Point in fact "satellites are more cost effective" but are not necessarily as capable due to certain weather patterns. The experimental aircraft to replace the high velocity high altitude supersonic Reconnaissance/Observation Spy Plane would be classified under a project dubbed "AURORA". During the tale end of the cold war the Soviet Union's Missle program posed a serious threat to the SR-71 Project, in thus revamping the project for a more sustainable aircraft that was capable of primarily evading an enemy ground airborne threat, secondary an air to air threat, it would involve an aircraft that was capable of hypersonic speeds using a cryogenic fuel, and with an airframe emitting a low radar signature...enter the hypersonic nicknamed by it's flight crew "MINUTE MAN".