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NASA Aeronautics Research: An Assessment (2008)

Chapter: 2 Challenges and Requirements for NASA Aeronautics Research

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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
×
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
×
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
×
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
×
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
×
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Suggested Citation:"2 Challenges and Requirements for NASA Aeronautics Research." National Research Council. 2008. NASA Aeronautics Research: An Assessment. Washington, DC: The National Academies Press. doi: 10.17226/12182.
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Page 64

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

2 Challenges and Requirements for NASA Aeronautics Research This chapter evaluates how well each of NASA’s 10 aeronautics research projects supports the 51 highest-priority research and technology (R&T) challenges from the Decadal Survey of Civil Aeronau- tics (NRC, 2006) and NASA’s own requirements for aeronautics research and the needs of other federal government departments and agencies for non-civil aeronautics research. The chapter also evaluates NASA’s response to the eight overall recommendations that are contained in the Decadal Survey. The evaluations of the 51 highest-priority R&T challenges are grouped according to the five areas from the Decadal Survey: • Aerodynamics and Aeroacoustics • Propulsion and Power • Materials and Structures • Dynamics, Navigation, and Control, and Avionics • Intelligent and Autonomous Systems, Operations and Decision Making, Human Integrated Sys- tems, and Networking and Communications Appendixes A through E of the Decadal Survey of Civil Aeronautics contain lists of milestones for all of the challenges examined in the survey. The assessment of each R&T challenge below includes a list of the milestones established for that challenge. The purpose of this listing is to indicate the nature of the work that the Decadal Survey included within each challenge. However, the list of milestones for each challenge does not in all cases describe the complete scope of the challenge, as detailed in the Decadal Survey of Civil Aeronautics. This chapter’s evaluation of how well each of NASA’s 10 aeronautics research projects supports the 51 highest-priority R&T challenges from the Decadal Survey is summarized in Tables 2-1 and 2-2. Each cell of Table 2-1 is color-coded with green, yellow, black, or white, as follows: • Green: The project substantially meets relevant aspects of the intent of the R&T challenge and will substantively advance the state of the art, with no significant shortcomings. 20

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 21 TABLE 2-1  Summary of How Well NASA’s Aeronautics Research Supports the 51 Highest-Priority Research and Technology (R&T) Challenges from the Decadal Survey of Civil Aeronautics l tro k t. on ec gm C D Green = no significant shortcomings y M ft ilit ht ra lth lig ab rc Yellow = minor shortcomings ea ce tF g l ur Ai ta g in H pa D in or en nt W e W d irp irs Black = major shortcomings i lie lli g cl an y ar d -A -A hi es te xe Ve ft ot M M In en s s R ra w White = not relevant ck Fi R ic ic AT AT lo rc ed ed ed re n on la ic ic el ARMD --> so Ai S S lG n n at at at lB rs lY so so AT AT er gr gr gr g e ta ta Projects in ta b b p yp te te te G G Su Su Su Ag To To To In In In H N ARMD --> Fundamental N Airspace Aviation Grade Summary Titles of R&T Challenges Programs Aeronautics Program Sys. Prog. Safety Program by Challenge (Some are abbreviated; see Table 1-1 for full titles.) R&T Challenges in the Aerodynamics and Aeroacoustics Area A1 GG Y B 1 1 1 A1. Novel propulsion-airframe integration A2 GG B GG Y 2 1 1 A2. Transition, boundary layer, and separation control A3 GG B B 1 2 A3. High performance and/or flexible multi-mission aircraft A4a GG GG GG 3 A4a. Reduce aircraft and rotor noise A4b GG Y GG Y 2 2 A4b. Prediction of performance of complex 3D configurations a A6 GG Y 1 1 A6. Aerodynamics robust to atmospheric disturbances A7a B 1 A7a. Leverage advantages of formation flying A7b B Y GG B 1 1 2 A7b. Wake vortex prediction, detection, and mitigation A9 Y B 1 1 A9. V/STOL and ESTOL, including adequate control power A10 Y 1 A10. Reducing/mitigating sonic boom (novel aircraft shaping) A11 GG Y Y Y 1 3 A11. Robust and efficient multidisciplinary design tools R&T Challenges in the Propulsion and Power Area B1a GG Y GG 2 1 B1a. Quiet propulsion systems B1b Y Y 2 B2. Ultraclean gas turbine combustors B3 B Y B Y 2 2 B3. Intelligent engines and mechanical power systems B4 Y Y B 2 1 B4. Improved propulsion system fuel economy B5 B Y 1 1 B5. Propulsion systems for short takeoff and vertical lift B6a Y Y 2 B6a. Variable-cycle engines to expand the operating envelope B6b B B B B 4 B6b. Integrated power and thermal management systems B8 B 1 B8. Propulsion systems for supersonic flight B9 B B B B 4 B9. Advanced aircraft electric power systems B10 GG 1 B10. Combined-cycle hypersonic propulsion systems R&T Challenges in the Materials and Structures Area C1 B GG Y 1 1 1 C1. Integrated vehicle health management C2 Y B B 1 2 C2. Adaptive materials and morphing structures C3 GG Y GG Y B 2 2 1 C3. Multidisciplinary analysis, design, and optimization C4 Y B GG Y 1 2 1 C4. Next-generation polymers and composites C5 Y GG B 1 1 1 C5. Noise prediction and suppression C6a B GG Y B Y 1 2 2 C6a. Innovative high-temperature metals and environmental coatings C6b GG GG Y B 2 1 1 C6b. Innovative load suppression, and vibration and stability control C8 Y 1 C8. Structural innovations for high-speed rotorcraft C9 Y Y Y Y Y 5 C9. High-temperature ceramics and coatings C10 Y B B B Y 2 3 C10. Multifunctional materials R&T Challenges in the Dynamics, Navigation, and Control, and Avionics Area D1 Y B B Y D1. Advanced guidance systems 2 2 D2 B GG Y GG D2. Distributed decision making and flight path planning 2 1 1 D3 B YB D3. Aerodynamics and vehicle dynamics via closed-loop flow control 1 2 D4 Y GG 1 D4. Intelligent and adaptive flight control techniques 1 D5 B GG Y GG 2 1 D5. Fault tolerant and integrated vehicle health management systems 1 D6 B B Y 2 D6. Improved onboard weather systems and tools 1 D7 B B B B 4 D7. Advanced communication, navigation, and surveillance technology D8 B GG GG GG 3 1 D8. Human-machine integration D9 GG 1 D9. Synthetic and enhanced vision systems D10 B B B 3 D10. Safe operation of unmanned air vehicles in the national airspace R&T Challenges in the Intelligent and Autonomous Systems, Operations and Decision Making, Human Integrated Systems, Networking and Communications Area E1 GG Y Y Y 1 3 E1. Design and evaluate complex interactive systems E2 Y Y 2 E2. Separating, spacing, and sequencing aircraft E3 Y Y 2 E3. Roles of humans and automated systems for separation assurance E4 B B 2 E4. Sensors, etc. to predict and measure wake turbulence E5 GG Y 1 1 E5. Information sharing among human and machine agents E6 B Y 1 1 E6. Vulnerability analysis in the design of the air transportation system E7 Y Y 2 E7. Adaptive ATM techniques to minimize the impact of weather E8a GG GG 2 E8a. Transparent and collaborative decision support systems E8b GG Y 1 1 E8b. Operational and maintenance data to assess safety E8c GG B 1 1 E8c. Human operators in effective task and attention management Totals for All 51 R&T Challenges from the Decadal Survey Green 10 4 6 1 7 2 3 3 2 0 38 a Yellow 9 13 9 5 3 7 3 3 1 5 58 Work on R&T Challenge A6 related to subsonic fixed wing Black 8 14 9 5 6 7 2 0 1 1 53 aircraft is being done by the NASA Office of Safety.

22 NASA AERONAUTICS RESEARCH—AN ASSESSMENT TABLE 2-2  Grade Summary for the 51 Highest-Priority R&T Challenges in the Decadal Survey of Civil Aeronautics, by Area Report Area Green Yellow Black Area A 12 11  8 Aerodynamics and Aeroacoustics Area B  3 10 13 Propulsion and Power Area C  8 18 12 Materials and Structures Area D  9  7 16 Dynamics, Navigation, and Control, and Avionics Area E  6 12  4 Intelligent and Autonomous Systems, Operations and Decision Making, Human Integrated Systems, and Networking and Communications Total 38 58 53 • Yellow: The project contains minor shortcomings, which are recoverable within the current overall project concept, such as the following: —  esearch described in the NASA task, if successful, would satisfy most, but not all, of the R relevant aspects of the Decadal Survey R&T challenge (e.g., the task would make only moder- ate advances in the state of the art of relevant technologies, though the results would still be significant). — Research described in the NASA task, if successful, may not make a significant difference in a time frame of interest to users of the research results (e.g., because the level of effort is too low, or a different and more viable research approach should be selected, or some of the task is devoted to research goals inconsistent with the Decadal Survey R&T challenges, the aero- nautics research requirements of NASA, and other federal government department or agency non-civil aeronautics research needs). • Black: The project contains major shortcomings, which would be difficult to recover from within the current overall project concept, such as the following: — Research described in the NASA task, if successful, would make little or no progress in satis- fying the Decadal Survey R&T challenge (e.g., the task would not make a significant advance in the state of the art of relevant technologies or the effort is meager compared to what is needed). — Research described in the NASA task, if successful, would be highly unlikely to make a sig- nificant difference in a time frame of interest to users of the research results (e.g., because the level of effort is too low, or a different and more viable research approach should be selected, or most of the task is devoted to research goals inconsistent with the Decadal Survey R&T challenges, the aeronautics research requirements of NASA, and other federal government department or agency non-civil aeronautics research needs). — The Decadal Survey R&T challenge is relevant to the NASA project, but the project is doing no related research. • White (or blank): The R&T challenge is not relevant to the project. As detailed in the discussion of individual challenges below, in a few cases yellow or black grades indicate that research plans developed by the Aeronautics Research Mission Directorate (ARMD) are poorly conceived and that the resulting research will likely be ineffective. In most cases, however, yellow

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 23 or black grades reflect inconsistencies between NASA project plans and the Decadal Survey. These inconsistencies are generally the result of NASA choosing to do little or no work in a particular task area and/or selecting research goals that fall short of advancing the state of the art far enough and with enough urgency either to make a substantial difference in meeting individual R&T challenges or the larger goal of achieving the strategic objectives of the Decadal Survey of Civil Aeronautics. However, as noted in Chapter 4, NASA does not have the resources necessary to address all 51 R&T challenges simultaneously in a thorough and comprehensive manner, and so it is inevitable that the project plans, as a whole, do not live up to all of the expectations of the Decadal Survey. The grades in Table 2-1 reflect the committee’s assessment of how well a particular project addresses relevant aspects of a particular challenge. Thus, if only a small portion of a particular challenge is within the scope of a particular project but the project plans indicate that the project is or will do an excellent job in addressing that small research area, the cell in Table 2-1 representing the intersection of that project and challenge is green, even if the overall size of the relevant research is quite small. However, if a large portion of a particular challenge is within the scope of a particular project and if the project plans for the relevant research have minor or major shortcomings, the cell in Table 2-1 representing the intersection of that project and challenge is yellow or black, respectively, even if the overall size of the relevant research effort is quite substantial. The difference between a black grade and a white grade is illustrated by R&T challenge A7a, Aerodynamic Configurations to Leverage Advantages of Formation Flying. None of ARMD’s research projects plans to conduct research to support this R&T challenge, but if this challenge were pursued, the research would most appropriately be done by the Subsonic Fixed Wing (SFW) Project. Therefore, the SFW Project is graded black for R&T challenge A7a, and the other projects are graded white. As noted previously, NASA declined to provide detailed budget and staffing data for each project. Unless otherwise noted, the grades in Table 2-1 assume that the project research plans described to the com- mittee will be implemented with enough funding and personnel resources to succeed. Thus, the grades primarily indicate the extent to which NASA’s research plans are consistent with the Decadal Survey of Civil Aeronautics, but they do not necessarily indicate the likelihood that NASA will succeed in implementing those plans. The overall assessment for each R&T challenge is indicated in the columns of Table 2-1 that sum- marize the number of grades assigned to each challenge, by color. As shown, the committee found no significant short­comings in efforts by relevant ARMD research projects to address four R&T challenges (i.e., the grades assigned to these challenges are all green): • A4a. Aerodynamic designs and flow-control schemes to reduce aircraft and rotor noise • B10. Combined-cycle hypersonic propulsion systems with mode transition • D9. Synthetic and enhanced vision systems • E8a. Transparent and collaborative decision support systems Eight R&T challenges received only yellow grades, indicating that ongoing work suffered from minor shortcomings that could be corrected within the context of existing project plans: • A10. Reducing/mitigating sonic boom (novel aircraft shaping) • B2. Ultraclean gas turbine combustors • B6a. Variable-cycle engines to expand the operating envelope • C8. Structural innovations for high-speed rotorcraft • C9. High-temperature ceramics and coatings

