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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms 3 Naval Air Platform Technology OVERVIEW OF FUTURE NAVAL AIR TECHNOLOGY Initial Observations In reviewing relevant technologies and formulating its findings, the panel took special note of significant trends in employment concepts for air platforms: Increased emphasis on long-range, precision weapons, launched from both aircraft and surface vessels; Expanded consideration of off-board sensing and targeting; and Growing concerns about employing manned aircraft in combat operations over land, particularly during daylight hours. It will be important to strike a balance among tactical air platforms, sophisticated weapons, and off-board sensors in order to provide the most cost-effective approach for the future. Acknowledging calls for increased emphasis on unmanned aerial vehicles (UAVs) for a variety of support and lethal missions, the panel believes that the argument over manned and unmanned aircraft—although an important one—is not the real watershed decision for 21st-century naval aviation. The cardinal aircraft issue for future decision-makers is that of tactical aviation (Navy, Marine Corps, Air Force) versus standoff weapons, long-range bombers, and ship or shore basing. This issue is not addressed here, but nevertheless must underlie any consideration of the future character of naval aviation.
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms Vision of Naval Air Platforms for 2035 A More Vertical Force Naval aviation, both afloat and ashore, is likely to become a more vertical force in the future. There will be increased reliance on air vehicles, both manned and unmanned, with short takeoff and vertical landing (STOVL), vertical takeoff and landing (VTOL), and short takeoff and landing (STOL) characteristics that have excellent payload, range, and low-signature capabilities. Takeoff and landing footprints will be much less than today's conventional takeoff and landing aircraft, thereby opening up design space for future aircraft carrier development. Unmanned Aircraft Naval aviation will employ UAVs for a variety of missions, beginning with reconnaissance, surveillance, and targeting, and later expanding to include such familiar aircraft carrier (CV) support tasks as tanking, electronic warfare (EW), antisubmarine warfare (ASW), and airborne early warning (AEW). Some of these unmanned aircraft will fly from aviation ships and surface combatants, whereas others, some possibly operated by the Air Force, may be based ashore at great distances from the supported battle group or expeditionary task force. As UAVs become more reliable and gain operational acceptance, unmanned tactical aircraft will be employed for selected lethal purposes, both air-to-air and ground attack. The panel believes that the introduction of unmanned tactical aircraft as substitutes for today's fighter and attack planes will be a slow ''fly-before-buy" process, and that a place will remain in the naval aviation arsenal for piloted tactical aircraft for many years to come. Aerial Trucks The introduction of subsonic, stealthy-when-required, aerial trucks is seen as a major positive development for the future. These aircraft—manned and unmanned—and employing STOVL, VTOL, and in many instances, STOL capabilities could constitute the backbone of naval aviation for the missions cited above. These workhorses would be mission configured using modular packages that could be changed in a reasonable time aboard ship and at advanced shore bases. Broadened Aircraft Basing Options Carrier Size Because of the trend toward a more vertical force of aircraft with attendant reduced demands for takeoff and landing deck space, the spectrum of acceptable
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms aircraft carrier sizes and configurations is broadened considerably. Seakeeping characteristics of aviation ships are also less constraining on STOVL and VTOL aircraft—and to some extent STOL—a fact that contributes to lowering the ship tonnage threshold below that for which safe air operations are now viable. Vertical aircraft also contribute to cost-effectiveness in other important ways—in sortie generation and the attendant quantity of munitions delivered on target. A ship with a vertical air wing can carry more such aircraft than conventional takeoff and landing (CTOL) aircraft and, for short to medium ranges, STOVLs and VTOLs can cycle at a greater rate. This adds up to more sorties and more ordnance delivered in a given period of time. Distribution of Air Assets The panel sees aircraft, some with considerable combat capability, being distributed more widely among ships of the fleet. Improved system reliabilities and the greater prevalence of vertical aircraft will make such distribution feasible in many instances, at least on a temporary basis, as dictated by the tactical situation. Flexible Carrier Deck Loads Although commanders have always been able to tailor the mix of aircraft types in a carrier air wing, force options of unusual flexibility will be open to the Navy in 2035 if the requisite enabling technologies are developed and exploited. For example, support aircraft functions—tanking, EW, ASW, AEW—could be provided by shore-based air platforms, the majority unmanned, that operate from airfields perhaps thousands of miles away and remain on station in support of battle groups for periods of two days or more. A CV in this instance could function as an all-fighter attack base and munitions magazine, greatly increasing the striking power of the all-fighter battle group. Alternatively, under a different tactical scenario, the carrier could serve principally as a support and/or reconnaissance and surveillance base, operating troop lift and logistics aircraft as well as special mission planes that provide reconnaissance and targeting support for expeditionary forces ashore and control long-range missiles launched by bombers and surface ships. TECHNOLOGY DEVELOPMENT PLAN The panel believes that a plan to develop future technologies for naval aviation should embrace the following elements: Make maximum use of technological advances in the commercial aviation sector, as well as advances developed by the Air Force, Army, and NASA.
