The Indian INS Kalvari submarine, which is currently docked in Mazagon for its first refit, will be cut open and another 10-meter Fuel Cell based Air Independent Propulsion (AIP) System will be added, which will necessitate the installation of new wires and other systems before it can be wielded back into the submarine.

Naval Group, the OEM of the Kalvari Class submarine, was unwilling to become a technical consultant in the programme, so plans to incorporate it into the fifth and sixth submarines were scrapped.

The Indian Navy was concerned that the Naval Group would overlook the integration of this programme because DRDO has little experience integrating such systems into existing submarines. The recent agreement brings Naval Group on board this programme and allows it to collaborate with the DRDO on the integration of an AIP module designed in India.

The AIP plug will increase the length of the Kalvari-class to 77,56 metres and will increase its displacement by 1000kg that will bring its submerged displacement to 1875-tons.