In a landmark step for India’s naval indigenisation drive, the Indian Navy will begin integrating its first indigenous Air-Independent Propulsion (AIP) system into the Kalvari-class submarine INS Khanderi during its scheduled refit in July 2026, defence sources confirmed.
Developed by the Defence Research and Development Organisation (DRDO) with support from Larsen & Toubro (L&T) and Thermax, the AIP system represents a major leap in undersea warfare technology, enabling conventional submarines to stay submerged for weeks without surfacing or snorkeling to recharge batteries.
The prototype is expected to be ready by December 2025, with sea trials scheduled for early 2027. Following successful validation, the system will be retrofitted on other Scorpene-class submarines and built into all future conventional submarines under upcoming projects.
Unlike foreign AIP systems, India’s design uses hydrogen-on-demand technology, generating hydrogen inside the submarine instead of storing it, enhancing safety and simplifying logistics. Based on fuel cell technology, the system also produces water as a by-product, making it both sustainable and environmentally friendly.
Defence experts say the indigenous AIP will act as a “force multiplier”, significantly boosting stealth, endurance, and combat effectiveness, while reducing reliance on costly nuclear propulsion. With this integration, India will join an elite group of nations, including Germany, France, and Japan, that have mastered AIP technology.
The Navy considers the project critical to countering increasing submarine activity by regional adversaries in the Indian Ocean Region (IOR). Officials have emphasised that timely execution will be key, as stealth and sustained underwater presence are central to India’s maritime deterrence.
