India has reached an important milestone in developing its indigenous Air Independent Propulsion (AIP) system for conventional submarines, with the inauguration of the Setting to Work Phase-2 (STW-2) activity. The programme is intended to enhance the underwater endurance and operational effectiveness of the Indian Navy’s diesel-electric submarine fleet. Developed by the Naval Materials Research Laboratory (NMRL) under the Defence Research and Development Organisation (DRDO), the AIP Energy Module is designed to reduce conventional submarines’ dependence on atmospheric oxygen. This would allow them to remain submerged for longer periods without surfacing or using a snorkel to recharge their batteries. The STW-2 inauguration took place at Larsen and Toubro’s AM Naik Heavy Engineering Complex in Hazira, Gujarat. Defence Secretary Rajesh Kumar Singh, who also serves as DRDO Chairman and Secretary of the Department of Defence Research and Development, attended virtually as the chief guest. Senior officials present at the facility included Vice Admiral B. Sivakumar, Chief of Materiel of the Indian Navy, and DRDO Director General (Naval Systems and Materials) R. Balamuralikrishnan. The next stage will involve energising the AIP Energy Module to generate power and conducting rigorous tests according to Indian Navy protocols. Following successful validation, the system is expected to be handed over to Mazagon Dock Shipbuilders Limited for installation in a Kalvari-class submarine in early 2027. The integration is expected to improve the capabilities of India’s Scorpene-class submarine fleet. Conventional diesel-electric submarines depend on batteries while submerged and must periodically approach the surface to recharge using diesel generators. AIP technology addresses this limitation by enabling power generation underwater, reducing the need to surface and lowering the risk of detection. At the event, Singh congratulated DRDO and its industrial partners for translating years of development into practical engineering progress. He acknowledged the Indian Navy’s continued involvement in testing and validating the system and stressed the importance of maintaining programme momentum to meet the planned induction schedule. He also highlighted the stringent safety requirements associated with hydrogen and fuel-cell technologies. The project reflects India’s broader drive to achieve self-reliance in critical naval technologies. Once operational, the indigenous AIP system is expected to improve submarine stealth, surveillance and deterrence capabilities across the Indian Ocean Region by allowing longer submerged deployments.
