The hush-hush mission of a robotic miniature space shuttle, known in military parlance as the “Orbital Test Vehicle,” or X-37B, is heading for a California landing this week, the Air Force said Tuesday.

“Preparations for the first landing of the X-37B are under way at Vandenberg Air Force Base in California,” the Air Force said in a statement.

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“Space professionals from the 30th Space Wing will monitor the de-orbit and landing of the Air Force’s first X-37B, called the Orbital Test Vehicle 1 (OTV-1). While the exact landing date and time will depend on technical and weather considerations, it is expected to occur between Friday, December 3, and Monday, December 6, 2010.”

The mini-spaceplane was put into orbit on April 22 for a mission that could last as long as nine months. Apparently, the vehicle made it to full-duration.

The project, which was started by NASA in the late 1990s and later adopted by the military, is intended to test a next-generation space shuttle — the world’s only reusable operational spaceship — in an attempt to trim time between flights and cut costs.

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Unlike NASA’s space shuttles, the X-37B is not meant to carry people. The military is looking at the vehicle as a way to test new equipment, sensors and materials in space, with an eye to incorporating them into satellites and other operational systems.

The X-37B looks like a space shuttle orbiter, with a similar shape and payload bay for cargo and experiments. But it measures 29 feet, 3 inches in length and has a 15-foot (4.5-meter) wing span, compared to the 122-foot (37-meter) orbiters with wing spans of 78 feet.

Unlike NASA’s space shuttles which can stay in orbit about two weeks, X-37B is designed to spend as long as nine months in space, then land autonomously on a runway.

The military plans to fly its second X-37B this spring.

Image: The X-37B before launch (US Air Force)