A Primer on Survivability Requirement Fundamentals

by ENS Jake Hickman and Christopher Adams

U.S. Air Force Photo by Airman 1st Class Mikaela Smith

One of the most significant challenges the U.S. Department of Defense (DoD) faces today is the complex, time-consuming, and costly acquisitions process. In 2023, acquisitions alone accounted for nearly $160 billion, or almost 10% of the total DoD budget [1]. Furthermore, because of all the interdependent, interwoven, and contingent aspects involved, problems or mistakes that may originally seem small can often become exponentially expensive in terms of time and money before a system is fully acquired and fielded. It’s no wonder then that some have joked that perhaps the best way to defeat our military rivals would be to force them to adopt all the administrative requirements involved in acquiring a U.S. weapon system.

Survivability is, of course, just one of many themes that influence this acquisitions process. However, its importance, demonstrated by its significant contributions to the overall success of many weapon systems, is such that its associated requirements and processes deserve critical attention, analysis, and, where possible, enhancement. Accordingly, the focus of this article, as well as the more detailed thesis from which it is drawn [2], is centered on one small intersection of acquisitions and survivability—namely, the requirements for aircraft combat survivability (ACS).

In presenting this information, it is recognized that some readers may already be familiar with survivability and/or its applications, though not necessarily the acquisitions process. Others may work in, or otherwise be intimately acquainted with, acquisitions. Still others may be somewhere in the middle, having some knowledge and/or experience in both realms. Finally, some readers may be mostly strangers to all of these topics but, hopefully, interested in them from their standpoint as a stakeholder. It is thus hoped that the brief overview presented herein—which is intended to be more of an introduction to, rather than a comprehensive treatment of, the topic—will be beneficial to readers regardless of their background or experience and will facilitate further investment and investigation into this important issue.

THE ACQUISITIONS PUZZLE

The acquisitions process is made up of the three key DoD support systems: (1) the Planning, Programming, Budgeting, and Execution (PPBE) process; (2) the Defense Acquisition System (DAS); and (3) the Joint Capabilities Integration and Development System (JCIDS). Under the purview of the Joint Chiefs, JCIDS is the process of requirement writing and generation as funded by the PPBE process and managed by the DAS. While all three systems are concurrent and interwoven, JCIDS essentially develops requirements as enabled by funding from PPBE to meet chronological deadlines (called milestone [MS] decisions) as framed by the DAS (illustrated in Figure 1) [3].

Figure 1. The DAS Process.

Though the balance of these three is critical, we limit the majority of our attention here to JCIDS. According to the JCIDS Manual, a requirement is “a capability which is needed to meet an organization’s roles, functions, and missions in current or future operations to the greatest extent possible” [4]. In simpler words, a requirement is a capability to fill a gap, a solution to solve a problem, or a means to meet a need. Thus, it makes sense that JCIDS (the “C” of which stands for “capabilities”) is primarily concerned with the integration and development of requirements as solutions to problems. This integration/development begins with the identification of problems in need of solutions by a variety of means, one of which being the Joint Requirements Oversight Council (JROC) or potentially a Service chief or other stakeholder.

After identification, an appropriate solution is translated into a physical document. That initial documentation is then validated at a decision point, followed by the introduction of new information and ideas. From further investment and analysis, a new document emerges, which is similarly validated. This iterative process punctuated by validated documentation is the tangible effect of evolving requirements and corresponds to DAS milestones (Figure 1). This process continues until requirements are finalized in a contract with industry, becoming then the standard to which the contractors build and, finally, becoming the material solution to the initial capability gap.

Note that, for this discussion, the definition of a requirement is further refined to include only initial design considerations. Obviously, there may be “means to meet needs” discovered after a platform is in service (as is discussed more later), but pertinent survivability requirements must be original in design to the platform and not afterthoughts or retroactive addendums (as they’ve been for most of the last century). Additionally, the distinguishing feature of a survivability requirement is intuitively a capability to fill a survivability need in whatever form or fashion it may manifest. Typically, the solution to a survivability need is accomplished through survivability enhancement features (SEFs), as championed by long-time survivability professor Dr. Robert Ball in the (forthcoming) third edition of his ACS textbook [5].

