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Recently posted on this site was in adea for a "lite" space elevator, with a minimal superstructure buoyed up by balloons. Balloons cannot provide lift in very thin atmosphere, and so the area of the space elevator extending very high still needs a means of support.
I propose that the top of the
elevator be held in place by a solar powered perpetual rocket running on compressed air. Large solar panels capture the solar energy which is abundant at high altitude. This is used to run a pump which draws air up a tube running the length of the space elevator. At the top, this air is accellerated with great force into one or more rocket nozzles pointing down and away from the elevator. These nozzles could also be used to steer the top of the elevator to meet spacecraft etc as well as resist high winds lower down.
The problem with propulsion in space is that energy is available, but there is nothing to throw in the opposite direction. This approach makes use of the connection to earth to get something to throw.
Buoyant Space Elevator
http://www.halfbake..._20space_20elevator
A nifty idea. [bungston, Oct 05 2004, last modified Oct 17 2004]
Space Elevator
http://science.hows.../space-elevator.htm
From howstuffworks.com [st3f, Oct 05 2004, last modified Oct 17 2004]
[link]
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How could any amount of pumping draw the air up the tube, when there is already vacuum all around failing to draw up the rest of the atmosphere? Fundamental flaw, methinks. |
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(Now, it might work if you had pumps creating a high pressure in the tube at ground level. Someone else can do the math - there's always someone with a calculator.) |
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I suppose this is a space elevator, and the whole point is to move things up from the ground. However the question of whether the topside pump would work is interesting. I am not sure it would. |
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DrCurry is right, it will work only if the pump is on the ground. Also, why not put the solar power on the ground so the rocket has less to (perpetually) lift? the power loss through the atmosphere is small, and the arrays would be much cheaper. Also, the air could be heated electrically to give a better specific impulse to the rockets. |
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BUT what about the environmental impact? are we sure that this won't cause a lot of air to be lost to space? |
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Maybe you guys haven't read 'The Fountains of Paradise' by Arthur Clarke. The dynamics of the space elevator is clearly explained. It's afixed structure with a station at geostationary orbit and a counter weight past that. And yes, the problem is that it requires materials several orders of magnitude stronger than any we have under development. |
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That's what I like about Clarke: he only breaks ONE law of physics at a time. |
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The solar power station is weightless, in orbit. It is attached to the elevator by a tiny wafer thin wire. I put it up there because the suns rays pack more punch and you dont have to worry about dust, clouds etc. |
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Re: Mr Clarke. There's more than one way to skin a cat. |
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I'm afraid [DrCurry] is right. Suction works by creating a presure differential that is greater than the gravitational pull. The difference between a partial vacuum and more of a vacuum is unlikely to spirit up much air from ground level. |
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The geostationary orbit should be almost good enough to hold it in place. As for trimming, why not consider a different propellant medium, such as using an ion drive. The propellant could be shot up the lift and the energy stored at the top used to accelerate it. |
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//are we sure that this won't cause a lot of air to be lost to space?// |
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It's estimated that our atmosphere looses billions of cubic feet of air at the polar regions. Be we also recieve tons upon tons of raw material from space each day, like fragments from asteroids whos chemical composition includes oxygen. Or ice from comets which also includes oxygen. The earth is not a closed system. We don't have to worry about sucking the air off our planet any time within the next eon. |
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(What RusNash said) Build it according to the Arthur C Clarke's instructions and the whole thing's under tension anyway. I can't see the need for these downward pointing nozzles. |
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But then they'd point out to the sides, surely? |
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// There's more than one way to skin a cat. // |
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I know a dozen or so, but I'm always willing to learn ...... |
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The nozzles would point wherever you wanted. I envisioned mostly down, to keep the rest of the elevator from being pulled back to earth. But they could be adjusted to point sideways - which would be useful for bringing the top of the elevator to bear on the space station etc. |
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(+) Of course the real joke is the elevator itself. But this add-on idea is a good one. You want to use water, of course, not air -- no momentum with air. And you don’t want to use solar power -- there’s no way to support all those solar cells at the top -- it won’t be weightless, you know. So you install a nuclear plant at the bottom, and a string of pumps along the elevator to pump the stuff up. The weight of the pipe and pumps and electrical cable will be enormous, of course, much greater than what you’d get from ejecting the water...so eventually you’ll have to resort to vacuum balloons, disguising them as pumps... |
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//it won't be weightless, you know//
Er... it will at the orbital anchor. That's really the point of a space elevator. (link to howstuffworks). |
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