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SpaceX is reporting for Air Force duty for the first time.

The company's Falcon 9 rocket will carry the US Air Force's secretive X-37B miniature spaceplane into orbit in August, Air Force Secretary Heather Wilson said Tuesday.

It was thought SpaceX's first Air Force mission would be the launch of a GPS satellite announced last year and scheduled for some time in 2018. Instead, SpaceX will this year take over the X-37B launch from United Launch Alliance, a joint venture of Boeing and Lockheed Martin. ULA's Atlas 5 rockets have successfully carried the spaceplane into orbit for four previous missions, and the spaceplane itself is built by Boeing. SpaceX founder Elon Musk has publicly sparred with the Air Force over what he saw as favoritism in the awarding of launch contracts to ULA.

Given the secrecy surrounding the X-37B, it's hard to say why and when the USAF awarded this contract to SpaceX. According to the Air Force, the unmanned spaceplanes (there are at least two of them) test guidance, navigation and control systems and advanced propulsion systems, with the goals being to explore reusable-spacecraft technologies and conduct experiments that can be returned to, and studied, on Earth.

The Air Force is also testing the X-37B's endurance -- one of the planes recently spent 718 consecutive days in orbit. As to what else the spaceplane does up there, speculations range from top-secret reconnaissance to anti-satellite functions.

Wilson made the announcement during webcast testimony before the US Senate Armed Services Committee.