Back Fat Man Afrikaans الرجل البدين (قنبلة) Arabic Fat Man AST Fat Man Azerbaijani Дебелака Bulgarian Fat Man BJN ফ্যাট ম্যান Bengali/Bangla Fat Man Catalan Fat Man Czech Fat Man Danish
| 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 | 6.4 kg |
| 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. It was built by scientists and engineers at Los Alamos Laboratory using plutonium from the Hanford Site, and one 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Crossroads nuclear tests at Bikini Atoll in 1946, and some 120 were produced between 1947 and 1949, when it was superseded by the Mark 4 nuclear bomb.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.