CAPE CANAVERAL, Florida — A mini military space plane is poised for liftoff Wednesday. But as usual, the Air Force isn't saying much about the experimental unmanned flight.
This will be the fourth flight of an X-37B space plane. The three previous missions also began with rocket launches from Cape Canaveral, Florida.
The mystery test vehicle is designed to orbit the Earth and then land like one of NASA's old shuttles. It is operated robotically, without anyone on board, and is reusable. It is 29 feet (9 meters) long — about one-fourth the size of a NASA shuttle.
The longest X-37B flight lasted 675 days. There's no official word on how long this one will stay up.
NASA has a materials experiment aboard, while the Planetary Society is tagging along with a solar-sail demo.