A skeptical response to Musk's hyperloop

http://pedestrianobservations.wordpress.com/2013/08/13/loopy-ideas-are-fine-if-youre-an-entrepreneur/

by anologwintermut • 13 years ago

171 114 13 years ago

pedestrianobservations.wordpress.com

scotty792• 13 years ago

Elon Musk, an entrepreneur who hopes to make a living some day building cars.

Didn't he already make all the living he needs and now just does whatever he likes?

axefrog• 13 years ago

You can almost completely write the article off considering he's characterizing Musk's achievements with such dismissive condescension.

simonh• 13 years ago

No, you really can't. How he characterizes Musk is irrelevant to whether his criticisms of the proposal are valid or not. Just because he deploys dismissive condescension is no excuse for also resorting to it. This is Hacker News, not Slashdot.

scotty792• 13 years ago

What I got from article:

Author is:

- unfriendly towards Elon Musk

- unfriendly towards people who voice ideas of what the author thinks is not their area of expertise in general.

- fond of high speed trains.

- thinking that Elon Musk wants to kill trains to sell more cars.

... oh yeah, and he has some concerns about Hyperloop estimates. Mainly that cost and disadvantages are underestimated.

Also somehow author managed to overlooked the fact that Elon Musk delivered some stuff to International Space Station, most likely at fraction of NASA cost which consist of very experienced people.

If experienced specialist tells that something in his area of expertise can be done. He's most likely right. If he says something can't be done, there's a fair chance he's wrong.

cdash• 13 years ago

Well technically he is worth something like 6-7 billion dollars right now but I believe almost all of that is made up of stock in the companies he owns so if the companies were to end up failing then he would lose most of it and I don't think he plans on selling any of his stock any time soon.

Osmium• 13 years ago

We are no where near the stage where we can judge if Hyperloop is a good or a bad idea yet. At the moment, it is just that: an idea. It needs to be refined, torn apart, put back together, and examined thoroughly and I look forward to that happening. I'm glad this article exists and is asking tough and valid questions, but I feel like the article is wrong in trying to persuade people that the Hyperloop is intrinsically a bad idea when a much better response (at this stage) is to try and improve the design.

In particular, some parts of this article are just way way off base, e.g.:

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

and

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.

The article would have been much stronger if it'd left ego and silly ad hominem out of it and reported on facts alone.

I also have concerns about the costings: the Hyperloop report didn't give sufficient justifications for any of them. Yet I assume they didn't just pluck them out of thin air either. We really need to know how they were calculated before we can do a more critical analysis of them or someone should try and come up with their own rigorous cost projections. We can go back and forth all day saying it seems too low until someone actually definitely proves it.

In particular, comparing Musk's projected costs for, e.g., viaducts to how much the government says they cost is almost definitely a poor metric since, after all, exactly the same could have been said for Musk's cost projections for rocket-powered spaceflight.

rkangel• 13 years ago

Exactly. I enjoyed the fairly well supported counter-arguments to the ideas. Inevitably it isn't going to be quite as good as it appears initially, and open debate is how consensus is reached, but he devalues the whole argument by laying into the person who brought it all up.

Whether or not the idea is valid is irrelevant - the fact that Elon Musk is proposing it does lend it some additional weight - with Space X and to a lesser extent Tesla, he has gone into an existing market, taken a step back, rethought things from the ground up, and re-written the book on how much it costs to do things.

I don't know if Hyperloop is as technically feasible and cost effective as it looks, I don't know if any government would have the courage to go in that direction, but I do know that it isn't going to get anywhere with good balanced debate on the technical merits of the proposed solution and ad hominem rubbish just gets in the way of that.

makomk2• 13 years ago

What's wrong with this part?

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

If the blog post's claims are correct - and the numbers in it seem to have a much more solid basis in fact than anything Elon Musk's come up with - then even a simple back-of-the-envelope calculation should've been enough to show his power consumption figures for high-speed rail are impossibly high. The trains are simply incapable of using that much power.

pmarca• 13 years ago

It's almost like it's easier to criticize new ideas than come up with them or implement them. Oh, wait...

mjn4• 13 years ago

It's not hard at all to come up with speculative transit ideas with some high-level engineering guesstimates. It's sort of a hobby of a lot of people. People have even sketched out plans for this particular idea (partially evacuated tube transport).

Implementing them: yes, that's harder, and most transit ideas fall down at that stage. Implementing them in a way that comes anywhere near the original optimistic projections is even harder (see: maglev).

madaxe• 13 years ago

'What is love? What is creation? What is longing? What is a star?' thus asks the last man, and blinks.

