If you built this space elevator, won’t it be necessary to have a “counterelevator”, so to speak, located 180 degrees away? - Jinx
What for? The Earth isn’t going to become unbalanced by not having elevators on both sides.
Or did you mean two elevator cars on the same space elevator with one ascending while the other descends? That would help keep the elevator from gaining or losing too much orbital momentum, although it wouldn’t be perfect.
No, you’d just have a counterweight, just like a regular elevator does.
From my understanding, the earthbound base of the space elevator is going to be on a floating platform… not that you could ‘pull’ the earth out of orbit anyway, but if you could, this would prevent it. I think.
Regarding the counterweighted elevator car itself, I don’t know, but I would hope there would be more than one actual car on the thing… one going up, one coming down… or even multiple cars in each direction.
That would be cool.
Sure hope they build it!
When payloads are moved downwards, they will generate a significant lateral force in the same direction as the earth’s spin (in the same way that a ballet dancer pulling in her arms will generate forces that increase the speed of a pirouette); payloads going upwards will generate lateral forces in the other direction.
It might seem that a solution would be sending one up at the same time as another comes down, but this will only generate balanced lateral forces at the midpoint, where the two payloads pass. At other points on the journey, the lateral forces would be pushing in opposite directions on different sections of the elevator.
Another solution might seem to be sending up lots of small payloads in series, at the same time as lots of small counterweights descend in series, so that the lateral forces generated by the descent or ascent of an object are, at any one time, matched by another moving in the opposite direction, relatively close by. But unless we’re planning to bring back the same amount of mass as we send up, there’s still a net force in the opposite direction to the spin of the earth.
Perhaps this can be overcome by the use of lateral thrusters, but that will require fuel, which adds weight, which requires bigger engines etc.
Does anyone know how the lateral forces are proposed to be dealt with?
Only that eventually the lateral force will push against the Earth at the anchored end. But how force transmits through a tens of thousands of kilometers-long ribbon without whipping the whole thing around, I don’t know.
But what if all the Chinese people ride to the top and then jump off?
There’ll be a force but it won’t be a significant force. In layman’s terms: Earth very big: elevator very small. There’ll be no more need to have a counter-elevator due to the effect on the planet than there is to have counter-flights every time a plane flys around the world.
But while the elevator’s effect on the planet will be negligible, the elevator’s effect on the elevator could be significant. Things like counterwieghts may be necessary for the elevator to function efficiently.
Another point with a Space Elvator is that you can (aproximately) balance one payload going up with another payload going up. Below the geosynch point, things will “fall” downwards, but above that point, they’ll “fall” upwards, so a car on the top half can partly balance a car on the bottom half with a straight line of cable between them (no need for pulleys or the like). With enough cars each travelling a short enough distance, and with equal masses inbound and outbound, one can make this balance arbitrarily fine, leading to an arbitrarily low energy cost to operate the elevator.
Nor is equal masses inbound and outbound an implausible assumption. One of the first things we’d do if we had a Space Elevator would be to build another one and send it to Mars. One could then make a tidy profit at both ends by trading water from Earth with an equal mass of iron ore from Mars. Even if your destination world doesn’t have valuable resources, you can just ship back worthless rocks.