Reports indicate India is closing in on a deal with Germany estimated at US dollars 10 billion under what’s called the Project-75I programme to build six AIP-equipped submarines in India. 

The proposed collaboration will be between Mazagon Dock Shipbuilders Limited (MDL), an Indian state-owned shipbuilding yard, and Thyssenkrupp Marine Systems (TKMS), a major German naval shipbuilder.

The AIP submarines can remain underwater without revealing themselves. While diesel-electric submarines are extremely quiet moving on battery power, issues arise when batteries need recharging. Then the sub must be near the surface and run its diesel engines using atmospheric oxygen. They can be discovered. 

Air-independent propulsion, or AIP, is designed to lengthen the interval between these risky charging periods. No need for oxygen from the atmosphere. Fuel cells use stored reactants to produce electricity electrochemically, recharging or conserving batteries while remaining fully submerged. These AIP submarines are most useful for quiet, low-speed patrols.

German Ambassador Philipp Ackermann has said the proposed programme could be announced shortly.