VISAKHAPATNAM, — April 3, 2026 : India on Friday commissioned its third nuclear-powered ballistic missile submarine (SSBN), INS Aridhaman, into the Indian Navy at a ceremony held in Visakhapatnam and presided over by Defence Minister Rajnath Singh. The induction marks a continued expansion of India’s sea-based nuclear deterrent and strengthens the maritime leg of its nuclear triad.
The submarine, designated S4 under the classified Advanced Technology Vessel (ATV) program, is the third vessel in the Arihant-class series and the first of an enlarged subclass with improved design and capabilities. Its commissioning coincided with the induction of the stealth frigate INS Taragiri, reflecting ongoing efforts by the Ministry of Defence to expand naval capacity through indigenous platforms.
Platform Development and Construction
INS Aridhaman was constructed at the Ship Building Centre (SBC), Visakhapatnam, with fabrication support from Larsen & Toubro. The keel was laid around 2018, and the submarine was launched on November 23, 2021. It completed its sea trials by late 2025 before being cleared for operational service.
The vessel has a displacement of approximately 7,000 tonnes, making it larger than earlier Arihant-class submarines such as INS Arihant and INS Arighaat, which displace around 6,000 tonnes. It measures about 130 metres in length with a beam of 11 metres and incorporates a more streamlined hull design aimed at improving hydrodynamic efficiency and reducing acoustic signature.
Propulsion and Performance
The submarine is powered by an 83 MW Compact Light Water Reactor, an upgraded pressurised water reactor developed by the Bhabha Atomic Research Centre (BARC). The reactor enables extended submerged endurance and contributes to lower detectability compared to earlier configurations.
INS Aridhaman is fitted with a seven-blade propeller and is capable of speeds ranging from 12 to 15 knots on the surface and up to 24 knots when submerged. The nuclear propulsion system allows the submarine to remain underwater for prolonged periods without surfacing, enhancing operational survivability.
Armament and Combat Systems
The submarine is equipped with eight vertical launch system (VLS) tubes located in its missile compartment, doubling the missile capacity compared to earlier boats in the class.
It can carry:
- Up to 24 K-15 (Sagarika) submarine-launched ballistic missiles (SLBMs) with a range of 750 km, or
- Up to 8 K-4 SLBMs with a range of approximately 3,500 km
The platform has also been designed to integrate future K-5 SLBMs, which are currently under development and expected to have a range of around 6,000 km.
In addition to ballistic missile capability, INS Aridhaman is fitted with six 533 mm torpedo tubes and is estimated to carry up to 30 munitions, including torpedoes, cruise missiles, or naval mines.
The submarine is equipped with indigenous sensor and combat systems, including the USHUS integrated sonar suite and the Panchendriya unified submarine control and underwater communication system.
Operational Role and Basing
INS Aridhaman will operate under India’s Strategic Forces Command and is expected to be based at Project Varsha, a high-security naval facility with underground submarine pens near Visakhapatnam.
With the induction of the third SSBN, the Indian Navy improves its ability to maintain continuous at-sea deterrence, ensuring that at least one nuclear-armed submarine remains on patrol while others undergo maintenance or transit.
Fleet Integration and Strategic Context
INS Aridhaman joins INS Arihant (commissioned in 2016) and INS Arighaat (inducted on August 29, 2024). This marks the first time India operates three Arihant-class SSBNs simultaneously.
India remains among a limited group of countries operating nuclear-powered submarines, alongside the United States, Russia, China, the United Kingdom, and France.
A fourth submarine of similar configuration, expected to be named INS Arisudan, is currently under construction and is projected to enter service around 2027. In parallel, India is progressing toward the development of the next-generation S5-class submarines, expected to displace around 14,000 tonnes.
Concurrent Commissioning of INS Taragiri
Alongside INS Aridhaman, the Indian Navy commissioned INS Taragiri, an advanced stealth frigate built by Mazagon Dock Shipbuilders Limited (MDL) under Project 17A.
The 6,670-tonne frigate is equipped with a Combined Diesel or Gas (CODOG) propulsion system and features a modern weapons suite, including supersonic surface-to-surface missiles and medium-range surface-to-air missile systems.
Program Continuity
Officials indicated that the expanded missile capacity, improved propulsion system, and reduced acoustic signature of INS Aridhaman contribute to strengthening the credibility of India’s sea-based deterrent. Development work under the ATV program continues at the Ship Building Centre as part of India’s long-term indigenous submarine construction roadmap.
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