The earth has become small, and on it hops the last man, who makes everything small. His race is as ineradicable as the flea; the last man lives longest.

'We have invented happiness,'say the last men, and they blink. They have left the regions where it was hard to live, for one needs warmth. One still loves one's neighbor and rubs against him, for one needs warmth...

I see Musk as something akin to Nietzsche's superman - and this chap, the detractor, the denigrator, the naysayer, is his last man.

philwelch5• 13 years ago

I can't believe you got downvoted. You've made explicit the sycophantic, uncritical Elon Musk worship that permeates this thread.

INTPenis• 13 years ago

I for one can't get the mono rail song from the Simpsons out of my head.

But people have already pointed out that this is merely an idea and should be treated as such. Though a town with money is sort of like a mule with a spinning wheel...

tinco4• 13 years ago

Geez the author of this article is a dick. It makes it very hard to read, it looks as though he makes some valid points, but it's interspersed with so much personal pettyness that it's hard to take him seriously.

Why does this guy hate Elon so much?

sz4kerto• 13 years ago

Whether or not he's a dick does not matter. Personal antipathy or sympathy should not matter that much. That's exactly what he says btw: most people haven't even read the Hyperloop PDF but they're already fans - just because it's Musk, and he seems to be a nice guy.

Jobs-effect again and again.

tinco4• 13 years ago

I just explained why it does matter. His dickishness made his otherwise interesting article agonizing to read. I did not think the author was a dick _before_ I read the article.

Anyway, I have read the Hyperloop pdf end to end and I think it's great. I don't agree with this author at all that Elon Musk's endeavours distract from improving existing technology. Nor do I think that improving existing technology is as important as inventing new potentially disruptive technology in general.

People are fans of Musk because he succeeds and delivers in the face of spineless critics like this one. Just as people were fans of Jobs as he reintroduced quality into consumer electronics succesfully.

andor• 13 years ago

From the article:

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.

jasonwatkinspdx• 13 years ago

Which is an entirely unsupported claim that sheds no light on whether what's in that pdf is accurate or not.

The problem is the article's criticisms aren't categorical. He doesn't apply the same standards he demands of Elon et all to his own claims.

It's sad, because clearly the guy is well informed on public transit projects, but there's no reason for him to descend into ad homs and his own pet psychoanalysis of Elon Musk.

alan_cx• 13 years ago

He doesn't. He "hates" sycophancy. The fact that you think its Musk he hates sort of proves his point.

jcox922• 13 years ago

He mentions Musk by name.

crusso2• 13 years ago

There are many ways to gain celebrity. Some people like Musk actually do things, create things, say clever things... others like this Levy are parasites who lack the ability to do and create but can harness enough wit and attention to criticize and attempt to destroy.

Critics will always have an audience in the envious and the shadenfreudencia.

jacquesm3• 13 years ago

Alon Levy thinks that anybody that is not a 'transportation engineer' should stick to minding their own business. His agenda is shining through pretty strong here and his dislike for Elon Musk (who apparently succeeds in areas where he's not qualified to succeed in the first place) is as strong as it ever was. The more successful Elon Musk is in his endeavors the more vehement this kind of attack seems to become.

It's quite possible that there are valid criticisms embedded in between the vitriol but I wished he'd stick to the factual stuff and leave his bias out of it. Calling Elon Musk a crank is an insult given what the man has already achieved and reflects poorly on the writer.

I personally think that the best way forward with the hyperloop is to create a scale model, the tube and carriage could be (virtually?) wind tunnel tested and valuable information would be gathered that way offering a path to verify the design one step at the time starting with the hardest part, the aerodynamics.

crusso2• 13 years ago

Vitriol is right. Starting your piece with:

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.

... was just an immature and catty way to begin a (what he hoped would be) substantive attack on the Hyperloop.

The article finds some questionable issues in the initial proposal, but its unfortunate that Levy writes as though Musk is a jackass for even putting the idea out there.

lmg643• 13 years ago

catty is a big understatement for this article - there is some pretty radical thinking in there, particularly the part about entrepreneurs not deserving the spoils of their companies, because someone else would have done it if they hadn't. (key quote: "People get extremely rich for doing something first, even if in their absence their competitors would’ve done the same six months later.")

not sure what that has to do with elon musk, other than to try and put together a "nuclear" attack on his character, going after the moral foundation of his wealth in addition to the hyperloop idea. it's like the article is a communist critique wrapped in a technical evaluation.

