Why Air-Independent Propulsion submarines are stealthier than diesel, nuclear counterparts EXPLAINED as Indian Navy closer to getting German Type 214s

When German Chancellor Friedrich Merz reaches India for two days on 12 and 13 January, the two democracies could agree on a deal to build submarines for the Indian Navy, a report said. It is the Type 214 conventional submarine with Air-Independent Propulsion (AIP) that India wants to buy from the European power and build domestically.

THE WEEK had reported earlier that if the deal with Germany goes ahead, India may cancel plans to buy three more submarines from France. However, it is to be noted that there is no official confirmation from the defence ministry regarding such a deal.

The deal involves India spending around $8 billion to build six submarines in collaboration with ThyssenKrupp Marine Systems (TKMS) and Mazagon Dock Shipbuilders Limited (MDL), The Tribune said in a report. It was in June 2025 that the Mumbai-based MDL signed the MoU to construct six stealth submarines using the latest technology from Germany-based ThyssenKrupp, the report added. The Indian Navy had sought operational AIP technology, which would allow a submarine to remain underwater for up to six days.

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ThyssenKrupp Marine Systems is entrusted with the design and engineering aspects of the project, along with consultancy support, while the building and delivery part is the responsibility of the state-owned MDL, The Tribune report said.

What are Air-Independent Propulsion submarines?

According to the  TKMS website, the 214NG subs are equipped with fourth-generation AIP systems, which "can operate with an exceptionally low acoustic signature." They are well-suited for surveillance and reconnaissance in coastal environments, covert insertion missions and denial of access in strategic chokepoints, the manufacturers claim. 

In simplest words, Air-Independent Propulsion (AIP) is a technology that allows non-nuclear-powered submarines to operate without access to atmospheric oxygen. AIP systems generate electricity to turn the propeller or charge the batteries and make the submarines quieter than even nuclear-powered models. Since they produce lower heat signatures than diesel engines or nuclear reactors, the "stealth" property of AIP subs remains intact when challenged by thermal sensors.

Currently operated by the naval forces of South Korea, Portugal, Türkiye, and Greece, the Type 214 submarines are developed exclusively for export. They are capable of deploying heavyweight torpedoes, anti-ship missiles, and mines.