Hyperloop : pie in the sky or is it time?

Factual Questions
1

I’d appreciate commentators glance at the original source before commenting : link to pdf.

To summarize : the tunnels are sections of 0.8inch thick steel tubes, polished on the inside and welded together using friction-stir seam welders. Pipe - Friction Stir Welding - YouTube

Most of the tubeway is supposed to be elevated to minimize construction cost, but due to hard constraints on radii of curvature, there have to be some sections of underground tunnel.

If Elon Musks’s numbers are even remotely realistic (I think he neglected to include the R&D costs to actually design and prototype the individual cars, they might cost a million each or so to manufacture but they are almost as complex as a pressurized jet aircraft) then by my rough estimates we could replace most major freeways in the united states with hyperloop trains, as well as crisscross the country with these things. I don’t think his statement at the beginning, that routes over 1000 miles would be better served with planes, is correct for heavily trafficked corridors. You don’t have to pay for jet fuel or pilots with this kind of transportation.

How could this system fail? At 800 mph, the individual cars will have an incredible amount of kinetic energy - but there are wheeled vehicles that have traveled on the Arizona salt flats at nearly that speed. It seems at least possible that the emergency wheels on this system might be able to save the passengers if the air supply to the skis were to fail.

The original document mentions TSA style screening for every passenger. I wonder if that’s really necessary - unlike an airliner, there’s no way to hijack a hyperloop car to kill people on the ground, and there are not enough people in an individual car to be worth the expense of screening. After all, there’s 30 or so people standing in line in a grocery story or movie theater or any number of other public places, and a terrorist could murder them with a gun or bomb as various events have demonstrated.

I suppose that if a bomb destroyed a hyperloop car, it could potentially leave lethal debris in the tunnel that would kill people in following cars who cannot slow down in time.

Another topic not discussed is telemetry - a metal tube will block radio signals going through it, and it’s all a single conductor, so the only means that comes to mind for communicating between the car and the control systems in the track would be RF signals from antennas in the front and rear of the car, reflected down the tunnel to antennas embedded in the tunnel walls. This would have to be how the high speed internet access for passengers was delivered as well.

2

Hey Habeed! Welcome to the Dope. Nice first post! Stuff like this belongs in General Questions, and I’ve reported this post to be moved there, where you’re far more likely to get quality commentary.

3

Oops, I meant to put it there. Hope it gets moved. Thanks for the comments, I felt that parts of this post are a little shakey. How can you talk about the “straight dope” about something that doesn’t exist yet, even though it looks like nearly everything you’d need to build this baby can be purchased.

4

Welcome to the SDMB, Habeed!

I’ve moved your thread from ATMB to General Questions, where, hopefully, someone will be able to weigh in on the issue.

twickster, for the SDMB

5

It won’t happen and here’s why (my opinion)

Too costly to build. He underestimates the true cost
Overselling the capabilities. It won’t go that fast, you won’t be able to get from point A to Point B that quickly.
Because it won’t live up to the hype, there will not be sustainable use to make it profitable.
It will take up a LOT more land than he is suggesting.
Too dangerous. Very little needs to go wrong at those speeds to have catastrophic deadly consequences.
It will be under repairs for a large part of the time, shutting down the whole system. One stuck car, means the whole tube is backed up behind it. This will happen often.

Basically, not enough need, interest (cash flow coming in) to justify the cost of researching, constructing and building.

6

There has never been a high tech project in history that went from concept to implementation without years of painful experimentation to overcome problems that weren’t - or couldn’t be - seen in advance. That alone is enough to relegate this to pie in the sky.

I’m also extremely suspicious of his cost estimates. There’s a lot of expensive engineering required for every piece of this. His $6 billion estimate is about the Keystone pipeline cost. That’s an established, much lower tech piece of engineering. I’d multiply the costs by 10 as a starter. That might still make it worth while, but it changes every other aspect of financing. He needs millions of passengers per year to return costs even with his lowball figure. By my calculations, that would require near 100% capacity at all non-maintenance periods.

One more problem to consider. These tubes are required to work perfectly and in unison from start to finish at every second. Any flaw and the entire system stops working. What happens when a breakdown occurs - as it must - and people are 200 miles from the exits? How do you get them out? For that matter, how do you do regular maintenance? You have a 1000-mile system that needs to maintain tolerances to seemingly millimeters. What does he have to say about this?

