Editing Astute-class submarine (section)

===Propulsion and general specifications===
The boats of the ''Astute'' class are powered by a Rolls-Royce [[Rolls-Royce PWR#PWR2|PWR2]] (Core H) (a [[pressurised water reactor]]) and fitted with a [[pump-jet]] propulsor. The PWR2 reactor, which was developed for the ''Vanguard''-class ballistic missile submarines, has a 25-year lifespan without the need for refuelling.<ref name="tna3b">{{cite web|url=https://rina.org.uk/publications/warship-technology/project-aukus-achieving-critical-mass-scientifically-and-politically/|title=Achieving Critical Mass with Highly Enriched Uranium 2023|date=26 July 2023|access-date=26 July 2023|publisher=[[Royal Institution of Naval Architects]] by [[Dr MJ Cianni]]|archive-date=26 July 2023|archive-url=https://web.archive.org/web/20230726080646/https://rina.org.uk/publications/warship-technology/project-aukus-achieving-critical-mass-scientifically-and-politically/|url-status=live}}</ref><ref name="BAEAstute2016"/> As a result, the new submarines are about 30 per cent larger than previous British fleet submarines, which were powered by smaller-diameter reactors. Like all Royal Navy submarines, the bridge fin of the ''Astute''-class boats is specially reinforced to allow surfacing through ice caps. These submarines can also be fitted with a [[dry deck shelter]], which allows special forces (e.g. [[Special Boat Service|SBS]]) to deploy whilst the submarine is submerged.<ref>{{cite web|url=http://www.rusi.org/downloads/assets/Willet.pdf |title=Dr Lee Willett, The ''Astute''-Class Submarine, Capabilities and Challenges, RUSI (2004) |access-date=7 November 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110928105319/http://www.rusi.org/downloads/assets/Willet.pdf |archive-date=28 September 2011 }}</ref> More than 39,000 [[Anechoic tile|acoustic tiles]] mask the vessel's sonar signature, part of the acoustic qualities that the ''Astute'' class has over any other submarine previously operated by the Royal Navy.<ref>{{cite web |url=http://www.shippingtimes.co.uk/item577_astute.htm |title=Countdown to launch of first ''Astute'' submarine at Barrow shipyard |publisher=Shippingtimes.co.uk |access-date=7 November 2011 |archive-date=24 July 2011 |archive-url=https://web.archive.org/web/20110724093014/http://www.shippingtimes.co.uk/item577_astute.htm |url-status=dead }}</ref>

A 2009 safety assessment by the Defence Nuclear Safety Regulator concluded that PWR2 reactor safety was significantly short of good practice in two important areas: [[loss-of-coolant accident]] and control of submarine depth following emergency reactor shutdown.<ref>{{Citation |chapter-url=http://robedwards.typepad.com/files/declassified-report-to-mod-defence-board.pdf |title=Successor Submaring Project - Update |chapter=Annex B: Successor SSBN - Safety Regulator's advice on the selection of the propulsion plant in support of the future deterrent (4 November 2009) |page=21 |publisher=Ministry of Defence |date=24 November 2009 |id=EC-14-02-02-01-14 / Annex B: DNSR/22/11/2 |access-date=28 March 2011 |archive-date=17 April 2011 |archive-url=https://web.archive.org/web/20110417133948/http://robedwards.typepad.com/files/declassified-report-to-mod-defence-board.pdf |url-status=live }}</ref> The regulator concluded that PWR2 was "potentially vulnerable to a structural failure of the primary circuit", which is a failure mode with significant safety hazards to crew and the public.<ref name="dm-20110518">{{Cite news |url=http://www.defencemanagement.com/news_story.asp?id=16337 |title=PWR3 Reactor chosen for Trident |publisher=defencemanagement.com |date=18 May 2011 |archive-url=https://web.archive.org/web/20110722100732/http://www.defencemanagement.com/news_story.asp?id=16337 |archive-date=22 July 2011}}</ref> Operational procedures have been amended to minimise these risks.<ref>{{Cite news |url=http://www.mod.uk/DefenceInternet/DefenceNews/EquipmentAndLogistics/CsaSafetyParamountForRnNuclearSubmarineReactors.htm |title=CSA: Safety paramount for RN nuclear submarine reactors |work=Defence News |publisher=Ministry of Defence |date=9 June 2011 |access-date=17 June 2011 |archive-date=23 June 2011 |archive-url=https://web.archive.org/web/20110623152331/http://www.mod.uk/DefenceInternet/DefenceNews/EquipmentAndLogistics/CsaSafetyParamountForRnNuclearSubmarineReactors.htm |url-status=live }}</ref>

