Thin Man (nuclear bomb) Thin Man (nuclear bomb) "Thin Man" was the code name for a proposed plutonium gun-type nuclear bomb using plutonium-239 which the United States was developing during the Manhattan Project. They aborted its development when they discovered that the spontaneous fission rate of their nuclear reactor-bred plutonium was too high for use in a gun-type design, due to the high concentration of the isotope plutonium-240. In 1942, prior to the Army taking over wartime atomic research, Robert Oppenheimer held conferences in Chicago in June and Berkeley, California, in July at which various engineers and physicists discussed nuclear bomb design issues. A
Mark 8 nuclear bomb bomb, was developed as a lightweight airburst (surface target) bomb. The Mark 10 project was cancelled prior to introduction into service, replaced by the much more fissile-material-efficient Mark 12 nuclear bomb implosion design. Mark 8 nuclear bomb The Mark 8 nuclear bomb was a nuclear bomb, designed in the late 1940s and early 1950s, which was in service from 1952 to 1957. The Mark 8 was a gun-type nuclear bomb, which rapidly assembles several critical masses of fissile nuclear material by firing a fissile projectile or "bullet" into a hollow opening in a larger fissile "target", using a system which