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Midget/Mini Submarines and AUVs – Force Multipliers for Littoral Defence of India

The author highlights the importance of the midget/mini submarines as well as unmanned underwater vehicles in the defence of India's coast against expeditionary forces. These need to be imperatively included along with coastal missile batteries/ultra long-range guns, patrol crafts, UAVs and USVs etc.

Confined sea spaces, lesser depths, heavy traffic, threats due to lurking quiet diesel submarines, coastal missile batteries, swarms of armed boats, deployed mines and threats from the air, severely compromise a blue water navy's ability to execute manoeuvre in littorals. The definition of a littoral region encompasses water close to the shores as well as greater than 50 nm at sea. The Indian Navy (IN), like all the other blue water navies has not been fundamentally positioned for close combat encounters. It is generally been expected that sea warfare would have standoff distances of at least 50/60 km if not more between adversaries (outside range of torpedoes and guns). If Carrier groups and anti ship cruise missile (ASCM) cruisers are deployed, the standoff can be up to a couple of hundred miles (ASCM and Air craft limits). However, today littorals present an inevitable close quarter engagement situation with Carrier Strike Group (CSG) remaining well clear of coastal missile batteries and aircraft operating from shore based airfields.

A worthy defender is always considered to be in an advantageous position in the littorals, because of the intrinsic knowledge and experience in operating in his home environment. Indian Navy has identified, in all probability, areas in Arabian Sea, Bay of Bengal and Indian Ocean where, should a contingency arise, it may have to engage in littoral conflicts singly, or in concert with coalition of navies. Post 26/11, realising the vulnerability of the coasts to attack by terrorists, the Government of India has initiated efforts to tighten its coastal security. As to the plans of defending own littorals against a formidable expeditionary force, nothing much is known in the open domain, in all likely hood it remains a simplistic defensive model due to insufficient focus and inevitable funding. The fact remains that 'ocean rim state navies' today are focussing more on littoral capability than building a blue water navy. The Indian Navy has to consider the littoral capability seriously whilst modernising and achieve a balance between offence and defence, depending upon its current and future threat perceptions. The blue water force has to have an embedded littoral component force so that the IN can operate in littorals far away from her homeports without worrying about security of its ports.

Operating Littoral Environment
The littorals comprise of different types of zones in which a Navy has to operate. These include continental shelf, surf zones, straits and archipelagos, harbours and estuaries. The main thrust of naval operations hinges upon the underwater acoustics (sonic ray plots) which do not provide an accurate measure of Sonar's effectiveness. In the continental shelf, not much is known about the tactical usage of bioluminescence, plankton or suspended particles and other non-acoustic environmental information. Quantifiable effect on performance of different sensors and weapons under various conditions is also not available to the Commander to help him deploy them optimally. Further, predictions about conditions for naval operations in continental shelf areas of interest are at best sketchy and no reliable database exists to provide correlation between various environmental conditions that may be encountered. In the surf zone region (within 10 m depth line till the beach), temporal and spatial environmental data is required for effective planning of naval operations, however, there are large variations in acoustic data over short and long term. Archipelagos and straits are subject to swift changes in currents and water masses due to restricted topography, dense shipping, fishing and human traffic, which complicate planning. Most of the harbours are estuarine in nature and present a highly intricate and variable environment (tides, currents, wave amplitudes etc) warranting a holistic approach to understand the same.

Thus, it can be seen that carrying out missions in littorals also involve other aspects of environment in addition to the uncertain under water acoustics which have a direct bearing on the missions. These aspects include real time and archival data bases of; meteorological surface conditions required for efficient operation of infra red, electro optical, and electromagnetic sensor and weapon systems; under water topography, accurate bathymetry, bottom composition, and detailed assessment of oceanographic water column environment for under water sensors and weapons.

The availability of overarching oceanic environmental knowledge would provide insight into enemy submarine operating/hiding areas, location of mines and underwater seaward defences. Currently the Indian Navy does not have the capability to carry out exhaustive littoral environmental scanning let alone field any sensor or weapon system that can adapt to the dynamic littoral environment and carry out missions with conviction. In fact, even for own littoral zones this type of information is not available which would enable effective deployment of static or dynamic defences.

Paradigm Shift in Approach to Littoral Defence
Littoral and coastal defence plans of India have undergone a sea change after 26/11; still there is a need for a paradigm shift in the way these defences are perceived as far as Indian Navy is concerned. There is strong possibility of the sea battle being fought in the littorals since the battle may not be waged at open seas. This would bring effective and capable coastal and littoral defence in to sharp focus. The days of the conventional sea fortresses and coastal gun batteries are gone; there is a need therefore to look in to strengthening, extending and backward integrating the complete range of submarine operations from the high seas to Indian littorals. This in turn would imply creating capabilities for littoral and coastal operations and acquisition of suitable class of submersibles like midget/ mini submarines and autonomous under water vehicles.  These could act as defensive force multipliers by converting the environmental disadvantages for the expeditionary forces in littorals, as potential defences against them.

 

Characteristics of AUV
The midget/mini submarines and the autonomous underwater vehicle are ideally placed to carry out the task of littoral defence as against the much bigger conventional or nuclear submarines. Some of the characteristics of such craft are-

•    Much smaller and easier to operate in shallow waters.
•    Emits much less noise and can remain undetected.
•    Can detect surface ships and submarines.
•    High-sustained speeds & long endurance.
•    Small size negates effects of squat and hump effects.
•    Detection difficult as they blend well with fishing craft and other coastal shipping craft.
•    Guidance can be provided from ashore or through surface craft.
•    Stay at the  bottom and wait for the enemy.
•    May or may not carry weapons, as they may be tasked for ISR role.
•    Turnaround maintenance can be done by designated surface craft
•    Low cost of acquisition and maintenance.

