Known
as "the hill," Los Alamos produced two bombs. One, nicknamed
Little Boy, was a gun-type weapon that used U-235. A slug of U-235
would be projected down a gun barrel into the center of another
piece of U-235. When combined, a nuclear explosion would occur.
The second bomb, Fat Man, used implosion to detonate plutonium.
Here, explosives would surround the plutonium ball. When detonated,
they would compress the plutonium, causing a nuclear explosion.