2. Status of Trident
2.1 - Trident submarines, missiles and warheads
2.2 - Comparison with nuclear submarine force levels
during the Cold War
2.1 Trident submarines, missiles and warheads
Since April 1998 all British nuclear weapons have been based in Scotland. Trident submarines operate from Faslane and the adjacent Coulport nuclear depot. The submarines are:
HMS Vanguard
Armed with 48 warheads, carried out its first patrol in December 1994,
due to go into Devonport Dockyard for a refit in 2002
HMS Victorious
Armed with 48 warheads, carried out its first patrol in January 1996
HMS Vigilant
Armed with 48 warheads, carried out its first patrol in June 1998
HMS Vengeance
Launched in September 1998, due to be operational in 2001.
There are 42 missiles deployed on submarines.12 There are probably 14 missiles on each of the 3 submarines in service. The total number of missiles is not expected to increase when HMS Vengeance becomes operational.
Each missile can carry several warheads. George Robertson has said that "All three Trident submarines normally in the operational cycle will have 48 warheads loaded".13 This means that there are a total of 144 nuclear warheads deployed.
The total number of warheads deployed at sea can be increased at any time from 144 to at least 180. The Defence Secretary has said that spare warheads are kept to "provide potential to deploy additional weapons should that ever become necessary." 14
Mr Robertson has made it clear that no Trident warheads would be decommissioned as a result of the Defence Review.15 He has also said that new warheads will be built in future to replace some of those currently in service.
Each warhead has a yield of around 100 kilotons, which is around 8 times the power of the bomb which destroyed the city of Hiroshima. The total yield of all the warheads deployed on submarines based in Scotland is around 14.4 megatons, which is equivalent to over 1000 Hiroshima bombs.
Most missiles probably carry 4 warheads. A small number of missiles are assigned to a "sub-strategic" role and each carry one warhead. It is not clear whether these warheads have the same yield as the others.
2.2 Comparison with nuclear submarine force levels during the Cold War
Since 1968 Britain has had one nuclear armed submarine on patrol at all times. The Defence Review makes it clear that this will continue. With Polaris there was always one fully armed submarine in reserve and sometimes two in reserve. This will also continue with Trident.
There are substantially more nuclear warheads deployed on submarines today than there were in the early 1990s:
In 1992 there were only 64 Polaris warheads deployed. 16 In January 1997 there were 120 Trident warheads deployed. This rose to 180 later in 1997and declined to 144 following the Defence Review in July 1998. This is illustrated in Chart 1.
The number of warheads on each submarine since Polaris entered service is indicated below:
1968 - 1982
Polaris submarines with 48 Polaris warheads per submarine
1982 - 1996
Polaris submarines with 32 Chevaline warheads per submarine
17
1998 onwards
Trident submarines with 48 Trident warheads per submarine
The Defence Review states that the total yield of all warheads on one Trident submarine today will be one third less than the total yield of all warheads carried on a Polaris submarine. However the Trident warheads are far more accurate and can be targeted independently. The House of Commons Defence Committee described the move from Polaris to Trident as "a significant enhancement of the UKs nuclear capability", in the light of the increased accuracy of the missiles, their longer range and greater sophistication. 18
Until April 1998 Britain also had a number of nuclear bombs which could be dropped from aircraft based in England and Germany. These have now all been withdrawn from service. While this has resulted in a reduction in the total numbers of nuclear weapons, it has also meant that all British nuclear weapons are now based on the Clyde.
Notes
12. Vanguard collected 16 missiles, Victorious 12 and Vigilant 14. Hansard 27 Nov 1997
13. Hansard 28 Jul 1998
14. Hansard 9 Nov 1998. There were 60 warheads deployed on each submarine until Jul 1998, with a total of 180 deployed from when Vigilant became operational in Nov 1997. Following the Defence Review 12 warheads were removed from each submarine. Hansard 16 Jul 1998. The Defence Review said that the total number of operationally available warheads would be less than 200, giving a maximum of 56 in storage. The primary reason these warheads are kept is probably in anticipation of an increase in the effectiveness of Russian ABM defences. The current state of the Russian economy indicates that a steady decline in ABM capability is more likely. In addition to these operational warheads there are more which are kept as a processing margin and others which are undergoing surveillance. Including these, the total stockpile may be slightly higher than 200.
15. "we do not need to decommission any warheads to implement the Strategic Defence Review changes. Adjustments are being made to future warhead production ... " George Robertson, Hansard 16 Jul 1998.
16. From April 1992 to June 1993 and again from October to December 1994 there were only two Polaris submarines armed. HMS Revenge was decommissioned before HMS Renown was operational in 1992/3 and HMS Resolution was decommissioned before HMS Vanguard was operational in 1994.
17. Strategic Defence Review (SDR), MoD, Jul 1998, Supporting Essay 5, para 10.
18. Progress of the Trident Programme, Defence Committee 2nd Report, May 1994, p xiv