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Background and Overview

INTRODUCTION

The history of warfare contains many examples of “measure-countermeasure” cycles in which one side develops a “leap ahead” capability that redefines the battlespace, whereupon the adversary is forced to expend significant resources to catch up and counter this new capability. In the late 1970s and early 1980s, the U.S. military was able to demonstrate and deploy innovative aircraft with reduced radar signature (stealth), giving it a significant advantage against air defenses of that period. In response, however, integrated and networked air defense systems have continued to improve, including longer-range early warning radar detection, computerized integration of radars, airborne interceptors, effective surface-to-air missiles, and defensive weapons with greater range, speed, tracking, and kill capability. These defensive improvements have threatened the survivability of conventional U.S. aircraft—that is, their capability to avoid or withstand a hostile man-made environment.1 This threat has led in turn to the development of onboard electronic countermeasures and weapons to attack enemy air defenses, as well as to recognition of the importance of having up-to-date knowledge of the location and capability of enemy assets in the battlespace (situation awareness). As enemy air defense capabilities continue

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Robert E. Ball, The Fundamentals of Aircraft Combat Survivability Analysis and Design, Second Edition, American Institute of Aeronautics and Astronautics Education Series, 2003.



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Future Air Force Needs for Survivability 1 Background and Overview INTRODUCTION The history of warfare contains many examples of “measure-countermeasure” cycles in which one side develops a “leap ahead” capability that redefines the battlespace, whereupon the adversary is forced to expend significant resources to catch up and counter this new capability. In the late 1970s and early 1980s, the U.S. military was able to demonstrate and deploy innovative aircraft with reduced radar signature (stealth), giving it a significant advantage against air defenses of that period. In response, however, integrated and networked air defense systems have continued to improve, including longer-range early warning radar detection, computerized integration of radars, airborne interceptors, effective surface-to-air missiles, and defensive weapons with greater range, speed, tracking, and kill capability. These defensive improvements have threatened the survivability of conventional U.S. aircraft—that is, their capability to avoid or withstand a hostile man-made environment.1 This threat has led in turn to the development of onboard electronic countermeasures and weapons to attack enemy air defenses, as well as to recognition of the importance of having up-to-date knowledge of the location and capability of enemy assets in the battlespace (situation awareness). As enemy air defense capabilities continue 1 Robert E. Ball, The Fundamentals of Aircraft Combat Survivability Analysis and Design, Second Edition, American Institute of Aeronautics and Astronautics Education Series, 2003.

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Future Air Force Needs for Survivability to improve in the future, U.S. aircraft technologies must also evolve so as to maintain the level of survivability necessary to accomplish missions that are deemed essential to the achievement of U.S. military objectives. Stealth technology is defined here as the technology that allows a weapons system and/or vehicle to be difficult to detect. In the case of a threat radar system, the radar return is reduced below the noise level or clutter. In this way, the weapons system gains advantages in surprise, time lines, and battle management. Such advantages are relevant for attacking entities from leopards to aircraft. Many speak of aircraft stealth as the key attribute of modern aircraft system mission success. It is very important, however, that one not think of stealth or speed or electronic countermeasures as ends in themselves, but rather in the context of the ultimate objective that these technologies provide—survivability, not only of the aircrew but of the system itself—so that both can live to fight another day. The many attributes (stealth, speed, situation awareness, tactics, and countermeasures) work synergistically so that the sum total of their contribution is mission success. To discuss how to ensure survivability in modern systems, it is necessary to go back in time. HISTORICAL CONTEXT World War I witnessed the advent of powered air warfare. In that conflict, airmen observed one another by relying totally on their natural vision and used their innate flying skills to achieve victory. Air warfare in World War II was characterized by the introduction of radar systems that saw beyond visual range and created for the first time in history an opportunity for long-range detection and tracking of hostile aircraft. The successful defense of Great Britain was to a great extent enabled not only by the resolute attitude of the English people in the face of repeated attacks and by the implausible strategic blunders of Adolph Hitler, but by the ability of the Royal Air Force to know where the enemy air forces were and how to employ its relatively meager air assets most efficiently to ensure their defeat. Electronic countermeasures also became a factor in the avoidance of German radar detection. Vietnam was the real crucible for the employment of weapons systems designed to attack militarily meaningful targets and penetrate enemy defenses protecting those targets. That conflict demonstrated the power of precision bombing to destroy critical targets such as bridges, and through increased effectiveness to reduce the number of sorties required and the