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms Interservice cooperation has improved over the years, and the Navy has benefited considerably from R&D conducted by NASA and by the other military services. This policy should be continued and, indeed, information exchange and sharing, including joint technology planning and development, should be enhanced whenever possible. Navy R&D planners should seek to maintain and improve strong working relationships with NASA R&D planners to encourage recognition of Navy needs within NASA and to maximize the utilization of technology available from the relevant NASA programs. Continue the general course of Navy-funded R&D as outlined in current plans, but also maintain a healthy watch for the occasional nonessential pet projects that can creep in and soak up resources. By maintaining the current path, the Navy will be assured of having technologies in hand that facilitate evolutionary development of current air platforms should this course of action be chosen in the future; however, the panel believes that this course alone is inadequate to met the challenge of the future. Implement new, focused R&D thrusts in the following air platform technology areas, building on current progress within the Navy and in joint efforts with the Air Force, the Army, and NASA: Aerodynamics, Structures, Propulsion, Flight and mission control, Signature reduction, and Design and manufacturing processes. Technology Toolbox/Buffet Line The panel suggests that the Navy view its future R&D challenge as one of developing tools, including borrowing, wherever possible, those funded and developed by civil aviation, the Air Force, and the Army. These tools would then be placed in a toolbox ready to be used or presented on a technology buffet line. Thus, when the time comes to develop a tactical aircraft after the joint strike fighter (JSF) or a follow-on support aircraft, the Navy will have the option to pursue either a traditional evolutionary path or one that exploits the enabling technologies identified in this report, with the attendant new platform concepts identified by the panel. Key Enabling Technologies The panel identified 12 key enabling technologies (Table 3.1) that are uniquely applicable to naval aviation platforms and may be underemphasized within the Navy Department's current R&D portfolio. Investment by the Navy Department in the 12 enabling technologies that
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms TABLE 3.1 Key Enabling Technologies Technology Focus Area Key Enabling Technology Aerodynamics Laminar flow control High-lift aerodynamics Structures Lightweight, high-strength composites Propulsion Core engine performance Variable cycle engine Adapting large-engine technology to small engines Flight and mission control Integrated flight and propulsion control High-capacity, long-range data links Signature reduction RF signature reduction IR signature reduction Design and manufacturing processes Dynamic electronic prototyping Reduced-cost, low-rate production capitalize on and leverage the established aerospace R&D path could broaden the air platform and aircraft basing options for naval forces in the year 2035. By exploiting these enablers, and as success is demonstrated, those officials who set operational requirements and formulate acquisition programs will be afforded increased flexibility in fashioning designs of aircraft and aviation ships to meet future needs of the Navy and Marine Corps. These needs will embrace a wide mission spectrum in an era of rapid change in information technologies, increased reliance on precision-guided munitions, and demands for lower cost and possibly fewer aircraft and base ships. The panel believes that developing and deploying more cost-efficient air platforms and supporting sea bases are feasible and necessary goals. These aircraft and aviation ships will confer warfighting benefits that will be unattainable if R&D proceeds solely along the traditional path, wherein each aviation community (i.e., fighters, strike, reconnaissance, surveillance, ASW, EW, and troop lift) seeks a successor model possessing increased performance. The enabling technologies and their impact on future air platform designs are discussed in the context of the technology focus areas for future naval air platforms described below. Integrated High-Performance Turbine Engine Technology The Defense Department's very successful Integrated High-Performance Turbine Engine Technology (IHPTET) program, which was initiated in 1988 and will proceed in phases until 2003, constitutes an excellent model for a technology
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms development program. Its success is attributable to four crucial elements: (1) the subject is seen as important; (2) clearly defined technical and schedule goals are specified; (3) the effort is a government and industry partnership; and (4) stable funding profiles are established and adhered to. The panel believes very strongly that IHPTET should serve as the model for air platform technology development. TECHNOLOGY FOCUS AREAS Aerodynamics Laminar Flow Control The most significant air platform performance parameter for mission capability is range and, alternatively, endurance—both of which are major functions of cruise efficiency. From an aerodynamic perspective, this relates to low cruise drag. Current Situation and Constraints Many factors can dominate cruise drag: shape (or fineness), wing platform and aspect ratio, airfoil design, size, gaps and protuberances, surface roughness, engine inlets and nozzles, and control or trim surfaces. It is well known that a particular design to accomplish a specific mission is a compromise among mission elements such as maneuver performance, takeoff and landing performance (especially for sea-based air), and cruise performance. In addition, for fighter, attack, and reconnaissance aircraft, external stores are often used to increase payload and/or range at the expense of cruise drag. Many advances in technology have enabled refinement of aerodynamic shape for the basic platform as well as the external pylons and stores and their integration. Flight control technology has led to reductions in trim drag. Sophisticated analytical tools and design codes have facilitated optimum wing designs and inlet and nozzle integration based on dominant elements of the mission profile. As analytical tools continue to be refined, so does the understanding of flow phenomena, flow interactions, and drag. Computer-aided design tools facilitate moldline definition (and build) with unprecedented fidelity. New structural design techniques and composite structure process development are enablers for high-aspect-ratio wings to extend both the altitude and the endurance envelopes for special-purpose aircraft. These kinds of improvements are addressed almost daily and can be classified as business as usual from an aerodynamic perspective. There is, however, one particular aerodynamic technology with tremendous potential to improve cruise performance that is not business as usual. This is the area of laminar flow control.
