On Monday, the Ministry of Defence (MoD) signed two major deals worth Rs 2,867 crore to enhance the submarine capabilities of the Indian Navy. The deals are focused on the integration of sophisticated Air Independent Propulsion (AIP) technology and Electronic Heavyweight Torpedo (EHWT) systems into Indian submarines. According to an official MoD release, the contracts were signed in New Delhi with Defence Secretary Rajesh Kumar Singh in attendance.
One of the significant agreements signed with Mazagon Dock Shipbuilders Limited (MDL) at Mumbai is valued at Rs 1,990 crore. This contract is for the building of AIP plug-in for Defence Research and Development Organization’s (DRDO) AIP system to be incorporated into Indian submarines. DRDO’s indigenously developed AIP technology will immensely enhance the underwater endurance of conventional submarines that align with India’s Aatmanirbhar Bharat initiative. In addition, the project will create nearly 300,000 man-days of employment.
AIP-powered conventional submarines can remain underwater for up to two weeks. This is quite an improvement over older diesel-electric submarines, which normally stay underwater for just 48 hours. Long endurance in operation means less exposure to detection when a submarine has to surface to recharge its batteries.
With AIP technology, submarines can operate more quietly, thus making them very difficult to track by hostile forces. This is an important leap forward for Indian naval capabilities and enhances India’s defense preparedness.
Submarines under Project-75 are going to integrate AIP technology, a great step forward in the capabilities of these Kalvari-class submarines. AIP is an underwater propulsion system that significantly extends the endurance of conventional submarines, allowing them to remain underwater for a long period without surfacing to charge their batteries. It would give the Indian Navy an edge in underwater operations.
The steel-cutting ceremony of the AIP system, designed by the DRDO, was held on 28 December 2023 at the Larsen & Toubro (L&T) Hazira facility.
This marks the culmination of an agreement inked in June 2023 between the DRDO and L&T for two AIP System Modules for Kalvari-class submarines of the Indian Navy. These are essentially the core modules for a fuel cell-based AIP system, developed by NMRL of DRDO as an indigenous system and partnered with L&T for primary industry support. This decade-old relationship has been an integral part of the development of AIP technology.
The cutting-of-steel ceremony is another step in the broader mission of integrating AIP capabilities into India’s submarine arm. In July 2024, Kamat inaugurated an AIP Integration and Testing facility at the AM Naik Heavy Engineering Complex. The system is expected to go through a grueling testing procedure and be ready for induction by the end of 2025.
Subsequently, it will be integrated with the INS Kalvari, the first of the six Scorpene-class submarines being built under Project-75 at Mazagaon Dockyard Limited (MDL). The Kalvari will be the test bed for the indigenously developed AIP technology in its first major refit scheduled for September 2025.
Integrating AIP into an operational submarine is not a straightforward process. The process entails cutting the submarine into two halves, following which the AIP system will be installed, which will elongate and increase its weight. The intricate task of overseeing the installation and testing will probably be handled by the Naval Group, the French company that designed the Scorpene class.
These changes will be further tested as they are deployed to the rest of the Scorpene-class submarines. However, though this change reduces the operational readiness of the Navy during the refit, the introduction of the AIP technology has marked a giant leap in enhancing submarine capabilities for India.
Why the Indigenous AIP System Is a Game-Changer
AIP is of great significance for the traditional diesel-electric submarines, SSK, as it positions them between nuclear-powered submarines and old diesel-electric models strategically. A traditional SSK with AIP can spend 10 to 14 days submerged in water without surfacing to breathe through snorkeling, a practice that is often used by submarines to charge their batteries and leaves the submarine exposed to detection.
The fuel-cell-based AIP, in the case of India’s Kalvari-class submarines, is special because it has the ability to produce its own hydrogen onboard, eliminating the need to store hydrogen onboard.
The fuel-cell-based AIP also adds maneuverability. Submarines equipped with this type of technology can “bottom,” or sit on the ocean floor, running only essential systems to conserve energy while using passive sonar to detect targets. Since fuel cells work better at lower loads, bottoming can further extend the time of operation of the submarine.
The Kalvari-class submarines will be fitted with an AIP plug, which will house these AIP modules, allowing them to generate hydrogen onboard and supply the necessary power.
The AIP will be added to India’s Kalvari-class submarines, which will improve the country’s naval capabilities, especially in the face of growing maritime threats from adversaries like China and Pakistan. This will enable the Indian Navy to monitor the increasingly assertive Chinese naval presence in the Indian Ocean Region (IOR) without detection.
Both China and Pakistan have already deployed AIP-equipped submarines, putting India at a strategic disadvantage. Pakistan has long operated AIP-equipped French Agosta-90B submarines and is now in collaboration with China for developing Hangor-class submarines that also feature AIP systems.
These developments have made the admittance of AIP into the fleet a gamechanger for the Indian Navy. The Indian submarine force will gain the tactical advantage in the region because India can remain undetected for a long period of time, especially now that the naval presence of China as well as Pakistan is growing in the IOR.
India’s Project-75I and the Role of AIP
The Air indepedent Propulsion technology is of paramount importance, as India’s ambitious Project-75I seeks to acquire six advanced submarines for the Navy. These submarines will be equipped with fuel cell-based AIP systems.
This project now forms a central focus of India’s maritime defense strategy as it seeks to upgrade its underwater warfare capacities to deal with increasing maritime threats from neighboring states.
Project-75I has two contenders: MDL, along with the German company TKMS, and L&T, which has partnered with the Spanish shipbuilder Navantia. TKMS has offered the Type 214 submarine designed specifically to meet India’s needs, while Navantia has offered the S-80 submarine. These options have AIP technology, which is a necessity for the long-term plans of the Indian Navy.
The BEST system from Navantia generates hydrogen onboard from bioethanol fuel, hence giving the submarine a tactical and safety advantage. With this technology, the submarine can remain submerged for three weeks at a stretch.
This increases strategic autonomy and deterrence capability. However, TKMS’s AIP system uses a lithium-ion battery. TKMS has cited the fuel-cell-based AIP system in combination with the lithium-ion battery as a major capability enabler for the Indian Navy.
Earlier this year, the Indian Navy completed its trials of the submarines to be supplied by TKMS and Navantia. According to reports, neither of the two AIP systems tested by the Navy met its very stringent requirements. The S-80 was not even fitted with the Spanish AIP system during field tests, while the German one, though operational, proved to be smaller than desired.
The Indian Navy has not yet decided on a winner for Project-75I, but AIP technology is central to the decision-making process. The Navy’s Request for Proposal for the project stipulates strict criteria, of which Air indepedent Propulsion technology forms one of the most crucial requirements.
Strategic Significance of AIP for India
For India to compete aggressively against its maritime rivals, notably China and Pakistan, this requires an improvement in the country’s underwater capabilities. In the Indian Navy’s strategy, it is not a question of having the largest or fastest fleet; instead, it is being quietest and deadliest for the submarines.
AIP technology is essential for achieving such a strategy, giving Indian submarines the ability to run more stealthily with endurance, making them extremely hard to detect and more strategically advantageous in the area.
As India moves ahead to modernize its submarine arm through Project-75 and Project-75I, the integration of AIP technology developed indigenously is going to be at the very heart of the power that the Indian Navy exercises over the waters of the Indian Ocean. Through modernization of its submarine, the latest in Air Independent Propulsion will be incorporated to protect its maritime interests while keeping an edge on competitors.
