View source for Russian submarine Nerpa (K-152)

{{Short description|Russian Akula-class submarine}}
{{Other ships|Russian submarine Nerpa|INS Chakra}}
{{Good article}}
{{EngvarB|date=January 2014}}
{{Use dmy dates|date=January 2014}}
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|Ship image=Indian Navy's TROPEX-2014 (8).JPG
|Ship caption=INS ''Chakra''
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|Ship country=Russia
|Ship flag={{shipboxflag|Russia|navy}}
|Ship name=K-152 ''Nerpa''
|Ship namesake=[[Baikal seal]]
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|Ship builder=[[Amur Shipbuilding Plant]], [[Komsomolsk-on-Amur]]
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|Ship laid down=1993
|Ship launched=October 2008
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|Ship fate=Leased to the Indian Navy for 10 years in 2012, returned in June 2021
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|Ship country=India
|Ship flag={{shipboxflag|India|naval-2014}}
|Ship name=''Chakra''
|Ship namesake= [[Sudarshana Chakra]]
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|Ship status=Returned to Russia, June 2021
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|Ship type= [[Nuclear submarine|Nuclear-powered]] [[attack submarine]]
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|Ship displacement={{convert|8140|t|long ton|lk=on}} surfaced
|Ship length={{convert|108.0|-|111.7|m|ft|abbr=on}} (sources vary)
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'''''Nerpa''''' (renamed '''INS ''Chakra''''' in [[Indian Navy]] service) is a {{convert|8140|t|long ton|adj=on}} Project 971 (or Project 518;<ref>{{Cite web |url=http://government.ru/eng/docs/9439/print/ |title=Prime Minister Vladimir Putin has a working meeting with Roman Trotsenko, President of the United Shipbuilding Corporation (USC) |date=2010 |website=The Russian Government |url-status=dead |archive-url=https://archive.today/20120709134739/http://government.ru/eng/docs/9439/print/ |archive-date=9 July 2012}}</ref> NATO: [[Akula-class submarine|''Akula''-class]]) [[Nuclear submarine|nuclear-powered]] [[attack submarine]]. The construction of the submarine was started in [[Russia]] in 1993, but was suspended due to lack of funding. [[India]] then sponsored further construction<ref name="Top10FAQ">{{Cite web |url=https://www.ndtv.com/india-news/ins-chakra-top-10-must-know-facts-475108 |title=INS Chakra: Top 10 must-know facts |first=Sudhi Ranjan |last=Sen |date=6 April 2012 |website=NDTV.com}}</ref> and sea trials of the submarine provided it was leased to the Indian Navy for 10 years. It was launched as ''K-152 Nerpa'' in October 2008 and entered service with the [[Russian Navy]] in late 2009. The submarine was leased to the [[Indian Navy]] in 2011 after extensive trials, and was formally commissioned into service as INS ''[[INS Chakra|Chakra]]'' with the [[Eastern Naval Command]] at a ceremony in [[Visakhapatnam]] on 4 April 2012.<ref>{{cite web |title=Russian-built nuclear submarine joins Indian Navy |url=https://www.bbc.co.uk/news/world-asia-india-17606829 |access-date=4 April 2012 |website=BBC News |date=4 April 2012 |url-status=live |archive-url=https://web.archive.org/web/20120404180531/http://www.bbc.co.uk/news/world-asia-india-17606829 |archive-date=4 April 2012}}</ref> In June 2021 ''Chakra'' was spotted on the surface escorted by Indian and Russian warships in the [[Singapore Strait]] while presumably heading towards the Russian naval base in [[Vladivostok]]; some media speculated that she was returning to Russia before the expiry of the lease term.<ref name="NDTV">{{Cite web |url=https://www.ndtv.com/india-news/navys-only-nuclear-attack-submarine-ins-chakra-returns-to-russia-before-lease-expires-2456368 |title=Navy's Only Nuclear Attack Submarine Returns To Russia Before Lease Expires |first=Vishnu |last=Som |date=4 June 2021 |website=NDTV.com}}</ref>

While ''Nerpa'' was undergoing sea trials in the [[Sea of Japan]] on 8 November 2008, a [[Gaseous fire suppression|fire suppression system]] was [[K-152 Nerpa accident|accidentally activated]], killing 20 civilian specialists and navy crew members and injuring 41 others.