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms FIGURE 3.1 Potential gains from laminar flow control. SOURCE: NASA Langley Research Center Web site at http://22.214.171.124/LFC_www/LFC.html. Key Enabling Technology Laminar flow control is a technique to control the boundary layer or the airflow closest to the skin. By maintaining laminar flow in the boundary layer and controlling the transition to turbulent flow, drag can be reduced significantly, buffet onset and flow separation can be delayed, and the flight envelope can be extended efficiently. Usually this is best accomplished by venting or bleeding the boundary layer via suction through a porous skin. An alternate technique is pulse blowing at frequencies tailored to unstable fluctuations in the location of boundary-layer transition. Interaction of the secondary flow with the primary airflow stabilizes the boundary layer and maintains laminar flow. Yet another technique, primarily useful at low Reynolds numbers, is to tailor the airfoil shape to maintain laminar flow. Figure 3.1, provided by NASA and based on work conducted at the NASA Langley Research Center and the Boeing Company, illustrates significant potential gains from the application of laminar flow control to both subsonic and supersonic flight. Fuel savings of the order of 10 to 20 percent can be realized for subsonic narrow-body transports, whereas fuel savings in excess of 20 percent are projected for wide-body transports with ranges greater than 4,000 nautical miles. Alternatively, research studies on high-speed flight indicate that supersonic cruise lift-to-drag ratios can be increased on the order of 10 percent at speeds of Mach 2.5, depending on the transition Reynolds number. The feasibility of these concepts has been demonstrated in both laboratory and flight research. For example, Figure 3.2 depicts one of the flight test vehicles, an F-16XL at the NASA Dryden Flight Research Center, that has been modified to conduct supersonic laminar flow control research. Close inspection of the port wing reveals the test panels in the enlarged glove area. Other flight
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms FIGURE 3.2 NASA laminar flow flight test vehicle at the Dryden Flight Research Center. SOURCE: NASA Langley Research Center Web site at http://126.96.36.199/LFC_www/LFC.html. test research has been conducted using a Boeing 757 for investigating laminar flow control in the subsonic regime. Recent accomplishments have been facilitated by a greater understanding of the flow phenomenology via development of CFD codes and breakthroughs in processing technology. Outstanding analytical and empirical correlation has been demonstrated for the F/A-18. Physical implementation of laminar flow control technology requires exacting external moldline (skin) definition, fabrication, preparation (hole location and size), and operation (vent flow control). As noted above, computer-aided design and manufacturing (CADAM) is a significant enabler in attaining the necessary fidelity for the moldline surface and for vent (port) locations. Control of the secondary flow through these vent holes is now feasible and manageable using advanced digital electronic controls and modern processing capabilities. Specific matching of the secondary flow management to the moldline shape and flight condition remains a challenge. These elements should be areas of continued Navy focus. However, much work remains to enable full integration into aircraft design.
