The W42 was an American nuclear warhead developed in 1957.
In December 1957 the Army requested the Atomic Energy Commission to develop a nuclear warhead for the HAWK low- to medium-altitude surface-to-air missile. In July 1958 the military characteristics were approved for the new warhead and the design released. Two months later the requirement for a HAWK with a nuclear warhead was cancelled.
It equipped the AIM-47 Falcon long-range air-to-air missile.
The dimensions of the warhead were 13-14in wide by 18.5in long. It weighed 75-92 pounds and used a proximity fuze.
The project was cancelled in June 1961.