rently available information indicates that propulsion research should generally support the continued evolution and use of high-bypass turbofan engines burning liquid hydrocarbon fuels. At the same time, a portion of the research should anticipate the possibility of (1) an eventual changeover to hydrogen, (2) the use of an advanced gas turbine engine core, and/or (3) the use of fuel cells to generate electric power for electrically driven engines if and when room temperature superconductivity becomes practical. Research in these areas should start at a low level and proceed at a pace consistent with research focused on nonaerospace applications.

The development of environmentally beneficial propulsion technologies that might eventually be applied to aircraft systems should be tracked to understand their potential environmental benefits and tradeoffs (for example, evaluating the potential advantages and disadvantages of using hydrogen fuel, including the potential to use cryogenic hydrogen as a heat sink for electrical components). Support should be provided for research necessary to take advantage of new technologies, including the design of components (such as low-emission combustors compatible with hydrogen fuel or electrically driven propulsion engines compatible with advanced fuel cells) and the development of new system concepts (such as an environmentally acceptable means of releasing water into the atmosphere to mitigate the effect of greatly increased emission of water vapor that would result from the use of hydrogen fuel).

Avionic systems include computers, communications networks, sensors, controls, operational software, and human-computer interfaces. Avionics plays an increasingly critical role in the safe and efficient operation of commercial aircraft and now accounts for up to 40 percent of the capital cost of new aircraft.

Onboard electronics perform or monitor virtually all critical functions in an aircraft, including engines, control surfaces, stability augmentation systems, active flow controls, flight path, collision avoidance, and interactions with the external air traffic control system.

The federal government, especially the Department of Defense, has supported basic long-term research and applied research and technology development that continue to enhance the capabilities of avionics on both civil and military aircraft. The success of this research has been enabled in large part by smaller, more capable computers and more sophisticated software.

Chapter 2 discussed the importance of research in automation and the ability of automated systems to enhance the performance of human operators and the overall system. Advanced on-board avionics will be necessary to implement any new operational concepts that call for increased automation of cockpit and navigation functions.

Federal agencies should continue research aimed at enhancing airborne avionic systems through evolutionary improvements, while pursuing longer range research that could lead to major breakthroughs. For example, advances in nanotechnology may provide major benefits to avionics in computing, sensors, and active distributed control. Research in avionics that relates to air traffic control and automation should be integrated into the overall research strategy for the air transportation system as a whole. Two examples of ongoing research and development of this type are (1) the Alaska Airlines all-weather approach system and (2) work by NASA’s SATS project to enable safe low-visibility operations at minimally equipped landing facilities through the development of new operational concepts, sensors, pilot interfaces, and procedures.

Nanotechnology is an emerging technology with the potential for broad application to many aspects of aircraft design. Nanotechnology deals with materials and devices having at least one dimension on the order of 1 to 100 nanometers. The design of nanoscale materials deals with molecular-scale structures, whose physical and chemical properties are different from materials at larger scales. At nanoscales, no atom is far from a surface. This changes chemical reactivity, coherent scattering, and other processes. Devices also involve large, but countable, numbers of atoms.

Nanotechnology is still in its infancy and is just starting to move into operational applications. In fact, the term nanotechnology is somewhat misleading, implying that research has generally advanced to the stage of developing useful technology, when in many (or most) cases, nanoscale research is still scientific research (and would more accurately be referred to by the less common term nanoscience).

Global investment in nanotechnologies is about $1.5 billion per year, primarily in the United States, Europe, and Asia. The U.S. federal government appropriated $604 million for nanotechnology research and development in fiscal year 2002. The four agencies most heavily involved in nanotechnology research and development are the National Science Foundation ($199 million), the Department of Defense ($180 million), the Department of Energy ($91 million), and NASA ($46 million) (Roco, 2002).

The aeronautical community should maintain an awareness of nanotechnology research in other disciplines that might be used in aeronautical applications, such as flow control, lubrication, structures, and manufacturing. A recent study (NRC, 2002c) on the future role of micro- and nanotechnologies in improving Air Force capabilities identified three scientific frontiers that nanotechnology research

Front Matter (R1-R16)

Executive Summary (1-5)

1. Foundation for Change (6-12)

2. Improving Air Transportation System (13-18)

3. System Modeling and Simulation (19-26)

4. Improving Aircraft Performance (27-41)

5. Process for Change (42-44)

Findings, Recommendations, and the Big Question (45-50)

Appendix A: Statement of Task and Study Approach (51-54)

Appendix B: Comparative Assessment of Goals and Visions (55-59)

Appendix C: Biographies of Committee Members (60-63)

Appendix D: Propulsion Taxonomy: Comments on Propulsion Fundamentals (64-66)

Appendix E: Four Levels of Models (67-70)

Appendix F: Acronyms and Abbreviations (71-72)