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Summary:

Elon Musk just unveiled the design of the Hyperloop, which could enable us to travel 800 miles per hour between SF and LA. Here’s some potential hurdles with such a plan, from a Navigant Research analyst.

Hyperloop seats
photo: Elon Musk

If a prototype of the Hyperloop – Elon Musk’s futuristic superfast train – ever gets built, it will have to overcome some very significant engineering challenges that may or may not be solvable. After reading through the published document that explains how the concept works (it reads something like a cross between a patent application and a Popular Science article), I can’t say that it will or it won’t work.  But I do have opinions on the plan’s strengths and weaknesses.

HyperloopI should point out that, while I’m not an engineer. I have helped design systems that use compressed air and deal with the aerodynamics of large structures. I’ll start with my opinion of what the plan has going for it, followed by important challenges that still require a solution.

The most important element of the concept paper is that it doesn’t really invent anything.  Everything described in the plan has been built for other applications and proven to work. The electric engine and battery pack would be variations of what Tesla has built in the Model S. The steel tubes, through which the passenger pods would travel, would be carefully aligned versions of pipeline tubing. The compressor on the front of the pod would be similar to any industrial compressor.

Not So Outrageous

Every entrepreneur claims that his or her idea will be cheaper than the currently available technology, and just about every entrepreneur turns out to wildly overestimate how cheap his or her system will be. Musk’s paper does an excellent job of detailing exact pricing of each element of the project so that there’s no magical thinking involved in the pricing expectations.

Musk began this project when he realized how awful high speed rail is as a transportation solution. Although we’re comfortable with trains, few of us really appreciate how much it costs to build a brand new rail line. The $68 billion price tag for California’s rail project seems outrageous, but it’s actually not too expensive in the world of high-speed rail. It’s worth considering that perhaps the craziest option is to spend $68 billion on a more conventional alternative to the Hyperloop.

hyperloop capsule in tubeThe biggest concern with this plan has to do with temperature. The pod will be compressing air and expelling it downwards and backwards. All that air compression creates an enormous amount of heat, which can damage the pod and its machinery.

Musk’s solution is to add to each pod a water tank that will capture that heat and turn it into steam to be collected at the next station. Although the thermodynamic calculations are correct, a small pod with only a few cubic feet of room for a heat exchanger leaves little space for an efficient exchange of heat. That means that the flow of water must be increased, requiring a lot more water on board. There may be an elegant solution for this challenge, but it’s not in Musk’s current paper.

Wind stress is another challenge. Any structure elevated 100 feet off the ground is going to be under a lot of wind pressure, which will act on it in weird and sometimes multiple directions.  If that structure is a heavy tube stretching hundreds of miles in either direction, you effectively have a big sail. Will the concrete pylons be powerful enough to resist that pressure?

The Hyperloop may or may not ever get built. But there are few examples of a billionaire spending his own time and money on giving the world a unique idea that’s been well thought-out and clearly worth investigating further. Musk’s vision and audacity should be applauded.

This article originally appeared on the blog of Navigant Research, a market research and consulting team that provides in-depth analysis of global clean technology markets. Navigant Research is also a partner of GigaOM Pro, GigaOM’s premium research service.

  1. It may be more feasible in the short term for intercity transport, not necessarily coast to coast. Sounds good.

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    1. That’s exactly what Musk says in the paper. He suggests that supersonic aircraft are impossible to beat for any trip lasting more than a few hundred miles.

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  2. Great idea but where do you go to the bathroom?

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    1. 30 minute transit. hold it.

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  3. “Will the concrete pylons be powerful enough to resist that pressure?”

    Seriously, that’s it?

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  4. Use Tesla eV’s expensive packaging as a distraction to kill electric cars green infrastructure.

    This trick can be repeated to kill the green and affordable high speed rails infrastructure as well.

    Brilliant!

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  5. It’s sad when the first 2 words of the title contain a grammatical error.

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  6. Biggest problem I see is that there is only one lane in either direction. If there is a problem OF ANY KIND, (maintenance, disabled pod, etc.) the entire route needs to be shut down.

    Speaking of disabled pods, if a pod goes down, explodes, whatever, then the pod behind it is only 30 seconds behind it. Can a pod slow down from 700 miles per hour to full stop in 30 seconds?

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    1. Depends largely on the g’s you are willing to tolerate. An emergency deceleration can be much more intense than regular operation, easily in the 3-4g region (29.4 – 39.2 m/s^2). At that rate you’d decelerate from 340m/s (speed of sound) to a standstill in roughly 10 seconds, giving you an additional 20 seconds of reaction time. The rapid deceleration can be achieved in a number of ways, ranging from mechanically contacting the tube walls via specially designed friction pads to solid-fueled retro rockets. Capsules further than 1 accelerator section away can be decelerated electrodynamically at the next active section and then come to a stop using regular wheel brakes.

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  7. I got the impression from reading Mr. Musk’s PDF that the tubes are not standard pipes, but custom-built to Hyperloop’s specs.

    Probably some wind-tunnel testing for scale models will help to refine the design characteristics needed to withstand wind conditions. That seems like a small issue, easily addressed.

    But the heat dissipation problem you identified does seem to be a large hole in the engineering concept. Mr. Musk’s PDF leaves capsule cooling poorly addressed, and tube cooling wasn’t addressed at all.

    I didn’t see any toilets in the design, either. They’ll need them!

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  8. Stopped reading at, “I’m not an engineer.” Then I decided to give it another chance. I shouldn’t have.

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    1. If you stop reading technical discussions at “I’m not an engineer”, then you can’t read Musk’s paper on Hyperloop. He’s not an engineer either.

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      1. Do you think all of the CFD diagrams and the like appeared out of thin air? The guy employs literally hundreds of engineers. Not to mention that he is a *physicist*. He has a BS in physics from the University of Pennsylvania. And he’s on the board of the National Academies of Aeronautics and Space Engineering and the Stanford Engineering Advisory Board.

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      2. No – he’s a physicist running two of the most successful innovative companies in the country instead of an MA in Near East studies. I know who I’d go to for a tech opinion. Get over yourself!

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    2. Sam needs to learn to stop digging when he’s in a hole.

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  9. An article about nothing, anyone?

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  10. You need to go to bathroom every 30 minutes?! Ask for Pampers to be included in your ticket price…

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