Aridhaman &Arisudhan: 24 ×K15SLBM (750 km or 470 mi range) or 8 ×K-4 SLBM (3,500 km or 2,200 mi range)[1] or 8 ×K-5 SLBM (5,000–6,000 km or 3,100–3,700 mi range)[8]
6 × 21" (533 mm) torpedo tubes – est 30 charges (torpedoes, cruise missiles or mines)[8]
The lead vessel of the class,INS Arihant was laid down in 2004, launched in 2009 and after extensive sea trials was confirmed to be commissioned in August 2016.[12][13][14]Arihant holds the distinction of being the first ballistic missile submarine to have been built by a country other than one of the fivepermanent members of the United Nations Security Council.[15] As of 25 October 2024,[update] INSArihant andINSArighaat are already on deep sea patrols.[16]
In December 1971, during theIndo-Pakistani War of 1971,US PresidentRichard Nixon sent acarrier battle group namedTask Force 74, led by the nuclear-poweredUSS Enterprise into the international waters of theBay of Bengal in a show of force.[17][18] Task Force 74 remained in international waters, where it was legally entitled to be. The records of Nixon-Kissinger communications show no contingency nor any plan under whichEnterprise would enter Indian or Pakistani waters, or otherwise intervene in the conflict but it is well known that the duo viewed Pakistan as a strong ally in that region and were silent onBangladesh genocide committed by Pakistani military. In response, theSoviet Union sent a submarine armed with nuclear missiles fromVladivostok to trail the US task force in support of India.[19] The event demonstrated the significance of nuclear weapons and ballistic missile submarines to thenPrime MinisterIndira Gandhi.[20] Following the 1974Smiling Buddha nuclear test, the Director of Marine Engineering (DME) at Naval Headquarters initiated a technical feasibility study for an indigenous nuclear propulsion system (Project 932).[21]
PMNarendra Modi addressing the crew of INSArihant. Note the picture of the submarine in the background.
TheArihant-class submarines are nuclear-poweredballistic missile submarines built under the Advanced Technology Vessel (ATV) project.[27] Originally, three submarines were to be built under the ATV project, which itself is part of a larger programme to construct fivenuclear submarines[28] for the Indian Navy. Later, a fourth submarine was added[1] to the₹30,000crore (US$6.2 billion)-worth project.[29] These are the first nuclear submarines designed and built by India.[30] The total cost of the project had hiked to₹90,000 crore (US$13.82 billion) by 2017.[1]
The first two submarines are 111.6 m (366 ft)long[31] with abeam of 11 m (36 ft), adraught of 15 m (49 ft), displacement of 6,000 tonnes (5,900 long tons; 6,600 short tons).[3] The latter submarines included an additional 10 m (33 ft)-long section of four launch tubes increasing the displacement by 1,000 tonnes (980 long tons; 1,100 short tons).[1] The complement is about 95, including officers and sailors.[32] The boats are powered by a single seven blade propeller powered by an 82.5[31]MWe-ratedpressurised light-water reactor (PWR)[33] and can achieve a maximum speed of 12–15 knots (22–28 km/h) when surfaced and 24 knots (44 km/h) when submerged.[32][34]
The submarines, being constructed at the Ship Building Centre (SBC),Visakhapatnam using a USHY-80 grade equivalent Russian steel, has two compartments including propulsion and combat management systems, platform management centre, and the torpedo room. The vessels feature a double hull encompassingballast tanks, two standby auxiliary engines, and a retractable thruster for emergency power and mobility.[31]
The initial batch of two submarines have four launch tubes in their hump and can carry up to twelveK-15 Sagarika missiles with one warhead each (with a range of 750 km or 470 mi) or fourK-4 missiles (with a range of 3,500 km or 2,200 mi).[35][36][37] The third and fourth submarines, featuringArihant Stretch design,[38] will have a larger configuration, carrying twenty-four K-15 Sagarika or eight K-4 missiles, due to the addition of four launch tubes.[1] The Indian Navy personnel received training onINS Chakra, anAkula-classsubmarine leased from Russia in 2012.[39][40]
The submarine's K-15 missiles can reach most of Pakistan and its K-4 can target all of Pakistan.[41] The K-4 may also be capable of targetingBeijing, but would need to be in the northern most waters ofBay of Bengal.[41] Deployment of the Arihant to the Pacific Ocean is unlikely given the submarine's noise issues.[41]
