Unmanned Surface and Undersea Vehicles: Capabilities and Potential
The environment of the world today reflects increased uncertainty about origins of threats, possible locations of attacks, and means by which they might be delivered. The term “asymmetric threat” is now familiar in the lexicon, and terrorist actions are a frequent occurrence. For naval forces, the classical terms “blue water” threat and “major threat axis” no longer hold the significance they once did. The threat environment has moved from the “blue water” to “brown water,” or littoral regions, placing emphasis on power projection, force protection, and expeditionary operations in littoral areas.
Along with this change in emphasis, new capabilities will be required of naval forces in the areas of maritime intelligence, surveillance, and reconnaissance (ISR); oceanographic bathymetric surveys; battlespace preparation; battlespace awareness; mine warfare; antisubmarine warfare (ASW); special operations and strike support; surface warfare (including interdiction); littoral ASW with emphasis on diesel submarines; and base and port security. Particular areas of weakness that have been identified with respect to the needed capabilities include organic mine countermeasures, littoral ASW, and defense against small boats.
In turn, the kinds of missions listed above place a premium on integrated, persistent ISR; command, control, and communications (C3); and distributed, real-time knowledge. The increasing needs arising from the new threats may be alleviated, to a growing extent, by exploiting the benefits of unmanned systems, leveraged by networking sensors and communications to the greatest possible advantage, and using unmanned surface vehicles (USVs) and unmanned undersea vehicles (UUVs) as nodes in sensor and communications networks.
This chapter discusses the following topics: potential of USVs and UUVs for naval operations, the USVs and UUVs currently available or under development, naval operational needs and technology issues, and opportunities for improved operations. The committee’s conclusions and recommendations concerning USVs and UUVs are then presented.
THE POTENTIAL OF AUTONOMOUS UNDERSEA AND SURFACE VEHICLES FOR NAVAL OPERATIONS
Unmanned underwater vehicles already play a significant role in naval warfare—the most obvious example being the torpedo. In recent years, several developmental systems have reached levels of maturity at which they can be used in direct support of combat operations. The principal mission of these systems is reconnaissance—to provide environmental or countermine data.
Advantages of Current System Developments
Typically, USV and UUV systems provide significant standoff and clandestine capability. They can operate in fully or partly autonomous modes, but when operating autonomously they do not currently have adaptive or intelligent capabilities. They can carry out predetermined missions, providing optical or acoustic imagery and physical environmental data—such as information on temperature, salinity, depth, and currents, as well as optical properties. As the development of adaptive, and eventually intelligent autonomous, control capabilities become more mature, the potential for these systems to engage in cooperative autonomous behavior will grow, allowing groups of these vehicles to operate together as robust, fault-tolerant, and adaptive networks.
Both UUVs and USVs offer the potential for significant contributions to the conduct of naval warfare tasking, particularly when integrated with one another and with other manned and unmanned platforms, sensors, and communications nodes into a total FORCEnet system solution. The Department of Defense (DOD) and the Navy have recognized the utility of unmanned systems in recent operations, including Operation Enduring Freedom and Operation Iraqi Freedom, and in a number of fleet exercises as well. The Department of the Navy has an outstanding roadmap for the development of UUVs and is well along the path to their production and deployment. In addition, the Navy is currently evaluating the role of USVs, which at present do not have a history of operational experience comparable to that of UUVs.
Needs, Issues, and the Future Potential of Unmanned Surface Vehicle and Unmanned Undersea Vehicle Systems
The Navy’s UUV Master Plan1 identifies the utility of UUVs for maritime reconnaissance (passive electromagnetic/electro-optical (EM/EO) localization, and indications and warning), undersea search and survey, communication and navigational aids, and submarine track and trail. Plans and programs are under way to distribute the sensing and countermeasure assets, building on the early Mk 39 (Expendable Mobile Antisubmarine Warfare Training Target System) (which reached initial operating capability (IOC) in 1994), through the Remote Environmental Monitoring Unit System (REMUS) semiautonomous hydrographic reconnaissance vehicle (which reached IOC in 2002), the Near-term Mine Reconnaissance System (deployed on selected submarines from 1998 to 2003) that is now planned to transition to the Long-term Mine Reconnaissance System (IOC in 2005), the mission reconfigurable UUV (IOC in 2008), to the large displacement mission UUV (IOC in 2011), and, perhaps even larger conformal vehicles releasing swarms of small UUVs. Several key elements are the concept of “families” of vehicles, modularity of vehicle components, energy sources, sensors and payloads, and common architecture (including physical interface) standards. These approaches should facilitate integration into an end-to-end system solution.
To date, much of the UUV development has been platform-centric, with integration often limited to physical interfaces. Today’s systems are described by NAVSEA PMS 403 (Unmanned Undersea Vehicle Program Office in the Naval Sea Systems Command) to be the development of a number of “stovepiped” systems leading to the production of similarly stovepiped systems. Future developments need to embody the desired system functionality, standardized interfaces, and common architectures for communications and control, and provide for options to facilitate logistics for extended performance (such as energy pallets or docking stations on the seafloor), sensor fusion (cooperating with other systems), onboard processing, fusing data into information, and compressing the result for communication to other vehicles (manned or unmanned) or the fleet.
