After "Gadget," the test device exploded at the Trinity site in the desert of New Mexico, these were the world's first actual nuclear weapons. “Little Boy,” on the left, was dropped on the city of Hiroshima. From the beginning of the Manhattan Project the physicists knew that its simple "gun type" mechanism would need no testing, but this design also made it an extremely unsafe and very inefficient weapon, so dangerous that it was decided not to complete its assembly until the plane carrying it, the Enola Gay, had safely departed the huge U.S. military air field on the island of Tinian. "Fat Man," the more elegant "implosion" design, was an improved version of Gadget packed into a ballistic casing. It was used against the city of Nagasaki.
Neither of these weapons was as powerful as the "triggers" of the thermonuclear devices which I maintained, yet even so these relatively crude devices were powerful enough to kill well over 200,000 people! These weapons were the first two nuclear weapons used in war, hopefully they will remain the last.
- In the Beginning -
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Even before the first components of the uranium gun-type weapon were designed and fabricated the boffins at Los Alamos knew they would need no tests for such a weapon. This was not so much a measure of their scientific confidence as it was reflection of their understanding of how remarkably simple a mechanism would be such a device.
When it came to plutonium-239, however, they soon learned how limited their understanding was of its nuclear reactivity, and thus began the difficult process of designing a device that could utilize such a volitile human-made metal. Thus, the first nuclear device ever tested, "Gadget."