Indian Navy's first AIP-equipped submarine to be ready by year-end

Second of six operational Kalvari submarines to become first in class to be fitted with endurance- and stealth-enhancing technology

The Indian Navy’s first submarine equipped with advanced technology to enhance its underwater endurance and stealth is expected to be ready by the end of 2026, when the second of the six French-origin Kalvari (Scorpene)-class submarines in its fleet will have been fitted with an indigenous air-independent propulsion (AIP) system, a defence source told Business Standard on Friday.

 

Between December 2017 and January 2025, six Kalvari-class conventional diesel-electric attack submarines were commissioned into service. The vessels were built by the state-run Mazagon Dock Shipbuilders Ltd (MDL) under a transfer-of-technology arrangement with France’s Naval Group.

 

“The first submarine is already undergoing refit and will therefore not be fitted with an AIP system at present. The second vessel, however, will enter refit in the middle of the year and will become the first submarine in Indian service to be equipped with this technology,” said the source.

 

 

The AIP system will be installed by cutting open the submarine’s hull and “plugging in” a section that will house the technology.

 

“If all goes to plan, this process should be completed by the year-end, after which the system and the submarine will undergo trials,” the source added.

 

AIP is a technology that allows conventional submarines to generate power underwater without surfacing or using a snorkel to draw in air. By enabling the vessel to remain submerged for much longer periods, it enhances underwater endurance, stealth and survivability.

 

The “energy unit”, which will constitute the AIP once fitted onto the submarine, is expected to be delivered to MDL in about three months, another defence source said. MDL will be responsible for integrating the AIP plug onto the vessel.

 

The AIP system has been developed indigenously by the Defence Research & Development Organisation (DRDO), with Larsen & Toubro (L&T) as the development-cum-production partner.

 

Under the Project 75 India (P75I) programme, MDL will also build six advanced conventional submarines with technology transfer from its partner, the German firm ThyssenKrupp Marine Systems (TKMS). The submarines, designed by TKMS to meet Indian requirements, will be equipped with similar endurance-enhancing technology. These vessels, however, will be fitted with a German AIP system. The signing of the P75I contract is expected by the end of March.