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Old 03-03-2006, 10:57 PM
jere7my jere7my is offline
Join Date: Mar 2006
Posts: 11
Originally Posted by zut
Like I said, it depends on the size and speed of the belt. There must be a boundary layer associated with the belt, and I would think that at some ridiculously high belt speed, the air over the wings would move fast enough to produce adequate lift. Granted, we're talking about awfully high speeds, but awfully high belt speeds are required to keep the plane in place.
Agreed, with a quibble. This gets into turbulence, which obviously requires a lot more information than we're given. A large enough belt, once it settles into a steady state, will indeed move the air along with it, but speed isn't really what you want. As the belt increases speed, the air will split into various laminar flow regions, with fast-moving ones near the belt and slow-moving ones near the outside world, until a certain threshold is crossed and all the layers dissolve into turbulence. If this belt were miles wide and circled the earth, you could probably create enough of a wind to launch a 747, if you increased the speed steadily; if it were about the size of the plane, you'd probably just create a lot of vortices. (That's just an off-the-cuff guess, though.)

Note, Paradoxic, that we're not subject to 1,000 mph winds here on the surface of the earth. This isn't because the atmosphere has rotational inertia; it's because the atmosphere is pulled along with the big spherical "conveyor belt" we call the earth.