The Nuclear Bomb

A single neutron colliding with the atomic nucleus of a fissionable substance like uranium 235 (or plutonium 239) can cause the nucleus to split, releasing 2 or 3 more neutrons and energy in the forms of extreme heat and lethal radiation. These newly released neutrons collide with other nuclei, releasing more neutrons and more energy. Under proper conditions, this chain reaction spreads and instantaneously releases enormous energy. The atomic bomb is a weapon designed to use that energy to inflict massive destruction.


Type Gun-Barrel Uranium bomb(Nickname Little Boy)
Weight Approx. 4 tons
Explosive power(TNT) Approx. 16.000 tons
Detonation altitude Approx 1.969 feet (600m)
Structure Quantities of uranium 235,         each less than a critical mass,* were placed at two ends of a long, thin cylinder. A chemical explosion propelled the U-235 at one end forcefully into the piece at the other end, instantly creating a critical mass and starting a fission chain reaction. U-235 is present in natural uranium, but only in tiny amounts. This bomb thus required technology to increase that percentage.

*Critical mass: The minimum amount of fissionable material required to sustain a nuclear chain reaction


Type Implosion Plutonium(Nickname Fat man)
Weight Approx. 4.5 tons
Explosive power (TNT) Approx. 21.000 tons
Detonation altitude Approx 1.640 feet(500m)

Quantities of plutonium 239, each less than a critical chemical explosion drove the pieces forcefully toward the center, compressing them instantly into a critical mass and starting the nuclear fission. Pu-239 does not exist naturally. This bomb thus required a reactor capable of creating this element.