Project-76 is an ambitious Indian Navy program to build 12 advanced conventional submarines, with the first prototype expected around 2030. These are indigenous diesel-electric submarines equipped with Air-Independent Propulsion (AIP) and estimated to have a submerged displacement around 3,000 to 4,000 tonnes, marking a significant leap in size and endurance from previous classes.

Project-76 subs will feature key technologies such as pump-jet propulsion for enhanced stealth and efficiency, lithium-ion batteries, and a fully indigenous weapon control system. The design also draws on experience and technology from India’s upcoming nuclear attack submarines under Project-77, aiming for a high share (up to 80%) of indigenous components.

This project is focused on reducing dependency on foreign designs while enhancing underwater endurance and operational versatility in contested environments.

Project-75, also called the Kalvari-class, involved the construction of six Scorpene-class diesel-electric attack submarines in collaboration with the French Naval Group and Indian shipyards. These subs displace about 1,700 tons submerged, are equipped with conventional diesel-electric propulsion with some integration of AIP technology, and feature wire-guided torpedoes and tube-launched anti-ship missiles.

Project-75 marks India’s first major indigenous submarine production effort with technology transfer, aimed at modernizing the underwater fleet with stealth and advanced sensors, but with a smaller size and less underwater endurance compared to later projects.

Project-75I (India) is a follow-up to Project-75, aiming to build six advanced conventional submarines with foreign design collaboration but greater indigenous construction. These subs will be larger than the Project-75 boats, with an expected displacement of about 3,000 tonnes, and equipped with Air-Independent Propulsion systems for substantially enhanced underwater endurance.

P-75I integrates newer generation sensors, ISR (Intelligence, Surveillance, Reconnaissance) capabilities, and advanced weapons suites including land-attack cruise missiles, anti-ship missiles, and heavyweight torpedoes. It fills the capability gap between the smaller Project-75 and the much larger nuclear attack submarines under Project-77. Its design also emphasizes stealth and operational flexibility in diverse maritime roles.

The primary distinctions lie in displacement, propulsion, stealth, and indigenous content: Project-75 set the foundation with smaller Scorpene-class diesel-electric subs; Project-75I scales up with more advanced AIP-enabled diesel-electric subs of about 3,000 tons, stronger indigenous content, and enhanced combat systems; Project-76 further leaps ahead with larger (3,000–4,000 tons) submarines featuring pump-jet propulsion, lithium-ion batteries, full indigenous design, and technologies derived from nuclear submarine programs, aiming for superior underwater endurance, stealth, and multirole operational capabilities.

These programs represent a continuum toward greater self-reliance and enhanced submarine warfare capabilities for the Indian Navy in the coming decades.

This layered approach strategically balances immediate fleet modernization (P-75), mid-term advanced capability upgrade (P-75I), and long-term high-end indigenous technology-driven capability (P-76) for comprehensive maritime dominance. Each project progressively incorporates newer technologies, greater indigenous manufacturing, and larger platform sizes to meet evolving maritime security challenges.

Detailed comparison of Project-76 with Project-75I and Project-75 submarines:

AspectProject-75Project-75IProject-76
PurposeBuild six Scorpene-class conventional diesel-electric submarines with technology transfer from France (Naval Group).Build six advanced conventional submarines with Air Independent Propulsion (AIP) and foreign design support under the Strategic Partnership model.Build 12 fully indigenous diesel-electric submarines with AIP, advanced stealth, and weapon systems developed domestically.
Indigenous ContentModerate (~40-50%) via technology transfer for construction in India.Higher indigenous content (45%-60%) focusing on newer tech and local manufacturing.Very high indigenous content (~90-95%) with domestic design, weapon control, and lithium-ion battery integration.
Air Independent Propulsion (AIP)Not equipped (traditional diesel-electric).Equipped with AIP fuel-cell systems that enable about two weeks submerged endurance.Equipped with indigenous AIP system from DRDO for enhanced endurance and stealth.
DisplacementApprox. 1,500-1,700 tons (Scorpene-class).Larger than Project-75 subs, ~3,000 tons.Approximately 3,000 tons submerged displacement, next-gen capabilities.
ManufacturingMazagon Dock Shipbuilders (MDL) with French collaboration.Indian shipyards with foreign OEM design support (Germany's ThyssenKrupp or Spain’s Navantia).Larsen & Toubro (L&T) leading indigenous design and build with DRDO collaboration.
Operational TimelineFirst delivery by mid-2020s, operational by late 2020s to mid-2030s.Expected delivery between late 2020s and mid-2030s (delayed).Design completion by 2027, construction start ~2030, commissioning by 2037.
Key FeaturesStealth technologies and modern torpedoes/missiles but no AIP.Advanced sensors, stealth, cruise missile capability, AIP, and ISR systems.Indigenous weapon control system, lithium-ion batteries, cruise missile strike capability, and strong stealth.
Strategic SignificanceFoundation of modern Indian conventional submarine force.Next stage in capability with modern tech and higher self-reliance.
Leap towards full indigenous underwater naval capability with emphasis on strategic autonomy and export potential.

Project-75 introduced Scorpene submarines with moderate indigenous content and no AIP. Project-75I improves on Project-75 by adding AIP and modern combat systems with foreign design support but higher indigenous manufacture.

Project-76 is the most ambitious, aiming for near-complete indigenous design and build with the latest technologies and advanced weapon systems, representing a major step toward India’s strategic and industrial self-reliance in submarine capabilities

IDN (With Agency Inputs)