British warheads:
Britain’s Next Nuclear Era
The Warheads
The type of warhead deployed on Britain’s D5 missiles will last at least into the 2020, according to the White Paper. But the U.K. government says it doesn’t yet know whether the warhead can be “refurbished” to last longer, or whether it will be necessary to develop a replacement warhead. The next Parliament will have to make that decision, the government says, an option that of course will be harder to reject if a decision has already been made to build the new submarines.
How British are the warheads on the British SSBN fleet? The Ministry of Defence stated in a fact sheet that the warheads on the D5 missiles were “designed and manufactured in the U.K.” Even so, rumors have persisted for years that the warheads are in fact modified U.S. W76 warheads.
Now a U.S. Department of Energy document – declassified after eight years of processing – directly links the warhead designs on U.S. and U.K. Trident missiles. The document shows that the “U.K. Trident System,” as the British warhead modification is called, is similar enough to the U.S. W76 warhead to make up an integral part of the W76 engineering, design and evaluation schedule (see figure below).
Specifically, the document shows that between 1999 and 2001, work on five of 13 “W76 needs” involved the “U.K. Trident System.” These activities included vibration and point shock models, impulse models, impulse and point shock tests, vibration tests, as well as “TSR [thermostructural response] and Blast Models.”
The activities listed in the chronology are contained in a detailed database that “maps the requirements and capabilities for replacement subsystem and component modeling development, test, and production to the specific organizations tasked with meeting these requirements.”
The “U.K. Trident System” is thought to consist of a 100-kiloton thermonuclear warhead encased in a cone-shaped U.S. Mark-4 reentry vehicle. The W76 is the most numerous warhead (approximately 3,200) in the U.S. stockpile. Built between 1978 and 1988, about a third of the W76s are being modified as the W76-1 (see figure below) and equipped with a new fuze with ground-burst capability to “enable the W76 to take advantage of the higher accuracy of the D5″ against harder targets. Delivery of the first W76-1 is scheduled for 2007 and the last in 2012. The W76 is also the first warhead scheduled to be modified under the proposed Reliable Replacement Warhead program.
