The U.S. Air Force is set to launch its secretive “space plane” on Wednesday, the fourth flight of the mysterious unmanned X-37B Orbital Test Vehicle.

Unlike previous missions, however, the Air Force has offered details of at least part of its mission: an experimental Hall thruster. This electric propulsion device ionizes a noble gas such as xenon. The device would allow a spacecraft to carry larger payloads and perform more orbital maneuvers than one powered by traditional rocket engines.

“Space is so vitally important to everything we do,” Maj. Gen. Tom Masiello, commander of the Air Force Research Laboratory, said in a news release. “Secure comms, ISR, missile warning, weather prediction, precision navigation and timing all rely on it, and the domain is increasingly contested. A more efficient on-orbit thruster capability is huge. Less fuel burn lowers the cost to get up there, plus it enhances spacecraft operational flexibility, survivability and longevity.”

The X-37B is capable of extended missions in space; one such journey lasted 675 days. The Air Force has said little about what the spacecraft has been doing, and the details about the Hall thruster represent some of the most detailed explanations it has offered about an X-37B flight.

The craft resembles the space shuttle, but is roughly a quarter of the size of its retired cousin. Like the shuttle, it’s both reusable and capable of landing like an airplane, as shown in this Air Force image from a previous mission:.. see more

source: huffingtonpost