My understanding of the idea of a space tether is that currently you wouldn't be able to build one because even just having it support it's own weight we don't have strong enough material, and with the material we do have the thickness you would need for the cable makes it impractical.

But I am wondering if there have been any designs for a space tether that have tried to break the problem down into smaller stages or parts to try and over come some of these problems.

For example if you use a high point like a mountain to start from. If you then built a tall building. If you then tethered balloons to get up higher. If you then tethered electric multi-rotor drones and powered them with power coming up the tether. Maybe there are other stages you could have that I haven't thought of and maybe things like a tall building as a starting point don't make much of a difference. I am just wondering if anyone has ever done the math on doing a space-tether in multiple stages?

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    $\begingroup$ Check Skyhook or other similar concepts under the see also section. Multi-stage you describe wouldn't do much good because getting into orbit isn't so much about gaining altitude as it is about gaining speed, and a whole lot of it. Even if you could reach out till the ISS (which is a W=PT problem at 1 to ~0.88 g), it would hit your cable at over 7.5 km/s! Also see Effect of atmospheric drag on rocket launches and benefits of high altitude launch sites $\endgroup$ – TildalWave Aug 15 '15 at 0:08
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    $\begingroup$ @user802599 All the tricks you mention wouldn't shorten the tether by as much as 1%. The trouble with a skyhook is that the tether isn't in orbit and each point along it has to be able to support the weight of all the tether below it. $\endgroup$ – Organic Marble Aug 15 '15 at 0:24
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    $\begingroup$ @OrganicMarble And 1% is way too much. AFAIK a "space tether" needs to have its center of mass in geosynchronous orbit which is at 36,000 km altitude. 1% of that is where the space station orbits. If you can start at 1%, you don't need any tether. $\endgroup$ – LocalFluff Aug 15 '15 at 6:14
  • $\begingroup$ I did find some similar information under Airship To Orbit. space.stackexchange.com/questions/6548/… in that they consider using solar powered ion propulsion to keep an airship up higher. Maybe you could do the same for a tether and send power from the ground and not need the solar panel weight. in the end I think the numbers would fall short, but I would be interested in see in how close to space to could get with something like this. $\endgroup$ – user802599 Aug 16 '15 at 12:33

Hop David proposed something like this idea a few years ago: http://hopsblog-hop.blogspot.com/2016/08/tran-cislunar-railroad.html. This particular idea has three tethers, one above Low Earth Orbit, one below Medium Earth Orbit and the third above Geosynchronous Equatorial Orbit. However, the motivation behind this seems to be to avoid orbital debris, rather than for reasons of material strength.

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(Image is taken from the linked blog post.)


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