Mazagon Dock, Naval Group Sign ToT Agreement for Kalvari-Class Submarine Upgrades

24 Jul 2025 , 01:48 PM

Mazagon Dock Shipbuilders Ltd (MDL), the state-owned defence shipyard, has entered into a formal agreement with France’s Naval Group for the transfer of technology (ToT) to install indigenous energy system plugs on Indian Navy’s Kalvari-class submarines.

In a statement dated July 23, the company confirmed that the integration will use a combination of technology developed by the Defence Research and Development Organisation (DRDO) and proprietary submarine architecture from Naval Group, the original manufacturer of the Scorpene-class platforms.

The modification process, known in naval engineering as “jumboisation”, involves precision cutting of the submarine’s hull, inserting the custom-built energy plug, and reassembling the structure with exacting accuracy to ensure that the platform remains fully operational post-upgrade.

Naval Group will provide technical guidance, specialised training, and critical components for the upgrade, while MDL will lead the integration effort on Indian soil.

“We are pleased to extend our natural partnership with Naval Group. Together, we will work on integrating the DRDO-developed propulsion system into the Scorpene submarines of Project 75,” said S.B. Jamgaonkar, Director of the Submarines Division at MDL.

The agreement follows two major defence contracts signed by the Ministry of Defence in December 2024, aimed at improving submarine capabilities.

• The first, worth ₹1,990 crore, was awarded to MDL for the construction and integration of Air Independent Propulsion (AIP) system plugs.
• The second, valued at ₹877 crore, was signed with Naval Group for the incorporation of an electronic heavyweight torpedo (EHWT) system, developed in collaboration with DRDO.

Combined, these initiatives represent a significant leap in India’s effort to indigenise critical defence technologies and extend the service life and underwater endurance of its conventional submarines.

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