An Air Force X-37B spaceplane just completed its 718th day in orbit, making it the longest mission yet for a secretive military test program.
The US military has launched five unmanned X-37B spaceplanes into orbit over the past decade, and each flight has been longer than its predecessor.
The current mission has no specified end date, according to Air Force spokesman Major William Russell. The spacecraft will return to Earth only after its completed all its objectives, he said.
The details of those objectives remain a closely guarded secret.
The X-37B program tends to attract public interest because of that secrecy: the Air Force does not share the locations of the X-37B planes while they’re in orbit, although amateur astronomers have made a sport out of spotting the spacecrafts with telescopes.
What is known is that the military is using the planes to develop reusable spaceflight technology.
Officials don’t necessarily want to reuse the same X-37B plane multiple times, but the Air Force designed the crafts to try out new navigation systems as well as methods for reentering the Earth’s atmosphere and for landing safely back on earth.
The X-37B is also popular among space fans because of its unique design. The planes, which look like miniature space shuttles, launch into orbit atop powerful rockets and then break away to carry out