Undersea operations, including the difficulty of communications, demand “work-arounds” in the near term as well as further research into increasing underwater communications capabilities. One such step is increased autonomy, which in itself serves to reduce communications needs. Also, a premium is placed on the ability to navigate and to coordinate positions and time lines in order to fuse the data from sensors. One potential solution to the latter two issues may be to release
small, tethered modules to the sea surface either for radio transmission through the atmosphere or to obtain a Global Positioning System (GPS) navigational fix.
It is important to approach future systems developments and their integration with joint and theater assets (whether organic or not) with an overarching approach to systems engineering and systems management, reflecting integrated concepts of operations (CONOPS). One such example could be the development of a relatively large UUV, capable of sonar mapping for search and classification and capable of deploying a variety of unattended sensors, both tripwire and other varieties (for example, acoustic or magnetic to determine ship movements to and from port areas of interest). The example UUV would also be capable of certain revisit rates to download information from such sensors and provide restorative power, as needed, to the sensors (particularly if the sensors include a significant amount of onboard computational capability). By the same token, the UUV may be able to recharge its energy from an energy pallet or source previously placed on the seafloor by another large UUV, ship, or aircraft. To complete the picture, the UUV may be able to obtain data from companion USVs performing maritime reconnaissance tasks, deploy a small buoy or antenna to the surface to gain GPS and timing updates, provide onboard processing to fuse the results, and, finally, deploy another small buoy or antenna providing a burst transmission to either a satellite or unmanned aerial vehicle (UAV) communications relay, thereby allowing the Navy to enjoy a persistent, real-time alert-and-warning capability. If necessary, and if endowed with enough energy, the large UUV could initiate a track-and-trail operation, then accomplish a handoff to another companion UUV to track, trail, or tag the target.
Naval operations in the air, at the sea surface, and in the ocean need good information about the environment. For example, knowing the acoustic environment in the upper ocean enables the prediction of the performance of sonar sensors. Similarly, knowing the presence of bioluminescent organisms in a nearshore area could predict difficulty for a Special Operations Force or mine countermeasure activity. This kind of knowledge and understanding of the environment is an essential component of technological superiority.
It has been the hope that numerical modeling, particularly coupled to ocean atmosphere modeling with sparse in situ and remotely sensed data, would provide high-resolution, accurate environmental fields to guide tactics and strategy. While the development of these models and the techniques for data assimilation are still an active research area, so are the needs for accurate data in both the atmosphere and the ocean. These data cannot be provided by remotely sensed, overhead assets but require direct, in situ measurements. The difficulty of providing sufficiently accurate and well-resolved data in the ocean has been faced by the research community as well, aggravated by the rising cost of ship time. The answer has been autonomous vehicles.
Many of the small UUVs in use today were developed under support from the Office of Naval Research (ONR) in order to address these environmental sensing needs. These systems are sufficiently robust and well developed at this point to contemplate the larger question of whether they can be used cooperatively with numerical models to characterize an ocean environment. For example, the ONR-sponsored program (July 2003) on the Autonomous Ocean Sampling Network (AOSN) in Monterey Bay, California, uses a suite of autonomous vehicles as well as many other assets whose sampling patterns can be adapted and guided by a data-assimilating numerical model to improve the performance of the model’s representation of the environment and its predictions. This scenario can be readily extrapolated to include atmospheric boundary-layer observations using USVs and UAVs. One could further imagine this capability over the scales of a Carrier Strike Group or Expeditionary Strike Group providing accurate descriptions of the oceanic and atmospheric environments. The ability to bring multiple observational assets together adaptively so that observations can be used to resolve fronts and other evolving small-scale structures will dramatically improve models and representations of the environment.
Simultaneously with the development of various autonomous systems, the Navy has embarked on the development of the Littoral Combat Ship (LCS), which it is anticipated will play a major role in future combat operations. An integrated suite of both UUVs and USVs, as well as other types of autonomous vehicles, such as UAVs, are likely to be important elements within the LCS complement of combat assets. However, to date there appears to have been little or no consideration given to the logistical issues posed by the presence of such vehicles onboard the LCS. Planning for the launch and recovery as well as maintenance and handling space for these systems must become an integral part of the LCS development process.
OVERVIEW OF UNMANNED SURFACE AND UNDERSEA VEHICLES AVAILABLE OR IN DEVELOPMENT
This section provides an overview of the current status of the Navy’s programs for utilizing unmanned surface vehicles and unmanned undersea vehicles. Table 5.1 summarizes the characteristics of a number of these vehicles. While USVs and UUVs have much in common, they have many distinct issues as well. Surface vehicles can use radio frequency (RF) for virtually unlimited communications and navigation. In contrast, the communications and navigation environment for undersea vehicles is challenging at best. Significant improvements have been made in underwater acoustic communications in the past decade, and many of these improvements are reaching operational status. As discussed earlier, future developments in autonomous control should provide effective strategies for minimizing the communications reach-back burden of remotely controlled vehicles.
