Homegrown AIP tech is best fit for Scorpene submarines: DRDO

The Defence Research Development Organisation (DRDO) is in the process of developing air independent propulsion (AIP) technology for future Indian-built submarines. Though the novel process, which allows submarines to remain submerged longer, was meant to be an integral part of the last two Scorpene submarines being built at Mumbai’s Mazagon Docks under Project-75, several crucial deadlines were missed.

“The delay in developing the home-grown technology led to the Indian Navy deciding to go ahead with the first lot under Project-75 without incorporating the AIP system,” said a DRDO official, seeking anonymity. “Six years down the line after the submarines are inducted, they would automatically come in for a refit. It is then that the AIP modules would be installed in all the six vessels,” he added.

An AIP system allows a submarine to run its electric motor and other electrical systems without using the batteries. Its inclusion reduces the frequency with which the submarine has to surface to suck in air for the diesel engines to recharge the batteries.

DRDO is being helped in its task by its lab at Ambernath called the Naval Materials Research Laboratory (NMRL). Officials at the lab told BusinessLine that two different types of fuel cells for AIP operation were being developed at the centre, and would be installed in the Scorpene, the diesel electric submarine.

“It is an non-nuclear alternative. While one incorporates a phosphoric acid fuel cell (PAFC), another has a polymer electrolyte fuel cell. It provides longer endurance under submerged conditions by supplementing the lead acid batteries,” an official said.

The AIP would provide “higher stealth and acoustic silence”, which were the main characteristics for underwater vessels, the official adding it would reduce the risk of exposure of the vessel since it would negate the need to surface frequently.

“The homegrown AIP system is the best fit for the Scorpene submarines,” a senior official at NMRL said, maintaining the “PAFC powered AIP modules would be integrated in the Scorpene.” The official added that NMRL has transferred the PAFC technology to Thermax Ltd in Pune for further production.

The official said though major naval powers like the US, the UK, and Russia turned quickly to nuclear propulsion for their submarines, smaller navies have remained committed to conventional diesel electric submarines. Many have incorporated innovations, including the DRDO.

The growing demand for longer underwater endurance has led to several countries presenting promising AIP technologies. Speaking of global AIP technologies that use the fuel cell system, an NMRL official said, “Germany has PEMFC (Proton Exchange Membrane Fuel Cells) technology which is in use by many countries, while Russia's AFC is a diesel reformer, at prototype level. Similarly, France and Spain's PEMFC (Polymer Electrolyte Membrane Fuel Cells) is a diesel reformer at prototype level. DRDO, on the other hand, has a PAFC Borohydride, an advanced prototype”

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