Arihant-class submarine

In December 1971, during the Indo-Pakistani War of 1971, the US President, Richard Nixon, sent a carrier battle group, named Task Force 74, led by the nuclear-powered into the international waters of the Bay of Bengal in a show of force. 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 which Enterprise 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 on the Bangladesh genocide committed by Pakistani military. In response, the Soviet Union sent a submarine armed with nuclear missiles from Vladivostok to trail the US task force in support of India. The event demonstrated the significance of nuclear weapons and ballistic missile submarines to the then Indian Prime Minister, Indira Gandhi. Following the Smiling Buddha nuclear test in 1974, the Director of Marine Engineering (DME) at Naval Headquarters initiated a technical feasibility study for an indigenous nuclear propulsion system for a submarine by a small task force, led by a Commander-ranked officer, under Project 932 in coordination with the Department of Atomic Energy (DAE). The Indian Navy's Advanced Technology Vessel project to design and construct a nuclear submarine took shape in the 1990s. Then Defence Minister George Fernandes confirmed the project in 1998. The initial intent of the project was to design nuclear-powered fast attack submarines, though following nuclear tests conducted by India in 1998 at Pokhran Test Range and the Indian pledge of no first use, the project was re-aligned towards the design of a ballistic missile submarine in order to complete India's nuclear triad. ==Description==

General characteristics The first two submarines are long The latter submarines included an additional -long section of four launch tubes increasing the displacement by . The submarines, being constructed at the Ship Building Centre (SBC), Visakhapatnam using a US HY-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 encompassing ballast tanks, two standby auxiliary engines, and a retractable thruster for emergency power and mobility. MWe-rated pressurised light-water reactor (PWR) and can achieve a maximum speed of when surfaced and when submerged. Weapon systems The initial batch of two submarines have four launch tubes in their hump and can carry up to twelve K-15 Sagarika missiles with one warhead each (with a range of ) or four K-4 missiles (with a range of ). The third and fourth submarines, featuring Arihant Stretch design, will have a larger configuration, carrying twenty-four K-15 Sagarika or eight K-4 missiles, due to the addition of four launch tubes. The Indian Navy personnel received training on , an leased from Russia in 2012. The submarine's K-15 missiles can reach most of Pakistan and its K-4 can target all of Pakistan. ==Development==

addressing the crew of INS Arihant. Note the picture of the submarine in the background. The Arihant-class submarines are nuclear-powered ballistic missile submarines built under the Advanced Technology Vessel (ATV) project. Originally, three submarines were authorised under the ATV project, at a cost of , The overall project cost had hiked to by 2017. The facility served as the site for hull construction. The steam turbines and associated systems integrated with the reactor were supplied by Walchandnagar Industries. Former Prime Minister of India, Manmohan Singh, had lauded ATV project as a "productive public–private partnership". On 24 December 2009, the Hindustan Shipyard, located at Visakhapatnam, was transferred from the Ministry of Shipping to the Ministry of Defence to support the construction of Arihant-class submarine programme. This would help in utilising the shipyard's infrastructure in the project. Prototype light water reactor The miniaturised version of the reactor was designed and built by the Bhabha Atomic Research Centre (BARC) at the Indira Gandhi Centre for Atomic Research (IGCAR) in Kalpakkam. It included a 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. The prototype reactor became critical on 11 November 2003 and was declared operational on 22 September 2006. The reactor subsystems were tested at the Machinery Test Center in Visakhapatnam. Facilities for loading and replacing the fuel cores of the naval reactors in berthed submarines were also established. The prototype 83 MW light water reactor that was installed at Kalpakkam by BARC is codenamed S1 and is used to train nuclear submariners. == Project timeline ==

1970–2000 • 1974: The nuclear submarine project was sanctioned following the Smiling Buddha tests under the then Prime Minister, Indira Gandhi. • 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 then Defence Minister, A. K. Antony, the first submarine was in the final stages of construction after supply chain bottlenecks were cleared and DRDO was already developing submarine-launched ballistic missile. 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. There were delays to miniaturise the nuclear 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 of metallurgical 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. • 16 July 2009: Multiple reports suggested that the first vessel under the Advanced Technology Vessel would be launched by Gursharan Kaur, the wife of the then Prime Minister, Manmohan Singh, on 26 July 2009. The ceremony would be held in Naval Dockyard (Visakhapatnam). The vessel was named '', meaning "destroyer of enemies". The design is based on Charlie-I submarines, while both the displacement and submerged speed are higher than the Charlie-I designs. While being launched, the dry 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 nearby pier for harbour trials during which, the nuclear power plant and auxiliary systems would be validated before its sea trials in the Bay 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 the Hazira facility of Larsen & Toubro and are to be transported to the SBC soon after Arihant'' exits the dock space. Meanwhile, many expected that the operationalisation of the submarine would take much longer than two years. 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. The submarine, equipped with Sagarika missiles, • 13 December 2014: Arihant was entered sea for the first time after being flagged off for extensive sea trials following harbour trials. The sea acceptance trials for the submarine was initially slated for February 2012. • 25 November 2015: A dummy or unarmed B-05 Sagarika missile was successfully test fired from INS Arihant from a depth of 20 metres. • 31 March 2016: The K-4 missile was successfully tested from INS Arihant, 45 nautical miles away from the Vishakhapatnam 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 of Strategic Forces Command (SFC) while the DRDO provided all the logistics. • August 2016: The first boat of the class, INS Arihant, was commissioned. • 19 November 2017: The second submarine, christened , 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. • 11–12 August 2018: The B-05 missile system was fired twice on 11th and once on 12th of August from INS Arihant 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. • 4 November 2018: Arihant completed its first deterrence patrol for 20 days. • 2022: Aridhaman begun sea trials. • 11 August 2024: Arighaat was being prepared for being commissioned within two months. • 29 August 2024: Arighaat was commissioned in the presence of the Defence Minister, Rajnath Singh. • 16 October 2024: The fourth and final submarine of the class, with an indigenous content of 75% and equipped with K4 missiles, was launched. • 2 December 2025: Aridhaman had entered the final stages of trials and was expected to be commissioned soon. • 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. • 5 January 2026: A report suggested that the final submarine, so far referred to as S4*, will be named INS Arisudan. 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, the President of India, who is also the Supreme Commander of the Armed Forces. • 3 April 2026: INS Aridhaman was commissioned. ==Ships in class==