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
B61 nuclear bomb three flight tests of the B61-12 tail kit assembly. , the Pentagon was asking for an $11 billion life-extension program for the B61 bomb, which would be the most ambitious and expensive nuclear warhead refurbishment in history. Congress is opposed to this effort for cost and timeline issues and questions for the B61's need. Cost estimates have doubled from $4 billion to $8 billion and production slipped from 2017 to 2020, then grew to $10 billion for life extension plus $1 billion for tail guidance kits and production was delayed to 2021. Sequestration budget cuts in early 2013 have delayed