Aptly named after the god of the underworld, the Pluto Project created a cruise missile from hell.

In 1952, the cold war and the arms race prompted the U.S. Air Force, and the Atomic Energy Commission (AEC) to underwrite the development of an under-the-radar-screen supersonic low-altitude missile (SLAM), a cruise missile capable of extended missions carrying up to 12 hydrogen bombs that could be released at low altitude over successive targets. The missile's nuclear ramjet propulsion system would superheat the incoming air blast, ejecting it at a velocity that would thrust the missile forward at six times the speed of the V-1. The entire project was code named Pluto and the nuclear engine was code named Tory. The development contract was awarded to the University of California's Ernest O. Lawrence Radiation Laboratory (now the Lawrence Livermore National Laboratory) in Livermore, 30 miles east of San Francisco, California. On July 1, 1964, the Air Force and the AEC canceled Project Pluto. Perhaps the most compelling reason for killing the project was that the United States was now deploying intercontinental ballistic missiles (ICBMs).