IN Brief:
- India’s DRDO inaugurated Setting to Work Phase 2 of the indigenous AIP energy module at L&T’s Hazira engineering complex on 24 October.
- The module is due to be energised and tested under Indian Navy protocols before it is handed to Mazagon Dock Shipbuilders.
- Integration with a Kalvari-class submarine is planned for early 2027; operational acceptance has not yet occurred.
India’s Defence Research and Development Organisation has inaugurated Setting to Work Phase 2 for an indigenous air independent propulsion (AIP) energy module intended for diesel-electric submarines. The 24 October 2026 milestone took place at Larsen & Toubro’s AM Naik Heavy Engineering Complex in Hazira, Gujarat, ahead of planned energisation and controlled power-production testing.
The Naval Materials Research Laboratory, a DRDO establishment, developed the energy module with Indian industrial partners. The assembled equipment is due to undergo power generation tests under Indian Navy protocols before handover to Mazagon Dock Shipbuilders for planned integration with a Kalvari-class submarine in early 2027. The October event does not establish that power-production tests have been completed or that an AIP module has entered operational submarine service.
Air independent propulsion, or AIP, is intended to extend the period during which a conventionally powered submarine can remain submerged without relying on atmospheric oxygen drawn in from the surface. A conventional diesel-electric boat generally uses batteries for underwater propulsion and diesel generators when atmospheric oxygen is available. AIP adds an alternative route for generating electrical power while submerged.
The capability does not eliminate the submarine’s need to manage stored energy, consumables or onboard electrical demand. How much endurance it adds depends on the actual power output, stored reactants, auxiliary loads and the propulsion regime being used. The ministry has not disclosed this energy module’s electrical rating, fuel capacity or expected submerged endurance gain, so precise performance comparisons would be premature.
DRDO identifies hydrogen and fuel cell technology as central to the programme’s safety requirements. A fuel cell generates electrical power through electrochemical reactions rather than combustion, but needs controlled delivery of reactants as well as thermal, electrical and fluid management. These supporting systems occupy space and consume some of the power produced, which is why the module’s net output and installed endurance must be measured in the intended operating configuration.
A functioning AIP installation nevertheless includes much more than an energy conversion unit. Operators must control reactant storage and distribution, pressure, temperature, electrical output and waste handling. Protective systems must detect abnormal conditions and place equipment into a safe state. The integration design must also account for the submarine’s available volume, mass distribution and existing electrical architecture.
Setting to Work Phase 2 is a commissioning milestone, not final qualification for shipboard use. The next declared activity is to energise the complete energy module and demonstrate power generation against the Navy’s test protocols. Results must show that its controls, fuel supply, cooling and electrical output operate together reliably before the equipment can be transferred for integration into a submarine.
Initial power testing can expose issues that may not appear in individual component trials. Pumps, valves, sensors, electrical converters and control software must respond coherently when load changes, safety thresholds are approached or a subsystem is isolated. Testing under a defined naval protocol is intended to determine whether the assembled equipment performs within the required operating envelope.
Hydrogen handling creates particular safety requirements: leaks, accumulation in confined spaces and ignition sources need to be detected and controlled. A submarine has restricted internal volumes and limited options for isolating failed equipment, so fault detection, ventilation or containment provisions and safe shutdown behaviour have to be assessed as part of system integration. DRDO has stressed that naval induction cannot compromise the safety culture needed for hydrogen and fuel cell equipment.
L&T’s Hazira engineering complex is providing the setting for the current industrial phase. The eventual receiving shipyard, Mazagon Dock Shipbuilders, will have to manage structural and services integration with the intended Kalvari-class submarine. Equipment interfaces, foundations, cabling, controls and maintainability must be compatible with the selected vessel and its approved configuration.
The receiving submarine’s electrical distribution must accommodate the AIP module alongside its existing batteries and propulsion-related loads. Cooling, cabling, controls and safe isolation arrangements must work in the installed position, not just on the factory test stand. Installation will also be constrained by access to machinery spaces, equipment foundations and the maintenance clearances approved for the selected hull.
The Kalvari class is the Indian Navy’s conventionally powered submarine programme based on the Scorpène design. Retrofitting or integrating a new propulsion energy module into a submarine requires careful scheduling, particularly where hull access, machinery spaces and ship acceptance trials are involved. The October announcement does not identify a completed installation or a vessel already operating with the new module.
DRDO’s Naval Materials Research Laboratory leads the underlying research, while L&T provides the present engineering and test setting and Mazagon Dock Shipbuilders is designated for the subsequent shipyard work. Progress through these separate stages would develop Indian manufacturing and validation experience, but a functioning module on a factory test stand still requires vessel integration, safety assessments and acceptance work before operational use.
Early 2027 remains the stated target for handing the tested module to the submarine integration programme, not a confirmed date for an operational AIP-equipped boat. The next published evidence to assess will be power-production test results, completion of naval verification and the handover to Mazagon Dock Shipbuilders. Installation and any subsequent harbour or sea trials are further milestones beyond the October commissioning event.
