Arihant-class submarine

The Arihant‑class submarine is India’s first indigenously designed and built nuclear‑powered ballistic‑missile platform, providing the nation with a sea‑based second‑strike capability. Centered on the lead vessel INS Arihant (S71), the class integrates a domestically produced pressurised‑water reactor with vertical launch tubes for submarine‑launched ballistic missiles (SLBMs), marking a decisive step toward strategic autonomy in the Indian Navy.

Origins and Development

The programme was launched in 1997 under the Integrated Guided Missile Development Programme (IGMDP), with the Defence Research and Development Organisation (DRDO) and the Naval Design Bureau (NDB) tasked to create a nuclear‑propulsion system free of foreign technology. The keel of INS Arihant was laid at the Shipbuilding Centre in Visakhapatnam on 16 January 2004, and the submarine was launched on 26 July 2009 by then‑Prime Minister Manmohan Singh.

Funding for the project was allocated through the Ministry of Defence’s “Strategic Nuclear Forces” budget, with an estimated cost of ₹ 15,000 crore (≈ US $2 billion) for the first three vessels. Dr. A. P. J. Kalam, then Scientific Advisor to the Prime Minister, championed the effort, emphasizing the need for an indigenous nuclear propulsion capability to avoid dependence on external suppliers.

Design and Propulsion

Arihant‑class hulls measure 110 m in length, 13.4 m in beam, and displace roughly 6,000 tonnes when submerged. The heart of the vessel is a 16 MW pressurised‑water reactor (PWR) designed and built by the Bhabha Atomic Research Centre (BARC), delivering enough power for a sustained submerged speed of 12–15 knots and an endurance limited only by crew provisions rather than fuel.

The reactor’s primary loop feeds steam to a turbine‑generator set that drives a single propeller shaft, producing about 30,000 shp (shaft horsepower). The nuclear plant is housed in a double‑hull compartment with extensive radiation shielding, allowing the submarine to operate for up to 20 years without refuelling—a hallmark of true SSBN capability.

Armament and Missile Capability

Each Arihant‑class boat is equipped with twelve vertical launch tubes capable of housing the K‑15 Sagarika SLBM, a two‑stage solid‑fuel missile with a range of 750 km and a payload of up to 1,000 kg. The class was designed from the outset to accommodate the longer‑range K‑4 missile (≈ 3,500 km) and the forthcoming K‑5 (≈ 5,500 km), which will expand India’s deterrent reach to the entire Indo‑Pacific region.

In addition to its strategic payload, the submarine carries a complement of torpedoes and anti‑ship missiles launched from its bow tubes, enabling conventional surface‑warfare roles when required. The fire‑control system, supplied by the DRDO’s Naval Systems Division, integrates inertial navigation with satellite‑aided updates to ensure precise targeting of SLBMs from submerged depths of up to 300 m.

Operational History and Current Status

INS Arihant entered active service on 10 July 2016 after a series of sea‑trials that demonstrated successful reactor start‑up, submerged endurance, and a live K‑15 missile launch on 30 May 2018. The vessel has since participated in the Indian Navy’s “Jagaran” and “Vijay” exercises, showcasing its ability to operate alongside surface combatants and allied navies.

The second boat, INS Arighat (S72), was launched on 28 July 2017 and began dockyard trials in 2021; as of 2024 it is undergoing integrated system trials with an expected commissioning by late 2025. A third SSBN, still unnamed, is under construction at the same shipyard, with a projected entry into service by 2028. The Navy’s long‑term plan calls for a fleet of four to six Arihant‑class submarines by 2030, complemented by the development of the K‑5 missile.

Strategic Significance

By fielding a nuclear‑powered ballistic‑missile submarine, India joins an exclusive club of seven nations—United States, Russia, United Kingdom, France, China, and now India—that possess a survivable sea‑based nuclear deterrent. The Arihant‑class provides a credible second‑strike option, reinforcing the doctrine of “no‑first‑use” and contributing to strategic stability in the Indo‑Pacific.

Beyond deterrence, the programme demonstrates India’s capacity to design, fabricate, and operate complex nuclear propulsion systems without external assistance, a milestone that bolsters indigenous defence‑industrial capabilities and signals a maturing technological base to both allies and rivals.