Traditional navies as well as maritime terrorists can and have used mines and underwater improvised explosive devices (UWIEDs) to challenge military and commercial uses of the seas. With 95% of the world’s commerce moving by sea, the security of waters, coastlines and military personnel remains a key issue for navies. Sea mines and underwater explosives have become cheap to acquire and easy to deploy now pose a real threat to navies and commercial shipping by reducing freedom of movement in shallow waters and strategic choke points.
More than thirty countries produce mines, and twenty countries export them. Iran has reportedly laid several thousand naval mines, North Korea’s 50,000, China 100,000 or so, and Russia estimated quarter-million. Since World War II, sea mines have damaged or sunk four times more U.S. Navy ships than all other means of attack combined, according to a Navy report on mine warfare.
Sea mines range from cheap, simple explosive devices which many fear may fall in the hands of terrorists, to sophisticated computerized systems equipped with sensors and designed to wait hidden on the sea bed for years until the right target presents itself. They are fitted with acoustic, magnetic, seismic, and pressure sensors, which can pinpoint the size and shape of a ship moving in water and detect ship’s approach. They have become stealthier by minimizing their sonar profiles, smarter in distinguishing targets from decoys and evolved into lethal systems that can fire torpedoes. There are also rumors of nuclear armed mines in the inventories of China and North Korea. They have potential to become surprise weapon in any future war. Indeed, sea mines are key to regional navies’ anti-access/area-denial (A2/AD) and sea-control strategies and operations.
Mine warfare is important component of US Navy’s one of the nine S&T focus areas of “Assure Access to Maritime Battle space”. Proliferation of anti-access, area denial capacity and capabilities among potential adversaries drives the need for technologies that assure access for naval forces, says US Navy.The capability to detect, locate, classify and neutralise these weapons remains a key requirement for navies around the world.
Mine Countermeasures (MCM) include both minesweeping and mine-hunting. Influence minesweeping uses acoustic, magnetic, and pressure signals to detonate emplaced mines. Mechanical sweeping uses a towed sled or other type of device to cut the cables of moored mines. These mines then float to the surface and are detonated by other means.
Mine hunting is the safest and most effective method of dealing with mines, particularly with modern influence mines. Mine countermeasures vessels equipped with variable-depth sonars, hull-mounted sonars and minesweeping systems are primary systems to detect and remove mines. Upon identifying the target using sonar, the mine-hunter vessel neutralizes the explosive with the help of deep-sea divers or remotely operated vehicles (ROVs).
With improvements in autonomy, endurance, underwater navigation, data communication, detection and identification sensors, Autonomous Underwater vehicles are increasingly being used for mine countermeasures.
Oceanic conditions greatly influence offensive mining and MCM operations. Variations in environmental parameters, such as bathymetry, salinity, temperature, tidal range, currents, water clarity, and seafloor character, can alter and significantly degrade sensor performance and reduce operational capabilities
Mine Countermeasure Platforms and systems
The Navy’s “triad” of “dedicated” mine countermeasures forces comprises surface mine countermeasure ships, airborne mine countermeasures helicopters, and Explosive Ordnance Disposal (EOD) divers and their systems. Once a threat region has been identified and bounded, a sonar or laser detection sweep for candidate mines is conducted from an Avenger class ship (MCM-1), a LCS, or MCM helicopters (including the MH-60S or MH-53E).
The systems currently employed for detection and classifications are:
• SQQ-32 variable-depth mine detection and classification sonar (MCM-1)
• AQS-24 multi-beam side-looking mine-hunting sonar (MH-53)
• Remote Multi-Mission Vehicle (LCS)
• AQS-20A Mine Hunting Sonar (MH-60S and with Remote Multi-Mission Vehicle from LCS)
• AES-1 Airborne Laser Mine Detection System (MH-60S)
Another platform under consideration for detection and classification is the common unmanned surface vehicle (CUSV).
