W79

The W79 was an American nuclear artillery shell, capable of being fired from any standard 8 inch (203 mm) howitzer e.g. the M115 & M110 howitzer.

The W79 was produced in two models, the "W79 Mod 0" and "W79 Mod 1". Both were a plutonium-based linear-implosion, nuclear weapon.

The "Mod 0" was a variable yield device with three yields, ranging from 100 tons up to 1.1 kiloton and an enhanced-radiation (popularly known as Neutron bomb) mode which could be turned on or off.

The "Mod 1" was fission only, without the enhanced-radiation option, and had a fixed 0.8 kiloton yield (800 tons of TNT). This probably corresponds with the maximum pure-fission yield of the "Mod 0".

Both models were 8 inches (203 mm) in diameter, 44 inches (112 cm) long and weighed 200 pounds (90 kg).

The W79 was produced starting at least as early as 1976 and continuing into 1986. All units were retired from active service by the end of 1992.

Linear-implosion uses a mass of nuclear material which is more than one critical mass at normal pressure and in a spherical configuration. The mass, known as pit, is configured in a lower density non-spherical configuration prior to firing the weapon and then, small to moderate amounts of explosive collapse and slightly reshape the nuclear-material into a supercritical-mass which then undergoes chain-reaction and explodes. Three methods are known to compress and reshape the nuclear-material: 1) collapsing hollow spaces inside the nuclear material; 2) using plutonium-gallium alloy, which is stabilized in the low-density delta-phase at a density of 16.4 (and which collapses to denser alpha-phase under moderate explosive-compression); and 3) shaping an explosive and nuclear material so that the explosive pressure changes a stretched-out, elliptical or rugby-football shape to collapse towards a spherical or more spherical end-shape.

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