A BRIEF HISTORY OF U.S. SURVIVABILITY REQUIREMENTS

So how did survivability requirements develop into their current position and importance in the acquisitions process? To answer this question, a brief history of U.S. military aviation is appropriate. If one permits retroactive addenda as survivability requirements (though, as previously mentioned, a true survivability requirement is proactive), then they have essentially existed since the dawn of aviation, even if not specifically enumerated or studied. In the earliest examples of aviation warfare before World War I (WWI), additional armor was tested and added to French planes under aviation pioneer Louis Bleriot. However, WWI would witness more than 115,000 aircraft-related casualties, demanding that more attention be paid to survivability [6]. The rise of commercial aviation would nonetheless claim the focus of aircraft design for the next several decades until the same mistakes were repeated in World War II (WWII), a similarly bloody conflict. Platforms such as the German Junkers J.1 in WWI and the American B-17 in WWII were retrofitted with more extensive armor, self-sealing fuel tanks, and added redundancy, though the lack of initial consideration still resulted in the loss of many lives.

Furthermore, our entrance into the Atomic Age at the end of WWII once again relegated survivability to a secondary priority as nuclear considerations became the focus of, and heavy influence on, aircraft design for the next two decades. It was not until the Southeast Asian (SEA) conflict and Vietnam that survivability requirements, at least as we understand them now, were afforded serious attention. As discussed in previous issues of this journal and elsewhere, much of the credit for the genesis of the ACS discipline goes to Mr. Dale Atkinson and his 1969 paper/presentation titled “Design of Fighter Aircraft for Combat Survivability” (see Figure 2) [7].

Figure 2. The Paper That Helped Start a Discipline.

The true history of survivability requirements is split into three phases, beginning in the middle of the 1960s and continuing to the present day. The first phase is defined by the previously mentioned primacy of survivability concerns in aircraft design. Several notable examples of this phase include the F-15 Eagle, arguably the first U.S. aircraft designed with survivability in mind; the UH-60 Black Hawk, recognized for unprecedented survivability in helicopters; and the A-10 Thunderbolt II, the most famously survivable U.S. aircraft.

In terms of requirements, the F-15 (shown in Figure 3) prioritized early in its program development survivability-enhancing characteristics such as the auxiliary power unit, soft-field landing gear, tail hook, drag chute, auto-pilot, self-sealing or foamed fuel tanks, armor, and bullet-proof glass. These characteristics were all justified at a weight and performance cost in the pursuit of survivability and operability. Likewise, the UH-60 (shown in Figure 4) enumerated survivability during combat and crash conditions as one of four categories in the earliest iterations of its requirement documentation. Out of this focus came the 30-minute requirement of operational capacity without lubricating oil, as well as many other key requirements and features. In addition, as detailed in the 2022 spring issue of this journal [8], the famed reputation of the A-10 (shown in Figure 5) for robustness and survivability is largely based on the program’s initial investment in, and prioritization of, survivability features.

Figure 3. The F-15 (U.S. Air Force Photo by Airman 1st Class Jason Couillard).

Figure 4. The UH-60 (U.S. Army Photo by Gertrud Zach).

Figure 5. The A-10 (Source: Tim Wing, Mecha Journal).

The second phase of survivability history is marked by the advent of stealth. Though some attention was previously paid to susceptibility reduction by means of camouflage, it was not until the latter part of the 20th century that advanced techniques for the discovery and tracking of aircraft were used, as well as attempts to reduce susceptibility. The first notable example in this pursuit is that of the SR-71 Blackbird, which was, in a word, fast. In fact, the entire concept of susceptibility reduction then hinged on this simple characteristic––the Blackbird was so fast that even when detected by an adversary, it was virtually impossible to shoot down. Lockheed’s investment in stealth technology evolved then into the F-117 Nighthawk (shown in Figure 6), which was not particularly fast but instead used a technique called faceting to drastically reduce the aircraft’s radar cross section (RCS) to achieve its relative “invisibility.”

Figure 6. The F-117 (U.S. Air Force Photo by Travis Burcham).

