I discussed a moon engine before and I am sure that would provide enough energy to operate a transport system that could extend to the planets. This isn't Gravity Guild quality, but I thought of it. I was wondering why a person wouldn't take off sideways from the moon instead of up and down. Since it is a virtual vacuum, you would just get low orbit and move out as fast as you wanted. So it made me think of a rail mounted and driven by a moon engine that caught velocity and acted as an interface to provide energy and material transport like a space railroad or cargo ship. There are many other ways, but I thought of this and had to get it off my mind. There is no reason that there shouldn't be a base on the moon. Energy could be produced there and even a nuclear reactor could be operated there, but it isn't really necessary to do that.