| A Nuclear Steamer is an interplanetary drive that uses water as a reaction mass. The basic idea is that the water goes through a nuclear reactor core where it gets heated to a very high temperature and boils. The gaseous steam goes out through a De Laval Nozzle giving reasonable thrust. The thrust is much higher than Solar Steamer but the fuel efficiency ISP is about the same (~190 seconds).
This means that it could be used to launch from the surface of the moon, Solar Steamers cannot collect enough solar energy to do this. Use on the Earth is unlikely due to pollution issues.
Nuclear Steamers are reusable, and would be capable of reaching Lunar orbit and returning in a single stage. The main intended use would be to ferry water from the lunar pole to lunar orbit and hence allow ferrying fuel down to LEO. | 
