You’ve probably used their technologies or shopped in their stores. But would you trust them to fly you into space? Microsoft billionaire Paul Allen is the latest to join the commercial space race with his new venture, Stratolaunch Systems. Stratolaunch plans to build the world’s biggest airplane to launch rockets from the sky. The appeal of this kind of air launch is that the aircraft flies a rocket to the most favorable launch latitude for a specific mission. Here’s how the entrepreneurs’ aspirations (and fortunes, as estimated by Forbes) compare.

This article was published in print as "Know Your Space Tycoons."