Elon Musk’s space exploration company has filed preliminary paperwork to sell shares to the public, according to two sources familiar with the filing, a blockbuster offering that is likely to rank as the biggest ever and make its founder the world’s first trillionaire. A SpaceX IPO promises to be one of the biggest Wall Street events of the year with several investment banks lining up to help raise tens of billions to fund Musk’s ambitions to set up a base on the moon and possibly one day send a man to Mars. The sources spoke on anonymity because they were not authorized to talk publicly about the confidential registration.