New Delhi: India’s Defence Research and Development Organisation (DRDO) built the Land-Based testing of the indigenous Air-Independent Propulsion (AIP) is going to take some time before it gets operationally ready to be fitted on the submarines of the Indian Navy.

However, prior to a Defence Quality Assurance (QA) approved ‘productionised’ version is available for operational exploitation onboard Kalvari-class submarine, the Ministry of Defence and Indian Navy have options open to procure AIP system from an international supplier.

“While the preference will be given to the indigenously made AIP, keeping the submarine performance issues in mind in the face of the hostile situation in the waters, options are always open to buy urgently from vendors who meet all parameters,” said a top source.

Six Kalvari class (Scorpene) diesel-electric attack submarines (SSKs) under Project 75 are being built by Mazagon Dock Limited (MDL) with the support and technology transfer (ToT) from French company Naval Group (former DCNS). As has been reported earlier, two out of six submarines have been commissioned.

“An Air-Independent Propulsion (AIP) system onboard a submarine allows conventionally powered submarine to operate without access to the outside air. A Kalvari Class submarine when fitted with an AIP system onboard shall be able to run its electric propulsion motor and electrical network while bypassing the conventional batteries. This shall allow it to remain submerged for a longer duration by reducing the need to surface often to take in the air for running diesel engines for charging conventional batteries,” explains Milind Kulshreshtha, a C4I expert.

Though the Kalvari class submarines are powered by conventional diesel-electric propulsion systems, as per the original plans the last two submarines were to be equipped with an indigenously developed AIP technology. This state of the art Fuel-cell based AIP design was taken up by the DRDO for indigenous development since such technology from abroad was extremely expensive. The fuel cell-based AIP uses hydrogen and oxygen to generate electricity has almost no moving parts (making them quieter) and produces minimal waste.

The indigenous AIP system is still at a developmental stage while pending four Submarines under the project are scheduled for commissioning in the next two years. The Made in India AIP system is therefore already planned to be retrofit onboard first submarine which enters a major refit.