==Construction==
''Nerpa'' was laid down at the [[Komsomolsk-on-Amur]] shipyard in 1993, but its completion was delayed for nearly a decade due to a lack of funds caused by the economic crisis of the early 1990s.<ref name="KP">{{cite news |title=Twenty Persons Perished Aboard a Submarine Due to a Defective Fire-Extinguishing System |newspaper=[[Komsomolskaya Pravda]] |date=9 November 2008}}</ref> The partly constructed vessel was mothballed until 2004, when Rosprom (the Federal Agency for Industry) signed an agreement with the Indian government to complete the submarine and lease it to the Indian Navy. The vessel was intended to be completed by 2007, but underwent further delays. In 2007, it was transferred to the Vostok shipyard in the [[closed city]] of [[Bolshoy Kamen]], [[Primorsky Krai]], for fitting-out. It was launched in October 2008 for sea trials, following which it was due to be handed over to the Russian Defence Ministry.<ref name="KP2">{{cite news |title=In Its First Trials the Submarine Nerpa Leaked at the Seams |newspaper=Komsomolskaya Pravda |date=9 November 2008}}</ref> Reports in the Indian media suggest that the resumption of construction was underwritten with Indian funding.<ref>{{cite web |url=http://www.marinelog.com/DOCS/NEWSMMVII/2008nov00090.html |title=Russian death sub was intended for India |date=9 November 2008 |website=Marine Log |access-date=11 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081113115608/http://www.marinelog.com/DOCS/NEWSMMVII/2008nov00090.html |archive-date=13 November 2008}}</ref>

The standard of the vessel's construction were criticised by several commentators. Aleksandr Golts, defence editor of the ''[[The Other Russia (coalition)|Yezhednevny Zhurnal]]'' newspaper, said that in the 1980s, the Amur shipyard turned out submarines "one after another, like pancakes,"<ref name="newsweek">{{cite news |url=http://www.newsweek.com/id/168382 |title=Behind the Russian Sub Disaster |date=9 November 2008 |newspaper=[[Newsweek]] |access-date=11 November 2008 |url-status=live |archive-url=https://web.archive.org/web/20081113211127/http://www.newsweek.com/id/168382 |archive-date=13 November 2008}}</ref> but from 1993 to 2008 had produced just one. "The old specialists had left, and the new ones lacked professionalism."<ref name="newsweek"/> An unnamed worker at the Amur shipyard told ''[[Komsomolskaya Pravda]]'' that there were "questions about the quality of the metal that was used in building the nuclear submarine", some of which had been bought from China, and alleged that "when the first trials of the submarine were carried out water was leaking in between the seams! So it is not surprising that the work dragged on."<ref name="KP2" />

During May 2009, the repairs were reported to be almost complete and new sea trials were planned for 15–20 June.{{citation needed|date=April 2023}} By October 2009, the work had still not been completed due to the shipyard's electrical supply having been disconnected. Nikolay Povzyk, the head of the shipyard, complained they had not been paid the 1.9 billion roubles (63.8 million dollars) owed for the work carried out on ''Nerpa''.<ref>{{cite news |url=http://www.spacewar.com/reports/Repairs_of_India-bound_Russian_sub_hit_by_lack_of_funds_report_999.html |title=Repairs of India-bound Russian sub hit by lack of funds: report |agency=[[Agence France-Presse|AFP]] |date=8 October 2009 |website=Space War |access-date=21 February 2010 |url-status=live |archive-url=https://web.archive.org/web/20091013143356/http://www.spacewar.com/reports/Repairs_of_India-bound_Russian_sub_hit_by_lack_of_funds_report_999.html |archive-date=13 October 2009}}</ref>

