MUMBAI: India’s Mazagon Dock Shipbuilders, in partnership with Germany’s ThyssenKrupp, has successfully cleared field trials for building six advanced conventional submarines for the Indian Navy, according to an exchange filing. The joint venture has emerged as the sole contender for the $5 billion project after its competitor, Spanish state-owned shipbuilder Navantia, partnered with L&T but failed to meet the navy’s technological requirements during trials conducted in 2024, as per sources, reported CNBC.
This project is a key component of India’s efforts to modernise its military and strengthen naval capabilities in response to China’s increasing presence in the Indian Ocean region. China’s increasing maritime activities in the region, including the deployment of advanced submarines, the construction of naval bases such as the one in Djibouti, and its Belt and Road Initiative projects at key ports like Gwadar in Pakistan and Hambantota in Sri Lanka, have heightened India’s security concerns. These developments enable China to project power in the Indian Ocean, challenging India’s historical dominance in these waters.
India’s conventional submarine fleet, many of which are ageing despite recent upgrades, currently put India in an undesirable and rather inadequate situation to counter this growing challenge. The addition of six state-of-the-art, air-independent propulsion (AIP) equipped submarines will significantly enhance the Navy’s ability to maintain an underwater advantage, deter adversarial actions, and ensure the safety of sea lanes of communication.
Also strengthening India’s naval power is not just about countering China; it is also about asserting India’s role as a net security provider in the Indian Ocean Region. This includes safeguarding smaller nations in the area, supporting friendly navies, and contributing to broader international efforts to ensure freedom of navigation. By modernising its submarine capabilities, India is not only addressing immediate security challenges but also positioning itself as a key maritime power in a rapidly evolving global order.
Mazagon Dock announced on Thursday (January 23) that its field trials met the necessary standards, prompting the Union defence ministry to invite the company for commercial negotiations next week.
A critical requirement for the new submarines under India’s $5 billion project is the integration of air-independent propulsion (AIP) technology, a game-changer in modern submarine warfare. This technology allows diesel-electric attack submarines to remain submerged for extended durations, exceeding two weeks, without the need to surface to recharge their batteries. This capability drastically enhances the stealth and operational efficiency of submarines, making them less vulnerable to detection by enemy forces.
Traditional diesel-electric submarines must surface every few days to intake oxygen for their engines, a process that exposes them to potential threats from adversaries’ anti-submarine warfare capabilities. In contrast, AIP-equipped submarines use alternative energy systems, such as fuel cells or closed-cycle engines, to generate power underwater, significantly reducing their detectability and increasing their combat readiness during prolonged missions.
Currently, none of the Indian Navy’s 17 operational conventional submarines are equipped with this technology, creating a critical capability gap when compared to neighbouring rivals, China and even Pakistan. Both countries have already incorporated AIP systems into their fleets, bolstering their naval strength. The People’s Liberation Army Navy (PLAN) operates the Yuan-class (Type 039A) diesel-electric submarines, which are the first Chinese submarines equipped with an indigenously developed air independent propulsion system.
While the Pakistan Navy has incorporated the technology into its fleet through the Agosta-90B submarines. Notably, the PNS Hamza, commissioned in 2008, was the first in South Asia to feature the French MESMA (Module d’Energie Sous-Marin Autonome) AIP system. Subsequently, Pakistan retrofitted its earlier Agosta-90B vessels with MESMA during overhauls. Pakistan is set to enhance its AIP capabilities with the induction of Chinese-built Hangor-class submarines, which are expected to join the fleet by the late 2020s and early 2030s.
The lack of AIP-equipped submarines puts India at a strategic disadvantage, particularly in contested waters like the Indian Ocean, where stealth and endurance are essential for surveillance, deterrence, and maintaining a tactical edge against adversaries. This project aims to bridge that gap by equipping the Indian Navy with advanced submarines capable of operating effectively in an increasingly complex maritime security environment.
In contrast, the Indian Navy’s current fleet of 17 conventional submarines lacks AIP technology, necessitating more frequent surfacing to recharge batteries, which can compromise stealth and operational effectiveness.
The project has faced delays of over a decade, with the first submarine now expected three to five years after a contract is finalised. Many of India’s conventional submarines are nearing the end of their operational lifespan, despite recent upgrades and retrofits.
Air-independent propulsion (AIP)
Air-Independent Propulsion (AIP) is an advanced technology used in non-nuclear submarines that allows them to operate underwater for extended periods without the need to surface for oxygen. This enhances the stealth, endurance, and operational capabilities of diesel-electric submarines, making them less vulnerable to detection.
Unlike conventional diesel-electric submarines that rely on surface oxygen for their engines, AIP systems generate power underwater through alternative methods, significantly enhancing a submarine’s stealth, endurance, and operational capabilities.
Several AIP technologies are employed globally. Fuel cells, such as Proton Exchange Membrane or Solid Oxide systems, combine hydrogen and oxygen to produce electricity quietly and efficiently, with water as the byproduct. These are commonly used in Germany’s Type 212/214 submarines. Stirling engines, found in Sweden’s Gotland-class submarines, use liquid oxygen and diesel fuel in a closed-cycle heat engine to generate power. The French-designed MESMA system, featured in Pakistan’s Agosta-90B submarines, utilises a steam turbine powered by ethanol and oxygen. Emerging technologies like lithium-ion batteries promise greater energy storage, enabling submarines to stay submerged for even longer durations.
AIP submarines offer several advantages. They can remain underwater for weeks compared to the few days possible for conventional submarines, significantly reducing the risk of detection. Their quieter operations make them ideal for covert missions, and they enhance energy efficiency, critical in stealthy underwater operations. However, AIP systems have limitations. They are most effective at low speeds, as high-speed manoeuvres still require conventional batteries or surfacing. Additionally, AIP systems are costly to install and maintain, and some, like fuel cell-based systems, face logistical challenges related to hydrogen storage.
AIP technology has been widely adopted by navies worldwide, including Germany, Sweden, China, and Pakistan. India plans to integrate AIP into its next-generation submarines, such as those under Project-75I, to enhance its naval capabilities. This makes AIP essential for modern naval warfare, providing a crucial edge in contested waters.