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Future Air Force Needs for Survivability attrition of attack aircraft. Enemy missile defense systems, especially the SA-2, had to be dealt with, along with Soviet-built fighters equipped with air-to-air missiles and greatly improved antiaircraft gun systems used for point defense. During and after the Vietnam conflict, Department of Defense air components absorbed lessons learned in that conflict and were developing new systems and tactics, doctrine, and operational concepts to cope with the rapidly improving Warsaw Pact conventional weapons capability led by the Soviet Union. The United States and the North Atlantic Treaty Organization (NATO) were preparing for major battles in two areas: central Europe and the North Atlantic and Norwegian Sea ocean basins. In the former, the Pact tactical air forces posed a major threat to NATO ground forces, aircraft, and air bases. In addition, the Pact, led by Soviet development and the fielding of the new air defense systems, was prepared to pose a major threat to NATO air forces should NATO counterattack Warsaw Pact ground forces and air bases. The United States and NATO developed capability to penetrate the Pact defenses by flying at low altitude (100 to 200 ft) while employing electronic countermeasures and lethal defense suppression. In order to achieve acceptable levels of survivability, the ratio of support aircraft to attack and close-air-support aircraft was high in some regions. Low-altitude operations impeded the ability to locate targets; thus, the USAF adopted the pop-up and roll-in maneuver performed as the target was approached. Still, to survive, the final approach to the target was limited to 10 to 20 seconds, which was marginally enough time for effective target acquisition and attack. It became very obvious, from the heavy air asset losses when attacking heavily defended targets in Vietnam and from the difficulties faced in central Europe planning, that a better way had to be found. It is pertinent to recount also the introduction of both reduced radar signature and high speed into U.S. reconnaissance aircraft. Following the missile intercept and destruction of the U-2 flown by Gary Powers over the Soviet Union, the A-12, YF-12, and SR-71 family was developed with a Mach 3+ capability (according to the press), along with shape features and materials to decrease the radar cross section. The speed, signature, and a high-altitude operation combined to make the aircraft quite survivable against ground air defenses as well as airborne interceptors. The MiG-25 Foxbat was the one aircraft most likely to attempt an intercept, and it did, but the intercept time window was only a few seconds, requiring precision command and control beyond Soviet capability.

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Future Air Force Needs for Survivability There is no reason to assume that evolution of integrated air defense systems, including defensive aircraft intercept, will not continue, or even accelerate, during the time horizon of this study (2018). Improvements in detection range, lethality, and system performance will challenge the United States to keep pace until the cumulative risk reduces the probability of mission success below an accepted threshold. In the past, the spectrum of possible warfare spanned extremes from actions against underdeveloped countries with dated defense systems to modern peer competitors with the latest equipment. Over time, however, the low end of the threat spectrum has been vastly improved by the acquisition of modern systems such that, if the necessity arises, U.S. forces must plan to face integrated air defense systems that will continue to be improved by evolution and possibly new concepts wherever these forces are employed. For this reason, the world of 2018 (and during the subsequent operational life of the aircraft—perhaps 40 or more years) presents a much more difficult and hostile operational environment than ever before. However, the United States has also continued working to keep pace. U.S. systems in use in 2018 and beyond must be able to complete their missions despite threat lethality evolution. Continued offensive mission success depends on improved situation awareness and low observables, increased speed, better system protection, and more capable weapons. Defense planning guidance demands that the Air Force be prepared to conduct its worldwide missions. To successfully accomplish these missions—Global Strike and Persistent Global Attack—serious consideration must be given to the quality of improved enemy air defense threats to ensure that analyses of alternatives result in systems that can accomplish the mission despite that expected threat. There is no need to recount in detail in this report the incredible success that has been demonstrated in recent conflicts by U.S. Air Force aircraft systems. We have all seen television footage of attacks in which not a single American aircraft has been lost despite fully functional and highly capable enemy air defenses. The question of this study, in its simplest form, is this: Can this nation continue to rely on these technologies to project power? This capability was not developed overnight. For example, there have been three generations of stealth technology from the 1970s until the present day.