==Lease to India==
[[File:AkulaProjekt971U right.png|thumb|right|INS ''Chakra'' of the Indian Navy]]
[[File:INS Chakra.jpg|thumb|right|''Chakra'' in the open sea, flying the [[Indian Naval Ensign]]]]
In 2008, Russia had an agreement pending with India worth US$2&nbsp;billion for the lease of ''Nerpa'' and another [[Akula-class submarine|Project 971 Shchuka-B]]-class submarine.<ref name="AFP">{{cite web |url=http://afp.google.com/article/ALeqM5hD_OJemR184COjKR32WI3G3He4cw |title=More than 20 killed in Russian nuclear sub accident: spokesman |website=[[Agence France-Presse|AFP]] |date=9 November 2008 |access-date=18 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20090223230359/http://afp.google.com/article/ALeqM5hD_OJemR184COjKR32WI3G3He4cw |archive-date=23 February 2009}}</ref> Of this, ''K-152 Nerpa'' would be leased for 10 years to India at an estimated cost of US$670 million. The submarine was handed over to India on 30 December 2011.<ref>{{cite web |url=http://www.ndtv.com/article/world/russia-hands-over-nerpa-attack-submarine-to-india-162241 |title=Russia hands over Nerpa attack submarine to India |website=NDTV.com |date=30 December 2011 |access-date=19 July 2012 |url-status=live |archive-url=https://web.archive.org/web/20120109023101/http://www.ndtv.com/article/world/russia-hands-over-nerpa-attack-submarine-to-india-162241 |archive-date=9 January 2012}}</ref> After being handed over to the Indian Navy, it was commissioned as INS ''Chakra''.<ref name="moscowtimes1">{{cite web |url=http://www.moscowtimes.ru/article/1010/42/372216.htm |title=Nuclear Submarine Accident Kills 20 |first=Nabi |last=Abdullaev |newspaper=[[The Moscow Times]] |date=10 November 2008 |access-date=11 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081112175240/http://www.moscowtimes.ru/article/1010/42/372216.htm |archive-date=12 November 2008}}</ref> ''Nerpa'' is the Russian word for the [[Baikal seal]],<ref>{{cite web |title=Baikal Seal |website=Seal Conservation Society |access-date=21 November 2008 |url=http://www.pinnipeds.org/species/baikal.htm |url-status=dead |archive-url=https://web.archive.org/web/20081015073949/http://www.pinnipeds.org/species/baikal.htm |archive-date=15 October 2008}}</ref> and ''[[Sudarshana Chakra|Chakra]]'' is the weapon of the Hindu god [[Vishnu]].<ref>{{cite book |first1=John |last1=Cross |first2=Robert |last2=Charman |title=Healing with the Chakra Energy System |pages=17–18 |year=2006 |publisher=North Atlantic Books |location=Berkeley, CA |isbn=1-55643-625-4}}</ref>

[[Indian Navy|Indian naval crews]] earlier trained to operate the submarine near [[Saint Petersburg|St Petersburg]] and another group of sailors were expected to arrive in [[Vladivostok]] in late 2008 for sea trials.<ref>{{cite news |url=https://timesofindia.indiatimes.com/world/europe/No-significant-damage-to-Russian-sub-to-be-leased-to-India/articleshow/3695371.cms |title=No Significant Damage to Russian Sub |newspaper=[[The Times of India]] |date=10 November 2008 |access-date=28 November 2008 |url-status=live |archive-url=https://web.archive.org/web/20121022092729/http://articles.timesofindia.indiatimes.com/2008-11-10/europe/27949005_1_nerpa-sea-trials-nuclear-powered-submarine |archive-date=22 October 2012}}</ref> The training of the crew was viewed as crucial to India's own nuclear submarine programme, known as the {{sclass|Arihant|submarine|0}}.<ref>{{cite news |url=http://economictimes.indiatimes.com/Russian_submarine_accident_kills_20/rssarticleshow/3692578.cms |title=Accident on Russian submarine meant for India kills 20 |date=9 November 2008 |newspaper=The Economic Times |access-date=11 November 2008 |url-status=live |archive-url=https://web.archive.org/web/20121003010542/http://economictimes.indiatimes.com/Russian_submarine_accident_kills_20/rssarticleshow/3692578.cms |archive-date=3 October 2012}}</ref>