Once a field has been mapped and objects classified, the target data is used by neutralization assets to reacquire (locate), verify (identify), and if required, neutralize the target. The systems currently employed (or planned for future use) for reacquisition and neutralization are:
• SLQ-48(V) Mine Neutralization System (MCM-1)
• SLQ-60 SeaFox (LCS)
• AN/AQS-235 Airborne Mine Neutralization System (MH-60S or CUSV)
• Barracuda Mine Neutralization System (MH-60S or CUSV)
• EOD Divers with Navy Marine Mammals
US Navy is attempting to achieve a number of objectives concurrently, writes Maj. Gen. Christopher Owens Director, Expeditionary Warfare (OPNAV N95): “Our primary air and surface platforms must be replaced with multi-mission platforms-in particular, littoral combat ships and the MH-60. Our primary hunting, sweep and neutralization systems must be replaced with new technologies that will do the time consuming, dangerous, and dirty work. We must continue to increase our clearance and confidence levels across our portfolio of mine countermeasures programs.”
Two airborne systems, the Airborne Laser Mine Detection System, and the Airborne Mine Neutralization System, achieved IOC at the end of November, Owens said. Both will operate aboard the Navy’s MH-60S chopper to locate and take out sea mines from the air by means of powerful armor-piercing warheads.
ALMDS (Airborne Laser Mine Detection System) uses LIDAR for Surface Mines
The US Navy has attained initial operating capability (IOC) for its AN/AES-1 Airborne Laser Mine Detection System (ALMDS). Designed and built by Northrop Grumman,The ALMDS will be integrated into the MH-60S helicopter to provide rapid wide-area reconnaissance and assessment of mine threats in littoral zones, confined straits, choke points, and amphibious objective areas. The ALMDS will be embarked as part of the mine countermeasures (MCM) mission package on the Littoral Combat Ship (LCS).
ALMDS uses Light Detection and Ranging (LIDAR) technologies to detect, classify and localize naval mines near-surface moored sea mines. The untethered sensor is capable of day or night operations and can attain high area search rates with accurate localization to support follow-on mine neutralization. The ALMDS uses the forward motion of the aircraft to generate image data, which simplifies the scanning process and helps ensure high system reliability.
The ALMDS uses pulsed laser light and streak tube receivers housed in an external equipment pod on the MH-60 helicopter. These lasers are designed to search the water column from the surface to about 40 feet in depth — the area where mines are the biggest threats and coincidentally where mine-hunting sonar systems are least effective. The system takes an image of the entire near-surface water column potentially containing mines.
The ALMDS projects a pulsed wide 538-nanometer blue-green laser beam into the water and samples at rates greater than 100 per second. This wavelength of blue-green laser “can penetrate water much better than other wavelengths. It goes a long way down,” says John Horton, head of the mine warfare systems department at the U.S. Naval Surface Warfare Center in Panama City, Fla.
AN/ASQ-235 Airborne Mine Neutralization System (AMNS)
AMNS consists of a helicopter-deployed launch and handling (LHS) system equipped with four unmanned Archerfish™ neutralizer vehicles which destroy mines via remote control from the operator in the MH-60S helicopter.
Each of the four Destructors can be launched one at a time without recovering the LHS. The Destructor contains a sonar, video camera, and light to accomplish target reacquisition, identification, and prosecution. The Destructor communicates with the common console via a fiber-optic data link and provides sonar and video data to the common console for display and use by the sensor operator.
The LHS consists of all hardware and software necessary for data processing during an AMNS mission. The LHS manages the neutralizers during helicopter transit and launch phases, and provides a communications interface between the neutralizers and the common console. The LHS interfaces with the Carriage Stream Tow and Recovery System (CSTRS) and can carry up to four Destructors on any one mission.
The Destructor is negatively buoyant, has six degrees of motion, can maintain a hover position, and can be operated in either automatic or manual mode. Additionally, the Destructor can monitor depth and relative distance from the bottom and has the ability to avoid bottom plowing. The Destructor’s position is determined by an Integrated Track Point II acoustic tracking system contained in the LHS.
BAE Systems to deliver Archerfish mine neutralisers to US Navy
The US Department of Defense (DoD) has contracted BAE Systems to manufacture and deliver Archerfish mine neutralisers and to continue supporting its minesweeping operation. BAE will manufacture Archerfish, which is a remotely-controlled underwater vehicle equipped with an explosive warhead, at its Broad Oak facility in Portsmouth, UK, and will also supply fibre-optic spools.
