Environment & Energy
Related: About this forumVacuum trains: a high-speed pipe dream? (BBC Future)
Jon Stewart
Transatlantic passengers on Concorde often referred to the supersonic plane as their time machine for its ability to land in New York two hours before it left London.
But that kind of illusion could look like childs play if so-called vacuum trains ever take off.
These futuristic transporters, designed to hurtle through tunnels that have had all of the air sucked out of them, could theoretically hit speeds of up to 4,000 km/h (2,500 mph), cutting the commute from Europe to North America to just one hour. In this high-speed future, passengers would arrive a full four hours before they set off.
As with all far out technology, it sounds like science fiction. And, in fact, vacuum trains do feature in movies like Star Trek and Logans Run. Whilst in the dystopian future of Farenheit 451, Ray Bradbury describes a silent air-propelled train that slid soundlessly down its lubricated flue in the earth.
But these are far from fiction, as we found out when Future reader Seb Gibbs suggested we look into them here at Hyperdrive. Today, there are teams in the US, China and elsewhere working on the concept, with some predicting their arrival within 10 years. Whilst others believe that they could offer a potentially cheap route to launch rockets into space.
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more: http://www.bbc.com/future/story/20120601-high-speed-pipedreams/1
MADem
(135,425 posts)That's pretty doggone fast!
Fascinating concept!!!
Mixed with magnets, I guess they will go fast:
johnd83
(593 posts)There have been concepts about putting these trains under the ocean too. I worry that if there is an accident it would be catastrophic, and probably destroy the entire rail line.
OnlinePoker
(5,730 posts)mindwalker_i
(4,407 posts)Take a nice deep hit from that bong, and out with it. Train disintegrates.
ThoughtCriminal
(14,058 posts)Crosstown commutes are a series of tubes...
madokie
(51,076 posts)or at many manufacturing facilities where they have to get samples to the lab for analysis quickly before they use the product that makes the parts that they are about to make. I know Iron foundries use them for that reason as do some plastic manufacturers.
I've worked on these systems at the foundry where i worked for several years back during the raygun years and there really isn't much to go wrong other than something bending the tube or the vacuum quits working. Other than that they're pretty fail safe and quick as all get outs. At the foundry they'd have samples back at the lab a couple hundred feet away for analysis way faster than they could by any other means, like right fucking now.
caraher
(6,279 posts)It always seemed too obvious not to have been thought of by someone else...
One thing I wonder is how much energy goes into maintaining the vacuum vs. the energy saved by virtually eliminating air resistance.
XemaSab
(60,212 posts)It's not just maintaining the vacuum, but it's starting and stopping the vacuum at each station.
FBaggins
(26,799 posts)Especially compared to the engineering challenges of tunneling through the N.A./Eurasian plate boundary (and for thousands of miles).
An airlock would be comparatively simple to set up. Since the (pressurized) train itself would fill up the bulk of the lock, there wouldn't be all that much air to evacuate/fill each time. Probably easier than the Panama locks.
XemaSab
(60,212 posts)Without a sea-change in the US, passenger rail will be nothing but a small-time novelty in many areas.
FBaggins
(26,799 posts)It really doesn't have much to do with passenger rail in the US. That might not pick up at all.
But such a transatlantic option (very high speed combined with very low cost) would be a game-changer.
Heywood J
(2,515 posts)For how much of the trip, at what kind of G-forces for the passengers on starting and stopping, and at what kind of pressure change in the cabin? There are reasons that elevators don't make it to the top of skyscrapers in seconds, even though there are ways to make that happen. Plus there's that whole Mid-Atlantic Ridge and laying tube over an expanding magma field.
A slower version on land might be plausible, but I don't think many people would like to experience astronaut-on-takeoff, or life as chunky salsa, to see Europe or space.
caraher
(6,279 posts)4000 km/hr is around 1100 m/s - let's round down to 1000 m/s and take g=10 m/s^2. Then at 1 g it takes 100 seconds - less than 2 minutes - to reach such a speed. I'm not sure what the best choice for a propulsion system would be in that case - you're then talking about accelerating over a distance of tens of km.
I think reaching modern jetliner speeds would be a more reasonable and still-useful goal.
Cabin pressure changes don't have to be an issue at all - I presume you would seal the compartments at whatever pressure you like; making it 1 atmosphere is just a matter of building a sturdy enough compartment.
Laying the tubes could be a real showstopper, though. Magma isn't going to be a congenial environment for this!
Heywood J
(2,515 posts)All those people in a confined space have to have some way of obtaining fresh oxygen and removing carbon dioxide. Even if you have stored oxygen in tanks, the CO2 builds up and poisons everyone. That's why jets pressurize the cabin constantly and vent the used air, which means an inevitable pressure change for the passengers. Not to mention someone's BO or the air around the required toilet...
1G in a car is more than enough to throw you back into the seat. That's about 0-60 in 2.7 seconds. More comfortable speeds for unbelted passengers or those not wanting a thrill-ride experience would be something like 0.1 g, which means your train takes 20 minutes to get up to speed, and 20 minutes to slow down. That one-hour travel time isn't so realistic now.
caraher
(6,279 posts)You just need more sophisticated air handling than airliners use. We keep people in space for months on end; air quality is a minor technical issue. Depending on the use of the tunnel and pumping speed one could even imagine venting gases out the rear if there were a need to do so.
Concerning acceleration, why assume unbelted passengers? On an airliner you are belted for substantial periods of time that do not exceed those required for accelerating and decelerating one of these trains. Airliners might be a good benchmark for realistic readily-tolerated accelerations - they're well short of 1 g, but I'd say closer to 1/4 than 1/10 of a g.
I'm not obsessed with the hypervelocity claims and 1-hour travel times; I do think there could be substantial benefits to this approach for shorter trips and slower speeds.
pscot
(21,024 posts)would pass from the North American tectonic plate to the Eurasian tectonic plate. Hard to imagine what could go wrong there.
XemaSab
(60,212 posts)Something goes wrong on a plane and you could always hope to glide to Iceland or wherever. If it goes really wrong, you could hope to die quickly.
On a train you might be sitting there for a long, long, long time.
pscot
(21,024 posts)in fragments, through the mouth of a volcano