After the 2008 accident, there were conflicting reports over the status of the lease. A Russian defence industry official denied that talks had been held with India on the delivery of the nuclear submarine.{{citation needed|date=April 2023}} General of the Army Nikolay Makarov stated that Russia would commission ''Nerpa'' and that it would join seven other {{sclass|Akula|submarine}}s with Russia's [[Pacific Ocean Fleet (Russia)|Pacific Fleet]].{{citation needed|date=April 2023}}

In May 2009, both Russian and Indian defence officials confirmed that ''Nerpa'' would be joining the Indian Navy by the end of 2009, after Russian President Vladimir Putin visited the yard and announced an immediate release of 1.2 billion roubles for the submarine's construction.<ref>{{cite web |url=http://news.xinhuanet.com/english/2009-05/13/content_11368340.htm |title=India to acquire Russian nuclear submarine on lease by year end |date=13 May 2009 |website=[[Xinhua News Agency]] |url-status=dead |archive-url=https://web.archive.org/web/20090517022236/http://news.xinhuanet.com/english/2009-05/13/content_11368340.htm |archive-date=17 May 2009}}</ref>

On 28 December 2009, ''Nerpa'' was commissioned and joined the Russian Navy. The submarine underwent further adjustments in February 2010.{{citation needed|date=April 2023}} By August 2010, Russia was training a crew from the Indian Navy to sail the boat to India in fulfilment of the lease agreement.<ref name="Top10FAQ"/> INS ''Chakra'' was expected to be commissioned into the Indian Navy before October 2011.<ref>{{cite web |url=http://indrus.in/articles/2011/03/18/k-152_nerpa_for_the_indian_navy_12302.html |title=K-152 Nerpa for the Indian Navy |date=March 18, 2011 |website=RIA Novosti |url-status=dead |archive-url=https://web.archive.org/web/20110321231315/http://indrus.in/articles/2011/03/18/k-152_nerpa_for_the_indian_navy_12302.html |archive-date=21 March 2011}}</ref> On 1 July 2011, Russian Navy chief Admiral [[Vladimir Vysotskiy (admiral)|Vladimir Vysotsky]] was quoted as holding that ''the Indian crew is now absolutely prepared for operating the submarine'', which will be on a 10-year lease.<ref>{{cite news |url=https://timesofindia.indiatimes.com/india/Russia-to-hand-over-India-nuclear-sub-by-year-end/articleshow/9070385.cms |title=Russia to hand over India nuclear sub by year-end |date=2 July 2011 |newspaper=[[The Times of India]] |url-status=live |archive-url=https://web.archive.org/web/20120910202218/http://articles.timesofindia.indiatimes.com/2011-07-02/india/29730427_1_nuclear-submarine-nuclear-powered-submarine-nerpa |archive-date=10 September 2012}}</ref>

On 23 January 2012, the ship was commissioned at [[Bolshoy Kamen]] under the command of Captain P. Ashokan.<ref>{{Cite tweet |author=SpokespersonNavy |user=indiannavy |number=866597675055149057 |date=22 May 2017 |title=INS Chakra - Akula class SSN |access-date=2017-05-23 |url-status=live |archive-url=https://web.archive.org/web/20180321144313/https://twitter.com/indiannavy/status/866597675055149057 |archive-date=21 March 2018}}</ref> She commenced her home voyage under Indian control from the Russian port of Vladivostok to its Indian base at Visakhapatnam.<ref>{{cite web |url=https://news.yahoo.com/india-sails-nuclear-submarine-home-002834034.html |title=India sails new nuclear submarine home |date=23 January 2012 |agency=AFP (Agence France-Presse) |website=Yahoo! News |access-date=23 January 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120125234206/http://news.yahoo.com/india-sails-nuclear-submarine-home-002834034.html |archive-date=25 January 2012}}</ref> An official Russian announcement of the transfer was still pending at that time. INS ''Chakra'' was inducted into the Indian Navy on 4 April 2012.<ref>{{Cite news |url=https://economictimes.indiatimes.com/news/politics/nation/ins-chakra-govt-inducts-8000-ton-russian-origin-akula-ii-class-nerpa-into-navy/articleshow/12526102.cms |title=INS Chakra: Govt inducts Russian-origin Akula II class Nerpa into Navy |date=4 April 2012 |newspaper=The Economic Times |url-status=live |archive-url=https://web.archive.org/web/20120407070809/http://economictimes.indiatimes.com/news/politics/nation/ins-chakra-govt-inducts-8000-ton-russian-origin-akula-ii-class-nerpa-into-navy/articleshow/12526102.cms |archive-date=7 April 2012}}</ref><ref>{{Cite web |url=https://www.indiatoday.in/india/south/story/ins-chakra-inducted-into-indian-navy-98027-2012-04-04 |title=INS Chakra formally inducted into Indian Navy |date=4 April 2012 |agency=P.T.I. |website=[[India Today]] |url-status=live |archive-url=https://web.archive.org/web/20120919152021/http://indiatoday.intoday.in/story/ins-chakra-inducted-into-indian-navy/1/182955.html |archive-date=19 September 2012}}</ref>

