India to install indigenous AIP system on INS Khanderi

India will retrofit INS Khanderi, the second Kalvari-class submarine, with an indigenous Air-Independent Propulsion system developed by DRDO by December. Fuel-cell based module will allow submarine to remain underwater for weeks without surfacing, improving stealth. Sea trials are expected in mid-2027 with full refit completion by early 2028, marking a major milestone in India's submarine tech.