TABLE 5.1 Characteristics of Various Unmanned Surface Vehicles (USVs) and Unmanned Undersea Vehicles (UUVs)
Unmanned Surface Vehicles
Naval use of unmanned surface vehicles has a long history, beginning soon after World War II with deployments of remotely controlled target drones and mine sweepers. Recently, there has been enhanced interest in developing and using USVs for reconnaissance, surveillance, and mine-hunting missions in more nearly autonomous modes, as well as a continued use of the target drones.
To date, USVs have received neither the acceptance nor the attention in the Navy that has been given to other unmanned vehicles (unmanned ground vehicles (UGVs), unmanned aerial vehicles (UAVs), and UUVs). In particular, the Navy has no approved USV master plan. It appears that efforts regarding USV launch-and-recovery systems on surface platform hosts have limited emphasis. Among other things, hosts would prefer not to reduce speed or stop to either launch or recover USVs, because to do so might place the surface host platform at risk.
The number of USVs in existence or being developed is small compared with that of UGVs, UAVs, and UUVs. Three unmanned surface vehicles—the Spartan, Owl, and Roboski (detailed descriptions follow)—are mentioned frequently as candidates for naval use. The Remote Minehunting System (RMS), usually considered a UUV, is in fact a semisubmerged, air-breathing USV.
Most of the technology necessary for the development of USVs is mature and available. High-speed, low-observability, agile surface vehicles with acceptable endurance could be developed at reasonably low cost. However, various systems engineering aspects of these systems have not been adequately addressed, including how they will communicate with one another, with other unmanned vehicles, and with manned undersea, surface, and air systems; what sensor suites they might employ; and how they would best be launched and recovered.
Although current USV systems are used in a remotely controlled mode, opportunities for these systems, when used in an autonomous and adaptive control mode, are significant. For example, the increasingly hazardous mine-hunting process typically requires the acquisition of potential targets in order to identify, classify, and neutralize hazards. The cooperative action of multiple USVs with a broad range of sensing capabilities has the potential to improve mine-hunting capability significantly. Similarly, with multiple vehicles there is important potential for improvements in coverage rates for environmental and other survey missions if adaptive or intelligent autonomous control schemes become available.
USVs could also be effective in the areas of port and ship force protection. Current systems fulfilling these potentially hazardous roles are personnel-intensive. USVs appear to have promise for shallow water ASW and for countering swarms of small boats. USVs could also be assigned clandestine logistic roles to deliver and place seafloor sensors or seafloor energy sources for later use by UUVs, to shoot ground sensors ashore, to deploy seafloor or midwater acoustic arrays, or to place logistics packages in support of SEAL (sea, air, and land) teams or Special Operations Forces. Also, as discussed earlier, they could collect oceanographic data necessary to provide environmental information in support of warfighter systems and to detect the presence of chemical and biological agents.
Various naval USVs are described below:
The autonomous search and hydrographic (ASH) vehicle and the Roboski were developed in the 1990s, initially as jet-ski type target drones for ship self-defense training. They are now also used as reconnaissance vehicle testbeds. They operate as remotely controlled vehicles and therefore are confined to line-of-sight operation.
The Owl USV is a commercially available modification of ASH, with a low-profile hull for increased stealth and payload, operated as well in a remotely controlled mode. It has been used in demonstrations for marine reconnaissance in riverine and littoral situations. Today, several variants for stealthy USV sensor platforms have been proposed and are under consideration by the naval forces.
The Spartan USV is an Advanced Concept Technology Demonstration (ACTD) started in May 2002. It is a modular concept, adapted to a 7-m-long rigid hull inflatable boat (RHIB) and fitted with various sensor and mission modules. It will be demonstrated in mine warfare, force protection, and precision strike sce-
narios, as well as for command and control of multiple USVs. This prototype system will have an endurance of up to 8 hours, a range of 150 nautical miles, transit speeds greater than 28 knots, and payloads of up to 2,600 lb. A larger version is contemplated based on an 11 m RHIB, with correspondingly larger payload and endurance.
The Remote Minehunting System’s mission is to detect, classify, localize, and identify bottom and moored mine threats in shallow and deep water. It is an air-breathing, diesel-powered semisubmersible that autonomously follows a preplanned mission plan. The vehicle deploys a variable depth sensor (VDS), comprising acoustic and EO sensors to positively identify objects as mines or nonmines. The VDS is the AN/AQS-20 airborne mine reconnaissance sensor, containing a suite of five acoustic sensors and the EO mine warfare sensor. The data link sends information collected by the VDS back to the host ship via line-of-sight or over-the-horizon transmissions. The first installations are planned for Aegis destroyers DDG 91 through DDG 96. System mission command, control, and display are incorporated into the AN/SQQ-89(V)15 undersea warfare combat system and operated by the host ship.
