The Earth's oceans are the central engine of the energy and chemical balance that sustains humankind. They provide warmth and power. They moderate the weather so food can be grown on land to feed the Earth's population. Their living resources also supply food. Understanding them is one of humanity's most important challenges.
The United States, as a leading maritime nation, relies on the ocean more than most. It has one-fourth of the world's trade and the largest standing navy. Investments in ocean science and technology by U.S. government and industry lead the world. But support for those investments has waned steadily in recent decades, even as the need for knowledge of the ocean, in all of its dimensions, has grown. The nation faces decisions that will require substantially more information about pollutant concentrations, climate change, the ocean food chain, and the hydrocarbon and mineral resources beneath the ocean and on the bottom.
Humanity's first scientifically based knowledge of the ocean came from observations made aboard surface vessels and from instruments put into the sea. Later came aircraft and satellites with sensors aboard. Underwater vehicles augment these capabilities by making it possible to go far beneath the surface, giving human beings firsthand information about how the oceans work. Early bathyspheres took explorers to spectacular depths. Four decades of exploration with undersea craft have since offered glimpses of many facets of the oceans' wonders, suggesting how much there is yet to discover. Recent oceanographic and geologic discoveries of immense significance made while using undersea vehicles, such as the stunning discovery of hydrothermal vents at mid-ocean plate boundaries with associated chemosynthetic food chains, are tantalizing examples of how much more there is to learn about the sea.
Advances in guidance and control, communications, sensors, and other technologies for undersea vehicles offer an opportunity for a great leap in understanding the ocean engine. Together these advances have led to the evolution of remotely piloted and autonomous undersea vehicles, which may extend the human reach beneath the sea, offering more cost-effective and capable systems for some missions than those used today.
This report, developed by a balanced team of ocean scientists, underwater vehicle development engineers, and managers in both government and industry, assesses the value of investments in underwater vehicles. On the basis of that assessment, the committee offers recommendations for definitive actions that will lead to systems that offer access to knowledge and tools that protect and enhance human life.
Undersea vehicles are of three types:
Deep submersible vehicles (DSVs) are human-occupied and are generally used to descend to great depths (up to 6,500 meters), with up to several kilometers of horizontal mobility on the bottom. They are used for a variety of tasks requiring human observation or recovery of objects or samples. They have relative brief endurance (owing to human limitations) and are relatively costly to operate and maintain, in part due to provisions to ensure human safety.
Remotely operated vehicles (ROVs) are unoccupied, tethered vehicles with umbilical cables to carry power, sensor data, and control commands from operators on the surface. ROVs are widely used in the offshore oil and gas industry for a variety of inspection and manipulation tasks and in laying undersea cable. They are also used in ocean research. ROVs are maneuverable within the limits of their tethers (a radius of up to a kilometer) and have nearly unlimited endurance on the bottom. Large ROVs used for research commonly operate from dedicated surface support ships. (In industry, they may be operated from construction or production vessels or platforms using temporary launching and retrieval equipment.)
Autonomous underwater vehicles (AUVs) are unoccupied submersibles, without tethers, powered by on-board batteries, fuel cells, or other energy sources. Currently, they are intended to carry out preprogrammed missions, with little or no direct human intervention. The ability to achieve human strategic control of AUVs in near real-time is now within reach. Still experimental, AUVs have yet to see wide operational use.
The capabilities of these vehicles have grown dramatically in the past two decades or so. In particular, advances in sensors, control systems, communications, and manipulators have made ROVs increasingly strong and versatile performers to the extent that they have largely replaced DSVs in commercial operations. These technical advances also have opened the potential for operational AUVs able to carry out complex and precise survey or sampling missions. DSV technology is considered generally mature. AUVs offer the greatest potential for expansion of capabilities as the result of investments in development, although both ROVs and DSVs will remain important tools of science and industry. AUVs promise to open new areas of research and new ways of doing work undersea, if their development is supported. Many of the technology developments carried out for AUVs will be applicable to other vehicle types.
