AIAA 2003-3785 Aerodynamics for Revolutionary Air Vehicles William L. Sellers 111, Bart A. Singer, and Laurence D. Leavitt NASA Langley Research Center Hampton,VA 21 st Applied Aerodynamics Conference 23-26 June, 2003 Orlando, FL ~~ For permission to copy or to republish, contact the copyright owner named on the first page. For AIAA-held copyright, write to AIAA Permissions Department, 1801 Alexander Bell Drive, Suite 500, Reston, VA, 20191-4344. AI AA-2003-3785 Aerodynamics for Revolutionary Air Vehicles William L. Sellers HI*, Bart A. Singert, and Laurence D. Leavitt‘ NASA Langley Research Center Hampton, VA 2368 1-2 19 Abstract Introduction Aeronautics research has seriously declined Projecting visions for the future is always a risky partly because of the perception that it is a mature endeavor. The tendency in predicting future science and only incremental improvements are technological advances is to be overly optimistic in possible. Recent aeronautics roadmapping activities at terms of evolutionary improvements, and to be NASA Langley paint a different picture of the future. completely blindsided by truly revolutionary advances. Breakthroughs are still felt to be possible if we expand These tendencies should not be overly surprising; linear the current design space of today’s vehicles and extrapolations of current trends are natural. Foreseeing optimize the airspace and vehicles as a system. The the nonlinear saturation of those trends is more paper describes some of the challenges that the aircraft difficult. Identifying promising opportunities that have and airline industry face. These challenges include real potential for completely disrupting the way we live political, technical and environmental issues. Examples and work is even more difficult. In the area of of the opportunities and technologies that could provide aerodynamics and air transportation learned scientists a different vision for the future are discussed. predicted that we would never fly, never cross a speed barrier, or the public would never accept air Nomenclature transportation only to be proven wrong in a relatively b Span (inches) short period of time. Those making the negative CL 3-D Wing lift coefficient predictions often worked long and hard on what they D Drag Force believed to be the relevant problems before deciding L Lift Force that no solution was in sight. Their error was in not M Machnumber appreciating that some new approach could bypass the W Weight problem(s), they understood to be in the critical path. It is with this in mind that this paper presents visions of a Abbreviations possible future and the impact aerodynamics must have FLOPS Floating-point operations per second to enable a future filled with new and revolutionary air vehicles. MIPS Millions of Instructions per second There is an oft-spoken concern that aeronautics, SFC Specific fuel consumption and aerodynamics in particular, is mature, and nothing CMOS Complementary metal-oxide semiconductor more than incremental gains in performance and LlNPACK Linear algebra software package capacity are possible. That perception is partly due to Superscripts past successes in the field. The public, for the most Fluctuating component - part, sees an efficient and safe air transportation system Subscripts with flights to most every part of the globe. Today’s max Maximum value during actuator blowing cycle aircraft are a marvel of engineering, science, and mean Mean value technology. Aerodynamic efficiency in terms of ML/D min Minimum value during actuator suction cycle has increased approximately 30% since the beginning rms Root-mean-square value of the jet age’. Range has increased such that non-stop w Freestream c flights of 8,000 nm are a reality. Aircraft noise has been reduced significantly in the last 20 years. ‘Head. Flow Physics and Control Branch, Associate Fellow PAsst. Head, Computational Modeling and Simulation Unquestionably, the rates of improvement in Branch. Senior Member these areas have slowed, and linear extrapolation of the $Head. Configuration Aerodynamics Branch, Associate current rates of improvement could certainly lead Fellow someone to conclude that the future holds only incremental improvements. This is especially Copyright0 This material is declared a work of the US. Government unfortunate because straightforward extrapolation and is not subject to copyright protection in the U.S. suggests that significant problems lie ahead. These 1 problems require a rethinking of our air transportation controls, and aerodynamics and acoustics looked at and vehicle systems. The airline industry is under their own disciplines and the interactions between them economic pressure and increased public attention to that would be required. The NASA teams’ efforts paint quality-of-life issues, such as noise and emissions will an entirely different picture of aeronautics, one in make profits harder to generate and operations more which it is not mature, but is poised to take off in bold difficult. Prior to September 11, 2001, travelers were new directions. facing increased transportation delays and projected This paper will focus on the role of 4 growth that would make the situation worse. aerodynamics in that future vision and discuss the Geopolitical and economic circumstances have environment and constraints in which it will have to complicated projected growth scenarios, but most operate. There is a deep belief that for this vision to projections suggest that air transportation growth will become a reality, multi-disciplinary efforts must be pick up and we again will be faced with increasing increased and the interactions dramatically improved. delays in a few years. This is especially true if one believes that truly Hence, just at a time when dramatic leaps in disruptive capabilities can occur through the innovative performance would be most beneficial, we are faced integration of existing technologies as well as through with a possible future of slow incremental advances in the invention of new previously undiscovered traditional aeronautics metrics. No one should be technologies. Therefore, there will also be a discussion blamed for such dire forecasts; they are the predictable of some of the advancements coming from other result of extrapolating current trends. We can ensure disciplines that are critical. that the forecasts are true by continuing on our current path. We can continue the steady declines in NASA Blueprint for Aeronautics Aeronautics research funding, the steady aging of the NASA recently published its blueprint for workforce in the field, and the inclination to continue to aeronautics4 that provides a glimpse of what the future work on familiar problems in familiar ways. of aviation could be in the year 2050. Revolutionary On the other hand, we recognize that huge new air vehicles will be required for this new vision. improvements are possible if we ask the right questions. This new future brings about the possibility for new For instance, we don’t need to increase aircraft speed to large, long haul concepts, increased speed, autonomous reduce passenger travel time. We might accomplish operations, and the necessity for new vehicle concepts this better if we started to look more closely at that provide runway independence. The concept of improving our ability to take off and land safely in a runway independence will require lightweight vehicles wider range of weather conditions, to take off and land with high thrust-to-weight ratio, and very effective quietly and safely from an increased number of airports, high-lift or propulsive systems that will likely have to many with considerably shorter runways, and to make be low noise solutions as well. The blueprint for air transport accessible to small communities without aeronautics briefly described some of the new introducing noise and emissions concerns. While the technologies that will enable the increased capabilities current hub and spoke system of air transportation of these revolutionary air vehicles. evolved as a cost-effective optimum for a given type of The blueprint addressed the challenges facing aircraft, we have only begun to consider the the current aviation system including capacity, safety, aerodynamic issues that need to be tackled to provide and security. It highlighted the fact that there are over opportunities for other approaches to air transportation. 800 restrictions worldwide on aircraft operations that The Europeans, to their credit, have formulated severely limit growth into certain markets. It discussed a vision for their future in aeronautics, and have a the issues of C02 and NOx emissions on both air highly effective European framework2 for research and transportation capacity and the environment. It outlined technology development as well. Perhaps the best the importance of aeronautics to the future of our nation example of their vision for the future3 describes a 2020 and the global economy. The blueprint laid out the role future where European aeronautics is the best in the of the U.S. government in this future vision. It also world, and they are winning more than 50% of the stated that NASA’s role was to provide enabling world market share in aircraft. The document includes technology, by conducting high-risk research, devel- their goals on reduced emissions and noise, and oping unique facilities, and fostering an educated and increased air transport safety. innovative workforce. With these factors as a backdrop, in 2001 NASA The NASA aeronautics blueprint recognized that