4 ms·
Space elevators don't work on the moon. While gravity is weaker, the moon's rotation period is also much lower. To build a space elevator, its center of mass mu
by jjk166 5y ago
Space elevators don't work on the moon. While gravity is weaker, the moon's rotation period is also much lower. To build a space elevator, its center of mass must be in a stationary orbit over the body. A geostationary orbit around the moon (selenostationary) would be about 88,000 km. The moon's Hill sphere, the region where its gravity dominates and thus things can stay in stable orbit around it, is only about 58,000 km. Basically a lunar space elevator would be so tall that Earth's gravity would yoink it off the moon.
You could potentially build a skyhook on the moon, which a space elevator is merely a special case of, but you lose a lot of the advantages of a space elevator - namely you still need something to blast off the surface to reach the skyhook, and you have to carefully time it because everything's moving at extremely high speed. Saves a lot of fuel though.
- Valgrim 5y agoOn the moon, you'd need a mass driver in conjunction with a skyhook.
- jhgb 5y agoBut why not just build a mass driver, then? It's a somewhat large horizontal structure, compared to a space elevator which is an absolutely humongous vertical structure. If you can reach 2 km/s on magnetic rails, you don't need anything else to launch from the Moon -- or even land on it.
- Valgrim 5y agoBecause unless you reach escape velocity, you still need to adjust your trajectory to insert into orbit, or else you're just going to crash back on the surface. If you use a rocket that's fine you just point in a different direction and burn, but if you're trying to launch, say, a few trillion tons of stuff, you need something a tad more efficient
- hoffspot 5y agoExcellent use of "Yoink"
- sobellian 5y agoWhat if you position the counterweight of the space elevator at the L1 lagrange point of Earth/Moon? Since the moon is tidally locked, it should always stay about the same spot relative to the lunar surface.
- panick21_ 5y agoThe most likely place for a space elevator is clearly Mars. At the Mars Society conference there was a talk where somebody went deep into space elevators and Mars is the most likely place to make one anytime soon. Its far easier then on earth. One the moon you might just use a mass driver instead, at least for bulk materials. And if not that a reusable rocket works just fine.