obtaining the nuclear material that makes a nuclear bomb go boom. the hiroshima bomb in 1945, it was basically structurally speaking, a gun. inside the outer casing that looked like a cartoon version of a bomb was basically a gun mechanism used an explosive charge to fire a piece of highly enriched uranium into another piece of highly enriched uranium. that create create add nuclear reaction and a nuclear explosion. the second bomb the u.s. dropped on japan three days later, that was built in a different way. again, used an explosive charge. in this case, it was used for a different material. the nagasaki bomb used an explosive charge to squeeze together a hunk of plutonium. and that is how the nagasaki nuclear reaction was setoff. those two american bombs remain the only two nuclear weapons ever been used as weapons in