|South African gold mine. Looks like it could be on the moon.|
A while back I was thinking that some kind of electric train would be a good way to launch things from the moon. There is no air, so there would be no air resistance, so if you could build an electric vehicle that could reach orbital velocity, you could launch things (spacecraft, rocks, luggage, whatever) into orbit. You would still need some rocket power to circularize the orbit, and orbit velocity would probably be impossible to achieve with a wheeled vehicle, so you would probably need to support your 'car' with magnets.
To launch something of any size you would need a pretty big chunk of electricity. It is possible to build big generators, so it could be done.
But all this got me to thinking. If we could launch something using electric power, could we not also land something using electric power? The navigation would be extremely difficult. You would have to mate two vehicles that were traveling several miles a second. Of course, this is exactly what happens when we send a Soyuz or resupply ship to the ISS (space station). It's just that you don't have the ground flying by mere meters away. And you have all the time in the world, it's not like you are going to run out of track like you are on the moon. Well, okay, you could build a track that went all the way around the moon, but that might take a while.
But suppose you can master this. Slowing down a spacecraft is going to require dissipating a tremendous amount of energy. What are we going to do with it? That's when I got this really great idea.
We dig a mine shaft straight down into the moon a hundred miles or so. We build a track down the side of this shaft just like the one we have laid on the surface to launch and recover spacecraft. We put a really big rock in the mine shaft connected to a car that rides on the track. When we want to launch a spacecraft, we haul the rock to the top of the shaft. When we release it, it falls down the shaft and generates a huge amount of electricity that we funnel to the launch track to propel the launch vehicle.
When we want to recover a spacecraft, we start with the rock at the bottom of the shaft. When the car mates with the spacecraft, we connect the cables between the two and energy from the spacecraft hauls the rock to the surface.
There are a few technical details that will need to be worked out, but I am sure that if we apply ourselves we can get them sorted out in the next thousand years or so.
Update June 2018 replaced missing picture.