The Royal Navy’s Astute Class submarine is a nuclear-powered attack submarine, which will replace the five Swiftsure Class submarines, launched between 1973 and 1977 and approaching the end of their operational life.

The initial order quantity was three, but the UK Ministry of Defence (MoD) ordered an additional four, meaning seven submarines will be built as part of the Astute Class. The performance specification of the Astute is an extension of the performance of the Trafalgar Class batch 1 fleet of the Royal Navy’s Second Submarine Squadron based at Devonport.

The Trafalgar batch 1 submarines are to be decommissioned by 2022, beginning with HMS Trafalgar, which was decommissioned in December 2009. The Astute Class submarines will be based at Faslane in Scotland.

Royal Navy’s attack submarine development history

BAE Systems Astute Class is the prime contractor for the project and the submarines are being built at the BAE Systems Marine Barrow shipyard. The first three Astute ships were named HMS Astute (S119), HMS Ambush (S120) and HMS Artful (S121).

The fourth submarine was named HMS Audacious (S122). The fifth Astute Class submarine was named Anson (S123) in September 2011. The sixth and seventh are named Agamemnon (S124) and Agincourt (S125) respectively.

The keel for the first submarine, HMS Astute, was laid in January 2001. It was launched on 8 June 2007. In October 2007, HMS Astute made the first dive for an underwater systems test at the ‘dive hole’ in Devonshire Dock, Barrow. In October, the vessel also successfully carried out first firing trials from its torpedo tubes. HMS Astute was commissioned in August 2010.

The keel of HMS Ambush was laid in October 2003. It was launched in December 2010. Ambush made its first voyage in January 2011. The initial dive test of the Ambush was completed in September 2011 and it was commissioned in March 2013. The HMS Astute and HMS Ambush submarines were handed over to the Royal Navy in July 2013.

The keel of HMS Artful was laid in March 2005. The submarine was launched in May 2014 and performed its maiden dive in October 2014. It was inducted into the Royal Navy in March 2016.

In May 2007, the UK MoD awarded BAE Systems a contract to build a fourth Astute Class submarine, HMS Audacious (S122). The keel of Audacious was laid in March 2009.

In December 2012, BAE Systems received a £1.2bn ($1.9bn) contract from the UK MoD for the design, construction, test and commissioning programme of Audacious. The submarine was launched in April 2017 and made its first dive in January 2018. It sailed from BAE’s Barrow-in-Furness site for a home base in April 2020.

The fifth and sixth Astute Class submarines, Anson (S123) and Agamemnon (S124), were ordered in March 2010. The keel for Anson was laid in October 2011, while that of Agamemnon was laid in July 2013.

BAE Systems received a £1.4bn ($1.7bn) contract for the construction of HMS Agamemnon in April 2017 followed by a £1.5bn ($2.03bn) contract for Agincourt in May 2018. The final three Astute-class submarines are at various stages of construction as of April 2020.

Command and control systems on Astute Class submarines

An astute combat management system (ACMS) is being supplied by BAE Systems Insyte (formerly Alenia Marconi Systems) and is a development of the submarine command system (SMCS) currently in service in all classes of UK submarines.

ACMS receives data from the sonars and other sensors and, through advanced algorithms and data handling, displays real-time images on the command consoles. Factory acceptance of the operational software was received from the Astute Prime Contract Office in July 2002.

EADS Defence and Security Systems and EADS Hagenuk Marinekommunikation were awarded the contract to provide the external communications systems for the Astute in August 2005. Strachan and Henshaw will provide the weapon-handling and launch system (WHLS).

Northrop Grumman Sperry Marine was selected in March 2008 to provide the platform management system for the fourth of class, HMS Audacious.

Astute Class Tomahawk missiles and torpedoes

Astute is equipped with the Tomahawk Block IV (tactical tomahawk) cruise missile from Raytheon fired from the 533mm torpedo tubes.

