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Vanguard Class Ballistic Missile Submarine

Four Vanguard-class SSBNs make up Britain's nuclear deterrent. The Vanguard Class submarine has been purpose-built as a nuclear powered ballistic missile carrier, incorporating a selection of successful design features from other British submarines. In this respect it is unlike its Polaris predecessor, which was adapted from the then existing Valiant Class SSN. At nearly 150 meters in length and over almost 16,000 metric tons, about twice the displacement of the Polaris submarines of the Resolution Class.

Vanguard Class SSBN

The submarines were designed and built by Vickers Shipbuilding and Engineering Limited [VSEL] at Barrow-in-Furness. They are by far the largest submarines ever manufactured in the United Kingdom and the third largest unit in the Royal Navy. A special manufacturing facility, the Devonshire Dock Hall, had to be purpose-built at Barrow for their construction. The Vanguard Class submarines are larger than the Resolution Class mainly because of the need to accommodate the Trident D5 missile. However, the complement of a Vanguard Class boat is smaller - 132 officers and men compared to a Polaris submarine's crew of 149. The Vanguard Class boats include a number of improvements over previous British submarines, including a new design of nuclear propulsion system and a new tactical weapon system for self-defense purposes both before and after missile launch. The 16-tube missile compartment is based on the design of the 24-tube system used by the United States Navy's Ohio Class Trident submarines.

Some fourteen years after the start of the Trident project, the first submarine, HMS Vanguard, entered service on time in December 1994. HMS Victorious repeated that achievement, entering service in December 1995. The third Trident submarine, Vigilant, was commissioned in Barrow on 2 November 1996. In late 1997 HMS Vigilant emerged from the nuclear weapons store at Coulport fully armed with Trident missiles and nuclear warheads.Vigilant test fired two missiles in October 1997, then loaded missiles from 19 November to 3rd December, in which time nuclear warheads were attached to the missiles at Coulport. There was a final inspection on 05 December 1997, then the submarine became operational. The fourth and last UK Trident submarine, the Vengeance, was launched at the Barrow-in-Furness shipyard in Cumbria on 22nd August 1998. The Vengeance was commissioned into the Royal Navy at the GEC Marine (formerly VSEL) shipyard in Barrow-in-Furness, Cumbria on 27 November 1999.

It is too early in the life of the Trident program accurately to assess operating costs but the Government estimates them to be in the order of £200 million per annum over a 30 year in-service life. This estimate encompasses manpower and related costs, refits of the submarines, stores and transport costs, a share of the running costs of shore facilities, an element of the costs of the Atomic Weapons Establishment, in-service support of the submarines and their weapon systems and decommissioning and disposal costs. The latest estimate of the total acquisition cost of the Trident programme is £12.57 billion at 1996-97 economic conditions, over £3.6 billion less in real terms than the original 1982 estimate.

In February 2002, Vanguard arrived at Devonport Naval Base to begin a two year refit including a new reactor core, which was completed in January 2005. The Victorious began refit in January 2005.

Nuclear Warhead Loading

Each Vanguard Class submarine is capable of carrying 192 warheads, but the boats will deploy with much less. Normally, each missile is equipped with 1-3 warheads, depending on its mission.

The Labour Party’s 1998 Strategic Defence Review (SDR) determined that only one of four SSBNs would be on patrol at any given time, and that it would “will carry 48 warheads.” The British government reaffirmed this number to Parliament on July 21, 2005. In December 2006, the government modified this statement by stating that each submarine carried "a maximum of 48 warheads" The 1998 SDR declared that less than 200 warheads were operationally available for the four SSBNs. This statement was modified in December 2006, when the government stated that the number would be reduced to "less than 160." The government has not disclosed the size of its total stockpile, and the statements from 1998 and 2006 imply that additional warheads are stored in a reserve.

Vanguard Class SSBN Profile

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This statement appears to reflect the operational reality of the British SSBN force. The 1998 SDR reduced the number of Trident II D5 missiles to be supplied by the United States from 65 to 58, meaning that there are not enough missiles to fully arm all four SSBNs. This suggests a Royal Navy decision to acquire only enough missiles to arm three boats (48 missiles), with the remaining 10 missiles to be used for spares and test launches. If one assumes that the navy arms each of the 48 missiles with up to three warheads, then a maximum of 144 warheads are required, a number that seems to match the declaration of "less than 160" warheads.

It is important to note that there is not a set of Trident IIs specifically dedicated to British use. Rather Britain draws on a pool of commingled missiles kept in the Strategic Weapons Facility Atlantic at Naval Submarine Base Kings Bay, Georgia. Britain has title to 58 missiles but does not own them; a missile that was deployed on a U.S. sub may later deploy on a British sub, or vice versa.

Another factor influencing the loadout is that Britain assigns its patrolling SSBN a “substrategic mission” to supplement its strategic role. Operationally this probably means that some of the sub’s missiles have a single warhead aimed at targets once covered by WE177 gravity bombs. These warheads could be used to attack regional adversaries (so-called rogue states) that have weapons of mass destruction, a mission that would not require a substantial attack. The substrategic mission may also require smaller warhead yield options. This can be achieved by choosing to detonate a warhead’s unboosted primary, which would produce a yield of 1 kiloton or less, or by choosing to detonate the boosted primary, which would produce a yield of approximately a few kilotons.

The load-out of an SSBN on patrol with strategic and substrategic missions would likely be either 10, 12, or 14 SLBMs loaded with multiple warheads; the remaining missiles would be armed with one warhead each. U.S. Trident IIs can carry up to eight warheads; presumably those missiles on British submarines can do the same. Assuming a limited upload capability, a few spares, and a number of warheads always in maintenance (and therefore not “operationally available”), we conclude that a reasonable estimate of the total stockpile is approximately 200 warheads.

The submarine on patrol operates at reduced alert, with the capability to fire its missiles within days of receiving an authentic launch order (rather than within a few minutes, as during the Cold War). The missiles are held in a “detargeted” mode, meaning that target data would need to be loaded into the guidance system before launch, an operation that takes a few minutes. It could also take the sub some time to get into position to launch a missile. While on patrol, the submarine carries out secondary tasks, including hydrographic data collection and exercises with other vessels. During the past few years, a couple of British subs have visited French ports.

The Future Deterrent

The U.K. government announced on December 4, 2006, that it had decided to replace the Vanguard-class SSBNs with a new class of ballistic missile submarines to begin entering service in 2024.

Vanguard Class SSBN


Hull Number


First Patrol


Vanguard S28 1993 December 1994 Displacement 15,980 metric tons (dived)
Victorious S29 1995 December 1995 Length 149.9 meters
Vigilant S30 1996 June 1998 Beam 12.8 meters
Vengeance S31 November 27, 1999 February 2001 Draught 12 meters
        Complement Two crew of 135
        Armament 16 Trident II D5, torpedoes



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Maintained by Robert Sherman
Originally created by John Pike
Updated Friday, November 05, 1999 8:08:56 AM