Naval History and Heritage Command

National Museum of the U.S. Navy

Fat Man - Nagasaki - August 9, 1945

The atomic bomb used at Nagasaki on August 9, 1945, was "Fat Man".   The bomb was dropped by a USAAF B-29 airplane named "Bockscar", piloted by U.S. Army Air Force Major Charles Sweeney.  The bomb weighed 10,000 pounds and had a diameter of 60 inches.  It utilized the explosive power of dynamite to create pressure on a ball of Plutonium in the weapon's center, which squeezed the atoms closer together until nuclear fission was achieved.  "Fat Man" was tested in July 1945.  Previously, on July 26, the bomb, along with "Little Boy", was transported to Tinian Island by USS Indianapolis (CA-35) for final assembly.  Four days later, Japanese submarine, I-58, sank Indianapolis, northeast of Leyte.

A replica of Fat Man can be found at "The Navy In The Nuclear Age" exhibit area in the Cold War Gallery, Bldg. 70.   

Image:  77-BT-67:  Tinian Island, August 1945.  Boeing B-29 "Bockscar" Superfortress plane.   Official photograph of the Office of the Chief of Engineers, now in the collection of the National Archives.