Larsen and Toubro and Pipavav Defence, in which Reliance Infrastructure of Anil Ambani Group is acquiring a majority stake, have been shortlisted for the Rs.60,000-crore potential contract to build six submarines for the Indian Navy, sources said.

“Project 75i, as we call it, is for purchasing six next-generation submarines with air independent propulsion (AIP) system for the Indian Navy over the next seven-eight years. It can fire both torpedoes and missssiles,” said a senior official in the defence ministry.

“L&T and Pipavav have been soortlisted. This was based on the recommendations from a high-level committee that had inspected the shipyards of several companies, both private and state-run, to zero in on the potential candidates,” the official added.

The government had given its clearance in three years ago for six submarines with AIP capability and subsequently decided last year to go for their construction on Indian yards as part of Prime Ministrer Narendra Modi’s “Make in India” campaign.

As against the initial import of two submarines, it was decided to make all the six submarines in India, as part of the effort to create defence infrastructure within the country while going for the best suitable collaboration with a foreign vendor under transfer of technology.

L&T’s mega shipyard, where the company intends to execute the project, is at Kattupalli, about 40 km north of Chennai, on the east coast. This complex also includes a container port and a modular fabrication facility.

Pipavav’s facility is at the location by the same name on the Gujarat coast and claims a modern, versatile engineering and fabrication facilities with shipbuilding infrastructure that is also suitable for the construction of a wide range of warships and submarines.

Of the Rs.123,000 crore cleared late last year for defence purchases, a whopping Rs.60,000 crores has been set aside for these six stealth submarines.

According to defence experts, what makes these Project 75i submarines unique is that they could be powered by an indigenous AIP system that enables them stay underwater for longer periods than conventional boats that have to frequently surface to recharge their batteries.

“Conventional submarines usually need to come to the surface every three-four days for oxygen,” said an official of the Defence Research and Development Organisation(DRDO) that has developed such a system. “But qith AIP, they can stay for under water for two-three weeks,” he said.

“It makes the vessel noise-free. India is the only non-Western nation to have this technology.”

The official said the Naval Materials Research Laboratory, based at Ambernath in Maharashtra, which has developed the AIP, has already tied up with several state-run firms and the private sector as partners in the project. Production will start as soon as the final tests are over.