In view of recent tremendous efforts made by some leading naval scientists and engineers who are working tirelessly to develop a series of credible unmanned underwater vehicle (UUV) technologies, the militaries are looking for new ways to engage the enemy in a 21st century battlefield scenario by using artificial intelligence.
All over the world the new trend is to deal with a threat from unmanned platform so that the casualties are less or zero but the gain is maximum and timely, which can make the forces further battle ready with a full gravity of domain awareness.
Recent advances in UUV technology and their imminent inclusion in naval operations may mean that one will witness lot of new technological innovations and also these counter-measures much sooner than originally thought.
Artificial intelligence is going to be the key as the naval forces have been active over several decades in developing unmanned underwater vehicles (UUVs) since adjuncts to conventional manned platforms in many of the submarine missions that arise in expeditionary warfare.
Although initial emphasis is on minefield reconnaissance, intelligence collection, trailing, tagging, deception, and attack capabilities are potential future options, with command modalities that range from simple remote control to near-total autonomy.
And not surprisingly, UUVs have emerged as a key element in future concepts of operations for the submarine community, beginning with the Long Term Mine Reconnaissance System (LMRS) and its successor, the Mission Reconfigurable UUV (MRUUV).
Strictly speaking, every self-propelled torpedo is also a UUV, unmanned underwater vehicles can trace their history back for more than a hundred years.
More recently, mobile underwater targets, such as the Mk 39 Expendable Mobile ASW Training Target (EMATT) have demonstrated rudimentary UUV capabilities little different in their essentials from those of advanced UUV systems today.
However, it is only in the last thirty years that progress in propulsion, control, hydrodynamics, and sensor technology have enabled the development of more broadly capable vehicles and freed the imagination of naval planners to propose new and innovative operational applications for them.
The growing military potential of these platforms-particularly autonomous UUVs-stimulated the publication of US Navy UUV plan two years ago, and that document remains an authoritative and useful roadmap for supporting a wide range of naval missions, such as:
• Maritime Reconnaissance
• Undersea Search and Survey
• Communications/Navigation Aids o Submarine Track & Trail
Most of these roles are motivated by the unique advantages of underwater stealth and the need to manage risk, but there are many missions in which using UUVs to complement crewed platforms provides either a significant force-multiplier or simply a more cost-effective way of getting things done.
Despite the fact that UUVs are only now nearing operational use by the US Navy, significant research and development programs on UUV concepts stretch back well over two decades.
For example, the Defense Advanced Research Projects Agency (DARPA) supported a vigorous effort in the late 1970s and early 1980s to determine the feasibility of very long-endurance autonomous vehicles capable of undertaking Cold War surveillance missions over oceanic distances.
Endurance capability
DARPA investigated a number of promising energy-storage and propulsion schemes, but only drag reduction seemed to offer the possibility of achieving long range and endurance, and a variety of low-drag approaches, including bulbous, non-cylindrical bodies, were tried without achieving a practical vehicle.
At that time, the principal barrier to fielding militarily-useful UUVs lay in storing enough energy for adequate range, but navigating accurately over long distances, communicating with host platforms, and implementing reliable autonomous control presented challenges of their own.
Although new high energy-density batteries such as lithium thionyl chloride cells are now available to satisfy many of today’s propulsion requirements, their considerable expense per mission-mile is a serious disadvantage.
Moreover, energy storage remains a significant factor in designing long-endurance UUVs for future military applications like tracking and trailing.
However, with the introduction of small, low-powered inertial navigation components, the Global Positioning System (GPS), suitable satellite communications, compact antennas, more capable underwater sensors, and powerful digital information processing, many other barriers to implementing quite ambitious UUV capabilities have fallen away.
As long as their concepts of operation permit sporadic excursions near the surface to expose communications and navigation antennas or to allow access to relay platforms, only speed, endurance, and the adequacy of onboard autonomous control and “decision-making” will limit what UUVs can do.
Among the evolving UUV systems that have been demonstrated to date are Woods HoleOceanographic Institution’s REMUS (Remote Environmental Monitoring Units), MIT’s Odyssey, Florida Atlantic University’s Ocean Explorer series, and the Naval Postgraduate School’s Phoenix.
Of these, the small REMUS vehicles-only 7.5 inches in diameter, five to seven feet long, and less than 75 pounds-inhabit the low-end of the UUV size spectrum, but over ten have been fielded, largely for oceanographic measurements.
