted the important points “$5500 extra debt, $100 rail ticket, and $100 hotel for CAHSR travel”, effect of willingness to pay for “45minute Hayward to Sylmar”, “sprawling”, CAHSR formula of fees, calculating 1-3minute labor cost of security persons (~$15/hour/person) and optimize number of lines. Go complete all relevant points to complete your comment, to respect other people’s time.

            All the comments are evidences that I always diligently and progressively addressed all important points (contended by others) and explore/innovate solutions and reasoning. I addressed all the most important points: “20,000 repetitive works of 30 meter section” “Comfort” “Safety” “Gap of air cushion” “Cost and benefit comparison”, “Voters’ money”, “Drastic difference made by near sonic travel (1 day round trip)”, “Local transit/last mile vs cost”, and many smaller points such as security check time. (didn’t address the heat issue though)

            There are overwhelming evidences (such as your saying “The reason I’m so intent on debunking this”) in this post showing that you won’t do complete, coherent, point-to-point reasoning. I don’t foresee additional useful debates in this post. Anyhow thanks for your challenges (better than idiots in other forums) that prod me and others to develop comprehensive, roughly-argued modifications to the initial draft (to make alpha 1.1).

            It was so much fun to get through the first round of brainstorm. I am sure many open source people also enjoy their first diligence on HL. I will compile all the points, solutions, and innovation I made here and send to Hyperloop working group.

            Diligence and sense of historical mission are all too common in silicon valley successes.

          • Alon Levy

            Yeah, and everything you said about “20,000 repetitive works” is pure guesswork. It’s not actually supported by construction costs elsewhere, neither of bridges nor of tunnels. Repetitive tunnel lining or bridge supports or whatever don’t cut costs this much. Everything else follows from the cost. CAHSR assumes $100 tickets to partially recoup construction costs and the debt incurred for it; a correctly costed Hyperloop would have the same issue.

          • cosmicbuzz

            Again, you never complete point-to-point in your arguments. My confident guess work based on converging solid existing robotic technology would make the final cost $15B feasible and much shorter travel time, voters are willing to wait few more years to see if the guess work will turn real or not, and save the $70B money at the meantime, for the better. I don’t want to repeat all my coherent points about cost/benefit and voters’s money, etc.
            ….Sigh, another waste of time.

          • Alon Levy

            I don’t, because you take one point and turn it into five points that look different. And I know you say there’s converging robotic technology, but where is it currently used for construction? There’s plenty of repetitive construction out there, so where’s the example of cost saving? How do we know the costs won’t octuple with all the debugging required of any untested technology?

          • cosmicbuzz

            You just don’t think through the points
            “voters are willing to wait few more years to see if the guess work will turn real or not, and save the $70B money at the meantime, for the better”
            One of my point is that guess work might not work, or might; (“turn real or not”) another coherent point says it worth the wait considering the huge money. You simply repeat my point of “it might not work”. That is incomplete argument.

            Points in my other comments implies that the guess work will not be mine, the open source/companies will rigorously invent the critical robots and greatly improve beyond the alpha.

            …Sigh, again.

          • simple-touriste

            “It doesn’t matter how many passengers there are per vehicle,”

            Actually it does.

            “but how many there are per unit of time.”

            Please explain.

            “And imagine the staffing costs”

            Which cost? There is no reason to even wait. Except to humiliate people!

        • Ricardo B

          Dear cosmicbuzz,
          sanity check: apply your route and your robots to a 350 km/h high speed railway built on top of pylons, instead of Hyperloop’s vaccuum tube.
          How does it compare in terms of travel time, capacity and and costs?

          You’re trying to brush away the route/g-force issue and the costs of elevated track issue as fixables, but then they’d also be fixable for HSR. And then you could bring the cost of CHSR project to 10M$/mile.
          This is what Alon meant by “proving too much”.

          Second, drawing routes on Google Map is, unfortunately, not enough to assess actual curve requirements.

          • cosmicbuzz

            Dear 😉 Ricardo,
            The reason why I mostly replied @Alon, @Joey because I think they follow all comments, and guess they might recollect the coherent points I made, though I now doubt if they do recollect fully. As least I do my part of recollection. Anyone or you who would read my prior comments and follow the logics could provide the answers as I would. Sorry that I really want to reduce repetitive debate and time. I will paste prior words/points. Searching for prior reasoning helps.

            RB> sanity check: apply your route and your robots to a 350 km/h high speed railway built on top of pylons, instead of Hyperloop’s vaccuum tube.
            How does it compare in terms of travel time, capacity and and costs?
            RB> You’re trying to brush away the route/g-force issue and the costs of elevated track issue as fixables, but then they’d also be fixable for HSR. And then you could bring the cost of CHSR project to 10M$/mile.
            This is what Alon meant by “proving too much”.

            — “@Joey
            For CAHSR, what is the time between San Jose and Sylmar? What is the rough cost breakdown for this route?” that was what I asked and searched, and got no answer, it is voters’ right to suspect the worst (re prior argument points of “Voters’ money”, CAHSR’s chronic hiding vs Musk’s day 1 open alpha1.0 & toward a1.1). If truth is revealed and convincingly cheap, I would reasonably agree that this portion of CAHSR is viable. Still, my “coherent” points: “sprawling” to Central Valley, “20million people in LA and SF. Scale of innovation”… , “45minute Hayward to Sylmar for $20 and back home every night is just marvelous” still carry weight, though not decisive. I really hate “sprawling to CV”.
            — Search for all the reasoning work I did on HL comfort, robot, etc., it clearly shows that they are not “brush away” reasoning time/work. Did you think about whether you have “brush away” reasoning points? (BTW, why no one respond to my point about smooth “3D G force graph”? That is exactly what OS people will have to do with computer aided design.)

            RB> Second, drawing routes on Google Map is, unfortunately, not enough to assess actual curve requirements.

            — “other open source people will optimize comfort/cost even better” I already implicitly agree with you 😉

            After covering “all important points” and “don’t foresee additional useful debates”, it became more of a matter about the effectiveness of online debates, especially about the “coherence”/clarity of argument points, and the negative effect of the lack of coherence/clarity, such as the huge waste of time on calculation of g. My double quotes “” on words highlighted the importance of coherence and wasteful repetition. In software we use even more symbols, mind map, diagrams… all types of shorthands, that do tasks better than mere human languages. I hope some evolution of web forum such as easily posting drawing/whiteboarding can come sooner and more common to help open collaboration and debating.

            Everyone has the urge to voice opinions and not measure effects. I have tons of opinions, but I discipline myself to always try to put forth facts and coherent reasoning points during debates. That is why I respond to Ricardo’s reasoning points, but not respond to Rico’s recent opinions, where there is no direct reasoning point; and not to Joey’s sarcasm (search for word “right?”). It is also why I stay away in other idiots’ forums, and show my appreciations in this post (search for “thank”).

            After covering all important points, sorry that my recent comments sound confrontational, but those are not personal attacks (personal attacks are description of a person without direct facts and reasoning). Without insisting on clear reasoning points I cannot continue in forum, because there will be no additional rational results for sane people. I have shown honesty/humility when lack of facts and reasoning, honest mind helps the quest for them. Eventually coherent facts/reasoning exert their immense power and effectiveness. It works very well for my work and life. I reuse arguments about fact and reasoning points, personal attacks, strength of fact and reasoning to help convince people to do positive and effective debating. Hope it happens more here.

            What remain interesting are Inductrack levitation and cost, the fuel-base compression, and heat issue. https://pedestrianobservations.wordpress.com/2013/08/13/loopy-ideas-are-fine-if-youre-an-entrepreneur/#comment-10697

          • Joey

            What exactly is it you want? Most of your major points have been addressed. You claim that no one else here uses facts, but you are the one who throws around hypotheticals without any evidence that they are feasible. Shall we go through it again?

            You have failed to solve the comfort issue. 0.5g is uncomfortable no matter what direction you are facing, and without visual cues it is all but guaranteed to make many people motion sick. Repositioning the passengers won’t help. This point I addressed very specifically. The only ways to solve it are (a) to increase curve radius, in which case you are base tunneling under the Grapevine and probably cutting through several Central Valley towns and wetlands, or (b) Decrease speed, in which case what’s the advantage over air travel?

            You have failed to demonstrate any aspects of automated construction which are specific to the Hyperloop concept. If you have found a way to built elevated tubes cheaply, you have also found a way to build elevated railways cheaply. What you also don’t know is that railway construction is becoming increasingly automated: precast segments of viaduct are lifted into place and tracks are laid on top mechanically. See Alstom’s Axionis Concept to see a bit of this (watch the video in particular). In general you have failed to demonstrate that Hyperloop would be any less expensive than HSR, except something about “other people will solve the issues.”

