It's mission is top secret, and it is the unmanned X-37B, and it has autonomous re-entry.
Star Wars 2010? U.S. military launch space plane on maiden voyage... but its mission is top secret
USAF's Mystery SpaceplaneThere were a lot of potential uses, including surprise reconnaissance: a quick plane change on the other side of the world from your target, and you appear where you are not expected. Satellite inspection was another logical mission, and there were some breifings, videos and graphics which showed the SMV launching weapons.
Is it just for space exploration, will it be used as a moving manoeuvrable satellite or as a weapons delivery system?