India weighs 3 more Scorpene submarines as Project-75(I) moves closer to approval

India is pursuing a two-track expansion of its conventional submarine fleet, with the government considering three additional Scorpene-class submarines while the larger Project-75(I) programme for six advanced boats moves towards final approval.

Defence Secretary Rajesh Kumar Singh said both proposals are under consideration, with Project-75(I) at a more advanced stage. The six-submarine programme has been submitted for a final decision by the competent authority, while the additional Scorpene proposal remains at an earlier stage.

The proposed three additional Scorpene submarines would extend the Kalvari-class line already being built at Mazagon Dock Limited (MDL), Mumbai. The move would provide another avenue for expanding the Navy’s conventional submarine fleet alongside the larger Project-75(I) programme.

Project-75(I), meanwhile, envisages six advanced diesel-electric attack submarines to be constructed in India under a strategic partnership with Germany’s Thyssenkrupp Marine Systems (TKMS). The programme is estimated to involve an investment of more than ₹80,000 crore and is expected to include substantial participation from Indian private-sector companies.

The submarines are planned to feature advanced sensors, weapons, stealth capabilities and Air Independent Propulsion (AIP).

AIP upgrade for existing fleet

Alongside new submarine construction, the Navy is working to improve the capabilities of submarines already in service.

The Defence Research and Development Organisation (DRDO) has developed an indigenous AIP system, which the Navy plans to install on one of its Scorpene-class submarines during a mid-life refit. Singh said the installation is expected to take place when the submarine undergoes a refit around the middle of next year.\

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AIP technology allows conventional submarines to remain submerged for longer periods without surfacing, enhancing their underwater endurance.

The planned integration of the indigenous system would add a domestic technology component to the existing Scorpene fleet while the Navy pursues new submarine construction.

Indigenous combat system also planned

The modernisation effort extends beyond propulsion. The Naval Physical and Oceanographic Laboratory (NPOL) has developed an indigenous integrated combat system for submarines.

According to Singh, the system will be progressively installed across the submarine fleet as vessels undergo refits. The system is part of the Navy’s broader effort to introduce indigenous technologies into existing platforms.

Regional submarine capabilities

The parallel focus on new construction and upgrades comes as India monitors developments in the regional underwater fleet. Pakistan is progressing with the induction of Hangor-class submarines, based on Chinese design and built with Chinese assistance.

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For India, the proposed additional Scorpenes would build on an existing submarine production line, while Project-75(I) would introduce a separate class of advanced conventional submarines through a German-Indian partnership.

The combination of new construction, AIP integration and an indigenous combat system represents multiple lines of effort to expand and upgrade India’s conventional underwater capabilities. The immediate decision point is Project-75(I), while the additional Scorpene proposal remains under consideration.