away from the radical and bitter aspects of this critique, i appreciate the technical comments in here. i think it is vital to have a proper, public technical evaluation of the hyperloop, and he undermines his argument with the personal and philosophical. i would love to see a response to this critique from the hyperloop side.

i would agree that musk, having lobbed this hand grenade into public discourse, should follow-through on his idea to some extent - build a test bed and prove it can be done on a small scale. in my limited experience, if something is a really good idea, you try and pursue it for yourself, rather than hoping someone else will steal it from you.

mjn4• 13 years ago

No, Levy just thinks that anyone who wants to make a detailed proposal for a specific line should do enough research to justify their claims, and show their evidence. He isn't a transportation engineer himself (he's a mathematician), so it's not some kind of turf defending. The fact that he as an interested amateur has this information available makes it absurd that Musk wouldn't have done at least as much research as Levy has, to back up his numbers with data.

Alternately, the proposal could have avoided making detailed claims on cost and routing, and instead focused on the high-level technology, more in the direction of validating the basic idea, and leading up to a test track. There's nothing wrong with that. But if you're going to claim you can build a line on a specific route for a specific cost, you need to do the work to justify those numbers credibly. Musk's existing document, at least, comes off as very hand-wavy and lacking in empirical grounding for any of its detailed engineering and cost estimates (that grounding could be rooted in his own data, or in existing data, but there has to be data somewhere).

jacquesm3• 13 years ago

1) Musk states specifically it is an alpha issue and welcomes constructive criticism

2) I did not claim Levy is a transportation engineer

3) Musk did this quite handy, he did not propose the hyperloop in a vacuum (pun intended) but for a specific application, this increases the chances of something being done with it

You have to start somewhere, think of this as a first proposal that can be suitably amended or scrapped in its entirety as more insight is gained.

I'm pretty skeptical about the whole thing but Musk has a history of pulling off impressive feats and I would not put it past him to come up with something that might work when tweaked. So let's hear it for constructive criticism (fix what is broken or provide actual proof why it can not work) rather than outright dismissal.

bowlofpetunias• 13 years ago

Okay, so this is over the top and not very constructive.

However, there is an underlying pattern that annoys me too. There are literally thousands of people working in innovative transportation ideas, why is the barely researched idea of a relative amateur like Musk receiving so much attention?

The same applies to the Soylent story: people who have been working on the problem for decades are being ignored in favor of self-promoting entrepreneurs who's ideas lack depth.

The great irony is that the cheerleaders for these entrepreneurs are the same people that bitch about the lack of scientific knowledge in politicians and the lack of attention for science in general.

I can perfectly understand that this pisses people of who have been diligently working on these problems for decades.

jamesdelaneyie• 13 years ago

Sounds like a marketing problem for these diligent hard workers? But would more attention aid them in their decade long hikes or hinder them by opening them up to more public scrutiny and the possible need to appease that can follow? Certainly don't know myself.

batemanesque2• 13 years ago

it's not a marketing problem. people outside a given field will, by virtue of their inexperience, be prone to more hubristic ideas they don't understand the impossibility of. combined w/ the tech scene's natural credulity - as demonstrated by the Soylent debacle - & there you go.

the problem w/ casually describing it as a "marketing problem" is it completely excuses both entrepreneurial excess & the whole Valley hype thing. sure, there should be an onus on people to present/market their ideas well, but also on the public to be a little more skeptical of wild & unfounded claims.

ThomPete• 13 years ago

Well, think about how little spotlight Thorium have when it comes down to it. Only recently have there started to be momentum to get this field to a point where we can say whether it possible or not.

I would assume there are thousands of other areas like this where some "better" version never sees the light of day.

jhuckestein• 13 years ago

It sounds to me that you have discovered an important and often underestimated property of disruptive ideas. How did an 18 year old change the way we communicate online forever? How could a clerk at the patent office usher in the era of 20th century physics?

It's possible and maybe even easier to have truly breakthrough ideas if you're coming from a different field. You can always catch up on all the knowledge required to execute your idea later.

