As the procurement of new submarines under P-75I goes on, the Defence Research and Development Organisation (DRDO) has taken up a preliminary study on the design and development of an indigenous conventional submarine under Project-76, reported The Hindu.

“DRDO got a go ahead from defence ministry to carry out a preliminary study to determine the project contours. It is expected to take upto a year after which a formal case will be put up to the Cabinet Committee on Security (CCS) for project sanction,” a defence source in the know said. This will be a continuation of the Advanced Technology Vessel (ATV) project, to build a conventional submarine, under which the Arihant series of nuclear ballistic missile submarines (SSBN) are being built and another project for building nuclear-powered submarines (SSN) is currently underway, the source stated.

Under P-76, there will be substantial indigenous content, including weapons, missiles, combat management system, sonars, communications, Electronic Warfare suite, mast and periscope, sources said.

The Navy has a 30-year submarine building programme and after the P-75I, it intends to design and build conventional submarines indigenously, senior officials had stated on several occasions.

Air Independent Propulsion

An Air Independent Propulsion (AIP) module designed and developed by DRDO is now awaiting fitment on the Scorpene class submarines. The first Scorpene-class submarine Kalvari is expected to go for refit in 2025 when the fitment process would begin and is expected to take 2-3 years, 2027 or 2028, sources said. This is being done in collaboration with Naval Group, the original manufacturer of Scorpenes.


An AIP module acts as a force multiplier as it enables conventional submarines to remain submerged for longer duration thereby increasing their endurance and reducing chances of detection.

The AIP is currently being continuously run on shore, and as there is no submarine, a simulated hull has been created to have near-sea conditions and also run the same cycles, the source stated. An AIP module is inside a submarine so there is no corrosion issue and the only aspect to be checked in a submarine is the reliability of the AIP module.

The DRDO-developed AIP module is phosphoric acid based which is widely available, officials noted. An AIP module has a stack of fuel cells generating hydrogen. The power output of each fuel cell in the DRDO AIP is 13.5 kW. It is being so asked up to 15.5 kW and will eventually be scaled up to 20 kW which will meet future submarine requirements like the P-76, sources said.

The final configuration of the AIP is a stack of 24 fuel cells and the overall output will be higher than the requirement, to build in redundancy and optimise performance, another source explained.

(With Agency Inputs)