India’s sea-based nuclear deterrent is advancing significantly with the reported commissioning of INS Aridhaman (S4) in April 2026 and the ongoing development of its successor, the S4*. The new platform is expected to achieve up to 90% indigenous content, marking a major leap in localization and signaling a shift toward greater self-reliance in strategic submarine development.
The Arihant-class program has progressively increased indigenous capability—from around 70% in INS Arihant (S2) to 75% in INS Arighaat (S3), and approximately 85% in INS Aridhaman (S4). The S4* is expected to further push this to near-total indigenization, reflecting a maturing domestic industrial ecosystem.
The S4* introduces both structural and technological enhancements. As a stretched variant of the Arihant-class, it is likely to feature greater displacement and increased missile capacity. The adoption of an X-shaped rudder improves maneuverability and hydrodynamic efficiency, particularly during low-speed stealth operations. Additionally, advancements in acoustic quieting—through improved propulsion, vibration isolation, and hull design—enhance survivability by reducing detectability.
This progress is underpinned by the expanding role of India’s domestic industry, with over 200 MSMEs contributing critical components such as specialized steel, electronics, and sonar systems. This shift reduces dependence on foreign suppliers while strengthening supply chain resilience.
With INS Aridhaman now operational, India’s ability to maintain continuous at-sea deterrence is reinforced. The upcoming S4* will further enhance the credibility and survivability of the nuclear triad. Moreover, the technological gains from this program are expected to feed into the next-generation S5-class submarines, which will likely be larger and more advanced. Overall, the rapid rise in indigenization within a single submarine class underscores India’s accelerating capability in strategic defense manufacturing.