And yes, often you'll find out that your idea wasn't so great. But at least you didn't dismiss it as out of hand because you didn't come across it in your years of experience in the field.

hollerith• 13 years ago

It's wrong to think that Einstein was "coming from a different field". He had a PhD in physics from a good school. In his day, physics jobs were much scarcer, so perfectly ordinary physicists tended to need to get non-physics jobs for parts of their careers.

driverdan• 13 years ago

It is extremely rare for someone with little to no knowledge or training in a field to step in and change everything. Anyone claiming to do so should is making extraordinary claims and needs to provide extraordinary evidence.

zwieback• 13 years ago

True, but disruption is extremely rare in mechanical and civil engineering. It's more common in SW and theoretical fields.

zeteo4• 13 years ago

The article is full of cant in more ways than one, and more about social norms when entering a new field than the proposal itself. This is obvious from the kind of nitpicking that goes on (no references! 4.37 m/s^2 is the maximum motion sickness possible because an accredited expert proposed it; I've never seen 4.9 m/s^2, but it's surely a barf comet!). Despite the author's high opinion of his own knowledge, the criticism amounts almost entirely to basic arithmetic and comparisons to existing systems that are built on rather different principles. The really interesting, constructive questions: does this low-pressure air cushion thing really work? what are some factors that we need to explore to determine its true efficiency? etc. are of no interest to this kind of expert, who is more interested in tribally defending his own turf (see the unnecessary name calling) than in figuring out new ground.

In all fairness, I would give much more slack to an engineer talking about his field. But, as the author himself points out, almost all civil engineering technology is from the 19th and early 20th century. He seems to think that, in between, his colleagues have been perfecting the fine forms of the art and polishing its many facets. Except feats that were once fairly common, such as building the Hoover Dam under budget and two years ahead of schedule [1], are in the realm of the mythical these days.

[1] http://en.wikipedia.org/wiki/Hoover_dam

Retric4• 13 years ago

I would add he completely ignores the fact he runs a SpaceX which has significantly under cut a long established industry. If you look at his numbers there Basicly estimates for actual costs before padding where large contractors pad construction costs as much as possible because that's how they maximize proffits.

mjn4• 13 years ago

SpaceX is based on a fairly different principle, of taking proven designs from the past, updating them, and building them for less. For example SpaceX's Grasshopper VTVL is following in the footsteps of the 1990s McDonnell Douglas DC-X, not some kind of completely untested idea. He isn't taking a previously speculative technology idea, like a space elevator or something, and trying to build it.

An analog here would be if Musk had a proposal to take an existing, working mode of transit (at least working in prototype) and build it for less. But the current proposal is more like hard sci-fi: goes into enough depth to be back-of-the-envelope plausible, but no detailed engineering or working demonstration, and very hand-wavy cost estimates.

dgudkov• 13 years ago

Currently SpaceX doesn't offer significantly lower LEO delivery costs -- they are on par with Ukrainian/Russian space programs [1].

[1] http://en.wikipedia.org/wiki/Comparison_of_orbital_launch_sy...

akjj3• 13 years ago

This is obvious from the kind of nitpicking that goes on (no references! 4.37 m/s^2 is the maximum motion sickness possible because an accredited expert proposed it; I've never seen 4.9 m/s^2, but it's surely a barf comet!)

This isn't nitpicking. Dealing with the acceleration around curves is going to be a problem for any transit system and at higher speeds it becomes a bigger problem. Unlike bathrooms, this is going to be intrinsic to any system that carries human beings. As the author points out that the hyperloop proposal has significantly higher acceleration than any other high-speed system that he knows about.

So, how did the hyperloop designers decide that 4.9 m/s^2 would be safe? Did they find some study which tested this level of acceleration on average people? Did they conduct their own study which overturned conventional wisdom? Did they look at the research which led to the 4.37 m/s^2 figure and determine that it was fatally flawed? This is a critical issue and if the designers don't explain themselves, then it's fair to assume they made it up.

The hyperloop proposal contains innovative elements (air suspension in evacuated tubes) and elements which are essentially common with many other transit systems (viaducts, human passengers). The designers deserve credit for the former, but they can't sweep the details of the latter under the rug. The point of references is not stylistic and not to name-check previous work. The point is that when you're doing something, which has had lots of previous research, you either use that research to justify your claims or you explain why yours will be different.

The really interesting, constructive questions: does this low-pressure air cushion thing really work? what are some factors that we need to explore to determine its true efficiency?

Those are interesting questions and if Musk had proposed just the air cushion technology, then that's all we would be talking about. People would build test pieces to validate the technology and then go looking for applications. Instead, Musk choose to also include a specific proposal for a replacement for the LA-SF high-speed rail line and to estimate the costs at a tenth as much. That's what got the most media attention and so that's the aspect the OP chose to criticize.

