About this 3D model

Little Boy was the name of the type of atomic bomb used in the bombing of the Japanese city of Hiroshima on 6 August 1945 during World War II , making it the first nuclear weapon used in warfare. The bomb was dropped by the Boeing B-29 Superfortress Enola Gay piloted by Colonel Paul W. Tibbets Jr. , commander of the 509th Composite Group , and Captain Robert A. Lewis . It exploded with an energy of approximately 15 kilotons of TNT (63 TJ ) and caused widespread death and destruction throughout the city. The Hiroshima bombing was the second nuclear explosion in history, after the Trinity nuclear test . Little Boy was developed by Lieutenant Commander Francis Birch 's group at the Manhattan Project 's Los Alamos Laboratory during World War II, a reworking of their abandoned Thin Man nuclear bomb. Like Thin Man, it was a gun-type fission weapon . It derived its explosive power from the nuclear fission of uranium-235 , whereas Thin Man was based on fission of plutonium-239 . Fission was accomplished by shooting a hollow cylinder (the "bullet") onto a solid cylinder of the same material (the "target") by means of a charge of nitrocellulose propellant powder. Little Boy contained 64 kilograms (141 lb) of highly enriched uranium , although 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. Unlike the implosion design, which required sophisticated coordination of shaped explosive charges, the gun-type design was considered almost certain to work so it was never tested before its first use at Hiroshima.