The Shanghai Maglev Train's max speed is 267 mph. Could a plane be made to follow a rail, surface area provided, if not an existing rail to travel along? How much faster could the heavily modified train/plane travel?

The plane is "on rail, not touching the track while following it, not over water but over a track made of concrete" or less.

Another way to ask, is how much would a very large cruise missile shaped vehicle benefit from using ground effect (possibly using curved surface area or rail to follow) verses not? Because the the rail is not directly supporting the wight of the vehicle, at least directly, how sturdy would that rail need to be? When done over water, the water is displaced by the air pressure under the ground effect plane.

• I would think that if you are going to rely on the infrastructure of a rail system you might as well get rid of the drag of the wings. 267 is plenty fast, if you want faster go in an airplane. I just don't see any advantages to the sort of hybrid you have loosely described. But go ahead, convince me! ;) Commented Aug 10, 2020 at 5:38
• When I first read the quesiton, I tought you wanted to revive the aerotrain, but then I realize you just want to make an hovercraft or a GEV. I fail to understand how different from an hovercraft your vehicle would be. Commented Aug 10, 2020 at 8:04
• So, you want to take a mode of transport that has the fundamental property that it stays on the ground and combine it with another mode of transport whose fundamental property is that is does not stay on the ground. I think we can see why this idea hasn't made progress before. Commented Aug 10, 2020 at 10:42
• The Maglev does not, in fact, stay on the ground. It levitates because of magnetism. Also, planes do not really go any faster than the Maglev while they are close to the ground, both for reasons of avoiding noise and because the high air pressure compared to FL400 does put more stress on the airframe. So, uh, your idea basically has been done, at least as close as is reasonable. (Also note that altitude equals safety in aviation, being close to the ground gives you less room for maneuvering and an engine failure or similar has much more impact than at higher altitudes.)
– user50571
Commented Aug 10, 2020 at 13:14
• If the vehicle must follow tracks, then it is a train, regardless of whether it is in contact with the track or hovering a few inches above it. Planes, even ones that can only fly in ground effect, do not have tracks. Commented Aug 10, 2020 at 16:23

The first issue with airplanes is they are stupendously, freakishly light. Any random American freight diesel locomotive weighs more than a 747-400. Trains rely on this mass to provide the downforce to keep them engaged to the railhead.

So your vehicle would need to do something to replace this downforce; for instance have a tubular or I-beam rail which allows the train to grab the bottom of the rail; expect switches and special work to be complicated at that point, shifting an entire track instead of just small parts of it.

So while unloading weight off the rail only makes matters worse for track design, you're also paying for that lift with induced drag. In other words you're using a great deal more fuel (or electricity) to unload weight off the rail, when the rail really doesn't mind bearing weight.

In fact from an aviation perspective, the "induced drag" on a train can be approximated to zero, thanks to Mr. Babbitt (Mr. Timken's idea is worse for drag but better for reliability).

That's why good ole fashioned railroad just keeps winning the high-speed race (or coming too close to matter). The exact TGV train that ran 357 mph could be dropped onto a NYC subway branch in Brooklyn, interchange onto LIRR, come into Penn Station and the Amtrak Corridor, through the freight rail system to Detroit and run on Woodward Avenue Q-line, then to Long Beach CA and run on the Blue Line. The only thing I'm arm-waving is power supply, and curve and platform clearances on NYCTA. In fact, in 1993 Amtrak dragged an X2000 and ICE high-speed trainset all over America behind diesels. No wheel modification needed.

So while your idea has merit... once you get out the sharp pencil and really start optimizing for performance, you will find it best to forget wings and load full weight on the rail, and further, to optimize for Plain Old Railroad Track so you can just use existing rails to get downtown. Going with a wack-a-doodle guideway doesn't buy you much, and makes getting downtown a mega-project of biblical proportion all its own. Here:

The city of Victorville was selected as the location for the westernmost terminal since extending the train line farther into the Los Angeles basin through the Cajon Pass would be prohibitively expensive.

/facepalm... Cajon Pass is not a challenging hill for HSR. If they can't even handle that, they sure aren't getting into L.A. proper where all the connecting trains are. And L.A. is a piece of cake compared to a dense, old city like Paris or even Boston. This: This is the folly of a wack-a-doodle guideway. They finally retreated from that to a standard railroad design, so they could come downtown on shared rails.

• I am not worried about max efficiency as far as the vehicle, so much as max efficiency for the speed of it; to have a plane to travel like a train to achieve higher speeds verses normal cargo or passenger flight or train ride. Less efficient than a train, but more efficient than normal cargo flight. Commented Aug 10, 2020 at 19:19
• If I could make my question read like your answer. Great work! Commented Aug 10, 2020 at 20:28
• To elaborate on your last point, if you have a vehicle with wings following the railway, you need a much wider right of way. You also need to rebuild all multiple track sections of your railroad to provide sufficient clearance for vehicles going in opposite directions, and you have to worry about intruding cows, deer, humans, &c being struck by the wings. As pointed out, a diesel locomotive is a LOT sturdier than an airplane wing. Commented Aug 11, 2020 at 5:20
• The Amtrak ICE did, in fact, have its wheels replaced because American rail profiles differ from German ones.
– user50571
Commented Aug 11, 2020 at 13:39