Elon Musk Plans To Build Hyperloop Test Track

An anonymous reader writes that Elon Musk wants to speed up the development of his proposed 800-mph tube transport. "Billionaire and entrepreneur Elon Musk is getting more hands-on with the Hyperloop. Musk, who heads up both space transportation outfit SpaceX and electric-vehicle maker Tesla Motors, casually announced via Twitter on Thursday that he's decided to help accelerate development of his vision for near-supersonic tube transportation, first outlined in August 2013. Musk said he will build a five-mile test track for the still-theoretical system for students and companies to use. A possible location would be Texas, he added, where presumably there is plenty of flat land to go around."

Comments

Re:"plenty of flat land to go around

[Rei]

If you think this is like a pneumatic tube, then you know absolutely nothing about this.

Hyperloop is a system involving partially evacuated (not hard vacuum) tubes. The reason is that hard vacuum is much more difficult to achieve and maintain. The very low (but not vacuum) pressures offer little resistance, but do present a problem: you can't allow air to build up in front of the craft. Hyperloop solves this by a system of watercooled battery-powered compressors.

A pneumatic tube is propelled by pressurized air behind the projectile expanding, with lower pressure in front of the projectile. Hyperloop involves nothing of the sort - it involves magnetic accelerator segments for propulsion. Only a few reboosts would be needed over the length of an LA to SF run due to the low air resistance.

Re:"plenty of flat land to go around

[Rei]

The air on the outside is still going to *aggressively* want to rush in through any little crack.

Air is not magical. You can't put a pinprick in a partially evacuated tube and have it just suddenly equalize. Viscosity on the order of the size of small cracks highly limits the rate at which air can migrate in. A little crack or a leaky seal is simply not enough to overcome an air compressor.

To put it another way: the pressure differential here is approximately one atmosphere. Large trunk natural gas pipelines have a pressure differential of about 13 atmospheres. By your logic, a natural gas distribution infrastructure is utterly impossible because "the natural gas on the inside is still going to *aggressively* want to rush out through any little crack".

Let me see if I've got this straight: we can't build regular maglev trains because they're super-expensive (the engineering, construction and maintenance would be incredibly difficult), so... we'll just make it that much harder by wrapping a (partial) vacuum tube around it???

First off, let's make this clear. Hyperloop is not Maglev. In fact, the design document notes that they could use Maglev, but dismisses it as too expensive: "A viable technical solution is magnetic levitation; however the cost associated with material and construction is prohibitive." Hyperloop uses air bearings - skis operating in ground effect with the pipe.

Maglev trains are expensive for many reasons. The cost of having the track be able to provide forward propulsion however usually represents only the tiniest fraction thereof. First off, you have the reasons that rail is expensive, period (right of way costs, environmental reviews, and all of the other overhead). Then you have to have the entire route be able to lift up a multi-dozen to multi-hundred-tonne train. Not just propel, but actually hold it stably in the air, which is a far more difficult challenge for many reasons than propulsion - you either have to have an extremely precise computer-controlled fluctuating magnetic field in a train with hanging magnets, or you have to have the entire track be magnetized or be able to magnetize, in a manner that resists dynamic instability.

Hyperloop only involves propulsion, and the accelerators represent just a few percent of the length of the track. It's a tried and tested technology, use around the world, and their budget for it is in-line with industry norms. There are all sorts of trains today that use linear accelerators, almost all of which represent way more length of accelerator than Hyperloop needs. Examples include

Airport Express in Beijing (opened 2008)
AirTrain JFK in New York (opened 2003)
Detroit People Mover in Detroit (using ICTS) opened 1987
EverLine Rapid Transit System in Yongin (opened 2013)
Kelana Jaya Line in Kuala Lumpur (opened 1998)
Scarborough RT in Toronto (using UTDC's (predecessor) ICTS technology - opened 1985)
UTDC ICTS test track in Millhaven, Ontario
SkyTrain in Vancouver (Expo Line (using ITCS) opened 1985 and Millennium Line opened in 2002)
Limtrain in Saitama (short-lived demonstration track, 1988)
Nagahori Tsurumi-ryokuchi Line in Osaka (opened 1990)
Toei edo Line in Tokyo (opened 2000)
Kaigan Line in Kobe (opened 2001)

Re:"plenty of flat land to go around

[Rei]

Said who? It costs the same as a BMW 535i, yet only goes 265 miles. That's *not* revolutionary.

Given that the previous longest range before Tesla came around was in the ballpark of 40% that far and was produced by the hundreds, not the tens of thousands, and that the model S outperforms the BMW 535i, and has higher customer satisfaction ratings, and the whole teensy detail that no new US manufacturer that has anywhere near that order of sales for any type of car (let alone a radical new one) has been established since 1925... yes, that is damned impressive.

Using an engine designed by someone else

Where'd you get the impression that the Merlin was designed by someone else? Merlin is the most from-scratch engine design for an orbital launch vehicle in the US since the 1950s. It shares a few parts with older engines, such as the pintle injectors, but the vast majority of the engine is of brand-new design. The engine shares some similarities with work done at TRW, but it's not a TRW engine (doesn't even burn the same fuels). The reason that it's sometimes referred to as a descendent of work done at TRW is because TRW's former chief engineer is SpaceX's head of propulsion. He was tinkering on rocket engines in his garage that he felt he couldn't get support for at TRW when Musk picked him up; he proceeded to use his new position to create what became the Merlin series.

It's great engineering and no-nonsense construction from a company that hasn't (yet) become bloated by sucking on the DoD & NASA teats, , but that is *no* revolutionary.

Nice dodge: let me repeat: #Beating Ares 1 to the ISS for 2% of the development cost, on a rocket cheaper than the Russians and the Chinese, *without* the reuse that it was designed for": how the heck is that not bloody amazing and something to be celebrated? If it's so easy, then why hasn't everyone been doing it? And yes, people like you were all over the place here a few years ago saying they'll never get off the ground.

For it to be revolutionary, they'd have to come up with something *really* game changing, like... a fuel better than LH2/LOX which doesn't corrode everything it gets near

No, something that's "really game changing" is dramatic reductions in the price of getting to orbit, with serious potential for even more significant drops if reuse works out. That is bloody game changing if the term "game changing" has any meaning. The propellent mix is irrelevant. You can have the highest ISP fuel mix on earth and still cost a bloody fortune to get to orbit if it's not economical. The Russians beat the US for the longest time with much lower performance engines for that reason.

However, and sadly, getting a booster to land on a floating platform is "mere" engineering

Any more difficult challenge than that and you might as well just call it "magic". You don't get much harder in the rocketry world than something like that. Rocketry *is* engineering, and adding the word "mere" is just an insult.