I remember reading somewhere (no cite - don’t have it anymore) that there is a potential for an very big voltage difference to build up on the top to the bottom of the tether. Didn’t this cause some other NASA tether failure in the 1990’s? Is there anyway to overcome this?
Think of it not as a flaw, but a feature - if there is a voltage difference over the ends of the elevator, you should try to use it to power the elevator cars. Thaey are going to need all the power sources they can get.
NM
The record for unmanned balloon flight is 170,000 feet or about 35 miles.
The problem isn’t so much the “weight” of the space elevator cable. A space elevator doesn’t act like a giant tetherball on a playground. The satellite at the end would stay in geosynchronous orbit regardless if the elevator cable is attached. It’s that the rest of the cable isn’t in geosynchronous orbit. As this video shows, the smaller an object’s orbit is, the faster it needs to travel in order to maintain that orbit. So at each point along the cable, the cable will want to move at a different speed or fall out of the sky. having the cable not quite reach the ground doesn’t solve that.
And I’m not quite sure if the weight of the cable would pull it to the ground anyway, or if it would just fly off into space and try and form a ring around the Earth.
The problem is exactly the weight of the elevator cable, and a ring is the last thing it would try to form. As I said before, the natural configuration that things in orbit will tend to assume is with their long axis radial.
There is no reason that a space elevator couldn’t be attached to a balloon floating in the air, rather than to the Earth’s surface; at the end of the tether, there is no tension at all - it is suspended from the sky like a rope hanging from a hook.
However, that is only true if you don’t try to use it; any ascending payload would drag the cable sideways because of Coriolis effects, and a descending payload would drag it sideways in the opposite direction.
A Space elevator would behave in a deeply counterintuitive way, if we were ever able to build one (which seems unlikely).
I’s been awhile since I studied orbital mechanics so I went and looked it up.
Technically it’s the tension caused by tidal forces pulling the cable towards the Earth (“weight” if you prefer) against centrifugal forces pulling the other end away from the Earth (iow “counterweight”). The counterweight satellite needs to be well above geosynchronous orbit to keep the cable taught. So it actually is like a tetherball.
I think I was thinking about it backwards or something. It makes sense that the cable would always be pulled towards the Earth since gravity is a function of distance.
True, but so long as the mass of the payloads is small compared with the mass of the cable as a whole (which it almost certainly will be), the sideways pull will be small.