The W59 was an American thermonuclear warhead used on some Minuteman I ICBM missiles from 1962-1969, and planned to be used on the cancelled GAM-87 Skybolt air-launched ballistic missile. The W59 was 16.3 inches in diameter[citation needed] and 47.8 inches long, and it weighed 550 pounds. It had a design yield of 1 megaton. A total of 150 W59 warheads were produced during its lifetime. The W59 was one of five nuclear weapon designs identified by researcher Chuck Hansen as using the common design Tsetse primary or first fission bomb stage.