The Advanced Technology Vessel Project (ATVP) under India's nuclear submarine program has initiated construction of the first two units of the S5-class SSBNs, marking a pivotal advancement in the nation's sea-based nuclear deterrence.

These submarines boast a displacement of approximately 13,500 tonnes submerged, rendering them roughly twice the size of the Arihant-class vessels, which displace around 6,000 to 7,000 tonnes. This substantial increase in size facilitates enhanced stealth, superior nuclear propulsion, and greater missile payload capacity.

The S5-class represents the pinnacle of India's indigenous SSBN evolution, designed to carry up to twelve or sixteen K-6 submarine-launched ballistic missiles (SLBMs), each equipped with multiple independently targetable re-entry vehicles (MIRVs).

The K-6 missile, under development by the Defence Research and Development Organisation (DRDO), offers an intercontinental range of 6,000 to 8,000 km, enabling submerged launches from deep ocean depths for maximum survivability. Such capabilities ensure a robust second-strike option, aligning with India's no-first-use nuclear doctrine.

Construction of the initial pair proceeds at the Ship Building Centre in Visakhapatnam, with Cochin Shipyard Limited upgrading its infrastructure, including dry docks, to accommodate these behemoths. 

The program enjoys direct oversight from the Prime Minister's Office, underscoring its strategic primacy amid Indo-Pacific tensions. Each S5 unit is projected to cost around ₹20,000 crore (approximately $2.4 billion), reflecting the complexity of integrating advanced sensors, quietened reactors, and MIRV technology.

The lead S5 submarine is slated for induction into the Indian Navy in the early 2030s, with subsequent units following in a phased rollout. Originally conceived as a six-boat class, the plan now focuses on four S5 SSBNs by the late 2030s, built in pairs to optimise resources and timelines. This fleet will form the core of India's underwater nuclear vigil, complementing existing platforms for continuous deterrence patrols.

Preceding the S5 is the S4* SSBN, ordered over a decade ago as an interim measure bridging the S4 (INS Aridhaman) and the larger S5 project. Launched in October 2024 with 75 per cent indigenous content, S4* carries K-4 SLBMs with a 3,500 km range, fired via vertical launch systems. It follows INS Arighaat's commissioning in August 2024 and precedes S4's expected handover in early 2026, with S4* itself targeted for service by mid-to-late 2026.

This sequence— Arihant (S2, 2016), Arighaat (S3, 2024), Aridhaman (S4, ~2026), S4* (~2026), and S5 series (2030s)—bolsters India's SSBN fleet from technology demonstrators to a mature deterrent force. 

The S4* variant, slightly modified from S4, enhances missile capacity and endurance, serving as a stopgap until the S5's superior displacement and weaponry mature. By the late 2030s, four S5s will anchor a credible sea-based triad leg, ensuring survivability against pre-emptive threats.

India's SSBN progression underscores self-reliance, with ATVP achieving over 75 per cent localisation in recent boats despite challenges like reactor miniaturisation and acoustic stealth.

Infrastructure expansions at Visakhapatnam and Cochin, coupled with DRDO's missile maturation, position the S5 as a counter to regional adversaries' naval expansions. Deep-sea trials of predecessors, such as S4*'s recent outings, validate the pathway to operational maturity.

IDN (With Agency Inputs)