There, the heavy cruiser USS Indianapolis shipped the collection of parts to Tinian Island in the Pacific Ocean south of Japan, where it arrived on July 26. Various components of the bomb were transported by train from Los Alamos, New Mexico, to San Francisco, California. The final construction of Little Boy occurred in stages. While the theory of the gun firing concept was not fully tested until the actual bomb dropped on Hiroshima, scientists conducted successful lab tests on a smaller scale that gave them confidence the method would be successful. The cylinder fit precisely over the spike as the two collided together creating the highly explosive fission reaction. The target was in the shape of a solid spike measuring seven inches long and four inches in diameter. In effect, one slug of uranium hit another after firing through a smooth-bore gun barrel. In Little Boy, the first atomic weapon, the fission reaction occurred when two masses of uranium collided together using a gun-type device to form a critical mass that initiated the reaction. The Manhattan Project team agreed on two distinct designs for the atomic bombs. The enriched uranium-235 was the critical element in creating an explosive fission reaction in nuclear bombs. Government in the late 1930s to study enriched uranium in nuclear chain reactions. Scientists on the project drew from the earlier work done by physicists Enrico Fermi and Leo Szilard, both of whom received funding from the U.S. Facilities for the research were set up in Manhattan, Washington State, Tennessee, and New Mexico. Groves oversaw the military’s participation, while civilian scientist Robert Oppenheimer was in charge of the team designing the core details of Little Boy. Scientists developed the technology for the atomic weapon during the highly classified project code-named “The Manhattan Project.” U.S.
In an instant when the first bomb was dropped, tens of thousands of residents of Hiroshima, Japan were killed by “Little Boy,” the code name for the first atomic bomb used in warfare in world history.
Two American atomic bombs ended World War II in August 1945, and the devastation will be forever remembered. Hancock, an archives technician at the National Archives at College Park, MD. August 6, 2020, marks the 75th anniversary of the dropping of the first atomic bomb.