L&T To Build Two AIP Modules For Kalvari Class Submarines, Receives Technology From DRDO

Larsen and Toubro (L&T) and Defence Research and Development Organisation (DRDO) have signed a deal to manufacture two Air Independent Propulsion (AIP) modules for the Indian Navy's Kalvari class submarines.

The AIP modules has been designed by the Naval Materials Research Laboratory (NMRL), a DRDO lab. NMRL will transfer the technology to manufacture these AIP modules to L&T.

Earlier in January 2023, NMRL and France's Naval Group had signed an agreement for the integration of this AIP system on INS Kalvari.

"The addition of these green AIP Module in submarines is believed to add India to the club of a handful of nations who have indigeneously developed the fuel cell based AIP System," Arun T Ramchandani, executive vice president of L&T, said. 

NMRL will start integrating these AIP modules on Kalvari class submarines in 2024, when INS Kalvari goes for a refit.

The process of integration will involve cutting the submarine hull in half, after which the hull will be welded back with the AIP sections in between. 

Air Independent Propulsion System

An AIP system gives a submarine the ability to remain submerged underwater, away from enemy sensors, for a long time without surfacing.

A diesel-electric submarine, not equipped with an AIP, has to snorkel frequently to recharge its batteries which power its propellers and other equipment.

The process of snorkelling involves travelling just below the surface of the water, with the submarine’s periscope and generator exhaust pipe above the surface.

An AIP system reduces the need for snorkelling by enabling it to generate electricity for charging its batteries, while completely submerged.

NMRL successfully conducted trials of the land-based prototype of the AIP system in March 2021.