The ''Nerpa'' was returned to Russia in June 2021, ahead of the expiry of the 10 year lease, due to "increasingly unreliable powerplant and maintenance issues" besides the overall condition of the vessel which was extensively used by the Indian Navy to train crews on advanced nuclear submarines.<ref name="NDTV"/> According to other sources, the main reason for the early return was an explosion of a high-pressure air cylinder in the spring of 2020. The cylinder was located between the two hulls and its explosion killed a crew member and damaged electronic weapons, hydro-acoustic equipment and the hulls.<ref>{{Cite web |url=https://frontierindia.com/nuclear-submarine-ins-chakra-aka-nerpa-sent-back-to-russia-for-conventional-reasons/ |title=nuclear submarine INS Chakra aka Nerpa sent back to Russia for conventional reasons |date=9 June 2021 |website=frontierindia.com |language=en}}</ref>

The [[Soviet submarine K-43|similarly named ''Chakra'']] was a [[Charlie-class submarine|Charlie I-class submarine]] leased by India from Russia from 1988 to 1992.

==2008 accident==
{{Main|2008 Russian submarine K-152 Nerpa accident}}
{{Infobox event
|image=
|caption=
|date= 8 November 2008
|time=
|place= Pacific Ocean, [[Sea of Japan]], off the coast of [[Vladivostok]]<ref name="India">{{Cite news |url=http://indiatoday.intoday.in/story/Freak-accident-on-Russian-N-submarine-kills-21/1/19749.html |title=Freak accident on Russian N-submarine kills 21 |date=9 November 2008 |last=Unnithan |first=Sandeep |website=[[India Today]] |access-date=2015-07-31 |url-status=live |archive-url=https://web.archive.org/web/20160304131635/http://indiatoday.intoday.in/story/Freak-accident-on-Russian-N-submarine-kills-21/1/19749.html |archive-date=4 March 2016}}</ref>
|suspects=
|casualties1= 20 killed
|casualties2= 21 injured
|casualties3=
|notes= Accident occurred on board the Russian submarine ''K-152 Nerpa''
}}
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An accident occurred aboard ''K-152 Nerpa'' at 8:30 PM local time on 8 November 2008,<ref>{{cite news |url=http://www.dispatch.com/live/content/national_world/stories/2008/11/10/lat_russia_sub_1110.ART_ART_11-10-08_A5_B2BRFFV.html?sid=101 |title=False fire alarm blamed in Russian sub deaths |last=Loiko |first=Sergei L. |newspaper=[[The Columbus Dispatch]] |date=8 November 2008 |access-date=11 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20110413052913/http://www.dispatch.com/live/content/national_world/stories/2008/11/10/lat_russia_sub_1110.ART_ART_11-10-08_A5_B2BRFFV.html?sid=101 |archive-date=13 April 2011}}</ref> during an underwater test run in the Pacific Ocean.<ref name="CNN">{{cite news |title=Russia: Sub returns to base after 20 killed |url=http://www.cnn.com/2008/WORLD/europe/11/08/russia.submarine.ap/index.html |date=9 November 2008 |access-date=2015-07-31 |agency=Associated Press |publication-place=Moscow |website=CNN |archive-url=https://web.archive.org/web/20081206090512/http://www.cnn.com/2008/WORLD/europe/11/08/russia.submarine.ap/index.html |archive-date=2008-12-06 |url-status=dead}}</ref> A total of 208 people – 81 military personnel and 127 civilians – were on board at the time of the accident.