Well, I’m convinced. That covers every possibility.

Build a 10-mile section. See what happens. And remember that his Space-X has been around for more than a decade, using proven technology, and has never put a person in orbit. How far out does that put a Hyperloop?

7

There’s a couple of other threads active as well:

I do have to say that reading the PDF makes it seem more plausible than it does just reading the articles and discussion.

8

I’m not sure that this concept needs three separate threads, but anyhow a big advantage that Elon Musk is claiming this will cost “only” six billion against the seventy billion dolllar projected cost of the high-speed rail project that’s been approved in California. One reason for the lower cost appears to be that he’s proposing to locate the tube above the I-5 median. I believe the high-speed rail train would require land to be acquired. But why can’t the high-speed rail project also be located on pylons above I-5? (I believe that’s the approach used for the JFK Airport AirTrain over the Van Wyck Expressway.) Also, the high-speed rail project has intermediate stops and I don’t think the hyperloop concept allows for these.

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I don’t know how to multi-quote so I sacriliged and went inside the quote brackets.

10

Very interesting.

I think the reason Elon thinks longer distances are better served with planes is due to travel time. Note that he’s proposing supersonic aircraft for those longer distance travels. I think his feeling is that for longer distance, there is not the economic incentive to drive creating this system over existing air travel.

My first observation is that he proposes using water tanks to cool the air and generate steam, which is then exchanged at each station to prep for the next trip. Since he has a steady supply of steam, I would suggest considering how to capture the energy, say creating a steam generator plant at each station.

My second observation is that he has a lengthy steel tube with a large sliding mass running through it. I would be concerned about the generation of charge in the steel tube itself. Good grounding and insulation will be a necessity.

11

Nice poster name / post combo.

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I don’t think it’s likely within the next 20 years but I suspect it’ll be brought to life sooner than you think. I can see smaller nations taking an interest to this also.

Probably the biggest question mark and i agree it’ll be a lot more than the quoted 6 billion figure. 6 billion for 350 miles is roughly 17 million per mile, which is much lower than what light rail costs per mile and that’s with technology we know how to manufacture.

I’m not saying you’re wrong, but I’d like to know why you think that.

It won’t make up the volume that planes, trains, and automobiles carry but they can charge well beyond the $20 quoted price. I’d say anywhere from $1000-$5000 a ticket. There are definitely enough rich people to fill the need of the TINY supply they’re generating: a 28 man car leaving every 2 minutes.

I google-flight checked how many planes were taking off between La/Burbank and SFO/Oakland yesterday. 1042 flights. I think think some of those first class passengers will definitely opt for the tube instead of commercial flying.

Any moreso than flying or driving?

Yeah. that’s what I thought as well. There would have to be multiple tracks, waystations, etc. It’s not as easy as just a tube.

At the moment, I certainly agree with most of your concerns. I just don’t see it as being insurrmountable within the next 20 years.

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28 people leaving every two minutes is 7,348,400 people a year which is as about NOT TINY as you can imagine. Worse, Musk actually projects that number EACH WAY as part of his cost estimate!

Holy Flying Squirrel, Rocky! He requires 100% capacity and availability with not an empty seat or a moment of downtime for maintenance in both directions! That’s how he gets his 20-year return.

And that is nuts. Say that the Hyperloop completely eliminates air travel between the two cities. That’s currently running at about 3,000,000 annually. He has to quintuple that number. That means taking every car off the road as well. And adding new travelers on top of that.

It’s impossible to make the numbers work. The costs are too low and the potential passengers are too high. Either it’s run as a subsidized governmental service (heresy!) or the payback period runs into the next century. And that’s supposing for a second that it would work.

We won’t know until somebody starts serious r&d on this. I’ll bet that when this thread is brought back as a zombie in 2023 we’ll still be waiting.

14

As I implied in my thread, I think that Musk’s Hyperloop concept isn’t ambitious enough. He’s proposing to develop an entirely-new class of vehicles, with all the experimentation, work, and testing that implies, for only about a 2x increase in speed. Take a look at Wikipedia’s list of non-rocket spacelaunch concepts. Some of them look like they could be adapted for surface-to-surface transport and also implemented gradually. Maybe he should be looking there?

