India Advances Project-75(I) and Submarine Modernisation Plans to Strengthen Underwater Warfare Capability

India’s efforts to expand its conventional submarine fleet are progressing with the Project-75(I) programme moving towards the final decision stage, according to Defence Secretary Rajesh Kumar Singh.

Under Project-75(I), six advanced conventional submarines are planned to be built in India under the Strategic Partnership model. The programme includes significant indigenous content, technology transfer and participation of Indian defence industries.

The project is being pursued with Germany’s ThyssenKrupp Marine Systems (TKMS) as the foreign technology partner, along with Indian shipbuilder Mazagon Dock Shipbuilders Limited (MDL). The submarines are expected to enhance the Indian Navy’s underwater endurance, surveillance and strike capabilities.

Additional Kalvari-Class Submarines Under Consideration

Alongside Project-75(I), India is also considering the construction of additional Kalvari-class submarine submarines through Mazagon Dock Shipbuilders.

The additional boats would build upon the experience gained from the existing Kalvari-class submarine programme, which involved technology cooperation with France and domestic construction at MDL.

The expansion of the fleet is aimed at maintaining submarine availability while new-generation platforms under Project-75(I) enter service.

Indigenous Air Independent Propulsion System to Improve Endurance

India is also working to enhance the operational capability of its existing conventional submarines through indigenous technologies.

The Defence Secretary highlighted plans to integrate the indigenous Air Independent Propulsion (AIP) system developed by the Defence Research and Development Organisation (DRDO) into Kalvari-class submarines during future refits.

AIP technology allows conventional submarines to remain submerged for longer periods without depending only on diesel-electric propulsion, improving stealth and operational flexibility.

Indigenous Combat Systems to Upgrade Submarine Fleet

India is also developing advanced submarine combat capabilities through indigenous systems.

The Naval Physical and Oceanographic Laboratory (NPOL), a DRDO laboratory, has developed an indigenous integrated combat system for submarines. The system is planned for gradual integration across submarines undergoing future refits.

The move is part of a broader effort to increase indigenous content in naval platforms, reduce dependence on imported technologies and strengthen India’s underwater warfare ecosystem.

Expanding Domestic Submarine Manufacturing Ecosystem

The submarine programmes are expected to create opportunities for Indian public and private-sector companies in areas such as shipbuilding, electronics, sensors, propulsion systems and underwater technologies.

With Project-75(I), additional Kalvari-class submarines, indigenous AIP technology and locally developed combat systems, India is building a multi-layered approach to modernise its underwater fleet and strengthen domestic naval manufacturing capability.

---

References

• Ministry of Defence, Government of India — Updates on Project-75(I), Strategic Partnership Model and submarine modernisation initiatives
• Defence Secretary Rajesh Kumar Singh’s remarks on Project-75(I), additional Kalvari-class submarines, indigenous AIP and submarine combat systems — reported by ANI
• Defence Research and Development Organisation (DRDO) — Indigenous Air Independent Propulsion (AIP) system and submarine technologies
• Naval Physical and Oceanographic Laboratory (NPOL), DRDO — Indigenous integrated submarine combat system development
• Mazagon Dock Shipbuilders Limited (MDL) — Kalvari-class submarine construction and naval shipbuilding programmes
• ThyssenKrupp Marine Systems (TKMS) — Partnership for advanced conventional submarine programme under Project-75(I)

---