The X-37B Orbital Test Vehicle (OTV), the Air Force’s unmanned, reusable space plane. (US Air Force / AFP)
The unmanned X-37B, which looks like a miniature space shuttle, is due to glide back to Earth after having launched on Dec. 11, 2012, on a mission that military officers say is strictly top secret.
“Preparations for the third landing of the X-37B are underway at Vandenberg Air Force Base” in California, said a US Air Force spokesman, Captain Chris Hoyler.
“The specific parameters are unreleasable,” the official said.
The Air Force says the X-37B can test technology for “reusable” spacecraft and conduct unspecified experiments that can be studied on Earth.
The X-37B, manufactured by aerospace giant Boeing, weighs five tonnes and measures about 29 feet (8.8 meters) long, with a wing span of roughly 15 feet across.
Traveling at speeds 25 times faster than the speed of sound, the vehicle is launched into space on the back of a rocket and, once its mission is complete, returns from orbit like a plane.