24 NASA AERONAUTICS RESEARCH—AN ASSESSMENT • E2. Separating, spacing, and sequencing aircraft • E3. Roles of humans and automated systems for separation assurance • E7. Adaptive air traffic management (ATM) techniques to minimize the impact of weather Seven R&T challenges received only black grades, indicating the presence of major shortcomings that would be difficult to recover from within the context of existing project concepts. The committee verified NASA’s own assessment that NASA is not supporting four R&T challenges: • A7a. Aerodynamic configurations to leverage advantages of formation flying • B9. High-reliability, high-performance, and high-power-density aircraft electric power systems • D7. Advanced communication, navigation, and surveillance technology • D10. Safe operation of unmanned air vehicles in the national airspace In addition, the committee has determined that NASA is not substantively addressing three other R&T challenges: • B6b. Integrated power and thermal management systems • B8. Propulsion systems for supersonic flight • E4. Affordable new sensors, system technologies, and procedures to improve the prediction and measurement of wake turbulence For the other 32 R&T challenges, as indicated in Table 2-1, NASA is effectively addressing some areas but not others, and the overall assessment of these challenges is best described as “mixed.” The grades for each row of Table 2-1 are explained in the sections that follow. In some cases, the comments for green grades are rather brief. Rather than prepare detailed assessments of areas where NASA is doing well (and significant corrective action is not required), the committee focused its attention on areas where improvements need to be made (those with black or yellow grades). Also, the commit- tee chose not to justify its decision to assign white grades (that is, the determination that the scope of a given project was not relevant to a given R&T challenge). AERODYNAMICS AND AEROACOUSTICS This section summarizes the committee’s assessment of NASA research related to the top 11 R&T challenges involving aerodynamics and aeroacoustics (Area A) in the Decadal Survey of Civil Aero- nautics (NRC, 2006). A1  Integrated system performance through novel propulsion-airframe integration SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   Y black             This R&T challenge has the following milestones: • Validate the predictive capability for three-dimensional (3-D) mean and dynamic distortion at the p ­ ropulsion-airframe interface. • Validate the predictive capability of the impact of reacting exhaust flows on external aerodynamics.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 25 • Validate the predictive capability of acoustic radiation patterns from integrated propulsion-air- frame configurations. • Develop novel propulsion-airframe configurations for supersonic and hypersonic flight. The SFW Project is investigating important innovative concepts related to this R&T challenge. Research goals include development of dynamic models of integrated control systems, development and application of prototype actuators and innovative control methods, and laboratory experiments and piloted simulations to validate closed-loop system performance. Plans include flight-test validation of predictive models for propulsion-airframe integration of unconventional vehicle configurations, such as the blended-wing-body (BWB) aircraft, where possible. The Supersonics Project is supporting extensive code development in this area, and NASA plans to rely on yet-to-be-established partnerships with industry to execute key aspects of the above milestones with regard to validation. However, NASA has not established any notional vehicles to help refine its work. This shortcoming could be addressed, perhaps, by using one of the vehicle concepts developed by the Defense Advanced Research Projects Agency (DARPA) as part of the Quiet Supersonic Platform (Wlezien and Veitch, 2002), modified as necessary to reflect civil rather than military performance requirements. This R&T challenge is focused on novel configurations for propulsion-airframe integration. Propul- sion-­airframe integration is a key component of any air-breathing hypersonic vehicle. In addition, the Vehicle Tech­nology Integration, Propulsion Technology Integration, and Physics Based Multidisciplinary Design, Analysis, and Optimization (MDAO) elements of the Hypersonics Project are focused on the development of predictive tools. However, the Hypersonics Project will not validate the performance of these tools, nor will it exercise the tools to investigate the design of any specific, novel propulsion- airframe configurations. A2  Aerodynamic performance improvement through transition, boundary-layer, and separation control SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black             This R&T challenge has the following milestones: • Develop energy-efficient and flexible active flow-control actuators. • Develop improved models for the operation of flow actuators. • Demonstrate techniques to incorporate these models into flow-simulation schemes. • Validate models and simulation schemes through comparison with experiments. The SFW Project is investigating smart material actuators as well as active and passive control concepts. Research plans include validation at the configuration, component, and physics levels. Plans include a key test to demonstrate improved performance via a high-lift wind tunnel model with flow- control actuation integrated into realistic aircraft structure. The SRW Project has no planned research to address the above milestones. The Supersonics Project is working on both foundational research and performance improvement related to this challenge, including actuator development. This work would be facilitated if NASA had a quiet wind tunnel in the Mach number range being investigated (approximately Mach 1.5 up to Mach 2.5) for transition validation. Based on experience with existing quiet wind tunnels at Langley Research Center (which operates at Mach 3.5) and Purdue University (which operates at Mach 6), it would be less

26 NASA AERONAUTICS RESEARCH—AN ASSESSMENT expensive to build a new quiet facility operating at about Mach 2 than to do the flight tests that would otherwise be required. Plans for the Aerodynamics, Aerothermodynamics, and Plasmadynamics element of the Hyper- sonics Project include fundamental research on turbulence and boundary-layer physics, and one task (HYP.04.04.6) intended to demonstrate boundary flow control using a microwave plasma. However, this activity does not include improved actuators as a goal, and it is unlikely to significantly improve the aerodynamic performance of hypersonic vehicles. A3  Novel aerodynamic configurations that enable high-performance and/or flexible multimission aircraft SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black black               This R&T challenge has the following milestones: • Develop a family of aircraft configurations with cruise efficiency twice as high as conventional aircraft. • Demonstrate design approaches to develop novel configurations able to operate from small airfields. • Validate the ability to predict the performance of novel airframe configurations using data from ground and flight tests. The SFW Project has a substantial research effort in developing tools to predict advanced-concept airplane performance. It has defined a trade space that includes aerodynamic efficiency, noise, and emissions as key criteria to evaluate advanced configurations. Both conventional and hybrid wing fami- lies of configurations are being explored, along with powered lift and flow-control concepts to reduce minimum runway length required for takeoff and landing. In the case of the BWB high cruise efficiency configuration, these tools are being validated by flight test. The Subsonic Rotary Wing (SRW) Project has no focused research to design or develop novel aero- dynamic configurations for rotorcraft. The introduction to the project description mentions the compound slowed rotor concept, but the rest of the document does not describe any foundational or integrated research that would support this challenge by developing the concept. The Supersonics Project is developing tools, but there is little or no effort to apply those tools to develop and predict the performance of notional aircraft configurations. Some external researchers work- ing under NASA Research Announcements (NRAs) may be doing some analyses of their own notional aircraft configurations, but this work would be of much greater value if NASA were to define one or more notional aircraft configurations as a common reference. A4a  Aerodynamic designs and flow-control schemes to reduce aircraft and rotor noise SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C               This R&T challenge has the following milestones: • Improve techniques for prediction and control of the aeroacoustics associated with high-lift devices, ­protuberances, and cavities for fixed-wing aircraft.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 27 • Develop techniques for the prediction and design of quiet drag devices for fixed-wing aircraft. • Improve understanding and modeling of unsteady fluid–structure interactions and resulting noise radiation for rotary- and fixed-wing aircraft. • Demonstrate novel rotor system design tools that can be used to reduce rotor noise with minimum performance sacrifices for rotorcraft. Research plans for the SFW, SRW, and Supersonics Projects support a wide array of research activi- ties that would support the above milestones. For example, research related to noise is a large part of the Propulsion and Power Systems element and the Airframe Systems element of the SFW Project. In addition, NASA’s previous participation in the Quiet Technology Demonstrator, which included partners from manufacturers and the airlines in the flight testing of advanced noise control techniques for SFW aircraft, provided a wealth of modeling, design, and validation experience. This is an important example of collaboration to facilitate technology transition to in-flight use. In addition, aeroacoustics research by the SRW Project includes foundational research to advance the understanding of sources and mechanisms of noise generation and propagation, experimental validation of predictive tools, and the stipulation of explicit metrics against which advancements in this field would be measured. The Supersonics Project is supporting variable-cycle engine research, which would help reduce noise. A4b  Accuracy of prediction of aerodynamic performance of complex 3-D configurations, including improved boundary-layer transition and turbulence models and associated design tools SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y Y             This R&T challenge has the following milestones: • Develop improved techniques for the prediction of boundary-layer transition on 3-D configura- tions and validate them against ground- and flight-test data. • Demonstrate computationally efficient techniques to couple aerodynamic and structural analysis tools. • Develop structured techniques for predicting performance in the presence of parameter uncertainties. The SFW Project plans to improve the ability to predict high-lift performance by developing 3-D prediction models that would be validated in wind tunnel tests with active flow-control experiments. The SRW Project is studying structured and unstructured grids in computational fluid dynamics (CFD)-based modeling applicable to rotorcraft. The project also includes research that links these numerical models to structural and acoustic analysis capabilities. There are no plans, however, to model the effects of uncertainty in the predictive capabilities of these models or to validate the numerical models using flight tests. The Supersonics Project is developing and validating models that address this challenge, including code development for transition and turbulence modeling of 3-D configurations. These models can and should be validated using existing data. The Aerodynamics, Aerothermodynamics, and Plasmadynamics and Vehicle Technology Integration elements of the Hypersonics Project include many computational and experimental tasks to investigate boundary-layer transition and turbulence. The application and evaluation of the resulting models in complex 3-D configurations, however, seem to have a low priority.

28 NASA AERONAUTICS RESEARCH—AN ASSESSMENT A6  Aerodynamics robust to atmospheric disturbances and adverse weather conditions, including icing SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y                 This R&T challenge has the following milestones: • Develop and validate 3-D icing prediction tools. • Demonstrate systems with improved spatial and temporal measurements of upstream environ- mental conditions. • Develop high-bandwidth techniques to respond to and mitigate the impact of upstream environ- mental conditions. This challenge is relevant to subsonic fixed-wing aircraft. However, it is not necessary for the SFW Project to address this challenge because NASA’s Office of Safety is supporting worthwhile research in this area. Unfortunately, there is no substantial effort related to the specific concerns of rotorcraft. The reference document for the SRW Project describes some research to (1) develop numerical models for predicting the effects of ice accretion on lifting characteristics and (2) simultaneously develop a database of experimental results obtained in wind tunnel tests for validation purposes. However, the SRW Project is not developing models of rotorcraft behavior in wind shear of aircraft flow-field immersion, nor is it developing systems to detect and mitigate the effect of upstream environmental conditions on the safe operation of rotorcraft. Some small-scale wind tunnel tests are underway to look at ice accretion for rotor- craft, but this work is too limited to make substantial progress in addressing the above milestones. A7a  Aerodynamic configurations to leverage advantages of formation flying SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black                   This R&T challenge has the following milestones: • Develop improved methods to accurately predict wake vortex evolution. • Demonstrate design tools for evaluation and optimization of multiple interacting airplanes. • Validate models and tools for formation flying using ground and flight experiments to evaluate real ­atmospheric effects. The SFW Project has no planned research to address the above milestones. A7b  Accuracy of wake vortex prediction, and vortex detection and mitigation techniques SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black Y     black         This R&T challenge has the following milestones: • Develop numerical techniques to predict accurately wingtip vortex trajectory, strength, and dissipation.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 29 • Validate numerical methods with experiments and flight testing. • Demonstrate low-cost techniques for locating and measuring the strength of wake vortices for ground-based and aircraft-based applications. • Integrate local weather prediction techniques into larger-scale weather models. • Investigate aircraft designs that mitigate the strength of wake vortices. The SFW Project is doing no work to investigate aircraft designs that mitigate the strength of wake vortices, which is the only milestone for this challenge that is related to the SFW Project. The SRW reference document describes a focus on enhancing both structured and unstructured grid flow solvers, where one of the emphasis areas is an accurate treatment of wake vortices. Plans include code validation using experimental data. However, research plans do not include investigation of rotary- wing aircraft designs that mitigate the strength of wake vortices. This is a significant shortcoming. A goal of the NGATS Air Traffic Management (ATM)-Airportal Project is to model and to predict wake vortex behavior to enable superdensity operations. A goal of the Coordinated Approach and Depar- ture Operations Management element of the Airspace Project is to improve the modeling and prediction of wake vortex behavior as well as the understanding of wake vortex on airport and terminal-area capac- ity. The scope of this research has been reduced in recent years, in that NASA does not plan to develop new sensors, and it will rely on the National Oceanic and Atmospheric Administration and the Federal Aviation Administration (FAA) to take the lead in research related to the determination and characteriza- tion of weather and hazards such as wake vortices. However, these are not significant shortcomings in terms of the contribution of the NGATS ATM-Airportal Project to overcoming this challenge.  The NGATS ATM-Airspace Project is doing no work related to in-flight applications of wake vortex research. A9  Aerodynamic performance for vertical and short takeoff and landing (V/STOL) and extremely short takeoff and landing (ESTOL), including adequate control power SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y black                 This R&T challenge has the following milestones: • Develop low-drag high-lift systems. • Demonstrate systems to provide pitch trim and control power at low speeds. • Develop new techniques for active twist control of rotors. • Demonstrate low-cost, simple flow-control techniques for prevention of leading-edge separation from vertical and/or short takeoff and landing (V/STOL) wings. • Improve wing design and fuselage shaping to reduce transonic cruise drag. Plans for the SFW Project include development of technologies, such as active flow-control and mor- phing materials, that could enable advanced V/STOL and extremely short takeoff and landing (ESTOL) configurations, but plans do not include research to support other aspects of this challenge. Another concurrent National Research Council study is focused exclusively on NASA’s wake vortex research. The results of that study were not available in time to factor them into this report.

