Musk's Hyperloop math doesn't add up

http://greatergreaterwashington.org/post/19848/musks-hyperloop-math-doesnt-add-up/

by subsystem • 13 years ago

34 76 13 years ago

Denzel2• 13 years ago

Isn't it incorrect to simply compare the capacity of the Hyperloop vs. the High Speed Rail. Shouldn't the transport time also be taken into account?

I mean, simplifying of course, if the Hyperloop can carry ~3,000 from A to B in 30 minutes, and the High Speed Rail can carry ~12,000 from A to B in 2 hours, which is better? In this scenario wouldn't they be equal?

anologwintermut4• 13 years ago

The measure is capacity per unit time. The hyperloop's capacity is much smaller.

craftkiller• 13 years ago

Well I'm from the east coast so I'm not the most familiar with SF/LA but how many people per hour actually travel between those two cities? Would it really exceed the 1,260? If not then the reduced travel time would certainly be a huge benefit.

Denzel2• 13 years ago

Ah, you are correct. I figured I was missing something. Thanks!

yk• 13 years ago

See anologwintermut's comment. But if anything, the faster Hyperloop needs a larger capacity, since there would be more demand.

6d0debc071• 13 years ago

In addition to those mentioned in other forks on this thread - There are also scheduling trade offs. One of the arguments against high speed rail is that it places a great degree of emphasis on end to end times, whereas on many routes there are a lot of intervening stops that will render greater capacity per train vastly more useful than higher speeds.

Probably not a concern for the given case - but if you're comparing transport options in an abstract sense it's something to be aware of.

anologwintermut4• 13 years ago

So his point about spacing may be true for loading and unloading, but it is not for emergency stops. You can exceed .5g's in am emergency. With appropriate restraints, 4 or 5g's would be possible.

The larger problem is: if you can build a hyper loop track at 10% of the cost, you can build an ultra light conventional "train" on the same pylons and with lighter weight,cheaper, track. It would run at maybe 200 or 250pm and hence with reduced capacity. At best Musk's cost claims are a capacity/cost trade off. At worst, they are suspect. I think they are suspect, especially given the extreme tolerances of the tube

johntb862• 13 years ago

I think one advantage of the hyperloop is that it would probably be quieter (they claim the compressor uses <150 HP) so that would make putting it on a pylon simpler and would reduce the need for noise barriers. Also the separation between tubes could be much lower than the separation between tracks. I'm not sure how much this would affect the feasibility of putting a more normal HSR train on small, lightweight pylons, but it wouldn't help.

anologwintermut4• 13 years ago

I mean his tunnel/tube is more expensive than a noise barrier. It has all the same properties but has to withstand far higher pressure differences and be built to insane tolerances.

johntb862• 13 years ago

Also, it has a large enough speed advantage that it doesn't have to go straight to the city center to have a time advantage over air travel, and that would be a big part of reducing the cost while keeping it viable.

jackfoxy• 13 years ago

Comparing the theoretical capacity of the Hyperloop vs the High Speed Rail is only one fact to consider. Musk correctly points out the High Speed Rail is in theory way more dangerous. And, possibly more significantly, it is just too slow. To expect travel consumers to opt to max-out the so-called High Speed Rail capacity is wishful thinking. The real "high speed" capability of the Hyperloop make it more likely consumers would opt to max out its capacity, at which point more capacity can be added (by adding a parallel loop), and it is still cheaper than the High Speed Rail.

jdmitch• 13 years ago

The most important issue in terms of long-term cost-effectiveness is how much it will actually be used, and how much of the time it is actually full. High Speed Rails or any trains for that matter, are plagued by the inefficiency of having to run at a set schedule regardless of how many tickets are sold, and they ultimately don't justify their own existence in most of America. The hyperloop, aside from attracting new people who otherwise wouldn't have considered rail travel, also has the benefit of having smaller capacity and being able to adapt to demand more quickly. With no stops between SF and LA, if there are no passengers at a certain time, you just don't send the vehicle -its that simple.

devx• 13 years ago

Or you do send them, because it costs so little, and the hyperloop will be mainly self-powered, instead of having them wait half an hour for others to take the ride with them.