            You have failed to demonstrate that the issue of stability at high speed and low clearance can be solved effectively or cheaply. You have proposed magnetic levitation (maglev) with higher clearances, but then you are building maglev, which is not less expensive than HSR to build.

            You have failed to solve the last mile issue (or last 40 miles in this case). Serving existing transit hubs and multiple stations in a region is precisely the advantage that HSR carries over air travel. Compared to air travel, Hyperloop offers stations even further out and less accessible.

          • cosmicbuzz

            There is no additional reasoning points in your comment. If you don’t want to quote the complete, coherent points that I already made, I don’t have interest continuing wasting time as you do, just as why I stay away from other idiots’ forum. But thanks for some of your points contributing to the debate. I am very disappointed that even you cannot give rough cost breakdown of san jose to Sylmar for CAHSR.

          • Joey

            I am very disappointed that even you cannot give rough cost breakdown of san jose to Sylmar for CAHSR.

            I previously said that the information had become unavailable due to the CHSRA reorganizing their site. But it seems I was mistaken. See page 3-11 of the Revised 2012 Business Plan. The Bay-to-Basin construction phase is projected to cost between $41.3 and $49.0 billion in 2011 dollars (depending on the alternatives selected), or between $51.2 and $60.9 b YOE dollars (projected completion 2026 due to funding constraints). These numbers are from last year and may not be 100% up-to-date.

            BTW, if you want to make it easier to address your arguments on a point-by-point basis, there are a few easy ways to do this. If you’re quoting someone, use blockquote tags (you use them the same way as any other HTML tag). Break up each of your points into separate paragraphs and possibly number them. Look up existing terms for the things you are trying to talk about (inductotrack levitation == maglev, etc). It makes the entire discussion flow a lot better.

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  85. William

    Very interesting article and comments. One issue I did not see addressed specifically is the route along the I-5 which in quite a few places is NOT simply flat farmland. I’ve made that drive 3-4 times per year for the past 5 years, and here are some issues I see:

    – Much of the route is actually built into the foothills west of the I-5 / flat farmland
    – On those stretches it is not clear there is even room for pylons in between or along the I-5
    – There are several sections with significant hills, even before we get to the Grapevine
    – This includes a pass from Tracy to Dublin which would likely need a tunnel
    – The foothill sections include many miles of “tiered” I-5 roadway (one direction significantly higher or lower than the other) due to the hils
    – The Grapevine pass is a 4000 ft hill; would need significant tunnel
    – The Grapevine is at least a 25 mile stretch

    Having watched the delay / cost overruns for the “4th bore” on the Endicott tunnel here in the Bay Area I suspect any tunneling estimates in Musk’s proposal are vastly underestimated.

  86. Bob

    truly a “pedestrian” observation. Shooting down new ideas is easy. Coming up with solutions or alternatives is hard. The math in the article is weak at best. It has a class warfare type of undertone so I guess we know exactly what the motivations of the author are….

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  90. Christian Geiselmann

    Wouldnt keeping the necessary extreme accurracy of shape for the tube require supports similar to traditional rail?

  91. Aero

    It’s funny, because while you all sit online and criticize him, he continues to revolutionize multiple industries and make billions of dollars doing it.

    Why not go outside and try to do something useful, instead of replying to me that he hasn’t revolutionized anything all he’s done is blah blah blah?

    • BruceMcF

      If this was the kind of idea he was willing to build himself, those ad hominem arguments would be more compelling. But someone can have lots of good ideas and still have some stinkers, just as somebody can mostly spout nonsense but occasional get something right.

      Indeed, the past evidence OF those ventures you point to rather supports than undermines Alon Levy’s points.

      Elon Musk has a habit of designing with insufficient margins for error and then in order to be successful the designs with great regularity have had to move away from a physicists ideal toward an engineers safe operating margin. So pointing to those previous ventures makes it even more likely that this particular proposal is promising substantially more than can be actually delivered in the real world.

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    • Joey

      Putting linear motors in a tube is easy. Making a vehicle levitate stably at 1000 km/h in that tube is hard.

    • cosmicbuzz

      Thanks for sharing. It is so fun to watch a real thing, despite it is all within simple design and analytic visualization. There is no levitation as I thought there is no need to.

      http://techcrunch.com/2013/08/21/meet-the-original-hyperloop-for-rocks/ mention few points that are relevant to what I discussed:

      * “So we used the plugging of the pipeline to our advantage” is related to the on/off/partial piston effect I explored.
      * “use of eddy current levitation” is relevant to my idea of combining Inductrack, air cushion, internal wings to enlarge levitation gap.
      * “rugged wheels” relate to my mention of safety wheel.
      * “conventional gas turbine engines to power to the compressor”, I did not think about it. Lesson to learn.
      * “heat balance in the tubes”. I didn’t cover it in this post.

    • BruceMcF

      The expensive part of the pipe is the soft vacuum and the 700mph vehicle moving through it. not the linear accelerator. If it was continuous linear accelerators propelling a minitrain through the pipe at one atmosphere, rather than 0.1% of an atmosphere, at 100mph, it would be a lot easier.

      • Adirondacker12800

        If you are moving at 100 you don’t need the tube. Catenary is lot cheaper than linear accelerator.

  93. Christian Geiselmann

    Hi everybody,
    after reading thoroughly about 75 % of articles and comments published here, I really wonder why one aspect has not been mentioned at all, or only very cursory under the notion of “travel comfort”.

    To let you understand where I come from: I am a resident in Germany, and since I have been working for years in frequently changing locations, I am very used to using the German HSR system (named ICE, or “Intercity Express”). And of course it is not me, but many people like me who live and work at one place, but regularly have business in other places, ususally the larger cities. So, I am very well acquainted with the strengths and weeknesses of the ICE system. I also see the traveling culture that has developed around this high speed rail system, since it’s start some 20 years ago.

    Based on this experience, I can say: A travel time of about 2-2,5 hours from one large city to another is a comfortable time. People more often see the time spent in the train as time won, not time lost. This is because riding is very comfortable, and every seat has power supply to serve a laptop. That way, most business travellers just use the time sitting in the train (usually at one of the desks that are available) and do their clerical work, or prepare for the meeting they may be going to have in their destination city, or take notes from the meeting they just had.

    An example from my own life and work: For one year I had a half time employment in Hannover, and a half time employment in Leipzig; now, there is no really high-speed connection between these towns but more something like an traditional connection, but the important thing here is that the comfort in the train is similar, and travel time is exactly 2:40, i.e. the time envisaged for the CAHSR from LA to SF, right? For me, personally, sitting in the train on, say, Wednesday evening, to travel from Hannover to Leipzig, wasn’t lost time at all, but extremely useful for doing some work. The change of environment (from office to carriage compartment) had a positive and energizing effect; in the train I have a table, power supply, and I can have a coffee, or a beer, which I may have brought, or buy from the bistro in the train. Thus, the two and a half hours are perfect for doing some more concentrated work. In fact, those train rides gave a push to my overall efficiency.

    Opposed to that, squeezing myself into a 1,30 pod, with even not the possibilty to stand, to move, or use a toilet, is not an attractive alternative. Moreover, the (alledged) time of 35 minutes from point of start to point of arrival is not enough – even if laptops can technically be used – to start some serious work. You need some time to settle down and to mentally adjust to where you are, to open your computer, to open your documents, and so on. And at least 5 minutes before you arrive, you have to stow away your computer or what ever stuff you are working with. So, a 35 minutes ride from start to destination will be lost time in any case. And then, as you obviously are not in the city centre, but somewhere in the outskrits of a megacity, you will have to take some other means of transportation, and spend again time in it which will be lost time, not time won.

    There is an additional thing to consider: People aren’t moles. People want to see landscape, sky, trees, hills, or whatever the region provides (and be it a desert). They want to look out of the window, especially when traveling. Even airplanes provide this opportunity (with the advantage that flying lets you see the sun, even on a cloudy, dark winter day). Sitting for 35 minuts in an entirely closed pod is an extremely unattractive prospect to me, and I believe, to other people and commuters, too. (By the way, the comfort of seeing daylight is one of the reasons why people often prefer going by car, even in large cities where the underground would provide quicker service.)

    Engineers and business people sometimes seem to underestimate the fact. In Germany, we have these years one notorious railway development project: replacing Stuttgart central station (rail head type) by a completely new underground station (pass-through type). This project was designed by politicians and technocrates (the public was included extremely late), the real motor actually being not travel comfort, but mere greed to sell the huge areas of land in the city centre occupied by the rail yard serving the rail head. The Stuttgart central station project is a drama in itself, completely useless, at costs of billions of euros; its stupidity even contributed to chasing the conservative government of this German province out of service (after 50 years or so of unchallanged power!), and handing government over to a provincial prime minister of the Green party. This was unprecedented.

