LOS ANGELES, June 16 (Xinhua) -- After spending more than 15 months orbiting Earth on a mystery mission, the U.S. Air Force's X- 37B unmanned, reusable space plane finally returned to the ground on Saturday.
The space plane, known as the Orbital Test Vehicle 2 or OTV-2, was on its second ever space mission. It glided back to Earth on autopilot, touching down at the Vandenberg Air Force Base in California at 5:48 a.m. PDT (1248 GMT) Saturday, the Base announced in a news release.
OTV-2, which was launched on March 5, 2011, conducted on-orbit experiments for 469 days during its mission. The estimated mission length for the space planes is about 270 days. The OTV-2 mission and its predecessor were both launched from the Cape Canaveral Air Force Station in Florida.
The U.S. Air Force is preparing for another launch of the X-37B from the Cape Canaveral station sometime in fall 2012 aboard an Atlas V booster. This will be a re-flight of the first X-37B OTV, which was successfully recovered at the Vandenberg base on Dec. 3, 2010.
"With the retirement of the Space Shuttle fleet, the X-37B OTV program brings a singular capability to space technology development," said Lt. Col. Tom McIntyre, the X-37B program manager. "The return capability allows the Air Force to test new technologies without the same risk commitment faced by other programs."
The X-37B space planes are built in tight secrecy by Boeing, and look much like NASA's retired space shuttles, only much smaller. Each X-37B spacecraft is about 8.8 meters long and 4.5 meters wide.
Industry analysts said the spacecraft could be a precursor to an orbiting weapon, capable of dropping bombs or disabling enemy satellites as it circles the globe.