h a l f b a k e r yAlas, poor spelling!
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Trains are long skinny worms and have a small frontal area/volume ratio. Because of this, they're pretty efficient in the fluid dynamics department.
So why not build submarine trains? Not in a tunnel, but directly in the water. Surely the resistance through water wouldn't be too bad either. If trains
on land can ride at 190 mph, they must be able to travel at 60, 80 mph or even more underwater?
Advantage:
We can have transatlantic and transpacific railroads that use a fraction of the vast amounts of fuel that airplanes use.
Implementation:
Tracks could oviously not be "chemin de fer". Iron, or steel would rust quickly. Perhaps ultra high density polyethylene would be suitable. Propulsion can't be overhead electric or diesel. It could be nuclear, but that's a little risky. I think ideal would be a large battery bank in the front of the train together with electric propulsion. The train can maintain a constant speed over its entire trajectory, so unlike with airplanes the extra weight of batteries is of little consequence. It might even be beneficial in holding the train down.
These trains could be outfitted with all the abundant luxury of great trains like the Orient Express. Surely people would like this.
In shallower waters, passing aquatic life can be observed.
Cable Ferry
http://en.wikipedia.org/wiki/Chain_ferry
[DrCurry, Oct 07 2006]
cavitation blog
http://www.defencet...dex.php/t-3701.html
[williamsmatt, Oct 06 2008]
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Annotation:
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Unfortunately, your plastic trains would float off the tracks and become boats. |
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Silly! The trains run UNDER the tracks. |
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Hmm, an electric train, now the fastest submarine in the world... |
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Hey, I wanted to make the tracks of plastic, not the trains! The trains are made of cast ir..fiberglass. |
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And ultra high molecular weight polyethylene is only slightly lighter then water. Surely it won't float up when solidly bolted to railroad ties made from recycled rubber. |
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Perhaps it's possible to shape the cross-section of the train in such a way that it's pushed onto the rails by a side current, some sort of wing shape. |
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So you don't use rails, you use a cable or chain that the submarine train hauls itself along, the way some ferries do. Then it doesn't matter if currents push the train sideways - the cable goes with it. |
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3600 miles / 60 miles n hour = 60 hours underwater - any thought to food fresh water or AIR ? back to the drawing board, i think. |
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Air? There's no air, that would make it too buoyant. Unless you use Caeli's suggestion and run the train under the rails. The rails could be fastened to the bottom of giant pontoons and stretched across the surface of the Atlantic. Then the buoyant train cars could run upside down underwater, but not so far that you couldn't run a snorkel to get air. As for water, there's a bar on board, of course, where you can water down your Scotch. |
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No. Buoyancy is not an issue. Our train can be made arbitrarily heavy to weight it down. It doesn't need zippy acceleration: it's speed is constant for most of the trip. Also we have room to bring a large volume of liquified air. Fresh water either be brought or made with a water maker. |
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I like the steampunk aspect. Bun. |
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I like the idea of a transatlantic train, but I have a few issues: |
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Buoyancy aside, I'm worried about the energy required and the speeds that are possible. |
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Water is around 1000 times denser than air, but drag is proportional to speed squared, so to travel at 60mph underwater, you'd need approximately: |
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1000 * 80^2/125^2 = approximately 410 times the power an intercity 125 at full chat! Multiply by 3600 miles, that's a helluva lot of batteries, and probably worse than the planes from a 'green' point of view! |
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Transatlantic 'channel tunnel' or a floating railway based on 'oil rig' anchoring more doable. |
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//Water is around 1000 times denser than air, but drag is proportional to speed squared//
sp. "800", "cubed" |
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Well there's no problem with air and no problem with submarine travel, the problem is at the surface, but air vehicles tend to fall out of the sky and submarine passengers tend to asphyxiate, so.... |
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Flying-Fish Transatlantic Service: same thing but completely different: no tracks, just a train that leaps out of the water and dives back in again. Good for that "Mechanical Loch Ness Monster" effect. |
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sounds strangely doable. the additional resistance of water does not greatly slow down boats, or come to think of it submarines. is it really true to say that because water is denser it has an equal increase in friction? trains don't even try to have aerodynamic fronts because their mass (and hence inertia) is so great any air friction is nominal. the main problem is overcoming its own inertia, once they get to speed they require little energy to keep them going. i think this mass would reduce the relative friction effect of water.
the greater problem would certainly be laying the track. i am presuming it would be laid on the sea bed otherwise any support structure would make it prohibitively expensive ov er air travel. Oil drilling platforms sometimes use pipelines to get the oil back to land at a constant flow for storage. i have met a diver who works at assembling these lines and apparently it is a virtually impossible and very dangerous task to construct these.
as an adjunct to your idea perhaps the 'trains' could travel on cables slung within the sea, with the train driver able to control the bouyancy much like a scuba diver, and use fins or aelerons to control the relative elevation and direction of the 'train' whilst underwater. the train could then attach to rigid track once the water was not deep enough to absorb any error in the positioning of the train. |
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//with the train driver able to control the bouyancy much like a scuba diver//
By varying his average lung volume?? |
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//with the train driver able to control the bouyancy [of the train] much like a scuba diver// |
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Oh, my dear! You forgot to take into account the water displaced! Haven't you known that speeding bullets simply disintegrate upon hitting water? So, why not just gulp the frontal water in and jet it out in the rear? Once done, all that's left is to make enough living space between the inner and outer shells of an open-ended hollow cylindrical underwater transatlantic train we envisioned... |
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[rotary], top speed submarine travel is estimated at around 45 - 50 knots/hr or 90klm/h. interestingly a tuna travels at around 45knots. bullets travel around 3000klm/h. thats a pretty big difference - what speed are you thinking this thing would travel at? |
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How about a rope drive system where the sea-train connects on, with a parrellel rope 50 miles north or south to provide a backup line incase the rope snaps. The rope would flex for collision avoidance, to avoid hitting a whale for example. The train would have multiple and redundant collison avoidance systems as well. If the sea-train goes faster than 60 MPH, have unmanned scout cars ahead of the train because the ocean is unpredictable. There could be bouy-like supports to hold the line near the ocean surface. Having rope lines for thousands of miles in the ocean is cheap and low-tech infrastructure. |
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If we want a fast trans-ocean transport alternative to planes we should develop speed ships, capable of 200+ MPH. |
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I think we should just build Elon Musks Hyperloop or ET3 already. |
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