For just over 500 days, the US Air Force’s mysterious X-37B OTV-3 robotic space plane has been casually orbiting the Earth. X-37B looks like the Space Shuttle, and launches into space on the back of a rocket like the Shuttle, but it’s actually fairly small at just under nine meters (30 feet) in length. What’s truly weird, though, is that I’ve now told you everything that we officially know about the X-37B — its payload, current mission, and combat capabilities are completely unknown. X-37B OTV-3, one of the world’s largest artificial satellites, has been up there for 500 days, shows no sign of coming down any time soon, and we have no idea what it’s doing or what it can do.
The X-37 started life way back in 1999 when NASA asked Boeing’s Phantom Works division to develop an orbital test vehicle (OTV). The X-37 was originally conceived as an unmanned, robotic spacecraft that would rendezvous with satellites to refuel or repair them — but in 2004 the project was transferred to DARPA and it has been highly classified ever since. Starting in 2010, the US Air Force has launched two X-37B spacecraft on three missions (OTV-1, OTV-2, and OTV-3), perched atop an Atlas V rocket. The photo above, of OTV-2′s landing in 2012, is one of only a handful of photos that are publicly available of the vehicle. All three missions have spent a long time in space (220+ days), with OTV-3 now having spent over 500 days in low-Earth orbit (LEO).