The U.S. Air Force's Space Shuttle

The Air Force hopes its unmanned X-37 (in taxi tests in 2007)
will take on some of the functions of the shuttle. (USAF)

Space Shuttle Jr. -- The Air & Space Smithsonian

After 2010, the only spaceplane in the U.S. inventory will be the Air Force's mysterious X-37.

It's been a long wait—in some ways, more than 50 years—but in April 2010, the U.S. Air Force is scheduled to launch an Atlas V booster from Cape Canaveral, Florida, carrying the newest U.S. spacecraft, the unmanned X-37, to orbit. The X-37 embodies the Air Force's desire for an operational spaceplane, a wish that dates to the 1950s, the era of the rocket-powered X-15 and X-20. In other ways, though, the X-37 will be picking up where another U.S. spaceplane, NASA's space shuttle, leaves off.

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