In a landmark development for Indian naval self-reliance, the nation’s fourth ballistic missile submarine (SSBN), designated as S4*, has begun its sea trials, setting a new benchmark in domestic defence production.
The vessel has achieved an indigenous content ratio of nearly 80 per cent, the highest figure recorded among the four nuclear-powered platforms developed under the Advanced Technology Vessel (ATV) programme to date.
This accomplishment underscores the increasing maturity of India’s industrial and scientific capabilities in the complex realm of nuclear submarine construction.
As the most advanced iteration of the Arihant-class lineage, the S4* incorporates significant design refinements derived from the operational experiences of its predecessors, INS Arihant and INS Arighat.
his latest platform features a "stretched" hull design, accommodating a larger weapons payload—specifically the 3,500-km range K-4 submarine-launched ballistic missiles (SLBMs)—which offers a substantial upgrade over the shorter-range K-15 missiles carried by earlier boats.
The high degree of indigenisation is evident across critical domains, including the hull fabrication, sophisticated onboard electronics, propulsion subsystems, and combat management suites.
By progressively reducing reliance on foreign imports, the S4* demonstrates marked improvements in system integration and reliability.
Looking beyond the current class, India is preparing for a quantum leap in capability with the S5 ballistic missile submarines.
These next-generation vessels are projected to displace approximately 13,500 tonnes—nearly double the size of the current fleet—and are expected to feature indigenous content exceeding 90 per cent.
Scheduled to enter service in the 2030s, the S5 class will likely be armed with K-6 intercontinental SLBMs, forming the core of India’s sea-based nuclear deterrence.
The shift towards such high levels of localisation signals a growing confidence in the domestic design and manufacturing of large-scale, endurance-focused nuclear platforms.
Simultaneously, the Indian Navy is pursuing an equally ambitious roadmap for its non-strategic nuclear fleet under Project-77.
This programme, aimed at constructing nuclear-powered attack submarines (SSNs), has set a target of 95 per cent indigenous content for its initial vessels.
Recent reports suggest these SSNs may displace around 10,000 tonnes and could feature advanced "mothership" capabilities for deploying unmanned underwater vehicles (UUVs).
Achieving this level of self-sufficiency would position India within an elite tier of nations capable of executing almost the entire nuclear submarine supply chain domestically.
The progression from the S4*’s successful indigenisation to the lofty targets set for the S5 and Project-77 programmes illustrates a decisive strategic shift.
India is steadily moving from a phase of selective self-reliance to near-total sovereignty in underwater warfare technology.
This trajectory not only strengthens the nation’s credible strategic deterrence but also secures its long-term autonomy in navigating the geopolitical complexities of the Indo-Pacific region.