The United States was globally preeminent in undersea vehicle technology in the 1960s and 1970s, but today there is no concerted government program to develop and use these systems. Other nations, including Japan, Canada, France, the United Kingdom, and Russia, have carried the technologies forward. Since the early 1970s the United States Navy has not built a single DSV, and commercial interest in advancing the technology has faded. The ROV technology base has shifted from military programs to private industry, which develops the technology of these robust and versatile systems to meet the growing demands of the offshore oil and gas industry and other customers. There are now over a hundred work-class ROVs operating worldwide, and this count is continuing to increase at a rate of 10 or more per year. Developing major AUV technology remains the concern of government programs.
The nation still has a strong operational undersea vehicle capability, mainly in U.S. Navy hands. The vehicles are increasingly outdated but quite capable and varied. With the end of the Cold War, the Navy opened access to its DSVs more widely to scientific researchers. The Deep Submergence Science Committee—supported jointly by the National Undersea Research Program of the National Oceanic and Atmospheric Administration, the National Science Foundation, and the U.S. Navy—oversees the Alvin and Medea-Jason vehicle facility at the Woods Hole Oceanographic Institution and, as an added task, reviews proposals for the use of these vehicles as well as other government-owned vehicle assets used in nonmilitary research. The Deep Submergence Science Committee also assists in scheduling scientific missions using these assets. The U.S. Navy and National Science Foundation are responsible for the costs of running most of the vehicles. The Navy DSVs, Turtle and Sea Cliff, are now available for civilian purposes up to 60 days each year. The DSV Alvin and the ROV Medea-Jason, owned by the Navy and operated by the Woods Hole Oceanographic Institution, are used full-time for civilian science.
Some advanced research in vehicle-related technologies is being conducted at private oceanographic institutions in the United States, particularly by the Monterey Bay Aquarium Research Institute (in ROVs and AUVs) and by the Harbor Beach Oceanographic Institution (in DSVs).
UNDERSEA VEHICLE CAPABILITIES AND TECHNOLOGIES
As a first step toward setting development priorities, the committee reviewed each of the technologies for undersea vehicles at both the system and subsystem levels. Undersea vehicles should be considered as systems, in which the human operator and vehicle subsystems and components are integrated to achieve optimal performance. For that reason, any technology development program should focus on systems integration. Systems integration requires that vehicle subsystems, payload subsystems, and surface support be perceived as a whole.
The committee reviewed each of the vehicle subsystems and made the following observations about their relationship to overall vehicle capability and their potential for improving vehicle performance.
Mission guidance and task control together form one of the most fruitful areas of technology for undersea vehicles. Advances in the theory of automation have made possible so-called supervisory control, in which the human operator provides high-level, task-oriented commands rather than exercising direct control over all functions of the vehicle. The vehicle systems carry out the detailed control movements to accomplish the tasks. For example, when a sampling task is performed in mid-water, the moving vehicle and its manipulator are controlled as a single system. Further developments in this technology will have strong synergies with advances in navigation and sensors. Obviously, this technology area holds the greatest benefits for ROVs and AUVs. In the future, AUVs should be capable of pursuing tasks with abstract descriptions, such as finding and following a chemical gradient or surveying a given area with the ability to replan and reconfigure the mission based on a wide range of changing internal and external factors.
Communications comprise a critical set of technologies for undersea vehicles, drawing on active developments in the electronics and telecommunications industries. DSVs use communications transmitted through the water acoustically; ROVs use copper or fiber-optic umbilicals; and AUVs communicate through acoustic links. Recent improvements in digital acoustic communications, using data compression, show great promise for control of AUVs by using signals of increasing bandwidth for near real-time command. AUVs could use satellite communications to transmit data ashore using surface buoys equipped with transmitters (although bandwidth is limited by the instability of floating platforms). However, recovery to the surface of real-time data collected by payload sensors is still a major technical hurdle.
Data processing holds many challenges, owing mainly to the need to manage the multiple streams of data from sensors of varied purposes, including both vehicle control sensors and payload sensors, such as sonars or video cameras. Modern database technology and automated processing of optical and acoustic images hold great promise for improvements in this area.