30 NASA AERONAUTICS RESEARCH—AN ASSESSMENT The rotorcraft portion of this challenge is focused on active twist control of rotors to enhance aero- dynamic performance at low speeds, and the SRW Project is conducting no relevant research. A10  Techniques for reducing/mitigating sonic boom through novel aircraft shaping SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C     Y               This R&T challenge has the following milestones: • Develop guidelines for allowable exposure of the public to sonic booms. • Develop accurate techniques for the prediction of sonic boom propagation through the atmosphere under realistic environmental conditions. • Demonstrate novel aircraft shapes that minimize sonic boom levels. Historically, NASA has been the leader in developing sonic boom prediction techniques. The sonic boom element of the Supersonics Project is focused on modeling sonic booms, and a more vigorous effort is needed to make substantial and timely progress in developing design evaluation tools that could be used to (1) predict the sonic boom characteristics of various aircraft shapes and (2) facilitate the design of new aircraft shapes with lower levels of sonic boom. There is no evident validation process for the computer codes being developed. A11  Robust and efficient multidisciplinary design tools SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y Y Y             This R&T challenge has the following milestones: • Develop and validate physics-based models to predict performance for novel aircraft configurations. • Assess a family of aircraft configurations with major improvement in cruise efficiency, including a quantitative description of the benefits and risks. • Assess novel concepts for flexible multimission aircraft, including a description of potential benefits in performance and cost. • Conceive design approaches to develop novel V/STOL and ESTOL configurations. • Validate design codes to predict the performance of novel airframe configurations by comparing code predictions with ground and flight tests. The SFW Project is applying and validating tools for advanced configurations. A particular strength of this effort is the collaboration of NASA researchers with U.S. Air Force and industry researchers to validate models through flight test. The SRW Project plans to develop a number of modeling and simulation tools, but it is not devel- oping the integrated, multidisciplinary modeling techniques necessary to develop an MDAO capability for rotary-wing applications. The Supersonics Project is developing appropriate tools but has not defined the configurations and tests (ground and/or flight) necessary for validation.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 31 The Physics Based MDAO element of the Hypersonics Project includes tasks to develop multidis- ciplinary design capabilities in the hypersonic flow regime. However, the Hypersonics Project will not exercise these tools to investigate the performance of any specific class of aircraft configurations. PROPULSION AND POWER This section summarizes the committee’s assessment of NASA research related to the top 10 R&T challenges involving propulsion and power (Area B) in the Decadal Survey of Civil Aeronautics (NRC, 2006). B1a  Quiet propulsion systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y               This R&T challenge has the following milestones: • Develop validated physics-based models to predict engine noise and conduct trade-off studies. • Improve understanding and prediction capabilities, and develop propulsion cycles compatible with noise and emissions reduction. • Develop advanced low-noise fan designs, liner concepts, and active control technologies. • Develop concepts to reduce installed noise (e.g., adaptable chevrons). • Develop and demonstrate propulsion designs that show the feasibility of technologies to reduce noise by 10 dB (in 15 years) from Boeing 777/GE 90 levels. The SFW Project has established the goal of reducing the noise of commercial aircraft at the three certification points (takeoff, sideline, and approach) by a total of 32 to 42 dB below current (Stage 4) standards over the next 5 to 11 years. It seems unlikely that NASA will be able to achieve these ambi- tious goals, which are more aggressive than the goals established by the Decadal Survey. Nonetheless, NASA is supporting important research to reduce aircraft noise, including trade-off studies of noise versus CO2 emissions for different engine cycles, and the assessments in this section are based on the ability of the NASA aeronautics program to address the challenges and milestones in the Decadal Survey of Civil Aeronautics, not NASA’s own goals. For purposes of certification and regulatory compliance, the noise produced by commercial aircraft is determined by three measurements of noise on the ground, as follows: • Takeoff noise is measured 6,500 meters from the point where the aircraft releases its brakes, as the aircraft flies overhead after takeoff. •  Sideline noise is measured at a point 450 meters to the left or the right of the runway centerline, at a point where the noise level is greatest after takeoff, as the aircraft flies past. •  Approach noise is measured at a point 2,000 meters from the threshold of the runway, as the aircraft flies overhead prior to landing. NASA has established an “N + 1” goal of reducing noise at the above points by a cumulative total of 42 dB below the “Stage 3” standard defined by the International Civil Aviation Organization and adopted by the Federal Aviation Administration. The N + 2 goal is 52 dB below Stage 3. The current standard for type certification of new aircraft designs is Stage 4, which is 10 dB quieter than Stage 3 (cumulative, for all three certification points). Thus, the N + 1 and N + 2 goals represent a cumulative improvement of 32 to 42 dB (at all three points) relative to current limits, or about 11 to 14 dB at any one point.

32 NASA AERONAUTICS RESEARCH—AN ASSESSMENT This R&T challenge is targeted primarily at the prediction and mitigation of noise from jet engines. Plans for the SRW Project include research to (1) explore quiet propulsion and drive systems to increase cabin comfort and (2) improve the ability to predict noise and determine how it will propagate through he atmosphere under various conditions. Plans for the Supersonics Project include research that effectively addresses relevant aspects of this challenge, including evaluation of empirical and statistical noise prediction tools, development of an improved statistical model for broadband shock noise, and jet noise studies. B1b  Ultraclean gas turbine combustors to reduce gaseous and particulate emissions in all flight segments SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y   Y               This R&T challenge has the following milestones: • Understand particulate matter formation mechanisms and kinetics and develop fuel additives to disrupt formation. • Understand air toxicity measurement techniques and the impact of particulate matter on human health and welfare. • Improve understanding and prediction capabilities and develop optimized approaches for mixing in multi­phase flows. • Develop large eddy simulations with optimized subgrid models that contain key physics needed to capture chemical reactions, mixing, and unsteady combustor phenomena. • Develop physics-based, reduced-order combustor models, including emissions, combustion insta- bility, blowoff, and flashback, for inclusion in intelligent engine control systems. • Develop validated chemical mechanisms that describe fuel kinetics. • Develop and demonstrate combustor designs that show the feasibility of technologies to reduce oxides of nitrogen (NOx) emissions by 85 percent while also reducing particulate matter, rela- tive to the limits set by the International Civil Aviation Organization in 1996 for future large and regional subsonic engines (with pressure ratios of 55:1 and 30:1, respectively). The SFW and Supersonics Projects are supporting research to reduce emissions. This research encompasses all but the last of the above milestones, and NASA is providing some support, such as test facilities, to support industry-funded research. Even so, industry seems to be taking the lead in engine emissions research. Given NASA’s expertise in studies of engine emissions, the state of the art in this very important area would advance more quickly if NASA were more proactive. B3  Intelligent engines and mechanical power systems capable of self-diagnosis and reconfiguration between shop visits SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black Y black       Y       This R&T challenge has the following milestones: • Develop better computational simulation tools to understand operability limits.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 33 • Develop better life prediction tools. • Develop improved steady-state and dynamic performance checks. • Develop improved health diagnostics systems. • Develop new health prediction systems. • Develop improved clearance control systems. • Develop active compressor stall control. • Develop active combustion control. This R&T challenge calls for the development of computational simulation tools to understand the new generation of engines that have a high degree of self-diagnostics and regulation. Relevant research by the SFW and Supersonics Projects is unlikely to make a significant difference to the state of the art; most of the research relevant to this challenge for these flight regimes is being funded by organizations other than NASA. Most of the diagnostics research described in the SRW reference document pertains to rotorcraft drive systems and not the engines themselves. This research would investigate active control for increased stall margins, and it includes experimental validation of models. The Integrated Vehicle Health Management (IVHM) Project is addressing some aspects of this chal- lenge, such as the issue of monitoring propulsion systems with smaller unique high-temperature sensors in the gas path and the development of diagnostic systems to predict engine health. B4  Improved propulsion system fuel economy SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y Y black               This R&T challenge has the following milestones: • Demonstrate laboratory-scale materials for 1500°F compressor disks. • Demonstrate materials for full-scale, 1500°F compressor disks. • Perform 1,000-hour test of a 50-horsepower per pound speed reduction gearbox. • Test a reduced-weight, high-bypass-ratio engine and nacelle-to-wing configuration in a wind tunnel. • Demonstrate an acceptably low-cost, advanced high-pressure turbine cooling system. The Durability of Engine Superalloy Disks element of the Aging Aircraft and Durability Project is working to improve the durability of disks at operating temperatures up to 1300°F, but this challenge calls for research to enable operating temperatures up to 1500°F (for the purpose of improving fuel economy), and research to develop new materials able to function at 1300°F is likely to focus on classes of materials that will be unsuitable for operations at 1500°F. As a result, this research is not relevant to this challenge. Neither the SFW Project nor the Supersonics Project is working on developing compressor disks with an operating temperature of 1500°F, higher-pressure-ratio engines, or the thermal problems associated with those engines. However, the SFW Project is working to improve the engine component efficiency and aircraft aero­dynamics, which should improve specific fuel consumption. The SRW Project is addressing this challenge through fundamental research in oil-free engines for rotary-wing flight and the integration of such engines with an optimized drive system gearbox. How- ever, no significant full-scale demonstrations are planned. Also, the Decadal Survey predicts that, over

34 NASA AERONAUTICS RESEARCH—AN ASSESSMENT the long term, research related to this challenge should be able to improve fuel economy by 30 percent relative to the GE 90 (for large commercial engines) and by 30 percent relative to T700/CT7 (for small engines). However, the SRW Project has not set specific targets for improving fuel efficiency. B5  Propulsion systems for short takeoff and vertical lift SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black Y                 This R&T challenge has the following milestones: • Demonstrate pressure ratios between 25:1 and 30:1 and turbine inlet temperatures of 2800°F for 3,000-shaft-horsepower-class engine components. • Develop and validate the design tools required for candidate gearboxes and clutch systems. • Demonstrate highly reliable gearboxes, which have transfer efficiencies of about 99.8 percent and power-to-weight ratios of about 50 horsepower per pound. • Demonstrate clutch system technologies with 10,000-cycle life and a probability of failure of 1 × 10–6 over the life of the system. The SFW Project has no planned research to address the above milestones. The SRW Project includes research on optimization of gearbox-engine systems, wide-operability engines, and efficient, high-power-density engine technologies. However, these tasks only use metrics related to the accuracy of tools, and they do not target specific levels of propulsive efficiency. Neither the SFW Project nor the SRW Project includes thrust vectoring or engine-assisted lift research. B6a  Variable-cycle engines to expand the operating envelope SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y   Y               This R&T challenge has the following milestones: • Develop variable exhaust nozzle technology to optimize fuel burn. • Develop improved thermal management systems. • Develop ceramic matrix composite technologies for hot section components. • Develop highly loaded, high-speed bearings. • Develop probabilistic analysis for more accurate designs and life prediction. • Develop improved turbine cooling technology. • Develop high-temperature combustors to accommodate increased operating pressure ratios. • Develop improved aircraft-engine integration tools. The SFW Project is supporting some component research that addresses most of the above mile- stones, but the U.S. Air Force is leading research in this area. Plans for the Supersonics Project include research that would likely make substantial progress in the near term in meeting the intent of this R&T challenge, although the usefulness of this work will be limited somewhat by the lack of any notional vehicle to guide the research.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 35 B6b  Integrated power and thermal management systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black black black black             This R&T challenge has the following milestones: • Identify and mature new business models for the design, development, validation, and support of hardware and software components of integrated systems. • Develop an object-oriented modeling infrastructure that allows networking resources to operate across different hardware platforms and geographic sites. • Develop new engine-airframe systems integration architectures for both subsonic and higher-speed flight. • Develop physics-based subsystem component models that can analyze transient operations. • Develop and mature concepts for the integration of fuel cell technology as secondary power sources. • Develop advanced electric or electromechanical actuators that have rapid response, high power- to-weight, and low heat rejection. • Develop subsystem components that can survive in more stressful thermal environments, require less cooling, and reject less waste heat, including thermally efficient fuel pumps and high-tem- perature electronics for power management and distribution systems. • Develop lightweight, high-energy-density batteries. • Develop advanced heat exchanger technologies. The high velocity of hypersonic vehicles make it particularly important to manage the power and thermal balance. However, thermal management is important for aircraft in all flight regimes. Even so, neither the Hypersonics, Supersonics, SFW, nor SRW Project has planned research to address the above milestones. B8  Propulsion systems for supersonic flight SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C     black               This R&T challenge has the following milestones: • Establish needed boundary conditions, initial conditions, and other inputs and outputs for each module of multidisciplinary, system-level design tools. • Develop technology that will enable supersonic aircraft to meet Stage 4 noise standards. • Validate boundary-layer control techniques for inlet performance and drag reduction. • Demonstrate a supersonic variable-cycle engine with specific fuel consumption of 1.1 or lower and a thrust-to-weight ratio of at least 6. • Demonstrate high-performance, low-drag, noncircular inlet designs. • Obtain flight-test data on noise, emissions, human annoyance caused by sonic boom, and system interactions across the flight regime. The Supersonics Project is not working to achieve a specific fuel consumption of 1.1 or a thrust-to-

