By Anjali Ojha
New Delhi, Nov 5 (IANS): Indian scientists have developed technology that will enable the navy's conventional non-nuclear submarines stay under water for up to two weeks before replenishing their oxygen supply, thus increasing their stealth capabilities.

"Conventional submarines usually need to come to the surface every three to four days for replenishing their oxygen supply," an official of the Defence Research and Development Organisation (DRDO), which has developed the Air Independent Propulsion (AIP) system, told IANS, speaking on condition of anonymity.

For the replenishment, a diesel submarine has to come to periscope depth and raise its snorkel, which makes it vulnerable to detection.

"With AIP, a conventional submarine can stay under water for up to two weeks," the official said, adding that India is the only non-Western nation to have developed the technology.

AIP can replace or supplement the diesel-electric propulsion systems of conventional submarines. It also makes a vessel noise-free.

The system, which is in an advanced stage of development, will be mounted on last two of the six Scorpene submarines being manufactured in India in collaboration with France.
These two submarines are expected to be ready in a couple of years, along with the AIP system.

"We took up the project in 2010, and the work is in an advanced stage. The tests are going on," the official said.

The DRDO is also hopeful that the system will be used in the six conventional submarines that were recently cleared for being domestically manufactured.

"So far it is not clear who will be making the six new conventional submarines, but if it is successful in the Scorpene, it will open the door for its incorporation in other submarines as well," the official said.

The system, which is based on a fuel cell, converts methanol-like substances to produce hydrogen, which in turn produces electricity. While diesel engines need oxygen to function, these cells are air independent.

The official said the Naval Materials Research Laboratory (NMRL) based in Ambernath in Maharashtra, which has developed the AIP, has already tied up with several Indian Public Sector Units (PSUs) and the private sector as partners in the project. Production will start as soon as the final tests are over.