All six Kalvari class Scorpene submarines being acquired for the Indian Navy under the ongoing Project 75 will be retrofitted with an indigenous Air Independent Propulsion (AIP) system during programmed refit for each of these submarines.

The AIP is being developed by the Defence Research and Development Organisation (DRDO), and the submarine OEM, the French Naval Group is assisting the DRDO in platform redesign to enable a plug-in integration of the AIP.

India had earlier turned down a French offer for the Mesma AIP for fitment on the fifth and sixth submarines during the construction process.

India had earlier turned down a French offer for the Mesma AIP for fitment on the fifth and sixth submarines during the construction process

"We believe the AIP developed by the DRDO is a very good system based on sound technologies. We are closely working with DRDO to make this project a success and integrate it with Project 75 submarines during their refits," Rear Admiral RK Shrawat (Retired), chairman and managing director of Naval Group India Private Limited confirmed to this reporter.

The AIP will significantly enhance the underwater endurance of the Indian Navy's Kalvari class Scorpene submarines, manufactured at Mazagon Dock Limited (MDL), Mumbai, under transfer of technology from the Naval Group (earlier DCNS).

"We believe the AIP developed by the DRDO is a very good system based on sound technologies. We are closely working with DRDO to make this project a success and integrate it with Project 75 submarines during their refits," Rear Admiral RK Shrawat (Retired), chairman and managing director of Naval Group India Private Limited confirmed

The first of these submarines - Kalvari - is already in operational service. The second, Khanderi, is set to be commissioned shortly. The third and fourth submarines have been launched.

Besides the DRDO and the Naval Group, MDL and the Indian Navy are also closely involved in integrating the AIP.

A design study for the retrofitment of the DRDO AIP on to the Indian Navy Scorpenes is underway.

The Indian Navy is reported to be seeking enhanced capabilities for the next line of conventional submarines which will be acquired under Project 75 (I). Among the features sought are an AIP and more potent sonars and weapons, including longer-range submarine-launched land-attack missiles. The tonnage of the new submarine will also be higher at 2000 tons. The Scorpene class is in the 1,500 ton class. India is also seeking 50 per cent indigenisation in Project 75(I), as compared with 30 per cent in the sixth and last submarine under the ongoing Project 75.