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms Issues range from those associated with product definition in the laboratory to those associated with operational employment in the fleet. Analytical and experimental work to refine the moldline definition, vent hole distribution, and flow control based on specific design applications (fighter, support, surveillance) and platforms, wind tunnel validation of numerical codes, and the definition of robust scaling laws for naval air vehicle applications are all required before laminar flow technology is mature enough for full implementation. Operational issues include maintaining adequate bleed port operation (size and number of ports) and vent control, given the potential for surface contamination by rain, dirt, or salt spray. A range of solutions should be examined, including surface treatment, redundancy management for the ports, characterization of failure modes and effects, and maintenance and repair concepts. These efforts should not be conducted at the expense of pressing for continued progress in product definition, manufacturing, or flow control quality. Efforts should be coordinated with applicable work in contributing materials, structures, and manufacturing technology program elements. Other Contributing Technologies There is a distinct interaction between laminar flow control technology and several other technologies described in this report. Many of the wind tunnel and CFD tools used in laminar flow control R&D are applicable to high-lift aerodynamics issues as well. Large, complex unitized composite structures play a role in moldline and surface fidelity, and new processes enable very-high-aspect wing development. These have to be tied together from a Navy applications perspective for common support aircraft and UAVs. The variable cycle engine enables mission matching and may be valuable to offset traditional vent and bleed losses, depending on the specific breadth of Navy platforms and tailored mission applications. Integrated flight and propulsion control facilitates attainment of efficient trim conditions and integration of vent port flow control as a function of flight or maneuver envelope for all vehicles. Techniques to provide radio-frequency (RF) signature reduction will also reduce gaps and protuberances and should be considered when implementing laminar flow control methods in applications where stealth may be an issue, particularly for new-design fighter or attack aircraft and UAV applications. Dynamic electronic prototyping is an essential tool for evaluating particular designs, as are many of the tools used to facilitate reduced-cost, low-rate production. Potential Payoffs for Future Air Platforms Improved aerodynamic cruise performance has a first-order, fundamental effect on all aircraft design. Reduced drag and improved cruise efficiency provide design options to (1) increase endurance and operational altitudes for UAVs or
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms surveillance aircraft; (2) increase payload or range for the same size and weight platform in remaining naval air applications; or alternatively, (3) reduce platform size and weight with increased efficiency. All of this equates to decreased acquisition (size) and operational costs (fuel) for the life cycle of the vehicle. Recommendations To realize the potential offered by laminar flow control, several technology areas should be pursued to round out the fundamental understanding and provide for operational applications and transition: The Navy aerotechnology base should provide validated product definition and analysis tools, including shape, location, flow port patterns, and flow control. The Navy materials technology base should be tasked to provide coatings to prevent contamination and blockage of the secondary flow ports. Elements of the Naval Air Warfare Center (NAWC) and the Naval Air Systems Command (NAVAIR) should explore specific vehicle and mission applications. Research and development efforts on an integrated systems basis should provided parameters for control system development, critical operational (and failure) modes, and repair and maintenance techniques. These integrated efforts should extend to operational control and integration with variable cycle engine technology and should draw on advanced composite structures technology for characterization of new classes of air vehicles such as common support aircraft or surveillance UAVs. High-Life Aerodynamics One of the fundamental issues in carrier aviation is the ability to generate high lift at low speeds for takeoff (catapult) and landing (trap), particularly at maximum payload and bring-back weights typical of fighter or attack aircraft and fleet support carrier aviation. From an aviation safety perspective, lower approach speeds are desirable. Level 1 handling qualities at any approach speed are mandatory. Current Situation and Constraints Providing good high-lift capability for shipboard operation is a demanding task, particularly for modern supersonic jet aircraft. High-lift requirements for catapult and for approach or arrestment are different. Launch requirements typically are accompanied by lift and acceleration demands at heavy gross weights. For arrestment, maximum bring-back loads are important, but the requirements are to maintain a steady approach angle and altitude at low speeds through to arrestment. These high-lift requirements often introduce constraints and aircraft