BTW, you seem to be implying that the OP is a civil engineer or a transportation engineer with an axe to grind, but he's just an amateur and if you look at his other posts you'll see that he has a lot of concerns for reducing the costs of infrastructure projects.

zeteo4• 13 years ago

I agree that it's important to talk about motion sickness. I was pointing out that the way the article deals with it (remarking that the proposed system may involve 12% higher lateral accelerations than HSR, and instantly dismissing it as a "barf ride") is inadequate. Here are a few questions that I don't know the answer to, but seem a lot more interesting:

- Do we have studies that estimate the effect of lateral acceleration on motion sickness? What do they indicate (e.g. 0.1% of passengers get it at 4 m/s^2, 2% at 5 m/s^2 etc.)?

- To what extent is motion sickness in HSR comparable to the proposed system? Are the differences (no outside visibility, different vibrations model, possibly different seating) significant and if so how?

- To what extent do potential passengers care about motion sickness? Has anyone compared cost and convenience trade-offs for systems with different expectations of motion sickness e.g. ferry vs. train? How comfortable are passengers with self-medication in such contingencies?

Etc. And motion sickness is only one of hundreds of possible serious weaknesses in this project. But this is inherent in anything that hasn't been tried before; anyone can think of hundreds of ways in which it can go wrong. Does this mean we should never work on anything that isn't fully proven?

lifeisstillgood• 13 years ago

My maths may be letting me down but 4m/s is a mere 14km/h, and many production cars will get you from 0 to 115km/h in less than 8 seconds, so the acceleration of 4m/s^2 is fairly common in consumer world, so unlikely to crush windpipes.

JoeAltmaier• 13 years ago

The article was a fairly even mix of real issues and more hand-waving. Its going to take 2 hours to traverse the hyperloop terminals? Where did that come from?

The Hyperloop document was obviously putting a flag up a flagpole to see who salutes. It had a few man-hours of estimations put into it. It looks like that, obviously.

So the numbers need improvement, sure. Its nit-picking when you get all emotional about it and trash the author.

Anechoic10• 13 years ago

the criticism amounts almost entirely to basic arithmetic and comparisons to existing systems that are built on rather different principles.

But many of most important (and show-stopping) principles involved are the same, and those are what tend to cause delays and increase costs - things like running into unexpected geology, dealing with NIMBY's, the eminent domain process and so on.

He seems to think that, in between, his colleagues have been perfecting the fine forms of the art and polishing its many facets.

They (we) are. Want to see for yourself? Go to the Transportation Research Board annual meeting in Washington D.C.: http://www.trb.org/AnnualMeeting2014/AnnualMeeting2014.aspx

Except feats that were once fairly common, such as building the Hoover Dam under budget and two years ahead of schedule [1], are in the realm of the mythical these days.

You can say the same about the original elevated Boston Artery, the 19th century railroads, etc. The biggest difference between the mega-projects of old and today involve 1) the environmental process and 2) commitments to worker safety. It's fairly easy to build a project quickly when you don't care about splitting neighborhoods, killing/maiming workers and contaminating soil. The environmental process in particular has been a double-edged sword - it's done well in protecting the environment and communities, but it also provides means for anyone who doesn't like any facet of a project to significanty delay (or kill) it.

zeteo4• 13 years ago

The biggest difference between the mega-projects of old and today involve 1) the environmental process and 2) commitments to worker safety.

I don't see why environmental and safety considerations are such big unknowns, I think we have a pretty good handle on both by now. Are they factoring to build it with pollution and no safety when they estimate the cost and schedule these days?

In fact, if you read about the history of Hoover Dam there were a number of these things that they weren't legally mandated to do back then, but did them anyway. For instance, workers were offered employer-based health insurance (an arrangement that later evolved into what we know today as Kaiser Permanente).

moogleii• 13 years ago

He definitely seemed to have a chip on his shoulder with a lot of unnecessary backhanded comments, and many engineers do suffer from saying "no" too often, but I do think he raised several points that are applicable to the Hyperloop. Until someone invents anti-gravity, g-forces and other traditional physics problems are going to be a factor. I've been in a sustained half g turn. It's not uncomfortable, but it's not exactly old person friendly, either (in simplistic terms, take half your body weight and imagine that much force pushing you laterally). You'll want bucket seats.

And I did not know the Hyperloop would not actually go into LA proper. That's a significant difference to me. That last leg into LA is where a lot of the traffic trauma happens, the part I would most want to avoid.

Ultimately both "sides" need to work with each other. The entrepreneur pushing the envelope, and the engineer making sure things are feasible.

dragonwriter• 13 years ago

Except feats that were once fairly common, such as building the Hoover Dam under budget and two years ahead of schedule

Buildng projects on the scale of the Hoover Dam (whether under budget and ahead of schedule or not) were never "fairly common".

misnome• 13 years ago

An interesting article, and seems to be nicely referenced. Most of the detraction of the article seems to be attacking his dismissal of Musk; that shouldn't matter, given it seems to actually quote sources for details. I found especially interesting this quote:

If a famous question could be solved in ten pages, it probably wouldn’t still be open.