RyanZAG4• 13 years ago

Aren't we arguing about the wrong things here? The hyperloop is actually something worth having as it will get you from SF to LA in 30 mins. Even if it costs more and takes less people than HSR, it's still far better than HSR for actually getting you between the two cities in the kind of time people would like. If you could set up these 30 min hops between cities all over the world, you will improve humanity as a whole. That's something worth attempting.

If capacity becomes an issue, you could just add more tracks. If the cost is wrong (and it no doubt is), why is nobody coming up with the real cost so we can compare this properly? Hand waving about 'too low!' is only useful for arguing, not for finding a solution. Are there other ways that the cost could be brought down?

jfb5• 13 years ago

Of course it's not delivering anybody from SF to LA as proposed; as proposed, with the putative cost of 6B, it will take you from Hayward to Sylmar in 35 minutes. Great, but the cost of getting from SF to Hayward or Sylmar to anyplace in the LA basin that anybody would want to go to are not included.

baddox• 13 years ago

Raw speed is obviously valuable, but it will always have to be balanced against construction/operation cost and passenger capacity.

tptacek18• 13 years ago

It will not get you to SF from LA in 30 minutes. You have to get to Sylmar, which is a hike, then get through a security checkpoint; when you get to the other side, you have to drive from Hayward to San Francisco.

HSR plans get around this by terminating in the middle of major metro areas, which they can do because they get to reuse existing rail lines.

glenra• 13 years ago

Trains don't need security checkpoints because trains follow a fixed route - you can't hijack them to cuba, you can't crash them into a building. All you can conceivably damage is the train line itself and the few people in it...and that sort of attack could be done almost as easily from OUTSIDE the train as from inside it.. Our impulse to PUT security checkpoints all over the place is idiotic. The TSA goons haven't won yet when it comes to subways and ski lifts and Amtrak and individual cars (as they enter tunnels or approach bridges) and we shouldn't assume they'll win on this one either.

mistercow2• 13 years ago

The hyperloop is actually something worth having as it will get you from SF to LA in 30 mins. Even if it costs more and takes less people than HSR, it's still far better than HSR for actually getting you between the two cities in the kind of time people would like.

Not necessarily. It depends on demand.

Think of travel time as latency, and volume as bandwidth. If the system is unsaturated, then the 30 minute travel time is great. You show up, get on, and ~30 minutes later you're at your destination.

But if the system is saturated (which seems likely at $20/ticket), then latency becomes more or less irrelevant because you're limited by bandwidth. Sure, once you get on the car, you'll arrive in half an hour. But you will have to wait in line, and that wait will be determined by the volume limitations of the hyperloop. If the hyperloop attempts to serve the same demand as the proposed HSR, a passenger's total travel time will be four times as long.

The solution is to charge more for a ticket. The actual price needs to be calculated in terms of a point where you don't end up with more than 3000 passengers per hour (at which point you break even).

However, even if you do that, it doesn't as effectively solve other problems that the HSR will help with, like total car traffic.

superuser23• 13 years ago

Why would we create one of the most sophisticated transit systems in history and then use standing in a line as the method of reserving a space?

Web-based reservation systems are not hard. Last-minute tickets could be sold at higher price for those that need and can afford them as well.

kevinpet• 13 years ago

There may be some valid points in there, but I don't consider it very productive to get this kind of info from this source. I'm not sure what their agenda is, but it clearly doesn't have anything to do with economics or transportation. From the authors recent articles, I have my doubts he would approve of anything that isn't initiated by government. Consider this article http://greatergreaterwashington.org/post/19330/supreme-court...

