The U.S. Airforce's top secret unmanned space shuttle is set to return to earth by next week, after spending seven months in the space.

The X-37B Orbital Test Vehicle is expected to land at Vandenberg Air Force Base in Santa Barbara County, California, sometime between Friday and Monday.

The Air Force Space Command said in a statement Tuesday the base has begun preparations for the landing, which will depend on the weather and other technical factors.

Preparations for the first landing of the X-37B are underway at Vandenberg Air Force Base. Space professionals from the 30th Space Wing will monitor the de-orbit and landing of the Air Force's first X-37B, called the Orbital Test Vehicle 1 (OTV-1), the statement said.

X-37B Orbital Test Vehicle, which was built by Boeing Co.'s advanced research lab, Phantom Works, is an American unmanned spaceplane. It is operated by the U.S. Air Force for orbital spaceflight missions intended to demonstrate reusable space technologies.

The X-37B will provide a flexible space test platform to conduct various experiments and allow satellite sensors, subsystems, components and associated technology to be efficiently transported to and from the space environment where it will need to function.

If these technologies on the vehicle prove to be as good as we estimate, it will make our access to space more responsive, perhaps cheaper, and push us in the vector toward being able to react to warfighter needs more quickly, said Gary Payton, the Air Force deputy undersecretary for space programs, at the time of the April launch.

The space shuttle is about 29 feet long with a wing span of about 15 feet and is a reusable robotic spacecraft. It is one-fifth the size of the space shuttle and can draw on the sun for electricity by unfolding its solar panels.

The X-37 began as a NASA project in 1999 and then was transferred to the US Department of Defense in 2004. It had its first flight as a drop test on April 7, 2006.

The Air Force won't release an exact figure, but some reports indicate hundreds of millions of dollars were spent on the program.