AP Photo

In the early morning of 16 June, 2012, a top secret spaceplane made a picture perfect landing at the Vandenberg Air Force Base in California. To those unfamiliar with the vehicle, it might have looked roughly similar to the US space shuttle, the manned spacecraft that shuttled astronauts into space for two decades. But this spaceplane, called the X-37B Orbital Test Vehicle, is very different. While it looks like a plane, is launched on a rocket, has a cargo bay and uses some of the same technology as the shuttle, such as thermal shielding to protect it during reentry, it is smaller and unmanned. It is designed to stay in orbit for months on end and can automatically land back on Earth. Perhaps more crucially, the Boeing-designed plane is operated by the US Air Force and its mission is...