There are many types of propulsion from electric turbine engines to steam powered catapults once used on aircraft carriers. Which of the many types of propulsion would be the most efficient in getting a vehicle to space via space elevator?
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2 Answers
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Clicking a few links through your linked question provides the answer here.
David Smitherman of NASA/Marshall's Advanced Projects Office has compiled plans for such an elevator that could turn science fiction into reality. His publication, Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium, is based on findings from a space infrastructure conference held at the Marshall Space Flight Center last year. The workshop included scientists and engineers from government and industry representing various fields such as structures, space tethers, materials, and Earth/space environments.
Current plans call for a base tower approximately 50 km tall -- the cable would be tethered to the top. To keep the cable structure from tumbling to Earth, it would be attached to a large counterbalance mass beyond geostationary orbit, perhaps an asteroid moved into place for that purpose.
Four to six "elevator tracks" would extend up the sides of the tower and cable structure going to platforms at different levels. These tracks would allow electromagnetic vehicles to travel at speeds reaching thousands of kilometers-per-hour.
So, the answer is "Electricity". Theoretically, you'd have a solar panel farm attached to the base of the elevator providing at least the majority of the power. Since the elevator would be at the equator, there's bound to be plenty of sunlight...
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$\begingroup$ If you can provide power from the base, I can't see any reason why you would not just hook it up to the grid and produce the electricity in any way you want. $\endgroup$ Commented Sep 6, 2018 at 12:16
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1$\begingroup$ The cable is very long. Transmitting power along the length of it (in either direction) needs massive conductors and leads to considerable losses. Designs I have seen for early elevators use a crawler gripping the cable with rollers and powered by a laser beam from somewhere. $\endgroup$ Commented Sep 6, 2018 at 13:35
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$\begingroup$ I'm kind of thinking that NASA has probably thought about this. $\endgroup$– user21233Commented Sep 6, 2018 at 13:37
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$\begingroup$ Perhaps by the time we have cables strong enough to build a beanstalk, we'll also have room-temperature superconducting cables that can deliver power without loss to crawling cars. $\endgroup$ Commented Sep 7, 2018 at 18:18
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$\begingroup$ What would the 50 km base tower be built out of and how exactly does it differ from the cable? $\endgroup$ Commented Sep 8, 2018 at 3:14
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Helium. Gravity is the biggest issue. You can't accelerate all segments to geostationary velocity, therefore, you have to offset gravity with another method. The use of He within various parts of the structure - especially lower portions of the shaft - would add to the overall vector compensating for gravity.
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1$\begingroup$ What do you mean by "all segments"? It seems like the questions is asking about moving the cars. Anyway, helium would be useful for the first few dozen kilometers, but there's another 45,000 kilometers above that, where helium is just dead weight. $\endgroup$ Commented Sep 7, 2018 at 18:16
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$\begingroup$ Sorry you feel that way - educate. He didn't say cars, and I specifically said "lower portions." Compressed air would be most practical for propelling the cars, also providing air exchange for the entire elevator. $\endgroup$ Commented Sep 7, 2018 at 18:18
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1$\begingroup$ I believe this is more about reason than feelings. What part of my comment is problematic in your view? That helium won't help over a few dozen kilometers? Or that a beanstalk will be that high? I'm not understanding your question. $\endgroup$ Commented Sep 7, 2018 at 18:21
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1$\begingroup$ 53 compared to 45,000 is... somewhat less that 0.5%. If it were a probability, it would be somewhat less than scientifically significant. ;-) $\endgroup$ Commented Sep 8, 2018 at 4:33
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1$\begingroup$ I mean really, if you had to walk 100 miles, and you had something that would make the first 500 feet easier, but make the remaining 99.9 miles harder, would you carry it? $\endgroup$ Commented Sep 8, 2018 at 5:45