Although the X-37B has landed, its mission is not yet over.
"Probably the most important demonstration is on the ground," Gary Payton, who served as undersecretary of the Air Force for Space Programs, told reporters before the launch. "Once we get the bird back, see what it really takes to turn this bird around and get it ready to go fly again."
The vehicle expected to fly in the spring is a second spacecraft, but the idea is to cut down the time needed for servicing the space planes from months to days - and at a fraction of the cost NASA pays to get its shuttles ready for flight.
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.
Rather than hydrogen-oxygen fuel cells like the space shuttle orbiters, the X-37B is powered by gallium arsenide solar cells with lithium-ion batteries. It is designed to stay in orbit for up to 270 days, deorbit itself and land autonomously on a runway. NASA's space shuttles can stay in space for up to about three weeks.