    Well, Stuttgart main station a completely separate story.

    But based on my experience as a frequent traveller in the German ICE, I would recommend in California be built a HSR system, not a windowless pneumatic pod gun with all its conceivable discomfort. And, no, I do not have stock in the business, really. I am speaking solely as a passenger. And yes, I am in favour of new technology (where it makes sense); the best thing I have seen in this respect in recent years being the Pedelec – a bicycle with an intelligent system of electro support that enables you to get to your destination in half the time with 1/4 of the physical effort compared to a traditional bicycle, including climbing hills that you would not take otherwise, and at energy costs of, say, 20 cent per 30-50 km. Now, THIS is progress!)

    Kind regards,
    And thanks for all the very meaningful and well presented arguments, which are a joy to read.

    Christian Geiselmann
    (Leipzig, Hannover, Munich, and Sofia (Bulgaria)

    • cosmicbuzz

      Very well written comment.

      Your point of “comfort, productive riding time” do carry weight.

      My points about “Voters’ money”, “last mile cost”, “sprawling” to Central Valley, “20million people in LA and SF. Scale of innovation”… , “45minute Hayward to Sylmar for $20 and back home every night is just marvelous” also carry heavy weights too. Sorry I do not want to repeat these reasoning (searchable) words in my prior comments.

      Social effects are soft and hard to measure and predict. Cost and economics are hard, and usually dominate hugely costly project like this.

      • BruceMcF

        “sprawling to the Central Valley” can’t be accord any weight, since its such an evidently absurd framing of sprawl. Someone moving from an outer suburb on the edges of LA County to an infill development in Fresno would clearly be reducing sprawl. Its even sillier when saying it in a forum like this one, which will have a relatively high proportion of readers who realize that the only directly sprawl-inducing station in the California HSR system was removed, at the insistent of several environmental groups, long before the program received its federal funding. Indeed, putting your sole LA Station in Sylmar is far more likely to induce sprawl than having a station in the center of a range of Central Valley cities with populations in the hundreds of thousands, serving an existing population in excess of two million.

  94. Rico

    Comicbuz, the sighing is a nice touch but misses the point. Your comments are pure unadulterated fanboy. There is no evidence that your ideas have a snowball in hell’s chance of coming to furition in the near future….and if the robotic construction world does advance to the stage you believe it will be just as usefull to HSR. The only thing this current proposal does is provide ammunition to people trying to kill HSR…in fact that is almost certainly its purpose.

  95. Phlebas

    This is one of the most devastating counter-essays I’ve ever read – I’m bookmarking this blog!

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  99. John Kopp

    I found this site while searching for tunneling costs. A couple of observations about hyperloop.

    First, using the proposed design of the tubes, the amount of steel required would cost almost $2 billion. Fabrication and installation would probably double that. The tube will span the 100 feet between pylons, but would sag about 1/2 inch under load. This would result in a vertical curve of radius 6 miles and an acceleration of 1g or greater. The span has to be stiffer, and tolerances are very small, less than a quarter inch between pylons.

    Cost of construction of a bridge on pylons is at least $50,000,000 per mile through the Central Valley, and 200 to 300 million in the mountains and urban areas. This would bring construction costs of the tube infrastructure only to about $50 billion, not including vacuum pumps, linear propulsion motors, solar panels, vehicles, and development costs.

    A comparable ride for comfort would be Space Mountain at Disneyland, but continuing for 30 minutes.

    Applying Musk math to CAHSR, one could run 10 trains per hour in each direction, carrying 1200 passengers each, for a total of 105 million per year in each direction. Amortizing over twenty years, gives a ticket price of $16.50 each, $3.50 less than hyperloop.

    • Falstaff

      ” the amount of steel required would cost almost $2 billion.”

      Could you expand on that determination? The proposal calls for 2.2 m OD steel pipe, 0.9″ walls, for the passenger only version. Probably 100′ sections. Your price comes out to ~$500/ft (two tubes)?

      • John Kopp

        I used a tube diameter of 88 inches ID (7’4″) and thickness of 0.9 inches. This gives a cross sectional area for the tube wall of 251 square inches, or 1.75 square feet. Using a density of steel of 490 pounds/cubic foot yields 855 lbs per foot of tube length, or 2,258 tons per mile. For 399 miles and two tubes, this results in 1,800,000 tons. I used a price of $1,000 per ton which was about the price six years ago when construction was hot. Today’s price maybe more like $800 per ton, which would give a price of $1.44 billion. But I looked at the proposal again, and on pg. 27, it mentions reinforcing the tube with stringers. I assume this is the stiffen the tube, and am guessing they would add an additional 40% to the total steel required. This would double the stiffness of the tube, resulting in less vertical sag. That said, then the price of the steel would range from a low of $1.44 billion with no reinforcement, to $2.5 billion or higher. Then one must add the cost of fabrication and installation. Certainly several times their cost estimate of $660 million. It looks like they didn’t even attempt a reality check.

        My reference is AISC Manual of Steel Construction, Load & Resistance Factor Design, Volume I, Second Edition. Steel costs from various internet sites.

        • Falstaff

          Thanks, I think that’s a valid approach, with a couple caveats:
          1) The proposal apparently uses 350 miles (563 km), total length, two tubes (pg 26)
          2) The price of steel today is $650/metric ton. It was largely the spike in the price of oil that also spiked steel prices ~six years ago. [1]
          At that steel price and length, with 1.32 mt/meter , I have $965 million for steel tonnage both ways.
          [1] http://wsj.com/mdc/public/page/2_3023-cashprices.html

          • John Kopp

            1) I used mileages from the proposed route, pg 44-50, which showed 354 miles plus 45 miles listed as additional required. Very confusing, I’m not sure what was meant. Straight line distance between SF and LA is about 350 miles, but this proposal goes to suburbs far from the city center. An additional 45 miles would connect city center to city center.

            2) Thanks for the WSJ link. I used the cost of rail which I had found earlier. Other steel costs I linked to were not useful and couldn’t find the WSJ on line. Steel prices were high 6 years ago because China was in a major construction and manufacturing boom. In fact, they had contracted to reopen a large taconite mine in Minnesota which had closed in the 1980’s. With the world wide downturn, demand and prices have retreated.

          • Falstaff

            I’m curious to know if Musk et al consider alternative materials for the tube.

            By far the single largest line item cost in the Hyperloop proposal is the pylons: $2.6B, reinforced concrete, with the actual tube cost far behind at $650 million. The pylons are specified as one every 30m or 25,000 in total, 6m tall typically.

            It may be that a method for reducing the pylon cost is to use an alternative material for the tubes. The tube material is steel (22 mm wall, 2.3 m ID). Carbon fiber reinforced polymer, for example, would be more expensive than steel, as will any steel alternative, but the advantage is that CFRP has a specific strength ten times that of steel. A CFRP tube then attacks the high cost of pylons, likely enabling increased pylon spacing, and reduced pylon size, thus reduced pylon foundation mass, reduced construction transportation costs, etc.

            I can’t readily find information to bound the cost of a CFRP tube. The steel tube works out to 1.3 metric tons per linear meter of tube (22 mm wall, 2.3 m I.D.), with steel currently at $650/ton.


    • Falstaff

      I’m curious to know if Musk et al consider alternative materials for the tube.

      By far the single largest line item cost in the Hyperloop proposal is the pylons: $2.6B, reinforced concrete, with the actual tube cost far behind at $650 million. The pylons are specified as one every 30m or 25,000 in total, 6m tall typically.

      It may be that a method for reducing the pylon cost is to use an alternative material for the tubes. The tube material is steel (22 mm wall, 2.3 m ID). Carbon fiber reinforced polymer, for example, would be more expensive than steel, as will any steel alternative, but the advantage is that CFRP has a specific strength ten times that of steel. A CFRP tube then attacks the high cost of pylons, likely enabling increased pylon spacing, and reduced pylon size, thus reduced pylon foundation mass, reduced construction transportation costs, etc.

      I can’t readily find information to bound the cost of a CFRP tube. The steel tube works out to 1.3 metric tons per linear meter of tube (22 mm wall, 2.3 m I.D.), with steel currently at $650/ton.


  100. StephenH

    Good article, but I think you’ve gone off-track in your update.

    A 47% wider tube costing 17% in itself doesn’t look like an error. Many of the costs associated with tunnelling are fixed, or do not increase linearly with tunnel diameter (though some costs may increase more than linearly).
    If a 47% bigger tube was forecast to cost 47% more, that would be fishy.

    • Alon Levy

      I don’t think it’s an error. I think it’s an indication that the argument that it should be cheap because the tube is narrow or light is wrong.