Doctrinally the midget/mini submarines and AUVs should be integral to littoral/coastal defence. These craft can easily be modified for carrying out additional tasks like, the security of the Indian EEZ and protection of the offshore assets.

Shallow Water Acoustics: Shallow waters pose a serious problem for under water acoustics, they remain unfriendly to current sensors like towed arrays, variable depth sonars and air dropped sono buoys due to depth limitations, deployment of torpedoes (both ship and air launched) and depth charges. Shallow waters with close proximity to land also pose difficulties for radars and magnetic anomaly detectors thus providing a relatively safe operating area for small submarines. Detection of surface craft by submarines in passive sonar mode is much easier because of their higher acoustic signatures. The surface ships would perforce resort to active sonar transmission as their passive capabilities are degraded in littorals. This in turn makes them more acoustically visible. This however, is an advantage for the operation of the submersibles in own waters.

The Unmanned Submarine (Autonomous Underwater Vehicle-AUV):. An AUV is a machine that uses a propulsion system to transit through the water. It can manoeuvre in three dimensions (azimuth, plane and depth), and control its speed by the use of sophisticated computerised systems onboard the vehicle itself. Autonomous underwater vehicles come under the term Unmanned underwater vehicle includes, remotely operated vehicles, paravanes, and sea gliders.

AUV can be pre programmed to adhere to course, speed and depths as desired by the operator, at a remote location and carry out specific tasks utilising a bank of sensors on the AUV. The data collection, both time and space based, is referenced with respect to coordinates of the place of operation. It can operate under most environmental conditions and because of this, they are used for accurate bathymetric survey and for sea floor mapping prior to commencing construction of subsea structures. The Navies use them for detecting enemy submarines, mines, ISR and area monitoring/ denial purposes.

AUVs are on the verge of three developments, which would accelerate their induction into modern navies.

Unmanned Combat Undersea Vehicles (UCUVs): This is virtually accomplished with AUV designs incorporating lightweight torpedoes as weapons of choice. Heavier AUVs are being planned with missile launchers and/or heavy weight torpedoes. New class of weapons specific to unmanned vehicles are already under advanced development. These include much smaller and lighter missiles, torpedoes and guns firing super-cavitating ammunition.

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Radically Extended Operational Ranges: Already, the developed countries have invested in programs to create long-range underwater “sea gliders” to conduct long-range Intelligence Preparation of the Operational Environment (IPOE) missions. While the technologies enabling the “sea glider” approach probably do not provide the flexibility and propulsion power to enable armed AUVs, such programs will significantly advance the state of AUV navigation and communications technologies. Leveraging these advancements, other nascent technologies such as Air-independent-propulsion (AIP), Fuel Cell propulsion, or perhaps Aluminium/Vortex Combustors, could provide the propulsion power necessary to deploy armed AUVs even well outside of the operating area limitations of conventionally powered submarines.

Autonomy: This will allow them the flexibility to conduct operations far away from the homeport. Artificial intelligence (AI) based autonomous control systems are being developed at a rapid pace. Even with current state of missile/torpedo seeker technology, armed AUVs would only need enough autonomy to navigate to a known area of operations and launch the weapon.

AUVs in various configurations and roles such as communication and navigation nodes, environmental sensors in real time or 'lie in wait' weapon carriers are going to be the choice platform in the littorals. Networked operations of unmanned vehicles with PGMs could become the lethal weapon combo for the future. These AUVs could be expendable if required, economically viable, and offer flexibility in design, as being unmanned they can have much lesser degree of safeties.

Procurement
The midget/mini submarines and AUVs can be mass-produced in India and need not to be sent to defence shipyards, as the technology and designs are commercially available. It may be then sent to defence shipyards if weapon fitment is required. These submersibles do not require rigid safety standards of a conventional submarine as they are not required to operate at great depths, speeds or ranges, their operating range could be <100 km, their speed <10 kt, their turn around and nominal maintenance can be outsourced, their sensor packages are COTS items. Being modular in design, the weapon packages can be retrofitted.

Kongsberg Maritime has supplied two survey AUVs to the Indian Navy. Teledyne Gavia, Bluefin Robotics and International Submarine Engineering are already supplying AUVs. Their sizes range from man portable lightweight AUVs to 10 m long, large diameter AUVs.

IIT Mumbai, IIT Chennai, NIOT, and DRDO are some of the Indian agencies working on the AUVs.

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Korean VOGO, manufactures midgets and mini submarines under various classes.
Iran's Ghadir is a bigger diesel/electric midget submarine, about 90 ft long and with a crew of 18 persons. It has two torpedo tubes and is said to be capable of firing tube-launched missiles also.

Recently a RFI has been floated under “Make” Category by the Indian Navy to meet its requirement for at least 10 autonomous underwater vehicles (AUVs). These AUVs are to be developed and productionised within four years of contract finalisation. Modular payload capability of the AUVs have been asked for, where in  payloads like underwater cameras for surveillance reconnaissance and high definition sonars can be mounted.

In conclusion it can be said that induction and embedding of midget/mini submarines and AUVs  in to India's littoral defence schemes merits serious consideration, especially since these craft can be manufactured with commercial technology indigenously and can be fielded in large numbers economically. The asymmetric advantages of defending littorals with these submersibles far outweigh the doctrinal and induction hiccups that may be encountered administratively and operationally. Therefore, there is a need for a policy level intervention to integrate these craft in the littoral defence structure including the security of the Indian EEZ and protection of the Indian Offshore assets.

(The author is a Senior Fellow of the New Westminster College, Canada)

Rear Admiral Dr. S Kulshrestha, (Retd.)

Rear Admiral Dr. S Kulshrestha, (Retd.)

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