Powered by lithium batteries, REMUS variants have successfully completed survey missions of nearly 50 miles in the open ocean at three knots, and they have also demonstrated a capability to home in on a docking cone for downloading data and recharging their batteries at sea.
Somewhat larger are the Phoenix, Ocean Explorer, and Odyssey vehicles-
on the order of a foot or two in diameter, seven to ten feet long, and 500 to 1,000 pounds.
All have demonstrated range capabilities of 40-60 nautical miles at three to four knots, depending on payload, the most common of which has been side-scan sonar.
These vehicles have also carried a number of other instruments for various applications, and contact with their controllers is normally established with some combination of acoustic and satellite communications.
Similarly, navigation systems using a combination of GPS and inertial references are commonly fitted, although several vehicles have used fixed acoustic transponders to triangulate their positions.
Not surprisingly, interest in using UUVs in private industry is growing simultaneously, and internationally, at least a half-dozen firms have begun to commercialize UUV technology developed in university and military laboratories.
Currently, several vehicles are available for sale on the world market, and some developers also offer UUV services to the oil, undersea mining, and submarine cable industries for detailed bottom mapping, surveying, and geological exploration.
In many applications, the UUV approach costs less than half that of a typical deep-towed system covering the same area-and, these vehicles can, and have, gone places that towed systems cannot, such as under the Arctic ice.
Typically, the AUVs offered for commercial services by companies such as Maridan of Denmark and Hugin of Norway have been relatively small-generally about 15 feet long and several thousand pounds-and they offer endurance on rechargeable batteries of perhaps 20 hours at three or four knots. A variety of sensors can be fitted.
Since most oceanographic investigations and typical bottom-mapping assignments pose relatively modest endurance and distance requirements, many academic UUV researchers and industry AUV service providers have adopted a ‘small is beautiful’ design philosophy to minimize cost, turn-around time, and operating expense.
In contrast, for military and naval missions, where long endurance and large, multi-purpose payloads are key goals, the trend for the future is toward larger and larger vehicles.
The DARPA UUV program described above, for example, ultimately developed and tested several experimental craft that were extremely large for their time-38 inches in diameter, 27 feet long, and approximately five tons displacement.
These vehicles were transitioned to the Naval Oceanographic Office in 1997 to investigate their applicability to unclassified oceanographic surveying, and a follow-on version, denoted “Seahorse,” was developed subsequently by NAVOCEANO in collaboration with the Pennsylvania State University.
One notable UUV program is DARPA’s Deep Sea Operations Programme (DSOP), which is part of its Distributed Agile Submarine Hunting program.
Robotic technology
In April 2013, underwater vehicle manufacturer Bluefin Robotics completed phase two of the DSOP program with successful deep-water testing of one of its vehicles. The testing included six days of operational testing with two 4,450m dives, totalling 11 hours.
“We’ve achieved the goals of the phases as we’ve been working our way through them,” said Bluefin Robotics CEO and Chairman David P Kelly.
“The relative speed in which we’ve been able to integrate some of the capabilities and prove them out has gone very well. Probably better than expected.”
“The next phase is looking at testing the vehicle integrated with the sensor and the autonomy. We are in phase three of the contract and that phase is focused on the full integration of the sonar into the vehicle, as well as the production of a second system to demonstrate networked operations,” Kelly added.
Bluefin Robotics and other manufacturers are working on systems that can operate at depths unthinkable for manned platforms.
This capability is essential for detecting submarines overhead, which is one of DARPA’s main design criteria and one which Bluefin has worked closely on.
“The core pieces [for DSOP] were the depth, diving down to a 6,000 metre system, and then extremely tight buoyancy control at depth and also a power management technique to enable low power consumption to increase the endurance of the vehicle,” explains Kelly.
Bluefin are also working alongside General Dynamics Advanced Information Systems on the US Navy’s Knifefish UUV project. The Knifefish is a derivative of Bluefin’s successful Bluefin-21 vehicle and is due to enter operational service in 2017.
Significantly, it will be replacing the mine-detecting dolphins and sea lions that have made up the Marine Mammal Program for the last 50 years.
Despite the innovations that companies such as Bluefin Robotics have been able to achieve, endurance remains a challenge. “It’s not to the degree we’d like,” admits Kelly. “The US Navy would like missions approaching a week to enable the platform to work independent of the host platform. Those things are a little beyond what is capable today.”
But Kelly sees a time in the near future where platforms are robust and reliable and perform multimonth missions. In ten years, Kelly predicts the transition from a proof of concepts system to operational capability and asset will be fully complete.
