Assuming all the primary hurdles in building a space elevator are overcome, would it be structurally feasible to attach intermediate stops along the length of the tether (between the planet and GSO, and/or between GSO and the counter weight) without causing instabilities?
Thank you!
As part of the premise, we now have a space elevator, a rope of material you can climb. You can climb up it and suddenly be in Geo-Stationary Orbit (GSO). Not only is that a long ways away, but launching rockets just became super cheap. So could there be stops along the elevator - a "floor" to stop at?
The biggest consideration is:
The premise is that we have something that solves the tensile strength issue for space elevators, but how well we overcame this determines the margins for floors' weight. Those floors are supported on the elevator by the main cable. If the cable breaks, not only does the elevator go away, but so do those floors!
Additionally, those extra floors contribute to another thing:
I know that space is characterized by its profound lack of stuff. Around earth, where at least some part of a space elevator must operate, things get really busy.
The transition from atmosphere to space is not a sudden jump. It is more like a smooth transition from many particles to only some to fewer and then basically none. The lower ends of the cable will still encounter some number of particles which then (in turn) exert some amount of drag. Adding a "floor" to the elevator increases the amount of drag because the "floor" increases the odds of hitting particles.
All that drag exerts yet more forces on the space elevator, increasing the tensile strength requirements. Drag can also alter the orbit or cause a slight torque: this is also no good. (There are other schemes, like Skyhooks which may enjoy this.)
Space elevators are large enough structures that shifting center of masses becomes a concern. If the CoM for the whole elevator/floors/people system changes too much, it will alter the orbit. This is bad news for something trying to stay in GSO.
Adding floors and then putting a lot of stuff on those floors may be too much! Of course, a heavier counterweight may be the key to staving this off, but that's just kicking this problem so far down space-elevator-loading road that it isn't a problem.
All this really comes down to the one and only true answer on Worldbuilding SE: it depends. The tensile strength is likely the largest factor, followed by the size of these floors and orbital mechanics.
Contrary to what is commonly believed, perhaps we can build a space elevator with existing materials. The point is that we don't think about how to build this structure in a really appropriate way, as the authors of this paper or this other paper claims.
The structure should have elasticity to withstand the tidal forces of the Moon, which will have some kind of replacement due to the attack of micrometeoroids, shields to protect from radiation, protection against the actions of the atmosphere, support of solar panels throughout the entire structure , piping for water, oxygen, nitrogen [1], basic structure material, plus exclusive service rails for AI-controlled machines that will take care of repairs, different tracks for getting on and off, which do not really need to be different for cargo and passengers, in addition to perhaps a possible expansion of the structure in order for new tracks to be built.
Anyway, this structure will be huge in itself, even without stopping stations.
You aren't going to make a space elevator economically interesting to build as long as the volume of cargo can be taken into space or brought to Earth through other ways [2], so if you have reached the point of building one or more space elevators, it is because your society it has a big trade between the sides of the atmosphere.
All of these loads going up and down through the elevator will generate forces that the cable must resist and balance, which requires that it be dimensioned much higher than what would be simply a string of diamond nanotubes, graphene, carbyne, duct tape or any other supermaterial.
Here is an interesting point: if the load moves too fast, you will not need many intermediate stations, but the forces of this whole movement will require an oversize of the cables. If the load moves slowly you will need more intermediate stations, and they will require more of the cables as well.
In conclusion, any type of intermediate station, with some type of hotel with panoramic views, maintenance of the cars, emergency services, escape pods, restaurants, etc., will not present a significant effort in the structure of an elevator, unless you want to do a small town.
[1] I don't really know why most science fiction stories or Mars terraforming suggestions ignore the importance of nitrogen in atmospheric composition.
[2] methods that are already and will be in use by society then, the proposal for a space elevator will always looks like radical until its construction be an inevitable necessity.
[3] user535733 deserve all upvotes for mention the last book of Clarke's Space Odyssey.
[4] I failed in learn how make decent footnotes here, someone please edit it
Sure, but you'd lower cargo capacity
Using materials that are currently available, it is not possible to build a space elevator. There are studies into materials that might be up to the task, but nobody has figured out how to make long enough pieces to get to space. So in your story, you're starting with a different reality than the real world. If you create a material that's strong and light and easy to manufacture at scale, then you can make it strong enough to support intermediate stops. You might even build them using a similar material as the cable to keep the weight down. Remember that whatever weight you put on the cable will reduce the cargo capacity of the space elevator.
