MIT Team Tops Hyperloop Design Competition (google.com)

The Dallas Morning News reports that a team from MIT has topped competitors from around 100 universities around the world at a competition held on the campus of Texas A&M by presenting a workable design vision for Elon Musk's dream of a hyperloop. The hyperloop concept, mentioned several times before on Slashdot, involves rapidly shuffling passenger pods through 12-foot-wide tubes evacuated of air, and would mean terrestrial transport at speeds topping those of commercial air travel. From the Morning News article: Delft University of Technology from The Netherlands finished second, the University of Wisconsin third, Virginia Tech fourth and the University of California, Irvine, fifth. The top teams will build their pods and test them at the world's first Hyperloop Test Track, being built adjacent to SpaceX's Hawthorne, Calif., headquarters.

Comments

Nature Abhors a Vacuum

[ebonum]

I think this hyperloop is going to crash into the harsh realities of dealing with a vacuum.
a) It takes a huge amount of energy to pull a good vacuum. This thing needs to be at 0.02 psi. Vacuum pumps are really inefficient. They mostly take electricity and generate lots of heat.
b) Running the pumps is going to cost. Vacuum pumps burn out/need maintenance.
c) 0.02 psi? That translates into a HUGE amount of force trying to crush the tube. 14 lbs/ square inch. It adds up QUICK. Better hope some 13 year old doesn't think it would be funny to put an M-80 on this thing. It might implode and kill anyone in the pod.
d) Ever to try keep a vacuum? Good luck finding all the little leaks in the seals over X miles of this tube. Getting it evacuated once will be difficult. Now try to keep it sealed for a year. You have the stress of the pods flying through this thing. You have heating and cooling cycles every 24 hours.

It will make a awesome science project for some students spending lots of other people's money.

Re:Nature Abhors a Vacuum

[Rei]

You're right, it's not 10mm or 20mm.

It's "20-23mm". Basically, "nearly an inch", for Americans. And not only that, it's reinforced with stringers.

Steel is cheap. Seriously, run the numbers - it's only a small fraction of the total cost. 3.14159*((2,23m/2 + 0,0215)^2 - (2,23m/2)^2) * 579800m = 88173 cubic meters of steel = 687753 tonnes of steel = ~$138m of steel. Insignificant compared to the total project costs. Now, of course, that's not the cost to build the tube - pipe costs more than raw steel, and the cost to build is well more than the raw materials. But as for the concept of "Oh my god, that's a crazy amount of steel, it'd be way to expensive!"? No. No, it's not.

Anyway, the low air pressure isn't even the main load on the tube, it's the weight of the capsule + tubes between columns.

Re: Nature Abhors a Vacuum

[Rei]

Being borne by the mass of nearly 100 Eiffel towers, in a form naturally resistant to pressure (a cylinder).

Seriously, we deal with far more extreme pressure differentials in pipelines all the time. There's absolutely nothing exotic about the proposed pipeline. It's fairly large, but with nearly inch-thick steel (20-23mm), buckling isn't even close to a risk; the thickness of steel required for a 2,23m cylindrical shell to not buckle is a small fraction of that. The thickness of the tube is more governed by the issues of loading between columns than by the internal pressure.

Re:Nature Abhors a Vacuum

[Rei]

CA HSR is a $70B project. Hyperloop is a $6B project. Re: throughput: Hyperloop pods launch every 2 minutes during off-peak (30 seconds during peak) with 28 passengers, aka minimum of 20k per day, up to 80k per day depending on demand. HSR trains leave every 5-10 minutes with 450 passengers; they're ultimately hoping for 110k daily ridership, but it's expected to begin at well less than that (and critics think they're overestimating ridership by as much as 70%, but that's neither here nor there)

In short, HSR is higher throughput (it's designed to service a larger area), but not by the sort of margin that justifies the order-of-magnitude budget difference. It's also significantly slower, significantly more energy consuming, and significantly more cost per ride. Now, you can doubt Hyperloop numbers - that's fine. But that's not what this conversation is about: this conversation is about what the point of Hyperloop is: far better throughput per dollar at far better passenger cost, energy consumption, and trip time. That's the point. Whether they can pull it off, that's something they have yet to prove.