Navigation and positioning subsystems use various combinations of acoustic sensors, video imaging, inertial guidance systems, and the Global Positioning System, depending on the application. The greatest advances in undersea navigation in the near future will come not from advances in particular systems but from integration of multiple subsystems and components.
Energy subsystem improvement represents a variety of important development goals; the size, cost, and duration limitations of AUVs will be mitigated only when practical, safe, and readily available high-energy density sources are developed. Energy sources have a lower development priority for DSVs and ROVs, the performance of which is limited by other factors.
Propulsion subsystems represent mature technologies; existing systems are adequate for most foreseeable applications. The committee found no technology that promises significant improvements in the efficiency of propulsion.
Materials and structures generally represent mature technologies, although some advances would be needed if deepest ocean depth DSVs (capability to 11,000 meters) were sought. Also, some specialized materials, such as ultra-lightweight structural systems and antibiofouling coatings, would be critical for long-duration missions.
Payload subsystems are carried by vehicles for performing mission tasks. These subsystems involve the following elements:
Sensors in the context of payload systems are used to collect data, as distinguished from those used in guiding and controlling the vehicle. They include various acoustic, optical, and chemical sensors; conductivity, temperature, and depth sensors; fluorometers and transmissometers; magnetic field sensors; gravity sensors; and current meters. All sensors have potential for important advances. However, improvements in acoustic and optical sensors should receive priority, owing to the breadth of their applications.
Task-performance subsystems include manipulators and other tools. The development challenge is to take full advantage of new control techniques, with drills, cutting tools, wrenches, or other tools and with task-level control to enable operations like the gentle capture of a gelatinous creature. Research and development in the space program is an important potential source of advanced techniques.
Physical samplers are used to collect samples in situ. An especially important development is physical samplers that have the ability to capture live organisms and subsequently maintain them at the same pressure and temperature.
Surface support includes logistics, positioning, data retrieval and processing, and launch and recovery. The launch, recovery, and vehicle handling functions are particularly important operations that reflect logistical support conditions, equipment, capability, and crew training. Techniques for launching DSVs and ROVs are generally adequate; improvements are likely to have an incremental influence on overall system performance. An exception is research related to mitigating snap loads in long ROV umbilical lines when vehicles are deployed from small vessels; however, launch and recovery techniques for AUVs are still evolving. To take advantage of an AUV's lower cost and minimized surface support, new launch and recovery techniques will be required.
FOCUSING ON VITAL NATIONAL NEEDS
Assessing the subsystem technologies is insufficient without primary attention to full systems. To provide a grounding for this systems approach, the committee reviewed many of the ways undersea vehicles could help further the national interests in an extremely important range of scientific, regulatory, military nonclassified, and industrial applications.
Many scientific and technical fields are strongly dependent on undersea vehicles. Fundamental studies of deep ocean trenches, spreading centers, and faults using undersea vehicles have helped confirm and elaborate the theory of plate tectonics. Oceanographers can use these systems for studies of the geochemical and energy cycles of the atmosphere and ocean, bearing centrally on the future of climate and the biological productivity of the oceans.
Undersea vehicles are already showing evidence of their utility in observing commercial fish stocks and assessing harvesting techniques. They are critical to developing offshore
oil and gas resources and laying undersea cable, as well as to the efforts of salvors and treasure hunters. Undersea vehicles may one day help in developing and monitoring waste storage sites on the remote deep abyssal plains at depths of more than 3,000 meters (approximately 10,000 feet).
To illustrate these potential contributions, the committee developed four "focal projects" describing potential applications of undersea vehicles in support of national needs (see Chapter 3). Some of these projects rely on technology that is available and economically feasible today; others are more visionary. All four projects address selected high-value missions or applications and employ multiple technologies useful in a wide range of undersea vehicle missions. They make possible tasks heretofore unachievable or impractical. They have potential for multiple use of vehicles or technologies for commercial, military, and scientific needs. Certainly they do not exhaust the potential for innovative uses of undersea vehicles. Nor are they intended to be a representative sample of potential applications. They simply offer a few challenging examples. In each case the committee established system performance requirements and commented on the state of the relevant technology.