15

Systems like this fall short of airplanes for long distances because of the infrastructure needs. No matter how far you’re flying, you need the same amount of infrastructure: One airport at each end. With any sort of train, though, the necessary infrastructure is the track, which is proportional to the distance you’re traveling.

16

Put this almost anywhere other than California and it gets 20% more plausible.

17

I think Sigene hit it on all points. 6-10 Billion is absurdly low for something this ambitious. The OP mensions vehicles on the salt flats. Perhaps I’m mistaken, but isn’t it a not-rare occurance for those guys to end up as greasy smears across said salt flats? I’d think there’d be very little margin for error in such a system.

18

The reason I feel perhaps too optimistic is that nearly all of the pieces of hyperloop you can buy right now, today.

The steel tubes that it is composed of? Pick up a phone and call an ironworks in China. They’ll have em ready by the time you get to the next step.

The concrete pillars? Ditto. The polishing robot to clean the inside and machine it to close tolerances? Yep.

The electric motor driven turbofan that compresses the air in front of the car? That one will cost ya, but several companies that make jet engines can do it, it’s a straightforward exercise.

The control moment gyroscopes or reaction thrusters to stabilize the cars? SpaceX has both, working, in an actual spacecraft. The huge battery pack to power the electric turbofan? That’s just a few Tesla battery packs stacked on top of each other.

Body? Tesla’s got the stuff to make that. Sealed hatch? SpaceX has those, though admittedly they aren’t gull wing doors. I think a more traditional sealed hatched like on an airliner that has to open inward is a better idea, so it CAN’T open up and vent the car’s air into the vacuum tunnel. Seats? ditto.

Stretched out linear motor? Tesla deals with all of the components needed on a daily basis. Vacuum pumps? Just pick up a phone and order it. Solar panels? China will sell them, cheap.

Designing the control system for the individual car and the whole network? SpaceX has a team that has already done this for a spacecraft, cheaply.

The one piece of the puzzle that makes this a non starter is that even if he’s completely right, and it only needs a trivial amount of land to put the base pillars for the network, it’ll be like pulling teeth to get California to provide the land.

One comment : a couple of people stated that if a capsule fails, the network stalls.

This is true, however, keep in mind that the capsule is going at 800 mph in a near-vacuum. If power fails, it’s going to keep going for many many kilometers.

You could build the capsules with redundancy - use 2 electric motors with independent power controllers to power the jet engine in the front, multiple independent Tesla-derived battery packs.

The other “non-starter” is that TSA style security is stupid. The engineering goal would be to make it where if a bomb or something destroys an individual tube-car, it won’t kill the occupants in the tube car that is 27km behind it. And therefore, if the worst a terrorist could do is to kill the occupants of the tube-car he is in, and he COULD have just smuggled a ceramic knife or something, then there’s no point in having invasive security.

19

Yes perhaps some of the technology is here now, but …how do you know that a tube of 0.8 inch steel is enough? Once you get into the nuts and bolts of it, you might need 3 inch steel; or 5 inch steel incased in 2 feet of concrete. These are the details that are just guessed on in the current business case, that very likely (again my opinion) are going to be found to be insufficient. Things like this will cause severe cost overruns.

ALso note, that I’m not so much a downer on the technology. The more important driving factor here is economics. There just isn’t enough desire to spend that kind of money to get to the places with that sort of speed.

Witness the Concord. We have the technology to build these planes, but we don’t; simply because there aren’t enough people willing to spend the money for a ticket to get there that fast.

We can have flying cars, hotels on the moon, cities underground…the technology is there; we just don’t want to do it that badly.

20

one technical question that I don’t understand. propulsion of the cars requires higher pressure on the backside of it vs. on the front side. Is this correct?

you need a relative vaccum on the forward end compared to the rear end. How do you get multiple cars going through a tube. Won’t the high pressure side (back) of the first car have to be the lower pressure side (front) of the second car? Wouldn’t the back of each car have to be higher pressure the the back of the car in front of it? This seems like an unsustainable series of increasing pressures.

Any help on explaining that to me?