The Indian Navy’s Kalvari-class submarines under Project-75 are set to receive Air Independent Propulsion (AIP) systems, a technology designed to enhance their underwater endurance. This follows a steel-cutting ceremony held on December 28, 2024, marking progress in integrating the domestically developed system.
The AIP system, developed by the Defense Research and Development Organisation (DRDO) in collaboration with Larsen & Toubro (L&T), is expected to be tested and built by the end of 2025 at the AM Naik Heavy Engineering Complex. It will be installed on the INS Kalvari during its scheduled refit in September 2025 at Mazagaon Dockyard Limited (MDL).
DRDO and L&T signed a contract in June 2023 to supply two AIP modules for the Kalvari-class submarines. The fuel cell-based AIP was developed by DRDO’s Naval Materials Research Laboratory, with L&T as the industrial partner.
The integration process involves cutting the submarine into two halves to install the AIP module, a procedure expected to increase the submarine’s length and weight. The French Naval Group, which designed the Scorpene-class submarines, will oversee the integration process. The INS Kalvari will serve as a test platform for the system before it is implemented across the submarine fleet.
While experts have noted that retrofitting the submarines could temporarily affect operational readiness, the system is projected to significantly enhance the Navy’s underwater capabilities once fully integrated.
The AIP system represents a significant step in advancing domestic defense technology, with the INS Kalvari set to become the first Indian submarine to be equipped with this capability.