Some 673 days after it was launched into space for a secret mission, the Air Force's robotic X-37B space plane is set to return to Earth today—and there's still no word on what it was doing up there. Some rumors say that the robotic mini-space shuttle was interfering with foreign satellites or functioning as a space-based bomber. Sources tell the Daily Beast that the spacecraft is designed to carry specialized payloads of sensors like ground-mapping radars—useful stuff for the military to have on a spacecraft with an orbit over countries including Iran, Afghanistan, and China.
This is the third space mission for the Boeing-built craft, which is overseen by the US Air Force Rapid Capabilities Office. Space.com notes that while all the plane's landings so far have been at an Air Force base in California, Boeing is retooling an old NASA shuttle hangar for the X-37B. The X-37 program has "conducted testing at Kennedy's Shuttle Landing Facility to demonstrate that landing the vehicle at the former shuttle runway is a technically feasible option," NASA says in a statement. (Read more X-37B stories.)