Air Independent Propulsion Technology

Air Independent Propulsion Technology

News: Recently, France’s Naval Group declined the bid for the P-75I Project, citing it does not use AIP (AirIndependent Propulsion) Technology yet.

About:
• AIP is a technology for conventional non-nuclear submarines.
• Submarines are essentially of two types: conventional and nuclear.
• The conventional submarines use diesel-electric engines, which require them to surface almost daily to get atmospheric oxygen for fuel combustion. If fitted with an AIP system, the submarine will need to take in oxygen only once a week.
• The indigenously developed AIP, which is one of the key missions of the Naval Materials Research Laboratory (NMRL - DRDO), is considered one of the ambitious projects of the DRDO (Defence Research and Development Organisation) for the Navy.

What is Fuel Cell Based AIP system? 
• In a fuel cell based AIP, an electrolytic fuel cell releases energy by combining hydrogen and oxygen, with only water as the waste product ensuring less marine pollution. The cells are highly efficient, and do not have moving parts, thus ensuring that the submarine has a low acoustic emission of sound.

How does AIP help?
• AIP has a force multiplier effect on lethality of a diesel electric submarine as it enhances the submerged endurance of the boat several fold.
• Fuel cell-based AIP has merits in performance compared to other technologies.
• AIP technology allows a conventional submarine to remain submerged for much longer than ordinary diesel-electric submarines.
• All conventional submarines have to surface to run their generators that recharge the batteries that allow the boat to function under water. However, the more frequently a submarine surfaces, the higher the chances of it being detected. AIP allows a submarine to remain submerged for more than a fortnight, compared to two to three days for diesel-electric boats.

Limitations of AIP:
• Installing AIP increases the length and weight of the boats, requires pressurised liquid oxygen (LOX) storage on-board and supply for all three technologies.
• MESMA (Autonomous Submarine Energy Module) and the Stirling engine have some acoustic noise from moving parts; and the submarine’s unit cost increases by around 10%.