What is in news : Kickstarting the formal process for building six conventional submarines indigenously under the Project 75 India or P-75I, the government issued a Request for Proposal (RPF) to the two selected Indian Strategic Partners (SP)

AIR INDEPENDENT PROPULSION (AIP) TECHNOLOGY IN SUBMARINES

• Submarines are essentially of two types: conventional and nuclear. Conventional submarines use a diesel-electric engine, and must surface daily for oxygen for fuel combustion. If fitted with an Air Independent Propulsion (AIP) system, the sub needs to take in oxygen only once a week.
• In a fuel cell AIP, an electrolytic fuel cell releases energy by combining hydrogen and oxygen, with only water as the waste product. The cells are highly efficient, and do not have moving parts, thus ensuring that the submarine has a low acoustic signature. Older submarines can be adapted to the AIP system by retrofitting.
• A fuel cell-based AIP, like the one developed by DRDO, is known to deliver better performance compared to other technologies.

PROJECT 75 I

• Project-75(I) envisages indigenous construction of six modern conventional submarines (including associated shore support, Engineering Support Package, training and spares package) with contemporary equipment, weapons & sensors including Fuel-Cell based AIP (Air Independent Propulsion Plant), advanced torpedoes, modern missiles and state of the art countermeasure systems.
• This would provide a major boost to the indigenous design and construction capability of submarines in India, in addition to bringing in the latest submarine design and technologies as part of the project