Manned version of X-37 space plane

When the Space Shuttle Atlantis touched down for the final time on July 21, 2011, it looked as if the notion of a manned spacecraft capable of going into orbit and then landing like a conventional airplane had been abandoned.

The US government appears to be in favour of returning to Apollo-style space capsules with anything like the Shuttles being relegated to the private sector.

Arthur Grantz, chief engineer of Space and Intelligence Systems' Experimental Systems Group at Boeing, delivered a paper at American Institute of Aeronautics and Astronautics' (AIAA) Space 2011 conference indicating that the U.S. Air Force and Boeing are already on the way toward developing a manned Shuttle replacement based on the X-37B robot space plane.

X-37B
The X-37B is one of the US Air Force's most highly visible yet most secret projects of recent years.

A robot spacecraft that looks like a miniature space shuttle without a flight deck was bound to attract public attention, but its mission has remained hidden under the blanket word "classified."

The government has released some information about the X-37B. In part, it's an experimental test bed based on the Boeing X-40 lifting body.

With an overall length of a little under 30 ft (9 m) and a wing span just under 15 ft (4.5 m), it's small enough to fit easily into the Shuttle's cargo bay, but it's still capable of acting like a robot version of the larger, older spacecraft.

Launched on top of an Atlas booster at Vandenberg Air Force Base, it can carry payloads into space, return them to earth and then land like a conventional aircraft. The difference is that it doesn't require a pilot or ground control because it can land by itself.

It also has much more endurance than the old Shuttle. While the Shuttle never remained in orbit for as long as three weeks, the X-37B has already broken the record for a reusable spacecraft in orbit: 244 days.

It's rated to remain on station for 270 days if needed.