36 NASA AERONAUTICS RESEARCH—AN ASSESSMENT weight ratio of at least 6. Little or no work is being done to achieve the higher pressure ratios, higher operating temperatures, extended flight times, and long times between major maintenance that the pro- pulsion systems for a commercially viable supersonic transport will need to demonstrate. B9  High-reliability, high-performance, and high-power-density aircraft electric power systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black black black       black       This R&T challenge has the following milestones: • Demonstrate tenfold increase in power density for suitable electric generators and motors. • Demonstrate fivefold increase in energy and power density of suitable batteries and hybrid storage systems (e.g., the battery–ultracapacitor). • Demonstrate an order-of-magnitude lighter optimized power system architecture (including, for example, a direct-current power bus, remotely controlled loads, and a wireless system control). • Demonstrate intelligent power management and distribution using advanced system models and wireless sensors or sensorless control technologies for graceful degradation and failsafe operation. • Demonstrate advanced analysis and simulation tools for multiconverter power systems, which can predict new modes of system dynamics and instability. Neither the Supersonics, SFW, nor SRW Project has planned research to address the above milestones. The IVHM Project is developing the Advanced Diagnostics and Prognostics Testbed facility at NASA Ames Research Center. This system will investigate intelligent power management systems for graceful and failsafe degradation and develop modeling and simulation tools that can assess power sys- tems dynamics. However, the IVHM Project is doing no work to increase the energy and/or power density of electric generators, motors, ­batteries, hybrid power storage systems, or power system architectures. B10  Combined-cycle hypersonic propulsion systems with mode transition SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C                   This R&T challenge has the following milestones: • Develop advanced diagnostics capable of measuring time-averaged and time-resolved flow param- eters and their correlations. • Demonstrate ramjet-scramjet (dual mode) transition and isolator performance for a simplified geometry with alternately clean and vitiated air. • Conduct transient experiments to simulate cowl door movement for turbine-ramjet mode transi- tion and cowl lip movement to control inlet contraction. • Demonstrate injection, mixing, and combustion using simple fuel injectors and with alternately clean and vitiated air. • Conduct inlet studies with variable angles of attack and sideslip angles.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 37 • Investigate new engine configurations using inward-turning inlets, elliptical cross sections, and so on. The Propulsion and Propulsion Technology Integration elements of the Hypersonics Project are conducting a significant amount of experimental and computational work related to the development of highly reusable and reliable launch systems. These systems would use hypersonic vehicles powered by air-breathing, combined-cycle, propulsion engines, and a substantial amount of related work supported by the Hypersonics Project would meet the intent of this R&T challenge. MATERIALS AND STRUCTURES This section summarizes the committee’s assessment of NASA research related to the top 10 R&T challenges involving structures and materials (Area C) in the Decadal Survey of Civil Aeronautics (NRC, 2006). C1  Integrated vehicle health management SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   black             Y This R&T challenge has the following milestones: • Develop lightweight sensor networks that characterize the state of materials and structures over large areas. • Develop very-low-power or self-powered wireless sensors capable of operation in harsh environments. • Develop artificial intelligence to automatically assess structural integrity from sensor responses and implement damage mitigation protocols. • Develop components and sensors that are cost-competitive and available from multiple vendors. • Flight test full-scale IVHM systems to detect multisite damage. This challenge is unique in that its scope encompasses almost all the work being conducted by a single ­project: the IVHM Project. The discussion of this R&T challenge in the Decadal Survey of Civil Aeronautics notes that “with a national fleet of aging aircraft and infrastructure in an industry with low profit margins, IVHM is increasingly important. . . . Early detection of impending failures in aircraft materials, structures, and wiring is critical for avoiding fatalities as a part of the aging aircraft program. IVHM also reduces time lost to scheduled maintenance and reduces the likelihood of unscheduled down- time” (NRC, 2006, p. 113). In addition, the reference document for the Aging Aircraft and Durability Project states that that “aircraft aging is a significant national issue” (NASA, 2006, p. 1). The average age of U.S. commercial aircraft dropped in the aftermath of the attacks on September 11, 2001, as many older aircraft were retired. On a global basis, the average age of regional jets operated by scheduled airlines is now less than 7 years. By contrast, the average age of narrowbody jets operated by scheduled airlines, nonscheduled airlines, and air cargo carriers is 13.5 years, 21.5 years, and 28.2 years, respectively (OAG, 2007). In addition, the average age of aircraft operated by the Department of Defense (DoD) is also increasing, sometimes to the point of exceeding the original design service life of the vehicles.

38 NASA AERONAUTICS RESEARCH—AN ASSESSMENT Even though aging is an issue with existing commercial and military aircraft, the project description for the Aging Aircraft and Durability Project says that its focus “is on aging and damage processes in ‘young’ aircraft, rather than life extension of legacy vehicles” (NASA, 2006, p. 1). NASA’s research plans in this area emphasize new and emerging material systems and fabrication techniques and the potential hazards associated with aging-related degradation. Such a focus would greatly limit the ability of the project to have any impact on the air transportation system in the near or mid term. Advanced IVHM can expedite the introduction of innovative material systems and structural concepts in rotorcraft. However, the reference document for the SRW Project does not address research related to the design or development of rotorcraft IVHM technologies or systems. In particular, the SRW Project does not focus on the use of sensor networks to gage the real-time state of rotorcraft systems, nor does it support research on the use of data to mitigate the influence of structural or material degradation. The IVHM Project is developing health management sensors and sensor networks applicable to airframes, aircraft systems, propulsion systems, and environmental hazards (such as ice, radiation, and lightning strikes). This work includes fiber-optic sensors for determining the distribution of strain and temperature in an airframe system, high-temperature silicon-carbide sensors, extensive studies of the impact of ionization and radiation, data mining research. NASA’s IVHM research on ice as a hazard does not clearly add value to icing research done elsewhere. However, IVHM research on data mining is novel and has the possibility of creating new paradigms for aircraft maintenance over the life of the vehicle. NASA may be able to create universal formats, protocols, and databases for representing data and informatics about any air vehicle. NASA is also developing a testbed at Ames Research Center that simulates vehicle power systems and allows IVHM principles to be applied to power network control- lers and systems. This testbed seems relevant to NASA’s future spacecraft missions, however, and it is uncertain how it can be used for direct support of aircraft. The Aging Aircraft and Durability Project has three research areas at the multidisciplinary capabili- ties level (i.e., Level 3, as defined by ARMD). These research areas are Detect, Predict, and Mitigate. Some of the research related to the Detect area supports this challenge and some of the above milestones, although in-flight monitoring is not identified as a goal. Reduction of maintenance downtime is one goal of this challenge, but NASA staff working on the Aging Aircraft and Durability Project lack firsthand experience with commercial transport maintenance operations. The Aging Aircraft and Durability Proj- ect’s low level of effort and broad scope bring into question its ability to make significant progress. C2  Adaptive materials and morphing structures SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y black black               This R&T challenge has the following milestones: • Identify new morphing missions and designs for reconfigurable civil aircraft, including supersonic aircraft with low sonic boom. • Develop the next generation of high-strain, adaptive materials or devices that can be activated and deactivated for repositioning, with actuation deformation up to 100 percent. • Develop novel integrated adaptive materials that allow wing surfaces and fuselages (including inlets) to rapidly change shape or alter load paths. • Conduct scaled wind tunnel and flight tests on active, morphing aircraft to enable innovative, lightweight designs.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 39 • Develop new, structurally integrated adaptive devices for flow control on a commercial aircraft to, for example, reduce drag and improve performance in off-design conditions. • Develop analysis and design tools that account for and accurately predict nonlinear behaviors of adaptive materials and morphing structures. The SFW Project is doing good work in basic material composition and adaptive structures and materials, although a greater effort to apply this research to structural configurations would be necessary to fully meet the intent of this R&T challenge. The SRW Project includes little or no research on the use of adaptive materials for rotorcraft struc- tural applications. The Supersonics Project is concentrating on aeroelastic issues, but not on adaptive materials or morphing. C3  Multidisciplinary analysis, design, and optimization SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y Y           black This R&T challenge has the following milestones: • Develop multidisciplinary analysis tools that incorporate aerodynamics, structural dynamics, vibration, thermal response, acoustic response with structural response to mechanical loads. • Extend multidisciplinary tools to incorporate explicit mathematical modeling of design issues such as manufacturing processes, life-cycle cost, and repairability. • Develop efficient approaches for multivariable optimization. • Develop efficient and effective search processes for the analysis of large, complex systems. • Develop approaches for modeling uncertainty in data-lean environments. • Develop computationally efficient methods for reliability assessment. • Develop a systematic approach for modeling risk and uncertainty in complex coupled systems. The SFW and Supersonics Projects are demonstrating the implementation of relevant tools in an integrated program that addresses the above milestones. For example, the Computationally Guided Mul- tifunctional Materials Development element of the SFW Project includes development of physics-based models to increase the funda­mental understanding of materials science, establish the interconnectivity of the multiple disciplines required to provide parametric analysis tools, and develop examples of key struc- ture-property relationships for novel materials. Validation would be achieved by experiment. Ultimately, this approach to materials design would enable the tailoring of key properties such as strength, durability, acoustic damping, and conductivity to address multifunctional applications. The SRW Project is developing a suite of analysis tools, but it is not supporting substantial work in assembling the tools into an MDAO capability for rotary-wing applications. The SRW Project is not explicitly examining the computational fidelity of these tools for different stages of the MDAO pro- cess, nor is it making a significant effort in integrating the various analysis tools and linking them to a design optimization capability. Neither is the SRW Project quantifying or representing the influences on uncertainty in the analysis and design tools. Several elements of the Hypersonics Project address this R&T challenge. The Materials and Struc- tures element includes milestones related to multidisciplinary thermal and structural analysis methods for the design and evaluation of hypersonic airframe and propulsion structures that incorporate life

40 NASA AERONAUTICS RESEARCH—AN ASSESSMENT prediction and reliability models. The Vehicle Technology Integration element includes milestones related to the development of tools and ­methodologies to design and analyze the highly coupled multi- disciplinary systems problems presented at the vehicle system level in support of hypersonic vehicles. The Physics Based MDAO element includes milestones related to the development of advanced phys- ics-based multidisciplinary predictive design, analysis, and optimization tools focused on supporting Highly Reliable Reusable Launch Systems (HRRLS) and High Mass Mars Entry Systems (HMMES) mission vehicles. The Aging Aircraft and Durability Project is organized around eight challenge problems, each of which is more or less a stand-alone research effort. They may touch on some of the above milestones, but the project details are not integrated to produce multidisciplinary design, analysis, or optimization. A systematic approach for modeling risk and uncertainty in complex coupled systems (the last milestone) would be very helpful in identifying and prioritizing aging aircraft and durability issues. C4  Next-generation polymers and composites SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y black             Y This R&T challenge has the following milestones: • Demonstrate fabrication of composites with many different types of reinforcement fibers. • Integrate adaptive materials to increase functionality. • Develop techniques for manufacturing, processing, and dispersion of nanoscale reinforcements. • Develop a fundamental understanding of how different kinds of reinforcements (e.g., nano, func- tional, or hybrid additives) affect the performance of polymers and composites. • Improve damage tolerance for high-temperature polymers. • Develop effective life prediction models for polymers and composites. • Investigate environment-friendly end-of-life reuse or disposal strategies. The Materials, Structures, and Mechanical Components element of the SFW Project is addressing a number of composites issues, but a more active program is needed in this very important area. The SRW Project has no planned research to address milestones relevant to rotorcraft. Plans for the Supersonics Project include research that would make substantial progress in the near term in meeting the intent of this R&T challenge. Three of the eight challenge problems (CPs) being addressed by the Aging Aircraft and Durability Project address polymers and composites, as follows: • CP-03: Durability and Structural Integrity of Composite Skin-Stringer Fuselage Structure • CP-04: Durable Bonded Joints • CP-05: Durability of Engine Fan Containment Structure The challenge problem on Durability and Structural Integrity of Composite Skin-Stringer Fuselage Structure (CP-03) directly addresses this challenge, but given the large level of effort in industry and extensive role that composites are already playing in commercial products, the timing of this effort and the low level of effort will limit the value of this research. The value of CP-04 and CP-05 is uncertain given the low levels of effort in both areas. In addition, for CP-05, blade containment systems using current technology already demonstrate a high level of protection, especially for composite blades.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 41 C5  Noise prediction and suppression SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y black               This R&T challenge has the following milestones: • Measure noise signatures in controlled environments such as anechoic wind tunnels, for a range of flight conditions. • Predict noise signatures using advanced multidisciplinary methodologies, validating against test data for level and maneuvering flight modes. • Develop efficient structural solutions for interior noise control, that is, structural optimization. • Design non-load-bearing passive noise control. • Design active controls for interior and exterior noise through smart structures technology. • Develop low-noise rotors. • Selectively flight test full-scale systems with noise signature measurement. The SFW Project is supporting research on fundamental noise control to alleviate structural noise. The Systems Analysis, Design, and Optimization element recognizes noise as an important aspect of MDAO modeling, although the principal investigator (PI) reports that there is a shortage of noise analysts available to support this work. The Supersonics Project has no planned research to address the above milestones. The Decadal Survey of Civil Aeronautics notes that noise prediction and suppression are very important for rotorcraft. The reference document for the SRW Project emphasizes the need for research to reduce both interior and exterior noise, and it characterizes noise generation as a problem involv- ing coupled structures, fluid dynamics, and acoustics. The use of smart materials to reduce interior noise is one task (among many) in the aeroacoustics area of the SRW Project. NASA is a key player in DARPA’s Helicopter Quieting Program, although that is not mentioned in the SRW Project’s reference document. C6a  Innovative high-temperature metals and environmental coatings SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black Y black           Y This R&T challenge has the following milestones: • Define required models and a model integration strategy to provide necessary functionality for simulations. • Select models for further development, based in part on how well they are aligned with materials systems that provide the greatest benefit for propulsion systems. • Develop models for selected substrates and associated environmental coatings; determine all the physical parameters required by the models. See <www.darpa.mil/ucar/text/programs/hq.htm>.

