| W56 | |
|---|---|
 Technicians work on the W56 Mk-11 warhead of an LGM-30F Minuteman II intercontinental ballistic missile. | |
| Type | Nuclear warhead |
| Service history | |
| In service | 1963-1993 |
| Used by | United States |
| Production history | |
| Designer | Lawrence Livermore National Laboratory |
| Designed | 1959 to 1963 |
| Produced | March 1963 to May 1969. |
| No. built | 1000 |
| Specifications | |
| Mass | 600 pounds (270 kg) sans RV |
| Length | 47.3 inches (1,200 mm) sans RV |
| Diameter | 17.4 inches (440 mm) sans RV |
Detonation mechanism | Contact, airburst |
| Blast yield | 1,200 kilotonnes of TNT (5,000 TJ) |
The W56 (originally called the Mark 56) was an American thermonuclear warhead produced starting in 1963 which saw service until 1993, on the Minuteman I and II ICBMs.
The warhead had a yield of 1.2 megatonnes of TNT (5.0 PJ) and a demonstrated yield-to-weight ratio of 4.96 kilotonnes of TNT per kilogram (20.8 petajoules per tonne), very close to the predicted 5.1 kilotonne of TNT/kg (21 PJ/t) achievable in the highest yield to weight weapon ever built, the 25 megatonnes of TNT (100 PJ) B41. However unlike the B41, which was never tested at full yield, the W56 demonstrated its efficiency in the XW-56-X2 Bluestone shot of Operation Dominic in 1962.[1]
Production of the Mod 1 warhead began in March 1963. The Mod 4 warhead began production in May 1967 and finished production in May 1969. 1,000 total were produced, of which 455 were Mod 4 warheads. The warheads were retired between 1991 and 1993,[2][3] and the last W56 warhead was dismantled in June 2006.[4] During dismantlement, one warhead which had high-performance but sensitive polymer-bonded explosive in its explosive lenses is reported to have nearly detonated in 2005 when an unsafe amount of pressure was applied to the explosive while it was being disassembled.[5]
- ^ "Operation Dominic". The Nuclear Weapon Archive: A Guide to Nuclear Weapons. Retrieved 2021-05-23.
- ^ Cite error: The named reference
W56Historywas invoked but never defined (see the help page). - ^ Cite error: The named reference
nukearcwas invoked but never defined (see the help page). - ^ "NNSA Dismantles Entire Stock of W56 Nuclear Weapons". NNSA. Archived from the original on 13 November 2013. Retrieved 13 November 2013.
- ^ "Mishap in dismantling nuclear warhead". UPI.com. 2006-12-15. Archived from the original on 2022-04-02. Retrieved 2017-05-14.