Submarines of the US
Navy - Page 3
|Each submarine carries 16 Trident II D-5 missiles, which can each carry
up to twelve warheads (i.e. a potential of 192 warheads). However, the British
government announced in 1998 that each submarine would carry only 48 warheads
(halving the limit specified by the previous government), which is an average
of three per missile. However one or two missiles per submarine are probably
armed with fewer warheads for "sub-strategic" use causing others
to be armed with more.
The British-designed warheads are thought to be selectable between 0.3 kt, 5-10 kt and 100 kt; the yields obtained using either the unboosted primary, the boosted primary, or the entire "physics package". The United Kingdom has purchased the rights to 58 missiles under the Polaris Sales Agreement (modifed for Trident) from a jointly maintained "pool". These missiles are fitted with UK-built warheads and are exchanged when requiring maintenance. Under the terms of the agreement the United States does not have any veto on the use of British nuclear weapons.
Table 1 Vanguard class — significant dates
The Trident missile agreement was reached in 1982 as a modification of the Polaris Sales Agreement. At the time it was envisaged the entire project; four submarines, the missiles, new facilites at Coulport and Faslane and a 5% contribution to Trident research and development, would cost £5 billion. The option for a fifth submarine was discussed at the time.
The submarines were built in specially constructed facilites at Vickers Shipbuilding and Engineering Ltd, subsequently GEC Marine (VSEL) and BAE Systems Marine (VSEL), Barrow-in-Furness, Cumbria. The Trident II D-5 achieved an initial operational capability with the U.S. Navy in March 1990. Following launch and commissioning the vessels deployed on Demonstration and Shakedown Operations (DASOs). The major part of this was the test firing of Trident missiles at the United States' SLBM Launch Area, Eastern Test Range, Cape Canaveral, off the coast of Florida (see table above).
In the Strategic Defence Review published in July 1998, the British Government stated that once the Vanguard submarines became fully operational (the fourth and final one, Vengeance, entered service on 27 November 1999), it would "maintain a stockpile of fewer than 200 operationally available warheads". The Stockholm International Peace Research Institute has estimated the figure as 185.
At the same time, the British Government indicated that warheads "required to provide a necessary processing margin and for technical surveillance purposes" were not included in the "fewer than 200" figure. Many estimates for the total number of warheads are around 200; for instance the Natural Resources Defense Council believes that this figure is accurate to within a few tens. The World Almanac suggests the number is between 200 and 300.