Astute Class SSN Submarine

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 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.

Trafalgar class


Essentially an improved Swiftsure class design, the Trafalgar class constitutes the third generation of British SSNs built at the Vickers shipyard in Barrow-in-Fumess. The lead boat, HMS Trafalgar, was launched in 1981 and commissioned into the Royal Navy in March 1983, serving with the Swiftsure class boats at the Devonport naval base. The class total of seven boats also includes HMS Talent, HMS Tireless, HMS Torbay, HMS Trenchant, HMS Triumph and HMS Turbulent.

The major improvements over the Swiftsure class include several features to reduce the underwater radiated noise. These comprise a new reactor system, a pumpjet propulsion system rather than a conventional propeller, and the covering of the pressure hull and outer surfaces with anechoic tiles to give the same type of protection as afforded by the Soviet Clusterguard coating in reducing noise.

The Trafalgar was the first boat to be fitted with the Type 2020 sonar, and was used as the development test platform for the system. According to other reports there has also been a rearrangement of the internal compartments to allow a rationalization and centralization of the operations, sound and ESM/radar rooms. The remaining systems, the armament and the sonars are the same as fitted to the Swiftsure class boats, although a thermal imaging periscope is now carried as part of the search and attack periscope fit, and Type 197 sonar is no longer carried. The fin, like those of the earlier British SSNs, houses an SHF DF antenna, communications antennae, and snort induction, radar and ESM masts. Underwater communications are believed to be conducted via a towed buoy and/of a floating antenna.

HMS TALENT (S92) – Crown copyright

The primary mission of the Trafalgar class submarines all of which remain in service with the Royal Navy, is anti-submarine warfare, with anti-surface ship warfare as a secondary role. The boats can launch the Tomahawk Block IIIC cruise missile. Source

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.

HMS Ambush – Crown copyright

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.

HMS Artful –

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.

HMS Audacious – Vigen’s Weapons Blog

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.

HMS Anson (S123) –

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.

Junior ratings’ mess –

The wardroom –


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.

Royal Navy submarine special forces delivery systems

HMS ASTUTE (S119) – Crown copyright

The Astute class submarines were designed from the outset to be fitted with a Dry Deck Shelter (DDS) which significantly enhances their ability to covertly deliver special forces. Using unclassified public domain sources, here we examine the history, design and operation of the DDS in RN service.

The DDS fitted to the Astute class boats is a cylindrical chamber approximately 13m long by 3m diameter. In UK service it is formally named the Special Forces Payload Bay (SFPB) and was procured under ‘project CHALFONT’, although submariners nickname it “the caravan of death”. The DDS is not a permanent fixture and is designed to be attached or removed from a submarine within a matter of days. The aft section of the sail on the Astute class boats have removable panels. Securing points on the casing, hull penetrations, piping for high-pressure air and electrical supplies are in place ready to receive the DDS. Given the small number of SSNs possessed by the RN, only one boat is likely to be fitted at a time. HMS Astute first deployed with the DDS on an 8-month patrol in 2014 and HMS Artful currently carries the DDS which she first received in late 2016.

The Astute class reputedly have a lock-in/lock-out transfer trunk permanently installed inside the sail that allows diver access to and from the submarine while submerged. When the DDS has fitted, this chamber is mated to the ‘hangar’ which can accommodate either a Swimmer Delivery Vehicle (SDV) or up to 20 divers and their equipment. (The US Navy version also has a hyperbaric decompression chamber forward of the transfer trunk but the UK version does not appear to have this facility.) Source

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).

Greg White

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

iXSea MARINS inertial navigation systems

After an exhaustive assessment, BAE Systems (Submarine Solutions) has chosen iXSea MARINS inertial navigation systems for HMS Audacious, the fourth boat in the UK Royal Navy’s Astute-class, nuclear-powered attack submarine construction programme. HMS Audacious will be equipped with two MARINS units. iXBlue will also supply a third unit for preliminary test work at BAE Systems’ Astute Shore Integration Facility and provide engineering and project management support for the installation of the units on board the submarine. BAE Systems has options on further MARINS units for Astute-class boats five, six and seven.