Which of course isn't saying that it's impossible, but that claiming it to be so requires overwhelming proof.

Hyperloop seems like an interesting idea, and certainly worth some investigation and research (as is, any proposal and idea). But large scale hand waving and dismissals of the problems as ad hominem attacks don't help lend an air of legitimacy.

My personal view? I find it interesting that he proposed this, but initially didn't want to do any of the development or payment himself. That doesn't sound like someone who truly believes in their "vision".

Symmetry• 13 years ago

I'm really unsure about the author's assertions regarding the maximum accelerations that people can take. Those might be the normal regulatory limits for passenger rail, but I'm pretty sure that the accelerations I've experienced on planes have also gone up into territories the author would consider utterly unacceptable.

On the other hand, I think he has some good points regarding the cost numbers. If pylons have all the advantages that Musk claims then why aren't we all getting around city on monorails?

cousin_it2• 13 years ago

Is it possible to build viaducts for $5mil/km?

Retric4• 13 years ago

Yes, however the cost of a viaduct is largely dependent on the height required. The Alasca pipeline came in around 1.2 million per mile dispite vary harsh conditions but it was also rather low to the ground.

cousin_it2• 13 years ago

Maybe I'm confused about the meaning of the word "viaduct", does a pipeline count as one?

msandford7• 13 years ago

This guy's main real criticism is "train viaducts cost X and Musk's proposal is 0.1X therefore it must be wrong" is total bullshit. It MIGHT be valid under the following assumptions:

1. The weight of the train and the hyperloop capsules are the same

2. The construction methods employed are identical.

But they're not! Average train car weight (if they have to comply with FRA regulations) should be in the 60 ton range. https://www.ebbc.org/rail/fra.html and http://uk.answers.yahoo.com/question/index?qid=2006082807531... Average train car length is betwen 60 and 80 feet so we'll go with 80.

60 tons / 80 feet = 1500lbs/foot. In the case that a non-FRA compliant car can be used, that number SHOULD drop to about 750lbs/foot.

The hyperloop cars are speculated to be 16.5 tons and 28.5 tons each. No hard numbers on length but if you assume 3ft per passenger and 28 total (14 per side) and add a bit of room for the other stuff, you can come up with 14 * 3+15=57 feet or for three cars, 3 * 20+15=75 feet.

33,000lbs / 57 feet = 578lbs/ft. 57,000lbs / 75 feet = 760lbs/ft

So it looks like the big-case hyperloop will weigh about the same as the best-case high speed rail.

Now let's analyze the support mechanism. Trains run on rails (two of them) and they weigh ~100 lbs per foot and are around 3" wide and 6" tall. These rails need to be very precisely supported both side-to-side and up-and-down especially if the trains are going to run at 200+ MPH. For viaduct you've got to build the bridge, then put down the ties, then put rail on top of those, fasten it down, etc. Ties are in the range of 6-8" thick and then there's the ballast (rocks) which aren't light either and which are generally required to keep the ties from moving. On bridges (viaduct) you might do something newer and fancier but I wouldn't count on it here in the US. Overall you've got at least 200lbs/foot for the rails and I might guess another 500-1500lbs/foot for the ties and ballast and such. Rock weighs ~150lbs/cuft and so does concrete so if your ties + ballast are a foot thick and 8 feet wide (rails are 4'8" plus 20" extra on the sides) that's 1200lbs/foot.

Hyperloop runs in a 7.5 foot diameter tube with a 0.8in thick wall. 7.5 * 12 * pi * 0.8=226 square inches cross section. Or a foot of it has 2712 cubic inches of steel. At 0.283lbs/cu-in that comes out to be 767lbs/foot. Because it's pipe (which has excellent structural geometry) it is self-supporting and thus all you really have to do is get the pipe properly supported on top of the pylons, weld two sections together and you're done.

Here's the last part. Hyperloop cars will be at least a mile apart. That means the system can be designed to support just one of them per pylon. Train cars will be 3 feet apart, and thus the viaducts have to support 1500lbs/foot * 80 feet per car * 10 cars = 600 tons. Versus the hyperloop car weights of 16.5 tons or 28.5 tons.