<ref name="KP" /> At least 20 people were killed by [[asphyxiation]]<ref>{{Cite web |title=Russian navy: sub accident kills more than 20 |url=http://6abc.com/archive/6496066/ |access-date=2015-07-31 |first=Steve |last=Gutterman |agency=Associated Press |publication-place=Moscow |website=[[WPVI-TV|6ABC]] |date=8 November 2008 |url-status=live |archive-url=https://web.archive.org/web/20151225065724/http://6abc.com/archive/6496066/ |archive-date=25 December 2015}}</ref> and at least 21 more were injured,<ref name="BBC">{{cite news |url=http://news.bbc.co.uk/2/hi/europe/7718156.stm |title=Twenty die on Russian submarine |date=9 November 2008 |website=BBC News |access-date=9 November 2008 |url-status=live |archive-url=https://web.archive.org/web/20081109004840/http://news.bbc.co.uk/2/hi/europe/7718156.stm |archive-date=9 November 2008}}</ref> making it the worst Russian [[Major submarine incidents since 2000|submarine disaster]] since ''[[Russian submarine K-141 Kursk|Kursk]]'' sank in 2000.<ref name="Guardian">{{cite news |url=https://www.theguardian.com/world/2008/nov/09/russia |title=Twenty die in nuclear submarine accident |last=Syal |first=Rajeev |date=9 November 2008 |newspaper=[[The Guardian]] |access-date=9 November 2008 |location=London |url-status=live |archive-url=https://web.archive.org/web/20130904055252/http://www.theguardian.com/world/2008/nov/09/russia |archive-date=4 September 2013}}</ref><ref name="Reuters">{{cite news |url=https://www.reuters.com/article/wtMostRead/idUSTRE4A738V20081109 |title=At least 20 die in accident on Russian nuclear sub |last=Maltsev |first=Yuri |date=8 November 2008 |website=Reuters |access-date=9 November 2008 |url-status=live |archive-url=https://web.archive.org/web/20081113114815/http://www.reuters.com/article/wtMostRead/idUSTRE4A738V20081109 |archive-date=13 November 2008}}</ref> Three of the dead were military personnel and the rest were civilians from the Vostok, [[Zvezda shipyard|Zvezda]], Era and Amur shipbuilding yards who were members of the acceptance team.<ref name="Ren TV">[[REN TV]], Moscow, 2030 GMT 10 November 2008</ref>

The incident involved the accidental triggering of a fire extinguishing system which sealed two forward compartments and released Halon 2402 ([[Freon]] R-114B2), [[dibromotetrafluoroethane]]<ref>{{cite news |url=http://www.defense-update.com/analysis/analysis_111108_russian_submarine_fire.html |title=Fire on Board the Russian Navy Akula II Nuclear Submarine kills Twenty Russian Sailors |first=David |last=Eshel |website=Defense Update |date=11 November 2008 |url-status=dead |archive-url=https://web.archive.org/web/20090123133238/http://defense-update.com/analysis/analysis_111108_russian_submarine_fire.html |archive-date=23 January 2009 |access-date=13 November 2008}}</ref> gas into them.<ref name="KP" /> According to survivors, those affected by the gas release were caught off guard and may not have been alerted in time due to warning sirens sounding only after the gas had already begun pouring in. Some of the victims were reported to have been unable to turn on breathing kits before they suffocated.<ref>{{cite web |url=https://www.defencezealer.com/hl=en&tab=jj&blogID=7138272787861320472#editor/target=post;postID=1046525617092730752;onPublishedMenu=allposts;onClosedMenu=allposts;postNum=1;src=postname |title=The Akula class nuclear attack submarine - India set to lease 3rd from Russia |date=18 November 2008 |website=DefenceZealer.com |agency=Associated Press |access-date=14 December 2019}}{{dead link|date=June 2021}}</ref>