Theclassified project is headquartered inNew Delhi and remains under direct supervision of thePrime Minister's Office and theNational Security Advisor.[1] The submarines are powered by apressurised water reactor withhighly enriched uranium fuel.[9][42] The miniaturised version of the reactor was designed and built by theBhabha Atomic Research Centre (BARC) at theIndira Gandhi Centre for Atomic Research (IGCAR) inKalpakkam.[43] It included a 42-metre (138 ft) section of the submarine's pressure hull containing the shielding tank with water and the reactor, a control room, as well as an auxiliary control room for monitoring safety parameters.[44] The prototype reactor became critical on 11 November 2003 and was declared operational on 22 September 2006.[20] Successful operation of the prototype for three years enabled the production version of the reactor forArihant.[33][45] The reactor subsystems were tested at the Machinery Test Center inVisakhapatnam.[46] Facilities for loading and replacing the fuel cores of the naval reactors in berthed submarines were also established.[20] The prototype 83 MW light water reactor that was installed atKalpakkam by BARC is codenamed S1 and is used to train nuclear submariners.[1]
In 2006, a high-level committee led byR. Chidambaram, the thenprincipal scientific advisor to the Government of India, had assessed India's ability to construct threeS5 series of SSBNs. The project with a budget of₹10,000crore (equivalent to₹320 billion or US$3.8 billion in 2023) divided amongDRDO,BARC and the ATV headquarters. The construction would tentatively begin in 2015 followed with the first submarine to be deployed in 2021. Its projected specifications of the submarine includeddisplacement of 13,500 t (13,300 long tons; 14,900 short tons), 12VLS with anMIRV-equippedSLBM with a range of 6,000 km (3,700 mi). The missile later evolved asK-6 ballistic missile.[1]
Around 2007, the thenfinance minister,P. Chidambaram, who was a member of the political committee which monitors the ATV programme, questioned the huge amount of money being spent on submarines with just 4 missile launch tubes. Thereafter, the ATV project team evolved the design intoArihant-stretch.[38] The improved design incorporated a 10 metre-long section for four more missile tubes to be equipped withK-4 SLBMs. This design would be applied to S4 boat.[1] The boat can, hence, accommodate 24 B-05 short-range missiles or 8 K-4 long-range missiles.[38][51]
On 24 December 2009, theHindustan Shipyard, located at Visakhapatnam, was transferred from theMinistry of Shipping to theMinistry of Defence to support the construction ofArihant-class submarine programme. This would help in utilising the shipyard's infrastructure in the project.[52][53]
Around 2012, with the S5 project remaining in developmental stage, anotherArihant-class submarine was cleared for production to avoid idling of theproduction line. The new unit was designated as S4* (between S4 and S5). The boat would also feature theArihant Stretch design.[1]
In December 2014, the work on a second nuclear reactor began andINS Arighaat startedsea trials in 2017. As per reports released in August 2024, INS Arighaat was commissioned before October 2024.[54][55] On 29 August 2024, after extensive trials and upgrades INS Arighaat was formally commissioned.[56]
INS Aridhaman was launched in November 2021.[1][57] The submarine begun sea trials in 2022.[58] On 30 August 2024, a report suggested that this submarine will be commissioned in the next 6 months.[59]
In August 2024, it was reported that a fifth Arihant class submarine is planned to be constructed.[60]
12 February 2009: The Advanced Technology Vessel project, meant to deliver three submarines, is part of a $2.9 billion programme to build five nuclear submarines. As per the thenDefence Minister,A. K. Antony, the first submarine was in the final stages of construction aftersupply chain bottlenecks were cleared and DRDO was already developingsubmarine-launched ballistic missile.[28][62] The project was conceived in 1970s and operationalised in 1980s, though public acknowledgement never came from official sources until this announcement by the defence minister.[63] There were delays to miniaturise thenuclear reactor core for the submarine and Russian technology help was sought to solve the issues without delays. Another factor that resulted in delays was lack ofmetallurgical expertise and lack of experience of Indian hull makers on the chosen material for the submarine. The successful development of a nuclear submarine came after two failed attempts in the 1970s and 1980s.[64]
16 July 2009: Multiple reports suggested that the first vessel under the Advanced Technology Vessel would be launched byGursharan Kaur, the wife of the then Prime Minister,Manmohan Singh, on 26 July 2009. The ceremony would be held inNaval Dockyard (Visakhapatnam). The vessel was namedINS Arihant, meaning "destroyer of enemies". The design is based onCharlie-I submarines, while both the displacement and submerged speed are higher than the Charlie-I designs. While being launched, thedry dock in the Shipbuilding Centre in Visakhapatnam will be flooded and the submarine would be moved out of the SBC. The vessel would be then towed to a nearbypier for harbour trials during which, the nuclear power plant and auxiliary systems would be validated before its sea trials in theBay of Bengal. The submarine was expected to be commissioned within two to three years. Meanwhile,hull sections of two additional ATVs have been completed in theHazira facility ofLarsen & Toubro and are to be transported to the SBC soon afterArihant exits the dock space.[65][66][62]