Deployed from a launch ‘cradle’ with a fibre-optic data link providing exacting command of the weapon, the equipment can be launched and operated from surface ships, helicopters and unmanned underwater vehicles (UUVs).
Archerfish leverages on the high frequency sonar and low light video data to track mine threats and fires the shaped charge warhead, initiating a full order detonation of the target.
The fibre-optic spools will link the Archerfish mine neutraliser and the launch platform, which is an MH-60S helicopter deployed from the US Navy’s littoral combat ships.
The advanced technologies of these systems deliver a comprehensive, end-to-end solution – detection to neutralization – enabling the Navy to safely and effectively execute its mission with reduced risk to its ships and crews
Remotely Controlled and Autonomous underwater vehicles (AUVs)
Unmanned systems (in the air, on the surface and below the surface of the water) have the potential to clear larger areas and to keep personnel and vessels out of the danger zone.
Using unmanned systems, Owens said, will lead to a significantly more effective minehunting operation. “It’s a force protection aspect, certainly,” he said. “But probably as important, or more so, from our mission standpoint, is that the unmanned systems don’t have crew decks. They don’t get fatigued after eight hours in the direct sun working a minehunting problem. We can do this reliably 24 hours a day, not affected by darkness, not affected by the heat … it gives us the ability to over time really expand our clearance rates.”
Autonomous underwater vehicles (AUVs) have gained increasingly importance in the area of reconnaissance and mine countermeasures (MCM). It is expected that AUVs will be integral part of seagoing vessels.
A major disadvantage of a typical MCM AUV operation is the time delay between survey and evaluation of collected side scan sonar data which typically doubles the overall mission duration. In order to exploit the full potential of MCM AUV missions, on-board data processing and the capability of online automatic detection and classification (ADAC) of mine-like objects is necessary.
Unmanned Aerial Vehicle (UAV) based Coastal Battlefield Reconnaissance and Analysis (COBRA) system
The Coastal Battlefield Reconnaissance and Analysis (COBRA) system, a minehunting payload designed to operate aboard the MQ-8 Fire Scout unmanned aerial vehicle, is set to achieve initial operational capability by the end of September 2017, said Marine Maj. Gen. Christopher Owens, director of the Navy’s Expeditionary Warfare Division.
Last Year US Navy issued SBIR to develop a “Night Time” capability for Coastal Battlefield Reconnaissance and Analysis (COBRA) that will provide the necessary light source for the COBRA camera. The current COBRA sensor is only capable of daytime operation.The objective is to create a small form factor, light weight, low power, and medium repetition rate broadband illuminator that is robust enough to be integrated onto the Fire Scout MQ-8B. The innovation of the COBRA Multi-Spectral Illuminator will be to provide the broadband light that will provide sufficient illumination power for the COBRA camera to image mine lines and minefields at night.
Three illumination technologies– Red Green Blue/Infrared (RGB/IR) lasers, RGB/IR light emitting diodes, and small/lightweight strobe lighting, have been previously explored for potential multi-spectral illumination. However, none of these technologies are mature enough to meet the technical requirements for COBRA camera illumination without further technical development and innovation. However, any of these three technologies, as well as other approaches, could serve as the basis for meeting the objectives of this topic.
European Unmanned Maritime Systems projects
The European Defence Agency (EDA) is continuing to promote maritime affairs and to develop, with Member States, the next generation of mine counter measure solutions via the successful delivery of Unmanned Maritime Systems projects.
Textron Systems Corp. is continuing its support for a fast unmanned boat designed to provide the U.S. Navy’s Littoral Combat Ship (LCS) with unmanned minesweeping capability to detect, pinpoint, and destroy ocean mines
The UISS, which uses the Textron Common Unmanned Surface Vessel (CUSV), will target acoustic, magnetic, and magnetic and acoustic combination mine types, and provide the LCS with a rapid, wide-area coverage mine-clearance capability to neutralize magnetic and acoustic influence mines.
US Navy’s fourth increment will deliver the Knifefish UUV, a development lead by General Dynamics Mission Systems based on the Bluefin-21 UUV equipped with a side-scan sonar that will provide a buried mine-detection capability up to a speed of three knots (5.5 kilometres-per-hour) to a depth of 275 metres/m (902 feet/ft).