All of the focal projects use AUVs as their primary vehicles. In the committee's judgment AUVs promise more payoff in advanced capabilities than DSVs or ROVs, which are technologically relatively mature. At the same time, DSVs and ROVs could be used in a variety of functions in these projects, not only in surveying and construction but also as alternatives to AUVs in some missions.
The focal projects for potential applications of undersea vehicles are as follows:
Synoptic Observation System. This concept would use AUVs to make high-resolution measurements of chemical and temperature gradients in the water column over areas of several hundred square kilometers and for periods of up to several years. The AUVs would have a central control and battery-charging base and an array of bottom-fixed instruments and navigation aids. These vehicles will contribute importantly to modeling how the ocean functions to affect climate and the undersea food chain and to understanding tectonic processes (which relate to earthquake prediction).
Blue Water Oceanographic Sections and Hydrographic Survey. These activities would involve the operation of one or more AUVs in synchrony with a surface ship to improve dramatically the accuracy and efficiency of oceanographic data-gathering—another important part of modeling the ocean's function and predicting the climate.
Subsea Oil Field Inspection and Intervention. This application of an undersea vehicle would use an AUV "garaged" at a central platform to make periodic inspections and maintenance of subsea oil and gas wellheads in the surrounding area—a task done better by an undersea vehicle, at much reduced cost, than by a surface-supported system. The subsea wellhead is an essential element in the development and operations of oil and gas resources in the new high-volume production fields of the Gulf of Mexico. In every case, the development of AUV capability to respond to shore-based, human, real-time task-management will improve AUV operational cost efficiency by a major factor.
Search and Survey. This effort involves the development of a versatile AUV system to carry varied suites of sensors, at depths of as much as 6,000 meters, to search the bottom for objects (such as lost aircraft) that have high-value for the safety of air travel or regional defense and to make wide area surveys of geological features (including mineral deposits) to assess resources of potential long-term value to the nation.
SETTING DEVELOPMENT PRIORITIES
The total system technology assessment and the review of national needs lead inevitably to the question of development priorities. This judgment involved a two-step analysis of the subsystem technologies. First, the committee ranked the subsystem technologies according to their impact on vehicle performance as "critical" (those whose improvement would enable important new capabilities, not otherwise achievable), "incremental" (those whose improvement offers significant, but not critical, improvements in efficiency or utility), or "mature" (those whose improvement would contribute only incrementally to vehicle performance). The committee then ranked the subsystem technologies deemed critical according to their likelihood of benefiting from development efforts. The technologies were ranked either "greatest potential" or "high potential." This sifting process revealed that three of the critical subsystem technologies offer the greatest potential for significant improvement in undersea vehicle performance and significant contributions to national needs:
ocean sensors (acoustic, optical, and chemical)
undersea communications (particularly digital acoustic methods)
mission and task-performance control (with an emphasis on high-level, task-oriented control architecture)
These technologies should be the focus of investments in developing vehicle systems. However, major advancements in these three subsystem technologies will need to be integrated into complete vehicle systems, tested, and applied to missions such as the ones outlined in the four focal projects above.
ENHANCING THE NATIONAL CAPACITY
The national undersea vehicle capability for undersea work and research involves three aspects:
availability and access to resources (coordination and scheduling of scientific and other uses) to scientific users with sufficient funding to support operations and studies (see Chapter 5)
capital investment (by public and private sectors) in DSVs, ROVs, and AUVs and the support vessels and other assets that support their operation (see Chapter 4)
The nation currently lacks an effective system for coordinating and planning these capabilities. The government-operated systems that would support undersea science and ensure a national capacity for deep ocean recovery and salvage are not well coordinated. Declining budgets for the Navy's submarine force, which provides many of the necessary systems, have put pressure on continued maintenance of the Navy's undersea vehicle assets; the users, who receive the benefits of these systems, have no authority or responsibility for their funding. The systems themselves are generally adequate for present purposes, but they are not efficiently managed, especially for science, and they will fall far short of meeting the critical national needs of the imminent future. The private sector has successfully managed investment in new technology and new systems of industrial interest, such as ROVs. These systems, adapted to scientific and national security missions, are increasingly capable and have important potential that is only beginning to be tapped.