So these two systems are mildly different in terms of their car weights but dramatically different in terms of the overall structural requirements and design to meet those structural requirements. Train track is heavy and train cars are heavy and trains are fairly dense (due to their length). Hyperloop cars are about half as heavy and hyperloop track is half as heavy and hyperloop support densities are only about half versus rail. 0.5 * 0.5 * 0.5 = 0.125 or 12.5% which isn't terribly far off from the 10% number that the Hyperloop is quoted to cost versus the high speed rail system.

TL;DR: Cut track weight by half, car weight by half, and total support weight by half and you get 0.125 which is suspiciously close to 0.10, the number that the article author had such a problem with.

EDIT1: formatting

EDIT2: tl;dr

Anechoic10• 13 years ago

That means the system can be designed to support just one of them per pylon.

The capacity of the structure is not just limited to the weight of the revenue vehicles, the structure needs to handle other loads it may encounter over the its useful life, such as snow (probably not much of an issue in central/southern CA), water (if the tunnel leaks) and maintenance vehicles (which will likely be significantly heavier than the passenger cars since they will have to be self-propelled).

then put down the ties, then put rail on top of those, fasten it down, etc. Ties are in the range of 6-8" thick and then there's the ballast (rocks) which aren't light either and which are generally required to keep the ties from moving.

You don't need ballast & tie track on structures.

In any event, cutting the material weights in half (even if you can, which is doubtful) does not automatically cut your costs by 90 percent. You still have the environmental process, you still have NIMBYs, you still have construction mobilization costs, etc.

msandford7• 13 years ago

That's a good point; something I neglected in my analysis.

I would argue that since the tube sections would all be pre-fab that means that the installation cost of the tube would be really small. Rail installation costs are no joke due to the need to precisely align horizontally and vertically the two rails.

You can make tube in 50ft sections and ship them via truck without needing any special permitting and given that the highway runs right next to the planned route, the pre-fab notion is quite a good one.

akjj3• 13 years ago

TL;DR: Cut track weight by half, car weight by half, and total support weight by half and you get 0.125 which is suspiciously close to 0.10, the number that the article author had such a problem with.

In the comments to his blog post, the OP disputes that lighter weight is going to lead to significantly lower pylon cost. I didn't look through his references, but he also has an update showing how assuming that pylon costs are going to be linear in the weight is not consistent with the hyperloop document itself.

I had to reread the update a few times, but the argument is: the proposal contains two versions, for passengers and for cars. The car version will weigh more and cost more, but the cost increase is much less percentage-wise than the weight increase, so the hyperloop designers themselves don't believe that pylon will be linear in the weight.

As I said elsewhere, this is why references are not just a formality. If the designers had explained where they got their cost estimates from, we could still argue about their accuracy, but we wouldn't have to speculate where they came from.

msandford7• 13 years ago

There's a table in the PDF on pages 55-56 that shows the tube & pylon cost breakdown. In the small version the tube costs $650mm to make. In the large version, which has 60% more material, it's quoted to cost $1200mm to make. That's an 84% increase in cost for a 60% increase in materials. The other costs in the system such as the cost of pylons, installation, etc are individual line items on the overall budget of $5bn or $7.5bn

dnautics2• 13 years ago

I'll just add one thing. It's reasonable to criticize musk for 'not knowing things outside of his domain'. But claiming that musk knows nothing about the cost of building metal tubes, is really stupid. It's certainly possible musk is fudging the numerical values.

Anechoic10• 13 years ago

Building metal tubes is one thing. Actually getting permission from abutters to install those metal tubes on/near their property and then dealing with the varying field conditions is a whole 'nother problem.

anologwintermut• 13 years ago

The problem seems to be: if you could build a partially evacuated tunnel on top of pylons, you could build a light rail system on top of the same pylons with the same sized cars and it would weight less since the track weighs less than the tube and you could replace the car's 1500kg batters with drive motors and power them off a third rail/over head wire.

Of course, this would have rather poor capacity, but that's a problem with the hyperloop as well. It would also be slower at maybe 200 - 250 MPH, lowering capacity further.

But if someone claimed they could simply do a 250mph light rail at drastically lower cost, people would necessarily be skeptical. Adding a bunch of really interesting high speed tech on top, shouldn't change that claim much. About the one way I can see it should change the skepticism is if the increased speed increases capacity sufficiently. Which seems not to be the case.

Someone2• 13 years ago

1) I doubt construction cost is a linear function of weight, as costs of material often are only a fraction of them. For example, one will need access ways for repairs, regardless of the weight of the structure.