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  102. Nathan Wilson

    I don’t buy the argument that weight only weakly effects cost. Surely cost savings is the main reason that cities choose light-rail over conventional (heavy) commuter trains, and cost savings is certainly the main reason anyone ever chooses narrow-gauge rail (which has light weight as an attribute alongside the narrowness).

    The small cost difference in the Hyperloop study can be explained in part by the fact that Musk assumed that the capsule does not grow much in weight due to the wider freight clearance: only 10%, this means that the dynamic loads are only slightly higher in the wider case. Also, note that the pictures don’t show the size of the stringers which reinforce the tubes; it may be that wider tube needs less reinforcement.

    Hyperloop aside, it seems to me that very-light high speed rail (VL-HSR) has the potential for significant cost savings compared to traditional HSR. Even if the cost savings was eroded by the need for larger and more expensive stations in order to serve high-traffic routes, VL-HSR would be much more likely to get deployed in low-traffic area (where conventional HSR would never happen).

    I’m imagining small trains with standard gauge wheels, so they can run on existing track, or on new very-light track. Speeds in the 120-150 mph range would be adequate to take market share away from cars, as long as we build the required overpasses and passing-lanes to get past the freight traffic.

    For size, I would note that when people spend their own money, they end up with things like mini-vans and business jets which have much smaller cross-sections that buses and regular trains (but bigger than Hyperloop’s 4.5’ width). My mini-van is 48” from floor to ceiling and 60” wide, and business jets start at about 54” inner diameter (see Cessna Mustang). For a VL-HSR interior, I would suggest 5.5’ high and wide with two seats per row with a center aisle (this could easily be under 1/3 the weight per unit length of conventional light-rail, and shorter cars could reduce the axle load another 2x). The low ceiling would be acceptable if people don’t have to walk far, so maybe it needs one door every 12 seats. If the trains have no crew (other than perhaps an engineer), a total capacity of 60-120 seats might be good.

    For me, the worst things about Amtrak are that it is slower than a car, and only comes once per day.

    • Alon Levy

      Light rail vehicles are not lighter than heavy rail trains (which are not the same as commuter rail trains). Light rail is lighter in capacity and costs less insofar as it’s built at-grade, but the vehicles weigh the same per unit length, and the total length of the vehicle is irrelevant for cost. For example, bridge loads are quoted in axle load or weight per unit length rather than total weight. In Germany, bus-sized rail vehicles are used not for the lower infrastructure cost but for the lower vehicle cost – they consume less energy per vehicle (though more per unit of capacity) and cost less to build, which saves money on very lightly-trafficked lines.

      Your proposal for very light trains is something that goes back to the 1830s or 40s. People at the time opposed railroad monopolies and said they’d be more supportive of railroads if people could just drive their own carriage-sized trains on them. It was rejected then and continues to be rejected, because the physics of railroads – easy combination of cars into trains, and long stopping times – favor long vehicles. A railroad will never be able to run vehicles a few seconds apart the way highways do, and a highway will never be able to run 400-meter vehicles the way railroads do.

      • Nathan Wilson

        Ok, I’ll accept your word on light rail. But the existence of narrow gauge still supports my belief about potential cost reductions with lower weight (especially with maglev or evac tubes or other dedicated infrastructure).

        The physics of railroads you describe, particularly the long stopping time, is a design choice. I understand that most passenger services have a strong incentive to interwork with legacy equipment, particularly freight. But when talking about new system, like Hypertube, Maglev, and VL-HSR, new possibilities will appear. I’m not claiming vehicle spacing like freeways; I understand that when trains merge onto tracks, track switch time must include the full stopping time (in case the track doesn’t switch). If a train slows to 30 mph to pass through a switch, then certainly it could be designed to stop in 10 seconds, if it takes 3 seconds to pass, and the switch takes 3 seconds to change, then that switch can handle one train every 16 seconds under computer control. Add another 10 seconds and even a human could drive it. 72 passengers every 26 seconds is 2.8 p/sec=10,000/hour, about like a 4 lane highway. Of course a station would have to have many boarding areas running in parallel to launch trains that fast; but that is a design choice that is very different for long distance system (where most of the cost is in the track) compared to city systems (where the stations are a bigger part of the total).

        But again, the big advantage would be for systems which did not need the high passenger throughput. Because of the importance of standardization, it is important that the system is scalable, which I believe it is.

        Is there some other issue with rail that makes 26 second train spacing problematic? (which isn’t solved by automatic control and hazard detection?)

        • Adirondacker12800

          The main problem is that something going 700 mph can’t stop in 26 seconds? Not if it has passengers in it.

          • Nathan Wilson

            Right. Probably 60 mph of speed change every 10 sec (which is 0.28 G, or 117 sec to stop from 700 mph) is about all you’d want (based on a familiar automobile acceleration). But personally, I’m skeptical that a 700 mph train could really be affordable, compared to the 150-300 mph range, but I am open-minded.

            But there is no need to go through track switches at full speed, it would make the switch design impossible, with a huge turn radius. That’s why I suggested the train or capsule should slow to around 30 mph before going through switches; if all trains slow down as they reach the same spot, their minimum time spacing is set by their stopping distance at the switch, not the straight sections of track.

            As with freeways, it would be nice to have limited access; due to the long accell/decell time, the trains should not have to slow down more often than every 20 minutes or so for merging tracks.

          • Joey

            The best switches today have no speed limit in the straight direction and around 230 km/h in the diverging direction. They’re long but they don’t take up much space otherwise. I don’t know where you’re getting 30 mph from. Also, line capacity is determined by emergency stopping distance at full speed at any point along the track, not just at switched.

          • Falstaff

            “The main problem is that something going 700 mph can’t stop in 26 seconds?”

            Why not? That’s 31s to stop at 1g, 15s at 2g, etc. Not comfortable but unreasonable for an emergency.

          • Joey

            It’s acceptable if passengers have seat restraints similar to roller coasters engaged for the entire duration of the trip. Otherwise people are going to get injured (or worse) during sudden deceleration.

  103. Nathan Wilson

    230 km/h for switches is impressive; but it will place an upper limit on line capacity, provided that other limits are eliminated. The emergency stopping distance rule is does not apply to freeways, and need not apply to specialized rail.

    For freeways, the car spacing is limited by driver reaction time (since every car has about the same non-emergency stopping distance as the car in front of it). The emergency stopping distance rule only limits speed (not following time), since cars must be able to stop for an obstruction after they see and react to it.

    For a computer driven train, the minimum following time is the based on the emergency stopping time for a switch (the train must stop if the switch fails in the wrong position), and slowing down for every switch can make stopping time as short as desired (hence my arbitrary selection of 30 mph). If the train has the same emergency stopping distance as the train in front of it, again the reaction time rule applies. A computer networked train can see stationary obstructions far in advance using stationary cameras, so these do not limit following time.

    Obviously, this does not apply when a train is operating on a track with legacy freight traffic, only on purpose-designed systems with only high performance trains.

    • Joey

      Safe stopping distances aren’t maintained on freeways because drivers don’t care about them and they’re difficult to enforce. Most driving safety classes tell you to maintain a much larger distance than people do in practice. On transportation modes where safety isn’t in the hands of the general public, a safe stopping distance is maintained at all times.

      And it’s not as much of a capacity constraint as you seem to think. AFAIK France is upgrading the LGV Sud-Est to allow 18 tph. The design specs for California’s system call for a maximum allowed headway of 5 minutes, but this is really to allow capacity-eating overtake maneuvers to take place, not the fact that we will actually need 12tph any time in the foreseeable future.

      • Nathan Wilson

        When I took driving class, I was taught to use a 2 second following distance in good weather, and to limit my speed at night so as not to “over-drive” my headlights (i.e. my stopping distance must never be greater than my headlights can reach, so I don’t hit cows, etc). The stopping distance rule applies to stationary obstructions (that’s why I suggestion stationary cameras or fences to keep obstacles out), not other moving cars.

        18 trains per hour may be good for big trains, but were are talking about small trains as with Hyperloop, in which case 120 train per hour would be desirable. I still don’t see a reason this won’t work.

        • Joey

          Because mitigating crashes is a necessary design parameter, and part of that is avoiding more deaths from cascading crashes.

          • Nathan Wilson

            Ok, now it’s getting specific. This statement assumes that a trains stopping distance is shorter in a crash scenario than the emergency stopping distance. This is certainly untrue for automobiles with anti-lock brakes (except in the case of collisions with stationary obstacles, which again could be prevented with stationary cameras or fences); skidding or even rolling decrease friction. Whether or not it’s true for a hypothetical new train is completely up to the designer and customer.

