What happened to 18 sailors that were onboard is not yet known, apart from 4 whose dead bodies were recovered recently.
If a tragedy like this would have happened with a U.S. Navy vessel, could the personnel onboard be saved?
The answer is yes and there are two ways to go about it: one is that a tethered chamber is lowered to the crippled submarine and then raised with the sailors, another is by using a deep submergence rescue vehicle (DSRV), Discovery News reported.
The U.S. Navy is known to use tethered method, which has three components - one each for every stage of a rescue operation.
In the first stage of Submarine Rescue Diving Recompression System (SRDRS), a diver wearing a specialized suit, called an atmospheric dive system, which is capable of reaching depths of 2,000 feet, swims to the sub to make sure that the hatch is accessible and if there are any survivors.
Once it is clear that people have survived and are trapped inside and the hatch is in working condition, the next step taken is to call in a remotely operated vehicle, called a pressurized rescue module (PRM) - typically crewed by two people, the vehicle - which is also capable of diving to 2,000 feet, is able to hold an additional 16 people. It links to the submarine hatch using a 'skirt,' which is essentially a tube covering the hatch and pushes out the water with pressurized air.
The outside water pressure is able to seal the tube onto the hatch the same way air pressure holds a suction cup to a wall.
The sailors then make an exit from the submarine through the skirt, they then board the PRM and go up to the surface where it docks with a larger pressure chamber.
The chamber then lowers the air pressure inside until it matches that outside in order to avoid giving the rescued sailors decompression sickness.
--ANI (Posted on 17-08-2013)