Air Force's mysterious space drone returns after two years in orbit

Following its longest-ever mission by far, the 11,000 pound X-37B unmanned spacecraft has returned to Earth bearing... well, we don't actually know. You see, after NASA and Boeing developed the craft (about a fifth the size of the Space Shuttle), it bounced over to the Air Force, which is using it for top-secret missions. The X-37B's longest previous flight lasted about 15 months, and this time, it stayed in orbit just shy of two years. As for what it was doing up there, exactly, cue the speculation. Some experts think it was launching spy gear from the pickup-bed-sized payload bay, while others believe it was designed to capture or impair enemy satellites. The Air Force denies all that, saying it was just testing space tech like advanced guidance, robotic systems and autonomous orbital flight. It certainly nailed the latter -- with no human at the controls, the X-37B made a perfect touchdown following a 218 mile-high descent. To see it, check the all-too-brief video below.

[Image credit: Boeing]