Re: Space Elevators
Might be feasible on Mars. Certainly possible on the moon, but then a rail launch might work there anyway.
Not feasible on Earth:
1) No current material is strong enough.
2) Everything has to be lifted to orbit and then cables extended down and up. Launch cost prohibitive.
3) How do you anchor the bottom end of cable?
4) Cost of ongoing maintenance / operational life.
An atomic powered plane / spaceship hybrid is more feasible. The Space Elevator is just a nice idea for a story. Just because his idea of Geosynchronous / Geostationary satellites was economic and possible doesn't mean all his ideas work.