India to commission INS Aridhaman as third Arihant-class nuclear ballistic missile submarine.

India is preparing to commission INS Aridhaman after the submarine entered its final phase of harbour and sea trials, Navy officials said during the December 2 briefing.

INS Aridhaman, India’s third indigenously-built nuclear-powered ballistic missile submarine, is set to be commissioned soon after entering the final stage of harbour and sea trials, as stated by Navy Chief Admiral Dinesh K. Tripathi during the pre-Navy Day press conference on December 2, 2025. The submarine will join the existing INS Arihant and INS Arighaat, giving the Indian Navy three operational Arihant-class SSBNs at sea for the first time and expanding the submarine component of the nuclear triad.
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Featuring an enlarged hull compared to the INS Arihant, the INS Aridhaman will have an overall length of about 130 meters, with a beam of 11 meters and a draft of around 9.5 to 10 meters. (Picture source: X/News IADN)

This announcement follows the formal commissioning of INS Arighaat into the Strategic Forces Command in Visakhapatnam on August 29, 2024, after a long construction and trial period. Military assessments during early 2025 already indicated that INS Aridhaman, which has been on trials for close to three years, was planned for commissioning within the year. Built under the Advanced Technology Vessel project at the Ship Building Centre in Visakhapatnam, the INS Aridhaman, designated as S4 or SSBN 82, is the third Indian-made nuclear submarine and the second Arihant-class unit. The submarine was laid down around 2017 to 2018, launched quietly on November 21 or 23, 2021, and has been undergoing harbour acceptance and sea trials since 2022, with final weapon and reactor checks completed by mid-2025.

The INS Aridhaman's displacement is consistently given as about 6,000 tonnes on the surface and approximately 7,000 tonnes submerged, with a complement of roughly 95 to 100 crew members, including officers and sailors. The submarine is powered by an 83 MW CLWR-B1 compact light water pressurised reactor derived from the prototype naval reactor at Kalpakkam, driving a single shaft with a seven-blade propeller. Speed is stated at 12 to 15 knots when surfaced and about 24 knots when submerged, with an endurance and range limited primarily by food stocks, crew rotation, and scheduled maintenance rather than fuel. The hull could be made using specialised low-carbon steel and, in some descriptions, anechoic tiles for acoustic damping, and it incorporates bow, flank, and towed array sonar fits. Once commissioned, INS Aridhaman is expected to be homeported at Rambilli near Visakhapatnam under the Eastern Naval Command, operating under the Strategic Forces Command within India’s nuclear command structure.

The missile and combat system of INS Aridhaman reflects a larger payload than earlier Arihant-class units, with eight vertical launch system (VLS) tubes in the raised hull section compared to four on INS Arihant and INS Arighaat. This arrangement allows the submarine to carry up to 24 K-15 Sagarika submarine-launched ballistic missiles, with a range of about 750 kilometers. Alternatively, the submarine can embark up to eight K-4 SLBMs, with ranges around 3,500 kilometers, and is widely expected to be compatible with future K-5 missiles, which are described as having a range between 5,000 and 6,000 kilometers. The K-15 can reach most targets in Pakistan from patrol areas close to the Indian coastline, while K-4 missiles offer coverage across the wider regional theatre, and K-5 is envisioned to provide longer reach into more distant strategic areas.

The INS Aridhaman also retains a set of six 533 mm torpedo tubes to launch heavyweight torpedoes such as the Varunastra, as well as certain cruise missiles or mines for self-protection and limited conventional strike roles. Its sensor fit includes the USHUS sonar, originally developed for Kilo-class submarines, and the Panchendriya unified sonar and tactical control system, which integrates passive, active, intercept, ranging, and underwater communication functions. These systems are complemented by submarine combat management systems intended to integrate navigation, fire control, and sonar information for submerged operations in the Indian Ocean Region.

Within India’s nuclear doctrine, which is based on credible minimum deterrence and a stated no-first-use policy, the Arihant-class is a family of four nuclear-powered ballistic missile submarines developed under the Advanced Technology Vessel (ATV) initiative, which has been valued at about ₹900 billion for the nuclear submarine effort and around ₹40 billion or about $470 million per submarine in earlier estimates. These submarines are described domestically as strategic strike nuclear submarines and, with the commissioning of INS Arihant in 2016, India became the first state outside the five permanent members of the UN Security Council to build and deploy an SSBN. The conceptual basis for a sea-based deterrent emerged after the 1971 Indo-Pakistani War, when the US carrier group Task Force 74 entered the Bay of Bengal, and a Soviet nuclear-armed submarine reportedly trailed it, highlighting for Indian leaders the strategic value of submarines able to carry nuclear weapons. Following the 1974 Smiling Buddha nuclear test, an internal feasibility study called Project 932 examined the potential for an indigenous nuclear propulsion system, and the nuclear submarine design effort later crystallised in the 1990s as the ATV.

