Abstract
In July 1998, Britain s Labour government announced several changes to its nuclear force resulting from its Strategic Defence Review:
• Only one British submarine will patrol at any given time, and that boat will carry a reduced load of 48 warheads–half the number the Conservative government had planned.
• The submarine will patrol at a reduced state of alert, its missiles de-targeted. It will be capable of firing its missiles within several days, not minutes as during the Cold War. It will also carry out a range of secondary tasks.
• Britain will maintain fewer than 200 operationally available warheads, a one-third reduction from the Conservative plan.
• Britain will purchase a total of 58 rather than 65 Trident II D-5 missiles from the United States.
When these decisions are fully implemented, the total explosive power of Britain's operationally available weapons will have been reduced by more than 70 percent since the end of the Cold War. The explosive power of each Trident submarine will be one-third less than that of the Chevaline-armed Polaris submarines, the last of which was retired in 1996.
British warheads are designed at Aldermaston, a 670-acre site in Berkshire. Final assembly takes place at Burghfield, a 270-acre site seven miles to the east. In February 1997, the component manufacturing facility at Cardiff closed after 36 years; its functions were transferred to Alder-maston and Burghfield, where about 3,600 people are employed. Warhead maintenance and disassembly takes place at Burghfield, where the last of the Chevaline warheads are scheduled to be dismantled by March 2002.
The Atomic Weapons Establishment (AWE) is now managed by an industrial consortium consisting of Lockheed Martin, Serco Limited, and British Nuclear Fuels, which took over in April 2000, under a 10-year, $3.6 billion contract. On April 1, 1999, the Chief of Defence Logistics assumed overall responsibility for the routine movement of nuclear weapons within Britain. Day-to-day duties are being transferred from Royal Air Force (RAF) personnel to the Ministry of Defence Police, with support from AWE civilians and the Royal Marines. The process will be completed by March 31, 2002.
Each Vanguard-class SSBN carries 16 U.S.-made Trident II (D-5) submarine-launched ballistic missiles (SLBMs). The United States and Britain share a pool of SLBMs kept at the Strategic Weapons Facility Atlantic, Kings Bay Submarine Base, Georgia. Although Britain has title to 58 SLBMs, technically it does not own them. A missile deployed on a U.S. SSBN may at a later date be deployed on a British sub, or vice versa.
British submarines conduct their missile flight tests at the U.S. Eastern Test Range off Florida. The Vanguard conducted two successful Demonstration and Shakedown Operations (DASO) in May and June 1994, launching two missiles. The Victorious fired two missiles during its DASOs in July and August in 1995. In October 1997, the Vigilant also launched two missiles during two DASOs. On September 21, 2000, the Vengeance launched a Trident II D-5 during a DASO exercise.
One of the four subs is normally on patrol. Two others are training in port or in local waters and can be deployed on relatively short notice. The fourth submarine is undergoing repair and maintenance and would require significantly longer preparation for deployment. Each SSBN is protected by one or two hunter-killer submarines (SSNs) while en route to and from its patrol area. In fall 2000, the Royal Navy briefly withdrew all attack subs from service after the Tireless suffered a reactor malfunction. While other British subs were being checked for similar reactor problems, anti-submarine warfare assets (frigates, helicopters, and maritime patrol aircraft) were used to guard and survey transit areas around the shallow waters of the Irish Sea.
British SSBN patrols are believed to be coordinated with the operations of French SSBNs.
British SLBMs are thought to carry a variation of the U.S. W76 warhead designed for Trident I C4 and Trident II D-5 missiles, enclosed in a U.S. Mk-4 re-entry vehicle (RV). Reducing the number of RVs can extend the range of a missile. In its “substrategic” configuration, for example, a missile carrying a single warhead would have a range of more than 6,000 miles.
Several factors will determine the number of warheads in Britain's future stockpile. We assume that Britain will produce only enough warheads for three boatloads of missiles, a practice it followed with Polaris. As stated in the Strategic Defense Review, there will be “fewer than 200 operationally available warheads” in the stockpile, and no more than 48 warheads per SSBN. If all four SSBNs were fully loaded (MIRVed with three warheads) that would total 192.
A further consideration is the “substrategic mission.” A Ministry of Defence official has described a substrategic strike as “the limited and highly selective use of nuclear weapons in a manner that fell demonstrably short of a strategic strike, but with a sufficient level of violence to convince an aggressor who had already miscalculated our resolve and attacked us that he should halt his aggression and withdraw or face the prospect of a devastating strategic strike.”
The substrategic mission began with Victorious and “will become fully robust when Vigilant enters service,” according to the 1996 White Paper. Vigilant achieved operational availability on February 1, 1998. Assuming this policy was implemented, some Trident II SLBMs already have a single warhead and are assigned targets once covered by WE177 gravity bombs. This means that when Vigilant is on patrol, 10, 12, or 14 of its missiles may carry as many as three warheads, while the other two, four, or six may be armed with only one warhead. There is some flexibility in the choice of yield of the Trident warhead. (For instance, choosing to detonate only the unboosted primary could produce a yield of 1 kiloton or less. Or choosing to detonate the boosted primary could produce a yield of a few kilotons.) With dual missions, an SSBN would have approximately 36-44 warheads on board during patrol.
We estimate that the future British stockpile for the SSBN fleet will be around 160 warheads. With an additional 15 percent for spares, we estimate the total stockpile will be approximately 185 warheads. About 15 other warheads are probably in some stage of maintenance and not operationally available.