On 10 November, a Russian Navy statement blamed the disaster on an "unsanctioned operation" of the fire suppression system aboard ''Nerpa''.<ref name="KP" /> Preliminary investigations concluded that the system had triggered automatically without human intervention. On 13 November, naval investigators announced that a crewman had turned on the system "without permission or any particular grounds".<ref>{{cite news |url=http://kp.ru/daily/24198/403930/ |script-title=ru:Матрос запустил смертельный газ на глазах у своего командира? |trans-title=A sailor fired a lethal gas in front of his commander? |newspaper=[[Komsomolskaya Pravda]] |date=15 November 2008 |access-date=18 November 2008 |language=ru |url-status=live |archive-url=https://web.archive.org/web/20081203234058/http://kp.ru/daily/24198/403930/ |archive-date=3 December 2008}}</ref><ref>{{cite web |url=http://old.lenta.ru/news/2008/11/15/change/ |script-title=ru:Матрос включил систему пожаротушения на "Нерпе" от скуки |trans-title=The sailor turned on the fire extinguishing system on the Nerpa out of boredom |website=[[Lenta.ru]] |date=15 November 2008 |access-date=18 November 2008 |language=ru |url-status=live |archive-url=https://web.archive.org/web/20110716160446/http://old.lenta.ru/news/2008/11/15/change/ |archive-date=16 July 2011}}</ref>

==2017 accident==
Indian media aired public reports in early October 2017 that indicated that INS ''Chakra'' had suffered damage while entering Visakhapatnam harbor, including a large hole in the sonar dome in the bow.<ref>{{cite web |url=http://www.thehindu.com/todays-paper/accident-on-board-ins-chakra/article19793626.ece |title=Accident on board INS Chakra? |newspaper=[[The Hindu]] |date=4 October 2017 |access-date=1 May 2018}}</ref> A Russian team visited India for a joint investigation, which led to the submarine being dry docked for repairs at a cost of ₹125 crore ($20 million) to fix the damage.<ref>{{cite web |url=http://www.thehindu.com/news/national/russia-seeks-125-crore-to-carry-out-repairs-on-ins-chakra/article22734847.ece |title=Russia seeks ₹125 crore to carry out repairs on INS Chakra |newspaper=[[The Hindu]] |date=13 February 2018 |access-date=1 May 2018}}</ref>

==2019==
After the [[2019 Balakot airstrike]] that was conducted by the Indian Air Force, the Indian Navy sent INS ''Chakra'' along with {{INS|Kalvari|S21|6}} to search for the Pakistani submarine {{PNS|Saad||6}} which was believed to be deployed to sea.<ref>{{cite web |url=https://www.ndtv.com/india-news/india-deployed-nuclear-missile-armed-submarine-during-standoff-with-pakistan-2009178 |title=India Deployed Nuclear Missile-Armed Submarine During Standoff With Pak |first=Vishnu |last=Som |date=18 March 2019 |website=NDTV.com}}</ref><ref>{{Cite web |url=https://www.indiatoday.in/india/story/post-balakot-indian-navy-hunted-pakistani-submarine-for-21-days-1554601-2019-06-23 |title=Post Balakot strike, Indian Navy hunted for Pakistani submarine for 21 days |agency=[[Asian News International]] |date=23 June 2019 |website=India Today}}</ref>

==References==
{{Reflist}}

{{Akula-class submarine}}
{{Submarines of the Indian Navy}}
{{2008 shipwrecks}}
{{2017 shipwrecks}}

{{DEFAULTSORT:Nerpa K-152}}
[[Category:Akula-class submarines]]
[[Category:Ships built by Amur Shipbuilding Plant]]
[[Category:2008 ships]]
[[Category:Russian submarine accidents]]
[[Category:Indian submarine accidents]]