Alright, I was playing around with an old idea again, something Paul Birch talked about with his Orbital Ring System and Kingsbury also elaborated on for his LEO port in one of his novels, 'Moon Goddess and The Son' (talk about the future not being what it once was- that dates back to the Eighties and had a number of assumptions that went away along with the end of the Cold War!)
Falling Moon rock, kicked out of the lunar gravity well and dropped down to Earth is moving at just under escape velocity, or about 11 kilometers per second. A kilogram @ 11,000 meters/s^2 has 121 million joules of energy, or about 33 kilowatt hours worth of electricity- a dollars worth @ $.03/kWhr. If we already had a mass driver on the edge of the atmosphere, which is to say, either an Orbital Ring System, a Lofstrom Launch Loop, or a Forward Fountain Bridge reaching up to space (so you see, the idea has been around, and reinvented constantly! 8-), we could have the worlds' tallest dam going... if we already had the ORS/LLL/FFB or any of the other things that would make cheap access to space and developing the Solar System possible.
I did work out an orbital ring system, purely back-of-the-envelope, based on a 16 KPS matter-stream dyanmicly supporting three times as much stuff- the containment for the mass-beam/matter-stream, orbiters and cargo, passengers and spaceport infrastructure. At 12 tonnes per kilometer, and a 100 miles/160 km altitude, that would be just under half a millon tonnes of megastructure. A bridge on the edge of space, with ladders hanging down to let us climb up to heaven, hook a ride on some very fast matter and accelerate escape velocity. Outgoing traffic, infalling mass, a mass transit system to make the poor old Space Shuttle look like a joke...