X-37B, space plane of mystery

Don't let the similarity in names confuse you--the X-47B of the previous slide is very different from the X-37B, above. True, both are unmanned flying machines, but the U.S. Air Force's X-37B is designed to venture all the way into space. (If it strikes you as reminiscent of the space shuttle, that's no coincidence, really. Once upon a time, it was a NASA program, with roots in the space agency's lifting-body research, much like the shuttle.)

In 2010, the X-37B became the first unmanned vehicle to return from space and land on its own. In March 2011, it went up again on an equally mysterious mission, and it remains there today--its flight having been extended beyond the 270 days originally intended.