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms design considerations that conflict with other mission design requirements. In particular, a wing optimized for high-speed flight should be very thin and highly swept, with little camber and twist. Low-speed aerodynamic efficiency, on the other hand, requires a relatively thick upswept wing, with high camber at the leading edge, preferably for full span. Many complex solutions have evolved over the years, including variable incidence (with respect to the fuselage) nose strut extension for catapult such as that used on the F-8; variable sweep as with the F-14; and numerous flap, slat, and slot arrangements on the wing's leading and trailing edges—some of them augmented by a complex active boundary layer control and blowing systems (e.g., the F-4). Increased flap area or deflection also has an effect on wing pylon and external stores integration (e.g., F/A-18) due to the physical clearances required for full flap conditions. Leading and trailing edge flaps are typically complex, have bulky drive systems creating external bumps, add significant weight to the airplane, and are a high-maintenance item. Often, developing excellent handling qualities for low-speed flight conditions is an exacting job because of the significant change in lift distribution and lift as a function of both airspeed and angle of attack. A fundamental issue is the ability to characterize the high-lift flow field, including repeatable flow through flap vents and slots, especially as it is affected by flow from the main wing or flow shed from the fuselage. Analytical tools for this complex flow field are not fully developed, yet this condition is fundamental to effective and safe CV operations. Researchers are gaining a greater understanding and appreciation of shed vortices from complex fuselage shapes, chines, or windscreen and canopy every day. Achieving a better understanding of high-lift aerodynamics and flow field interactions with and through deployed surfaces can provide a major breakthrough for simplification of wing design while maintaining repeatable low-speed handling qualities, high bring-back weights, and safe boarding rates. It is critical to maintain nonseparated flow over the deployed flap system. This requires further aerodynamic code development and an intense empirical interaction (i.e., wind tunnel test) for reduction to design practice. Figure 3.3 illustrates some of the outstanding problems that have yet to be solved. Key Enabling Technology Significant experimental work has been conducted in conjunction with the F/A-18 E/F program. Computer-aided design and analysis has enabled major progress for characterization of the high-lift flow field. An operable Reynolds-averaged Navier-Stokes turbulence model (both two dimensional and three dimensional) has been developed and validated to a large extent in wind tunnel tests. This has been facilitated by developments in processing capability and the ability to define a single three-dimensional solid geometry analytical and design data base for wing-flap-slot systems. Further, advanced test and flow field measurement techniques, such as a laser Doppler velocimeter, have been integrated
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms FIGURE 3.9 Bottom line results: benefits of design in manufacturing and assembly realized in the C-17 transport program. SOURCE: Courtesy of Wright Laboratory Manufacturing Technology Directorate, Wright Patterson AFB, Ohio. Other Contributing Technologies The above technology set interacts with several others in this report. Principal enablers exist via dynamic electronic modeling. Results of progress here affect virtually every element previously noted and have a direct interplay with the area of lightweight, high-strength composites. Potential Payoffs for Air Platforms Success in this area can have a first-order effect on force structure modernization through reduced cost of acquisition and ownership. Product quality and performance (weight) should also improve markedly. This may, indeed, be the single most important leverage for future defense systems, not only for air platforms but also across the board as the principles are applied. One prominent example is a newly redesigned C-17 horizontal tail, which has realized significant cost and weight reductions; see Figure 3.9. Recommendations Navy Man Tech efforts should emphasize the principle of reduced parts, tools, and fasteners in the development and manufacturing processes for both metallic and composite structures. Manufacturing process development should be conducted to extend high-speed machining from aluminum to hard metals
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms such as steel and titanium. Joining techniques, such as diffusion bonding and friction-stir welding, should be exploited to provide quality subassemblies and assemblies and to provide leverage for the use of near net shape casting and HIP forgings. Advanced casting and forming techniques should be exploited for repeatable large-part production, and should focus on producing near-net-shape parts to eliminate both material waste and machine time. Advanced tooling concepts should be explored in conjunction with the fabrication and assembly techniques noted here and in the discussion of composite structures. The guiding principles should be expandable-rate tooling (i.e., suitable for low rate, modified at some later point for increased rate) and reduced number of unique tools (via design for assembly and integrated manufacturing processes to obviate assembly steps, e.g., high-speed machine subassembly to eliminate sheet metal buildup). Integrated design and production efforts should be modeled, along with process cost, to allow cost-based decisions up to and including factory layout to reduce production cost and cycle time. SUMMARY OF ENABLING TECHNOLOGIES Table 3.2 lists the 12 key enabling technologies identified by the panel and indicates their impact on important air platform characteristics and costs. Aggressive development of these technologies will affect acquisition and life-cycle costs positively and in a major and fundamental way. Developing these technologies is essential to improving key aircraft design attributes such as cruise, takeoff, and landing performance and to enhancing combat survivability, particularly in subsonic speed regimes. Applications of Enabling Technologies These enabling technologies are applicable to manned and unmanned designs, and to conventional as well as various short or vertical takeoff and landing concepts. Further, they permit physical separation of command, targeting, sensor, weapons carriage, and weapons control functions from the platforms, air or surface, that perform the functions. Table 3.3 shows how these technologies affect the development of new concepts. Although these technologies also apply to the kinds of aircraft operating or being developed today, they were selected because they open up future aircraft and carrier platform options that are not otherwise attainable with current programs and R&D plans. Developing the proposed enabling technologies and exploiting the platform options thus opened up could move naval aviation, in the years ahead, in the following directions:
