Space flight: Flight of the phoenix Though the Space Shuttle programme ended in 2011, America seems unable to give up the idea of a reusable space plane. The X-37B, which began its third orbital mission on December 11th, is such a plane - albeit, unlike the Shuttle, unmanned. The X-37 project started in 1999, under NASA's auspices, and was taken over by the air force in 2006. That led to all sorts of conspiracy theories about what the vehicle is doing. These range from spying on China's manned space programme to deploying weapons in space. Like the Shuttle, the X-37B is not fully reusable. The Shuttle had a disposable external fuel tank to power its motors. The X-37B has a throwaway booster. The craft was launched from the air force's rocket station on Cape Canaveral just after 1pm. When it will return to Earth, though, is as mysterious as what it actually gets up to when it's out there.