Fission Bomb

The first atomic bomb used in warfare was dropped by the United States on August 6, 1945. Called “Little Boy”, it produced an explosion that devastated the city of Hiroshima in Japan and killed tens of thousands of people in less than one minute. “Little Boy” was a gun-type fission bomb, shown here, that generates a nuclear explosion by firing one piece of fissile material into another of the same type. In this case, the material is uranium. The bomb is gun-like in that a small wedge of uranium is fired at a larger, target piece. Upon impact, the two pieces fuse together briefly, forming a supercritical mass (a mass slightly greater than what is necessary to sustain a chain reaction). The rapid release of massive amounts of energy in a limited volume creates the explosion. In “Little Boy”, a mass of uranium about the size of an apple produced an explosion as powerful as 20 kilotons of TNT.

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Manhattan Project; Nuclear Weapons

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