MOTIVATION AND OBJECTIVES
The United States has one deep-diving nuclear-powered research Submarine-the NR-1. The NR-1 was built in 1969 with state-of-the-art technology as an ocean engineering and research support submarine. It was designed for prolonged operation (30 days) on or near the sea bottom at a speed of up to 4 knots. These characteristics distinguish the NR-1 from the majority of deep submersibles, which are essentially adjuvant vehicles operated from surface vessels. Such vehicles are typically subject to conditions in the water column or on the surface and have limited mobility. Unlike most nuclear submarines, the NR-1 has viewports, along with manipulators that allow the crew to handle small objects.
The NR-1 is an important national asset for a variety of reasons. It has been instrumental in the search for and recovery of underwater wreckage from military aircraft accidents. It was used to map the debris field from the explosion of the space shuttle Challenger (when other vessels were hampered by inclement weather) and to obtain forensic information in the crash of EgyptAir Flight 990. The NR-1 has also been used in support of maritime archaeology, oceanographic research, and military operations.
The NR-1 has been refueled and modernized twice. The Navy anticipates that it will require another refueling or replacement by 2012 and has begun to consider what capabilities a replacement, which we here call the NR-2, should have. In this connection, we at RAND were asked by the Navy to assist in two respects:
Identifying and prioritizing the range of missions the NR-2 would likely be required to execute.
Establishing the range of capabilities that would have to be incorporated to accomplish those missions.
Taken together, these missions and capabilities form a concept of operations (CONOP) for the NR-2. Other issues relevant to the Navy's considerations presented themselves in the course of the study and were addressed. These included whether a follow-on to the NR-1 was really needed, whether construction of the NR-2 might be funded and the vessel operated by the private sector, and whether the NR-2 needed to be manned. We also propose two initial design concepts. These and the CONOP underlying them can serve as inputs to elaboration by the Navy in an analysis of alternatives that would compare costs and benefits.
Our work on NR-2 missions, capabilities, and design concepts has been informed by the perspective that the NR-2, if built, is likely to be a platform of greater national importance than the NR-1. National undersea security priorities are expanding. The importance of the ocean sciences and related environmental and global issues are drawing increased recognition. Undersea fiber-optic cables are an increasingly important element of the national information infrastructure-an infrastructure that might be viewed by future adversaries as a tempting target.
Without the capabilities that could be provided by the NR-2, we would forfeit, as far as the oceans are concerned, the Joint Chiefs of Staff's Joint Vision 2020's goal of dominance across the full spectrum of conflict arenas-physical and electronic.
To accomplish the tasks assigned, we convened three conferences, where experts in science, national security, and submarine operations contributed to defining likely mission profiles required between 2015 and 2050. These profiles provided the basis for prioritizing design-driving capabilities-i.e., those having a large impact on platform cost-for the NR-2.
For each of the three conferences, we used a "group systems" decisionmaking support approach in which participants used networked laptop computers to identify and prioritize potential mission tasks and capabilities for a new deep-diving submersible. Participants were encouraged to discuss these options openly but also to submit comments and prioritize items anonymously via the computer network. The latter permitted contribution and exchange of viewpoints freed of the reserve that might accompany the expression of opinions in the presence of persons of higher rank or seniority.
Limitations to this approach include those inherent in a group discussion, as opposed to a labor-intensive analysis by a team of experts. The time and analytic tools available could not allow a completely thorough discussion of alternatives and the trade-offs and other analytical considerations they entailed-although such depth of analysis is not essential at this stage. The disciplines represented might not have been sufficient, or the nomination and winnowing process flexible enough, to incorporate the full range of future science missions. Further, the approach could not eliminate biases, but it did allow us to recognize and isolate them.
This summary is organized as follows. After providing some background, we summarize the results of the conferences on scientific and military missions and the capabilities required to perform those missions. We then present two possible design concepts for the NR-2 before offering some concluding observations.
BACKGROUND ON THE NR-1
To gain some perspective on the capabilities proposed below for the NR-2, it will be useful to more fully describe NR-1 capabilities than we did on pp. 1-2. For a view of the NR-1's physical layout, see Figure S.1.