MARINS was designed by iXSea to meet the growing need of the world’s navies for more accurate and reliable inertial navigation systems and represents the state of the art in strap-down, fibre-optic gyroscope technology. The military-specification unit outputs position, heading, roll, pitch, depth and velocities, and is perfectly silent. Drift is less than 1Nm in 24 hours operating in pure inertial mode, i.e. without GPS input. It is compatible with a wide range of aiding sensors and can be up and running within minutes. Source

Royal Navy’s newest sub test fires torpedo using £50 million UK-made advanced Combat System

The Royal Navy’s latest and most advanced hunter killer submarine, Artful, has test fired her first torpedo using a new UK designed and built command and control system.

The firing tested the BAE Systems designed Common Combat System (CCS) on board, which functions as the digital ‘brain’ of the boat controlling its ‘eyes’, ‘ears’ and ‘nervous system’. Using the torpedo test, the cutting-edge system was able to interpret sonar readings, and then attack a moving target with a practice weapon.

The CCS, completed ahead of time so it was ready for the third rather than fourth Astute submarine, uses the latest technology to collect and process huge amounts of data from sensors such as sonar, providing key information to help inform important Command decisions. The system is so advanced it can even process information fed back from the world-leading Sonar 2076, which allows the Royal Navy to detect and track the quietest of adversaries.

Developed through the Astute Build Programme, the Common Combat System is a collaborative industry effort. Managed through a £50 million contract with BAE Systems, the CCS hosts sonar processing capability developed by Thales UK, and was also worked on by global hardware provider Dell; Poole-based systems designers Aish Technologies; and cloud computing company VMWare, which employs UK workers in Staines-upon-Thames and Milton Keynes.

Installation work is being undertaken by BAE Systems at Barrow-in-Furness and Babcock Marine at HMNB Devonport and HMNB Faslane. In total, CCS is sustaining around 146 jobs across the UK.

The next generation command and control system will be integrated onto every Astute and Vanguard-class submarine currently in service, and fitted to every new Astute class submarine coming into service in the future, ensuring consistency right across the fleet. The system will also be used on board the Royal Navy’s next generation of nuclear submarines. Source

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.

Babcock Int’l Group

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.

HMS ASTUTE (S119) – Crown Copyright

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.

Greg White

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.

Spearfish torpedo

The Spearfish advanced heavy weight torpedo from BAE Systems is effective against submarine and surface threats in oceanic and coastal waters. The 1.85t torpedo is in service with the submarine fleet of the UK Royal Navy.

The Spearfish carries Aluminised PBX explosive warhead of 300kg and is directed towards the target by high-capacity guide wire system and passive and active sonar.

Its power plant is composed of a gas turbine engine using Otto Fuel as a liquid monopropellant, and Hydroxyl Ammonium Perchlorate (HAP) as oxidant. The propulsion system allows the Spearfish to engage targets within 48km at low speed. Source

Type: Torpedo Weight: 1850.0 kg
Length: 5.95 m Span: 0.533 m
Diameter: 0.533 Generation: None
Properties: Search Pattern, Bearing-Only Launch (BOL), Re-Attack Capability
Targets: Surface Vessel, Submarine
Torpedo Seeker – (Spearfish Mod 0) Hull Sonar, Active/Passive
Torpedo Seeker, Active/Passive Shallow Water
Max Range: 3.7 km
Spearfish Mod 0 – (1994) Torpedo
Surface Max: 11.1 km. Subsurface Max: 11.1 km.


Countermeasure technology and sensors

HMS ANSON (S124) –

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.

Thales Sensors Outfit UAP(4)

Type: ESM Altitude Max: 0 m
Range Max: 926 km Altitude Min: 0 m
Range Min: 0 km Generation: Early 1990s
UAP-4 – (Astute) ESM
Role: ELINT w/ OTH Targeting
Max Range: 926 km


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.

Type 2079 [Type 2076 Suite] (Astute)

Type: Hull Sonar, Active/Passive Altitude Max: 0 m
Range Max: 74.1 km Altitude Min: 0 m
Range Min: 0 km Generation: Late 2000s
Type 2079 [Type 2076 Suite] – (Astute) Hull Sonar, Active/Passive
Role: Hull Sonar, Active/Passive Search
Max Range: 74.1 km


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.

