2

Advanced Test Facilities Planning

The purpose of this study is to facilitate the creation of a master plan and strategy for the direction of the Arnold Engineering Development Center (AEDC), with special emphasis on the acquisition of new capabilities or facilities. The initial master plan was furnished by the vision of General Henry A. Arnold and Dr. Theodore von Karman, who recognized the significance of realistic ground testing as one of the key tools of the aerospace systems development process.

The philosophy regarding the justification for building ground test facilities has changed over the history of AEDC. Figure 1-1 shows that the majority of the primary facilities at AEDC were in service by 1966, more than 25 years ago. The resulting total array of facilities at AEDC (valued by AEDC at $3.64 billion to replace) has made available to the aerospace development community test facilities possessing unsurpassed or unique environmental simulation fidelity. This attests to the momentum initially imparted by General Arnold and Dr. von Karman, but it raises questions about what has happened in recent times.

In the beginning, for example, design work on the large transonic (16T) and supersonic (16S) wind tunnels began even before supersonic aircraft were designed. In fact, one of the most powerful motivations for the construction of these wind tunnels was the belief that mastering transonic and supersonic flight was absolutely essential to national interests. A direct result of this reasoning is that 16T and 16S were deliberately designed to have capabilities well beyond the needs of that moment. This explains why they have been in demand almost from the outset.

The philosophy behind the wind tunnel construction can be contrasted with that of the last primary AEDC facility to enter service, the Aero-Propulsion Systems Test Facility (ASTF). Designed for testing aircraft engines, the ASTF was authorized only after it was abundantly clear that it was needed. To begin with, virtually every military aircraft engine developed in the 1960s and early 1970s had experienced operational or durability problems after reaching the field. These problems were costly to solve because the engines were already in high-rate production. However, they could have been detected and corrected prior to field introduction with proper ground testing. Furthermore, existing transport aircraft engines had become so large that no facility was able to test them at the operating points most critical to fuel consumption--namely, their cruise conditions--and much bigger engines were on the way. The final rationale for construction was that aircraft engine testing facilities equivalent to those already at AEDC could



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Future Aerospace Ground Test Facility Requirements for the Arnold Engineering Development Center 2 Advanced Test Facilities Planning The purpose of this study is to facilitate the creation of a master plan and strategy for the direction of the Arnold Engineering Development Center (AEDC), with special emphasis on the acquisition of new capabilities or facilities. The initial master plan was furnished by the vision of General Henry A. Arnold and Dr. Theodore von Karman, who recognized the significance of realistic ground testing as one of the key tools of the aerospace systems development process. The philosophy regarding the justification for building ground test facilities has changed over the history of AEDC. Figure 1-1 shows that the majority of the primary facilities at AEDC were in service by 1966, more than 25 years ago. The resulting total array of facilities at AEDC (valued by AEDC at $3.64 billion to replace) has made available to the aerospace development community test facilities possessing unsurpassed or unique environmental simulation fidelity. This attests to the momentum initially imparted by General Arnold and Dr. von Karman, but it raises questions about what has happened in recent times. In the beginning, for example, design work on the large transonic (16T) and supersonic (16S) wind tunnels began even before supersonic aircraft were designed. In fact, one of the most powerful motivations for the construction of these wind tunnels was the belief that mastering transonic and supersonic flight was absolutely essential to national interests. A direct result of this reasoning is that 16T and 16S were deliberately designed to have capabilities well beyond the needs of that moment. This explains why they have been in demand almost from the outset. The philosophy behind the wind tunnel construction can be contrasted with that of the last primary AEDC facility to enter service, the Aero-Propulsion Systems Test Facility (ASTF). Designed for testing aircraft engines, the ASTF was authorized only after it was abundantly clear that it was needed. To begin with, virtually every military aircraft engine developed in the 1960s and early 1970s had experienced operational or durability problems after reaching the field. These problems were costly to solve because the engines were already in high-rate production. However, they could have been detected and corrected prior to field introduction with proper ground testing. Furthermore, existing transport aircraft engines had become so large that no facility was able to test them at the operating points most critical to fuel consumption--namely, their cruise conditions--and much bigger engines were on the way. The final rationale for construction was that aircraft engine testing facilities equivalent to those already at AEDC could

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Future Aerospace Ground Test Facility Requirements for the Arnold Engineering Development Center be found elsewhere in the free world, and larger ones were known to exist in the U.S.S.R., so that the United States was far from preeminent in this vital field. This type of reactive planning is particularly unsuitable to major ground test facilities, which usually require at least 10 years to design, build, shake down, and calibrate. The situation will be further aggravated if the technology necessary to allow the design of the ground test facility is not in hand and must first be developed through research or pilot plants before the design cycle can begin. Because major aerospace systems require about 10 years of ground testing before they are ready for production, test facility planning must be proactive and must precede initial operational capability by more than 20 years. In Chapter 3, several detailed examples can be found of aerospace systems that will require new development ground test capabilities. They encompass a wide spectrum of promising evolutionary and revolutionary future aerospace systems, such as subsonic and supersonic aircraft, hypersonic aerospacecraft, and spacecraft. These new systems will need entirely new ground test facilities or significant improvements to existing facilities. Little is being done to prepare for these new horizons even though they are already in sight. The present situation can therefore be summarized as follows: The vision of General Arnold and Dr. von Karman was correct and is still sound guidance for the conduct of the nation's technological affairs. It seems especially relevant as the Cold War ends. As far as AEDC facilities are concerned, the vision that created them has not been sustained. Ground testing capabilities lag rather than lead the known needs, and the gap is growing. The present planning process in the U.S. Air Force does not deal adequately with this situation. Indeed, if it did, there would have been much less reason for this study. This situation is likely to intensify with time for several reasons. First, the pace of technological development is being accelerated by the rapidly increasing power of computers and the purposes to which they are put, such as computational fluid dynamics (CFD) and data reduction, the discovery and perfection of radically improved aerospace materials, the introduction of new manufacturing processes and devices, and the practical application of such modern devices as the laser. Second, the roles of ground testing, flight testing, and CFD during both research and development have grown more interdependent and complex, and must be carefully sculpted to suit each program. Third, no matter how exotic the aerospace system, some form of realistic ground testing will always be required as the final “proof” or “qualification ” that the desired performance, reliability, and durability of the product have been achieved. This situation has been brought to the forefront by the revolutionary National Aero-Space Plane program and its derivatives, which will take air-breathing flight to frontiers well beyond the existing boundaries. Neither the facilities, computational methods, nor relevant experience exists across the complete speed range for hypersonic, transatmospheric, or cruise vehicles. As a result, the development of these vehicles will enlist a different mix of these tools than did their

