(Published Article in SP’s Naval Forces Oct-Nov 2012)
Victory smiles upon those who anticipate the changes in the character of war, not upon those who wait to adapt themselves after the changes occur.
One of the most salient military technology trends is the growing prominence of unmanned vehicles. The promising potential of unmanned technology has already reached fruition in the air domain in UAVs, as witnessed in the recent global war on terror. There is every indication that there would be similar impact in the undersea domain as in near future Navies aspire to acquire formidable sea denial and sea control capabilities. Incidentally, the first autonomous underwater vehicle was developed by University of Washington in the early 1960’s and was called The Self Propelled Underwater Research Vehicle 1 (SPURV 1). It weighed about 480 Kg, dived up to 3 Kms, and could operate up to 5.5 hrs at 2.2 m/s speed.
An unmanned underwater vehicle (UUV) 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. Generally an UUV can operate from 8 hrs to 50 hrs at a speed between 0.5 m/s to 2.5 m/s. The economic speed is around 1.5 m/s at which it achieves its maximum range. The depth of operation varies between 1000 m to 6000 m. The UUV 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 UUV. The data collection can be both time and space based and is referenced with respect to coordinates of the place of operation.
The UUVs carry out their routine tasks unattended, meaning there by that once deployed the operator is relatively free to attend to other tasks as the UUV reaches its designated area of operation and starts carrying out its mission, be it survey, search, or surveillance. The UUV reports at designed intervals about its technical wellbeing and also about the details of task undertaken by means of communicating through satellite communication, acoustic, or RF modes. The UUV is recoverable at the end of its mission and is available for reuse after maintenance.
The UUVs can operate under most environmental conditions and because of this they are used for accurate bathymetric survey by survey companies and also for sea floor mapping by oil and gas industry prior to commencing construction of subsea structures. The Navies use autonomous underwater vehicles and sea gliders for detecting enemy submarines, mines, ISR, area monitoring and combat purposes; therefore they are outfitted with sensors and weapons and designated as Unmanned Underwater Sensor and Weapon Carriers (UUSWCs) in this article.
The US Navy’s vision for UUSWCs combat deployment has been articulated based upon three tenets, firstly, Sea Strike, which is a broad concept for projecting precise and persistent offensive power from the sea, secondly, Sea Shield which is the concept focused on the protection of national interests by sea-based defence resources and thirdly Sea Basing which endeavours to support versatile and flexible power projection, enabling forces up to the size of a Marine Expeditionary Brigade (MEB) to move to objectives deep inland. The US Navy plans to deploy the UUSWCs for the following purposes:-
-Special Purpose ISR, Harbour ISR, Tactical ISR, Persistent ISR, Clandestine Reconnaissance, OP-AREA Reconnaissance, Inspect / ID.
-Very Shallow Water (VSW) MCM / Shallow water MCM (Coastal / Riverine), MCM Neutraliser, Explosive Ordnance Disposal (EOD)
-Submarine Decoy, Anti Submarine Warfare (ASW)
-Payload Delivery (Mine warfare, ASW, Special operations, EOD, Time Critical Strikes)
-Network Attack, Information operations and electronic warfare.
-Expendable Communication network navigation node (CN3), Mobile CN3.
Sensors Onboard UUSWCs. They currently carry five types of sensors namely; acoustic, magnetic, electromagnetic, optical, and CTD (conductivity, temperature, and depth) sensors.
Active sonars are used to map out their environments and detect objects of interest. Passive sonars are used primarily for ASW missions. Multi beam Obstacle-avoidance sonars use advanced signal processing techniques to obtain maximum information for obstacle avoidance. Beam forming in passive sonars and Synthetic aperture technology in active sonars are current trends. Magnetic compasses, magnetometers, Non traditional trackers, video cameras, non imaging sensors and CTD sensors are the most common sensors in use.
Levels of Autonomy. Six levels of vehicle autonomy have been defined by Office of Naval Research ONR, USA, in order of decreasing autonomy, namely; fully autonomous, mixed initiative, human supervised, human delegated, human assisted and human operated.
Factors that Impact Induction of UUSWCs in The Navy.
Whereas there are definite advantages of using unmanned systems in combat there are some factors which will be deciding the eventual induction and integration of unmanned systems in the Navy.
Space. Navies are always constrained for space on board ships and submarines and UUSWCs would require a demarcated launch, recovery, stowage and maintenance area for them as well as associated logistics. Under this head it would be wise to include the UUSWC operators and maintenance personal and their on board logistic requirements and UUSWC operation rooms. Serious and specific studies would have to be done prior to the induction as this would eventually lead to changes in design of ships and submarines.
Weight and Endurance. These are related issues, the larger the UUSWC the greater the endurance and larger the payload. Thus Navies would have to decide on the endurance required and the payload suitable for the role for which UUSWC would be utilised. The UUSWCs choice would also depend upon the conditions at sea under which it has to operate, which would again have an impact on ruggedisation, weight, endurance and cost.
Currently these vehicles are broadly available in three categories namely:-
Very Small. They have limited endurance (a few hours), limited sensor abilities, must get close to target for performing the assigned mission. However they are relatively inexpensive, hand portable, difficult to detect and could be expendable. One of the battles proven designs is the REMUS UUV.
Medium. This category has weights from upwards of 100Kg to a few Tons. However compared to manned vehicles for carrying out the same tasks, these vehicles weigh much less and can do the assigned tasks with great efficacy. Medium sized UUSWCs role as a communication node has emerged as a predominant mission due to complexities of communication with UUVs. Currently UUSWCs launched from submarine tubes for mine hunting is an example of such vehicles.
