New Delhi: INS Khanderi AIP system upgrade is set to significantly strengthen India’s underwater defence capability. The Indian Navy plans to install an indigenously developed Air-Independent Propulsion (AIP) system on the submarine INS Khanderi by the end of 2026.
The technology has been developed by the Defence Research and Development Organisation (DRDO) and is expected to allow submarines to stay underwater for much longer periods without surfacing. Once integrated, the system will improve stealth, endurance, and operational range of India’s submarine fleet in the Indian Ocean region. Sea trials of the upgraded submarine are expected to begin in mid-2027.
Details of INS Khanderi AIP System Upgrade
The Indian Navy is preparing to install DRDO’s indigenous Air-Independent Propulsion (AIP) system on INS Khanderi, the second submarine of the Kalvari-class fleet.
According to defence sources, the system has already completed extensive shore-based trials and met required technical standards. The integration work is expected to be completed before December 2026 during the submarine’s scheduled refit at Mazagon Dock Shipbuilders Limited (MDL) in Mumbai.
A key component of the system, known as the “energy module,” will be delivered to MDL within the next few months for installation inside the submarine’s hull.
INS Khanderi AIP System Upgrade Trials Timeline
After installation, the submarine will undergo extensive testing.
- Integration completion target: December 2026
- Sea trials expected: July–August 2027
- Full refit completion: Early 2028
These trials will verify whether the AIP system works effectively under real operational conditions at sea.
Why AIP Technology Is Important for Submarines
Traditional diesel-electric submarines rely on diesel engines to recharge batteries. This requires them to surface or use a snorkel every 4–5 days, which increases the risk of detection by enemy radar or sonar.
AIP technology solves this problem. It allows submarines to generate power while staying underwater without using combustion engines. This means submarines can remain submerged for several weeks, greatly improving stealth and mission endurance.
This advantage is crucial in contested waters such as the Indian Ocean Region (IOR), where stealth and endurance are vital for surveillance and deterrence operations.
How DRDO’s Indigenous AIP System Works
The system has been developed by DRDO’s Naval Materials Research Laboratory (NMRL) in Pune.
Key features include:
- Phosphoric acid fuel-cell technology
- Generates electricity underwater
- Produces only water as a by-product, making it environmentally safe
- Enhances stealth and operational endurance
The AIP module will be integrated into the submarine during its mid-life refit.
INS Khanderi AIP System Upgrade: Why INS Khanderi Was Chosen
Originally, the indigenous AIP system was planned for INS Kalvari, the lead submarine of the Kalvari class.
However, the technology was not ready during Kalvari’s refit schedule. As a result, the Navy decided to install the system first on INS Khanderi, while Kalvari continued its refit separately.
This decision reflects a practical scheduling change rather than a delay in the programme.
About INS Khanderi and the Kalvari-Class Submarines
INS Khanderi is part of India’s Kalvari-class (Scorpène) submarines, built under Project-75 at Mazagon Dock with technology support from France’s Naval Group.
The six submarines in this class are:
- INS Kalvari
- INS Khanderi
- INS Karanj
- INS Vela
- INS Vagir
- INS Vagsheer
These submarines form the modern backbone of India’s conventional submarine fleet.
India Joining an Elite Technology Club
Once the AIP system becomes operational, India will join a small group of countries that have developed indigenous fuel-cell-based AIP systems.
This group includes:
- Germany
- Sweden
- Japan
- South Korea
- Spain
- China
Developing the system domestically is considered a major milestone for India’s defence self-reliance (Atmanirbhar Bharat) strategy.
What is the Importance of INS Khanderi AIP System Upgrade for the Indian Navy
India currently operates 16 conventional submarines, but many older submarines are more than 30 years old and approaching retirement.
The indigenous AIP upgrade provides a critical capability boost while India works on future submarine programmes such as Project-75I and next-generation indigenous submarines.
The upgrade will help the Indian Navy:
- Increase underwater endurance
- Improve stealth operations
- Strengthen sea-denial capability in the Indian Ocean
