Talk:Transatlantic tunnel: Difference between revisions

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For an April 2005 deletion debate over this page see Wikipedia:Votes for deletion/Transatlantic tunnel

This article was nominated for deletion on September 8, 2007. The result of the discussion was keep.

This should be merged with Vactrain.

No, but it should link to it. --Golbez 07:22, 24 August 2006 (UTC)[reply]

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Stability of a submerged tube?

A text I read regarding ordinary high-speed trains said that the high-speed railways need very high stability because there can't be "bumps" at a high speed. Therefore a suspension bridge is not usable at high speed. If one is neccesary it must be travelled at lower speed. What about travelling submerged tubes at above 1000 mph? Maybe one trains causes the tube to move, which might make it very unpleasant for the next train? --BIL (talk) 20:58, 20 May 2008 (UTC)[reply]

Indeed, such a tunnel or tube is so far beyond current fiscal and engineering capabilities that problems like that seem downright mundane. Presumably such a tube would have integrated mechanisms for active stability, and trains designed specifically to deal with rail movement, rolling of the tunnel due to its weight, change in buoyancy, etc. Or perhaps solving those are so difficult, a magnetically levitated (MagLev) might be justified. —EncMstr (talk) 22:30, 20 May 2008 (UTC)[reply]

Maglev does not solve the problem since the railway is still influenced by a force from the train (Newtons third law). Maglev needs centimeter accuracy for the "railway", and would get serious problems with a submerged tube. If air travel still exists, e.g. year 2200, why is a maglev across the Atlantic justified, having the cost in mind? Isn't air travel better? --BIL (talk) 20:45, 22 July 2008 (UTC)[reply]

As long as the effect is behind the train, who cares? Presumably the next train is an hour or more behind, long enough for the system to stabilize.

I thought the whole point of a high speed (1000+ mph) tube was for it to be in a near-vacuum for energy use advantages.

I remember another flavor of proposal (don't remember where, but it was 15–25 years ago) which would mostly evacuate the tube with the train sealing the cross section. With the train at one end, it compresses the air between the station and the train. As soon as the brakes let go, the air pressure would accelerate the train toward the far end, initially in near-vacuum. As the train approached the other end, the bits of air ahead of it would compress and slow the train to a stop just as it reached the station, with a nearly full vacuum behind where it just came from—almost a perpetual motion machine. Just needs a little energy added to replace the thermal losses magnified by Boyle's law. —EncMstr (talk) 21:00, 22 July 2008 (UTC)[reply]

The whole point of having the train in a near vacuum is three-fold. First you want to save the energy that would be wasted pushing all that air. Second you can go faster in a vacuum than in normal atmosphere due to reduced friction. Finally, if one were to push all that air column at high speed you would get huge vibrations before the train and a fairly large wake behind it. By removing most of the air we considerably reduce the difficulty of the problem, but introduce a new problem: if the tube were deep underwater the pressure coupled with the suction from the near-vacuum would be tremendous. This is why a tube floating somewhere in the water column is more viable: less pressure and less possibility of rupture due to earthquake. Earthquakes are also an important factor since, over the are which the tube would span, one would assume they would happen fairly frequently. All in all the partial vacuum floating tube is the most promising design, yet still a good way away. Ahugenerd (talk) 18:44, 6 August 2008 (UTC)[reply]

@@ Line 25: / Line 25: @@
 :::I thought the whole point of a high speed (1000+ mph) tube was for it to be in a near-vacuum for energy use advantages.
 ::: I remember another flavor of proposal (don't remember where, but it was 15–25 years ago) which would mostly evacuate the tube with the train sealing the cross section.  With the train at one end, it compresses the air between the station and the train.  As soon as the brakes let go, the air pressure would accelerate the train toward the far end, initially in near-vacuum.  As the train approached the other end, the bits of air ahead of it would compress and slow the train to a stop just as it reached the station, with a nearly full vacuum behind where it just came from—almost a [[perpetual motion machine]].  Just needs a little energy added to replace the thermal losses magnified by [[Boyle's law]].  —[[user:EncMstr|EncMstr]] ([[user talk:EncMstr|talk]]) 21:00, 22 July 2008 (UTC)
+:::: The whole point of having the train in a near vacuum is three-fold. First you want to save the energy that would be wasted pushing all that air. Second you can go faster in a vacuum than in normal atmosphere due to reduced friction. Finally, if one were to push all that air column at high speed you would get huge vibrations before the train and a fairly large wake behind it. By removing most of the air we considerably reduce the difficulty of the problem, but introduce a new problem: if the tube were deep underwater the pressure coupled with the suction from the near-vacuum would be tremendous. This is why a tube floating somewhere in the water column is more viable: less pressure and less possibility of rupture due to earthquake. Earthquakes are also an important factor since, over the are which the tube would span, one would assume they would happen fairly frequently. All in all the partial vacuum floating tube is the most promising design, yet still a good way away. [[User:Ahugenerd|Ahugenerd]] ([[User talk:Ahugenerd|talk]]) 18:44, 6 August 2008 (UTC)