2) I would expect that wind pressure on a tube is higher than on a rail with an occasional train on it. If so, the supports need to be designed to handle that higher load.

3) I think higher speed trains going through a bend in the track exert higher forces per kg of train than slower speed trains. Again, if so, the design will have to accommodate for that.

4) I don't see how that 0.5^3 makes sense. If both track and train are half the weight, my conclusion would be "total structure to lift is half the weight", not "total structure to lift is a quarter the weight".

I am not an engineer, so corrections welcome.

enoch_r• 13 years ago

While the author is annoyingly dismissive of Musk, the tribal responses here are unusually defensive and uninformative. It seems like our identities have expanded to encompass Elon Musk as well as Bitcoin (pro and con) and the NSA.

http://www.paulgraham.com/identity.html

the_watcher• 13 years ago

Musk has pretty regularly stressed that this is an alpha design, and that he welcomes feedback and improvements. It may be true that he trashes HSR and that it competes with Tesla. HSR is also stupidly expensive and arguably too slow. Regardless of your feelings on HSR, it's also impossible to argue that the CA government is likely not to screw it up somehow. It's possible that he could both benefit from HSR failing and also be benevolently proposing that we actually try something new. Don't forget, he's pledged his own money to this, and now seems to be leaning towards developing a prototype. I wonder if putting up the cash for a prototype will quiet the critics down. I, for one, am a big fan of rich people spending their money on cool things that they like, from Mark Cuban pushing the limits of analytics in basketball to Musk with Tesla/SpaceX/Hyperloop to Bill Gates' humanitarian efforts.

jcox922• 13 years ago

'skeptical' doesn't seem like the right word. I think 'loathsome' would be more fitting. While the author makes some good points, it was hard to consider them legitimate given that he sandwiched the article with opinionated rants that seemed to abhor the idea of successful people having good ideas.

leot• 13 years ago

If there's enough public will to make something great happen, and that something-great is within the realm of engineering feasibility, then it will happen.

I love HSR. But I also think we as a species are capable of much, much, much more than we're currently accomplishing. And much of the reason we're stuck using slow, uninspiring, and polluting technology from yester-year is a lack of public will.

So to the naysayers: if you want to harp on some bold proposal to do something great, pretend it's 1961 and someone told you about sending men to the moon and back. Pretend it was 1948 and someone proposed making trains that went 90 mph. Pretend it was 1850 and someone proposed linking Paddington and Farringdon using a massive tunnel buried deep underground. Real things change all the time. Technology can make problems go away. Bold proposals such as Musk's -- proposals that are the good-faith effort of someone who is ultra-competent and with a lot of social and financial capital -- are proposals that need to be celebrated and encouraged.

Doing new things well is orders of magnitude more difficult than doing that which has been done before. If you've never followed-through on a crazy and bold idea, please temper your critique of those who have.

jdietrich• 13 years ago

Frankly, I'm sickened at the hubris involved in this kind of analysis.

Musk owns a space exploration company that is flying regular commercial missions, yet OP thinks that Musk has made elementary mistakes in his physics calculations. SpaceX are currently building a passenger spacecraft, but OP thinks that nobody has factored the effect of G forces on passengers into the design. They have reduced the cost of putting mass into orbit by an order of magnitude, but OP deigns to assess the validity of Musk's cost estimates.

Frankly, who the fuck is he to tell Elon Musk what is possible? Musk has degrees in both economics and applied physics. He has done the "impossible" in three industries and is an epoch-defining figure in electronic payments, space exploration and the motor industry. Musk isn't some crackpot with a big bank balance, he's a genius with an astonishing track record of revolutionising established industries from the outside, by ignoring old assumptions about what is possible.

Hyperloop might succeed or fail, but I genuinely can't think of a single person who has ever lived who might be better qualified to make that judgement than Elon Musk.

jpatokal• 13 years ago

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.

"Security checks"? Why would Hyperloop require any more security checks than the HSR? If anything, you'd expect security to be faster for a constant stream of departures, vs 1000+ passengers bunched together for a train.

(Or you could be sensible like the French, Japanese, Germans and Chinese and dispense with any train-related security theatre entirely, but that would probably be too much to ask in the land of the free and the home of the scared.)

mehwoot2• 13 years ago

Security checks is not the main cost of time there. The hyperloop is suggested to end up in Sylmar, which according to google, is about a 30 minute drive from Union Station in the center of Los Angeles, where the HSR will stop at. I don't live in LA so I'm not sure whether that 30 minutes is optimistic or pessimistic.

A skeptical response to Musk's hyperloop

Related Stories