Conversely, Grumman took a different approach to stealth with its B-2 Spirit (shown in Figure 7). Rather than using faceting, the B-2’s design was centered around aerodynamic efficiency with innovative solutions for signature reduction and exhaust as well as more elegant shaping. (Stealth technologies have, of course, continued to evolve for subsequent U.S. aircraft, but many of them, as well as their associated survivability requirements, are beyond the classification level of this discussion.)

Figure 7. The B-2 (U.S. Air Force Graphic).

The third phase in the history of survivability requirements is the current age. Distinguishing these programs from previous examples is the integration of the primary consideration and stealth with many other features, such as tactics, new methodologies, and advanced electronic solutions. For example, the F-22 Raptor (shown in Figure 8) was influenced greatly by survivability concerns in early research and requirement writing, manifesting in its required supercruise capability [2], RCS reduction, advanced flight controls, maneuverability, radar detection range, and situational awareness. Likewise, the F-35 Joint Strike Fighter (JSF) (shown in Figure 9) has been one of the most complex and demanding programs in terms of requirements. With survivability representing one of the four pillars of the JSF program, the marked importance of these ideas was foundational throughout this complex requirements generation and iteration process, resulting in key performance parameters and other features that demonstrate significant investment in survivability.

Figure 8. The F-22 (U.S. Air Force Photo by MSgt. Andy Dunaway).

Figure 9. The F-35 (U.S. Marine Corps Photo by WO Bobby Yarbrough).

FUNDAMENTALS OF SURVIVABILITY REQUIREMENTS

Building on the many important lessons learned during the past half century of combat aircraft design, development, mission execution, and evaluation, several fundamentals associated with survivability requirements have emerged. These fundamentals were assembled by the authors based on DoD processes, the many lessons from past aircraft, and emergent work in the fields of acquisitions and survivability. Thus, Figure 10 is a new and emergent visual representation of our research, concisely articulating the process, tools, and content that comprise these fundamentals. Furthermore, the succeeding paragraphs briefly discuss these fundamentals, including important aspects of—or recommendations for—the requirements generation process, as well as the digital tools and content that inform it.

Figure 10. Fundamentals of Survivability Requirements (Source: Hickman).

The Process

As shown in Figure 10, there are two main pillars or characteristics that fundamentally support (or should support) the survivability requirements process: integration and iteration. In this complex process involving many stakeholders, competing, and overlapping timelines, large amounts of money, and technical complexity, integration is key to the efficient and effective cohesiveness of all the aforementioned facets. Not surprisingly, this integration is often accomplished primarily through effective, continuous communication, sharing information clearly, directly, and efficiently between different participants and stakeholders. Accordingly, for ideal integration to occur, one must have a good understanding of (1) one’s own position; (2) the motivations, dispositions, and goals of other stakeholders; and (3) how to best correlate the paths to shared goals.

Likewise, iteration is not just the redoing of something for the sake of redoing it. Rather, it is the intentional, deliberate, and, at times, painstaking process of reexamining ideas from a different perspective and/or with novel information. This step is clearly fundamental to requirements by the nature of the document validation process, which is iterative in the level of specificity and stage of the program reinforced by new research and information. Iteration also assumes a beginning and an end from which and to which to propagate. This beginning, as previously discussed, is the primary consideration and initial attention that delineate a design requirement from a retroactive addendum, the importance of which cannot be overemphasized.

The Tools

These pillars of the modern survivability requirements process, integration and iteration, are driven by a wide assortment of advanced design, collaboration, and computational tools. To try to name and detail the capabilities and status of all these tools would be beyond the scale and purpose of this discussion; however, the interested reader is encouraged to investigate them further in the aforementioned thesis [2], as well as throughout survivability-related literature (including many past issues of this journal, which are posted on the Joint Aircraft Survivability Program website [9]). For our purposes here, suffice it to say that the existence, intercompatibility, and ongoing enhancements of these tools—which are all tied together by the “digital thread” (another term for the overarching integration capability in the modern age) [10]—has opened the door to a vastly improved and optimized requirements process.

The Content

What then are the specific features or content of a well-written survivability requirement? Admittedly, there are numerous terms and characteristics that could be used to answer this question, but the following five general characteristics (as shown in Figure 9) are proposed:

Mission-conscious
Future-focused
Expertise-driven
Appropriately specified
Affordable.

