US Air Force’s X-37B Space Plane Passes 400 Days In Orbit Written 19 October 2018

SPACE reports that the US Air Force’s X-37B space plane “has now passed the 400-day mark” for its classified mission in orbit. The Orbital Test Vehicle (OTV-5) mission began October 7, 2017 when it launched mounted “atop a SpaceX Falcon 9 rocket from Launch Complex 39A at NASA’s Kennedy Space Center in Florida.” The only OTV-5 payload “revealed to date by Air Force officials is the Advanced Structurally Embedded Thermal Spreader, or ASETS-II.” The device is used to test experimental electronics and “oscillating heat pipes for long-duration stints in the space environment.” The ASETS-II’s “three primary science objectives are to measure the initial on-orbit thermal performance, to gauge long-duration thermal performance and to assess any lifetime degradation.” The next X-37B mission, “OTV-6, may lift off in 2019 aboard a United Launch Alliance Atlas-V (501) rocket.” 
More Info (SPACE)