Fat Man

Fat Man
Replica of the original Fat Man bomb
Type	Nuclear fission gravity bomb
Place of origin	United States
Production history
Designer	Los Alamos Laboratory
Produced	1945–1949
No. built	120
Specifications
Mass	10,300 pounds (4,670 kg)
Length	128 inches (3.3 m)
Diameter	60 inches (1.5 m)
Filling	Plutonium
Filling weight	6.2 kg[1]
Blast yield	21 kt (88 TJ)

"Fat Man" (also known as Mark III) was the codename for the type of nuclear weapon the United States detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the first being Little Boy, and its detonation marked the third nuclear explosion in history. The first one was built by scientists and engineers at Los Alamos Laboratory using plutonium manufactured at the Hanford Site and was dropped from the Boeing B-29 Superfortress Bockscar piloted by Major Charles Sweeney.

The name Fat Man refers to the early design of the bomb because it had a wide, round shape. Fat Man was an implosion-type nuclear weapon with a solid plutonium core. The first of that type to be detonated was the Gadget in the Trinity nuclear test less than a month earlier on 16 July at the Alamogordo Bombing and Gunnery Range in New Mexico. Two more were detonated during the Operation Crossroads nuclear tests at Bikini Atoll in 1946, and some 120 were produced between 1947 and 1949, when it was superseded by the Mark 4 nuclear bomb. The Fat Man was retired in 1950.