India is set to achieve a significant milestone in indigenous submarine technology as the Defence Research and Development Organisation's (DRDO) fuel-cell-based Air Independent Propulsion (AIP) system is scheduled to be installed on INS Khanderi during its refit at Mazagon Dock Shipbuilders Ltd in mid-2027.

Defence Secretary Rajesh Kumar Singh said the upgraded submarine is expected to begin sea trials during July-August 2027, with induction into operational service targeted for 2028.

INS Khanderi, the second submarine of the Indian Navy's Kalvari-class fleet, will be the first vessel to receive the indigenous AIP system. The integration process will involve substantial modifications, including the installation of an AIP module during the submarine's refit program.

Developed by DRDO's Naval Materials Research Laboratory, the fuel-cell-based AIP technology enables a conventional diesel-electric submarine to generate power while remaining submerged. This reduces the need to surface or use a snorkel for battery charging, significantly enhancing stealth, survivability and underwater endurance.

The indigenous system is considered a major step towards strengthening India's self-reliance in advanced underwater warfare technologies. It is expected to allow Kalvari-class submarines to remain underwater for far longer periods compared with conventional diesel-electric configurations, reducing detection risks during operational deployments.

The AIP integration program is being undertaken at Mazagon Dock Shipbuilders Ltd, which secured a Ministry of Defence contract worth approximately ₹1,990 crore for constructing and integrating the AIP plug into Kalvari-class submarines.

The technology was initially intended for INS Kalvari, the lead submarine of the class, but development timelines resulted in INS Khanderi being selected as the first platform for operational integration. 

Successful sea trials in 2027 will pave the way for the wider adoption of indigenous AIP technology across India's conventional submarine fleet.

The project marks an important advance in India's long-term effort to enhance underwater combat capabilities and reduce dependence on imported propulsion technologies.

Agencies