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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.
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.
a,b) 0.02 PSI is extremely mild by vacuum standards. By contrast, ultra-high vacuum is defined as less than 0.0000000000145 PSI. 0.02 PSI is not a difficult pumping challenge by any stretch. And after the initial pumping, the only vacuuming requirements are 1) airlocks at the end stations, and 2) overcoming the rate of leaks. The pump sizing and power consumption needed is well less than with equivalent-sized oil or water pipelines.
c) And too bad inch-thick steel is such a fragile, flexible material, utterly vulnerable to M80s! Oh wait....
You do realize that the buckling force of a cylindrical shell is actually far easier to work out (with safety margins) than the physics calculations for the structural stability of the capsules, right? Or for that matter, cars, airplanes... throw in buildings while we're at it.
d) The plan is not to "find all the little leaks". The little leaks are the only reason that any continued pumping is required at all. Only major leaks need to be found. The pipeline is to be made by the same technology as makes our water and oil pipelines today (automated orbital welding), plus an additional finishing step on the inside.
There are a number of serious issues that the Hyperloop teams need to show that they need to overcome. You didn't hit on a single one of them.
It's times like this I wish I had a friend named 'The Professor'.
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.
It's times like this I wish I had a friend named 'The Professor'.
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
It's times like this I wish I had a friend named 'The Professor'.
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.
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.
It's times like this I wish I had a friend named 'The Professor'.