42 NASA AERONAUTICS RESEARCH—AN ASSESSMENT • Validate the models by applying them to the development of new materials that are selected in concert with industry. The SFW Project has no planned research to address the above milestones. The reference document for the SRW Project affirms the importance of advanced material concepts for improved efficiency of small rotorcraft engines. Plans for the SRW Project include research into monolithic silicon nitride for hot sections and silicon carbide coatings. As suggested in the Decadal Survey, validation of modeling through experimental tests in the high-temperature engine test facilities is also planned. The Supersonics Project is supporting some research on modeling and development of high-tem- perature materials, coatings, and processes, but it is not supporting research related to other aspects of this challenge. The Materials and Structures element of the Hypersonics Project includes experimental tests of metallic materials and structures, but relevant modeling efforts do not seem to be part of this project. In the Aging Aircraft and Durability Project, the first challenge problem (CP-01: Damage Method- ology for Metallic Airframe Structures) and the second challenge problem (CP-02: Structural Integrity of Integral Metallic Structure) do not specifically address metal high temperatures or coatings, but the results of this research could contribute to overcoming this challenge, particularly with regard to a better understanding of aluminum structures in elevated temperature environments. Plans for CP-06 (Durabil- ity of Engine Superalloy Disks) and CP-07 ­(Durability of Engine Hot Section) address this challenge, and research in this area clearly could have significant value, but the low planned levels of effort (2.9 labor-years for CP-06 and 1.5 labor years for CP-07) draw into question the likelihood that planned work will substantially advance the state of the art. C6b  Innovative load suppression, and vibration and aeromechanical stability control SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y black             This R&T challenge has the following milestones: • Predict vibration using advanced CFD methodologies and validate experimentally. • Predict aeromechanical stability for advanced configurations and expanded flight envelope (including hypersonic flight) and validate experimentally. • Measure vibratory loads and vibration signatures under controlled, wind tunnel environments for a range of flight conditions. • Develop novel techniques for control-oriented modeling. • Selectively flight test full-scale systems, measuring vibration signatures and damping levels at level and maneuvering flight conditions. • Innovate and employ active or passive techniques to minimize vibration and increase stability margin. • Develop MDAO techniques to develop low-vibration, stable systems. The SFW Project is doing substantial work on aspects of this challenge related to the engine and airframe. The Decadal Survey of Civil Aeronautics emphasizes the importance of load suppression, vibra- tion reduction, and aeromechanical stability control to rotorcraft. The reference document for the SRW

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 43 Project describes specific research tasks that would address these areas by developing and validating predictive tools, using experimental test facilities as needed. There is a strong focus on coupling CFD codes and computational structural dynamics codes to develop predictive capabilities and to validate these predictions through wind tunnel tests. The SRW Project does not plan to conduct the full-scale tests included in the milestones for this challenge. The Supersonics Project initially emphasizes aeroelastic approaches and controls for reducing gust loads and aeroelastic amplitudes as well as control strategies to eliminate low-frequency structural vibra- tions. The reduction of flutter and dynamic stresses is proposed for fiscal years (FY) 2010-2011. All of this is through the use of computer modeling. It is not clear how these techniques will be validated. The Hypersonics Project has no planned research to address the above milestones. C8  Structural innovations for high-speed rotorcraft SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   Y                 This R&T challenge has the following milestones: • Develop comprehensive aeromechanic analyses for high-speed rotorcraft that include tilt- rotor, tandem-rotor compound, and compound coaxial rotors for level and maneuvering flight conditions. • Develop aeromechanics and technology tools for the drive-train system and other key components necessary for variable-speed rotors. • Design and develop lightweight, crash-absorbing composite airframes. • Develop technology for all-weather rotorcraft operation. • Develop advanced composites with high damage tolerance for use in large dynamic structural components. • Reduce required shaft power by 15 percent from current levels using elastically tailored composite blades, active structural and flow control, and advanced airfoils. • Reduce life-cycle cost using health and usage management systems, low-cost tailored airframes, and lightweight low-vibration rotors. The SRW Project includes specific tasks to improve the integration and design of drive-train sys- tems, with an emphasis on variable and multispeed drive system technologies. It also includes ongoing research related to structural design for enhanced crashworthiness in rotorcraft structures. However, the SRW Project’s reference document does not address (1) development of tools for innovative new rotor- craft configurations (tilt-rotors, tandem compound rotors, coaxial compound rotors) or (2) reduction of life-cycle costs using health and usage monitoring of rotorcraft structures. C9  High-temperature ceramics and coatings SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y Y Y Y           Y This R&T challenge has the following near-term milestones: • Generate material property databases appropriate for design of a high-temperature ceramic component.

44 NASA AERONAUTICS RESEARCH—AN ASSESSMENT • Complete full-scale testing of at least one ceramic composite component with improved perfor- mance for subsonic aircraft applications (e.g., fairing heat shields, combustor liner, or turbine airfoil). • Develop models to optimize a structure for a new, rather than an existing, platform. • Model crack growth under actual operating conditions. • Develop advanced ceramic composites for large surfaces and leading-edge components for super- sonic and hypersonic vehicles and complete relevant environmental testing of subcomponents. This R&T challenge also has the following far-term milestones: • Flight test at least one ceramic composite component for improved subsonic flight vehicles and transfer the technology to industry. • Verify model predictions of performance using flight-test data. • Extend model predictions to new flight speed regimes to optimize supersonic and hypersonic vehicle designs for hot structures and engine components. • Demonstrate, through full-scale testing, at least one ceramic composite component for a super- sonic or hypersonic platform. The ceramics research by the SFW Project is inconsistent with the above milestones and will not provide timely results, particularly with respect to high-temperature requirements. NASA should con- sider teaming with the Air Force in this arena. The SRW Project plans to support some research in ceramics (in the form of ceramic matrix compos- ites). However, the SRW Project will not address the need for (1) more fabrication and testing experience with these materials and (2) a better understanding of their long-term behavior. The Supersonics Project includes development of metal/polymer composites in the near term. The development of ceramic matrix composites and ceramic barrier coatings is delayed until FY 2011. The Hypersonics Project in its Materials and Structures element contains many tasks for evaluation and modeling of materials and structures constructed from ceramic matrix composites for propulsion and airframe applications, but the Hypersonics Project does not include flight testing to validate these structures and materials. In the Aging Aircraft and Durability Project, CP-06 (Durability of Engine Superalloy Disks) and CP-07 ­(Durability of Engine Hot Section) address coatings relevant to this challenge, but at a low level of effort (2.9 labor-years for CP-06 and 1.5 labor years for CP-07) that limits the likelihood of producing significant and timely results. Furthermore, plans for the Aging Aircraft and Durability Project do not address the need for (1) more fabrication and testing experience with these materials and (2) a better understanding of their long-term behavior. C10  Multifunctional materials SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C Y black black black     Y       This R&T challenge has the following milestones: • Develop a comprehensive analysis to predict the performance of selected monolithic and com- posite multi­functional materials.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 45 • Use this analysis to guide parametric studies to explore and optimize material response with the goal of understanding the combined response of the multifunctional material. • Fabricate materials according to model predictions. • Evaluate material performance, both coupled and structural, and compare with analytical predictions. • Integrate multifunctional materials into a structural component for benchtop verification. • Conduct flight tests on a structural component. The SFW Project has a solid plan that addresses the above milestones. Progress reported to date, however, is inconsistent with the plan. Neither the SRW Project nor the Supersonics Project has planned research to address the above milestones. The Materials and Structures element of the Hypersonics Project contains tasks for design and evalu- ation of multifunctional ablator materials. The task appears limited in scope to one type of composite material, and the project does not include any flight testing of these structures and materials for valida- tion as specified in the R&T challenge. The IVHM Project is supporting research to develop self-healing materials. The research supports some aspects of the R&T challenge. The integration of sensors into multifunctional materials would help develop structures capable of prognostics. The development of energy harvesting systems to collect thermal energy from the propulsion system is a good application of thermoelectric materials. DYNAMICS, NAVIGATION, AND CONTROL, AND AVIONICS This section summarizes the committee’s assessment of NASA research related to the top 10 R&T challenges involving dynamics, navigation, control, and avionics (Area D) in the Decadal Survey of Civil Aeronautics (NRC, 2006). D1  Advanced guidance systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   Y     black black   Y     This R&T challenge has the following milestones: • Develop advanced algorithms and avionics for collision, terrain, and wake vortex avoidance; f ­ ormation flight and cooperative and multiaircraft guidance; and ground operations guidance (taxi, takeoff, rollout, and turnoff). • Expand facilities and programs capable of maturing the above technologies to flight-ready systems. • Develop and adopt regulations for the certification and operation of autonomous unmanned air vehicles (UAVs) in civil airspace. The reference document for the SRW Project includes goals related to the development of algorithms to avoid flight into terrain, particularly in all-weather operations. Plans for the SRW Project include research on precision guidance, navigation, and control capabilities for rotorcraft, although the refer- ence document states that limited resources will constrain related research to aspects of the program that provide an integrated solution to handling qualities and dynamics problems.

46 NASA AERONAUTICS RESEARCH—AN ASSESSMENT The Safe and Efficient Surface Operations element of the NGATS ATM-Airportal Project explores optimization of surface routing and the roles of pilots, controllers, and systems in surface operations. None of the other research planned by either the NGATS ATM-Airportal Project or the NGATS ATM- Airspace Project addresses the above milestones (or similar milestones for challenge D10 on the safe operation of UAVs in the national airspace). The Adaptive Intelligent Information Management task of the Integrated Intelligent Flight Deck (IIFD) Project is addressing advanced onboard guidance. However, most of the onboard guidance research supported by ARMD is conducted by the NGATS ATM-Airspace Project. For example, this research includes the generation of aircraft trajectories using algorithmic methods. The IIFD Project is conducting research to improve pilots’ situational awareness by providing them with information about the trajectories of aircraft in their aircraft’s critical volume, so they can make appropriate spacing decisions. The IIFD Project anticipates providing its results to various government organizations, including the DoD. However, the IIFD Project has not considered the advances that DoD has made in integrated display systems in its most recent fighter aircraft, the F-22 and F-35. These systems integrate information from multitudes of sensors on the aircraft, on the ground, and on other aircraft. This directly relates precisely to issues that the IIFD Project is addressing, such as information quality and uncertainty, decluttering, and general spatial integration of information. D2  Distributed decision making, decision making under uncertainty, and flight-path planning and prediction SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   black     Y       This R&T challenge has the following milestones: • Develop simulation capabilities for evaluation and demonstration of certain high-performing strategies in the execution of realistic system architectures and applications. • Develop a requirements flowdown to all affected aircraft systems, such as advanced communica- tions, navigation, and surveillance systems. • Develop improved, automated logic and processes for contingency management. • Develop a methodology to support verification and validation of future systems technologies developed by this challenge. Although the SRW Project includes a system-level milestone on Control Theory, Intelligent/Autono- mous Systems, Information Processing, and Modeling, related research does not relate to the fundamental thrust of this R&T challenge as it relates to rotorcraft, which is to add autonomy and automatic controls to improve integration of rotorcraft in the air traffic management system. The Safe and Efficient Surface Operations element of the NGATS ATM-Airportal Project explores optimization of surface routing and the roles of pilots, controllers, and systems in surface operations. The role of people in decision making is addressed in the Airportal Transition and Integration Management element, which is developing a human performance model for the roles of pilots, controllers, airport ground personnel, and others. This effort is examining the allocation of roles between humans and automation. In addition, the Coordinated Approach/Departure Operations Management element of the NGATS ATM-Airportal Project is examining Required Navigation Performance and four dimensional (4-D) trajectories for improved runway throughput.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 47 The Traffic Flow Management, Super Density Operation, and Trajectory Prediction, Synthesis, and Uncertainty elements of the NGATS ATM-Airspace Project address the first and third milestones for this R&T challenge (see above). This research is also well aligned to the stated needs of the NextGen System (as of September 2007). The planned research should advance the state of the art, but timely undertaking of substantive research by the Super Density Operations and Trajectory Prediction elements is compromised by a shortage of qualified and experienced staff. The IIFD Project is addressing important elements of this R&T challenge, but the research would be more effective if it did a better job of taking into account work that DoD has performed in this area. (See discussion under D1, above.) D3  Aerodynamics and vehicle dynamics via closed-loop flow control SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C black black Y               This R&T challenge has the following milestones: • Develop simpler representations of the aircraft system dynamics for control design. • Develop distributed control algorithms and architectures. • Demonstrate the ability to numerically solve distributed control algorithms at the Reynolds num- bers associated with manned aircraft flight to demonstrate control performance. • Implement integrated, distributed closed-loop flow-control systems. • Design and develop lightweight, mechanized, shape-changing structures. • Experimentally verify the performance of shape-changing aerodynamic structures before flight testing. The SFW Project includes research and flight testing of shape-changing structures, but it does not include substantial work on the other elements of this challenge. The focus of this challenge is on using distributed sensors and actuators to provide flow control over a wide range of flight operations. The SRW Project does not effectively address this goal. The Supersonics Project includes research related to this challenge, but it is focused mostly on developing and testing computational codes, and it is not applying those tools to develop and predict the performance of notional aircraft configurations. D4  Intelligent and adaptive flight control techniques SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   Y               This R&T challenge has the following milestones: • Develop an adaptive, intelligent, fully integrated vehicle management system that can operate safely without reliable sensor information. • Demonstrate a mature methodology for designing and analyzing flight control laws for aircraft with large numbers of highly distributed control actuators and sensors—for example, shape memory alloys and piezoelectrics. • Demonstrate a mature methodology for using information of different degrees of reliability

48 NASA AERONAUTICS RESEARCH—AN ASSESSMENT without compromising flight safety (e.g., using data from what would traditionally be considered non-flight-critical systems within an inner control loop). • Demonstrate long-term learning so that adaptation would only need to be used in novel situations. For example, following damage, the system adapts the first time it enters a particular part of the flight envelope but does not need to readapt if it leaves that part of the envelope and returns. • Validate complex nonlinear systems to seek out worst-case scenarios that may not be identified with exhaustive testing. Intelligent and adaptive flight control techniques require that vehicle systems be highly integrated. The reference document for the SRW Project describes research related to this challenge, but it does not directly address the above milestones. The most important rotorcraft-unique aspect of this challenge is the first milestone, and the plans for the SRW Project includes research that supports that milestone. The Integrated Dynamics and Flight Control, Integrated Propulsion Control and Dynamics, and Airframe and Structural Dynamics elements of the Integrated Resilient Aircraft Control (IRAC) Project address key aspects of this challenge for fixed-wing applications. The research in question will investigate the integration of (1) engine and actuator health data and (2) structural degradation and damage. This research would also integrate propulsive and aerodynamic controls to optimize flight performance in damaged and degraded conditions. NASA assets such as simulation facilities, the scale-model transport testbed, and aircraft at Dryden Flight Research Center would be used to support full-scale validation of the concepts produced by this research. D5  Fault-tolerant and integrated vehicle health management systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   black         Y   This R&T challenge has the following milestones: • Specify nominal models and model behavior, interface, and test requirements for component and integrated system capability affected by degraded or failed operation of a representative subset of avionics and flight system components. Define suitable thresholds for levels of degraded and failed operation for component-level and system-level operations. • Work with aircraft subsystem and flight system vendors to specify parameters that are candidates for maintenance logging. Develop models and compact representations that can incorporate measurements of these parameters in near real time and develop thresholds that can be used for on-demand maintenance activities. • Evaluate component capability in a simulated environment (ground test and hardware in the loop). That is, take a particular subsystem, such as a real landing gear system that has been represented by an appropriate behavioral model as specified, and insert simulated faults to test for proper operation of the health monitoring system. Perform these tests for all representative subsystems that were specified above. • Evaluate integrated system capability in a simulated environment. Take the subsystem health models previously specified and insert faults, preferably ones that were not detected as quickly as necessary by the individual component models that were evaluated in the above set of tests, and use the system models in order to evaluate the efficacy of their integrated operation. • Test component and integrated system capability in a flight environment.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 49 The IVHM, IIFD, and IRAC Projects are generally addressing this challenge as it pertains to fixed- wing applications, and it is somewhat premature to address this challenge as it pertains specifically to supersonic and hypersonic aircraft. The reference document for the SRW Project describes research related to this challenge, although issues related to fault detection, isolation, and reconfiguration of control are not explicitly pursued. The IVHM Project is maturing health monitoring technologies related to structures, propulsion, and aircraft systems. It is developing assessment and prognostic capabilities for detecting airframe and pro- pulsive structure faults using in situ sensors. The IVHM Project is developing high-temperature silicon carbide sensors for the propulsion system hot gas path. It is also studying the management and mitiga- tion of icing- and lightning-related issues that relate to IVHM. Sensors, algorithms, and approaches are being developed for assessing landing gear, wings, propulsion systems, and power systems. The integra- tion of these technologies, to form a “big picture” approach to vehicle health management, has been an elusive goal to date. The Decadal Survey is very clear on the need to integrate the health management functions of individual systems, and the IVHM Project is addressing this goal through the use of novel data mining techniques. The External Hazard Detection and Classification element of the IIFD Project directly addresses fault tolerance. The Adaptive Information Management element of the IIFD Project supports research related to vehicle health to address vehicle situational awareness, along with the IVHM and IRAC Projects (see below), but the integration of these efforts is left to the researchers involved in the various efforts. The IRAC Project is effectively and directly addressing fault tolerance due to structural anomalies and control actuation failures or degradation by integrating propulsion control and aerodynamic control in an adaptive control architecture. Fault tolerance after adaptation is enhanced by integrating a replan- ning function that considers the reduced functionality of the aircraft. D6  Improved onboard weather systems and tools SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         black black   Y     This R&T challenge has the following milestones: • Develop robust and reliable data links for collecting information from onboard sensors. • Develop processes and tools for integrating weather information from onboard sensors and data links to the ground and other aircraft. • Demonstrate effectiveness in practical decision-support applications relating to weather, with varying levels of information quality and uncertainty. Neither the NGATS ATM-Airportal Project nor the NGATS ATM-Airspace Project has planned research to achieve aspects of the above milestones related to in-flight applications. The External Hazard Detection and Classification element of the IIFD Project is researching sensor suites for detection of adverse weather and obstacle avoidance while also investigating how best to display these data. This research is also addressing the feasibility of fusing alternative data sources that provide data on turbulence, icing conditions, and other weather-related phenomenology, and it is addressing display capabilities for runway incursion detection and obstacles in the air, such as thin wires. However, the IIFD Project does not include data link research.

50 NASA AERONAUTICS RESEARCH—AN ASSESSMENT D7  Advanced communication, navigation, and surveillance technology SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   black     black black black       This R&T challenge has the following milestones: • Simulate avionics on an individual aircraft to determine the capability of each avionics function (communication, navigation, guidance, control, and surveillance). • Demonstrate (1) fault-tolerant degradation of communications, navigation, and surveillance capa- bility (in terms of accuracy and availability of modes) and (2) processes needed to ensure that the individual aircraft can still transmit the needed aircraft state information and receive information and air traffic control commands with an extremely low probability of communication error. • Evaluate different tracking and control algorithms with various faults that could occur in either the ATM system or airborne aircraft to determine whether the algorithms are able to detect the faults, identify them, and recover from them by reconfiguring the system in which the fault occurred as well as other systems to provide a satisfactory level of service. • Document the feasibility of using space-based communications and surveillance as both a primary and backup means of ATM. • Demonstrate modeling and real-time simulation using distributed control centers and different traffic levels, ranging from the current peak hourly load of about 6,000 airborne aircraft in the continental U.S. airspace to a predicted hourly load of 18,000 airborne aircraft, using current demand patterns. This effort is required to verify that the network of communication links, pro- cessing nodes in the network, and control algorithms provides the desired capacity while satisfying safety criteria. • Demonstrate a means to provide seamless information flow between an aircraft’s multiband antenna and the fiber-optic local area network that manages the information flow between aircraft systems and the radio channels. • Demonstrate a robust IVHM system that detects permanent and transient onboard system faults and communicates system status to pilots and ground systems. • For aircraft equipped with autothrottles, develop performance algorithms linked to aircraft dynam- ics to maintain the approved flight trajectory while minimizing fuel consumption. For aircraft that are not equipped with autothrottles, document the information required by the flight management system to generate speed commands to be displayed to pilots while minimizing pilot workload. • Develop an air-ground communication protocol that (1) optimally allocates functions among pilots, avionics, air traffic controllers, and automated ground systems and (2) includes a means to alert ground systems and controllers that the data link or an onboard system has failed. This will require control algorithms that can handle multiple failures in terms of controlling the air- craft with the failures as well as adjacent traffic to minimize the impact on airspace capacity and efficiency. Neither the NGATS ATM-Airportal Project, NGATS ATM-Airspace Project, nor IVHM Project has planned research to address the above milestones, and the SRW Project is not supporting research to address rotorcraft-specific aspects of this challenge.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 51 D8  Human–machine integration SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C   black           This R&T challenge has the following milestones for human–machine integration methods and tools: • Develop improved system engineering processes and tools for determining optimum roles of humans and automation in complex systems and demonstrate the benefits of this improved methodology in a trial application. This milestone should include provisions for dynamic human– machine task allocation and monitoring of human performance by machines (e.g., automated terrain avoidance). • Conduct fundamental research on the causes of human error and on human contributions to safety and document design guidelines that will (1) help minimize the potential for design-induced error and (2) facilitate­ positive human intervention in the event of system failures. Transfer these guidelines to government program offices and industry. • Develop constructive models of human performance and decision making and validate model predictions against objective performance data acquired in high-fidelity human-in-the-loop flight simulation experiments. • Develop and demonstrate rapid prototyping tools that enable comparative evaluations of alterna- tive automation schemes early in system development. • Develop and validate a technique for integrating human reliability estimates into system safety and reliability analyses. This R&T challenge also has the following milestones for human–machine integration technologies for vehicle applications: • Develop and test enabling technologies for pilot workload management and reduced crew opera- tions (e.g., improved human–machine integration for a flight management system) while keeping pilot awareness at the proper level. • Develop display concepts for maintaining operator situational awareness while monitoring highly automated processes. Demonstrate the ability of operators to rapidly and accurately intervene in the event of system failures. • Develop technologies and/or display concepts enabling effective fusion of information from mul- tiple sources, including real-world and synthetic imagery (i.e., augmented reality). Demonstrate the effectiveness of these concepts in practical decision-support applications with varying levels of information quality and uncertainty (in terms of accuracy, timeliness, etc.). • Develop and demonstrate technologies for machine vision (image-based object detection). • Develop tools and metrics to compare effectiveness of machine and human operators in see-and- avoid tasks to improve machine performance. The SRW Project is addressing some rotorcraft-specific aspects of human–machine interaction issues, but it does not include research to develop processes and tools to determine the appropriate balance between human operations and automation. Instead, existing research is focused on control methods to reduced pilot workload.