The RMS concept of employment starts with a launch of the remote, mine-hunting vehicle with its towed sensor package from the destroyer (DDG). The vehicle transits to the reconnaissance area prior to the DDG’s entering the immediate area, and it conducts area reconnaissance by executing a preprogrammed mission profile. The processing onboard the RMS detects, classifies, and localizes minelike objects. Target imagery data and precise locations where data were gathered are radioed back to the DDG. The data are processed onboard the DDG to positively determine if the minelike object is indeed a mine. This process can be operator-initiated or automatic.
As mentioned above, this vehicle is large, almost 14,000 lb with the VDS, and is awkward to deploy or recover in any sea state above sea state 3. However, dedicated handling gear for deployment and recovery from the ship has been developed.
Unmanned Undersea Vehicles
Unmanned undersea vehicles are the most recent manifestations of a series of vehicles replacing divers to do work in the ocean. Manned undersea vehicles, usually called deep submergence vehicles (DSVs), were designed to go deeper than divers could. They were configured for ocean exploration, science, search, rescue, recovery, and survey.
To extend time on station at depth and remove risk to DSV occupants, remotely operated vehicles (ROVs) were introduced. A surface platform is required to launch, recover, and tend the ROV during operations. Control of the ROV from the surface is enabled through an umbilical link, which also supplies
power. Telepresence (i.e., the use of television cameras on the ROV) permits observations from the ROV to be sent to the human controllers on the surface. In many circumstances, the high costs associated with the surface platform are justified, particularly when fine control, manipulation, or specific complex tasks are involved requiring human oversight. In other situations in which the task is routine and can be programmed, untethered systems, unmanned undersea vehicles, without need for umbilical links, that are either partially or totally autonomous, are an attractive alternative. Elimination of the umbilical link also reduces drag. Thus, untethered UUVs were developed for various offshore industry, science, and naval purposes, replacing many of the functions of towsleds and similar survey vehicles.
The opportunity to provide multiple simultaneous views by operating several untethered UUVs or using UUVs with a surface platform will greatly enhance their capabilities. For example, untethered UUVs are beginning to replace towed vehicles for seafloor survey, and they are enabling new kinds of inspections that were previously impossible (such as in New York City water tunnels); they perform surveys from shore, and improve the utilization of ship resources by operating UUVs simultaneously with other UUVs or other types of operations. However, as noted earlier, the intrinsic limitation of bandwidth for communications in the ocean requires much more substantial autonomy for an untethered system in the ocean than for a system on the surface or in the air.
The technology required for useful naval UUVs is mature and available. Available technology enables reasonable endurance, low observability, multimission capability, and modularity. The highest near-term naval payoff that will accrue to UUVs is likely to be in mine warfare, ASW, oceanography, and environmental reconnaissance. UUVs could also play roles as communications relays in conjunction with nuclear-powered submarines (SSNs) and manned or unmanned surface or air platforms, and in operations similar to those mentioned previously in this chapter for USVs.
The Navy-approved UUV Master Plan2 provides a thorough and explicit roadmap for the continued development of UUVs, addressing their evolving capabilities, concept of operations, and technology and engineering issues. The UUV Master Plan cites numerous technical needs, including underwater communications, improved sensors, improved navigation, high energy density sources, and improved launch-and-recovery systems.
As noted earlier, there is an active, worldwide commercial interest in UUVs for the offshore oil, gas, and communications industries as well as active devel-
opments in the research community. These efforts need to be tracked and leveraged, where possible. The U.S. research community is supported in part by the Office of Naval Research, and the developments are well integrated into the Navy’s vision for UUVs. Various naval UUVs are described below.
Semiautonomous Hydrographic Reconnaissance Vehicle System
PMS 325J Expeditionary Warfare developed the semiautonomous hydrographic reconnaissance vehicle (SAHRV) system, which is a modification of a system, called Remote Environmental Monitoring Unit System (REMUS), developed for routine autonomous surveys in coastal regions for the research community. This SAHRV system is widely used in the research community. It is human-portable (80 lb) and is equipped with sensors to measure conductivity, temperature, water depth, and optical backscatter. It has a side-scan sonar as well as an up-down-looking acoustic Doppler current profiler. Its modular design facilitates the installation of additional sensors, such as for bioluminescence. Navigation is provided using a short-baseline acoustic system. Control is exercised through a laptop computer that implements simple waypoint commands.
Planned improvements in the SAHRV system include computer-aided detection and classification, digital acoustic communications, upward-looking detection sonar, forward-looking obstacle-avoidance sonar, and precision navigation. In addition, an adaptive control system is under development that will allow dynamic reprogramming of a mission by an operator via acoustic communications or by threshold detection of onboard sensors. An adaptive control system allows the vehicle to follow a plume to its source or to determine regions of maximum concentration of bioluminescent organisms or pollutants. In addition, the capability for the vehicle to dock at a remote docking station, download the accumulated data, and recharge its batteries has been demonstrated.
