India begins key testing phase for indigenous submarine air-independent propulsion tech
The DRDO-designed fuel cell system will undergo rigorous power testing at Hazira before integration into a Kalvari-class submarine in 2027.
India has officially begun the second phase of testing for its home-grown submarine propulsion technology, marking a major step forward in strengthening national maritime security and defence self-reliance.
The Ministry of Defence announced that the 'Setting to Work Phase-2' activity for the energy module of the Air-Independent Propulsion (AIP) system was inaugurated at Larsen & Toubro's AM Naik Heavy Engineering Complex in Hazira, Gujarat.
Developed by the Naval Materials Research Laboratory, a specialised unit of the Defence Research and Development Organisation (DRDO), the system is designed to significantly boost the underwater endurance of diesel-electric submarines by reducing their need to surface for atmospheric oxygen.
Once Phase-2 testing is complete, the module will undergo rigorous evaluation under Indian Navy standards before being delivered to Mazagon Dock Shipbuilders Limited in Mumbai. The Navy plans to integrate the indigenous AIP system into a Kalvari-class submarine in early 2027.
Advancing defence technology and industrial capability
Virtually attending the ceremony, Defence Secretary Rajesh Kumar Singh praised the scientific collaboration between DRDO and its private sector partners, highlighting how joint industrial efforts have turned advanced indigenous engineering into practical reality on the factory floor. Singh noted that close coordination between the Navy and DRDO during every stage of development and validation has been vital to reaching this operational milestone.
He urged development teams to maintain strict safety standards throughout the upcoming testing phase, acknowledging the specialized protocols needed when handling hydrogen fuel cell systems.
Vice Admiral B Sivakumar, the Navy's Chief of Materiel, and R Balamuralikrishnan, DRDO's Director General for Naval Systems and Materials, attended the Hazira event in person alongside engineering teams.
How the AIP module enhances submarine endurance
Conventional diesel-electric submarines must routinely rise to periscope depth to run their diesel engines and recharge batteries, exposing them to radar and satellite detection—a vulnerability known as snorkelling. The fuel-cell-based AIP technology solves this by generating power internally through hydrogen and oxygen reactions, allowing the vessel to stay submerged for far longer periods.
| Project Stage | Lead Unit / Organisation | Target Facility / Schedule |
|---|---|---|
| Module Design & Development | Naval Materials Research Laboratory (DRDO) | Lab-scale validation |
| Phase-2 Activation & Testing | Larsen & Toubro | AM Naik Complex, Hazira |
| Submarine Integration | Mazagon Dock Shipbuilders Limited | Early 2027 |
The successful operational deployment of this indigenous fuel-cell system will place India among a selective group of global nations possessing advanced submarine endurance technology, reinforcing stability and domain awareness across the Indian Ocean Region.
Key numbers
| What | Figure | Source |
|---|---|---|
| Target submarine integration date | Early 2027 | Ministry of Defence |
| Testing location | AM Naik Heavy Engineering Complex, Hazira, Gujarat | Ministry of Defence |
| Module developer | Naval Materials Research Laboratory (DRDO) | Ministry of Defence |
In this story
| Name | Role in the story |
|---|---|
| Hazira | Location of the L&T heavy engineering facility where testing began. |
| Larsen & Toubro | Hosting and executing the Phase-2 testing at its Hazira facility. |
| Indian Navy | Will validate, test, and integrate the system onto its submarines. |
| Mazagon Dock Shipbuilders Limited | Will carry out the integration of the AIP system onto the submarine. |
| Defence Research and Development Organisation | Developed the air-independent propulsion system energy module. |
