Nuclear technology the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. Terrestrial plutonium does not currently occur naturally in sufficient quantities for such use, so it must be manufactured in a nuclear reactor. Ultimately, the Manhattan Project manufactured nuclear weapons based on each of these elements. They detonated the first nuclear weapon in a test code-named "Trinity", near Alamogordo, New Mexico, on July 16, 1945. The test was conducted to ensure that the implosion method of detonation would work, which it did. A uranium bomb, Little Boy, was dropped on the Japanese city Hiroshima on
Mark 4 nuclear bomb Mark 4 nuclear bomb The Mark 4 nuclear bomb was an American nuclear bomb design produced starting in 1949 and in use until 1953. The Mark 4 was based on the earlier Mark 3 Fat Man design, used in the Trinity test and the bombing of Nagasaki. The Mark 3 was essentially handmade and constituted an emergency wartime expedient design; the Mark 4 utilized essentially the same basic principles (materials, dimensions of the nuclear core and explosive components) but reengineered the overarching system to be safer and easier to produce. The basic idea was to "GI-proof" otherwise sensitive nuclear weapons.