While the NR-1 has a forward-propulsion system and two pairs of thrusters to help it rotate, move laterally, or maintain position in a current, it was not designed to operate autonomously. Because it can manage no more than 4 knots (about 4 miles per hour), it is normally towed to and from operating areas by a dedicated support ship. The NR-1 also relies on its support ship for storing retrieved objects, retrieving large objects, rotating science teams or crew members, and replenishing its compressed air system. (Compressed air is needed to surface, by blowing seawater out of ballast tanks; to recharge scuba equipment; and for emergency breathing.)
The NR-1 is equipped with sensors for basic environmental data and with the means to record scientific data. The NR-1's three viewports provide a view forward and down, complemented by 25 external lights, low-light-level 35-mm still cameras, a digital still camera, a color video camera, and other vision aids. The three-dimensional perspective furnished by viewports has been important for ship safety when the NR-1 has been operating near the bottom, and the viewports have been used extensively by scientists. They are of limited use, however, in turbid water, and their locations on the hull have at times limited their utility. The digital camera has permitted real-time images without worries about film exhaustion or flash synchronization.
Complementing its viewing systems, the NR-1 is equipped with a variety of sonars. The most commonly used is an obstacle avoidance sonar, which can help not only in locating obstructions but also in searching and mapping the bottom. While state-of-the-art for its time, this sonar looks forward only; and even in that direction, it has not always detected obstacles as rapidly as desired. Side-looking sonar can also be used to map the seabed, and bottom mapping at high precision is enabled by a laser line scanner. A Doppler sonar provides precise position (accurate to about a foot) relative to the bottom and can also aid in seabed mapping. These bottom-mapping instruments detect not only variations in the ocean bottom itself but also the presence of objects, such as debris, resting on it.
On the surface, the NR-1 uses the Global Positioning System (GPS) and other navigation systems. When submerged but not near the bottom, the NR-1 has used dead reckoning to estimate its position. This practice is not precise, so it has been supplemented by communication with the support ship, whose position is known with GPS accuracy, which can track the NR-1 acoustically and communicate the NR-1's position to the NR-1. On the bottom, the Doppler sonar can be used for precise navigation.
The NR-1 has two retractable rubber-tired wheels that support it on the ocean bottom, where ballast and thrusters help it maintain a position. The ability to operate on the bottom at depths to 3,000 feet has allowed the recovery of aircraft debris, permitted such scientific studies as the observation and collection of manganese nodules on the ocean floor, and provided a "safe harbor" during sonar repairs. Wheels provided an ability to fine-tune NR-1's position on the bottom in missions that require fine position manipulation. A hovering submarine cannot be maneuvered as precisely as a bottomed submarine using wheels. Also, currents tend to affect hovering submarines. Precise position adjustments could sometimes be accomplished reliably only by bottoming and using the wheel system.
The NR-1's manipulator can handle small objects (no more than eight inches in diameter) and place them in sample baskets for storage. It also has a recovery claw for somewhat larger objects. The manipulator lacks operator feedback and can inadvertently crush fragile objects. The NR-1 also has a "jetter"-a water jet system for uncovering or burying objects on the bottom.
By the standards of modern submarines, the NR-1 is small. It is about 145 feet long, and 96 feet long inside the pressure hull. Its beam (maximum diameter) is 12.5 feet. The nuclear propulsion plant provides endurance limited only by the vessel's food and air supply, which is sufficient to sustain its two-person crew plus two scientists for up to 30 days. In contrast to modern U.S. nuclear submarines, the NR-1 uses a chlorate "candle" system to generate oxygen. Carbon monoxide and hydrogen produced by the system are removed from the atmosphere by a catalytic converter. Replaceable lithium-hydroxide canisters remove carbon dioxide.
In case of an emergency, the NR-1 can communicate by high-frequency radio over long distances when on the surface. The ability to sit on the bottom can provide a refuge. In the event of an underwater emergency, the NR-1 can release lead shot to increase buoyancy for return to the surface.
SCIENCE MISSIONS AND CAPABILITIES
Missions. Conference participants identified, characterized, and prioritized nine types of NR-2 science mission that might be carried out between 2015 and 2050. Table S.1 lists the nine missions in rank order.