Tomahawk is equipped with the TERCOM terrain contour mapping-assisted inertial navigation system. The terrain contour mapping for use over land combines on-board radar altimeter measurements with terrain mapping data installed in the missile. Block II added digital scene matching area correlation (DSMAC) guidance.

Block III improvements include an improved propulsion system and Navstar global positioning system (GPS) guidance capability. The GPS provides location and velocity data of the missile for precision targeting.

Tomahawk has a range of up to 1,000mi and a maximum velocity of 550mph. Block IV includes a two-way satellite link that allows reprogramming of the missile in flight and transmission of battle damage indication (BDI) imagery. Tomahawk Land Attack Missile (TLAM) Block IV entered service with the British Royal Navy in April 2008 on board Trafalgar batch I submarine HMS Torbay.

Astute has six 533mm torpedo tubes and is equipped with Spearfish torpedoes and mines. There is a capacity for a total of 36 torpedoes and missiles.

The Spearfish torpedo from BAE Systems is wire-guided with an active / passive homing head. The range is 65km at 60k. Spearfish is fitted with a directed-energy warhead.

Countermeasure technology and sensors

The countermeasures suite includes decoys and electronic support measures (ESM). The ESM system is the Thales Sensors Outfit UAP(4). Outfit UAP(4) has two multifunction antenna arrays, which are mounted on the two non-hull penetrating optronics masts from Thales (formerly Pilkington) Optronics and McTaggart Scott.

"Astute is equipped with the Tomahawk Block IV (tactical tomahawk) cruise missile from Raytheon."

Astute Class submarines are fitted with the Royal Navy’s new Eddystone Communications band Electronic Support Measures (CESM) system, also fitted to the Trafalgar Class submarines. The Eddystone system was developed by DML of Devonport UK with Argon ST of the US.

It provides advanced communications, signal intercept, recognition, direction-finding and monitoring capabilities. Sea trials of the system were completed in December 2007.

The submarines are fitted with I-band navigation radars. The sonar is the Thales Underwater Systems (formerly Thomson Marconi Sonar) 2076 integrated passive / active search and attack sonar suite with a bow, intercept, flank and towed arrays. Sonar 2076 has so far been fitted to Trafalgar Class submarines Torbay, Trenchant and Talent, which entered service in February 2003. Astute is fitted with the latest version of the Thales S2076 integrated sonar suite.

Atlas Hydrographic provided the DESO 25 high-precision echosounder, which is fitted on the Astute. DESO 25 is capable of precise depth measurements down to 10,000m.

Astute has two non-hull-penetrating CM010 optronic masts developed by Thales Optronics. McTaggart Scott supplied the masts. The CM010 mast includes thermal imaging, low-light TV and colour CCD TV sensors.

Raytheon Systems was contracted to provide the Successor IFF (identification friend or foe) naval transponder system for the Astute Class.

Propulsion and performance of the UK’s nuclear submarines

The nuclear power is provided by the Rolls-Royce PWR 2 pressurised water reactor. The long-life core fitted on the PWR 2 means refuelling will not be necessary for the service life of the submarine.

The other main items of machinery are two Alstom turbines and a single shaft with a Rolls-Royce pump-jet propulsor, consisting of moving rotor blades within a fixed duct.

There are two diesel alternators, one emergency drive motor and one auxiliary retractable propeller. CAE Electronics provided the digital, integrated controls and instrumentation system for steering, diving, depth control and platform management.

The PWR 2 second-generation nuclear reactor was developed for the Vanguard Class Trident submarines. Current generations of PWR would enable submarines to circumnavigate the world approximately 20 times, while the latest development of PWR would enable circumnavigation 40 times without refuelling.

The major equipment components in the development of PWR 2 were the reactor pressure vessels from Babcock Energy, main coolant pumps from GEC and from Weir. It also included protection and control instrumentation from Siemens Plessey and Thorn Automation.

Related Projects