Nuclear fission Mexico, which was the scientific hub for research on bomb development and design. Other sites, notably the Berkeley Radiation Laboratory and the Metallurgical Laboratory at the University of Chicago, played important contributing roles. Overall scientific direction of the project was managed by the physicist J. Robert Oppenheimer. In July 1945, the first atomic explosive device, dubbed "Trinity", was detonated in the New Mexico desert. It was fueled by plutonium created at Hanford. In August 1945, two more atomic devices – "Little Boy", a uranium-235 bomb, and "Fat Man", a plutonium bomb – were used against the Japanese cities of Hiroshima
B53 nuclear bomb megaton-range) bomb to replace the earlier Mk 41. A revised version of the Mk 46 became the TX-53 in 1959. The development TX-53 warhead was apparently never tested, although an experimental TX-46 predecessor design was detonated 28 June 1958 as Hardtack Oak, which detonated at a yield of 8.9 Megatons. The Mk 53 entered production in 1962 and was built through June 1965. About 340 bombs were built. It entered service aboard B-47 Stratojet, B-52G Stratofortress, and B-58 Hustler bomber aircraft in the mid-1960s. From 1968 it was redesignated B53. Some early versions of the bomb were dismantled beginning in