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Space elevator: up and down cars

Power the space elevator up-cars by regenerative braking of down-cars
  [vote for,

Power the space elevator by having at least two tracks, preferably many tracks for redundancy, with up-cars powered by regenerative braking of down-cars. This requires more weight going down than going up, which should be no trouble once we start mining the moon and asteroids. Cars could cycle up then down then up etc.

Cars need to be slow in the atmosphere, but outside the atmosphere the faster they go the less weight they add to the elevator and the less food passengers need to bring along, so faster is better. Escape velocity and beyond would be great if you can do it. Cars should use electromagnetic propulsion, like a railgun, rather than actually touching the elevator. Cars would be very sensitive to fast oscillations.

The space elevator needs to damp fast oscillations. Have the elevator be a rigid cylindrical shell, like bamboo, tens of meters across, with fins sticking out as tracks, and with a heavier cable running down the middle. Each part of it needs to be super-strong self-supporting space elevator stuff, but the central cable can have fast oscillations while the outer shell and tracks have to stay steady for the cars. Fast oscillations in the outer shell and tracks can be dumped into the central cable by pushing and pulling. The outer shell can have oscillations too, but only low enough frequency ones that the cars experience them as gradual movements rather than jolts.

rjenkins, Jul 04 2019

The man said ... https://xkcd.com/536/
[normzone, Jul 06 2019]


       Having two tracks means more mass, more mass for the structure means more strength. I don't know the numbers but I am guessing it will be quite a few hundred years before having materials of this nature. All current investment is with materials we believe are achievable of this goal.   

       Although, bio-mimicry of bamboo, for carbon nanotube structure, might be an inkling of a valid idea.
wjt, Jul 06 2019

       Carbon nanotubes, or boron nitride nanotubes etc, are cylinders at the nanoscale, but this would be a cylinder tens of meters across. Each track fin would stick out a few meters. I imagine the components of the fins and cylinder and central cable would be rebar-like solid rods of carbon nanotubes, about 1mm*1mm*100m, tapered at the ends, where the end of one rod is lashed to the next rod for several meters. That's manufactureable and replaceable. The cable would be mostly solid while the cylinder and fins would very sparse, sort of like a net.
rjenkins, Jul 06 2019

       I can see the concepts and thought engineering but even though everyone is awkwardly smirking, the physical actuality of this build is probably a lot more than fifty years off. Fifty, for a one cable, one climber initial step prototype, unless there's a unforeseen massive breakthrough in material science just ready rock science's world.
wjt, Jul 07 2019

       A fountain-based elevator inherently has this regenerative braking property, as I understand it, without needing multiple tracks, or even multiple cars traveling simultaneously.   

       // Cars should use electromagnetic propulsion, like a railgun, rather than actually touching the elevator. //   

       Sliding contact is generally necessary in railguns. Perhaps you mean a coilgun, or a brushless linear motor?
notexactly, Jul 21 2019


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