The X-37B Orbital Test Vehicle (OTV) – the US Air Force’s top-secret automated space plane – is finally set to return to Earth after a year in space. Although not much is known about the spacecraft, we do know that it powered itself during its time in orbit with a deployable solar panel.

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The space plane, which is due to land at Vandenberg Air Force Base in California next month, was launched into space on March 5, 2011. While it is not known what the payload was, it was carried into orbit via an Atlas 5 booster from Cape Canaveral Air Force Station in Florida.

The X-37B operates very much like an unmanned drone. It measures 29 feet (8.8 meters) long and 15 feet (4.5 m) wide and has a payload bay about the size of a pickup truck. The craft is outfitted with deployable Gallium arsenide solar cells that charge lithium-ion batteries for the craft’s internal systems.

Based on NASA’s X-37 design, the unmanned OTV is designed for vertical launch and low Earth orbit altitudes. Its mission is to perform long-duration space technology experimentation and testing. Upon command from the ground, the OTV can automatically re-enter the atmosphere, descend, and land on a runway.

By all accounts, the X-37B’s mission has been a complete success surpassing its 270-day baseline design specifications. Speaking in April the 28th National Space Symposium in Colorado Springs, General William Shelton, commander of Air Force Space Command said: “Although I can’t talk about mission specifics, suffice it to say this mission has been a spectacular success.”

The Air Force hopes that the  X-37B will become a reliable, reusable, unmanned space test platform that will aid space experimentation, risk reduction and be the first step in the operational development for reusable space vehicle technologies.

+ USAF X-37B Orbital Test Vehicle