Arihant-class submarine

The Arihant-class () is a class of nuclear-powered ballistic missile submarines in service with the Indian Navy. They were developed under the Advanced Technology Vessel (ATV) project to design and build nuclear-powered submarines. The project is being seen as a black project. These vessels are classified as 'strategic strike nuclear submarines' by India.

The lead vessel of the class, , was laid down in 2004, launched in 2009 and, after extensive sea trials, confirmed to be commissioned in August 2016. Arihant holds the distinction of being the first ballistic missile submarine to have been built by a country other than one of the five permanent members of the United Nations Security Council. INS Arihant and INS Arighaat are already on deep sea patrols.

History

In December 1971, during the Indo-Pakistani War of 1971, 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 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 then Prime Minister Indira Gandhi. Following the 1974 Smiling 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).

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

The Arihant-class submarines are nuclear-powered ballistic missile submarines built under the Advanced Technology Vessel (ATV) project. Originally, three submarines were to be built under the ATV project, which itself is part of a larger programme to construct five nuclear submarines for the Indian Navy. Later, a fourth submarine was added to the -worth project. These are the first nuclear submarines designed and built by India. The total cost of the project had hiked to by 2017.

The first two submarines are long with a beam of , a draught of , displacement of . The latter submarines included an additional -long section of four launch tubes increasing the displacement by . The complement is about 95, including officers and sailors. The boats are powered by a single seven blade propeller powered by an 82.5 MWe-rated pressurised light-water reactor (PWR) and can achieve a maximum speed of when surfaced and when submerged.

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.

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. The K-4 may also be capable of targeting Beijing, but would need to be in the northern most waters of Bay of Bengal. Deployment of the Arihant to the Pacific Ocean is unlikely given the submarine's noise issues.

Development

The classified project is headquartered in New Delhi and remains under direct supervision of the Prime Minister's Office and the National Security Advisor. The submarines are powered by a pressurised water reactor with highly enriched uranium fuel. 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. Successful operation of the prototype for three years enabled the production version of the reactor for Arihant. 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.

Larsen & Toubro undertook critical detailed engineering based on design provided by the Navy and DRDO at its submarine design centre. The firm was also the single largest contributor to the programme ranging from the steel cutting of the submarines to their launch. The facility served as the site for hull construction. Tata Power SED built the control systems for the submarine. 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".

In 2006, a high-level committee led by R. Chidambaram, the then principal scientific advisor to the Government of India, had assessed India's ability to construct three S5 series of SSBNs. The project with a budget of divided among DRDO, 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 included displacement of , 12 VLS with an MIRV-equipped SLBM with a range of . The missile later evolved as K-6 ballistic missile.

Around 2007, the then finance 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 into Arihant-stretch. The improved design incorporated a 10-metre-long section for four more missile tubes to be equipped with K-4 SLBMs. This design would be applied to S4 boat. The boat can, hence, accommodate 24 B-05 short-range missiles or 8 K-4 long-range missiles.

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.

Around 2012, with the S5 project remaining in developmental stage, another Arihant-class submarine was cleared for production to avoid idling of the production line. The new unit was designated as S4* (between S4 and S5). The boat would also feature the Arihant Stretch design.

In December 2014, the work on a second nuclear reactor began and started sea trials in 2017. As per reports released in August 2024, INS Arighaat was commissioned before October 2024. On 29 August 2024, after extensive trials and upgrades INS Arighaat was formally commissioned.

INS Aridhaman was launched in November 2021. The submarine begun sea trials in 2022. On 30 August 2024, a report suggested that this submarine will be commissioned in the next 6 months.

In August 2024, it was reported that a fifth Arihant class submarine is planned to be constructed.

Project timeline

• 1974: The nuclear submarine project was sanctioned following the Smiling Buddha tests under the then Prime Minister, Indira Gandhi.
• 1983: Additional funds were allotted for the project during the Fourth Indira Gandhi ministry.
• 1998: A. P. J. Abdul Kalam cut the first steel for the submarine hull at the Larsen & Toubro facility at Hazira. L&T had received the submarine hull construction contract. Simultaneously, the submarine's design was upgraded from nuclear attack profile to nuclear-powered ballistic missile submarine following Pokhran-II.
• 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.
• 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. 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. Even the nuclear reactor was yet to be fitted onboard and would be followed by the reactor reaching criticality, which would be a milestone. The submarine, equipped with Sagarika missiles, would serve as a technology demonstrator for the following nuclear submarines.
• 9 August 2014: The submarine's nuclear 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.
• 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.
• 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 RFS Epron, a Russian-origin Prut-class submarine rescue ship which arrived in India on 1 October 2017.
• 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.
• 29 August 2024: Arighaat commissioned.
• 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.