SSBN Vanguard Class Ballistic Missile Submarine, United Kingdom

The Vanguard submarines were built by Vickers Shipbuilding and Engineering Limited (now BAE Systems Marine) at Barrow-in-Furness. They are the largest submarines manufactured in the UK, displacing 15,900t submerged, twice the displacement of the Resolution class Polaris submarines which they replaced.

The first of class, HMS Vanguard, was commissioned in 1993, HMS Victorious in 1995, HMS Vigilant in 1996 and HMS Vengeance in 1999. The Vanguard submarines are based at the Royal Naval Base at Faslane in Scotland.

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

Following sea trials, which included test launching of Trident II D5 ballistic missiles, the vessel has returned to the fleet. A new dry dock was completed in 2001 for the refit of Vanguard and other RN nuclear-powered submarines. HMS Victorious began refit in January 2005, which was completed in July 2008. Following sea trials she is to return to the fleet in October 2008 and operational service in 2009.

Missiles

The Vanguard has the capacity to carry 16 Trident missiles. The Trident II or D5 missile (designated UGM-133A) is a strategic submarine-launched ballistic missile (SLBM) manufactured by Lockheed Martin Missiles and Space. The missile carries a number of multiple independently targeted re-entry vehicles (MIRVs), each armed with a yield of 100kt to 120kt.

The Trident II missile can carry up to 12 MIRVs but START I treaty agreements limit this to eight. D5 missiles for the Vanguard Class will carry a maximum of four warheads and, in 1999, it was announced that each vessel would carry a maximum of 48 warheads.

Trident II is a three-stage solid propellant missile with supersonic speed. Weight is 59,000kg. The US Navy gives the range of the D5 as 'greater than 7,360km' but this could be up to 12,000km, depending on the payload mix.

The accuracy of strike on the target is given by the Circle of Equal Probability (CEP) value, which is the radius of the circle within which half the strikes will impact. The Mark 6 guidance system on Trident II is a star-sight aided inertial guidance system, which gives a CEP of 120m. The missile is ejected from the submarine by high-pressure gas. When it reaches the surface the first rocket stage fires automatically. The missile's inertial guidance system calculates flight behaviour and guidance.

After the third rocket motor has separated, the warhead carrier takes a star-sighting to confirm position and manoeuvres to the point at which the warheads can be released to freefall onto the target.

Torpedoes

Vanguard is fitted with four 533mm torpedo tubes and carries the Spearfish torpedo supplied by BAE Systems. Spearfish is a heavyweight wire-guided torpedo with both active and passive homing.

It has a speed of 102km/h (55kt) and range of 54km (30nm) at low speed, 26km (12.5nm) at high speed. Length is 7m (23ft), diameter is 533mm (21in) and weight is 1,850kg (4,075lb), with a 300kg (660lb) warhead.

Electronic warfare

The submarine is fitted with two SSE Mark 10 launchers for deployment of Type 2066 and 2071 decoys. The submarine's electronic support measures (ESM) intercept system is the UAP Mark 3 supplied by Thales Defence.

Sensors

Vanguard is equipped with the Thales Underwater Systems Type 2054 composite sonar system. Type 2054 is a multi-mode multi-frequency suite, which includes the 2046, 2043 and 2082 sonar systems. In September 2006, Lockheed Martin UK was awarded a contract to upgrade the Type 2054 sonar systems.

The upgrade will include open architecture processing using COTS (Commercial Off The Shelf) technology, based on the ARCI (Acoustic Rapid COTS Insertion) model that has been in service with the US Navy since 1998. The upgraded system will enter service from 2009.

The Vanguard's towed sonar array is the Type 2046, which provides passive search capability and operates at very low frequency. The Type 2043 is the hull-mounted active and passive mode search sonar and the Type 2082 sonar provides passive intercept and ranging capability.

The submarine is fitted with the CK51 search periscope and the CH91 attack periscope from Thales (formerly Pilkington) Optronics. These periscopes include TV camera and thermal imager as well as optical channel. All above water sensors are combined into self-protection masts in the submarine's fin.

The submarine's navigation radar is the Type 1007 I-band radar supplied by Kelvin Hughes.

Propulsion

The Vanguard class submarine's main nuclear powered propulsion system is based on the second-generation Rolls-Royce PWR 2, which was developed specifically for the Vanguard Class. Current generations of PWR allow submarines to circumnavigate the world about 20 times, whereas the latest development of PWR would allow circumnavigation 40 times without refuelling.

The other main items of machinery are two GEC turbines, and a single shaft with a pump jet propulsor. There are two Paxman diesel alternators, and two turbo generators from WH Allen. The propulsion system provides a maximum submerged speed of 25 knots.