The X-37B Orbital Test Vehicle lands at Vandenberg Air Force Base . (Image credit: U.S. Air Force) The military has spoken only in generalities about the spacecraft . Theorists speculate it 's a space bomber or a spy plane against China space station .
The X-37B Orbital Test Vehicle lands at Vandenberg Air Force Base . It spent 674 days in orbit conducting experiments , military says . The military has spoken only in generalities about the spacecraft . Theorists speculate it 's a space bomber or a spy plane against China space station .