America’s most mysterious spacecraft, the X-37B Space Plane, just completed a two-year secret mission that might have involved orbital weapons tests – although details remain sketchy.
The U.S. Air Force X-37B landed at Cape Canaveral on May 6 after spending a record 718 days in space.
Nobody knows what was in the X-37B  or what it was doing in orbit, Space.com reported. The mission was classified, so there has been some speculation it was testing a weapon, such as a satellite disabler, or testing new spy satellite technology.
The Air Force’s 45th Space Wing, which operates the X-37B, denies those rumors but admitted the mission did involve new technologies.
“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,” an Air Force spokeswoman, Captain AnnMarie Annicelli, told Space.com.
“Also, the Air Force Research Laboratory (AFRL), Space and Missile Systems Center (SMC), and the Air Force Rapid Capabilities Office (AFRCO) are investigating an experimental propulsion system,” Annicelli added.
The 45th Space Wing  is the Air Force unit that tests missile technology for the Pentagon.
Some experts speculate the X-37B was testing new sensor technology for the National Reconnaissance Office (NRO) – the agency that operates America’s spy satellites. Others say the mission is a cover for testing weapons in space.
The X-37B is a miniature robotic version of the Space Shuttle and was built by Boeing. Like the shuttle, the X-37B  is launched into orbit by a rocket but it lands on a runway like a plane.
The Air Force has at least two X-37Bs that are used for research in orbit. It was first tested in April 2010 and has been on at least three missions since.
What do you think the X-37B is doing? Share your thoughts in the section below: