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HMS Achilles (S125)

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For other ships of the same name, see HMS Achilles.
HMS Ambush long
HMS Ambush, another Astute-class submarine, during sea trials off the coast of Scotland
Career (United Kingdom)
Name: HMS Achilles
Builder: BAE Systems Submarine Solutions
Cost: £1.640B (budget)[1]
Laid down: 14 May 2018[2]
In service: Projected 2028/early 2029[3][4]
Identification: Pennant number: S125
Status: Under construction[5]
General characteristics
Class & type: Astute-class fleet submarine
Displacement:
  • Surfaced: 7,000 to 7,400 t (6,900 to 7,300 long tons; 7,700 to 8,200 short tons)[6][7]
  • Submerged: 7,400 to 7,800 t (7,300 to 7,700 long tons; 8,200 to 8,600 short tons)[6][7]
Length: 97 m (318 ft 3 in)[6][7]
Beam: 11.3 m (37 ft 1 in)[6][7]
Draught: 10 m (32 ft 10 in)[6][7]
Propulsion: Rolls-Royce PWR 2 reactor, MTU 600 kilowatt diesel generators
Speed: 30 kn (56 km/h; 35 mph), submerged[6][7]
Range: Unlimited[8]
Endurance: 90 days[8]
Test depth: Over 300 m (980 ft)
Complement: 98 (capacity for 109)[6]
Sensors and
processing systems:
Armament:
  • 6 × 21 in (533 mm) torpedo tubes with stowage for up to 38 weapons:[9]

    • HMS Achilles (also known as Astute Boat 7) is an Astute-class nuclear-powered fleet submarine under construction for the Royal Navy and the seventh in her class. The boat has had its name changed twice, having previously held the in-work name of Ajax and Agincourt.[10][11]

    The confirmation for the seventh and final Astute-class boat was given in the Strategic Defence and Security Review 2010, although the order was not placed until 2018.[12]

    On 11 December 2012 the British government announced that long-lead items had been ordered for boats 6 and 7.[13]

    On 6 March 2018 the Defence Procurement minister Guto Bebb confirmed that the MoD had gained Treasury approval to sign a contract for Astute Boat 7,[14] after a leaked Navy document had suggested it might not be procured as a cost-saving measure.[15] In May 2018 it was reported that construction of Boat Seven had begun.[16] She had been projected as being ready for service by early 2026, to be based at Faslane (HMNB Clyde).[2][17][4] However, it was subsequently reported that her in-service date slipped substantially and she is now likely to commission in 2028 or early 2029.[18][19]

    Design[]

    Propulsion[]

    Achilles' PWR2 nuclear reactor will not need to be refuelled during the boat's 25-year service. Since the submarine can replenish her air supply and purify water underway and while submerged, she will be able to circumnavigate the planet without resurfacing. The submarine's main limitation will be from the three months supply of food carried for the 98 officers and ratings.

    Weapons[]

    Achilles will have provision for up-to 38 weapons in six 21-inch (533 mm) torpedo tubes.[20] The submarine will be capable of using Tomahawk Block IV land-attack missiles with a range of 1,000 miles (1,600 kilometres)[21] and Spearfish heavyweight torpedoes.

    Name[]

    Originally the vessel had the in-work name HMS Ajax, and then HMS Agincourt. In January 2025, the government announced she would be named HMS Achilles. It was reported that the name change had originally been to avoid offending the French but it later emerged that the change had been requested by the King.[22]

    References[]

