All good top secret robotic space plane test missions must come to an end, and so it goes for the Air Force's X-37B, otherwise known as the Orbital Test Vehicle 1 (OTV-1). After seven months of thrilling amateur satellite watchers with its shifting orbital flight patterns and making China nervous, the X-37B could be back on the ground at Vandenberg Air Force Base in California as soon as this Friday.

The X-37B, an unmanned robotic space plane that has been in orbit since April 22, is described by the military as a means to test new materials and sensors in space and otherwise conduct longer unmanned missions in orbital space (the plane is designed to spend up to nine months in orbit). Like the Space Shuttles, the X-37B is reusable, landing on a terrestrial runway automatically at the end of its missions.

Unlike the shuttles, the mysterious Air Force project is not designed to carry human crews. At 29 feet 3 inches, it's not very big (and kind of hard to spot in orbit) but boasts a payload bay that can ferry experiments (or anything else) into space cheaply and quickly.

It's unclear exactly when the Orbital Test Vehicle will touch down – that depends on factors like weather and other technical considerations. But the program won't sit idle for long. The Air Force plans to send its second X-37B aloft this spring.

Discovery News