The spacecraft, which was launched from Cape Canaveral Air Force Station in Florida in March 2011, conducted in-orbit experiments during the mission, officials said. It was the second such autonomous landing at the Vandenberg Air Force Base, 130 miles northwest of Los Angeles. In 2010, an identical unmanned spacecraft returned to Earth after seven months and 91 million miles in orbit.
The spacecraft was originally developed by Boeing for NASA and the Defense Advanced Research Projects Agency, or DARPA, but it eventually was turned over to the Orbital Test Vehicle program operated by the Rapid Capabilities Office of the Air Force.
The military has two of the 11,000-pound vehicles, which are about one-quarter the size of the space shuttle. The project started with NASA but was transferred to the Defense Advanced Research Projects Agency in 2004 and is managed by the Air Force Rapid Capabilities Office. It was first launched in 2006.