Pin representing the Little Boy atomic bomb

Pin representing the Little Boy atomic bomb

I obtained this pin at  the Atomic Testing Museum in Las Vegas in November, 2013.

Little Boy was the codename for the type of atomic bomb dropped on Hiroshima on August 6, 1945 by the Boeing B-29 Superfortress Enola Gay, piloted by Colonel Paul W. Tibbets, Jr., commander of the 509th Composite Group of the United States Army Air Forces. It was the first atomic bomb to be used as a weapon. The Hiroshima bombing was the second artificial nuclear explosion in history, after the Trinity test, and the first uranium-based detonation. Approximately 600 to 860 milligrams (9.3 to 13.3 grains) of matter in the bomb was converted into the energy of heat and radiation. It exploded with an energy of 16 kilotons of TNT (67 TJ).

Little Boy was developed by Lieutenant Commander Francis Birch’s group of Captain William S. Parsons’s Ordnance (O) Division at the Manhattan Project’s Los Alamos Laboratory during World War II. Parsons flew on the Hiroshima mission as weaponeer. The Little Boy was a development of the unsuccessful Thin Man nuclear bomb. Like Thin Man, it was a gun-type fission weapon, but derived its explosive power from the nuclear fission of uranium-235. This was accomplished by shooting a hollow cylinder of uranium over another hollow enriched uranium cylinder by means of four silk bags of cordite powder. It contained 64 kg (140 lb) of enriched uranium, of which less than a kilogram underwent nuclear fission. Its components were fabricated at three different plants so that no one would have a copy of the complete design.

After the war ended, it was not expected that the inefficient Little Boy design would ever again be required, and many plans and diagrams were destroyed, but by mid-1946 the Hanford Site reactors were suffering badly from Wigner’s disease, so six Little Boy assemblies were produced at Sandia Base. The Navy Bureau of Ordnance built another 25 Little Boy assemblies in 1947 for use by the nuclear-capable Lockheed P2V Neptune aircraft carrier aircraft. All the Little Boy units were withdrawn from service by the end of January 1951.

Location: 3-D3