French and British Governments to Jointly Develop Autonomous Underwater Mine-Hunting Robots
Meanwhile, mine-hunting methods have grown increasingly sophisticated as well, but it costs 10 times as much and it’s 10 time slower to remove a mine as to lay it. In an effort to make mine-hunting operations faster, cheaper, and safer, France and Britain are looking into robotic systems that have a high degree of autonomy.
French Defence Procurement Agency (DGA) has teamed up with UK’s Defence Equipment and Support organization, to create high-tech robotic systems capable of locating and neutralizing naval mines and other Underwater Improvised Explosive Devices (or UWIEDs) with greater ease and accuracy.
When deployed, Thales sees the mine hunters of tomorrow as a fleet of underwater robots, unmanned surface vessels, towed sonars, and remote operated vehicles connected by Iridium satellite links as well as radio, acoustic, and direct cable links that allow the command ship, robots, local operations centers, and Reach Back data centers to remain in close communications.
A set of geolocated Autonomous Underwater Vehicles (AUVs) will be used to locate the target, with the help of synthetic aperture sonar. The system would also use Towed Synthetic Aperture Sonar (T-SAS) with very high-resolution multiview imaging, while Unmanned Surface Vehicles (USV) with autonomous navigation and threat-avoidance sonar worked in conjunction with Remotely Operated Vehicles (ROV) capable of identifying and neutralizing mines by means of new analysis tools.
Deep driving drone submarine
Worst of all are mines buried under the bottom of the sea. There is no sonar in current service that can find them, said Navy Captain Aaron Peters, an explosives ordnance disposal (EOD) specialist.
“The only things that can detect buried mines right now are your marine mammals,” he said, primarily trained dolphins. But the Navy is working on a new system called Knifefish, with a special low-frequency sonar that can penetrate ordinary soil and detect small, dense objects such as explosives. It won’t be ready until 2017.
End-to-End Mine Countermeasure Capability
Raytheon provides both a modern minehunting and mine neutralization capability to the U.S. Navy, which are two of the components in the mine countermeasure mission package for the Littoral Combat Ship class. Supporting mine-clearing operations in both deep-ocean and littoral waters, AN/AQS-20A minehunting sonar detects, localizes bottom, close-tethered and volume mines, and identifies bottom mines.
European Maritime Mine Counter Measures project (MMCM) delivers modular toolbox
Belgium, Estonia, Germany, the Netherlands, Sweden as well as Norway agreed on 8 October 2014 to launch a new research project regarding future Maritime Mine Counter Measures (MMCM) capabilities.
Compared to existing solutions, future MMCM capabilities are expected to bring increased flexibility through a modular “toolbox” comprising a range of systems adaptable to different platforms, environmental, or operational conditions. The use of unmanned vehicles will also be developed and new detection techniques could be introduced. Future MMCM operations are also expected to be conducted with state-of-the-art sensors and effectors carried and deployed from dedicated or hybrid platforms as well as from stationary or mobile shore installations.
Challenges for Lockheed Martin Remote Multi-Mission Vehicle (RMMVs)
Remote Multi-Mission Vehicle also called a “semi-submersible” swims along with its upper surface just above the water. Being mostly submerged helps stabilize the small craft in choppy seas, enabling its sonar a much better picture. Being partly exposed to air allows it to burn diesel fuel, which gives it much longer endurance than batteries.
The Lockheed Martin-built system has three key problems to overcome:
Unreliable. The RMS was supposed to run for 75 hours between operational mission failures, but scored a dismal 19 hours in tests this summer. The Remote Multi-Mission Vehicle, the system’s centerpiece, fared slightly better with 25 hours between operational failures.
Losing contact. The RMMV is an unmanned, autonomous, semi-submersible system. It was to be a key component of the littoral combat ship’s mine countermeasures mission package, but has been unable to interface with LCS systems, according to a 2014 Pentagon report. The RMMV is billed as capable of line-of-sight and over-the-horizon operations, but control from the ship has not proven reliable, and communication is typically lost when the vehicle is out of sight
Missing mines: The self-propelled RMMV tows the AN/AQS-20A minehunting sonar that is supposed to detect and classify mine-like contacts, but a 2013 Government Accountability Office report noted that the towed sonar failed to detect certain mines, was slow in identifying others, and falsely identified some objects as mines
Mine countermeasure technologies
US and Germany partner to develop advance underwater mine hunting technologies
US Naval Surface Warfare Center Panama City Division (NSWC PCD) has partnered with Bundeswehr Technical Center for Ships and Naval Weapons, Maritime Technology and Research in Northern Germany on the Allied Munitions Detection Underwater (ALMOND) project.