PMS Explosive Ordnance Detachment is developing vehicles based on the REMUS platform to counter the threat of unexploded ordnance and reduce the threat to the Navy’s teams. The detachment is also developing a vehicle to conduct mine reconnaissance in shallow waters (10 to 40 ft deep) close to hostile shores and is working to have an initial operating capability by mid-FY03 and full operational capability by FY05. Concurrent developmental efforts include vehicles to conduct harbor search and the clearance and reconnaissance of waters up to 300 ft deep and, leveraging the Joint Robotics Program, to develop ground crawlers to work in the surf zone. REMUS was used in Operation Iraqi Freedom by Special Forces, and it was used for explosive ordnance disposal in mine reconnaissance missions in the waterway and in the port of Umm Qasr.
Long-range Mine Reconnaissance System
The Long-range Mine Reconnaissance System (LMRS) is a UUV designed to be launched and recovered from a submerged submarine while it is under way at very low speed. The primary purpose of the LMRS is to extend the submarine’s capability to conduct mine reconnaissance in clandestine fashion. The system is planned for the Virginia-class SSNs and nuclear-powered guided-missile submarines (SSGNs). LMRS launch requires a dedicated torpedo tube, and the recovery system occupies an additional torpedo tube, representing a considerable loss of flexibility for other kinds of submarine operations. The LMRS is a follow-on to the Near-Term Mine Reconnaissance System (NMRS), which was built to meet the specific needs of the submarine community to have a semiautonomous vehicle to perform reconnaissance ahead of the submarine. The NMRS was built using technology available in tethered torpedoes and sensors used by the mine countermeasures communities. The NMRS is tethered to communicate information back and forth, but the system is recoverable, unlike torpedoes. Four NMRSs were built and were deployed on selected submarines from 1998 to 2003. By meeting the specific needs of the Navy, the NMRS program can be considered a success.
One LMRS vehicle and a dedicated submarine launch-and-recovery system are in prototype development, with a planned IOC in FY05. It is apparent that the project is currently well behind schedule and over budget, to the extent that it has triggered an Office of the Secretary of Defense (OSD)-level review of whether to continue as originally planned. It is likely that an IOC in FY05 is not possible.
The technical problems of the LMRS in the areas of power and of navigation and launch and recovery are as follows. Given the 21 in. diameter of the vehicle, prescribed by the standard torpedo tube, the LMRS vehicle requires a great deal of power to provide sufficient speed for stability, as well as sufficient endurance to provide realistic standoff and surveying capability. The Navy has chosen to use high energy density, lithium thionyl chloride batteries, which have required an extensive and long process to be qualified for use in the vehicle’s hull. While this may ultimately be a good solution for the energy, it has certainly created additional delays in the program. There are, in the committee’s view, several technical deficiencies in this system, exclusive of the sensor package. The vehicle used an inertial navigation system, which may not achieve the level of accuracy required for the countermine mission; for such a mission, the objects being sought are of a scale smaller than the anticipated navigation error. Additionally, the launch-and-recovery system is cumbersome, requiring the attachment of an arm to the returning vehicle and then the insertion of the vehicle into the torpedo tube. This is a delicate process at best, when demonstrated by the mock-up system built on a floating dock—it is going to be problematic in real-world environments, especially given the limited stability and maneuverability of the LMRS vehicle at slow speeds.
As said above, this system, however flawed, needs to be used so that the Navy can begin to learn how to use a UUV for its ISR and countermine missions, and from this real-world experience develop appropriate CONOPS. If the OSD review triggered by the delays and budget growth results in a cancellation of the LMRS program, no experience will have been gained.
At present, the LMRS sensor package is similar to the package described above for the RMS (AN/AQS-20)—essentially the same variable-depth sensor suite used for airborne mine reconnaissance. Forward- and side-looking sonars are planned for IOC, and other sensors, such as synthetic aperture sonar (SAS) and improved acoustic communications systems (ACOMMS), will be added as they become available. These are currently scheduled to be added in FY06, to provide near-identification-quality imaging. The Precision Underwater Mapping System (PUMA) will be added in FY08, to increase the probability of detection of mines and to provide bathymetry capability as well.
The most significant limitation of the LMRS and the NMRS is their endurance, determined largely by the volume available for energy. In order to provide space for much larger payloads as well as the energy needed to support longer missions, a larger-diameter system is in conceptual development.
