Submarine rescue

With six new submarines to be built indigenously India needs to ensure that a deep sea rescue facility is an integral organic component. While India has one submarine rescue vessel in the form of Nishtar any delay in arriving at the scene of an incident can be fraught with danger for the crew.

The Indian Navy has a huge area of responsibility stretching from the southern tip of Africa in the west to the East China Sea. The modern day requirement for search and rescue is for at least inbuilt floatation systems that will lift the stricken submarine to the surface so that the crew is safe.

There are reports that India is interested in acquiring a new submarine rescue vessel that the Russians (who have suffered several submarine accidents in the past) have unveiled. The first of these vessels is to be inducted into the Russian Navy by the end of this year. It carries paraphernalia like evacuation and decompression chambers required to extricate sailors from a submarine that has met with an accident in the deep sea.

Compared to what is the modern-day requirement the Indian submarine rescue ship Nishtar is rudimentary. Commissioned in 1971 it became famous with the recovery of pieces of debris of the Pakistan Navy Ship Ghazi which sank off the coast of Vishakhapatnam while waiting to ambush the Indian aircraft carrier INS Vikrant. Since then it has been used to train divers for deep sea rescue and for mines and explosives clearance tasks in harbours and offshore oil facilities.

Escaping accidents

In any accident involving a submarine at sea the primary task is to ensure that the vessel does not settle to the bottom of the sea. Quite often explosions on board tend to make the vessel lie mast down buried in deep mud at the bottom of the sea. When it is this position or even while lying on its side it is difficult for any rescue vessel to  mate with the submarine escape hatch on the top of the mast. Under such circumstances the first act of the rescuers is to refloat the stricken vessel and put it upright so as to enable the diving bell to dock with the escape hatch. It is a slow process and the only surety is the recovery of dead bodies inside the many sealed cabins of the sunken submarine.

There is technology, several decades old, which ensures that the submarine not only remains in an upright position but rises to the surface fast enough to enable the submariners to activate self-sustaining facilities to ensure survival under flooded conditions. The HDW submarines that the Indian Navy acquired from West Germany (during the cold war) included a detachable module into which the sailors entered and rose automatically to the service.

India bought two ready-to-sail submarines from the HDW shipyard and constructed two more under license at the Mazagon Dockyard Ltd. Such is the nature of license-produced foreign equipment that the know-how of this technology was not shared by the Germans. Now that these submarines are approaching decommissioning, the Indian Naval Design Bureau can reverse-engineer the system and install it on future Indian submarines, especially the next generation of the nuclear powered (and armed) indigenous vessel the Arihant class of submarines.

When negotiations were underway with the French shipyard for six Scorpene submarines there was always talk of retrofitting the air-independent propulsion (AIP) technology that facilitates the vessel to remain submerged for a longer time surfacing to recharge its batteries. While nuclear-powered submarines are the most desirable, the AIP technology allows for several additional weeks of submergence which gives the submarine greater flexibility in operations.

While retrofitting such equipment to existing submarines is an option it can only be utilized when the vessel is brought to dock for its periodic maintenance cycle. This itself becomes extended because of the need to strip the hull to facilitate reconstruction putting already scarce assets out of operational use. The Indian Navy will have to strive to fit such components at the drawing board stage itself.

Rapid surfacing

The inclusion of integral floatation technology presents itself as the “first responder” in a disaster management situation involving submarines at sea. By retaining and maintaining the upright attitude of the stricken platform the system known as RESUS (acronym for Rescue System for Submarines) ensures automatic retrieval from any depth. Most specifically, it prevents the submarine from settling to the bottom of the ocean and becoming covered in deep layer of mud on the ocean floor where death of submarines becomes a foregone conclusion. Along the way it also prevents the submarine from sinking below the capacity of the hull to sustain the incremental pressure per square foot of water that could crush the submarine and further complicate the original disaster.

The RESUS is a stand-alone system capable of being configured for manual or automatic operation. It is deployed at several points most usually at the forward end and near the propeller in the aft chamber to ensure horizontal attitude. There are also several other locations that can be activated to ensure complete stability. The solid or liquid catalyst triggers hot gas formation which can be modulated to meet different kinds of requirements for different submarines. The total number of gadgets required is based on calculations of amount of water to be displaced, submarine depth and extent of damage to the hull.

The number of gas generators needed for rapid surfacing depends on the class of the submarine based on its displacement; the actual diving depth; and the volume of the main ballast tanks.

The required number of gas generators to be fired is determined by the Control and Test Unit which determines the diving depth measured by the Diving Depth Measuring Device. The system is designed to achieve rapid buoyancy which saves not only the lives of the submariners but also the submarine superstructure which can be repaired at a drydock immediately.

As a first responder the system behaves like a prophylactic intended to prevent further damage or loss of personnel. As it approaches the surface of the sea the rescue support vessels and their onboard remotely operated vehicles can approach the submarine escape hatch and achieve a lock on. From then the injured submariners can be evacuated in recompression chambers that ensure a greater degree of survival. The chances of saving both submarine and submariners is much greater than other available systems.

It is a system that has been in existence for more than a quarter of a century. It is a spinoff from France’s Ariene space launch projects involving Airbus Space Systems. Now that the six proposed Indian submarines are still in the drawing board stage it would be appropriate to involve the Indian Space Research Organisation to see whether similar transfer of technology is possible for the Indian submarine project.  After all ISRO has perfected several different types of launch vehicles (the latest being the GSLV) and it would be aware of the technicalities involved given that RESUS is based on space propulsion technologies.

It is time not just for ISRO to branch out but also for the Indian Naval Design Bureau to become innovative in the next generation of submarines particularly the nuclear-powered submarines that India will build.