The collaboration will aim to advance technologies and techniques for the detection, classification, and mapping of bottom and buried munitions. It will also benefit the warfighters by providing them with an increased ability to detect submerged and silent sea mines in complex environments.
NSWC PCD physicist Dr Jesse Angle said: “There is a significant worldwide capability shortfall in reliable techniques for mapping underwater munitions for unexploded ordnance remediation and hunting buried and stealthy sea mines in complex environments.
“We are seeking to bring together the best of our unexploded ordnance (UXO) detection capabilities and merge them with those of the Germans, so that both countries can learn and benefit from developments ongoing in the other country.”
Raytheon and US Navy partner to improve AN / AQS-20A mine hunting sonar
Raytheon and the US Naval Undersea Warfare Center (NUWC) – Division Newport have successfully upgraded the US Navy’s AN/AQS-20A mine-hunting sonar to better identify and classify mines. The team evaluated the equipment’s synthetic aperture sonar to optimise its ability to capture high and low-resolution images of potential mine threats undersea. During testing, the equipment demonstrated better performance and reliability, and generated better quality imaging of objects undersea, thereby improving the system’s mine detection capability.
The AN/AQS-20A system is towed undersea to simultaneously scan the water column for anti-shipping mines forward of, to the sides, and beneath the vehicle. Sophisticated sonar, electro-optical sensors, and high-precision location information are used to provide high-resolution images of mines and mine-like objects. It offers higher-quality imaging of objects found deep undersea to aid in the identification and classification of mines. The system supports the US Navy’s critical minehunting missions that make sure safe access and passage for military and civilian vessels on the world’s oceans and waterways.It can be deployed for mine-clearing missions in both deep-ocean and littoral waters, where the AN/AQS-20A identifies bottom, close-tethered and volume mines.
Synthetic aperture sonar (SAS)
Earlier sonars were of Real Aperture Sonar (RAS) type that transmitted pings, receives echoes, and generate corresponding strip of pixels on a computer screen. The sonar then repeats this pattern until it has an image of the sea floor. This technology is readily available and relatively inexpensive, but its resolution over long ranges is insufficient to suit the Navy’s mine-hunting needs.
SAS is a form of side scanning sonar, which sends pings to the port and starboard sides of the AUV and records the echoes. Synthetic aperture sonar (SAS) uses advanced computing and signal processing to create fine-resolution images of the sea floor based on reflected sound waves. The principle is to combine successive pings coherently along a known track in order to increase the azimuth (along-track) resolution. The commonly accepted measure for fine resolution is a 1-inch by 1-inch pixel size, which can be achieved by SAS.
Whereas RAS sensors emit relatively high acoustic frequencies that are quickly absorbed by the seawater. SAS uses lower-frequency acoustics that can travel farther underwater, thus increasing the range at which fine-resolution pictures can be produced. SAS can provide same resolution at 300 m what RAS produces at 30 to 50m. SAS in AUVs have produced fine-resolution images of sunken ships, aircraft, and pipelines.
Identify and Exploit Attributes of a Light Detection and Ranging (LIDAR) Signal to Improve Sea Mine Detection and Identification with a Low False Alarm Rate
The U.S. Navy’s ALMDS (Airborne Laser Mine Detection System), uses Light Detection and Ranging (LIDAR) technologies to detect, classify and localize naval mines near-surface moored sea mines. US Navy is seeking novel and innovative techniques to exploit the laser signal for fusion with image processing techniques to: better detect, recognize, and identify mine-like targets; reduce the false alarm rate; and to quantify results
Shallow Water Communications for Mine Warfare
US Navy has issues SBIR for development of an innovative secure communication capability for Navy mine warfare systems to enable two-way remote command and control of a minefield deployed across the hostile littoral environments. Reduction of power consumption of at least 15% and/or increased range of at least 25%, when compared to existing commercial-off-the-shelf (COTS) acoustic modems is desirable. Effective command and control of mine warfare systems requires two-way communication with reliable data transmission and reception over a range of 1000+ meters.