Multi-Reconfigurable Unmanned Undersea Vehicle
The multi-reconfigurable unmanned undersea vehicle (MRUUV) is the next step in the development of UUVs. It is intended as the follow-on to the LMRS. The MRUUV will include ISR sensors as well as ASW capabilities. In May 2003, the Navy awarded a $6.7 million design contract to Lockheed Martin for the MRUUV. Its design would have dimensions similar to those of a heavyweight torpedo—measuring 20 ft in length and 21 in. in diameter and weighing about 4,000 lb. The MRUUV will be able to reconfigure for different missions by switching modules. The modules will help the MRUUV perform the various missions, such as maritime reconnaissance, undersea search and survey, communications and navigation aid, and submarine trail and track. Lockheed’s contract includes the development of a “mine identification” module. The MRUUV will be designed with an open architecture for technology spirals that enable less expensive upgrades to its system over the course of its service life. The IOC for the MRUUV is scheduled for FY07. The first platforms to receive the MRUUV will be Los Angeles-class and Virginia-class attack submarines.
Large Diameter Multi-Reconfigurable Unmanned Undersea Vehicle
The large diameter multi-reconfigurable UUV (LD MRUUV) is designed as a large bus, capable of being reconfigured to carry different sensor and mission packages. Virginia-class SSNs and SSGNs are the anticipated classes of host
vehicles. Planned missions would include submarine track and trail, maritime reconnaissance (ISR), undersea search and survey, communications relay, navigation aid, and countermine activities. The diameter is as yet undetermined, but it is anticipated to be much larger than the standard 21 in. torpedo tube, which is the limitation for the LMRS.
LD MRUUV could carry and deploy several smaller, specialized UUVs into a contested area and serve as an energy recharging and data downloading docking station. It would extend the reach of the submarine into contested areas. This system could fulfill many of the roles imagined in the discussion of threats and potential naval operations, as discussed above, particularly ASW; littoral antisurface ship warfare; Special Operations Forces; clandestine intelligence, surveillance, reconnaissance, and targeting; and mine reconnaissance.
The projected IOC for the LD MRUUV is FY13. Technology requirements for this vehicle include a high-performance, renewable energy source, well-developed autonomy capabilities, and long-range, high-data-rate communications.
NAVAL OPERATIONAL NEEDS AND TECHNOLOGY ISSUES
The key naval operational needs and technical issues to be resolved in order to facilitate unmanned surface and undersea vehicles are delineated below. Some are common issues for both the USVs and UUVs:
Autonomous adaptive control systems, able to utilize sensor data in navigational and sensor control decisions. This operational need requires extensive sensor fusion and onboard processing capabilities. Advances in adaptive autonomy are crucial for fulfillment of the needs discussed earlier.
Sensor packages to provide positive identification of mines and other objects of interest. Meeting this need will require high-resolution, acoustic, and optical sensors whose prototypes are currently in development.
In-stride capability. This requirement involves timely detection, identification, and neutralization of mines or other hazards in the sea-lanes of communications and supply, as well as in the littoral regions.
Launch-and-recovery systems for both USVs and UUVs a high priority. This class of needs is most likely platform-specific, not “one size fits all,” although the concepts may be generalized. Without safe and reliable recovery systems and adequate checkout and maintenance space, operations will be dangerous, critical learning in real-world environments will be prolonged, and the acceptance of unmanned vehicles in the fleet will be delayed. Of particular significance in this context is the need for the planning and development of launch-and-recovery systems for the Littoral Combat Ship.
A number of naval operational needs and technical issues specific to UUVs including the following:
Energy storage, navigation, sensing, and control are probably the most significant technology needs for UUVs. Research and development in this area is extensive, particularly in the wireless industries, and their investment in these areas eclipses efforts of the DOD. As with other areas of intense industry interest, Navy UUV developers could leverage industry advances. This is especially important for energy storage, which is likely to continue to make the same kind of slow, steady progress as has been the case in the past. The continuing efforts at miniaturization and corresponding reductions in power-budget needs for sensors, computation, and the like will help alleviate the power needs of UUVs.
The utility of autonomous vehicles is ultimately limited by the quality and quantity of the information that they have to guide them. To remain clandestine, both navigation and communication functions must work undersea with minimal exposure at the surface. High-performance inertial systems may provide suitable navigation for large vehicles, but will be prohibitive for small vehicles for which large numbers and expendability may be appropriate. The current high cost of inertial navigation systems may be alleviated in the future as the demand for these systems increases or as technological advances make them more affordable. For example, the Jet Propulsion Laboratory is developing a microelectromechanical system three-axis assembly that incorporates “tuning fork” gyro sensors and mixed-signal application-specific integrated circuits. These gyro electronics are designed to operate with approximately 12 off-ship components at a power draw of 75 megawatts.3 Alternative technologies, integrated with low-cost inertial systems, may provide accurate UUV navigation in certain environments. Possibilities here might include low-frequency electromagnetic radiation in very shallow water or terrain-following methods.
Since the ocean is relatively opaque to most electromagnetic radiation but transparent to acoustic radiation, virtually all long-range undersea sensing must be acoustic. However, optical sensing can be effective over short distances, on the order of meters, depending on water conditions. The continued miniaturization of acoustic and EO sensors and corresponding reductions in power requirements will make these sensor systems attractive for unmanned undersea systems. The reductions in size and power requirements, together with the expectation of significant onboard processing and fusion of raw sensor data, are extremely important in the context of the limited bandwidth of acoustic undersea communications, especially in shallow-water applications.