Large Vehicles. These are vehicles which weigh a couple of tons or more and carry powerful sensors and/or weapon payloads and can operate over long periods. They can operate under hostile environment for long durations, unsuitable for manned vehicles. Liberdade class flying wing under water glider for tracking submarines for days together is an example of such systems.
Hundreds of different UUVs have been designed over the past 50 or so years, but only a few companies sell vehicles in any significant numbers. There are around 10 companies that sell UUVs on the international market, including Kongsberg Maritime, Hydroid (now owned by Kongsberg), Bluefin Robotics, Teledyne Gavia (previously known as Hafmynd), and International Submarine Engineering (ISE) Ltd.
Vehicles range in size from man portable lightweight UUVs to large diameter vehicles of over 10 metres length. Large vehicle have advantages in terms of endurance and sensor payload capacity; smaller vehicles benefit significantly from lower logistics (for example: support vessel footprint; launch and recovery systems). Most UUVs follow the traditional torpedo shape as this is seen as the best compromise between size, usable volume, hydrodynamic efficiency and ease of handling. There are some vehicles that make use of a modular design, enabling components to be changed easily by the operators.
The market is effectively split into three areas: scientific (including universities and research agencies), commercial offshore (oil and gas etc.) and military application (mine countermeasures, battle space preparation). The majority of these roles utilise a similar design and operate in a cruise (torpedo-type) mode. They collect data while following a pre planned route at speeds between 1 and 4 knots. Commercially available UUVs include various designs such as the small REMUS 100 AUV produced commercially by Hydroid, Inc.; the larger HUGIN 1000 and 3000 AUVs developed by Kongsberg Maritime and Norwegian Defence Research Establishment; the Bluefin Robotics 12-and-21-inch-diameter (300 and 530 mm) vehicles and the Explorer by International Submarine Engineering Ltd..
The market is evolving and designs are now following commercial requirements rather than being purely developmental. Upcoming designs include hover-capable UUVs for inspection and light-intervention (primarily for the offshore energy applications), and hybrid AUV/ROV designs that switch between roles as part of their mission profile. A Table below lists some of the popular Unmanned Underwater Vehicles.
Weight in Kgs
|Remus 100||Hydroid LLC||
|SUBROV (Sea Owl ROV)||Saab Underwater Systems||
|Remus 600||Hydroid LLC||
|Bluefin||Bluefin Robotics Corporation||
|Remus 6000||Hydroid LLC||
|Hugin 1000||Kongsberg Maritime AS||
|Hugin 3000||Kongsberg Maritime AS||
One weapon which is being tried out for fitment and utilisation from UUSWCs is the common very light weight torpedo (CVLWT). The CVLWT is actually a derivative of the Anti-Torpedo Torpedo (ATT). The ATT is 6.75 inches in diameter, 105 inches long, weighs approximately 200 pounds and is powered by a stored chemical-energy propulsion system. It is designed to operate in the noisy, turbulent wakes of ships, where it could intercept wake-homing torpedoes. The CVLWT is likely to offer a reduction factor in weapon size and weight of two to three times compared to the present lightweight weapons, while still offering a very high lethality versus most existing submarines. Promising developments specific to UUSWCs include; light weight but lethal warhead, compact combat battery and a single crystal broad band transducer. The CVLWT could be carried by UUSWCs and fired from modified launchers in anti submarine warfare role.
Super cavitating ammunition that functions better in the underwater environment has been developed recently by Defence & Security Group (DSG), a Norwegian company. The Multi-Environment Ammunition (MEA) series super cavitating rifle ammunition is anticipated to be useful for certain special operations, including underwater warfare. These include applications such as neutralisation of enemy divers, MIO (Maritime Interception Operations), anti-submarine warfare, and anti-torpedo operations. The unique underwater capabilities of MEA series super cavitating ammunition allow it to be used for UUSWCs applications. Using the .50 BMG super cavitating cartridges, an UUSWC can potentially destroy steel-hulled underwater objects from a distance of 60 meters, or could potentially hit a target 1,000 meters in the air from a location 5 meters below the surface.
Indian Navy has floated a requirement for at least 10 autonomous underwater vehicles (AUVs) that can be developed and begin production within four years of award of contract. The Navy has chosen to exercise the “Make” procedure of India’s Defence Procurement Procedure a special category that can be invoked by the armed forces for “high technology complex systems designed, developed and produced indigenously”. The Navy wants AUVs that can carry “variable payloads like high definition sonars and underwater cameras for surveillance reconnaissance activities of the sea bed (such as MCM operations, Oceanographic survey and specialised mapping etc).”
Trends. Ultra-low-power, long-range variants such as underwater gliders are becoming capable of operating unattended for weeks or months in littoral and open ocean areas, periodically relaying data by satellite to shore, before returning to be picked up. Also a new class of UUVs are being deployed, which mimic designs found in nature. These bionic vehicles are able to achieve higher degrees of efficiency in propulsion and manoeuvrability by copying successful designs in nature. Two such vehicles are Evologics‘ Bionik Manta and Festo‘s AquaJelly. Further, new class of weapons specific to UUSWCs is already under advanced development and is likely to be available in a couple of years. These include much smaller and lighter missiles, torpedoes and gun systems.
The UUSWCs are the future of underwater warfare.