India Accelerates Undersea Power: Progress and Projections in P75I, P75(AS), P76 & P77 Submarine Programmes
India’s submarine modernisation drive is entering a new phase of momentum, with multiple indigenous programmes — including Project 75(I), Project 75(AS), Project 76, and Project 77 — showing fresh developments even as delays and technical challenges persist. Key private and public shipyards, government R&D bodies, and foreign partners are all in play, overlapping timelines and design stages.
Key Programmes: Status & Players
| Programme | Type / Role | Major Entities Involved | Current Stage / Updates | Timelines & Indigenous Content |
|---|---|---|---|---|
| Project 75 (Scorpene or “P75”) | Diesel-electric attack submarines (SSKs) | State-owned Mazagon Docks Ltd (MDL) & Naval Group (France) | Six Kalvari-class submarines inducted. Efforts to integrate domestic AIP (air-independent propulsion) modules delayed. First AIP plug likely in INS Khanderi by 2026-27. Energy module expected to be ready by December 2025. | Base platform mostly foreign-designed; domestic integration increasing. |
| Project 75 India (P75I) | Next-gen attack submarines with AIP | MDL + TKMS (Germany). L&T + Navantia competed earlier. | MDL and TKMS have begun official contract negotiations. TKMS signed MoUs with Indian firms for heavyweight torpedoes and subsystems. TKMS AIP will be key to programme. | First submarine ~7 years after contract. Indigenous content 45% initially, rising to 60% by sixth submarine. |
| Project 75(AS) | Modified Kalvari class (stopgap SSKs) | MDL & Indian Navy | Aimed to add three more Kalvari-class boats to maintain fleet numbers. Contract was expected by March 2025 but remains unsigned; project in limbo. | Three boats planned. Provides breathing space until P75I. |
| Project 76 (P76) | Indigenous conventional submarines (SSKs) | L&T, MDL, DRDO, Submarine Design Group (Navy) | Preliminary design underway. Six submarines planned. Full design expected by 2026-27, production in 6–7 years. | Displacement ~3,000 tons. Armed with indigenous torpedo-tube-launched cruise missiles. High indigenous content (~95%). |
| Project 77 (P77) | Nuclear-powered attack submarines (SSNs) | DRDO, L&T, BARC, Navy Design Bureau | CCS approved programme in late 2024. First of six SSNs projected by 2036-37. Work underway on new reactor design (CLWR-B2) and quiet propulsion systems. | Displacement larger than Arihant SSBNs (5,000–7,000 ton class expected). Indigenous content projected at ~95%. |
Additional Details & Technical Insights
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Reactor & Propulsion (P77): India is developing a more powerful compact light-water reactor (CLWR-B2) with an output of around 190 MWt. Nuclear-electric propulsion is under study to reduce acoustic signatures.
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Sensors & Weapons: Development underway for conformal bow arrays, flank and towed sonars, non-penetrating optronic masts, indigenous heavyweight torpedoes, and weapon-control systems.
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Displacement: P76 submarines are expected to displace ~3,000 tons, significantly larger than the Kalvari class. The P77 SSNs could reach 7,000 tons submerged.
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Infrastructure: The Ship Building Centre (SBC) in Visakhapatnam will lead SSN assembly. L&T’s Hazira facility will handle major hull sections. BARC is working on nuclear reactor modules.
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AIP Integration: The domestic AIP module being developed by DRDO and L&T is facing schedule slippages. The first live plug is expected to be fitted into INS Khanderi during its refit in 2026-27.
Strategic Implications
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Fleet Strength: With ageing Kilo and HDW submarines nearing retirement, the Indian Navy faces capability gaps. The combined set of P75I, P75(AS), and P76 programmes aims to stabilise fleet numbers.
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Indigenisation: All new projects focus heavily on indigenous content, with P76 and P77 targeting 90–95% local systems and technology.
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Deterrence & Reach: Nuclear-powered SSNs from P77 will provide blue-water endurance and power projection, while advanced AIP-equipped SSKs will strengthen coastal and regional defence.
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Timelines: While ambitious, overlapping programmes risk delays if budgetary approvals, R&D milestones, or industrial capacities slip.
Outlook
India’s undersea warfare roadmap is now more comprehensive than ever:
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P75(AS) to plug immediate gaps.
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P75I to bring new-generation AIP submarines.
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P76 to establish an indigenous conventional design line.
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P77 to finally give the Navy a fleet of nuclear-powered attack submarines.
The coming decade will be decisive: the success of AIP integration, finalisation of P75I contracts, and timely execution of P76/P77 will determine how effectively India transforms its submarine arm into a balanced, modern, and largely indigenous force.