For additional information, see the Web site <http://nmp.jpl.nasa.gov/st6TECHNOLOGY/mems.html>. Last accessed on May 18, 2004.
One of the sensor systems that holds the greatest promise for mine warfare is the synthetic aperture sonar. This development appears to be on track and maturing. Once the SAS becomes available in the fleet, the hard work of developing expertise in interpreting the images will begin.
The Precision Underwater Mapping System—the principal integrated sensor package for LMRS and RMS, incorporating precision bottom bathymetry, side-scan and forward-looking sonar—is currently in development. This sensor package will be essential for realizing the capabilities of either LMRS or RMS and subsequent systems.
Navigation and communications are similar and interdependent in the underwater environment. If it is possible for the vehicle to come to the surface, then both GPS and RF or other communications channels are possible. Current methods for acoustic underwater communication in the open ocean are reliably working at rates of 2 to 3 kilobits per second (kbps) over 10 km. With large arrays and special circumstances, 10 kbps over 10 km is possible. To improve significantly on the current state requires the ability to predict and exploit special circumstances in the acoustic propagation characteristics. Improvements in this area will require a sustained effort in research focused on the next generation of acoustic propagation models, signal processing, and computational techniques. Underwater acoustics is an area of special interest and national responsibility for the Office of Naval Research, and one in which ONR has supported a vigorous and effective research effort. This effort needs to be sustained. Underwater acoustics will be the enabling technology for unmanned undersea vehicles.
In shallow water, the communications problem is even more complex and challenging because of the proximity of both the surface and the bottom reflections; this area of active research has met with some success. The rates of 2 kbps in this environment are only achievable under very special circumstances. If it is based on acoustics, the navigation problem is also challenging in the shallow-water environment, although there has been some promising work on using static magnetic fields in the very shallow environment in conjunction with the UGV crawler development. This is certainly an environment in which using GPS and RF communications at the surface may provide the most reliable navigation and communications link.
OPPORTUNITIES FOR IMPROVED OPERATIONS
The Navy has several systems in a prototype stage and in the acquisition process. These need to be used in the fleet so that lessons can be learned, as they have with the Predator and Global Hawk as well as with the smaller UAVs. These lessons and the inevitable and essential feedback to the system developers will both improve the systems and help bring about their acceptance in the naval community.
As discussed in many places in this and other chapters, the development of a robust, adaptive control system to provide reasonable autonomy and enable cooperation will be essential to realizing the opportunities for USVs and UUVs.
The Monterey Bay experiment—a component of the Autonomous Ocean Sampling Network, supported by ONR in the summer of 2003—was the first coordinated field experiment in which multiple UUVs were used in an adaptive observational program. They were used to determine the physical state and structure of a 50 km3 volume of ocean. Multiple, dissimilar UUVs were operating in this volume to determine the temperature, salinity, and optical properties of the ocean water as they evolved over a period of 2 weeks. The vehicles and sensors were guided by the evolving output of a numerical model, which was assimilating the observations as the data were acquired.
The oil and gas exploration industry, along with the oceanographic research community, has led the development of small UUVs because it has required the technology, largely because of the high costs of ship time. Because of the focus on providing specific, focused technologies within limited budgets and time lines, these systems are available today and in wide use. The support for such developments comes from a broad range of sources in the research community, but ONR has played a key role in encouraging these developments. Continued leveraging of these assets and technologies will help in their acceptance and use within the naval forces. This has been the pathway to bringing the REMUS technology to the Special Operations community, which occurred largely through the efforts of ONR, and has led to the recent use of the SAHRV system in Iraq.
CONCLUSIONS AND RECOMMENDATIONS
The conclusions and recommendations based on the preceding discussions are presented in the following subsections.
Conclusions Concerning Unmanned Surface and Undersea Vehicles
Unmanned Surface Vehicle Roadmap
While the Navy’s roadmap for unmanned undersea vehicle development is quite extensive and comprehensive, there is no similar planning document for unmanned surface vehicles. It is clear that the rather long history of development and even operational experience with UUVs facilitated the development of the UUV roadmap. Because USVs are much less mature, there is no similar experience base for them and hence the development of their roadmap will be more difficult. However, USVs can play increasing roles in the future, and a roadmap of their development is necessary.
Adaptive and Cooperative Autonomy
Improvements in the autonomous capabilities of USVs and UUVs are crucial to their future development. Of particular importance is the ability of these systems to adapt intelligently to changes in their tactical situations. As the missions of these vehicles evolve, it is inevitable that the tactical situation of specific missions will change, and their onboard sensing systems will indicate such changes. The onboard systems must be capable of recognizing the changes and adapting the mission plan accordingly, without the need for intervention by operators. Similarly, there is an increasing need for onboard autonomy that can facilitate the employment of multiple cooperative vehicles, both unmanned and manned.