The objective of this topic is to develop an innovative, secure wireless communications technology for use on mine warfare systems to enable command and control in the hostile littoral environments. This technology will enable warfighters too remotely “turn on,” “turn off,” and/or reprogram the targeting logic of the minefield to respond to mission needs. Additionally, this could be used to remotely terminate a minefield after hostilities have ceased, saving significant cost and labor typically required to clear minefields.
Automatic Target Recognition
The current state of the art in mine detection has people scanning through large sonar images looking for the mines. However, when looking at an image of the sea floor from above, operators sometimes have difficulty discerning the identity of simple objects. On the surface the mines are easily confused with floating garbage in the sea. The bottom mines. Many objects look similar to mines, e.g., ripples in the sand. And it is even harder in some ways since the images are blurry and there is noise.
Automatic Target Recognition (ATR) software identifies potential threats directly from the data gathered by the AUV’s sonar, enabling decisions in-missions in real time. The ATR software allows the AUV to autonomously inspect possible mine targets, allowing both for real-time mine detections or simplified and consistent post-processing. Various ATR algorithms are now readily available to the MCM community. Many solutions have been proposed in technical literature.
A common solution is for ATR software to be tuned to recognize specific mine-like shapes. These contacts are then flagged and presented to the operator for review. Other ATR solutions model the characteristics of a mine and look for matches in the data.
Sonar performance is dependent on underwater currents; differences in pressure, temperature, and salt content (salinity); even how sound waves reflect off the bottom — which can change on hourly basis.
Regardless of the choice of algorithm, a common problem when using ATR software is the level of false-positive alerts. ATR in challenging in cluttered environments or in different seabeds from those used to tune the algorithms is likely to increase the level of false alarms. Future algorithms should understand the environment, then predict the expected performance of the ATR in different scenarios to provide information on the ‘huntability’ of the different regions within the survey area. This provides context to the detections, allowing the operator to make more informed decisions.
Shadows cast by mines are often easy to distinguish from ones cast by clutter objects, such as tires. New shadow contrast prediction technology can lead to improved imagery, power conservation, and better performance for automatic target recognition software.
The mine and mine-countermeasure technologies are a race akin to stealth-counter stealth race, not expected to subside very soon. With increasingly aggressive Russia and China amassing hundreds of thousands of increasingly sophisticated naval mines, a revolution in minesweeping and continuing research in the mine countermeasures is what is needed.
Mines are classified according to three characteristics. The first characteristic is its position in the water column. Bottom mines, which can also include buried mines, are generally found in shallow water, where either surface craft or submarines can easily trigger them. Moored mines (also called tethered mines) are usually used in deeper water and can be positioned at any depth in the water column. Moored mines are highly effective against both ships and submarines. Drifting mines move with the prevailing current direction and are designed to float at or just below the sea surface. Surface mines are either moored (via a chain to the bottom) or floating (a favorite terrorist tactic), and many float just below the surface.
The second characteristic is its method of delivery (although most mines can be altered for a different mode of delivery). Aircraft-laid mines are generally used for offensive actions where mines need to be rapidly deployed. These mines are dropped like bombs from an aircraft. Surface laid mines can be deployed from a variety of ships, enabling them to be laid secretively. Submarine-laid mines are designed to be fired out of torpedo tubes and thus, these types of mines are often torpedo shaped.
The third characteristic is its method of activation. Influence activation is the most common method. Detectors are used to sense changes in fluid pressure or acoustic, magnetic, and electric fields (or a combination of all four). Sensors can be designed to distinguish between different types of vessels or to have delays before detonating to ensure maximum damage to the triggering vessel. Contact mines are the oldest technology for mine activation and, in the simplest version, are designed to detonate when “horn” on the mine is bent. Controlled mines are triggered remotely, using cables connected to shore, although new designs can be remotely controlled, which will effectively allow a minefield to be turned on and off when needed to allow ships to pass through the mined area. This type of mine is typically used defensively and is particularly effective in preventing entrance to straits or confined areas