A disciplined process of strategic planning is needed, with a long-term vision for assessing national needs and monitoring progress by the public and private sectors to meet those needs. Such a plan would not require a single, centrally directed undersea vehicle program; the vigor and variety of today's multiple-agency approach are valuable strengths. Coordination and planning can coexist with diversity, which is not to say that today's division of responsibilities must be maintained rigidly. Caught between declining military budgets and expanding ocean frontiers, the community must make better use of its resources and establish a more stable funding scheme.
CONCLUSIONS AND RECOMMENDATIONS
On the basis of its review, the committee developed the following conclusions with regard to undersea vehicles.
Conclusion 1. The nation has vital economic and scientific needs to significantly advance its capabilities for working, monitoring, and measuring in the ocean. Those needs involve national security, environmental protection, resource exploitation, and science. Undersea vehicles can contribute strongly to these capabilities by giving human beings access to new kinds of information about little known areas of the ocean and the seabed—information that may have a major impact on the well-being of large populations.
Conclusion 2. Technical advances are needed if the nation is to realize this potential; the priorities for these technologies are ranked in Chapter 4. The nation needs the ability to carry out construction support tasks, inspection, and maintenance in deep sea oil and gas fields safely and efficiently, using remote control. Autonomous undersea vehicles in synchrony with research vessels can help gather oceanographic and hydrographic data more accurately, quickly, and cheaply. Monitoring pollution and measuring the conditions that could lead to global climate changes will be easier with new chemical sensors. Surveying the bottom with the high-resolution offered by undersea vehicles is likely to reveal valuable mineral deposits and assist in the location and recovery of objects related to public safety and security.
Conclusion 3. The committee finds the technological advances most critical to these important missions are in the areas of ocean sensors, subsea communications, and mission and task-performance control systems.
Conclusion 4. The vehicle technologies are generally mature enough to place the emphasis of technology advancement programs appropriately on systems integration.
Conclusion 5. Other countries today, like the United States in the past, have mounted focused programs with sustained support in the service of well-defined national needs.
Conclusion 6. The United States has no concerted program; instead it has a number of informally coordinated programs and no disciplined mechanism for long-term planning. The financial disjunction between users and the federal providers of undersea vehicles in some cases impedes coordination.
Conclusion 7. Failure to address the deficiencies of federal programs will constrain scientific progress, limit the nation's ability to develop and manage its ocean resources, and compromise national security and law enforcement.
The committee's recommendations are outlined below.
Recommendation 1. The nation should develop, maintain, and follow a long-term plan for federal undersea vehicle capabilities that takes into account all of the available facilities for undersea research.
Recommendation 2. In developing undersea technology the nation should meet its needs through combining government programs, joint technology agreements with foreign programs, and cooperative industry-government programs. Maximum use should be made of programs outside the federal government. All decisions should be based on the long-term plan recommended in this report.
Recommendation 3. Capital investment programs should take advantage of partnerships—from leases of U.S.-certifiable foreign submersibles to joint development and use of new vehicles and support vessels with industry and foreign
programs. The federal government should buy wholly new vehicles for civilian use only when other sources are not available and the national interest (as determined by the planning process recommended here) demands it.
Recommendation 4. In ensuring user access to undersea vehicles, the nation should maintain the pluralism of the present approach with a variety of funding agencies. The flexibility and local innovation of that approach are major strengths of the U.S. system of science and technology. At the same time, the agencies involved should be guided by a shared strategic view of future needs.
Recommendation 5. Stable funding should be provided for those undersea vehicle systems that are viewed as national assets.