India’s strategic submarine modernization effort may ultimately produce four S-5 class ballistic missile submarines in its first production tranche rather than the six boats originally envisioned, as naval planners reportedly weigh the development of a larger successor design later in the next decade.
Defence sources suggest that construction of the first S-5 submarine officially began in late 2025 with steel-cutting activities at Visakhapatnam’s Shipbuilding Centre. To accelerate the program, the government has reportedly approved parallel construction of the first two vessels, ensuring production momentum and shortening induction timelines.
Although the S-5 program was initially associated with a six-submarine fleet, current planning appears focused on a confirmed four-boat batch, with provisions for additional units if future strategic needs demand expansion. At approximately 13,500 tons submerged displacement, the S-5 will be significantly larger than the Arihant-class and represent a major leap in India’s sea-based deterrence capabilities.
The revised force structure is thought to reflect confidence in the expanded Arihant variants already entering service. These submarines were designed to serve as an interim capability before the arrival of the S-5 class, leading the Navy to conclude that four advanced S-5 submarines may be sufficient to maintain uninterrupted deterrent patrols while older boats transition into support, training, and reserve roles.
Beyond the current program, defence planners are reportedly examining two possible paths for the future. The first involves an enlarged “S-5 Plus” design approaching 17,000 tons, featuring enhanced endurance, greater missile payload capacity, improved quieting technologies, and more powerful reactor systems. The second option centers on an all-new S-6 class optimized around advanced propulsion technologies, larger missile sections, next-generation stealth features, and future intercontinental-range ballistic missiles.
Depending on strategic requirements through the 2040s and beyond, the future follow-on program could produce between two and four additional submarines. For now, however, the Indian Navy remains focused on bringing the first S-5 into operational service by the mid-2030s. Once inducted, the class is expected to serve as the backbone of India’s nuclear triad, carrying long-range K-series SLBMs and providing a highly survivable second-strike capability from the depths of the Indian Ocean.
