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The X-37B Orbital Test Vehicle (OTV), the Air Force’s unmanned, reusable space plane. (US Air Force / AFP)

Excerpt from
defensenews.com

WASHINGTON — The US military’s mysterious robot space plane is expected to land this week after a 22-month orbit, officials said Tuesday, but the craft’s mission remains shrouded in secrecy.
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.

A defense official said that the space plane will likely touch down sometime this week and that future missions would seek to extend the vehicle’s technical capabilities and time in orbit.

“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.