52 NASA AERONAUTICS RESEARCH—AN ASSESSMENT The Airportal Transition and Integration Management element of the NGATS ATM-Airportal Proj- ect substantially addresses the above milestones, particularly with regard to the allocation of roles and responsibilities between humans and machines as it applies to airport and terminal area systems and operations. The NGATS ATM-Airspace Project includes separation assurance research to facilitate development of automated separation using a service provider approach. This research includes human situational awareness with automated systems through simulations, and it aligns with the above milestone to develop constructive models of human performance. The Automation Monitoring and Failure Mitigation element and the Operator State Monitoring and Classification element of the IIFD Project include a very strong effort to investigate dynamic human–automation task allocation and to develop tools to measure the benefits of specific allocations and identify the causes of human error. D9  Synthetic and enhanced vision systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C                   This R&T challenge has the following milestones: • Prepare an accurate and complete terrain and obstacles database and demonstrate real-time data- base monitoring and error correction. • Develop procedures and rules for fusing image information from multiple imaging sensors as well as stored terrain data and traffic; identify common viewing parameters; and determine what role enhanced vision systems and synthetic vision systems should play in an integrated system. • Demonstrate increased situational awareness and alerting to avoid air traffic, airport surface traf- fic, wires, and cables. • Demonstrate displays that (1) eliminate image fusion artifacts that lead to misleading informa- tion and (2) present conformal information to pilots in a way that facilitates its transition to the outside world. • Demonstrate tools for verifying database accuracy, fault tolerance, reliability, and overall system accuracy. The External Hazard Detection and Classification element of the IIFD Project contributes to the development of synthetic and enhanced vision systems. Relevant research would provide the capability to maneuver in poor visibility on the ground and in the air (e.g., to support approach and landing opera- tions on parallel or converging runways). This research also supports development of integrated displays of terrain and weather using onboard and external sensors and data sources. D10  Safe operation of unmanned air vehicles in the national airspace SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         black black     black   This R&T challenge has the following milestones: • Develop and demonstrate secure, reliable communications as well as procedures for interaction between UAVs and air traffic controllers.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 53 • Design, develop, and demonstrate human interfaces for remote UAV operators under conditions extant in the air transportation system. • Develop and test training programs for remote UAV operators. • Develop and demonstrate sense-and-avoid technologies for UAVs. • Demonstrate technologies for maintaining positive control of UAVs under adverse conditions. • Develop and demonstrate automated contingency management for control of UAVs. Neither the NGATS ATM-Airportal Project, NGATS ATM-Airspace Project, nor the IRAC Project has planned research to address the above milestones. INTELLIGENT AND AUTONOMOUS SYSTEMS, OPERATIONS AND DECISION MAKING, HUMAN INTEGRATED SYSTEMS, AND NETWORKING AND COMMUNICATIONS This section summarizes the committee’s assessment of NASA research related to the top 10 R&T challenges involving intelligent and autonomous systems, operations and decision making, human inte- grated systems, networking, and communications (Area E) in the Decadal Survey of Civil Aeronautics (NRC, 2006). E1  Methodologies, tools, and simulation and modeling capabilities to design and evaluate complex interactive systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         Y  Y   Y    This R&T challenge has the following milestones: • Demonstrate methodologies and tools for the design, test, and certification of a flexible, robust, safe air transportation system that is readily adaptable to changing operational paradigms suited to new and different vehicles, including UAVs, very light jets, and spacecraft operating in civil air- space; communications, navigation, and surveillance capabilities; and optimization techniques. • Demonstrate a flexible ATM model that incorporates the performance characteristics and limita- tions of the wide mix of present and future aircraft arriving, departing, and operating within air- space surrounding major hub airports. This model should be capable of analyzing the impacts of (1) aircraft mix and (2) operator and controller decision making and actions on system efficiency and capacity. • Demonstrate the ability of an enhanced version of the model to assess the impact of regional weather phenomena, such as convective activity, snow, and high winds. • Demonstrate the capability to test and certify nondeterministic systems. • Demonstrate the ability of an enhanced version of the ATM model to assess impacts of aircraft mix and operator and controller decision making. The NGATS ATM-Airportal Project is a contributor to and user of simulation facilities and labora- tories operated by NASA. Plans for the Coordinated Approach/Departure Operations Management ele- ment of the project include research to produce a suite of concepts and technologies that can be tailored to specific airports. In addition, plans for the Safe and Efficient Surface Operations element include research to develop and validate a surface 4-D trajectory model. Simulation and modeling underpin most of the work by this project.

54 NASA AERONAUTICS RESEARCH—AN ASSESSMENT The Performance Based Services element and the System-Level Design, Analysis, and Simulation Tool element of the NGATS ATM-Airspace Project substantially address most of the above milestones. Research in several other Airspace elements also supports this challenge, although none of the planned work specifically addresses unmanned air vehicles or spacecraft operating in civil airspace. In some cases, resource limitations, including the availability of sufficient in-house expertise, will make it dif- ficult to achieve milestones in a timely fashion. The IRAC and IVHM Projects have plans to address the milestone regarding the testing of nonde- terministic systems. The IRAC Project plans to conduct laboratory and flight tests of nondeterministic systems at Dryden Flight Research Center, although not until late in the current 10-year plan. Related work by the IVHM Project will piggyback on the IRAC flight tests at Dryden. E2  New concepts and methods of separating, spacing, and sequencing aircraft SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         Y Y         This R&T challenge has the following milestones: • Demonstrate high-efficiency airspace and airway structures that can be effectively managed and understood. • Design and evaluate separation, spacing, and sequencing procedures for UAVs operating in civil- ian airspace and assess their impact on commercial aircraft capacity and safety. • Extend models and simulation tools to enable accurate evaluation of emerging technologies (e.g., the Automatic Dependent Surveillance-Broadcast system) in all weather conditions and during all phases of flight. • Complete an in-depth examination of the ability of concepts such as runway-independent aircraft and UAV formations or swarms to safely increase capacity and accommodate nontraditional aircraft operations. • Demonstrate advanced, autonomous collision avoidance technologies and protocols. Plans for the Safe and Efficient Surface Operations element of the NGATS ATM-Airportal Project address surface scheduling and taxi routes. Plans for the Coordinated Approach/Departure Operations Management element include research to study vortex avoidance, and runway balancing, assignments, and self-spacing may be addressed in the future. Plans for the Airportal Transition and Integration Man- agement element also foresee including research on metroplex operations (i.e., areas with two or more airports in close proximity) in the future. The Separation Assurance and Super Density Operations elements of the NGATS ATM-Airspace Project address each of the above milestones except for those related to unmanned air vehicles operating in civil airspace. Ongoing work related to this challenge is likely to advance the state of the art, but avail- able resources will make it difficult to achieve milestones in a timely fashion. None of the planned work specifically addresses unmanned air vehicles.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 55 E3  Appropriate roles of humans and automated systems for separation assurance, including the feasibility and merits of highly automated separation assurance systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         Y Y         This R&T challenge has the following milestones: • Complete basic research necessary to determine the most appropriate separation assurance roles for humans and automation, for ground-centered and aircraft-centered designs. • Complete the development of the NASA Ames Advanced Airspace Concept, an automated ground-based separation assurance system, for the en route domain. • Determine how humans interact with the Advanced Airspace Concept and other automation designs. • Determine how the Advanced Airspace Concept and other designs respond to air and/or ground automation failures, or when the flight crew fails to respond to automated directives. • Develop an adaptation of the Advanced Airspace Concept or other designs for UAVs, and deter- mine its performance. • Determine through analysis and simulation the safety of the Advanced Airspace Concept and other designs. The Airportal Transition and Integration Management element of the NGATS ATM-Airportal Project includes a substantial, well-conceived effort to address human–system integration as it applies to the complex airportal domain. However, plans for the Coordinated Approach/Departure Operations Man- agement element have pushed the investigation of high-density operations and separation assurance in airport and terminal areas well into the future. The Separation Assurance and Super Density Operations elements of the NGATS ATM-Airspace Project include research on the roles of humans and automated systems, but this is not a key focus of these elements. Ongoing work related to this challenge would advance the state of the art, but available resources will make it difficult to achieve milestones in a timely fashion. None of the planned work specifically addresses unmanned air vehicles. E4  Affordable new sensors, system technologies, and procedures to improve the prediction and measurement of wake turbulence SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         black black         This R&T challenge has the following milestones: • Demonstrate new sensors, including a scientific, coherent lidar capable of accurate wake velocity strength measurements. • Conduct phenomenological studies of wake behavior supported by field experiments using ground-based sensor(s) that measure wake decay and atmospheric conditions at altitudes up to 8,000 feet above the ground.

56 NASA AERONAUTICS RESEARCH—AN ASSESSMENT • Determine aircraft upset risks from wake vortices encounters, taking advantage of existing models and enhancing them where needed with field data. • Demonstrate procedures, monitoring equipment, and other systems to safely reduce wake separation. • Demonstrate an airborne means to sense and quantify the intensity of hazardous wakes en route in time for aircraft to evade them. Plans for the Coordinated Approach/Departure Operations Management element of the NGATS ATM- A ­ irportal Project include exploration of “wake aware” procedures. However, the Airportal Project views wake vortex issues as one of many constraints on runway, airport, and terminal area capacity, and the scope of this research has been reduced in recent years. NASA does not plan to develop or demonstrate new sen- sors or sensor technologies. NASA plans to rely on the National Oceanic and Atmospheric Administration and the FAA to take the lead in research related to the determination and characterization of weather and hazards such as wake vortices. The NGATS ATM-Airportal Project is supporting foundational research (e.g., mathematical and statistical characterization) to support some of the above milestones, but these activities are not planning to proceed to the point of achieving the above milestones. The resulting work would be handed off to the National Oceanic and Atmospheric Administration and the FAA. The NGATS ATM-Airspace Project has no planned research to address the above milestones. E5  Interfaces that ensure effective information sharing and coordination among ground-based and airborne human and machine agents SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         Y         This R&T challenge has the following milestones: • Document improved understanding of human cognitive control, judgment, and decision making in a variety of contexts and under a variety of stressors. • Document improved understanding of organizational dynamics and business concerns associated with information sharing. Plans for the Safe and Efficient Surface Operations element of the NGATS ATM-Airportal Project include research on multiagent decision making and trajectory conformance for surface operations. Plans for the Coordinated Approach/Departure Operations Management element include the study of 4-D tra- jectory conformance and investigation of separation assurance in super density situations. Plans for the Airportal Transition and Integration Management element also include investigation of human–system integration issues associated with this domain. Plans for the Separation Assurance and Super Density Operations elements of the NGATS ATM- Airspace Project include substantial research on humans-in-the-loop information sharing. However, research by the Airportal and Airspace projects will not address the milestone on organizational dynam- ics and business concerns. Another concurrent National Research Council study is focused exclusively on NASA’s wake vortex research. The results of that study were not available in time to factor them into this report.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 57 E6  Vulnerability analysis as an integral element in the architecture design and simulations of the air transportation system SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         black Y         This R&T challenge has the following milestones: • Complete end-to-end vulnerability analysis of system architecture and signal flow. • Demonstrate the ability of a more capable model to simulate critical element disruptions as defined by vulnerability analyses. • Document safety and capacity impacts using modified system simulations. • Develop changes in system architecture and operational procedures and demonstrate that they can mitigate the effects of specific system disruptions. The NGATS ATM-Airportal Project is monitoring relevant work being done by the NGATS ATM- Airspace Project, but it has no planned research to address the above milestones. The NGATS ATM-Airspace Project does not contemplate development of a complete end-to-end vulnerability analysis or changes in system architecture and operational procedures. Plans for the Sepa- ration Assurance and Super Density Operations elements include modeling work that would factor in system disruptions. This research would advance the state of the art, but available resources will make it difficult to achieve milestones in a timely fashion. E7  Adaptive ATM techniques to minimize the impact of weather by taking better advantage of improved probabilistic forecasts SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         Y Y         This R&T challenge has the following milestones: • Identify potential reductions in weather-induced delays. • Demonstrate use of automated weather forecasts in making traffic flow decisions. • Quantify the benefit of using automated weather forecasts in making traffic flow decisions. • Determine where this capability is cost-beneficial. The NGATS ATM-Airportal Project is very attuned to the need for adaptive ATM techniques. Plans for the Safe and Efficient Surface Operations element include research to develop surface optimiza- tion schemes that would continually adapt to produce the optimal result. Plans for the Coordinated Approach/Departure Operations Management element include research to study the effect of weather on wake vortex behavior and, in the future, to develop better approaches for runway balancing and reconfiguration and for equivalent visual operations (which would allow aircraft to operate regardless of visibility conditions or the ability to make direct visual observations). The Airportal Transition and Integration Management element also foresees including research on metroplex operations in the future. The NGATS ATM-Airportal Project is not performing cost-benefit analyses.

