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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?

Why is using a space elevator cheaper than rocket power?

Mark Adler
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Muze
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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.

(Source)

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...

Community
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  • 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. – SE - stop firing the good guys Sep 06 '18 at 12:16
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    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. – Steve Linton Sep 06 '18 at 13:35
  • I'm kind of thinking that NASA has probably thought about this. –  Sep 06 '18 at 13:37
  • 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. – Don Branson Sep 07 '18 at 18:18
  • What would the 50 km base tower be built out of and how exactly does it differ from the cable? – The_Sympathizer Sep 08 '18 at 03:14
  • Maybe most of the acceleration is in the first few hundreds of km, where the car is still in conduction range of the ground station, though I don't know whether we are talking about human-rated acceleration there. – Eth Sep 30 '18 at 16:55
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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.

Leech Phillip
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    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. – Don Branson Sep 07 '18 at 18:16
  • 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. – Leech Phillip Sep 07 '18 at 18:18
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    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. – Don Branson Sep 07 '18 at 18:21
  • Sounds more argumentative than reasonable. I'm done here. – Leech Phillip Sep 07 '18 at 18:22
  • He says "vehicle." I loosely referred to these as "cars," but if there's another term you prefer, that's fine with me. – Don Branson Sep 07 '18 at 18:23
  • Unless you're changing vehicles at some sort of dock about 20km up, high altitude helium/hydrogen bladders might help for the first 1/2000th of the ascent, but will be extra mass and extra parts to fail for the remainder. -- And I do mean you'll need bladders, rather than just filling spare room in your ascent vehicle with low density gas, because you'll need a couple thousand liters of hydrogen to lift a small payload an insignificant fraction of the way to the top of a space elevator. – Ghedipunk Sep 07 '18 at 23:16
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    53 compared to 45,000 is... somewhat less that 0.5%. If it were a probability, it would be somewhat less than scientifically significant. ;-) – Ghedipunk Sep 08 '18 at 04:33
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    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? – Ghedipunk Sep 08 '18 at 05:45
  • "you have to offset gravity with another method" I think that should be covered by the tension in the cable, pulling the lower sections up. – owjburnham Sep 10 '18 at 08:52
  • Don't be discouraged! Try more questions. – Muze Sep 12 '18 at 18:47