India's undersea dominance: project 75-i, aip tech, and the next-gen nuclear fleet

India’s maritime strategy is undergoing a profound transformation, shifting from a defensive posture to one of assertive sea control, particularly in the Indian Ocean Region (IOR). Central to this evolution is the modernization and expansion of its submarine fleet, a critical asset for both conventional warfare and strategic deterrence. Recent developments, including progress on Project 75-I and the landmark approval for a new class of nuclear attack submarines, signal a clear intent to build a formidable underwater force.

The Conventional Edge: Scorpene-Class and AIP Revolution

India’s conventional submarine power is spearheaded by the Kalvari-class submarines, based on the French Scorpene design. These diesel-electric attack submarines (SSKs) are crucial for littoral warfare, intelligence gathering, and anti-submarine operations.

Project 75, a collaboration with France’s Naval Group, has been instrumental in this effort, leading to the construction of six Kalvari-class submarines at Mazagon Dock Shipbuilders Limited (MDL).

Mnemonic for Scorpene-Class Submarines: To remember the six submarines, use the phrase: “Keep Kalm, Keep Vigilant, Very Vigilant” (for Kalvari, Khanderi, Karanj, Vela, Vagir, Vagsheer).

Fun Fact: The Kalvari-class is named after the Indian Navy’s first-ever submarine, the INS Kalvari (S23), a Soviet Foxtrot-class vessel inducted in 1967. The name itself is derived from the Malayalam word for tiger shark, a deep-sea predator.

A significant leap for the conventional fleet is the development of Air Independent Propulsion (AIP) technology. An AIP system allows a non-nuclear submarine to operate without needing to surface to recharge its batteries, drastically increasing its underwater endurance from days to weeks and enhancing its stealth.

The DRDO has successfully developed an indigenous fuel-cell-based AIP system. Following successful land-based tests, this system is scheduled to be retrofitted onto the Scorpene fleet, starting with INS Khanderi during its refit cycle beginning in mid-2026.

The Next Wave: Project 75-India (P75-I)

Building on this foundation, Project 75-India (P75-I) is the ambitious successor program to acquire six next-generation conventional submarines. These vessels will be larger, more advanced, and equipped with AIP and land-attack cruise missiles from the outset. After years of deliberation, the project is gaining momentum, with MDL, in partnership with Germany’s ThyssenKrupp Marine Systems (TKMS), emerging as a frontrunner. The final contract is anticipated to be signed by early 2026, marking a major step under the ‘Make in India’ initiative.

The Nuclear Guardian: SSNs and SSBNs

Nuclear-powered submarines provide unparalleled strategic capability due to their virtually unlimited range and endurance. They are broadly classified into two types:

Fun Fact: A nuclear submarine like the INS Arihant can stay submerged for several months, limited only by the amount of food and supplies it can carry for the crew. Its reactor can theoretically operate for years without refueling.

India’s SSN fleet has historically relied on leased submarines from Russia, known as the ‘Chakra’ series. However, a major strategic shift occurred in October 2024, when the Cabinet Committee on Security (CCS) approved a high-priority plan to design and build six indigenous SSNs. This project, often referred to as Project 75 Alpha, is vital for protecting India’s sea lanes and carrier battle groups, and for countering the growing naval presence of adversaries in the IOR.

The cornerstone of India’s strategic deterrence is its SSBN fleet, which guarantees a credible second-strike capability and completes the nuclear triad. The indigenous Arihant-class submarines are the heart of this capability.

• INS Arihant: The first indigenous SSBN, commissioned in 2016.
• INS Arighat: The second SSBN, an improved version of the Arihant, was formally commissioned in August 2024, significantly bolstering India’s deterrent posture.

These submarines are capable of launching the K-family of Submarine Launched Ballistic Missiles (SLBMs).

Fun Fact: The term “nuclear triad” refers to a country’s ability to deliver a nuclear strike from land-based missiles, strategic bombers in the air, and submarines in the sea. It is considered the most robust and survivable form of nuclear deterrence.

Critical Policy Appraisal

Analytical Lens: UPSC Focus (Mains & Prelims)

Conceptual Basis: The legal and strategic foundation for India’s submarine program is rooted in its Maritime Security Strategy and its Nuclear Doctrine, which codifies the policy of Credible Minimum Deterrence and a “No First Use” posture, making a survivable second-strike capability (assured by SSBNs) paramount.

