Vought SLAM

The Supersonic Low Altitude Missile, known as SLAM and by the program name Project Pluto, was a United States Air Force design for an unmanned intercontinental cruise missile powered by a nuclear ramjet and, in principle, of unlimited range. Air entering the engine was to be heated directly by a reactor instead of by burning fuel. Launched by solid rocket boosters, the missile was to cruise near Mach 4 at high altitude, then drop to about 300 metres and roughly Mach 3, steering by terrain contour matching, while ejecting between 14 and 26 thermonuclear warheads over their targets. The reactor was developed at the Lawrence Radiation Laboratory, and in 1963 the Air Force selected Vought as airframe contractor for a wingless design with a ventral air intake whose sturdy structure earned it the nickname Flying Crowbar. The program was cancelled in July 1964, because intercontinental ballistic missiles had made it redundant and because no one could explain how a flight test of a radioactive vehicle would be made safe, so no airframe was ever built or flown.