http://www.washingtonpost.com/blogs/the-switch/wp/2017/09/07/spacex-set-to-launch-the-x-37b-the-pentagons-secretive-autonomous-space-drone/

In the Pentagon's vast arsenal there is little quite like it: a super-secret space drone that looks like a miniature version of the space shuttle, but orbits the Earth for months, even years, at a time. Doing what? The Air Force won't say.

On the tarmac, the X-37B, as it is called, looks tiny, standing not much taller than a person. Its wingspan measures less than 15 feet, and it weighs in at just 11,000 pounds. But over the course of six flights, it has proved to be a rugged little robotic spacecraft, spending a total of nearly six years, probing the hard environment of the high frontier.