The W68 weighs 367 pounds (166 kg). The warhead's dimensions are not publicly known, however to fit the maximum load of 14 within the roughly 65-inch-diameter (1,700 mm) Poseidon payload fairing, the Mk 3 Reentry Vehicle must be much smaller than other US RVs [which are mostly 22-inch (560 mm) diameter and mostly 72-inch (1,800 mm) long sized].
Production and deployment
A total of 5,250 W68 warheads were produced, the single largest production run of any American nuclear weapon model. It was manufactured starting in June 1970 and ending in June 1975. Each Poseidon missile could carry up to 14 warheads; at the peak deployment, there were 41 US Poseidon submarines with 16 missiles each, for a total of 656 deployed missiles, at a density of about 10 warheads per missile.
Safety issues and later service
Aging of the LX-09 Plastic Bonded Explosive used in the W68      led to decomposition of the explosive, separating the binder and plasticizer, which then caused deterioration of the detonators. This required the whole production run to be retired or remanufactured with LX-10 and LX-10-1 as new explosives from November 1978 through 1983; about 2,000 units were retired starting in 1977 rather than rebuilt.
The remaining 3,200 warheads remained in service longer, with the last units retired in 1991.
- W68 warhead at globalsecurity.org Accessed 2006-05-03
- Warhead Accidents at Banthebomb.org Accessed 2006-05-03
- Explosives section in nuclear weapons FAQ Accessed 2006-05-03
- LLNL explosives accident training web page Accessed 2006-05-03
- Relatives of 3 Killed in Blast At Nuclear Plant Lose Suit from Oct 3, 1981 New York Times, Accessed 2006-05-03