https://en.wikipedia.org/wiki/Boeing_X-37 OTV-4[edit]
The Air Force launched a fourth X-37B mission, designated OTV-4 and codenamed AFSPC-5, aboard an Atlas V rocket from Cape Canaveral Air Force Station on 20 May 2015.[45][69] The launch was designated USA-261 and is the second flight of the second X-37B vehicle.[21] The mission will test a Hall effect thruster in support of the Advanced Extremely High Frequency communications satellite program,[69] and conduct a NASA investigation for testing various materials in space.[4][21][44] The mission was expected to last at least 200 days;[21] as of May 2016 the vehicle remains in orbit.[70]