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms TABLE 3.2 Air Platform Characteristics and Costs: Impact of Enabling Technologies Enabling Technology Greater Endurance and Range Higher Thrust-to-Weight Ratio Lower Landing Speed Enhanced Survivability Less Development Time Reduced Acquisition Cost Lower Life-cycle Cost Laminar flow control X X X High-lift aerodynamics X Lightweight, high-strength composites X X X X X Core engine performance X X X X Variable cycle engine X X X X X Adapting large-engine technology to small engines X X X Integrated flight and propulsion control X X X X High-capacity, long-range data links X X RF signature reduction X X X IR signature reduction X X X Dynamic electronic prototyping X X X X Reduced-cost, low-rate production X X
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms TABLE 3.3 Aircraft and Air-Capable Ship Concepts: Application of Enabling Technologies Enabling Technolgy Subsonic Aerial ''Truck" STOL Enhanced VTOL Enhanced STOVL UAV Long Endurance UAV Sea-based Support UAV/Sea-based Strike Fighter Reduced Dependence on catapults and Arresting Gear Broadened range of Viable CV Sizes Increased CV Configuration Options CV/LHD Hybrid Laminar flow control X X High-lift aerodynamics X X X X X X X X Lightweight, high-strength composites X X X X X X X X X X X Core engine performance X X X X X X X X Variable cycle engine X X X X X X X Adapting large-engine technology to small engines X X X Integrated flight and propulsion control X X X X X X X X X High-capacity, long-range data links X X X X RF signature reduction X X X X IR signature reduction X X X X Dynamic electronic prototyping X X X X X X X Reduced-cost, low-rate production X X X X X X X
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms Systems that embody performance enhancements principally in air weapons and sensors instead of the platforms themselves. Subsonic aerial trucks as weapons carriers, target designators, and sensor platforms. Here, speed and maneuverability would no longer be principal design drivers. Also, the truck concept will facilitate improved cruise and endurance characteristics and make signature reduction more easily achievable and less costly. A more vertical force—VTOL, STOVL, and STOL. The mix of such platforms and CTOLs will be determined by the success of vertical designs in fleet operations and the size and configuration of future aviation ships. Widespread use of land- and sea-based UAVs for surveillance, reconnaissance, targeting, and a variety of support missions. UAVs for lethal purposes may follow. Reduced dependence on high-capacity catapults and arresting gear. A mix of aircraft carrier sizes. Fighter and Attack Missions Exploiting the enabling technologies will facilitate a shift in emphasis from an overfocus on platform performance to a focus on weapons, sensors, and communications. Thus, a fighter or attack aircraft in the future need not be a wholly self-contained system that can do everything on its own. Instead, it can serve as a de facto reusable intermediate stage of a broader weapons system in, for example, the role of weapons carrier, or solely as a sensor platform controlling missiles launched from ships, land sites, or arsenal airplanes. Such platforms also can be manned or unmanned. Subsonic Aerial Trucks The need for high-speed, very maneuverable, and, consequently, expensive air platforms would be minimized by substituting utilitarian subsonic trucks that incorporate modular mission change packages where sensible. These trucks may or may not have on-board sensors, depending on the mission. They could draw on tailored off-board information derived from long-endurance UAVs, satellites, Air Force platforms, national technical means, and other battle group assets. The aerial truck concept is also an attractive candidate for the several nonlethal support missions now flown by sea-based aircraft. The subsonic truck has the cost advantage of being less expensive to develop, manufacture, and operate than vehicles in today's high-speed fleet. Given improved laminar flow techniques and advances in engine efficiency, improved cruise and endurance performance is ensured. Placement of propulsion components is simplified, which in turn will facilitate the development of STOL vehicles and improvements in VTOL and STOVL designs. A shift to predominately subsonic air platforms also facilitates the achievement
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms of reduced RF and IR signatures in future designs. This is attributable to greater flexibility in airframe shaping, application of signature-reducing coatings, placement of engine inlet and exhaust ducts, placement and shaping of sensor and communications apertures, and in the instance of a weapons-only arsenal truck, elimination of radiation by sensors and communications. More Cost-efficient Systems The acquisition cost for future aircraft needed to carry out today's fighter and attack missions can be reduced by eliminating the high-speed flight requirement, no longer essential tactically or for survivability and employing advanced design and manufacturing processes. Operating costs will be lower because of the better aerodynamic cruise performance of new subsonic designs, as well as improvements in engine-specific fuel consumption. Combining these attributes with reliable and secure, high-capacity, long-range data links will yield a force that is less costly overall to procure and operate, on a dollars per target killed basis, than today's technology allows. Unmanned Aerial Vehicles UAVs offer obvious great potential benefits in surveillance, reconnaissance, and targeting, although these are only beginning to be demonstrated in the field. Additionally, UAVs promise reductions in aircrew manning and attendant training costs, as well as elimination of political risk associated with current manned aircraft reconnaissance missions and one-time punitive strikes in which downed aircrews are in danger of becoming hostages. Exploiting the enabling technologies will assist the Navy and Marine Corps to benefit from the kinds of concepts that spring from the high level of interest in UAVs by Congress and other DOD components. Long-endurance Systems Very long endurance or long-range UAVs that often can operate only from distant airfields, offer great promise to naval forces at sea despite their inability to fly from ships. Technical advances such as improved subsonic laminar flow; high-strength, low-weight composite airframes; improved propulsion efficiency; and reliable, secure, high-capacity data links over long distances give these systems their unusual performance and make operations in support of air and surface naval forces feasible. As an example, the Tier II+ High Altitude Endurance system, now being developed by DARPA, can fly 2,500 nautical miles to an operating area and remain on station for two days before returning to base, all the while providing area and spot data from synthetic aperture radars, moving target indicators, and