Recently, DARPA consulted with industry over proposals for a new UUV project called Hydra. According to DARPA’s solicitation the vehicle would provide a novel delivery mechanism for insertion of unmanned air and underwater vehicles into operational environments.
This ‘mothership’ program will mean a greater reliance on autonomous systems to carry out advanced new missions.
Research into cooperation between AUVs is already underway across the Atlantic at Nato’s Centre for Maritime Research and Experimentation (CMRE).
CMRE, which is based in Italy, has been working with its European partners to create a system of UUVs that communicate through acoustic modems in an underwater wireless network. The result is a system composed of multiple, heterogeneous marine vehicles which cooperate to perform a mission.
One of CMRE’s main goals is working on standardising communications to create a common set of protocols when working with NATO members’ UUVs.
The hope is to have underwater connection that is up to the standard of WIFI, says CMRE’s deputy chief scientist Dr James H Miller.
“It’s a very big deal for Nato because we all speak different languages and every nation has different vehicles that speak different underwater communication languages.”
Sea trials of the Marine Robotic System of Self-Organising, logically Linked Physical Nodes (MORPH) project were carried out recently.
A consortium of 32 scientists from five countries and another eight research organisations successfully demonstrated coordinated manoeuvres between autonomous vehicles (two underwater and two surface) in a diamond shaped formation.
Collaboration is significant in operations such as ASW because of the low speed of UUVs compared to manned submarines.
“We’re like policemen on a slow motorcycle trying to catch a fast car. So we have to have a number of vehicles down the road waiting to catch the submarine,” says Dr Miller.
Scientists are developing ways UAVs can detect a submarine, track it and then communicate that information to a sister vehicle, which can repeat the process over distance.
CMRE is working closely with NATO’s Allied Maritime Command (MARCOM) based in Northwood, England, and Allied Command Transformation to speed-up the UUV transition from concepts to operational capability.
The innovations witnessed in recent years in vehicle technology, autonomous software and underwater communications could well create an effective capability with less risk and cost associated with manned platforms. In particular, the cost of an unmanned vehicle will be significantly less than what is currently invested in manned platforms.
With developers close to an effective UUV capability for ASW and mine clearance operations, what comes next?
Navies are taking notice of UUV capabilities as they develop and once they are deemed effective, may soon develop counter-UUV technology. As CMRE’s Dr Miller predicts: “It is the classic offence and defence in military warfare history, you come up with a new offence and defence adapts quickly.”
Replacing submarines
The first UUV likely to be deployed operationally in the Submarine Force is the Long Term Mine Reconnaissance System (LMRS) now under development by Boeing Corporation for an Initial Operational Capability (IOC).
Roughly the size of a submarine heavyweight torpedo, LMRS will be 21 inches in diameter and is intended for torpedo-tube launch and recovery from attack submarines.
Its primary mission will be autonomous mine reconnaissance, and the vehicle will be equipped with both forward-looking search sonars and side-looking classification sonars for that purpose.
In operation, LMRS would be pre-programmed to search potentially hostile areas out to as much as 120 nautical miles ahead of the host submarine.
Powered by lithium thionyl chloride batteries, LMRS is expected to have a top speed of seven knots and a nominal endurance of 40 hours.
This should provide an area coverage rate of from 35 to 50 square nautical miles per day. The host submarine will be able to establish acoustic communications with the vehicle at short ranges, and a satellite link will be used to maintain sporadic contact for both command/control and data exchange at greater distances.
Pre-planned product improvements under development for the vehicle include precision underwater mapping capabilities and more cost-effective, rechargeable energy sources.
In this context, the Office of Naval Research is sponsoring the development of a slow-speed synthetic aperture sonar to improve the onboard classification capability of the UUV with higher spatial resolution, while simultaneously extending the swath width to complement the capabilities of the forward-looking sonar.
Also, a laser line-scan imaging device that will facilitate more accurate classification of objects and features detected on the bottom is in consideration.
Already in planning as a more capable follow-on to LMRS is the Mission Reconfigurable UUV (MRUUV). MRUUV will be fielded in two “flights.”
The first of these will again be a 21-inch diameter, torpedo-tube-launched vehicle, which will build heavily on the lessons learned from LMRS and incorporate a wide range of advanced, modular payloads that may include sensors for electro-magnetic and electro-optical ISR, tactical oceanography, and remote ASW tracking.
Northrop Grumman Oceanic Systems, for example, is developing a retractable “ISR mast” that could be raised above the sea surface to conduct optical or electronic surveillance.
