After the success achieved with the nuclear device known as “The Gadget” during the first nuclear explosion in history, known as the “Trinity test“, it was time to get something practical out of it all. For this, the construction of a plutonium gun-type fission bomb designated as “Thin man” began, although this must have been canceled for technical problems. Finally it was decided to develop another simpler uranium bomb, but with the same trigger system for the chain reaction. This development ended with the appearance of the “Little Boy” bomb, with which the first nuclear bombardment would be carried out on the city of Hiroshima, Japan.

LITTLE BOY (Mk.1) gallery and more info


Información adicional

Ficha Completa
Country of origin

United States


Los Alamos Laboratory


Nuclear bomb

Entered service


Missile/bomb dimensions, (length x diameter)

3.04 x 0.71 meters

Missile/bomb weight

4,394 kg

Warhead, (explosive charge)

Weight: 64.1 kg – Fissile material: Uranium 235 core – Type: fission gun device

Yield, (maximum)

15 kilotons


1 Little Boy complete bomb + 28 casings + 10 trigger systems + 6 initiator devices