India’s Submarine Building Programmes (Project 75 & 75I)
To protect its massive coastline and secure the Indian Ocean Region, the Indian Navy requires a highly advanced underwater fleet. The backbone of this modernisation effort relies on two critical initiatives: Project 75 and its successor, Project 75I.
The Background: The 30-Year Submarine Plan
In 1999, the Ministry of Defence (MoD) approved a highly ambitious 30-year plan to construct a total of 24 submarines natively to boost India’s underwater combat capabilities.
- This massive plan was divided into phases. The first phase focused on building submarines with foreign assistance and technology transfer.
- In 2001, the Indian Navy officially selected the Scorpene-class design, offered by the French naval firm Armaris (now Naval Group), along with an agreement for Transfer of Technology (ToT).
- This initial phase became formally known as Project 75, aiming to build six Diesel-Electric Attack Submarines (SSK) in India at Mazagon Dock Shipbuilders Limited (MDL).
They are all named after deadly deep-sea predators or historic Indian naval vessels:
- INS Kalvari
- INS Khanderi
- INS Karanj
- INS Vela
- INS Vagir
- INS Vagsheer (Note: DRDO is currently developing an indigenous AIP system, which will be fitted into all these Project 75 submarines during their future upgrades to increase their underwater endurance).
Understanding the Technology: What is an AIP System?
Before studying the advanced Project 75I, it is crucial to understand the technology that separates old submarines from modern ones: the Air Independent Propulsion (AIP) system.
- The Problem with Diesel Submarines: Traditional diesel-electric submarines use diesel engines to charge their electric batteries. However, diesel engines require atmospheric oxygen to burn fuel. Therefore, these submarines must come up to the surface (or near the surface using a breathing tube called a “snorkel”) every 48 hours to take in fresh air. When they snorkel, they create noise and expose themselves to enemy radar.
- The AIP Solution: AIP technology acts as an auxiliary (backup) energy source. It uses fuel cells (combining a fuel and an oxidant) to generate electricity chemically, completely removing the need for atmospheric oxygen.
- The Advantage: With an AIP system, a submarine does not need to snorkel. It can remain silently submerged deep underwater for up to two weeks, massively boosting its stealth and survivability.
Project 75I: The Next-Generation Submarines
India does not yet build its own nuclear-powered attack submarines. To train Indian sailors and gain a tactical advantage, India leases the highly capable Akula-class submarines from Russia.
- Type: Nuclear-Powered Attack Submarine (SSN).
- Propulsion: Like the Arihant class, they run on nuclear power and can stay submerged for months. However, unlike the Arihant, they do not carry nuclear missiles.
- Origin: Russian-built submarines leased to the Indian Navy.
- Role: They are designed to travel at high speeds underwater, hunt down enemy submarines, and protect India’s own naval fleet.
- Examples: India previously operated INS Chakra I and INS Chakra II on lease. A new agreement has been signed with Russia for the lease of another Akula-class submarine (expected to be named Chakra III), which is scheduled to arrive around 2028.
Project 75I: The Next-Generation Submarines
India does not yet build its own nuclear-powered attack submarines. To train Indian sailors and gain a tactical advantage, India leases the highly capable Akula-class submarines from Russia.
- Type: Nuclear-Powered Attack Submarine (SSN).
- Propulsion: Like the Arihant class, they run on nuclear power and can stay submerged for months. However, unlike the Arihant, they do not carry nuclear missiles.
- Origin: Russian-built submarines leased to the Indian Navy.
- Role: They are designed to travel at high speeds underwater, hunt down enemy submarines, and protect India’s own naval fleet.
- Examples: India previously operated INS Chakra I and INS Chakra II on lease. A new agreement has been signed with Russia for the lease of another Akula-class submarine (expected to be named Chakra III), which is scheduled to arrive around 2028.
Key Features of Project 75I:
- Factory-Fitted AIP: While the earlier Project 75 submarines lacked this initially, all six submarines under Project 75I will be equipped with state-of-the-art fuel-cell-based AIP systems right from the factory.
- Size and Lethality: These submarines will be physically larger than the Kalvari class. They will carry contemporary sensors and heavy weapons, including long-range, tube-launched land-attack cruise missiles and anti-ship missiles.
- Strict Indigenisation (Atmanirbhar Bharat): The project mandates that the first submarine must have a minimum of 45% indigenous (Indian-made) content, which must scale up to 60% by the time the sixth submarine is built.
- MSME Development: The project is designed to boost India’s core manufacturing sector. It will provide massive opportunities for Micro, Small, and Medium Enterprises (MSMEs) to manufacture associated spare parts, systems, and equipment.
DRDO’s Indigenous AIP Breakthrough
Rather than importing AIP technology forever, India has developed its own.
- The Naval Materials Research Laboratory (NMRL), a branch of DRDO, has successfully developed an indigenous Fuel Cell-powered AIP system.
- Under a recent agreement, this indigenous DRDO system will be integrated into the first Project 75 submarine, INS Kalvari, during its upcoming major refit, upgrading its stealth capabilities to modern standards.
Challenges Facing India's Submarine Ambitions
Despite these strong plans, India’s submarine manufacturing faces several critical hurdles:
- Severe Delays: The original Project 75 was supposed to be completed by 2017. However, the first boat (INS Kalvari) was only commissioned in 2017, and the final boat (INS Vagsheer) is expected to be commissioned around 2024. Project 75I is also lagging heavily and is currently stuck in complex tendering stages.
- Shortage of Submarines: The Indian Navy currently faces a critical shortage. It operates only about 16 functional submarines, many of which are older than 30 years and run on outdated technology. Furthermore, India currently lacks a dedicated, operational Nuclear-Powered Attack Submarine (SSN) fleet.
- Structural Inefficiencies: Testing and integrating new, highly complex technologies (like the indigenous AIP) into tightly packed submarine hulls is structurally difficult and slows down production timelines.
- Exiting Collaborators: Project 75I operates under strict technical demands and liability clauses set by the Indian government. Because of these tough conditions, several major foreign collaborators (including companies from Sweden, France, and Russia) have expressed concerns or exited the initial bidding process, creating uncertainty for the project’s future.
Kalvari vs. Arihant Class
Feature | Kalvari Class (Project 75) | Arihant Class (ATV Project) |
Type | Conventional Diesel-Electric Attack Submarine (SSK) | Nuclear-Powered Ballistic Missile Submarine (SSBN) |
Primary Role | Tactical (Anti-ship, anti-submarine warfare) | Strategic (Nuclear deterrence, second-strike capability) |
Propulsion (Engine) | Diesel engines and electric batteries (Requires surfacing/snorkeling for air) | Miniature Nuclear Reactor (Can stay underwater for months) |
Main Weapons | Heavyweight torpedoes and Exocet anti-ship missiles | K-15 (Sagarika) and K-4 nuclear-tipped ballistic missiles |
Built By | Mazagon Dock Shipbuilders Limited (MDL) with French collaboration | Shipbuilding Centre (SBC) Visakhapatnam with DRDO, BARC, and Russian design aid |
Number of Boats | 6 (Kalvari, Khanderi, Karanj, Vela, Vagir, Vagsheer) | INS Arihant, INS Arighaat (commissioned), and more under construction |