This will include an already-tested “immersive video” camera with hemispheric coverage and the ability to focus on targets of interest, as well as a multi-band antenna system and corresponding signal processing for collecting both signals and electronic intelligence.
Similar collection modules can be added as well for recording acoustic intelligence or detecting biological or chemical warfare threats in both air and water.
Accelerating progress in the realm of electronic computation and control, data processing, information management-and the packaging of these functions into smaller and more energy-efficient components-has led directly to the growing list of impressive UUV capabilities described above.
The potential for further growth is apparent. Nonetheless, three major technical challenges remain: energy storage, in situ communications, and autonomous control.
Essentially all state-of-the-art UUVs today are battery-powered, and battery capacity remains the most fundamental limitation on range and endurance.
Despite continuing efficiency improvements and increases in the energy density of both conventional cells and more recent electrochemical alternatives, no quantum breakthrough has been found in energy storage that would permit relatively small UUVs to perform theater-scale missions or long-duration trailing tasks.
Since the power required to propel an underwater vehicle is roughly proportional to its surface area-and stored energy capacity to its volume-the mission duration (or range) achievable at given velocity can be shown to vary directly with vehicle dimension, characterized by length or diameter-i.e. twice the duration, twice the size.
This is a key factor in explaining the increasing physical scale of extended-range UUVs planned for the future.
The same hydrodynamic laws also predict that the required propulsive power varies with the cube of vehicle speed, which drives another cruel trade-off and explains why so many of today’s UUV missions are executed at less than five knots.
New concepts
For the many useful military and naval missions that do not require long endurance-limited-area surveys or reconnaissance over short distances; repetitive patrols in scenarios where periodic energy replenishment is tactically feasible; and in peacetime oceanographic characterization-small UUVs will remain attractive for their low-cost, efficiency, ease of handling, and quick turn-around.
Additionally, several futurists have suggested “staging” concepts in which large, forward-deployed UUVs would launch smaller, perhaps expendable, UUVs of their own, both as a force-multiplier and for access to hostile areas inaccessible to larger, even unmanned, platforms.
Communications remain a problem area, particularly to and from underwater vehicles at depth. Despite the availability of undersea acoustic communication techniques in which “channel-matching” and intensive digital signal processing are used to sort out multi-path interference in shallow water, effective data rates will likely be limited to no more than several tens of kilobits per second over distances of several tens of miles.
This is an impressive achievement, and it has already been put to use in some of the more limited scenarios described immediately above, particularly when covertness is not an issue.
Additionally, short-range acoustic communications have already been demonstrated for exchanging data and command information among nearby vehicles and docking stations, or when operating close to manned host platforms.
But because so much of the data that prospective long-range missions are intended to collect will be inherently high-bandwidth-imagery, electronic or communications intelligence, detailed bottom surveys-there seems no real alternative to recording the “take” on board for post-mission playback-or devising some means to relay it back to the user by satellite or other means.
One promising alternative is the so-called “COMNAVAID” approach, in which ocean areas of interest would be seeded with multiple surface buoys in contact with both GPS and communication satellites and used as relays for nearby UUVs.
Relatively short-range two-way acoustic data links would establish connectivity between vehicles and buoys for both data and command/control. This technique follows directly from the network-centric orientation now gaining ground in the US Navy.
Even in today’s relatively limited missions, reliable autonomous control remains a significant risk factor. Despite a growing capability for two-way communication with deployed UUVs, the vehicles must still be “smart” enough to decide how to react to unforeseen circumstances between communication sessions and either take appropriate action or recognize the need to contact home base for instructions.
A number of tools are available here-artificial intelligence, “fuzzy” logic-but as the range and sophistication of UUV missions increase, maintaining sufficient vehicle autonomy may become the most limiting factor in implementing any future vision.
After nearly three decades of development and experimentation-much of it supported by the Navy-unmanned underwater vehicles are close to joining the fleet in meaningful numbers and substantive roles.
Because their communication and command/control issues have been so much easier to resolve, unmanned aerial vehicles (UAVs) have been proving their value in combat for over ten years.
For UUVs-out of sight and often out of touch in the depths of the ocean, these problems remain formidable. But the winds are shifting; a sea-change is imminent.
With an active and enthusiastic development community, a powerful legacy of demonstrated technologies, increasing industry acceptance, current interest in Special Forces applications, and the approaching deployment of LMRS by the Submarine Force, UUV’s are rapidly gathering momentum and a critical mass of supporters.
The technologists have delivered, and there is no lack of imagination in proposing future concepts of operation.