Rankings are displayed quantitatively in Figure S.2. These rankings reflect a variety of perspectives. They are the composite of four separate ranking exercises (displayed in Figure S.3), each with a different criterion and different participants. Missions were ranked according to
scientific value, by scientists only,
scientific value, by all conference participants,
likelihood of federal agency funding, by agency representatives only, and
projected importance to the nation between 2015 and 2020, by all conference participants.
Within each mission, objectives or subareas were ranked by specialists in that discipline. To give a sense of mission character, we listed in Table S.1 two or three illustrative objectives for each.
Capabilities. Working from information provided by scientists, ship designers, experienced submarine operators, and the Naval Sea Systems Command, RAND identified a set of potentially desirable NR-2 capabilities. These were ranked in importance by scientists participating in the conference as follows:
Under-ice capability. Scientists agreed that the ability to operate under ice was desirable.
Remotely operated vehicle (ROV) capability. Ability to employ ROVs or autonomous undersea vehicles. For every mission except ice science and atmospheric science, scientists judged such vehicles desirable.
Endurance. The consensus was that a minimum of 30 days time on station was needed for all missions except maritime archeology and that 45 days would be desirable for most missions.
Submerged speed. Scientists thought greater speed necessary to obtain longer survey tracks in a given time available. Speeds of 8 to 10 knots were judged adequate for all missions, and 15 knots desirable.
Maximum operating depth. Scientists agreed no mission would require an operating depth greater than 1,000 meters (3,300 feet).
Crew size/augmentation. Scientists found it difficult to meaningfully project needed science team size, which would likely be driven-as in the past-by the details of the mission and space available, as well as other ship capabilities. Some scientists suggested that-in the future-depending on mission areas, science teams might be unnecessary. This was the characteristic they were most willing to trade away.
Mission record reviews and discussions with ship operators and scientists revealed a broader range of capabilities required for each mission area. The following mission capabilities were identified as the most broadly applicable for science missions:
multipurpose acoustic suite,
precise navigation system,
operation on or near the bottom,
ability to launch, operate, and recover adjuvant vehicles or towed sensor arrays,
in-situ water sampling,
ability to undertake coordinated measurements of scientific data, and
3-D vision and external, segregated stowage.
MILITARY MISSIONS AND CAPABILITIES
Missions. Potential military missions for the NR-2 were developed and prioritized through two conferences involving civilian and military defense experts, including submarine design experts. They are listed, in composite rank order, in Table S.2. Possible objectives are also given, although here they are simply representative. No priority within mission is implied.
Quantitative priority ratings are shown graphically in Figure S.6. These ratings are the product (normalized to 1.0 for the highest-priority mission) of two other rankings: mission criticality, defined as the relative impact of mission failure on national security (should it be conducted) (shown in Figure S.4) and the expected future frequency of occurrence of the mission (shown in Figure S.5).
The priority scores in Figure S.6 strongly favor the mission to protect national seabed assets, which was ranked first in frequency of occurrence and second in criticality. The frequency ranking derives from two factors. The first is the growing importance of seabed fiber-optic cables to the U.S. information infrastructure, and the attendant vulnerability they represent. The second factor is that, if built, the NR-2 would be the only dedicated national asset capable of protecting the seabed infrastructure and deterring efforts to damage it. In other words, any time the need for protection or deterrence should arise, the mission could fall to the NR-2.
Covert operations are scored last because of the expectation that the need to conduct them would be rare. The low score of this mission, combined with its distinctively offensive profile, indicates that the consensus of conference participants was that the NR-2's value would be in gathering information and intelligence from sea bottom operations, not from employment as a combatant. This is also consistent with three broader views of the participants:
The NR-2's leverage would be in completing the national "full spectrum" capability for intelligence preparation of the battlespace.
The NR-2's value would increase as the transition continues to a cyberwar environment.
The President and Secretary of Defense have at their disposal many other special operations assets to accomplish "direct action" combat missions.
Excerpted from A Concept of Operations for a New Deep-Diving Submarineby Frank W. Lacroix Robert W. Button Stuart E. Johnson John R. Wise Copyright © 2002 by RAND. Excerpted by permission.
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