Not all U.S. drones are flying over Southwest Asia. At least one of them is in space.

The U.S. Air Force on Wednesday launched an X-37B space plane from Cape Canaveral. It went into space aboard an Atlas V rocket and it will orbit the earth for an unknown amount of time, but it could be a year or more.

The Air Force has two X-37Bs that, like the Space Shuttle, take off like a rocket and land (video) like a plane. They’re unmanned, about a quarter of the size of the now-retired Space Shuttle and have cargo bays about the size of a pickup truck bed. This is the fourth known X-37B mission.

The Air Force is enthusiastic about the X-37B. “It’s really for cool things. For instance, it goes up to space but, unlike other satellites, it actually comes back. Anything that we put in the payload bay that we take up to space, we can now bring back, and we can learn from that,” Gen. John Hyten, the head of Air Force Space Command, told CBS’ 60 Minutes last month.

The Air Force won’t say which of its X-37Bs was sent up last week. We do know some of the payload aboard the plane, however. There is an ion-based thruster to be tested which, if successful, could revolutionize space travel. There is also a solar sail and an experiment to test the effects of space on many different materials.

A previous flight was thought by some to be a spy mission on a Chinese space station, which the Air Force denies was the case. When asked by 60 Minutes’ David Martin if the X-37B will become a weapons system, Gen. Hyten replied, “I cannot answer that question. I’m not going to say what it’s going to become ‘cause we’re experimenting.”

-Steve Straehley

To Learn More:

U.S. Air Force Launches X-37B Space Plane on 4th Mystery Mission (by Mike Wall, Space.com)

X-37B Spaceplane Embarks on Fourth Voyage in Orbit (by Justin Ray, Spaceflight Now)

The Secret American Space Drone is Going Back Into Orbit (by Tim Fernholz, Government Executive)

Mysterious Unmanned U.S. Space Plane Lands (by Ken Broder, AllGov California)

Mysterious U.S. Space Spy Plane Probably Tracking China (by Noel Brinkerhoff, AllGov)