Initially focused on nuclear-powered attack submarines, the project was reoriented toward ballistic missile submarines after India’s 1998 nuclear tests and the adoption of a no-first-use pledge, which emphasized a secure second strike capability. The prototype 83 MW light water reactor, designated S1, was installed at Kalpakkam, reached criticality in November 2003, and was declared operational in September 2006, providing the basis for the production reactors used in Arihant-class boats and a training facility for naval nuclear personnel. Industrial participation in the programme includes detailed engineering at Larsen and Toubro’s submarine design centre, control systems by Tata Power SED, and steam turbine packages from Walchandnagar Industries, with Hindustan Shipyard transferred to the Ministry of Defence in 2009 to support construction work.

The history of the Arihant-class reflects a gradual expansion of India’s SSBN fleet, with boats identified internally as S1 through S4*, followed by a planned S5-class. INS Arihant, designated S2 and SSBN 80, was laid down in 2004, launched on July 26, 2009, began sea and weapons trials in December 2014, completed a series of missile firings, including a K-4 test in March 2016, and was commissioned in August 2016 before completing its first deterrence patrol on November 5, 2018. INS Arighaat, designated S3 and SSBN 81, was laid down in 2009, launched on November 19, 2017, began sea trials in January 2018, completed trials around March 2021, and was formally commissioned on August 29, 2024, after upgrades and testing. INS Aridhaman, or S4, launched in November 2021, began sea trials in 2022, and has been assessed for commissioning at the end of 2025, while a fourth unit, codenamed S4*, with about 75 percent indigenous content and armed only with 3,500-kilometer-range K-4 missiles, was launched on October 16, 2024.

Earlier in the programme, internal discussions in 2007 led to a modification of the design to extend the hull by about 10 meters to accommodate four additional missile tubes on the larger variants S4 and S4*, ensuring a greater missile load without waiting for the follow-on S5 submarine. An additional S4* unit was sanctioned in 2012 to avoid production gaps before the new class, while planning has continued for three larger S5 SSBNs of around 13,500 tonnes displacement, carrying longer-range missiles beyond 5,000 kilometers. In parallel with SSBN construction, India has arranged for a further leased Russian Akula-class nuclear attack submarine, often called Chakra III, under a $3 billion, ten-year lease signed in 2019 and scheduled to deliver around 2028 with a displacement in the 12,770 to 13,800 tonne range. Project 77, a separate plan for six 10,000-tonne indigenous SSNs designed by the Navy’s Warship Design Bureau and built at Visakhapatnam, received Cabinet Committee on Security approval for two boats in October 2024, with design and construction timelines expected to span more than a decade.

As of December 2024, the Indian Navy operated more than 130 warships and 251 aircraft and helicopters, with goals of reaching 155 to 160 warships by 2030, between 175 and 200 by 2035, and up to 230 surface combatants and submarines by 2037. By September 22, 2025, there were 54 ships in various stages of construction, from early fabrication to sea trials, with around 10 of those planned to be commissioned within the same year, and contracts for these vessels were valued at about ₹99,500 crore (roughly $11.1 billion). The Defence Acquisition Council has accorded Acceptance of Necessity for 74 additional warships worth roughly ₹2.35 lakh crore ($26 billion), while the Ministry of Defence continues to clear further programmes, including a first batch of four 10,000-tonne next-generation destroyers and a future aircraft carrier. By October 31, 2025, the Navy had commissioned 10 warships and a submarine in that calendar year, with four more ships scheduled for delivery by December, corresponding to an induction rate of roughly one warship every 40 days.

In response to increased activity by the Chinese navy in the Indian Ocean Region, including submarines and surface deployments, India has invested in anti-submarine corvettes such as the Kamorta and Mahe classes, long-range P-8I maritime patrol aircraft, Saryu-class patrol vessels, and unmanned aerial vehicles like the Heron-1. Plans also include strengthening island infrastructure at the Andaman and Nicobar chain and Lakshadweep to create a network of air bases and logistics nodes that support freedom of navigation and overflight across the Arabian Sea and Bay of Bengal, while a Technology Perspective and Capability Roadmap published in September 2025 outlines an ambition for at least 10 nuclear propelled surface ships, including the proposed aircraft carrier INS Vishal.

Future submarine plans under the “Future of the Indian Navy” framework include three more Kalvari-class or modified Type 214 submarines under consideration, six Project 75I AIP equipped submarines based on an enlarged Type 214 design, and twelve Project 76 submarines equipped with AIP and tube launched land attack cruise missiles, with feasibility studies beginning in July 2024 and design and construction projected over the next decade. Additional undersea plans include at least five 150 tonne midget submarines intended for MARCOS special operations as swimmer delivery vehicles, a ₹2,500 crore project (roughly $278 million) for twelve extra large unmanned underwater vehicles over 100 tonnes with roles in ISR, anti submarine warfare, anti surface warfare, and mine warfare, and the Jalkapi XLUUV currently under construction in Halol, Gujarat, after a plate cutting ceremony on June 10, 2025.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.