Since I lack the expertise to know myself whether the numbers are plausible or will work out, I need to rely on the expertise of others. And one of my ways of evaluating the expertise of others is if they appear to be guided by facts or by an agenda.

moocowduckquack6• 13 years ago

To be honest, it reads like a standard paid-for FUD piece.

ams61102• 13 years ago

Both projects are impractical fantasies regardless.

tptacek18• 13 years ago

Are you able to see the factual assertions in this article and then challenge them? Then do that. Trying to read the author's mind is not only an unproductive way to build an argument, but also an invalid way: he could be taking $2MM/mo from CA HSR lobbyists and it would still be logically possible for him to construct a compelling argument against Musk's plan.

Debating motives is a waste of time. If his piece is all motive and no meat, the article should be easy for you to pick apart. So do it.

Xcelerate• 13 years ago

In the engineering field, I've found there's an issue with a subset of engineers where they get some kind of enjoyment out of saying why something can't be done without providing any suggestions or improvements to make it possible. They just feel the need to be negative and list reasons why something won't work. It's unfortunately common, it's unproductive, and it really gets kind of annoying after a while.

mikeash• 13 years ago

I think it's interesting how people are apparently compelled to bring up all possible objections, no matter how weak, when they really should be concentrating on the strongest ones.

For example, I think the discussions of headway at the beginning of this article are very good, and he lays out both problems and potential solutions, albeit ones that make the system less useful.

However, by the time we reach the end, we get crap like "Clearly he's unfamiliar with the Cypress Street Viaduct." Yes, I'm sure Elon Musk has never heard of that, sure. I'm sure he didn't research earthquakes at all when making his statement. Come on, really?

This kind of nonsense weakens the article considerably, because readers will tend to concentrate on the weakest aspects of it, not the strongest.

tptacek18• 13 years ago

There's already an alternative plan on the table that does SF to LA, city centers in both, in 2 hours 28 minutes.

To mount the argument that engineers and critics should be focusing on rehabilitating Musk's proposal rather than shooting it down, one of the following needs to be plausible:

(a) that door-door transit times on Musk's system will be significantly better than the HSR plan

(b) that construction and operation of Musk's plan will be significantly cheaper than HSR

There are compelling arguments against (a) and (b):

(a) because Musk's system can't reuse existing urban rights of way, it terminates far from either city center. It gets a "~30 minute" estimate, which message boards are eager to latch onto, by waving a magic wand and turning Hayward into San Francisco and Sylmar into Downtown LA. If that was a viable strategy, SWA would still be relying on Islip to service NYC.

(b) Musk's estimated tunneling and el track costs are so low that, were they viable, they'd revolutionize all of the rest of urban planning. For instance, Musk proposes to lower the cost of running viaduct by an entire order of magnitude. No comparable tunnel has been built for anything like what Musk proposes his tunneling costs will be. And the expenses he lays out make optimistic assumptions about the routes he'll be able to use, especially through the mountains.

It's gotta handily beat 2hrs 28min for the route people actually care about, OR be substantially cheaper. These aren't nits: they're the entire motivation for the proposal.

tedunangst• 13 years ago

You must realize you're posting on "I could build that in a weekend" central. When viewed through HN goggles, a train that goes 80% of the distance between sf and la is identical to a train that connects downtown.

Facts, like tweets, have a size limit. "Hyperloop will connect areas relatively near to sf and la" is too long. "Hyperloop will connect sf and la" is a shorter, and therefore better, fact.

dojomouse3• 13 years ago

I find it even more annoying when they're not engineers, and their math is bad, and they get it totally wrong. The number of news stories I saw explaining the Hyperloop as 'like a big pneumatic tube' and showing the twitter picture of the huge fan forced tube as support... even though that's COMPLETELY WRONG... anguish.

