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 design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history.

A Fat Man device was detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second and largest of the only two nuclear weapons ever used in warfare. It was dropped from the Boeing B-29 Superfortress Bockscar piloted by Major Charles Sweeney. Its detonation marked the third nuclear explosion in history. The name Fat Man refers to the wide, round shape. Fat Man was an implosion-type nuclear weapon with a solid plutonium core, and later with improved cores.

The first Fat Man 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. It was built by scientists and engineers at Los Alamos Laboratory using plutonium manufactured at the Hanford Site. The second nuclear explosion, and the first used in warfare, was Little Boy, a different device based on uranium. Two more Fat Mans were detonated during the Operation Crossroads nuclear tests at Bikini Atoll in 1946. The three tests in the next series, Operation Sandstone in 1948, used Fat Man devices with improved cores. Fat Man was finally superseded by the Mark 4 nuclear bomb in the Operation Ranger tests.