Honestly, I personally don't like how Hyperloop was set up as a competitor to HSR. Because it's really something new, something in-between high speed rail and air travel. I think they would have made far fewer "enemies" had they presented their initial pilot route as LA to Las Vegas. Probably could have gotten a lot of investment money from casino operators that way, too.

What were the criteria the designs judged on?

[mykepredko]

TFA is somewhat lacking in actual information.

I'd like to know what makes one design of a hyperloop capsule better than another.

Anybody have any links?

More information

[Harlequin80]

From http://www.gizmag.com/mit-hype...

The MIT team's winning design details a 250 kg (551 lb) passenger pod with an exterior crafted from carbon fiber and polycarbonate sheets. With a passive magnetic levitation system comprising 20 neodymium magnets, the pod is designed to maintain a 15 mm (0.6 in) levitation gap above the track.

The team says with the lowest available tube pressure available of 140 Pa, the pod should be accelerated at 2.4 G and have 2 N aerodynamic drag when traveling at 110 m/s. The design also features a fail-safe braking system that automatically brings the pod to a halt should the actuators or computers fail, and low speed drive wheels that can move the pod forwards or backwards at 1 m/s in an emergency situation.

Re:pneumatic tubes?

[Rei]

No relation whatsoever, except that both involve a tube. Same with a vactrain. Hyperloop is "none of the above".

Lift:
  * Pneumatic: (Usually) wheels (though sometimes aero or maglev)
  * Vactrain: Maglev
  * Hyperloop: Aerodynamic

Propulsion:
  * Pneumatic: Backpressure
  * Vactrain: Single-segment coilgun
  * Hyperloop: Multi-segment coilgun

Dealing with air resistance:
  * Pneumatic: Frequent stations that have to move a lot of air
  * Vactrain: Hard vacuum, effectively no air resistance
  * Hyperloop: Compressors shunt bypass air
 

Re:Design and build are two different things...

[Rei]

The cost for pipeline construction is... well, the cost of pipeline construction. We already make giant elevated pipelines thousands of kilometers long. The costs aren't prohibitive, and are far less than rail. Compared to a big oil pipeline project, Hyperloop has some advantages and disadvantages.

Advantages:

  * Significantly less column loading
  * No fire risk
  * No spill risk
  * Easier thermal management
  * Easier permitting (one of the biggest costs)
  * Less NIMBY opposition
  * Lower pumping loads/power consumption

Disadvantages:

  * Much greater need for internal precision (requires an internal polisher)
  * Must be maintained highly straight, even during thermal expansion
  * Human lives directly involved, not just indirectly.
  * Larger diameter than most pipelines; comparable to the size of the worlds' largest pipelines
  * New technology

Neutral/shared:

  * Both require regular monitoring equipment, although different types
  * Both need to meet stringent standards again natural or manmade disasters, such as earthquakes or car accidents
  * Oil requires valves/tees/access points; Hyperloop requires periodic emergency exits
  * Fairly similar wall thicknesses, though an oil pipeline of this diameter would have slightly higher walls due to the higher loading

I see no reason to expect the costs (for a given diameter) to be off from each other by orders of magnitude. And the cost of the steel itself is almost irrelevant compared to the total costs (see the calculations above).

And no, you could not "build a lot of new track for passenger and freight service" for $6B. California's HSR project for example is $70B. Part of the main impetus of Hyperloop was to be significantly cheaper than HSR while providing higher transit speeds (although to be fair to HSR, Hyperloop is not designed as a direct replacement; it's only point-to-point, no intermediary stops, and lower net throughput - more of an cross between rail and air travel). The main way in which it's cheaper (in addition to not having all of the stops, aka having to go through towns, and instead largely sticking to rural highways where right-of-way and permitting is much cheaper and easier) is that by dividing the load out into numerous smaller vehicles, the peak "track" loadings are far less with Hyperloop. Loadings are strongly correlated with cost.

Oh wait, its not tech and its not green.

That's a bizarre claim, given that its energy per passenger mile is far less than any other current form of transportation and it's designed to generate its own power via solar.