First and foremost, a well-written requirement is only achieved by a thorough and meticulous definition of the problem (i.e., the capability gap). In other words, the concept of operations (CONOPS) has to be “bulletproof,” and the entire range of mission sets has to be considered in depth. Well-defined requirements spring from a well-defined purpose, mission, and use of a proposed aircraft. Before the requirements are written, then, the scope of the CONOPS must be explored in depth to avoid overexertion or overextension of resources for a capability that does not effectively address the gap for which it is intended.

Thus, requirements also need to be focused on the future, which includes a changing battlefield and the ongoing evolution of threats and technology. As we seek new offensive capabilities, we must simultaneously leverage that knowledge to enhance our defensive capability against the threats of both today and tomorrow.

Implicit in these first two characteristics is the third, for who can better (and more accurately) assess the early survivability concerns from a threat environment or the future demands of survivability than an actual expert in those fields? This concept may seem elemental, but the input of survivability experts, which is commonly (and unfortunately) overlooked, is truly fundamental to the development of effective survivability requirements. The input of expertise should extend all the way from the inception of the solution to the identified capability gap.

Proceeding from this thought is the fourth characteristic of a well-written requirement, an appropriate level of specification. While also encompassing the expected progression of requirements from broad to specific when approaching industry contracts, the point at which contracts are awarded requires appropriate specification. Here, a balance must be found between a requirement that is verifiable, testable, and concrete (to hold the contractor accountable) and one that has the leeway and trade space to allow for innovative solutions.

To illustrate some of these characteristics in practice, consider the following notional requirement examples. A stated requirement for an aircraft to achieve, say, “X% less vulnerability than the F-16” is far too broad; incorrectly implies there is a single figure defining the F-16; and is not testable, verifiable, or appropriate. Similarly, a requirement to, say, “separate all flight control systems” or “provide fire protection” would respectively beg the question of how far to separate and what really constitutes fire protection, as well as give contractors too much room to provide inadequate solutions.

An example of overspecification would be to prescribe an exact system from a certain manufacturer in a certain configuration and location with no option or trade space. On the other hand, to state that “the vulnerability against X missile characterized by Y-grain fragments impacting at Z ft/s with said density of Q shall be <W in said scenario” is appropriate in that it outlines an objective, testable figure in a well-defined scenario from a mission set without prescribing the exact solution or methodology to accomplish the goal. Furthermore, a detailed requirement such as this would also clearly be driven by subject-matter expertise. Similarly, including “shall have” verbiage in a requirement such as “the XX aircraft shall have a dry bay fire suppression system under fuel tanks X-X” would ensure a clearly evident solution, providing sufficient detail without handcuffing design engineers.

Finally, our fifth content characteristic of a well-written requirement is the necessity of affordable solutions. While itself meriting mention, this “elephant in the room” is addressed last to allow for the exploration of other critical ideas that tend to find themselves relegated due to the all-consuming nature of affordability.

CONCLUSION

Just as the costs, complexities, and challenges of developing new U.S. combat aircraft continue to rise, so too does the importance of having good survivability requirements, processes, and tools in our acquisitions process. Thus, whether one is a survivability practitioner, acquisitions specialist, or associated stakeholder, it is hoped that this brief overview of the history and fundamentals of U.S. survivability requirements will help the reader to better understand, assess, organize, and ultimately connect the pieces of the acquisitions puzzle.

About the Authors

ENS Jake Hickman is a student naval aviator in training at Naval Air Station Pensacola. He holds a B.S. in aerospace engineering from Auburn University, commissioning out of the ROTC program in 2022. He also holds a master’s in aerospace engineering from the Naval Postgraduate School (NPS), where his thesis focused on survivability requirements for aircraft.

Mr. Christopher Adams is a Senior Lecturer at the NPS Department of Mechanical and Astronautical Engineering and is a former Associate Dean of NPS’s Graduate School of Engineering and Applied Sciences. A retired Navy Commander and aviator with multiple tours in Iraq and Afghanistan, he is a widely recognized subject-matter expert and educator on combat survivability. Mr. Adams holds a bachelor’s degree and master’s degree in aerospace engineering from Boston University and NPS, respectively.

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