The U.S. Air Force began developing this air-launched antisatellite missile (ASAT) to destroy enemy satellites after the USSR demonstrated its ability to attack satellites in space. At the tip of this two-stage missile was a Miniature Homing Vehicle (MHV). Once it separated from the missile, the MHV homed in and destroyed a satellite by direct collision, rather than by detonation of a warhead - a concept known as "hit-to-kill." The ASAT's maximum intercept altitude was at least 560 kilometers (350 miles). Five ASATs were flight tested, with the one launched from an F-15 fighter in September 1985 successfully intercepting and destroying an orbiting NASA satellite. The Air Force cancelled the ASAT program in the late 1980s. LTV made this unflown ASAT, and the U.S. Air Force transferred it to NASM in 1990.