    1. ↑ "Ministry of Defence Major Projects Report 2015 and the Equipment Plan 2015 to 2025". 22 October 2015. p. 43. https://www.nao.org.uk/wp-content/uploads/2015/10/Major-Projects-Report-2015-and-the-Equipment-Plan-2015-2025.pdf#page=44. 
    2. ↑ 2.0 2.1 "HMS Agincourt". https://www.royalnavy.mod.uk/our-organisation/the-fighting-arms/submarine-service/fleet-submarines/astute-class/hms-agincourt. 
    3. ↑ Thomas, Richard (30 June 2025). "Introducing the UK’s newest SSN – the Fantasy class". https://www.naval-technology.com/features/introducing-the-uks-newest-ssn-the-fantasy-class/?cf-view. 
    4. ↑ 4.0 4.1 "The Royal Navy's Astute class submarines: Part 1 – development and delivery". 9 January 2023. https://www.navylookout.com/the-royal-navys-astute-class-submarines-part-1-development-and-delivery/. 
    5. ↑ "£300M facilities investment will transform UK submarine building". 13 March 2014. http://www.baesystems.com/en/article/pound300m-facilities-investment-will-transform-uk-submarine-building. 
    6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Bush, Steve (2014). British Warships and Auxiliaries. Maritime Books. pp. 10–11. ISBN 978-1-904459552. 
    7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 "Astute-class attack submarines". http://www.royalnavy.mod.uk/the-equipment/submarines/fleet-submarines/astute-class. 
    8. ↑ 8.0 8.1 "Astute class submarines". http://www.baesystems.com/en/product/astute-class-submarines-enhanced. 
    9. ↑ "UK's most powerful submarine joins the Navy". Ministry of Defence. 27 August 2010. http://www.mod.uk/DefenceInternet/DefenceNews/EquipmentAndLogistics/UksMostPowerfulSubmarineJoinsTheNavy.htm. 
    10. ↑ "Royal Navy nuclear submarines to get £2.5bn boost". BBC News. 14 May 2018. https://www.bbc.co.uk/news/uk-44102308. 
    11. ↑ Allison, George (26 January 2025). "Royal Navy renames final Astute-class submarine". https://ukdefencejournal.org.uk/royal-navy-renames-final-astute-class-submarine/. 
    12. ↑ "Second Astute Class submarine officially named". 22 December 2010. http://www.mod.uk/DefenceInternet/DefenceNews/EquipmentAndLogistics/SecondAstuteClassSubmarineOfficiallyNamed.htm. 
    13. ↑ "UK: BAE Systems Secures $1.92 Bln Submarine Deal". 11 December 2012. http://navaltoday.com/2012/12/11/uk-bae-systems-secures-1-92-bln-submarine-deal/. 
    14. ↑ "Contingent Liability: Written statement - HCWS516". 6 March 2018. https://www.parliament.uk/business/publications/written-questions-answers-statements/written-statement/Commons/2018-03-06/HCWS516/. 
    15. ↑ Chapples, Natalie (6 March 2018). "MoD announces it will sign a contract for Astute boat seven". http://www.nwemail.co.uk/news/barrow/MoD-announces-it-will-sign-a-contract-for-Astute-boat-seven-25bd36a4-20c4-4f71-90fb-c8d7a1696cce-ds. 
    16. ↑ Maundrill, Beth (1 May 2018). "Seventh Astute class submarine build underway". https://www.shephardmedia.com/news/imps-news/seventh-astute-class-submarine-build-underway/. 
    17. ↑ "HMS Audacious". https://www.theyworkforyou.com/wrans/?id=2020-01-30.10350.h&s=c. 
    18. ↑ "Royal Navy submarine, HMS Astute first A-class boat to undergo mid-life refit". 4 July 2025. https://www.navylookout.com/royal-navy-submarine-hms-astute-first-a-class-boat-to-undergo-mid-life-refit/. 
    19. ↑ Thomas, Richard (30 June 2025). "Introducing the UK’s newest SSN – the Fantasy class". https://www.naval-technology.com/features/introducing-the-uks-newest-ssn-the-fantasy-class/?cf-view. 
    20. ↑ "Alien submarine breaks technical barriers". BBC News. 7 May 2007. https://news.bbc.co.uk/2/hi/business/6625477.stm. 
    21. ↑ "United States Navy Fact File: Tomahawk Land Attack Missile". http://www.navy.mil/navydata/fact_display.asp?cid=2200&tid=1300&ct=2. 
    22. ↑ "King involved in 'woke' name change of Agincourt submarine". BBC News. 2025-01-29. https://www.bbc.co.uk/news/articles/c86375y545yo. Retrieved 2025-01-30. 

    External links[]

    • Official website
  • Preceded by: Trafalgar class
  • Followed by: AUKUS class


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