India’s Ministry of Defence has advanced the ₹70,000-crore Project-75(I) submarine program to the Cabinet Committee on Security for final approval.

This initiative involves building six 3,000-tonne diesel-electric attack submarines at Mazagon Dock Shipbuilders Limited in Mumbai in partnership with Germany’s ThyssenKrupp Marine Systems.

The project is intended to replace the aging Sindhughosh and Shishumar-class submarines, many of which are already over 30 to 40 years old, and will integrate advanced fuel-cell Air-Independent Propulsion technology for extended submerged endurance.

The program specifies submarines capable of remaining submerged for 21 days continuously using German polymer-electrolyte-membrane hydrogen fuel cells. The first vessel is contractually required within seven years of signing, with indigenous content rising from 45% on the lead boat to 60% by the final delivery.

The Finance Ministry cleared the acquisition in May 2026, leaving CCS authorization as the last major step, with contract conclusion targeted by September 2026.

Project-75(I) stems from India’s 30-year submarine construction plan approved in 1999, which envisaged 24 conventional submarines. However, only six Kalvari-class boats have been delivered so far.

The procurement process for P-75(I) has stretched across more than 25 years, with approvals in 2010, 2014, and 2019. Even if signed in 2026, the first submarine will not be inducted until 2034–35, by which time most of the Navy’s current fleet will be over 40 years old.

The competition was narrowed from seven foreign designs to a single compliant MDL-TKMS team because India required an AIP system already proven at sea. Designs from France, Russia, Sweden, Japan, Spain, and South Korea were eliminated over time.

By 2025, only MDL-TKMS remained, and cost negotiations concluded in January 2026. The Indian submarine will differ significantly from the standard Type 214, being larger at 3,000 tonnes and adapted for Indian endurance, weapons, and sensor requirements.

The Indian configuration will retain 533 mm torpedo tubes but carry heavier armament, including 18 heavyweight torpedoes and at least 12 cruise missiles.

Compared with the Kalvari-class, which displaces 1,775 tons submerged, the P-75(I) will be substantially larger and capable of longer patrols in the Indian Ocean. The German AIP system allows 21 days of submerged endurance, reducing exposure compared to conventional diesel-electric submarines that must snorkel every 48–72 hours.

India’s current fleet consists of six modern Kalvari-class submarines and ten older boats from the Sindhughosh and Shishumar classes. Eight of these older submarines are already over 32 years old, with some reaching 40 years of service.

Maintaining them has required repeated modernization programs worth thousands of crores. The cost of P-75(I) is nearly three times that of the Kalvari program, reflecting its larger size, advanced technology, and extensive technology-transfer package.

The procurement schedule requires one submarine annually after the first delivery, with indigenous content rising toward 60%. If induction begins in 2034–35, the six submarines will arrive as the older fleet retires, leaving a potential gap in numbers.

The Navy has considered an option for three additional submarines to reduce this deficit. Project 76, cleared in 2024, aims to produce an indigenous 3,000-tonne submarine, absorbing lessons from both Project-75 and P-75(I). However, timelines remain tight, as Project 76 must overlap with P-75(I) to avoid further delays in fleet renewal.

The enlarged TKMS design is therefore crucial not only for immediate fleet replacement but also for India’s long-term submarine-building capability. It provides experience in AIP integration, larger hull architecture, and advanced engineering methods, all of which will be vital for Project-76.

The challenge remains to ensure timely induction, as delays could leave India with a reduced submarine force during a critical period of regional maritime competition.

Agencies