Energy Storage for Unmanned Undersea Vehicles
The range and endurance of UUVs are directly dependent upon their onboard energy-storage capabilities. It is incumbent upon the Navy to keep cognizant of all commercial developments of energy-storage technologies and, in addition, to selectively fund the development of energy-storage technologies that are particularly applicable to UUV needs.
Launch and Recovery
Unless there are safe and effective systems for the launch and recovery of USVs and UUVs, these vehicles will not find their way into operations. In particular, there is an important need for launch-and-recovery systems for USVs while the mother ship is under way. Similarly, launch and recovery of UUVs, both at and below surface, are increasingly important.
Sensors for Mine Hunting
Mine hunting is possibly the most significant current mission for both UUVs and USVs. A sensor system to allow onboard recognition and classification of mines is an important technological need. In this context, the further development of synthetic aperture sonar technology is an associated need.
The need for high-bandwidth underwater communications for command and control of UUVs will be alleviated to some extent by increased autonomous capabilities of UUVs. However, further development of underwater communications methods for the transmission of sensed information and other needs is of paramount importance.
Logistics Needs of Autonomous Vehicles on the Littoral Combat Ship
While autonomous vehicles of all types are likely to be important contributors to the overall capabilities of the Littoral Combat Ship, there appears to be little or no planning for the maintenance and checkout space, launch-and-recovery equipment installation, and logistics support needs of these vehicles in the current development of the LCS. This planning needs to be accomplished.
Tracking Commercial Developments
The commercial-sector investment in technologies applicable to the missions of both USVs and UUVs dwarfs the investment that can be made by the Department of Defense. Hence, it is crucial for the Navy to be cognizant of commercial developments and to take maximum advantage of those developments insofar as they are relevant to the Navy’s development of USVs and UUVs.
The Navy has a long and distinguished history in the development and testing of methods for monitoring the sea environment. It is important for the future development of USVs and UUVs that this area of technology development be continued and strengthened in areas synergistic with USV and UUV developments.
The complexity of complete UUV/USV systems, including the launch-and-recovery subsystems, demand well-planned and well-executed operations and maintenance training for those responsible for these systems.
Recommendations Concerning Unmanned Surface Vehicles and Unmanned Undersea Vehicles
Recommendation: The Navy and Marine Corps should aggressively exploit the considerable warfighting benefits offered by autonomous vehicles (AVs) by acquiring operational experience with current systems and using lessons learned from that experience to develop future AV technologies, operational requirements, and systems concepts. Specifically:
Accelerate the Introduction of Unmanned Undersea Vehicles. The Chief of Naval Operations (CNO) should direct the Commander, Fleet Forces Command, to deploy and evaluate systems such as the Long-Range Mine Reconnaissance
System, the Remote Minehunting System, and the Remote Environmental Monitoring Unit System in order to refine concepts of operations, cost issues, logistics, and handling.
Recommendation: The Assistant Secretary of the Navy for Research, Development, and Acquisition (ASN(RD&A)) and the Chief of Naval Research (CNR) should direct the Navy and Marine Corps Systems Commands, the Office of Naval Research (ONR), and the Marine Corps Warfighting Laboratory (MCWL) to partner with the operational community and monitor the concepts and development of critical autonomous vehicle-related technologies considered essential to the accomplishment of future naval missions. The progress of these developments should be tracked year to year. Specifically:
Pursue New Unmanned Surface Vehicle/Unmanned Undersea Vehicle Concepts and Technology Developments. The Chief of Naval Operations should establish a high-level working group to refine the requirements and concepts of operations for unmanned surface vehicles and other autonomous vehicles as an integral part of the Littoral Combat Ship (LCS) and other naval operations. Once the LCS design is completed, planning for logistical support, maintenance and handling space, and launch-and-recovery systems for autonomous vehicles should be incorporated.
The ASN(RD&A) and the CNR should direct the ONR to monitor commercial developments in unmanned surface vehicle (USV)/unmanned undersea vehicle (UUV) technologies and to take maximum advantage of those developments for meeting the Navy’s needs. Specifically, the ASN(RD&A) and the CNR should direct ONR to invest in and develop networks of small UUVs. These efforts should include the leveraging of research and experimentation within the oceanographic research and oil exploration communities.
The ASN(RD&A) and the CNR should direct the ONR to conduct research into adaptive and cooperative autonomy and communications. ONR should develop better energy sources, as well as launch-and-recovery systems and environmental sensors for UUVs and USVs. Increased investment is needed in basic research and development in the areas of acoustics and optics as well as in sensors for mine hunting, including synthetic aperture sonar. ONR and the Naval Air Systems Command should focus on the modularity of components (propulsion, energy, and sensors), common architectures, common mission planning, and common integration pathways for data. The ASN(RD&A) and the CNR should ensure that UUVs and USVs, whenever possible, meet the interoperability and communications requirements of the Department of the Navy’s FORCEnet operational concept.