The U.S. Air Force’s top secret X-37B Space Plane made a not-so-secret return to Earth this morning, landing at Vandenberg Air Force Base in California after an impressive 674 days in orbit. Of course, the closely held secret of the X-37B Space Plane – which looks like a miniature version of one of NASA’s Space Shuttles, and carries no crew – isn’t that it was in orbit, but what it was doing up there.