Weapons & delivery systems
Atomic Bomb
A nuclear weapon whose energy comes from nuclear fission of uranium-235 or plutonium-239.
Atomic bombs (also called fission bombs) split heavy nuclei to release energy. Yields are typically below 100 kilotons because of inefficiency. The Hiroshima bomb (Little Boy, uranium-235, gun-type) and Nagasaki bomb (Fat Man, plutonium-239, implosion) were both fission weapons.
Related terms
Hydrogen Bomb
A nuclear weapon that derives most of its energy from nuclear fusion of hydrogen isotopes, ignited by a fission primary stage.
Thermonuclear Weapon
Synonym for hydrogen bomb — a nuclear weapon whose primary energy comes from fusion reactions.
Nuclear Fission
The splitting of heavy atomic nuclei (typically uranium-235 or plutonium-239) into lighter fragments, releasing large amounts of energy.
Critical Mass
The minimum amount of fissile material required to sustain a self-propagating nuclear chain reaction.