The Navy’s saturation divers, often referred to as ‘aquanauts’ given their underwater exploits, are on a high having hit a new low when they bettered their own national record by diving to a depth of 257 metres some 35 nautical miles off Kochi on January 9.
On Saturday, Lieutenant Malkeet Singh along with clearance divers Mukesh Kumar, BS Bora, Rithesh Kumar, M. Kumar and Satender Sharma emerged from the Deck Decompression Chamber (DDC) aboard the Navy’s only submarine rescue and diving support vessel INS Nireekshak after completing the mission that lasted 12 days and 18 hours.
The divers, after a month-long preparation involving lessons in first aid, had entered the DDC on January 7 and were saturated, using a mix of helium and oxygen, for the desired depth in a staggered fashion so as to avoid high-pressure health hazards.
Once they acclimatised themselves to the targeted depth, the DDC was mated to the submersible diving capsule, ‘Bell’, which was subsequently lowered undersea through a ‘moon pool’ on the ship’s deck.
The ‘Bell’ sports an umbilical chord through which breathing gas and hot water to keep the divers warm are supplied. It also has two-way communication facility.
At depths ranging from 250 to 257 metres, Lt. Singh and divers Mukesh Kumar and Bora swam out in full diving gear to accomplish the daunting feat in freezing temperatures. It took eight days to decompress the team back to atmospheric pressure.
The deepest dive so far had been 233 metres undertaken by Nireekshak’s divers in 2011.
Inside the monotonous decompression chamber (the ship has one in stand-by, too), the divers do a lot of reading, take tests to revise their theoretical understanding of the specialised field, and watch films or listen to music relayed to them.
“As high-pressure makes their speech, which comes with a heavy nasal twang, almost scrambled, descramblers are used at the control room to communicate with them. We also provide them slates for jotting down what they want to say. They are on round-the-clock monitoring… We did a bit of experimentation this time by offering them a keyboard and mouse remotely linked to a computer outside. While this worked, we have to be careful in using electronic gadgets inside as batteries have hydrocarbons which can explode under pressure,” said Commander Sandeep S. Sarna, Commanding Officer of Nireekshak.
He pointed out that setting a new diving frontier was significant for the Navy in view of the ship’s tasks of salvage and submarine rescue operations.
Deep sea diving can only be undertaken by specialist saturation divers. “Water pressure increases as you go down. For instance, at a depth of 250 metres, the pressure is 26 times more than the atmospheric pressure, where chances of nitrogen narcosis and other decompression sickness can prove lethal. This is what makes saturation diving so crucial,” Lieutenant Commander Ashish Jaitly, Nireekshak’s Diving Officer, who coordinated the mission, said.
Retrofitted with a dynamic positing system which is key to submarine rescue and extending life-support to submarines in distress, Nireekshak has carried out many salvage operations, among which was the recovery last year of fishing boat Don-1, which sank off the coast of Kerala following a collision with merchant vessel Prabhu Daya.
A few months ago, it took part in a submarine rescue exercise alongside the US Navy. While Nireekshak’s submarine rescue capability (deployment of its submarine rescue capsule) has a depth ceiling of 150 metres, it is designed to perform salvage and rescue operations up to 300 metres underwater.
The specialised vessel is now slated to take part in submarine rescue operations off Mumbai in February.