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms electro-optical and infrared sensors via satellite or direct line-of-sight downlink to naval commanders at sea and Marine Corps air-ground task forces ashore. Matters of ownership, tasking authority, flight control, payload control, and imagery access must be worked out, but integration into the Navy and Marine Corps of commercial data link and satellite technology will make possible full exploitation of the potential of very long-range or long-endurance UAV systems. Sea-based Systems The panel sees VTOL, STOVL, and STOL designs as the sea-based UAVs of choice, with VTOL solutions going beyond current rotary wing technologies such as the tilt rotor and conventional helicopter. Air vehicles with ability to take off and land vertically or in short distances make sense for naval applications because they can operate from flattop aviation ships and other surface vessels with smaller, partial helicopter-like flight decks. UVAs Permitting Offloading Functions By employing land- and sea-based UAVs for a variety of support missions—reconnaissance, surveillance, targeting, weapons control, EW, tanking, and long-range ASW and AEW—the flexibility of a naval task force at sea can be enhanced considerably. Commanders could offload certain support functions from carriers and amphibious aviation ships, thereby freeing flight and hangar deck space and turning these air-capable ships into all-strike or all-assault lift platforms. When naval forces operate at great distances from friendly airfields, the long-endurance UAV assures the commander of needed support while still permitting him to engage in high-intensity strike operations and ship-shore assault. Lethal UAVs Unmanned vehicles designed for lethal purposes are concepts to be explored as the enabling technologies mature, experience is gained in nonlethal applications, and trade studies help identify the most cost-efficient approaches. Such concepts range all the way from stealthy, loitering, long-endurance UAVs that dive into targets of opportunity to a highly capable air vehicle much like today's F/A-18 that is flown remotely by a pilot located in a command module on board a ship. In between these extremes might be a Tomahawk-like missile equipped with dynamic retasking capabilities and a large, possibly stealthy, subsonic aerial arsenal truck, described above, carrying weapons that can be launched on remote command.
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms Networked Warfare The Navy is currently leading development efforts in CEC as part of its air defense approach. The recent introduction of an airborne mode in the network will now enable ships best positioned to engage a threat to do so on the basis of tracking and fire control data contributed by other ships in the task group. At the present time the development effort in CEC is focused on integrating the air node into the network strictly as an airborne relay. The next step is to enable the air node to contribute fire control quality data to the net from its own on-board sensors, with a vision of eventually adding airborne shooters to the netted air defense capability. The panel believes that the current focus of netted warfare should be expanded to include offensive operations against surface targets by aircraft, submarines, and surface ships, with airborne sensor platforms—very likely UAVs—performing terminal guidance where necessary in a forward pass mode of operation. The netting of all warfare platforms by a common cooperative engagement architecture for both defensive and offensive combat operations would greatly expand the inherent warfighting capabilities of all platforms for littoral warfare, including support of Marine Corps forces ashore. Air platforms in particular would benefit greatly from the ability to employ off-board weapons. Aircraft size, weight, and cost could be greatly reduced since ordnance payload and carrier bring-back weights are design drivers in size and strength requirements and, consequently, in cost—including the cost of stealth. Support and Special-mission Aircraft Functions Challenge and Opportunity Perhaps the greatest potential for effecting beneficial change exists in providing the functions now resident in support and special mission aircraft. Mission categories include patrol, antisubmarine warfare, tanking, airborne early warning, surveillance, reconnaissance, electronic warfare, and logistics support. Some of these planes are not carrier capable and operate solely from shore bases; others, such as fixed-wing logistics aircraft, cycle to and from the fleet. However, significant numbers of support and special-mission planes are regular elements of the carrier air wing, constituting about 25 percent of the wing's complement. The functions they perform give the carrier battle group flexibility, including its ability to operate independently of other forces if required, an attribute much valued by senior commanders. However, this flexibility comes at a price. The support elements occupy 35 percent of available deck space aboard carriers, space that might be used to embark additional strike fighters. If the support functions can be offloaded but still remain available to the commander, the CV could be turned into a pure strike
