Anti-submarine operations

Anti-submarine warfare is a multi-dimensional asset deployment in the water, on the surface and in the air to look for, track, identify and finally destroy an enemy submarine.

With so much ocean space to patrol (Arabian Sea 3,86,200 sq km; Bay of Bengal 2,17,200 sq km, Indian Ocean 70,560,000 sq km), visiting just the littoral waters and the chokepoints in the west and south-east Asia requires massive human effort and a plethora of technical tools.

More and more, to deal with the increasing threat posed by Chinese submarines, India will have to resort to the use of robots, unmanned underwater vehicles and seabed array of sensors to be able to make the first contact with the potentially hostile submarine at arms length from its 7,150 km coastline. To manage this task it has a strategic advantage in the location of its island territories in the Andaman and Nicobar group in the south east Bay of Bengal and the Lakshadweep group off the western seaboard of Kerala. The former dominates one of the most important chokepoints-the Malacca Strait and the southern Indonesian waters.

Detection capabilities

For long-range submarine detection India has been using maritime patrol aircraft first the British Constellations, later the ex-Soviet (Russian) Ilyushin and Tupulov maritime aircraft and currently the American Poseidon P-8I.

With Chinese nuclear submarines making regular forays to the string of naval bases Beijing has acquired over the years straddling Myanmar, Sri Lanka, Seychelles and Djibouti, India needs to beef up its detection capabilities to be able to track and identify Chinese submarines whenever they enter the Indian Ocean or try to creep close to Indian territorial waters. The Colombo visits and the creation of naval facilities at Hambantota in southern Sri Lanka are particularly worrying and demand extraordinary measures to dissuade China from using Sri Lankan hospitality for anti-Indian activities.

India has been steadily adding to its fleet of anti-submarine surface vessels which include the stealth ships Shivalik  frigate and the Kolkata class destroyers. The accent has been on multirole capability on every surface platform. Transiting from the Petya class anti-submarine warfare vessels the Kamorta class corvettes (a vessel smaller than frigates) the Indian naval shipbuilders Garden Reach Shipbuilders and Engineers of Kolkata have included a longer range for the Kamorta ships which allows them to protect the cluttered ocean lines of communications from hostile submarines. The larger size allows room for more weapons and fuel and adds a helicopter dedicated to anti-submarine warfare to be an organic part of the ship for which a hangar has been provided. Most of the sensors both underwater sonars and surface radars are indigenous. With the first two of four already delivered to the Indian Navy there are expectations that a follow-on order of eight would give the Indian Navy a significant boost in its anti-submarine capability.

With a range of more than 6500 km at a speed of 18 knots (about 33 kmph) the Kamorta will provide blue water coverage of the entire Indian Ocean littoral. Its integral helicopter helps provide a wide arc of security given that the helicopter can deploy both dipping sonars to test several levels of the ocean (including thermal layers within which submarines can hide) or deploy sonobouys the signals from which are transmitted via satellite to all airborne and surface weapons platforms for concerted action against the lurking submarine. The helicopter itself can fire torpedoes.

ASW network

Part of the multi-layered anti-submarine network is the long-range maritime reconnaissance and strike aircraft Poseidon P-8I acquired from the US. Eight of the aircraft have arrived and a total of 16 are to make up this airborne platform which contains several indigenous sensors like the ‘identification friend or foe’ and the data link to enable network centricity with all fighting platforms of the Indian Navy. The aircraft has a range of 2,222 km but the distances to the outer edge of the Indian Ocean littoral are more than 3,000 km on either side of the Indian peninsula. Having to travel further would eat into the “time on station’ of four hours.

India will have to incorporate a refueling nozzle on its Poseidon fleet of maritime strike aircraft to increase its range to be able to police effectively the two major chokepoints that lie around Indonesia in the east to the Cape of Good Hope in South Africa in the west.

Another extremely useful tool for anti-submarine operations is what is known as the seabed array of sensors that can record the acoustics of passing vessels and helps create a dossier that can be used to identify the engine/propeller sounds with the name of the vessel. By elimination over time a ship or submarine belonging to an inimical neighbour can be identified and suitable counter-measures taken. There are plans to send aloft a dedicated satellite to keep an eye out on activities around the coast of peninsular India. The seabed array would provide real time information about any intruders into what is increasingly being described as a “littoral” intrusion into the Indian Ocean region.

The Naval Physical Oceanographic Laboratory is working on the project to lay seabed arrays that will contribute to the study of underwater acoustics that have a critical bearing on the detection of enemy submarines. The data collected by the seabed arrays will identify the effect of acoustic transmission. It is well known that the sound tends to bend and be deflected away from the sonar that is looking for underwater objects. These thermal layers need to be studied so as to be able to evolve techniques that will enable a penetration of a thermal layer to see if any submarine is hiding within it.

It is imperative that the Indian Navy conduct a sustained study of this phenomenon because it is becoming very apparent that the Chinese Navy has been studying the phenomenon during its frequent passages through the Indian Ocean littoral. It needs to be recalled that during a standoff in the South Pacific Ocean a Chinese submarine managed to penetrate the security screen of its anti-submarine network around a US aircraft carrier. This could not have happened without a thorough knowledge of the phenomenon of the distortion of sound while travelling through layers of ocean with deferring temperatures.

It is a slow and laborious job spread over different seasons in the region. To be able to execute that it would be useful to have robots to plumb the depths of the oceans around the Indian peninsula. These robots can help collect data about oceanic conditions in general and also be used in direct combat if, as in aerial warfare, the unmanned underwater vehicle is also armed.

The much-maligned Defence Research and Development Organization has produced an autonomous underwater vehicle (AUV) that can undertake tasks like studying the thermal layers and the effect on them of seasonal changes in temperature. The AUV created jointly by the Electronics Corporation of India and the Naval Science and Technology Laboratory is equipped with passive sonar for surveillance and intelligence gathering, mine detection and can operate down to a depth of 100 meters from shore or ship. Efforts are on to include mine laying in its repertoire. Slowly but surely India is improving its maritime defences.