The Submarine Gap — Why Project 75I Is the Navy's Most Urgent Programme

The Indian Navy's 30-year submarine plan, approved in 1999, called for 24 conventional submarines by 2030. The Navy has about 16, of which the six Scorpène-class (Kalvari) boats are modern; the remaining Sindhughosh (Kilo) and Shishumar (HDW Type 209) boats are 30 to 40 years old.

Project 75I

The plan for six air-independent propulsion (AIP) submarines under the Strategic Partnership model, worth roughly ₹70,000 crore, was approved in 2021. After a lengthy field evaluation, the pairing of Mazagon Dock with Germany's TKMS cleared the technical stage in 2025, with the Spanish Navantia–L&T bid the alternative. Commercial negotiations, contract, and the first boat are each multi-year milestones — first delivery is unlikely before the early 2030s.

The bridge options

1. Three additional Scorpènes at Mazagon Dock, with DRDO's indigenous AIP module, to keep the line running and add hulls by 2030.
2. Life extension of Kilo-class boats through Russian refits — expensive and diminishing returns.
3. Prioritising the nuclear-attack submarine (SSN) programme — two indigenous SSNs were cleared in October 2024, with Russian assistance discussed. SSNs give reach; AIP boats give numbers.

Why the gap matters

China's PLA Navy operates over 60 submarines and has sold eight Hangor-class boats to Pakistan, four of them built in Karachi, giving Pakistan a modern AIP fleet by the late 2020s. Submarines are the cheapest way to hold a carrier at risk — which is precisely India's carrier-centric fleet design's vulnerability.

The industrial angle

Submarine construction needs continuous work to retain the skilled workforce; Mazagon Dock's Scorpène line will go idle without follow-on orders. L&T's Hazira yard, which builds SSBN hull sections, is the second facility. Whichever path the Navy chooses, the shipyards need a decision by 2026 to avoid a lost decade of skills.

Specifications: Kalvari-class and INS Arihant.