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So there is a similar question, I read it but I am thinking a little differently. So instead of a big tower going into orbit with cables like an elevator, what if we had a satellite in orbit, something that can move to various orbits and positions. This satellite has a long cable it drops to the earth to pre-determined "Bear Traps" like we do to help land helicopters onto Frigates in rough seas. Once the cable is secured payloads are loaded, the bear trap released, and the whole thing reeled in to the orbiting satellite. From there it is loaded onto docked spaceships to be sent to the moon or where ever. Is that more practical/realistic than a big tower going from the ground up? You know considering the materials are available to withstand the stresses. Would this setup require stronger materials than the earth up tower/elevator?

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    $\begingroup$ How's it going to drop this cable, when it's in free-fall? $\endgroup$ – Organic Marble Feb 19 '18 at 23:35
  • $\begingroup$ Look up rotovator. en.wikipedia.org/wiki/Momentum_exchange_tether $\endgroup$ – geoffc Feb 19 '18 at 23:40
  • $\begingroup$ Well an orbit is an endless "free fall" so assuming we both understand that the satellite is not falling to the earth but falling around it the cable would do so as well once released. So to get it started it would likely have to be "shot" out towards the earth to a point where gravity will pull it down, or the end of the cable would need some sort of thrust guidance system to guide it out of its orbit and towards the earth. I would also imagine that the orbiting satellite would have correctional thrusters to stabilize it's orbit against the forces of pulling up extra mass from the surface. $\endgroup$ – Tyler Veinot Feb 19 '18 at 23:43
  • $\begingroup$ the same force the satellite exerts on the payload via cable, the payload exerts on the satellite, pulling it down. $\endgroup$ – SF. Feb 19 '18 at 23:43
  • $\begingroup$ Rotovator is exactly what I was looking for thank you! $\endgroup$ – Tyler Veinot Feb 19 '18 at 23:54
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The comment by @geoffic suggested looking up a rotovator, which is listed in Wikipedia as a momentum exchange tether.

It turns out that this is just the thing that I was envisioning. It seems that in the last half century (or probably longer) a wide variety of schemes for getting to space have been explored in the spaceflight engineering (as well as SciFi) community.

From the (extensive) Wikipedia article:

A momentum exchange tether is a kind of space tether that could theorically be used as a launch system, or to change spacecraft orbits. Momentum exchange tethers create a controlled force on the end-masses of the system due to the pseudo-force known as centrifugal force.

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  • $\begingroup$ you can't secure the end of a rotovator while loading it, and generally involve a high speed/altitude plane attaching the payload to the tether. So not much like the question really. $\endgroup$ – user20636 Feb 20 '18 at 8:34

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