But yeah, screw those guys. Much more fun to solve the problems.

moocowduckquack6• 13 years ago

Even if he is right and the math does not add up, I do not think that Musk is likely go to all this trouble to try and boost Tesla sales in California in 2026, which is the earliest that HSR is planned to get anywhere close to connecting LA and San Francisco, and even then it actually only gets as far as San Jose, the San Francisco bit is scheduled to open in 2029.

I can't see a plan involving the idea that in 2029 Tesla would be so dependent on Californian sales rather than global, that it would seek to stop a local rail network from progressing. Especially a plan so convoluted as to involve actually taking time out from running a rocketship business, car company and solar power company, in order to design a rail network that according to the theory, you do not want built.

tptacek18• 13 years ago

He hasn't taken time away from his car company to do this.

moocowduckquack6• 13 years ago

He has taken time to do this, while being involved in running three other concerns. This may not have taken time out of running any of those concerns admittedly, perhaps he gave up reading for a bit, I don't know. But he must have spent some time on it.

He says he was pulling all-nighters to get it ready for the press, and also said “I wish I had not mentioned it, I still have to run SpaceX and Tesla, and it’s fucking hard.”, which seems to indicate that it was squeezing his time.

Unless he has quite a lot of free time, which it doesn't sound like, I can't see how this could have taken no time away from Tesla, especially given what he has stated. It might not have taken that much, but it will have taken some.

zeteo3• 13 years ago

The Hyperloop pods will travel[...] about 30 seconds apart in the tube. They will have a maximum deceleration of 0.5 gs [...] it will take a pod 68.4 seconds to come to a full stop.
That's a pretty significant issue because safe vehicle operation means never getting closer to the vehicle ahead than the distance it will take you to stop. [...] That means that the minimum separation between pods is probably closer to 80 seconds or more.

Two flawed assumptions in here:

1. 0.5 g is the maximum deceleration under normal conditions (see p. 58 in Musk's PDF). Emergency braking would obviously be capable of more. The linear accelerators themselves are spec'd to be capable of 1g, and there's an onboard emergency braking system on top of that.

2. A vehicle that crashes doesn't stop immediately, but continues on its direction of motion due to inertia. That's why the two second rule is plenty safe on highways [1], even though expected vehicle stopping times are six seconds or more [2].

Furthermore, the article is basically an attack on maximum capacity, but that's not a real issue. The system is economically viable if it can get passengers from point A to point B at comfort and cost levels (including recouping investment) that compare favorably with other means of transportation; Musk cites $20 per ticket, which the article doesn't dispute Maximum capacity can always be expanded if the economics work otherwise.

[1] http://en.wikipedia.org/wiki/Two-second_rule

[2] http://www.csgnetwork.com/stopdistinfo.html

ronaldx• 13 years ago

On point 2: if you get jammed in a tube you're going to stop in a much shorter distance than if you're freewheeling on a road.

tptacek18• 13 years ago

Isn't that $20 estimate prima facie incredible? It's based on the capex costs of the system but not opex, right? It presumes that once you build the system, it runs itself for free.

jfb5• 13 years ago

What I don't fully understand is how this is any better than conventional HSR. What are the advantages? Cost, but that remains to be seen. Absolute speed, which yes, but where are the time estimates from Hayward to the Transbay Terminal in SF, and from Sylmar to Union Station in LA?

This whole thing reads to me as purest wind.

EDIT: At least on a conventional train, I can ride from somewhere that's not at one of the endpoints to somewhere else that isn't; and, of course, I can go to the bathroom.

zeteo3• 13 years ago

It seems really low, but I don't really know what to dispute among p. 56 estimates. Energy comes from solar panels. It doesn't seem to factor in maintenance. Even if the cost turns out to be double and we factor in a 20% profit margin, it would still be much cheaper (and possibly faster) than a HSR ticket.

dasmoth• 13 years ago

What fraction of "conventional" public transport costs are labour?