''Astute'' is the second Royal Navy submarine class, after the ''Vanguard'' class, to have a bunk for each member of the ship's company,<ref>{{Cite web |url=http://production.investis.com/astute/media/press/2007-06-08a/ |title=''Astute'' Fascinating Facts |access-date=10 December 2012 |archive-date=21 July 2013 |archive-url=https://web.archive.org/web/20130721140936/http://production.investis.com/astute/media/press/2007-06-08a |url-status=live }}</ref> ending the practice of '[[Hot racking|hot bunking]]', whereby two sailors on opposite watches shared the same bunk at different times. However, they have less mess-deck space than the {{sclass|Valiant|submarine}}s built 45 years earlier<ref>{{Cite web |url=http://www.whatdotheyknow.com/request/52005/response/144718/attach/5/Pdf%20DNP%20HR%20Study%20Redacted%202.pdf |title=Defence Nuclear Programme Human Resource Study |publisher=Ministry of Defence |date=1 July 2009 |id=Defence Board (09)33 |access-date=16 April 2011 |archive-date=8 October 2012 |archive-url=https://web.archive.org/web/20121008181348/http://www.whatdotheyknow.com/request/52005/response/144718/attach/5/Pdf%20DNP%20HR%20Study%20Redacted%202.pdf |url-status=live }}</ref> and a Defence Board audit recognised mistakes had been made on accommodation standards and quality of life issues.<ref>{{Cite web |url=http://www.whatdotheyknow.com/request/52005/response/144718/attach/6/Pdf%20DOC%20Audit%20Redacted.pdf |title=Defence Nuclear Programme Human Resources Study - An Audit by Defence Operational Capability |publisher=Ministry of Defence |date=1 July 2010 |id=Defence Board (10)XX |accessdate=16 April 2011 |quote=Recommendation ... on-board accommodation standards and quality of life issues are thoroughly addressed in order to avoid the mistakes made with the ''Astute'' class. |archive-date=8 October 2012 |archive-url=https://web.archive.org/web/20121008181405/http://www.whatdotheyknow.com/request/52005/response/144718/attach/6/Pdf%20DOC%20Audit%20Redacted.pdf |url-status=live }}</ref> Since it is nuclear powered, the boat has theoretically unlimited endurance, though in practice it is limited to 90 days at sea based on food carried (including 18,000 sausages and 4,200 [[Weetabix]]) and crew endurance.<ref name="BAEAstute2016"/>

In 2012, during the joint exercise Fellowship, ''Astute'' performed simulated battles with the latest United States Navy {{sclass|Virginia|submarine|1}}, {{USS|New Mexico|SSN-779|6}}. Royal Navy Commander Iain Breckenridge was quoted, "Our sonar is fantastic and I have never before experienced holding a submarine at the range we were holding USS ''New Mexico''. The Americans were utterly taken aback, blown away with what they were seeing".<ref>{{cite web|url=https://www.gov.uk/government/news/hms-astute-arrives-home-from-us-sea-trials--2|title=HMS Astute arrives home from US sea trials - Announcements - GOV.UK|access-date=25 July 2016|archive-date=18 September 2016|archive-url=https://web.archive.org/web/20160918032321/https://www.gov.uk/government/news/hms-astute-arrives-home-from-us-sea-trials--2|url-status=live}}</ref>

The ''Astute'' class are designed to achieve a top speed of {{convert|29|-|30|kn|km/h}}, but it was reported in 2012 that this speed could not be reached in trials due to a mismatch between the reactor and the turbine.<ref name="guardian-20121115b">{{cite news |url=https://www.theguardian.com/uk/2012/nov/15/hms-astute-submarine-slow-leaky-rusty |title=Slow, leaky, rusty: Britain's 10bn submarine beset by design flaws |author=Nick Hopkins |newspaper=The Guardian |date=15 November 2012 |access-date=20 November 2012 |location=London |archive-date=31 October 2013 |archive-url=https://web.archive.org/web/20131031121357/http://www.theguardian.com/uk/2012/nov/15/hms-astute-submarine-slow-leaky-rusty |url-status=live }}</ref> However, in January 2015, the [[National Audit Office (United Kingdom)|National Audit Office]] confirmed that demonstration of the top speed requirement (or Key Performance Measure (KPM)) for the ''Astute'' class was successful.<ref name="NAO2014">{{cite book|title=Major Projects Report 2014 and the Equipment Plan 2014 to 2024: Appendices and project summary sheets|date=13 January 2015|publisher=National Audit Office|page=45|url=https://www.nao.org.uk/wp-content/uploads/2015/01/Major-projects-report-2014-appendices-and-project-summary-sheets.pdf|access-date=8 August 2016|archive-date=6 August 2016|archive-url=https://web.archive.org/web/20160806031421/https://www.nao.org.uk/wp-content/uploads/2015/01/Major-projects-report-2014-appendices-and-project-summary-sheets.pdf|url-status=live}}</ref>