UPSC Integration: Connecting the Dots

• Polity & Governance: The submarine acquisition process is a key case study in defence procurement policy, the role of the Cabinet Committee on Security (CCS), and the implementation of the ‘Make in India’ initiative in the strategic sector.
• International Relations: The submarine fleet is a primary instrument of India’s SAGAR (Security and Growth for All in the Region) policy and its ‘Act East’ policy. It is also central to the strategic competition with China in the Indo-Pacific and India’s role within alliances like the Quad.
• Science & Technology: The program involves cutting-edge technologies like nuclear propulsion (pressurized water reactors), Air Independent Propulsion (AIP) systems, and advanced missile technology (SLBMs), which are crucial topics.

Expert Analysis & Future Impact: The recent approvals and inductions represent a pivotal moment. India is accelerating its transition from a ‘buyer’s navy’ to a ‘builder’s navy’. The long-term impact will be a significant enhancement of India’s strategic autonomy and power projection capabilities. A robust, three-dimensional submarine fleet (SSK, SSN, and SSBN) will not only secure India’s maritime interests but also position it as a key stabilizer in the increasingly contested Indo-Pacific, capable of shaping regional security dynamics for decades to come.

Prelims Practice Question (MCQ):

Which of the following is the primary advantage of an Air Independent Propulsion (AIP) system in a conventional submarine? a) It allows the submarine to launch ballistic missiles. b) It provides the power for the submarine to travel at exceptionally high speeds. c) It significantly increases the submerged endurance of the submarine without needing to surface. d) It enables the submarine to dive to greater depths than a nuclear submarine.

Answer & Explanation: (c). The main purpose of an AIP system is to allow the submarine’s batteries to be recharged while it remains fully submerged, eliminating the need to surface or snorkel. This dramatically increases its underwater endurance and stealth, as surfacing is the most vulnerable phase for a conventional submarine.

Mains Sample Question (15 Marks):

Project 75-I is critical for modernizing India’s conventional submarine fleet but has faced significant delays. Critically analyze the strategic imperatives for the project, the challenges in its execution, and the measures required to strengthen indigenous submarine construction under the ‘Atmanirbhar Bharat’ framework.

Mind Map Outline (Revision Structure)

• India’s Submarine Fleet & Doctrine
  • Strategic Context
    • Maritime Security Strategy
    • Credible Minimum Deterrence (Nuclear Doctrine)
    • Role in the Indian Ocean Region (SAGAR Policy)
  • Conventional Submarines (SSK)
    • Project 75 (Scorpene-Class)
      • INS Kalvari
      • INS Khanderi
      • INS Karanj
      • INS Vela
      • INS Vagir
      • INS Vagsheer
    • Key Technology: Air Independent Propulsion (AIP)
      • Purpose: Enhanced underwater endurance
      • DRDO’s Indigenous Fuel-Cell System
      • Integration Plan (starting with INS Khanderi in 2026)
    • Project 75-India (P75-I)
      • Goal: 6 advanced submarines
      • Features: AIP, Land-Attack Missiles
      • Current Status: Partnership with Germany’s TKMS, contract expected by 2026
  • Nuclear-Powered Submarines
    • Classification
      • SSN (Attack Submarines)
      • SSBN (Ballistic Missile Submarines)
    • SSN Fleet (Hunter-Killers)
      • Legacy: Chakra-class (leased)
      • New Development (Oct 2024): Approval for 6 indigenous SSNs (Project 75 Alpha)
      • Strategic Role: Sea-lane protection, Carrier Battle Group support
    • SSBN Fleet (Strategic Deterrence)
      • Purpose: Second-strike capability (Nuclear Triad)
      • Arihant-Class
        • INS Arihant (S2)
        • INS Arighat (S3) - Commissioned August 2024
        • INS Aridhaman (S4) & S4* - Under development/trials
      • Weaponry: K-series Submarine Launched Ballistic Missiles (SLBMs)
  • Policy & Challenges
    • Critical Appraisal
      • Challenges: Procurement delays, foreign dependency, aging fleet
      • Opportunities: ‘Make in India’, strategic autonomy, private sector growth