26 July 2009: The first submarine of the class,Arihant, was launched into the water. The launch took place after three decades of initiating the design stage of the project. The Defence Minister would also attended the event. The harbour acceptance and system trials was scheduled for one year. The submarine was built at a cost of $2.9 billion.[67] Meanwhile, many expected that the operationalisation of the submarine would take much longer than two years.[68] Harbour acceptance trials and followed by sea acceptance trials, including the surface and sub-surface domains, respectively, were to be conducted before commissioning the submarine.[27] Even the nuclear reactor was yet to be fitted onboard and would be followed by the reactor reachingcriticality, which would be a milestone.[69] The submarine, equipped withSagarika missiles,[27] would serve as atechnology demonstrator for the following nuclear submarines.[70][9]
9 August 2014: The submarine'snuclear reactor became critical for the maiden time after four years of harbour acceptance patrol. The Navy wanted the submarine ready for deterrent patrol in 2014. Meanwhile, the second submarine was already at an advanced stage of construction at the SBC and could be launched in a year later.[71]
13 December 2014:Arihant was entered sea for the first time[72] after being flagged off for extensive sea trials following harbour trials.[73] The sea acceptance trials for the submarine was initially slated for February 2012.[29]
25 November 2015: A dummy or unarmed B-05Sagarika missile was successfully test fired from INSArihant from a depth of 20 metres.[61][74]
31 March 2016: TheK-4 missile was successfully tested from INSArihant, 45 nautical miles away from theVishakhapatnam coast. The missile with a dummy payload was launched from the submarine in full operational configuration. The trial was carried out with the support of the personnel ofStrategic Forces Command (SFC) while theDRDO provided all the logistics.[75][76][77]
August 2016: The first boat of the class, INSArihant, was commissioned.[12][78]
19 November 2017: The second submarine, christenedArighaat, was launched by the then defence minister,Nirmala Sitharaman, with a low-profile, traditional ceremony. The vessel was floated out after flooding the drydock. Reportedly, commissioning of the vessel would take three years. It has an indigenous content of 60%. The third (S4) and fourth (S4*) submarine, with eight launcher units, was expected to be launched in 2020 and 2022, respectively.[1]
July 2018: The submarine was reportedly ready to be fully operationalised with several weapons firing trials and deep diving trials off the coast of Visakhapatnam having been completed since five months earlier. The submarine was being accompanied by RFSEpron, a Russian-originPrut-classsubmarine rescue ship which arrived in India on 1 October 2017.[79]
11–12 August 2018: The B-05 missile system was fired twice on 11th and once on 12th of August from INSArihant and was operationalised two decades since the missile systems development commenced. All the missiles followed the designated trajectories and were fired 10 km away from Visakhapatnam from a depth of 20 m.[80]
4 November 2018:Arihant completed its first deterrence patrol for 20 days.[10][81][11]
16 October 2024: The fourth and final submarine of the class, with an indigenous content of 75% and equipped with K4 missiles, was launched.[83]
2 December 2025:Aridhaman had entered the final stages of trials and was expected to be commissioned soon.[84]
30 December 2025: The fourth submarine, S4*, had reportedly departed the harbour for sea trials a week earlier and is expected to be commissioned in early 2027. Meanwhile,Aridhaman, the third unit had completed its sea trials a few weeks ago and is now to be commissioned in early 2026 after being delivered.[85][86]
5 January 2026: A report suggested that the final submarine, so far referred to as S4*, will be named INSArisudan. The name has been proposed by the ship-naming committee of the Indian Navy. The name is yet to be receive clearance by the defence ministry and eventually, thePresident of India, who is also the Supreme Commander of the Armed Forces.[87]
^abc"Indian Navy Ups the Stakes With Newest Nuclear Submarine INS Aridaman".The Wire. 3 December 2025. Retrieved12 January 2026.This length increase – earning it the nickname "Arihant Stretch" in overseas naval circles – was to accommodate an expanded vertical missile launch system, now doubled to eight tubes, enabling the SSBN to carry either eight K-4 submarine-launched ballistic missiles (SLBMs), with a range of 3,500 km, or 24 K-15 SLBMs striking 750 km away.
^abcNathan Powell. "The Arihant-Class SSBN and the Advent of Sea-Based Nuclear Forces in India, China, and Pakistan".Project on Nuclear Issues: A Collection of Papers from the 2017 Conference Series and Nuclear Scholars Initiative:141–142.
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