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Future Aerospace Ground Test Facility Requirements for the Arnold Engineering Development Center predecessors. Unfortunately, determination of this mix has become an additional part of the work, rather than having been planned in advance. Thus, the ground testing requirements of future aerospace systems must be thoughtfully considered by all involved parties, and steps should be taken early enough to ensure that a disciplined development process is possible. We refer to this surrogate for “vision” as a structured planning process and believe that the gated roadmaps it can produce are essential to leadership in aerospace development. With the foregoing in mind, and recognizing that these rapidly changing times also present special opportunities for creative problem solving, we now describe several dimensions of a candidate structured planning process that forms the basis for further action. The new U.S. Air Force Materiel Command (AFMC) should establish a Long-Range Planning Team (LRPT) that can emulate the procedure that created AEDC. The AFMC is the ideal location for this planning activity because it combines the work of the Air Force Systems Command (AFSC) and Logistics Command (AFLC) and will, therefore, be responsible for all U.S. Air Force aerospace systems from initial concept through development and logistic support, and because the development and service ground testing at AEDC is important in joining the functions of the AFSC and the AFLC. To this LRPT, the operating Air Force commands and their civil or commercial counterparts will bring their current experience and their vision of future tasks and systems. The Air Force laboratories and test centers, as well as the Navy, National Aeronautics and Space Administration (NASA), Department of Energy, and other government organizations will bring their vision of how emerging technologies can contribute to these or other systems. Congressional support will also be valuable and essential. The leadership of the LRPT should include civilians for continuity and military personnel for their operational perspective. It should also include resident experts in the likely fields of interest, such as subsonic and supersonic aircraft, hypersonic aerospacecraft, space launch systems, spacecraft, and weapons. It should routinely utilize technical expertise from other services, NASA, industry, and universities in the form of standing boards and special invitations. A conceptual diagram of the proposed structured planning process is given in Figure 2-1. Only a few of the many important feedback loops in action are shown. This figure represents the elements discussed above and is meant to emphasize the fact that the “customers” are the future aerospace systems options under consideration. The foremost objective of the planning will be to coordinate all possible participants of future prospective systems and initial actions, rather than to define new aerospace systems in complete detail. This could be in the form of gated roadmaps that address with forethought and realism the evolution of the technologies and related facilities that will be involved. We consider the early definition of required ground test facilities and their funding plans to be critical. This planning can and must precede by several years the issuance of system development contracts. The new long-range planning process should also provide initial answers to a number of closely related questions for the aerospace system under study. These would include, for example, the expected relationship among ground testing, flight testing, and CFD and, in particular, the methodology that will be used to clear the initial vehicle for flight and qualify the final version for serial production. Also, when adequate ground test facility technology is not available, a plan must be provided that includes research and pilot facilities.

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Future Aerospace Ground Test Facility Requirements for the Arnold Engineering Development Center FIGURE 2-1 Committee concept of the structure of the proposed planning process.

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Future Aerospace Ground Test Facility Requirements for the Arnold Engineering Development Center The committee, mindful of today's tightening budgets, believes that this structured planning process will lead to more deliberate and rational spending. This process will avoid situations in which major facility requirements are almost an afterthought to the decision to establish a new program. The consequences of the latter can range from decisions that lack an adequate data base to the unanticipated use of program resources on a crash basis to provide missing ground test facility capabilities. This process also should provide continuous review and modification of AEDC test funding rules so that they are mutually beneficial to all parties concerned and make possible the best use on behalf of the nation of the current and future facility investments. Although this proposal may appear to go beyond the statement of task of this committee, it is necessary if one is to respond to the implied questions found there. One cannot author a “guide for planning and modernizing AEDC facilities” without being able to visualize the environment in which AEDC exists. This proposal offers many benefits for the entire systems planning process, but it is essential for the maintenance of adequate national testing capabilities and for the most rational use of AEDC. The committee recommends that the AFMC augment present system-planning activities by creating a Long-Range Planning Team to be responsible for a structured preplanning process that contributes to the broader planning leading to new Air Force aerospace systems. The LRPT should examine all options and alternatives under consideration and concern itself with system technology requirements, test capabilities required, and the roles of the various developmental tools for those options. Strong participation in the LRPT by AEDC and the earliest possible identification of required development ground test facilities and their funding plans are critical.