An anonymous reader quotes Space.com: The record-shattering Mission of the U.S. Air Force's robotic X-37B space Plane is finally over. After circling Earth for an unprecedented 718 days, the X-37B touched down Sunday at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida -- the first landing at the SLF since the final space shuttle mission came back to Earth in July 2011... The just-ended mission, known as OTV-4 (Orbital Test Vehicle-4), was the fourth for the X-37B program... The 29-foot-long (8.8 meters) X-37B looks like NASA's now-retired space shuttle orbiter, only much smaller; indeed, two X-37Bs could fit inside a space shuttle's cavernous payload bay... Most of the X-37B's payloads and activities are classified, leading to some speculation that the space plane could be a weapon of some sort, perhaps a disabler of enemy satellites... But Air Force officials have always strongly refuted that notion, stressing that the vehicle is simply testing technologies on orbit. "Technologies being tested in the program include advanced guidance, navigation and control; thermal-protection systems; avionics; high-temperature structures and seals; conformal, reusable insulation, lightweight electromechanical flight systems; and autonomous orbital flight, re-entry and landing," Captain AnnMarie Annicelli, an Air Force spokeswoman, told Space.com via email in March.

Read more of this story at Slashdot.