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms ship. Here, it would serve as a refueling site and munitions magazine proximate to the target area, reloading and rapidly cycling fighter and attack aircraft. Battle group combat effectiveness would be enhanced, and the cost per target killed should be reduced. Commanders now have the option to change the mix of aircraft in an air wing and offload support aircraft. However, provisions must be made for the kinds of support these planes provide, support that is not available if the battle group is operating at a distance from friendly airfields. Hence, as a practical matter, creation of an all-attack carrier is not feasible today in many tactical situations. New Option—Off-board Support The enabling technologies that facilitate development of long-endurance or long-range UAVs, sea-based UAVs, and the aerial truck make possible offloading these functions to the degree desired. Support mission functions are naturals for unmanning, with very long-endurance or long-range UAVs that remain on station two days or more, constituting the backbone capability. The generally nonlethal nature of support functions also should facilitate early introduction of unmanned aircraft as current programs demonstrate reliability and UAVs therefore gain broader acceptance. Long-dwell surveillance or reconnaissance aircraft, with large-aperture antennas, would provide continuous tactical intelligence to both battle group and expeditionary force commanders without any necessity for sea-based flight operations. Also, naval expeditionary task forces without CV battle group support would benefit from improved situational awareness of their own and enemy forces without the interference to ship-shore lift operations that carrying organic reconnaissance platforms would induce. Patrol squadron (VP) could easily evolve into such a support force, becoming a shore-based element of the carrier's air wing. Sea-based manned and unmanned support aircraft could be positioned on ships other than CVs and LHDs. In concert with long-range systems operating from shore, this would reduce or eliminate flight deck congestion on both aviation ship types and would speed up turnaround of strike aircraft and troop life rotorcraft. Implications for Aircraft Carriers Introduction of new air platform concepts made feasible by development of the 12 key enabling technologies described above will have a profound effect on the design of future aircraft carriers and amphibious aviation ships. A more vertical aircraft complement broadens considerably the range of viable CV and LHD size options in the following ways: Nimitz size. New air platform concepts would enable a large CV to
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms generate significantly more sorties than can an air wing patterned after today's CTOL wing configuration. Sortie totals also can be increased dramatically by offloading support functions as noted above. The operational flexibility and economies of scale inherent in a large carrier likewise remain factors to be considered. Medium-tonnage CV. With a vertical air wing, a medium-tonnage carrier could generate sorties equivalent to today's Nimitz air wing. Small CV. Operating a vertical air wing reduces the tonnage threshold below which a carrier is considered nonviable. CV-LHD (amphibious assault ship) hybrid. A mission-flexible carrier suitable for littoral warfare might be possible. Depending on the task force mission, such a ship could embark strike fighter aircraft, Marine Corps lift and attack rotorcraft, or a mix of types. Since the next-generation aircraft envisioned by the panel can operate from aviation ships across a wide spectrum of sizes, this opens up the possibility of the Navy buying a high and low mix of aviation ships. These ships could include Nimitz-like CVs suitable for large-scale operations and smaller flattop aviation ships for less demanding situations. Payoff: A Potential Sea Change in Naval Aviation The benefits resulting from aggressively developing the key enabling technologies outlined in Table 3.3 will have a significant impact on both air platforms and their base ships, as summarized in Box 3.1. The Navy and Marine Corps have an opportunity to effect a sea change in the naval aviation of 2035 if the requisite technologies are developed and the platform options that spring from them are exploited. This force would differ materially from one that would result from the normal requirements and acquisition process; it would be different in character, composition, capability, flexibility, and cost. In turn, it would have a dramatic and positive overall impact on future naval forces. RECOMMENDATION The R&D path now being pursued by the Department of the Navy may limit its choices for air platforms that will follow on current development programs such as the Joint Strike Fighter program and a possible common support aircraft. Accordingly, the panel recommends that an air platform technology development plan be undertaken that comprises R&D funded by non-Navy entities, traditional Navy-funded programs centered on needs unique to the Sea Services, and most importantly, the 12 enabling technologies identified in this chapter, whose development should be vigorously pursued in IHPTET-like fashion. By doing so, Navy and Marine Corps leadership will have in hand a range of options on its technology buffet line when the time comes to develop platforms to enter operational status in the year 2035 and beyond.
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Technology for the United States Navy and Marine Corps, 2000–2035: Becoming a 21st-Century Force, Volume 6 Platforms BOX 3.1 Naval Aviation of the Future Moving toward a more vertical force—STOVL, VTOL, and STOL Subsonic aerial trucks as new, utilitarian naval air platforms Very long-endurance, long-range UAVs a principal naval forces asset High-quality surveillance, reconnaissance, and targeting information in real time Capability for offload of support aircraft from carriers More flexible carrier deck loading CVs as all-fighter or attack warfighters, or as Littoral warfare support ships with few or no VF or VA Broad range of viable aircraft carrier sizes and configurations Large CV to small CV with same aircraft types embarked Hybrid, multimission aviation ship (CV-LHD) as littoral warfare platform More cost-efficient force as a result of the following: Lower aircraft acquisition and life-cycle costs Greater aircraft deck loads per ship ton than today Increased CV sortie generation rates Efficiency of all-strike “arsenal” aircraft carrier Reduced manning due to more reliable systems, introduction of UAVs Lower training costs because of unmanning, less CV landing training for “vertical” air wing New air platform decisions necessary only as enabling technologies are proven
Representative terms from entire chapter: