Vactrains

[Razor235]

This is an interesting form of transportation I found about today. Essentially, it is a tube partially or completely devoid of air, with a MagLev train inside. Theoretically, this could allow for speeds of 350 - 4000 MPH (563 - 6400 KMH), or about mach 5, allowing a trip from Beijing to New York City in 2 hours. While as of yet unbuilt, this seems like a promising form of transportation to me, as we already have the technology to do it.

My only concern is how it could you could run it through (or over) an ocean. One of my sources shows an image of it being supported by anchor tethers around 350 feet underwater, but that would require lots of specialized equipment, plus anchor cables that can reach several miles long.

So, what do you guys think of this?

Sources:

http://www.popsci.com/scitech/article/2004-04/trans-atlantic-maglev

http://www.dailytech.com/China+Plans+1000+KPH+Super+Train/article19268.htm

http://et3.com/

http://www.wpi.edu/Images/CMS/Goddard/Vacuum_tube_patent2.pdf

http://en.wikipedia.org/wiki/Evacuated_Tube_Transport_Technologies#Evacuated_Tube_Transport_Technologies

This Cracked.com photoplasty for making me aware of this

Related idea, involving a propeller-driven train in a hydrogen atmosphere

http://www.supersonictubevehicle.com/docs/STV%20--%20Denizli%20%281%20Jul%2010%29.pdf

[astropapi1]

So this would be a super fast train traveling on an underwater vacuum-sealed tube. Amirite?

Sounds cool.

[Nuke]

i remember seeing one of these on an episode of seaquest (yea im that old).

anyway the best solution would be to cross areas of the ocean that are fairly shallow. the speed of the system means a round about route (like through the bering straight, or the canada->greenland->iceland->uk route, or rio->monrovia) would be totally acceptable. island hop where possible. this is a good place to test out potential space elevator materials in a practical way.

[Kerbface]

Yes, shallow ocean, undeground, like the Chunnel or whatever it's called.

[Justy]

I love the idea of vactrains. And the idea of atomic powered tunnel boring machines burning sealed tubes of vitrified rock, how cool is that? The floating tunnel under the ocean makes a lot of sense, though if it sways at all, won't that be a problem for the ultra fast train rattling around on its track or, worse yet, the walls?

The version I'd read about started with a coast-to-coast backbone, LA-DFW-NYC, with branch lines of slower vactrains, conventional high speed trains in vactrain-like tunnels but without the vacuum, and local surface commuter trains. The eventual expansion of this Planetran train into a world-spanning (well, northern hemisphere spanning) transit system was of course inevitable, but hey, let's keep focused on immediate and practical things, like LA to NY in 54 minutes in a spaceship floating on magnets in a glass tunnel through solid rock dug by atomic moles. So cool! Hey, we should write that into a song about nostalgic views of the future or something.

On that train, all graphite and glitter,

Undersea by rail,

Ninety minutes from New York to Paris,

Well, by '76 we'll be A-OK...

What a wonderful world it will be,

What a glorious time to be free.

--Donald Fagen, "I.G.Y."

The coolest part was that the trains were unpowered. They were propelled by rolling downhill out of the station, and slowed again by rolling uphill into the next one. Vacuum tunnel and maglev, so no resistance, right?

One day I will read that paper ("Trans-Planetary Subway Systems, A Burgeoning Capability," Rand Corp, 1978). And I will see if it can answer my fiancee's biggest question. You see, the way I geek about rockets, aviation and trains, she geeks about weather systems, earthquakes and volcanoes. So when I described Planetran to her, her first reaction was, "But what about fault lines?" Instantly I started to imagine the westbound train from Dallas crossing into California at 3000mph where a segment of perfectly smooth glass tunnel had shifted six inches to the right.

There's also the fact that "nuclear" is a bad word now, and it might not be as economically viable using conventional tunnelling equipment to dig a path across the whole continent.

The undersea floating tunnel faces neither of those challenges though...

Edited July 19, 2013 by Justy

[Nuke]

1. who said this needed to be underground.

2. the tunnel will be made out of concrete and/or metal, not glass (glass is really expensive and quite fragile), dont say acrylic either that stuff is just as expensive.

3. there are ways to deal with fault lines. how do you think we cross them with roads, piplines, railroads, etc. engineers are good at what they do.

[brooksy125]

Wasn't their something like this that could be used for satellite launches?

If I remember correctly if the vacuum seal is broken it would cause a huge explosion...

[Justy]

The version I had read about used underground tunnels. They would be burned right through the rock using a tunnel boring machine, powered by a nuclear reactor, heating a large tungsten probe to melt and vitrify (glass) the rock. This was desirable because, once you built the machine, the cost of digging tunnel was tiny.

aside from land use concerns, an advantage to going underground was the low energy needed to operate the train itself. Gravity would do nearly all the work, both accelerating and braking. A ground level tube will have to use more power for that.