I think (if it gets built!) we'll see very few humans operating or maintaining the hyperloop.

anologwintermut4• 13 years ago

Point 2 isn't necessarily correct when you factor in the effect of debris on bearings.

ackfoo• 13 years ago

People have largely missed the salient points of Elon's proposal:

1) If America cannot understand the potential and purpose of innovative technology, it is doomed to slide into socio-economic, scientific, and technological poverty. The point is that building a slow and expensive HSR is stupid, and people have approved it solely because they are, similarly, too stupid to envision what is possible. The primary point of building the Hyperloop is not to move people physically, but to move them intellectually.

2) the Hyperloop, as designed by Elon, has zero emissions. We should do it for that reason alone, otherwise we are genuinely too stupid to exist, which fact says more about us than any debate. If we do not begin building zero-emissions systems, the debate will not matter because we will be gone.

3) Capacity problems are not an issue. Elon has intelligently anticipated a diminishing requirement to physically move people because of the improvement of telepresence technology. If you still need to travel as much as you did ten years ago, you are an idiot. This trend will only increase. Elon is too savvy to mention this explicitly, but he no doubt understands that the need to move people physically is declining. The HSR will be mostly empty if it opens in 2024 with the capacity required in 2014.

4) Our entrenched institutions have failed us, not because of anything specific that they have done wrong, but simply because they are entrenched. We should build the Hyperloop for no other reason than a little revolution being a good thing, now and again.

ck2• 13 years ago

Plus since oil pipelines constantly leak, how are they going to make pressurized tubes for miles that don't leak and trap pods?

austinz• 13 years ago

Part of the problem is that HSR is fast, technically feasible, heavily used, and economically viable in France, Germany, China, Japan, and other places.

So, the most useful analysis would be:

1. What factors are preventing HSR from being fast, technically feasible, heavily used, and economically viable in the United States? (More concretely, why does California's HSR suck so much when it's been demonstrated that HSR doesn't necessarily have to suck?) Demographics (e.g. population density and layout)? Political and legal constraints? Terrain? Culture?

2. How does the Hyperloop mitigate or sidestep these problems, due to its superior specifications or design differences from HSR?

3. For additional insight, what would California's HSR have had to do differently to mitigate or bypass these issues, and would it even have been possible?

ams61102• 13 years ago

Americans prefer cars. It's that simple.

Aloisius• 13 years ago

It seems some people don't quite understand what the big deal is about not terminating outside the major population centers.

For people from the east coast, imagine a train system that claimed to connect New York and DC, but actually terminated in Manville, NJ and Bowie, MD.

DanBC• 13 years ago

Ryanair (budget European airline) does this.

EG: They fly you to Paris, not CDG or Orly, but to Paris Beauvais.

dojomouse3• 13 years ago

The capacity constraint accusation on the grounds of spacing and max G is pretty bogus. Firstly, there's nothing wrong with running at far more than 0.5g in an emergency. You think a plane stays below 0.5g when it crash lands? You just have to make sure people aren't badly injured, not pamper them - and make sure such emergencies are very rare.

Where the author really gets it wrong though is in saying "Maybe he can resolve that by using larger pods. But of course, a larger pod will weigh more. And that will probably mean using stronger steel for the tubes, which means that the cost will go up". That would be true, but if you're happy to resolve the issue with larger pods then you should be equally happy to resolve it with groups of smaller pods travelling at smaller separations. A 737-800 seats around 150 people. Hyperloop passenger capsules seat 30. So no one should have any conceptual issue with running 5 hyperloop capsules in convoy with separation of a couple of seconds. This 'couple of seconds' still means almost 1km, so they're certainly not sharing the same segments of tube, so you don't need to scale the tube design at all. It's still dirt cheap, and you have plenty of capacity, and it's still MUCH safer than a plane because if one capsule has a fault the others following can still likely stop in time (given they're all decelerating at roughly the same speed).

Musk's Hyperloop math doesn't add up

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