The Indian Navy is gearing up to acquire six advanced submarines under Project-75I. This project, with its focus on stealth and endurance, aims to integrate Fuel Cell Air-Independent Propulsion (AIP) technology with cutting-edge Lithium-ion batteries, positioning the Indian Navy at the forefront of modern naval warfare.

The Indian Navy’s pursuit under Project-75I is not just about expanding its fleet but ensuring it remains ahead in terms of stealth and lethality. In the contemporary maritime environment, where the element of surprise can decisively tilt the balance, the capability to remain undetected while operating in enemy waters is invaluable. This is where the integration of AIP technology and Lithium-ion batteries becomes a game-changer.

ThyssenKrupp: The Frontrunner

Among the international competitors vying for this prestigious contract, the German shipbuilder ThyssenKrupp (tkMS) has emerged as a leading contender. TkMS has proposed its 214-class submarines, which incorporate the advanced technologies seen in the 212 CD class submarines, known for their deployment by the Norwegian Navy. The 214-class submarines for India will be tailored specifically to meet the Indian Navy’s operational requirements.

“In this, our big advantage is our unique AIP solution. The submarine design is a derivative of the well-established HDW Class 214 submarine, which is currently in service with several navies worldwide. It will be tailored to the Indian Navy’s requirements and incorporate technological advancements. To summarise our Project-75I design: it is proven, it is advanced, and it is for India,” said Dr. Christian Frühling, the tkMS Program Head for Project-75I.

Game-Changing Technology

The combination of fuel-cell-based AIP systems with Lithium-Ion batteries offers substantial operational advantages. The fuel-cell AIP provides extended endurance at low speeds, while the Lithium-ion batteries allow for high-speed maneuvers without compromising stealth. This dual capability is crucial for the Indian Navy, given its expansive area of responsibility, which extends from the Gulf of Aden to the Strait of Malacca.

“The submarines can remain submerged longer and can also have high-speed performance. The combination makes sense,” Frühling added. This means that the submarines could cover the entire Bay of Bengal while remaining submerged, significantly reducing the risk of detection.

AIP technology allows submarines to remain submerged for extended periods, up to three weeks, without needing to surface. This is particularly vital as a submarine is most vulnerable when it surfaces to periscope depth to recharge its batteries. The integration of hydrogen-powered fuel cells, which operate silently and without emitting exhaust heat, further enhances the submarine’s stealth capabilities.

Stealth and Countermeasures

Stealth is a critical component of modern submarines, and the 214-class excels in this domain. The use of fuel cells ensures the lowest possible noise levels, as the electro-chemical reaction in the fuel cells produces almost no sound. The submarines can launch torpedoes stealthily using a water ram expulsion system, and are equipped with countermeasures against enemy torpedoes, including underwater effector jammers. The minimized acoustic, thermal, and magnetic signatures make these submarines virtually undetectable.

Operational Flexibility

AIP-enabled submarines offer increased operational flexibility. They can “bottom” or sit on the ocean floor with only critical systems running to conserve energy, extending their mission duration while using passive sonar to detect targets. Since fuel cells are more efficient at lower loads, bottoming can significantly extend the endurance of a mission.

Efficient energy systems are a key requirement for the Indian Navy, and the customization of propellers to meet specific operational needs ensures unique signatures for each submarine, enhancing their stealth.

Non-Nuclear AIP-Enabled Submarines: A Cost-Effective Solution

Compared to nuclear-powered submarines, AIP-based non-nuclear submarines are more cost-effective, both in terms of acquisition and maintenance. Fuel cell systems are modular, allowing for quick and easy replacement, and these submarines typically have smaller crews of 25-35 people.

The Indian submarine fleet currently includes 16 submarines, far short of the required 24. Most of these submarines are over 30 years old and nearing decommissioning. The urgency for Project-75I cannot be overstated, especially with the growing Chinese naval presence in the Indian Ocean Region.

German Government’s Support

Initially hesitant when the tender was floated three years ago, the German government has now fully endorsed the project. In March 2024, the German Navy provided a submarine for the Indian Navy to evaluate in the field. An Indian Navy team participated in a day-long diving trial in a 212-class German submarine to assess the AIP technology firsthand.

TkMS stands confident in its technology, being the only company with sea-proven fuel-cell-based AIP systems. The 214-class submarines are currently operated by Greece, Portugal, Turkey, and South Korea, showcasing their global acceptance and reliability.

Transfer of Technology and Local Manufacturing

A critical aspect of Project-75I is the transfer of technology and local manufacturing. TkMS has a long-standing partnership with Mazagon Dockyard Limited (MDL) in India, dating back to the 1980s. Together, they have built and maintained the Indian Navy’s 209-class submarines.

For Project-75I, the submarines will be built in India from the first vessel onwards. TkMS will supply the design and critical elements, while MDL will be the prime contractor. This collaboration ensures that India gains the technological expertise and autonomy in submarine manufacturing.

“We have already begun the design work on the project in conjunction with MDL,” Frühling informed. The first submarine is expected to be ready approximately seven years from the contract date, with subsequent submarines delivered annually.

The Competitive Landscape

Spain’s Navantia is the other contender in the fray for Project-75I. However, Navantia’s AIP technology, the BEST (Bio-Ethanol Stealth Technology) system, is not yet operational. While factory acceptance tests for the S-80 submarines were conducted in 2023, the technology remains unproven in the field. This could give tkMS an edge, as the Indian Navy may prefer proven and reliable technology.

Strategic Implications

The strategic importance of Project-75I cannot be overstated. As China’s naval capabilities continue to expand, including quieter and stealthier submarines, it is imperative for India to strengthen its underwater fleet. Enhanced stealth and endurance capabilities will provide the Indian Navy with a critical edge in the Indian Ocean Region.

Project-75I represents a significant leap forward for the Indian Navy, combining advanced AIP technology with Lithium-ion batteries to create a fleet of submarines that are stealthy, lethal, and capable of extended operations. With ThyssenKrupp’s proven technology and the support of the German government, the Indian Navy is poised to enhance its underwater capabilities significantly. This project not only promises to bolster India’s maritime security but also marks a milestone in the Indo-German defense collaboration.