Mark 8 nuclear bomb

The Mark 8 nuclear bomb was an American nuclear bomb, designed in the late 1940s and early 1950s, which was in service from 1952 to 1957.

Description

The Mark 8 was a gun-type nuclear bomb, which rapidly assembles several critical masses of fissile nuclear material by firing a fissile projectile or "bullet" over and around a fissile "target", using a system which closely resembles a medium-sized cannon barrel and propellant.
The Mark 8 was an early earth-penetrating bomb, intended to dig into the earth some distance prior to detonating. According to one government source, the Mark 8 could penetrate of reinforced concrete, of hard sand, of clay, or of hardened armor-plate steel.
The Mark 8 was in diameter across its body and long depending on submodel. It weighed, and had a yield of 25-30 kilotons.
A total of 40 Mark 8 bombs were produced.
The Mark 8 was succeeded by an improved variant, the Mark 11 nuclear bomb. Both the Mark 8 and the Mark 11 could use the same fissile material "gun cores."

Variants

The Mark 8 was considered a cratering warhead for the SSM-N-8 Regulus cruise missile. This W8 variant was cancelled in 1955.
A lighter Mark 8 variant, the Mark 10 nuclear bomb, was developed as a lightweight airburst bomb. The Mark 10 project was cancelled prior to introduction into service, replaced by the much more fissile-material-efficient Mark 12 nuclear bomb implosion design.