CM010 TV/EO optronic masts


Optronic masts are electronic imaging systems and do not penetrate a submarine’s hull, but are contained in the conning tower or ‘fin’. The smaller size of the periscope well allows for more freedom in determining the location of the ship’s control room. With conventional periscopes, the control room had to be placed in the cramped upper deck. A photonics periscope allows the control room to be located on the roomier second deck. Images from the photonics masts are sent via fibre-optics to two workstations and a commander’s control console.

In 1998, the first CM10 optronic mast was sea-trialled on HMS Trenchant and brought about a significant change in the Royal Navy’s above water visual system capabilities. Today, each Astute Class submarine has two Thales CM10 optronic masts, each fitted with a fully integrated ESM/EW sensor package and with TV, thermal imaging or images being remotely controlled and displayed on consoles within the control room.

Today state-of-the-art optronic masts can complete a full 360° sweep of the horizon, looking for potential threats, in only a few seconds, providing high definition images of the battle space to commanders before they are detected by an adversary.

Thales are currently bidding competitively to have their optronic masts procured for the BAE Systems Maritime build of four new Dreadnought nuclear deterrent submarines which will come into service in the 2030s. The company will conduct sea trials of their latest mast in 2018. Source

CM010 TV/EO Component

Type: Visual Altitude Max: 0 m
Range Max: 41.7 km Altitude Min: 0 m
Range Min: 0 km Generation: Visual, 3rd Generation TV Camera (2000s/2010s, CCD)
Properties: Identification Friend or Foe (IFF) [Side Info], Classification [Class Info] / Brilliant Weapon [Automatic Target Aquisition], Continous Tracking Capability [Visual]
CM010 TV/EO Component – (1.5x/24x Zoom) Visual
Role: Visual, Surveillance & Navigation TV Camera
Max Range: 41.7 km

CM010 LLTV Component

Type: Visual Altitude Max: 0 m
Range Max: 41.7 km Altitude Min: 0 m
Range Min: 0 km Generation: LLTV, 3rd Generation (2000s/2010s)
Properties: Identification Friend or Foe (IFF) [Side Info], Classification [Class Info] / Brilliant Weapon [Automatic Target Aquisition], Continous Tracking Capability [Visual], LLTV / NVG / CCD (Night-Capable) / Searchlight [Visual Night-Capable]
CM010 LLTV Component – (2000s/2010s, 1.5x/24x Zoom) Visual
Role: LLTV, Surveillance & Navigation Camera
Max Range: 41.7 km

CM010 IR Component

Type: Infrared Altitude Max: 0 m
Range Max: 41.7 km Altitude Min: 0 m
Range Min: 0 km Generation: Infrared, 3rd Generation Imaging (2000s/2010s, Impr LANTIRN, Litening II/III, ATFLIR)
Properties: Identification Friend or Foe (IFF) [Side Info], Classification [Class Info] / Brilliant Weapon [Automatic Target Aquisition], Continous Tracking Capability [Visual]
CM010 IR Component – (2000s/2010s, 1.5x/12x Zoom) Infrared
Role: Infrared, Surveillance & Navigation Camera
Max Range: 41.7 km

CM010 QLR IR Component 

Type: Infrared Altitude Max: 0 m
Range Max: 27.8 km Altitude Min: 0 m
Range Min: 0 km Generation: Infrared, 3rd Generation Imaging (2000s/2010s, Impr LANTIRN, Litening II/III, ATFLIR)
Properties: Identification Friend or Foe (IFF) [Side Info], Classification [Class Info] / Brilliant Weapon [Automatic Target Aquisition]
CM010 QLR IR Component – (1x/2x Zoom) Infrared
Role: Infrared, Day/Night Spherical Situational Awareness & Fire Control
Max Range: 27.8 km


HMS Ambush

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

3d_molier International

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.

Main material source

Images are from public domain unless otherwise stated

Main image: HMS AMBUSH (S120) –

Revised Dec 31, 2020

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.