Elton Musk's space exploration company, SpaceX, has filed preliminary paperwork to sell shares to the public, potentially the biggest ever IPO and could make its founder the world's first trillionaire. The IPO is expected to attract significant interest from several major investment banks to help fund Musk's ambitious projects, including setting up a base on the moon, building datacenters the size of several football fields in orbit, and possibly sending a man to Mars. The amount of the money raised has not yet been disclosed.