          • Joey

            Could you be more specific about what distances you’re talking about? Without a doubt, the emergency stopping distance is going to be shorter than the stopping distance in revenue service, but it’s the emergency stopping distance which is going to define the headway between trains. And the emergency stopping distance is still limited by the fact that passengers must not be injured during the deceleration.

  104. Nathan Wilson

    Ok, say two trains are racing down a Hyperloop tube, with the minimum allowable time separation between them. The lead train, train-1 has a malfunction which causes it to stop very quickly; train-2 wishes to stop before hitting train-1.

    What is the minimum allowable time separation which allows train-2 to stop in time?
    The robust answer is the (reaction_time + (stopping_distance)/(speed)), for all scenarios, real and imagined. In the special case of the low friction Hyperloop with computer control over the brakes on both trains, the trains can be designed to stop faster in the absence of malfunctions! In other words, the safe minimum time separation is equal to the reaction time, which is negligible with computer control. That’s why I claim that the actual limit only appears around track switches, which can fail instantly (hence the proposed solution of slowing down to satisfy the stopping_distance/speed requirement at the switches).

    But even in the cases where this argument doesn’t hold (e.g. tube failure), combining two small trains into one larger one (in the name of stopping distance) does nothing to improve safety, since the same number of passengers are at risk in either case.

    • Nathan Wilson

      Correction, the robust answer is (reaction_time + (stopping_distance/(speed/2))), which works in the case of the lead-train stopping infinitely fast, and/or leaving the track beneath it unpassable. Of course, stopping_distance is itself a function of speed^2.

      • Joey

        Ultimately it’s better to write it as a function of acceleration, which is what matters as far as passenger safety is concerned anyway. Plus the calculation is simpler.

        And re: longer trains, I agree completely, it does nothing for safety directly. But it increases capacity massively, which is the main reason why it’s important.

  105. Jacob

    With regards to energy use and aerodynamics. A stimulation firm has now run tests on the capsule/pod:


    People listen to Musk because he has slashed the cost of space rockets and electric car batteries. Tesla use cheap commodity casings for its batteries while Nissan use custom-made batteries:


    The cost of building pylons could possibly be slashed by pre-fabricating them in China and shipping them to wherever the Hyperloop is to be built. A bridge in San Francisco was partially built in China to cut costs:


    • Alon Levy

      The bridge that was partially built in China cost $6 billion for a couple of kilometers. It’s the Big Dig of the West, only above ground.

      • Falstaff

        Yes $6 billion. Was the point about a) possible cost savings from importing some tube components, or b) the cost of a 160 m high bridge with 704 m spans and 10 traffic lanes across the San Francisco Bay?

        • Alon Levy

          The point is that a) isn’t a game-changer; the cost savings are already baked into existing projects that I’m comparing the costs of Hyperloop with.

          And don’t forget – Hyperloop would need such a bridge or tunnel to get to San Francisco, too. Without that it has every drawback of flying.

          • Falstaff

            At a little over one ton per meter per tube it is very likely that either the Oakland or the Golden Gate bridges are structurally capable of piggy backing the tubes, perhaps under the roadway. The possibility is not something to bring up in a concept proposal as it would detract from the main thesis.

          • Alon Levy

            First, dynamical loads. Second, I think the ability to get into San Francisco proper is important enough that it should be part of the main thesis.

          • Adirondacker12800

            I would think first is that the Golden Gate bridge isn’t particular useful if you want to get to Los Angeles from San Francisco. It’s not even particularly useful if you want to get to Oakland.

          • Joey

            We’re looking at several hundred million dollars just to add a bike path to the west span right now. The cost of adding something to the bridge might be smaller than the cost of a new tunnel but it’s not trivial.

      • Jacob

        Do you have anything to say about the recent computer simulation tests done on Hyperloop?

        Or is Sandeep Sovani a liar too, when he says “I am pretty convinced Hyperloop is feasible”.

        • Alon Levy

          I’ve never said it’s infeasible. I’ve said that the cost projections are fraudulent (and have backed this up with a fair amount of evidence of real-world construction costs) and the passenger comfort levels make airplanes look good.

          • Jacob

            So it could be feasible but cannot be financially viable?

            The CGI photo of the Hyperloop looks as if it is a glass tube. Yet the 58 page document never mentions the word “glass”! That is very dishonest. If the entire system is in steel tubes, a lot of people wont want to use it.

            It would be great if Musk could slash the cost of Maglev, like he slashed the cost of space rockets and electric car batteries. Because unlike Hyperloop, maglev has already been built and is not in claustrophobic opaque tubes.

          • Falstaff

            “said that the cost projections are fraudulent (and have backed this up with a fair amount of evidence of real-world construction costs)”

            Which real-world construction costs? Your cost argument was essentially that the cost of “viaducts on California HSR”, bridges, “elevated highways and trains”, and elevated urban rail are X, therefore Hyperloop costs are X as if they were the same thing. HSR is a train; Hyperloop might compete with HSR, therefore, per the article, Hyperloop is a train. There is no comparison to the costs of, say, the right-of-way of elevated HV electric power or telecom transmission, or the construction of water/gas pipelines.

            A serious comparison of the construction similarities *and differences* between HSV and Hyperloop might have been done. Instead the article roamed into the vagaries of fame, defamation of Musk (“crank”, “fraudulent”, “surrounded by sycophants and stenographers”), and assumed knowledge of the minds of others (” think they can do anything”)

          • Alon Levy

            Read the post that looks at the costs of lighter, sleeker structures than standard trains. There’s no difference. It’s not and never been about weight, and the idea that you can construct very high-speed passenger transportation at the same cost as leaky pipelines suggests very strange views of passenger safety.

            Musk is welcome to sue. My defense will be truth.

        • Falstaff

          “There’s no difference. ”

          That’s provably not the case for *at least* the right-of-way costs. Elevated structures like transmission lines allowing ample cross path traffic and minimal ground disturbance have a fraction of the right of way costs of ground level equivalence. See right of way costs from e.g. costs from American Electric Power (AEP).

          • Joey

            1) Right-of-way is a small fraction of overall costs. Unless you’re building in highly developed urban areas, acquiring more land is usually cheaper than building more structures.

            2) Viaducts are expensive, regardless of what’s put on top of them. The cheapest way to build is usually to build at-grade and then build underpasses or overpasses (usually overpasses) for roads. This approach is often considered undesirable because it’s disruptive. The next cheapest way is usually to fill in with dirt (without retaining walls or with, for slightly more cost, in space-constrained areas), and build short structures over the roads. Viaducts are even more expensive – unsurprisingly, bridging the columns requires a fair bit of steel or reenforced concrete.

          • Adirondacker12800

            But isn’t Hyperloop going to be built out of Reardon Metal? I’m sure Ms. Taggart can arrange it. After all they are going to run the evacuation pumps with Galt generators aren’t they?

          • Falstaff

            “Right-of-way is a small fraction of overall costs.”

            Right of way cost for what? Elevated trains or elevated pipelines? According to who? The Hyperloop proposal has right-of-way (“land/permits”) at one billion, or 17% of the total passenger system. That’s roughly in agreement with HV transmission line right of way costs for ~350 miles.

            “Viaducts are expensive, regardless of what’s put on top of them.”

            Viaducts with nothing on top are just a series of pylons and pylon cost is design dependent. The Trans-Alaska pipeline system cost $7-8 billion for *800* miles of 48″ pipe, 420 miles of it elevated 1.5m to 5m above ground on 78,000 pylons.

          • Alon Levy

            Right of way for HSR, according to California HSR unit cost estimates and any attempt to pencil out the value of rural land. (Take the yields of the highest-value farmland, multiply by retail cost rather than profit to the farmer, multiply by a generous width, and it’s still in the low hundreds of thousands of dollars per route-km.)

            The Trans-Alaska pipeline is one pipeline rather than two tubes and the pipeline’s diameter is about 40% of the diameter of Hyperloop. If you believe that it’s all about reducing structure weight (even though that doesn’t actually save any money, see monorail vs. conventional rail or slab track vs. ballast), you need to multiply that cost by 5. And that’s without taking into account different design standards for low-speed oil versus high-speed transportation.

          • Joey

            Indeed. Oil doesn’t care if the pipeline sags a bit between supports. Oil doesn’t care if the pipeline is a few cm off of alignment (let alone fractions of a millimeter). Usually no one dies if an oil pipeline springs a small leak or shakes during an earthquake. Oil pipelines don’t have to worry about getting passengers out through a vacuum in an emergency.

          • Adirondacker12800

            Oil, like electrons, doesn’t have a minimum curve radius..

          • Falstaff

            “The Trans-Alaska pipeline is one pipeline rather than two tubes and the pipeline’s diameter is about 40% of the diameter of Hyperloop.”

