P-75 I (or P-7 5. India) project refers to manufacture of

Project 75 India (P-75I) is a major military acquisition initiative by the Indian Ministry of Defence aimed at procuring six advanced conventional diesel-electric attack submarines for the Indian Navy [2]. As a follow-on to the Kalvari-class (Project 75) program, P-75I focuses on building these vessels locally under the 'Make in India' strategic partnership model. A defining technical requirement of this project is the integration of fuel cell-based Air-Independent Propulsion (AIP) technology. This system allows diesel-electric submarines to remain submerged for significantly longer periods—up to two weeks—without needing to surface to recharge batteries, thereby enhancing their stealth and operational endurance. The project aims to replace the aging Sindhughosh-class fleet and strengthen India's undersea deterrence in the Indian Ocean Region [2].

Sources

1. [2] https://en.wikipedia.org/wiki/Project-75_(India)_submarine_acquisition_project