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In a major boost to India’s maritime strategic capabilities, construction work for the country’s next-generation S5 nuclear-powered ballistic missile submarine (SSBN) has officially commenced.
The S5, which will form the backbone of India’s future sea-based nuclear deterrence, is being built at the same Ship Building Centre (SBC) complex that previously delivered the Arihant-class follow-on vessels, often referred to as the S-4 and S-4* platforms.
According to defence sources, this development marks a dual-track evolution in India’s underwater naval power.
While the massive S5 SSBN takes shape at the legacy manufacturing site, a parallel infrastructure shift is underway to support the highly anticipated Project-77 programme.
This separate initiative focuses on building a fleet of nuclear-powered attack submarines (SSNs) designed for hunter-killer roles rather than strategic nuclear launches.
State-of-the-Art Infrastructure for Attack Submarines
Although the S5 is under construction at the established facility, the production of the Project-77 SSNs will be headquartered at a newly completed dry dock that became operational in 2025.Sources familiar with the project indicate that formal construction of the SSNs has not yet begun, but the new facility is fully prepped for the task.
This modern dock is engineered to handle larger hulls and significantly more complex integration workflows, aligning with the finalised designs of the Project-77 boats.
These attack submarines are expected to displace approximately 10,000 tonnes, placing them in a far superior capability bracket compared to earlier indigenous nuclear submarines.
Open-source information suggests that while the S5 SSBNs are likely to displace over 13,000 tonnes to accommodate long-range K-6 ballistic missiles, the Project-77 SSNs are optimised for speed and stealth.
The new facility’s capacity is a strategic asset in itself; sources have revealed that it can accommodate the simultaneous construction of up to three submarines.
This provides the Indian Navy with the "headroom" to expand production in the future without requiring further heavy infrastructure investment, even though current government approvals cover only the first two boats.
Optimised Production and Strategic Continuity
The Project-77 programme is structured to ensure a continuous industrial output.The plan involves the simultaneous construction of two submarines with a calculated offset of a few months between their start dates. This staggering is designed to optimise the use of the workforce and industrial resources.
The Indian Navy has a stated requirement for six SSNs to perform "blue-water" operations, including escorting carrier battle groups and conducting long-endurance stealth patrols in the Indian Ocean Region (IOR).
The production strategy is divided into batches: the first two SSNs will be nearly identical in configuration, while the subsequent pair will feature upgraded systems.
Crucially, planners aim to eliminate any "production gap" by commencing the second batch immediately as the initial submarines near completion.
Advanced Propulsion and Testing Protocols
A key technological leap for both programmes is the propulsion system.The S5 SSBN is set to be powered by a new 190 MW pressurised light-water reactor (PWR), offering the unlimited endurance required for months-long deterrence patrols.
While the Project-77 SSNs will utilise a reactor derived from this same 190 MW core, the engineering will be tuned differently.
Attack submarines require high "burst power" to chase targets or evade threats at high speeds—a distinct operational profile from the slow, silent patrolling of an SSBN.
Consequently, the power management systems on the SSNs will be adapted to handle rapid changes in speed and agile manoeuvring.
Following standard submarine building protocols, once the hull fabrication is complete, the vessels will be transferred to an outer dock for the final integration phase.
This involves the precise installation of combat sensors, weaponry (such as torpedoes and cruise missiles), and auxiliary machinery.
Following reactor activation, the submarines will undergo rigorous harbour trials and sea trials to validate their acoustic stealth and propulsion performance before being commissioned into the Indian Navy.