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Future Air Force Needs for Survivability History of Stealth Early first-generation investigations emphasized materials and shape management to gauge their potential for improved aircraft survivability against known air defense systems and resulted in the first operational stealth aircraft—the F-117A. One penalty for stealth was lower aerodynamic performance as a result of the faceted shape. The second generation, that is, the B-2A, incorporated improved low-observable technologies, including curved shapes that were more favorable to aerodynamic performance and improved operational capability. The B-2A, however, presented maintenance cost challenges that helped to inspire the third generation. The third generation includes further improvements of all of the attributes, including operational performance, while at the same time reducing the acquisition cost penalty and maintenance cost burden. An example of a third-generation system is the F-22A. (In fact, because of its proven operational test performance, the USAF refers to it as a “fifth generation” fighter.) The Speed Factor Speed is also a contributor to survivability. Obviously, reduced exposure time affects defensive-system success. With the exception of the F-22 and the SR-71, all previous aircraft operate at subsonic speeds for most of their operational missions. Many earlier aircraft were capable of supersonic dash (beginning with the F-100), but the fuel consumption at supersonic speeds in afterburner was simply too high to sustain for more than a few minutes. The specific design of the SR-71 allowed it to perform its reconnaissance mission at very high altitude at a Mach number of 3+. The F-22, however, is the first U.S. aircraft that can operate efficiently at supersonic speeds without the use of afterburner; hence the term “supercruise” was created. Its speed performance contributes significantly to survivability. For very-high-speed systems such as current missiles, speed begins to be the dominant factor determining survivability, as stealth attributes are degraded owing to the severe thermodynamic and aerodynamic environment. Tomorrow’s aircraft systems must exploit the lessons of the past and provide the optimized systems and attributes that allow continued operations in enemy territory, with impunity, even beyond the time horizon of

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Future Air Force Needs for Survivability this study. These systems will not depend only on speed and stealth for enhanced survivability. They will also rely on better situation awareness, defensive systems, tactics, and weapons to ensure their mission survival. True systems-engineered designs become essential. Components of Survivability Robert E. Ball, Distinguished Professor Emeritus at the Naval Postgraduate School at Monterey, California, is considered a survivability expert by many who are involved in the field of designing aircraft systems that are expected to survive in combat environments. He has authored several books on the subject, and anyone interested in this field of science and design is encouraged to seek them out and read further on the subject. His books delve into the definition of survivability and provide information on the following: the aircraft survivability discipline, the anatomy of aircraft, missions and threats, and on the constituent elements of survivability—susceptibility and vulnerability. Susceptibility Ball defines survivability as the “capability of an aircraft to avoid or withstand a man-made hostile environment.”2 In the same reference, Ball defines susceptibility as “the inability of an aircraft to avoid the guns, approaching missiles, exploding warheads, air interceptors, radars, and all of the other elements of an enemy’s air defense …” and vulnerability as “the inability of an aircraft to withstand the man-made hostile environment.” Notice the fine distinction between the two. Susceptibility is framed in terms of what constitutes the hostile environment, while vulnerability is the ability to withstand those elements. Not to be susceptible is to avoid detection and interception through aircraft design and by characteristics that mitigate susceptibility, such as smokeless engines, low radar and infrared signatures, capable self-defense ordnance, and speed, and through the application of evasive tactics. 2 Robert E. Ball, The Fundamentals of Aircraft Combat Survivability Analysis and Design, Second Edition, American Institute of Aeronautics and Astronautics Education Series, 2003.

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Future Air Force Needs for Survivability Vulnerability Vulnerability, as distinct from susceptibility, is mainly in the hands of the aircraft designer and of structured assessment analyses used to determine how well an aircraft can resist damage in a hostile environment and keep on flying, through to successful mission accomplishment. The aircraft designer knows that resistance to enemy threats (reduced vulnerability) can be built into the system up to a point. Modern aircraft, by nature, are inherently fragile—tough enough to handle flight conditions of high speed and high G forces—but at the same time too thin-skinned to survive proximate lethal warhead effects. In some ways, design efforts to make them less susceptible to enemy efforts to destroy them make them more vulnerable if hit. Susceptibility relies on speed, stealth, and tactics. The best way to avoid problems is to develop mission profiles that avoid most threats. However, that is not always possible, thus demanding other methods to avoid aircraft damage or loss. It is important that methods to reduce aircraft vulnerability continue to be considered by the Air Force and its airframe contractors. Importance of Situation Awareness As usual in warfare, safety lies in the quality of intelligence gathered and provided to the aircrew regarding threat location and type. And then, once in the combat area, that safety lies in possessing outstanding situation awareness about all that is occurring—the presence of hostile and friendly aircraft, ground-based threat system activity status, missiles on the way, radars locked on, and many other indications that a pilot must know about and act upon. Modern systems have this ability, which is what separates them from their predecessors. Some, as in the case of the F-22, are capable of sustained supersonic speed that, when combined with stealth, tactics, and battlefield awareness, makes it very difficult for enemy air defense systems to prevent them from accomplishing their assigned missions. STATEMENT OF TASK In 2005, the U.S. Air Force asked the Air Force Studies Board of the National Research Council to conduct a study addressing the following five tasks:

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Future Air Force Needs for Survivability Review the current state-of-the art capability achievable in both stealth and speed for air vehicles (including unmanned systems) and missile systems as postulated by both Air Force and industry sources inclusive of, but not limited to, long-range strike options. Capture the various views from diverse sources on the effect of speed and stealth on the combat capability of these systems and provide a framework for evaluation. Provide an assessment of levels of survivability (provide committee definition) achievable by capitalizing on “speed-stealth” combinations within 15 years against current and future threats. Discuss the missions/capabilities enabled by greater stealth and/or speed for which no other more cost-effective alternative is obvious. Generally assess and discuss cost and schedule issues to obtain the associated speed-stealth technology and compare them to current R&D investment plans. It was understood that addressing these tasks in detail would require briefings and discussions held in a secure environment and that the Committee on Future Air Force Needs for Survivability would produce a nonpublic version of the final report. SCOPE AND COMMITTEE APPROACH Consistent with the priority expressed in Task 1, the committee focused on options for long-range strike: that is, a mission requiring the aircraft to have long range, penetrate alone and unsupported into heavily defended territory, deliver precision weapons onto fixed or moving targets, and return safely to base. The committee considered a range of threat air defense capabilities, as well as how these threats might evolve in the future. It discussed aircraft survivability in the context of defeating the threat’s kill chain (see Chapter 2) as it would apply to the Global Strike (GS) mission, and considered the sensitivity of survivability to speed, signature reduction, and situation awareness with regard to GS and persistent Intelligence, Surveillance, and Reconnaissance. The committee did not discuss whether the next-generation long-range strike system should be manned or unmanned, reasoning that the system design of an aircraft with the range, payload, speed, and defensive capabilities necessary for long-range strike would likely not be significantly affected by the presence or absence of a pilot.

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Future Air Force Needs for Survivability To address Task 2, the committee’s approach was to gather available information through briefings at its meetings (see Appendix B), as well as to review recent relevant studies authored by government agencies, federally funded R&D centers, and industry. The “survivability” of an air vehicle depends on many factors, including the type of mission; the quality and doctrine of enemy air defense systems; aircraft characteristics such as speed, stealth, range, payload, and maneuverability; situation awareness; countermeasures; electronic warfare; and weapons against threats, tactics, and so on. In the limited time available for this study, the committee was unable to consider all of these factors in detail; rather, the committee outlined a framework for a more formal, quantitative evaluation in Appendix C. To address Task 3, the committee drew upon the information gathered in Task 2 and used its own expertise to propose consensus combinations of speed and stealth that it believes would result in equivalent survivability levels in the long-range strike mission. Based on the expertise of individual committee members and drawing on their sponsoring organizations, the committee also assessed the technical feasibility of achieving the speed-stealth combinations mentioned above for an aircraft with initial operational capability (IOC) of 2018—a date that was agreed upon in discussions with the sponsor. Regarding Task 4, the committee did not have time to examine in detail the variety of missions and capabilities enabled by greater stealth and/or speed, nor to lay out and assess the cost-effectiveness of alternatives. However, the committee placed a premium on those technologies that would enable maximum versatility to accomplish a variety of missions with a single platform. These technologies are highlighted in the recommendations, as discussed in Chapter 5. In addressing Task 5, the committee did not have time to fully discuss cost and schedule issues associated with speed and stealth technologies, although implicit in the technical feasibility analysis conducted for Task 3 was the requirement that the technology be available for a 2018 IOC aircraft. The committee overlaid this feasibility analysis on its proposed consensus speed-stealth targets for survivability (Task 3) to identify gaps and needed changes in R&D investment plans, as called for in this task. The sponsor can use the committee’s conclusions and recommendations to evaluate the detailed cost and schedule implications of the changes to current R&D investment plans.

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Future Air Force Needs for Survivability STRUCTURE OF THIS REPORT Chapter 2 discusses the various missions that U.S. military aircraft may be called on to perform and the operational environment associated with those missions, including the types of threats that may be encountered. A general discussion of technologies needed for achieving various speed and radar signature combinations is included in Chapter 3, and the feasibility of achieving these advances for platform IOCs of 2018 is assessed. Research and development priorities for applications both near term (2018 IOC) and later (2025 IOC and beyond) are discussed. Chapter 4 describes the committee’s observations regarding aircraft stealth, speed, and survivability drawn from its analysis of relevant recently published reports, supplemented by briefings received by the committee and its own expertise in the field. It overlays the technical feasibility analysis of Chapter 3 on the proposed speed and stealth targets for aircraft survivability to highlight the gaps in current R&D investment plans. Appendix C, which is associated with Chapter 4, describes the variables (and interactions among the variables) that influence the survivability of mission aircraft and presents a formal framework that the Air Force can use to evaluate platform performance for various mission scenarios. Chapter 5 presents the committee’s overarching findings and recommendations regarding changes to current R&D investment programs that are needed to maximize the versatility of system performance.