            Yes, certainly. Other differences include a route twice as long (half buried but pipe is pipe), a half ton of crude per meter along the entire pipeline, hundreds of pump stations, dozens of river and steep terrain crossings, and construction in the Arctic wilderness.

            “(even though that doesn’t actually save any money, see monorail vs. conventional rail or slab track vs. ballast…”

            Rail whether monorail or slab track is not pipe.

          • Falstaff

            “Oil, like electrons, doesn’t have a minimum curve radius..”

            Pipe doesn’t have a 25′ right of way each side of center (at least), as does rail, nor cut cross property transit in half for miles. Straddling properties can be swapped or otherwise negotiated for rail, but then arrangements can be made for large radii as well.

          • Joey

            Rail whether monorail or slab track is not pipe.

            It is in that it has non-negligible weight.

  106. Tony Alvarado

    The Hyperloop looks to be an exciting option for fast distance traveling, but similar to current public transportation options like San Jose’s light rail system or Caltrain, it relies on the public to travel to and from specific destinations. Our BiModal Glideway would be a better solution as it would provide the same high speed distance travel, but allow drivers the freedom to go from door to door during their commute.

    • Jacob

      BiModal is a waste of energy. Using a 1.5 ton car to carry 1 passenger.

      How about building SkyTrans PRT instead. It can be erected in narrow spaces using pre-fabricated pylons made in a factory.

  107. David Peters

    For the naysayers like this writer: You are correct:

    –A small company competing with NASA will NEVER happen.
    –A flyback first stage booster is to expensive to build.
    –Private companies cannot build rockets for a fraction of the cost NASA charges.
    –Electric cars must get massive subsidies to be profitable.


    Even if he is off on his price estimate by 500% the hyperloop is STILL MUCH BETTER than high speed rail. MUCH. The cost is practically nominal! We could build 5-10 hyperloops for JUST the price of the California Maglev Rail project. We could have connected the 200 largest cities in the U.S. AND provided FREE travel FOREVER for 1/2 the price of the “stimulus” bill. THAT would have been REAL stimulus! Imagine the economic activity it would have created! The ability to live in Chicago and work in Detroit or Kansas city? The ability to travel from San Diego to LA for lunch? THAT would have been ‘shovel ready.’

    This is NOT a new idea. All Musk did is make it actually feasible by adding his rocket technology experience (from SpaceX) and his electric battery experience (From Tesla) and then packaged it into a complete product. Nobody has EVER done this before and the response is his effort represents ‘back-of-the-napkin’ calculations?

    This author would have opposed railroads because they cut into the pony express. He would have opposed motor vehicles because they disrupted the horse crap pick up people. He opposes hyperloop because he has financial or personal interest in high speed rail. This is NOT credible.

    • Nathanael

      I happen to know why SpaceX was able to build rockets cheaper than NASA. It’s because NASA used pre-computer technology for control circuitry and SpaceX used silicon chips.

      This very real advantage doesn’t apply to Hyperloop.

      As for Tesla, it was always obvious that electric cars could be profitable. The business model was trivial and was figured out in the 19th century, and was already working in the early 1900s. In the 1910s and 1920s, there was no rural electrification, electricity was expensive, and gasoline was incredibly cheap (it was a waste byproduct of kerosene refining), which caused electric cars to lose out. We got rural electrification (in the 1930s), and gas stopped being cheap (in the 1970s). After that, cars like the EV1 sold like hotcakes. But then electric cars were suppressed actively, for essentially political reasons, by gasoline companies and “gas car” companies. Tesla is just a matter of doing the bleeding obvious.

      Hyperloop is simply fantasy and will not work for the fantasy price. Hyperloop is NOT credible. It’s worth noting that at Tesla, Elon Musk routinely lowballs price estimates on things he’s *researched* by factors of 2 due to huge optimism bias — and in the Hyperloop case Musk simply hasn’t done his research at all.

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  109. Joey

    I’d just like to point out that this post was linked in a Cracked.com article recently. It’s in the sentence “The Hyperloop needs a perfectly straight, elevated track built on huge pylons that would cost roughly 10 times as much as Musk predicts,” where italics stand in here for the link.

    • John Kopp

      I see that Hyperloop Transportation Technologies has a civil engineer as one of the principles. Hopefully there will be some realistic estimates and time lines for this.

      My thoughts on construction costs are that the tube structure is essentially a bridge built on pylons and my experience is that the cost would be about $50 million per mile through the Central Valley. Most of the valley is alluvial fill and lake deposits, and pylons will require extensive foundations. Cost would be $11.35 billion for the 227 miles through the Central Valley.

      Because the San Francisco and Los Angeles sections go through mountains and urban areas, typical costs seem to be about $300 million per mile, making the SF section of 74 miles cost about $22.2 billion.

      The LA section of 53.4 miles would cost at least $16 billion. But this crosses the San Gabriel mountains which is the fastest growing mountain range in the world. The project will cross the San Andreas fault, the San Gabriel fault and a number of thrust faults. This will no doubt add several billion dollars to the cost. Perhaps $20 billion for this section may be required, if it’s is possible to even build it.

      Cost of the tube structure would thus be about $54 billion. Cost of vacuum equipment and linear motors may add another $5 billion. The $6 billion quoted may be enough for design and engineering studies.

      • Adirondacker12800

        6 billion for prototypes to assure that when the pod crashes into the side of the tube it doesn’t burst through and it keeps the splattered passengers inside the pod not scattered over a mile and half of pasture.

      • Falstaff

        “the tube structure is essentially a bridge built on pylons “

        An automobile bridge? A tube is 2.3 m OD. Why is a pipeline not the better approximation (times two)? The Alaska pipeline, half elevated on pylons, was $10 million per mile, built in the Arctic.

        • John Kopp

          It’s a transonic passenger transport vessel bridge. Pipelines do not transport people, bridges do. Think of it as the bridge beams are round cylinders that the vehicles travel through. My crude analyses indicates that the tubes are not stiff enough for the high speeds and need to be reinforced with additional steel, or reinforcing beams. If they were regular I beams, they wouldn’t need as much steel.

          The Alaska pipeline was built almost 40 years ago, and steel is more than five times more expensive now. So cost of Alaska pipeline today would be $50 million per mile. But that’s only one pipe, not two. So, Hyperloop may be 100 billion?

          • Falstaff

            The idea is not to find the best metaphor, but the best model of existing construction that best approximates the HL requirements. Asserting, aha, I know bridges, therefore this is a bridge, therefore it will cost X does not educate anyone.

            *How* is the HL like a bridge in any significant way? It is elevated, yes. Large bridges have a mass of some 200 tons/meter, width 25 meter, span maybe 1200 meters between supports requiring extraordinary construction techniques. The HL is one ton/meter per tube, 5 meters wide, with spans between pylons than can be set with a crane.

            Also, the Alaskan pipeline cost was not remotely dominated by steel alone. And you earlier estimated the total HL steel cost at $2 billion. (@$650/ton it is $1 billion).

          • Joey


            It’s less like a bridge and more like a small viaduct, but even that fails to capture the cost of getting it within sub-mm alignment tolerance (which oil doesn’t care about and cars don’t really care about), and keeping it there in the event of an earthquake for instance. Do oil pipelines require active shock absorption?

          • Falstaff

            @Joey: “Do oil pipelines require active shock absorption?”

            Shock tolerance, yes, in places like Alaska which is far more geologically active than California.

            I’m not sure where the “sub-mm alignment tolerance” might come from. Recall the proposal for the vehicle has no contact with the tube when in motion.

          • Adirondacker12800

            No contact with the wall until it shifts suddenly in an earthquake. Slamming into the tube at 900 miles an hour is not going to be pleasant. Or slamming into the wall because the earthquake made the tube rupture three miles away and the delicate balances of air cushion and near vacuum fail suddenly.

          • Falstaff

            Earthquakes resistance would be a challenge, as it is for any transportation system. That said, consider:
            i) max speed is 760 mph in the proposal, not 900.
            ii) in the event of a severe quake emergency braking would be applied automatically. Full stop at 2g’s from max speed takes 15s, 1.3 mile. Unlike existing HSR, weather conditions would have no impact.
            iii) Existing HSR rail bed and stock at 200 mph in Japan, actually in physical contact with the surface, survived a 9.0 without passenger injury.
            iv) industrial air suspension is not “delicate”. Air cushions have been built for loads of many thousands of tons, indeed for entire buildings.

            v) losing the soft vacuum would cost time and money, but it should not be particularly dangerous. Indeed, part of the safety plan includes “rapid re-pressurization along its entire length” (pg 54) should it be necessary.

          • Adirondacker12800

            They move whole locomotives with air pressure. It’s moving at less than walking pace and if the system fails it settles gently a fraction of an inch to the concrete floor.

          • Joey

            Recall that Musk proposed a distance of ~1mm between the bottom of the vehicle and the bottom of the tube. Even a minor seismic event could cause that gap to go to zero very quickly (again, without active shock absorption on the pylons). And this is between two flat surfaces with relative velocities near 1000 km/h. This would likely lead to massive frictional forces which would cause an immense heat build up, and instability which could cause the pod to crash into the walls of the tube as well.

            Conventional HSR has none of these problems. The train is in physical contact with the track, meaning that if the track shifts, so does the train, but that’s fine because the train will continue rolling.

          • Falstaff

            “And this is between two flat surfaces with relative velocities near 1000 km/h … immense heat build up”

            If it continued, sure. Why would the capsule continue to slide at even half that speed for more than a couple seconds? The air gap in the proposal is under the so called ~30 sq meters of “skis”. If they contacted a surface they’d slide and heat up, as friction brakes do by intention. The proposal also calls for deployable wheels if necessary. Forcing that gap to zero in a small time would require many hundreds of tons. Air drag increases as the gap decreases slowing the capsule. A minor seismic event is not going to yield that kind of load on a two ton capsule.

            The issue, just as with the slower HSV, is with the strain withstand the support structure, of the pipe and pylons. The threat of seismic events on the air carried design aspect of capsule is a red herring. Like an HSR in a tunnel, with respect a seismic even what matters is not the distance to the walls but whether or not the tunnel collapses or the track separates.

          • Adirondacker12800

            two tons capsuiles, like two ton automobiles, don’t decelerate abruptly in a graceful fashion.

          • Falstaff

            In head on impacts, to which this head on wall impact has no relation.

          • Adirondacker12800

            Sideswipe accidents are the most common automobile accident in most states. It doesn’t matter if you decelerate from 760 of 670 or 350 from grazing the wall or at 60 by grazing a telephone pole. Stopping abruptly is unpleasant and it become increasingly unpleasant the faster you are going.

          • Falstaff

            “Sideswipe accidents”, “slamming into the tube”; that’s all nonsense if the tube is intact. To crash or slam into something the object has to have a velocity component in that direction, with out sufficient drag or brake to stop the collision. The capsule skiis have a high pressure air to slow contact even if pressure fails, and then the skiss are essentially a 30 square meter brake pad in the event of contact. Do the physics, not the cartoon.

          • Adirondacker12800

            My car has excellent computer comtrolled ant-lock brakes. That wouldn’t prevent me from stopping abruptly if a tree fell across the road. Or a tree fell by the side of the road and my car grazed it. When the pod hurtling along at speeds that would be supersonic at sea level hits some air that is at sea level pressure because the tube failed it’s going to stop abruptly. If the pod survives the sudden deceleration I suspect they will will arrange with the next of kin to take it out of service permanently and given a respectful disposal. Since they won’t be able to recover all of the remains from all the interior nooks and crannies they managed to get into.

          • Falstaff

            “When the pod hurtling along at speeds that would be supersonic at sea level hits some air that is at sea level pressure because the tube failed it’s going to stop abruptly.”

            The capsule can not suddenly “hit some air” at sea level pressure absent something slicing the tube in half just in front of capsule. Even if it could, the drag force of STP air suddenly in front of the capsule (cd=~0.15, A=7 m^2, v=300m/s) is ~60 kN on the 2 metric ton mass which then decelerates at a = F/m = 1.5g, and just for a moment. You’ve felt worse in a quick stop in your car.

  110. John Kopp

    Falstaff, what is your point? I used a two lane country road bridge built on pylons as a model and came up with $50 million per mile. You suggest the Alaska pipeline which when adjusted for inflation by CPI gives a cost of $50 to $100 million per mile. Costs are much higher through urban areas due to utilities and other existing infrastructure that has to be avoided or moved. Construction costs is also very expensive.

    My cost for the steel was for raw steel, not the fabricated tubes. That would probably be 2 to 3 times that amount. The parameters in the proposal are not sufficient to provide an accurate estimate. I would expect my estimate to be too low if anything.

    • John Kopp

      Last line first paragraph should read: Construction costs are also very expensive in the mountains.

  111. krichards6000

    One of the largely ignored aspects of this blog and associated responses relates to the expansive thinking that occurred to conceive the Hyperloop. The issues of today (not just in transportation) are becoming more complex, coming at a more rapid pace, and are interdependent with many other factors. If we step back and see what just occurred….rather than approach the problem in the “traditional way” of improving upon current modes of transportation, the Musk team challenged whether there might be a ‘5th” mode of transportation that might also address other social concerns such as the environment in a non-traditional way. In the past, most governmental bodies, consultants, and industry professionals orient their solutions from their current existing bodies on knowledge, research, and historically built upon solutions. In other words, from a constrained thinking model which is difficult to change. The Musk team applied expansive thinking that was creative, came from a different perspective, and was divergent from current bodies of knowledge in the transportation field. It may be that the Hyperloop proves to be non-viable based on todays body of knowledge, understanding and political climate. However, the Musk team should be applauded for having the balls to invest time, money and human resources in an unsolicited attempt to solve a transportation problem. It would be interesting to see what might happen if Alon were to take of the the rail and transportation knowledge that he has accumulated over the years, and collaborate or share any relevant knowledge with the Musk team for mutual benefit of all and work with the team as part of a collective as opposed to using his skill and knowledge to pick apart the proposal for…..what benefit? Not really sure of the objective. We all know that if you only have a hammer, everything looks like a nail. For complex problems such as transportation, we need to throw away the hammer and look for new ways to either drive the nail, or find new ways to eliminate the need for the nail altogether. I for one applaud the Musk team for the effort in expansive, forward and future thinking, no matter how the project ends up.

  112. krichards6000

    Was rethinking my post a little and have another thought. If Alon (or whomever are the “experts” in this area) were to team up with the Musk people and share the XX years knowledge spoke about above and in turn perhaps learn from the Musk team, couldn’t there possibly be benefits for all? Let’s say that that the Musk team is onto something when it comes to their costs to build pylons, but for technical reasons the full blown Hyperloop project is not actually feasible. Is it possible that through this process new knowledge such as a new or cheaper way to build pylons (for example), might in turn benefit the rail project? The point being, it is easy to sit on one side or the other of this or any project and be a critic. It is much more difficult to collaborate and share knowledge. Collaborative, expansive, creative and open minded thinking is really what is needed to solve the mission critical issues that are facing our country. This dialogue is a pretty good case study for an MBA program or program in developing expansive problem solving thinking capacity.

    • Alon Levy

      The problem with this is that there already is a lot of expertise on this subject (which I don’t have or claim to have; I simply know a bit more than the average person who the experts are). Actually, if you read a lot of the recent criticism of 538, it’s similar: Nate Silver and his team are getting economic analysis and even climate change wrong because they apply 538’s usual methodology to those issues. When it came to political horserace reporting, the 538 model was good enough, because the established experts were all blowing smoke. When it comes to economic analysis and science, it is not, because there’s such a huge body of solid research that Silver doesn’t know about and doesn’t think he needs to know about.

      The situation with Musk is the same. His real success is in Internet technology: he cofounded PayPal in 1998. At the time, the Internet was almost entirely new, and had no established players, at least not as far as websites were concerned. Google was only founded the same year, and Amazon was only founded in 1994. In such an environment, there isn’t much preexisting knowledge that’s worth much. The problem is that civil infrastructure is nothing like this – there are centuries of cumulative experience with engineering, and preexisting knowledge is everything. That culture that produces both Silver and Musk, and more generally brogrammer culture, doesn’t and can’t value such knowledge, because it grew at a time and in an area when it wouldn’t help but would only slow down innovation. For the same reason it’s better to give up on hoping 538 will be a good source of science reporting and just read science blogs, it’s better to just flush Hyperloop down the drain and concentrate primarily on conventional HSR and secondarily on established avenues of faster transportation, i.e. open air maglev.

      • John Kopp

        Mr. Levy, it appears to me that you proposed the so called hyperloop in your April 1, 2013 post. Mr Musk just took the idea, ran it by his rocket engineers, added some cool graphics and a great sales pitch that he is apparently adept at. I thought you did a better job with your proposal. He used google maps to plan his proposed route, and estimate number and size of pylons required. I checked the route using Geologic Map of California series maps which show central valley route over alluvial deposits. These require extensive foundations for each pylon, and probably individual designs also. So much for krichards6000 assertion of cheap pylons. The route into LA crosses several active thrust faults in addition to the San Andreas and San Gabriel faults. The same is true for SF. I am a retired civic/mining engineer who spent a decade at Vandenberg AFB budgeting for construction projects. I agree the best place for Hyperloop is flushed down the drain. I fear a few million will be spent on feasibility studies then the whole thing dropped.

        • Falstaff

          “I checked the route using Geologic Map of California series maps which show central valley route over alluvial deposits. These require extensive foundations for each pylon, and probably individual designs also. So much for krichards6000 assertion of cheap pylons. “

          There are numerous examples of pylon supported structures running up and down the central valley (and elsewhere that has active geology, ie Alaska): high voltage transmission, pipelines, etc. Why not simply cite the actual design of pylons used in one of those projects, instead of simply asserting on a blog what must or must not have extensive foundations?

          • John Kopp

            Falstaff: The pylons may look like they are sitting on the surface, but they all have to be anchored some way. The material and underlying geology of each site determines the design of this system. As an example, here is a bridge built on pylons over a creek and surrounding wetland. http://straubinc.com/portfolio/missile-transport-bridge/ The pylons are only about 20 feet above the ground, but go as deep as 120 feet to reach a firm footing. Some pylons use piles as footings, and some may only require a spread footing. It all depends on the load and site material. A site survey and core samples of the underlying material is required before a design can be accomplished. For more information, consult Das, “Principles of Geotechnical Engineering”, or a similar text. My experience is that pylons as proposed are not just set on the ground, they require a substantial foundation. The geologic maps tell me that we are not on bedrock, but on unconsolidated material.

          • Falstaff

            JK: Agreed that some structures require deep foundations. See for example the Burj Dubai Tower with 192, 1.5M bored piles all 50M (164ft) deep. The relevant question is for what structures, and where. Clearly projects like the PG&E HV transmission lines that run from SF to Bakersfield right down the Valley, with the largest tower mass up to 640 tons, would not have been economic if the foundation per tower was extraordinarily expensive. For instance, the Path-15 project with 87 miles of transmission line in the Valley at a documented (total) cost of $3.7 million per mile (construction, right of way, financing)

            That cost profile is not possible with the complex, deep foundations you describe.

          • Alon Levy

            The transmission lines don’t need to be built as precisely as infrastructure carrying high-speed transportation.

          • Falstaff

            “As an example, here is a bridge built on pylons over a creek and surrounding wetland.”

            Deep bridge foundations were required in a wetland? What is the relevance to the Hyperloop proposed path?

          • John Kopp

            Adirondacker: Exactly my point. The Central Valley was covered by lakes, marshes, and various wetlands. A simple slab on grade foundation is not adequate. Test drilling and soil analyses is required for proper foundation design.

          • Falstaff

            “The transmission lines don’t need to be built as precisely as infrastructure carrying high-speed transportation.”

            The recent discussion here was on the likely cost of HL pylons. The proposal specifies pylons placed every 30m, nominally 6m tall, with a load of 15 ton capsule+passengers, 30 tons of steel tube, or 60 tons for two tubes per pylon In the HL case, the main requirement of the pylons is to support the load without failure, not precision. This load is not large and thus no particularly sophisticated foundation is required (relative to, say, a transmission tower).

            Alignment (precision) is the job of i) the tube and ii) the “adjustable lateral dampers and one vertical damper” (pg 5), per pylon.

          • Adirondacker12800

            And what do you do when the lightly build cheap pylon shifts enough that the super duper never been used before anywhere precision adjustment doohickeys move outside of their range of adjustment?

          • Falstaff

            “…never been used before”

            Adjustable dampers never been used before? Why would you say that?

            As to structure displacement, yes *every* nominally fixed structure shifts over some time period. There are the long term geologic shifts, the faster weather based shifts of temperature expansion and/or frost heave, the faster yet flex of wind load, and the fastest flex of operational vibration. The HL design must prevent too much movement from reaching the load (in short time periods) using structure stiffness and/or dampers between load and structure.

            Greater displacements which occur over longer time periods (months to years) can be addressed via maintenance. Example: 2 cm frost heave per season, say 10 cm in 5 years. Remedy: detect and adjust tube alignment in maintenance schedule.

            This kind of precision-time requirement is already met, commonly, to the centimeter scale without dampers and without great cost. With dampers or some kind of isolation between support and tube, HL should be able to reach the millimeter scale.

          • Adirondacker12800

            The way to keep the frost heave reasonable is to dig big deep holes and pour lots and lots of concrete in them. How big and how deep does the pylon foundation need to be for the 100-year earthquake? Or do we just let the cars go careening into the tube walls every so often?

          • Falstaff

            “The way to keep the frost heave reasonable is to dig big deep holes and pour lots and lots of concrete in them.”

            As is done now, with HV transmission towers, pipelines, etc. Foundation depth: couple a few meters with cost $1.3 million per mile. To reduce the displacement of load to the smaller lever required here, do things like add adjustable dampers.

            “…how deep does the pylon foundation need to be for the 100-year earthquake? Or do we just let the cars go careening … “

            Concern troll questions detract from the discussion. Anyway, big earthquakes would be handled, per the proposal, the same way they are with surface HSV: detect early and shut down, then go out and repair because things will break. Or do you imagine HSV has cars are careening off the tracks every so often?

          • Adirondacker12800

            If the power pylon sinks a few inches it doesn’t matter. If it sways in the wind a few feet it doesn’t matter. Electrons bounce well. Passengers in pods inside tubes don’t. Pods don’t.

            How is that distracting from the conversation? I’m making the perfectly rational assumption that if this fantasy gadgetbahn was to be built it would be in service for decades and decades. In places like California that means building foundations that don’t move outside of the limits of your yet to be built or tested wundergadgets. In places where it gets cold that means designing for the once a century cold snap that causes especially deep frost heave. Or the once a century ice storm.


          • Arch Stanton

            falstaff has this slackoff attitude that all these matters are just minor details that are one-off nuisances that are minutae that can be papered over with a couple of bolts and nuts. I ASSume that falstaff hasn’t the clue about the hard eye of government concerning matters of safety of human transportation and is so enthralled by the cool thingamajig that falstaff is incapable of being aware that humans go to jail on matters over human transportation when they have the attitude that the potential of humans deaths in the cool thingamajig are the minor detail when it comes to getting the thingamajig built.

          • Falstaff

            “If the power pylon sinks a few inches it doesn’t matter. If it sways in the wind a few feet it doesn’t matter. “

            The issue here is the foundation and its cost, not the above ground tower/building/pylon. If a 50m tower, or 500m building, sways in the wind it is because of deformation of the above ground structure. The foundation can not, and does not move in short time periods (seconds) for these structures without cracking and eventually failing. And above ground here the pylons are 6m (nominal), likely concrete, with a less than 100 ton peak vertical load. That portion of the design is trivial, met with common pile foundations, to keep deformation in the mm range for wind loads against the pylon and a couple meters of pipe cross section.

            Maintaining alignment over slow, long term movement is the challenging problem here, as it is to some varying degrees with every fixed structure ever built. Worse case, that (slow displacement) can be addressed with maintenance.

            “your yet to be built or tested wundergadgets.”


            6 to 550 tons:
            Sliding shoe support on the Trans-Alaska (figure 3) which survived the Denali quake.

            Click to access TAPSearthquakeDenali.pdf

        • Adirondacker12800

          okay when the silt under the cheap pylon shifts three inches and pod goes crashing into the side of the tube the heirs can come and speak to you about how an oil pipeline is pertinent to their lawsuit for wrongful death.

          • Falstaff

            Physics is pertinent, not hyperbole or imaginary shifts or oil or wundergadgets.

          • Adirondacker12800

            yes it is. what happens to delicate human beings when the pod they are traveling in suddenly decelerates because something has gone wrong and their pod crashes into the tube millimeters away ?

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  119. harshsingh08

    Bro. I work in the pipeline industry and we build massive 32″+ Large Diameter pipe through incredibly various terrains, environments of varying degrees of pressure drops, through mountains, rivers, streams, roads and we can build a 400 mile pipeline for $2B Dollars. The proposed BS number for the HSR from SF to LA is LAUGHABLE!

    $52B DOLLARS, are you freakin kidding me???

    I completely agree with this $6B price tag because you are almost 100% excluding yourself on commodity risk by avoiding steel acquisition cost….

    • Eric

      32″ tunnel diameter is nothing. Trains need 7 meter diameter tunnels. That is 8.5 times as wide, which means about 8.5 times the cost in materials and probably more for the tunneling itself. So your $2B rises to $17B for one tunnel and $34B for tunnels in both directions. Add some safety systems (since human beings will use the tunnel), and stations in city centers, and $52B does not sound so unreasonable.

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  133. Simon Fowles

    its terrific that someone can challenge existing thinking in a positive way. Certainly the vacuum tube is a good way of reducing the main energy problem of high-speed transport. I think its also good to conduct experiments. We all move forward that way. Lets hope that a small section of the hyperloop can be built, tested, improved and then we’ll see whether it can compete with high-speed rail.

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