HMS Ajax (S125)

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For other ships with the same name, see HMS Ajax.
United Kingdom
Name: HMS Ajax
Builder: BAE Systems Submarine Solutions
Cost: £1,640m (budget)[1]
In service: 2024 (planned)[2]
Homeport: Faslane
Identification: Pennant number: S125
Status: Confirmed, steel cut[3]
Badge: HMS Ajax crest.jpg
General characteristics
Class and type: Astute-class fleet submarine
  • Surfaced: 7,000 to 7,400 t (7,300 long tons; 8,200 short tons)[4][5]
  • Submerged: 7,400 to 7,800 t (7,700 long tons; 8,600 short tons)[4][5]
Length: 97 m (318 ft 3 in)[4][5]
Beam: 11.3 m (37 ft 1 in)[4][5]
Draught: 10 m (32 ft 10 in)[4][5]
Propulsion: Rolls-Royce PWR 2 reactor, MTU 600 kilowatt diesel generators
Speed: 30 kn (56 km/h; 35 mph), submerged[4][5]
Range: Unlimited[6]
Endurance: 90 days[6]
Test depth: Over 300 m (984 ft 3 in)
Complement: 98 (capacity for 109)[4]
Sensors and
processing systems:

HMS Ajax (S125) (also known as "Astute-class Boat 7") is a proposed Astute-class nuclear-powered fleet submarine of the Royal Navy and will be the seventh in her class. She was to have been the ninth vessel of the Royal Navy to bear the name HMS Ajax, after the Greek hero Ajax; however while some previous official and unofficial sources state her name as "Ajax",[8] others state she is still yet to be officially named, referring to her simply as "Astute boat 7".[9][10]

The confirmation for the seventh and final Astute-class boat was given in the Strategic Defence and Security Review of October 2010, although an order has yet to be placed.[11] On 11 December 2012 the British government announced that long-lead items had been ordered for boats 6 and 7.[12]



A confusing press release suggested that Ajax would have the same PWR3 nuclear reactor as the Successor-class SSBNs[13] but in October 2012 it was confirmed that she would have a PWR2 like the rest of the Astute class.[14] Ajax's 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.


Ajax will have provision for up-to 38 weapons in six 21-inch (533 mm) torpedo tubes.[15] The submarine will be capable of using Tomahawk Block IV land-attack missiles with a range of 1,000 miles (1,600 kilometres)[16] and Spearfish heavyweight torpedoes.


  1. ^ "Ministry of Defence Major Projects Report 2015 and the Equipment Plan 2015 to 2025" (pdf). National Audit Office. 22 October 2015. p. 43. 
  2. ^ "House of Commons Written Answers c45W". UK Parliament. 3 September 2012. Retrieved 9 July 2016. 
  3. ^ "£300M facilities investment will transform UK submarine building". BAE Systems, 13 March 2014. Retrieved 26 July 2016. 
  4. ^ a b c d e f g Bush, Steve (2014). British Warships and Auxiliaries. Maritime Books. pp. 10–11. ISBN 1904459552. 
  5. ^ a b c d e f "Astute-class attack submarines". Royal Navy. Retrieved 27 July 2016. 
  6. ^ a b "BAE Systems - Astute class submarines". BAE Systems. Retrieved 25 July 2016. 
  7. ^ "UK's most powerful submarine joins the Navy". Ministry of Defence. 27 August 2010. Retrieved 11 April 2011. 
  8. ^ "Astutle class". Retrieved 7 April 2016. 
  9. ^ "Astute class submarines". BAE Systems. Retrieved 20 March 2016. 
  10. ^ "Royal welcome to newest submariners". Royal Navy. 11 July 2016. Retrieved 19 July 2016. 
  11. ^ "Second Astute Class submarine officially named". UK Ministry of Defence. 22 December 2010. Retrieved 20 March 2016. 
  12. ^ "UK: BAE Systems Secures $ 1.92 Bln Submarine Deal". 11 December 2012. Retrieved 20 March 2016. 
  13. ^ "Royal Navy submarine contract awarded". UK Ministry of Defence. 18 June 2012. Retrieved 20 March 2016. 
  14. ^ "House of Commons - Written Answers Column 311W". Hansard. UK Parliament. 17 October 2012. Retrieved 20 March 2016. 
  15. ^ "Alien submarine breaks technical barriers". BBC News. 7 May 2007. Retrieved 20 March 2016. 
  16. ^ "United States Navy Fact File: Tomahawk Land Attack Missile". US Navy. Retrieved 27 July 2016.