W15

W15 may refer to:

Mark 15 nuclear bomb

The Mark 15 nuclear bomb, or Mk-15, was a 1950s American thermonuclear bomb, the first relatively lightweight (7,600 lb / 3450 kg) thermonuclear bomb created by the United States.

The Mark 15 was first produced in 1955, and a total of 1,200 units were made before production ended in 1957. The Mark 15 design was in service from 1955 to 1965.

There were three production variants of the Mark 15 bomb, the Mod 1, Mod 2, and Mod 3.

Transitional design

The Mark 15 is widely described as a transitional design between fission and thermonuclear weapons. The Mark 15 was a staged weapon (see Teller-Ulam design), using radiation implosion from a fission nuclear primary (Cobra) to implode a secondary stage. Unlike most modern thermonuclear bombs, the Mark 15 used a secondary which was primarily HEU (highly enriched uranium), which generated most of its energy from nuclear fission reactions once the primary imploded it. There was a thermonuclear core which underwent fusion reactions, but most of the energy came from the HEU fissioning. The HEU fission was enhanced by fusion stage neutrons, but would have generated a very significant fission yield by itself.