India’s submarine modernisation program is facing critical delays that are undermining its underwater deterrent capabilities at a time when regional adversaries are significantly advancing their own submarine fleets. The eight-year delay in the indigenous Air Independent Propulsion (AIP) system has become emblematic of broader challenges plaguing India’s naval modernisation efforts, while Pakistan and China accelerate their underwater warfare capabilities in the strategically crucial Indian Ocean Region.
The AIP System Delay: A Critical Technological Gap
The Defence Research and Development Organisation’s (DRDO) fuel cell-based AIP system represents a crucial technology for extending submarine underwater endurance, yet it remains operationally unavailable eight years after its initial 2017 deadline.
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Originally sanctioned in 2014 with a budget of ₹270 crore, the system was expected to transform India’s Scorpene-class submarines by enabling them to remain submerged for up to two weeks instead of the current few days.
The first Scorpene submarine, INS Kalvari, has completed its maintenance refit without receiving the AIP upgrade that was originally planned. Naval sources now hope the system will be ready for INS Khanderi’s scheduled refit in mid-2026. This delay is particularly concerning as it leaves India’s entire conventional submarine fleet without AIP capability, while regional competitors have already fielded such technology.
The integration process, known as “Jumboisation,” involves the complex procedure of cutting open submarine hulls, inserting the AIP module, and welding the structure back together. On July 23, 2024, Mazagon Dock Shipbuilders Limited (MDL) and Naval Group finally signed an agreement for AIP integration on the Scorpene submarines, marking progress after years of delays.
Pakistan’s Strategic Submarine Advantage
Pakistan has gained a significant underwater warfare advantage through its strategic partnership with China and earlier French technology acquisitions. The Pakistan Navy currently operates three Agosta-90B submarines equipped with the French MESMA (Module d’Energie Sous-Marin Autonome) AIP system, making it the first South Asian nation to field AIP-equipped submarines since 2008.
More significantly, Pakistan is on track to receive eight Yuan-class (Hangor-class) submarines from China, all equipped with advanced AIP systems. These submarines utilise a Stirling cycle AIP system that provides underwater endurance of up to 18 days. The acquisition agreement, worth $5 billion, was signed in 2015, with four submarines being built in China and four at Karachi Shipyard & Engineering Works under technology transfer arrangements.
By 2030, Pakistan will operate eleven AIP-equipped submarines, representing a dramatic capability enhancement that alters the underwater balance in South Asian waters. The Hangor-class submarines feature improved stealth, maneuverability, and firepower, potentially carrying nuclear-capable Babur-3 cruise missiles.
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India’s Ageing Conventional Submarine Fleet
India’s conventional submarine force faces significant challenges from ageing platforms and delayed modernisation programs. The Indian Navy currently operates 16 conventional submarines: six modern Scorpene-class vessels, seven Russian Kilo-class submarines, and four German HDW submarines. Most of the Russian and German submarines are over three decades old, presenting increasing maintenance challenges and reduced operational capabilities.
The Kilo-class fleet has been particularly affected by ageing, with the strength reduced from ten to seven submarines following decommissioning and accidents. The tragic loss of INS Sindhurakshak in 2013, which killed 18 sailors in an onboard explosion, highlighted safety concerns with ageing platforms. The Indian Navy has been conducting Medium Refit with Life Certification (MRLC) programs to extend submarine service lives, but these measures provide only temporary solutions.
The six Scorpene-class submarines under Project-75, built by MDL in partnership with France’s Naval Group at a cost of over ₹23,000 crore, represent India’s most modern conventional submarines. INS Vagsheer, the sixth and final submarine, was commissioned in January 2025. However, these submarines currently lack AIP capability, limiting their underwater endurance compared to Pakistan’s fleet.
Nuclear Submarine Program: India’s Strategic Asset
India’s nuclear submarine program represents a significant strategic achievement, providing the sea-based component of its nuclear triad. The country currently operates two nuclear-powered ballistic missile submarines (SSBNs): INS Arihant, commissioned in 2016, and INS Arighaat, commissioned in August 2024.
INS Arighaat, significantly more advanced than its predecessor with 70% indigenous content, can carry up to twelve K-15 Sagarika missiles (750 km range) or four K-4 missiles (3,500 km range). A third SSBN, INS Aridhaman, is expected to be commissioned in 2025, with a fourth submarine (codenamed S4*) launched in 2024.
The nuclear submarine program demonstrates India’s technological capabilities and strategic commitment to maintaining a credible second-strike capability. However, the country still lacks nuclear-powered attack submarines (SSNs), with plans for indigenous SSN construction targeting delivery by 2036-2037.
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Project 75I: The Future of Indian Submarine Warfare
Project 75I represents India’s most ambitious submarine acquisition program, aiming to procure six advanced diesel-electric submarines equipped with AIP systems for approximately ₹70,000 crore. After extensive delays and evaluations, MDL partnered with Germany’s ThyssenKrupp Marine Systems (TKMS) emerged as the preferred bidder in 2025.
The submarines, based on the HDW Class 214 design, will feature proven fuel-cell AIP systems enabling two-week underwater endurance, advanced sensors, and modern weaponry including potential BrahMos missile integration. The program mandates progressive indigenisation, starting at 45% for the first submarine and reaching 60% by the sixth.
However, Project 75I has faced multiple delays, with the first submarine now expected by 2032 if contracts are finalised in 2025. The program’s complexity, involving technology transfer requirements and strategic partnership models, has contributed to prolonged procurement timelines.
China’s Growing Naval Dominance
China’s naval expansion presents the most significant challenge to Indian Ocean security, with the People’s Liberation Army Navy now operating the world’s largest submarine fleet. China’s submarine force includes approximately 60 vessels: six Jin-class SSBNs, six Shang-class SSNs, and 48 diesel-electric submarines, many enhanced with AIP technology.
The Yuan-class (Type-039A) submarines, which form the basis for Pakistan’s Hangor-class vessels, represent China’s first indigenous AIP-powered submarines. China has also made significant advances in underwater detection technology, developing AI-driven torpedo systems with 92.2% success rates in distinguishing submarines from decoys.
China’s “String of Pearls” strategy, involving strategic port developments from Gwadar in Pakistan to Hambantota in Sri Lanka, provides potential naval access points throughout the Indian Ocean. This strategic positioning, combined with expanding submarine capabilities, challenges India’s traditional maritime dominance in the region.
Modernisation Challenges And Future Prospects
India’s submarine modernisation faces multiple structural challenges including bureaucratic delays, cost escalations, and technology integration complexities. The Project-75 experience, where costs increased from ₹18,706 crore to ₹23,562 crore with five-year delivery delays, illustrates persistent procurement issues.
Despite these challenges, India maintains several advantages including indigenous nuclear submarine capabilities, advanced missile technology, and established shipbuilding infrastructure. The commissioning of INS Arighaat and planned INS Aridhaman demonstrate continued progress in strategic submarine capabilities.
The activation of underwater surveillance partnerships, such as the recent India-Australia collaboration for maritime domain awareness, indicates growing international cooperation to counter regional challenges. These partnerships provide technological and intelligence-sharing opportunities that could enhance India’s underwater warfare capabilities.
IDN (With Agency Inputs)
Agency