58 NASA AERONAUTICS RESEARCH—AN ASSESSMENT The Traffic Flow Management element of the NGATS ATM-Airspace Project seeks to develop models to forecast demand and capacity of the National Airspace System that respond effectively to weather uncertainties. Assuming success, these models could help to identify potential reductions in weather-induced delays. It does not appear, however, that the remainder of the challenge milestones are planned to be addressed. E8a  Transparent and collaborative decision support systems SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C                 This R&T challenge has the following milestones: • Identify the type of information to be shared between human operators and automated decision- support systems and the most appropriate form of information representation and exchange. • Develop, demonstrate, evaluate, and iteratively refine candidate designs in collaboration with operators. Plans for the Safe and Efficient Surface Operations element of the NGATS ATM-Airportal Project include substantial work to develop concepts for decision-support methodologies and tools applicable to surface operations. Plans for the Traffic Flow Management element of the NGATS ATM-Airspace Project include research to address both of the above milestones. This research would likely advance the state of the art and produce timely results. E8b  Using operational and maintenance data to assess leading indicators of safety SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C               Y This R&T challenge has the following milestones: • Produce a common taxonomy for all safety information acceptable to all stakeholders. • Demonstrate methodologies to discover and analyze anomalous system, components, and human behavior in nominal and off-nominal conditions. • Demonstrate methods to integrate system models into analytical processes. • Demonstrate advanced, affordable methods to analyze anecdotal written reports of safety prob- lems and cross-reference them to operational data from aircraft, ATM, and weather systems. • Demonstrate methods to cross-reference operational data to certification and training simulator data to determine if aircraft are performing as designers intended and if pilots and controllers are performing as trained. The IVHM Project plans to support extensive research in data mining and analysis of aircraft main- tenance records as well as operational data. This information would be fused with sensor data from the vehicle airframe; the IVHM Project is working with the IIFD Project to assess integration of this work into the cockpit.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 59 Plans for each of the eight challenge problems being addressed by the Aging Aircraft and Durability Project include research to help create a database that would provide better indicators of safety. However, the challenge problems do not directly discuss maintenance, and it seems unlikely that planned research will have a significant and timely impact without additional resources and the involvement of personnel experienced with airline maintenance and operations. E8c  Interfaces and procedures that support human operators in effective task and attention management SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C         black         This R&T challenge has the following milestones: • Complete basic research to document how operators absorb information, process information, and prioritize tasks. • Demonstrate tools to efficiently evaluate operational data and reports of nominal and off-nominal decision making by operators. • Demonstrate and evaluate candidate designs and procedures in support of preattentive reference, time-­sharing among different tasks, and task switching. The Airportal Transition and Integration Management element of the NGATS ATM-Airportal Project includes an in-depth and comprehensive research effort to address the role of humans. The NGATS ATM-Airspace Project has no planned research to address the above milestones except as a by-product of the research by the Separation Assurance and Super Density Operations elements. SPACE AND NON-CIVIL AERONAUTICS RESEARCH In addition to the civil aeronautics R&T challenges detailed above, the committee for this study identified two high-priority requirements for NASA aeronautics research based on NASA’s own require- ments for aeronautics research (including robotic and human space exploration) and the needs of other federal government departments and agencies for non-civil aeronautics research. S-1  Entry, descent, and landing on Mars (e.g., high-Mach-number parachutes) and Earth (ablative materials) SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C The Supersonics Project is supporting computational and experimental investigations of aerother- modynamics issues associated with entry, descent, and landing, as well as studies of supersonic aero- dynamic decelerators. Preattentive reference is supported by presenting partial information about a potentially interrupting task or event to help the operator decide whether a shift in attention is warranted. The information needs to be presented in such a way that it is quickly noticed and easily processed and understood without requiring an interruption of the ongoing task or line of reasoning (Woods, 1995). Operational systems that provide preattentive reference reduce the risk of task switching errors and improve operator efficiency and performance.

60 NASA AERONAUTICS RESEARCH—AN ASSESSMENT The Hypersonics and Supersonics Projects both include research that supports robotic and human space exploration. The study of High Mass Mars Entry Systems constitutes about 25 percent of the Hypersonics Project. This effort is conducting fundamental research on issues related to landing high- mass payloads on Mars. Issues of interest include increased levels of turbulent and radiative heating caused by a larger entry capsule and the need for increased precision in landing accuracy. Relevant research is incorporated in the Aerodynamics, Aerothermodynamics, and Plasmadynamics; Materials and Structures; and Guidance, Navigation and Control elements of the Hypersonics Project, and it includes development of CFD analysis tools, experimental investigations, aerothermodynamics modeling, materi- als for thermal protection, and trajectory analysis. S-2  Core competencies (facilities and staff) for space (e.g., for access to space, entry, descent, and landing, and analysis of space shuttle anomalies) and for DoD (hypersonic vehicles) SFW SRW Supersonics Hypersonics Airportal Airspace IVHM IIFD IRAC Aging A/C NASA’s Exploration Systems Mission Directorate, Science Mission Directorate, and Space Opera- tions Mission Directorate all support important space activities. As noted above, in some cases NASA space programs rely on the NASA Aeronautics Program to sponsor research tasks of direct benefit to future space programs. In other cases, research, development, and operational elements of the space program rely on NASA aeronautics to support space research tasks by providing access to aeronautical staff and facilities. In addition, elements of the Department of Defense often rely on NASA Aeronautics to provide support, in the terms of key staff expertise and/or facilities, to support DoD research and development tasks. (It is much rarer for the DoD to ask NASA to conduct a research project on behalf of the DoD.) The chief scientist of the Air Force and the DARPA director report that they are satisfied with the coop- erative support that NASA currently provides. Interactions with DARPA have focused on the four projects that make up the Fundamental Aero- nautics Program. Ongoing and recently completed collaborations include the following: • Subsonic Fixed Wing Project — DARPA Morphing Wing • Subsonic Rotary Wing Project — Helicopter Quieting Program — SMART Rotor Program — Heliplane — Acoustic flight tests at Eglin Air Force Base (co-sponsored with the Air Force Army) — Helicopter Brownout (co-sponsored with Air Force) • Supersonics Project — Oblique Flying Wing Program • Hypersonics Project — X-51 (1, 2, 3, 4) (co-sponsored with the Air Force) — Falcon — HyFly (co-sponsored with the Navy) See Chapter 3 for a detailed discussion of aeronautical facilities.

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 61 With many of the above projects, NASA subject-matter experts assist DARPA in the formulation of programs, review of proposals, and periodic program reviews. In addition, NASA subject-matter experts often use NASA test facilities (e.g., wind tunnels, flight-test operations, and propulsion test facilities) to support of DARPA programs. In some cases, NASA research in support of DARPA proj- ects is funded by DARPA, and in other cases NASA contributes its own resources to support research of mutual benefit. ASSESSMENT OF NASA’S RESPONSE TO RECOMMENDATIONS IN THE DECADAL SURVEY OF CIVIL AERONAUTICS The Decadal Survey of Civil Aeronautics made eight recommendations (NRC, 2006, p. 3). The committee’s assessment of NASA’s response to these recommendations is summarized below. Recommendation 1 from the Decadal Survey NASA should use the 51 Challenges listed in Table ES-1 as the foundation for the future of NASA’s civil aeronautics research program during the next decade. Assessment of NASA Response. The content of the Decadal Survey of Civil Aeronautics seems not to have been a significant factor in the selection of the research portfolio being pursued by many of the ARMD’s research projects. The basic planning documents for most of NASA’s research projects were prepared before the Decadal Survey was published, and the NASA research portfolio, as a whole, does not seem to have changed course in response to the Decadal Survey. In any case, as detailed above, NASA is doing a mixed job in responding to the R&T challenges overall and in each R&T challenge area. As discussed in Chapter 4, addressing all 51 ­highest-­priority R&T challenges from the Decadal Survey in a thorough and comprehensive manner would require a substantial increase in the NASA ARMD funding levels. Absent such an increase in funding and/or a substantial reduction in the constraints that NASA faces in conducting aeronautics research, NASA, in consultation with the aeronautics research com- munity and others as appropriate, should redefine the scope and priorities of the aeronautics research program, even if all 51 of the highest-priority R&T challenges from the Decadal Survey of Civil Aero- nautics are not addressed simultaneously. Recommendation 2 from the Decadal Survey The U.S. government should place a high priority on establishing a stable aeronautics R&T plan, with the expectation that the plan will receive sustained funding for a decade or more, as necessary, for activities that are demonstrating satisfactory progress. Assessment of NASA Response. NASA leadership issued a new vision for aeronautics research in early 2006, in the context of an agency vision that remains focused on space. For the next 2 years, NASA was consistent in advocating a research program that is stable, year to year, in carrying out the vision. However, changes in direction often occur with a change in leadership, and the associate administrator for ARMD who oversaw the creation and implementation of this vision left NASA in February 2008. It remains to be seen if the appointment of a permanent replacement will result in another change in NASA’s vision and/or priorities for aeronautics research. These 51 challenges are listed in Table 1-1 in Chapter 1 of the present report.

62 NASA AERONAUTICS RESEARCH—AN ASSESSMENT Recommendation 3 from the Decadal Survey NASA should use five Common Themes to make the most efficient use of civil aeronautics R&T resources: • Physics-based analysis tools • Multidisciplinary design tools • Advanced configurations • Intelligent and adaptive systems • Complex interactive systems Assessment of NASA Response. NASA has addressed the recommended common themes with different levels of success. NASA is doing well, in most cases, with physics-based analysis tools and multidisciplinary design tools. NASA is doing good work on advanced configurations for subsonic fixed- wing aircraft and, to a lesser extent, on hypersonic aircraft. It is not doing noteworthy work on advanced configurations for supersonic aircraft or rotorcraft. A stronger focus on systems and systems integration is necessary to strengthen research related to advanced configurations, intelligent and adaptive systems, and complex interactive systems. Recommendation 4 from the Decadal Survey NASA should support fundamental research to create the foundations for practical certification standards for new technologies. Assessment of NASA Response. In many cases, NASA is supporting fundamental research that could ultimately be used to create foundations for practical certification standards for future technolo- gies, but it is not conducting research specifically focused on certification issues. In addition, proce- dures for transferring new technologies are not apparent. However, Section 905 of H.R. 2881, the FAA Reauthorization Act of 2007, would direct the “FAA, in consultation with other agencies as appropri- ate” to “establish a research program on methods to improve both confidence in and the timeliness of certification of new technologies.” The same bill would direct the FAA to prepare a research plan for this activity and to have the plan reviewed by the National Research Council. As of October 19, 2007, the bill had passed the House of Representatives and was awaiting action by the Senate. Recommendation 5 from the Decadal Survey The U.S. government should align organizational responsibilities as well as develop and implement techniques to improve change management for federal agencies and to assure a safe and cost-effective transition to the air transportation system of the future. Assessment of NASA Response. Recommendation 5 is not directed at NASA, and it is beyond the scope of NASA’s authority. This committee is not aware of any action to implement this recommenda- tion (beyond the ongoing work of the NextGen Joint Planning and Development Office).

CHALLENGES AND REQUIREMENTS FOR NASA AERONAUTICS RESEARCH 63 Recommendation 6 from the Decadal Survey NASA should ensure that its civil aeronautics R&T plan features the substantive involvement of universities and industry, including a more balanced allocation of funding between in-house and external organizations than currently exists. Assessment of NASA Response. The Decadal Survey of Civil Aeronautics reported that ARMD had plans to allocate only 7 percent of its budget for research by outside organizations. NASA is gradually increasing the involvement of universities and industry in ARMD research projects using NRAs. This percentage varies among the projects from 10 percent to more than 40 percent.  Recommendation 7 from the Decadal Survey NASA should consult with non-NASA researchers to identify the most effective facilities and tools applicable to key aeronautics R&T projects and should facilitate collaborative research to ensure that each project has access to the most appropriate research capabilities, including test facilities; computational models and facili- ties; and intellectual capital, available from NASA, the FAA, the Department of Defense, and other interested research organizations in government, industry, and academia. Assessment of NASA Response. NASA is collaborating effectively with the Department of Defense in facility management. NASA is also improving collaboration with other research organizations in some areas. Recommendation 8 from the Decadal Survey The U.S. government should conduct a high-level review of organizational options for ensuring U.S. leader- ship in civil aeronautics. Assessment of NASA Response. Recommendation 8 is not directed at NASA, and it is beyond the scope of NASA’s authority. However, Section 604 of S.1300, the Aviation Investment and Modern- ization Act of 2007, would direct the President to establish the Advisory Committee on the Future of Aeronautics. The committee would consist of 7 members selected from a list of 15 candidates proposed by the National Academy of Sciences. The committee would “examine the best governmental and orga- nizational structures for the conduct of civil aeronautics research and development, including options and recommendations for consolidating such research to ensure continued United States leadership in civil aeronautics. The Committee shall consider transferring responsibility for civil aeronautics research and development from NASA to other existing departments or agencies of the Federal government or to a non-governmental organization such as academic consortia or not-for-profit organizations.” As of October 30, 2007, this bill was still under consideration by the Senate. In Chapter 3, see the section entitled “Aeronautics Workforce Issues” for more information related to the involvement of external organizations in NASA’s research.

64 NASA AERONAUTICS RESEARCH—AN ASSESSMENT REFERENCES NRC (National Research Council). 2006. Decadal Survey of Civil Aeronautics: Foundation for the Future. Washington, D.C.: The National Academies Press. Available online at <http://www.nap.edu/catalog.php?record_id=11664>. NASA (National Aeronautics and Space Administration). 2006. Aviation Safety Program, Aircraft Aging & Durability Project Technical Plan Summary. Washington, D.C.: NASA Headquarters, Aeronautics Research Mission Directorate. Available online at <www.aeronautics. nasa.gov/nra_pdf/aad_technical_plan_c1.pdf>. OAG (OAG Worldwide Limited). 2007. Trends in fleet models and aircraft age. London, England: OAG Worldwide Limited. Available online at <http://www.oag.com/oagcorporate/press_releases_overview.html>. Woods, D.D. 1995. The alarm problem and directed attention in dynamic fault management. Ergonomics 38(11): 2371-2393. Wlezien, R., and L. Veitch. 2002. Quiet Supersonic Platform. AIAA Paper 2002-0143. January 2002. Washington, D.C.: American Institute of Aeronautics and Astronautics.

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In 2006, the NRC published a Decadal Survey of Civil Aeronautics: Foundation for the Future, which set out six strategic objectives for the next decade of civil aeronautics research and technology. To determine how NASA is implementing the decadal survey, Congress mandated in the National Aeronautics and Space Administration Act of 2005 that the NRC carry out a review of those efforts. Among other things, this report presents an assessment of how well NASA's research portfolio is addressing the recommendations and high priority R&T challenges identified in the Decadal Survey; how well NASA's aeronautic research portfolio is addressing the aeronautics research requirements; and whether the nation will have the skilled workforce and research facilities to meet the first two items.

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