An O'Neill Cylinder
(AKA Island 3) is a space station concept. Thought up by Princeton Physics professor Gerard K. O'Neill, It has been featured in various Sci-Fi settings like Gundam, Policenauts, Ender's Game and Babylon 5(loosely based).
He also came up with the Mass Driver, which is essentially a powerful catapult. Ideally, a mass driver on the moon would aid with the construction of an O'Neill cylinder in space.