NASA’s Aeronautics Research Mission Directorate in Washington and the Air Force Research Laboratory’s Office of Science Research at Wright-Patterson Air Force Base in Dayton, Ohio, have released a broad agency announcement describing their intent to establish three national hypersonic science centers. Hypersonic speed is defined as Mach 5, or five times the speed of sound, and faster. Sustained hypersonic flight is a national aeronautical goal.
NASA’s Fundamental Aeronautics Program and the Air Force Office of Science Research plan to set aside as much as $30 million to fund the centers over five years. The maximum grant will be approximately $2 million a year. The jointly funded program will support university-level basic science or engineering research that provides improved understanding of hypersonic flight.
We have identified three critical research areas: air-breathing propulsion, materials and structures, and boundary layer control. These three areas are the biggest hurdles to successful hypersonic flight and low-cost space access using an air-breathing engine.—James Pittman, principal NASA investigator for Fundamental Aeronautics Program’s Hypersonics Project
Research topics within each of the areas include:
Hypersonic Air-Breathing Propulsion. Research topics and associated supporting technologies are (1) characterization of the governing mechanisms with emphasis on turbulence-chemistry interactions, including chemical reactions, as well as novel experimental methods to acquire relevant data and innovative concepts for fuel-air mixing, ignition, and flame holding (via nonequilibrium plasma or other concepts); (2) formulation of novel simulation methods specifically addressing, but not limited to, large eddy simulations (LES) and LES-RANS hybrid models with high-order accuracy in the presence of shock-waves and associated sub-grid-scale closure models for compressible, turbulent combustion valid for both far-field and near-wall applications; and (3) novel concepts addressing combined-cycle-engine net-propulsive performance improvements, and/or dynamic mode-transition control methods.
Hypersonic Materials and Structures. The following focus areas have been identified for materials and structures: (1) Development of experimental and computational tools to accurately predict the properties, and ultimately model the performance and failure, of materials and structures in extreme and coupled thermal-mechanical-vibratory environments. (2) Discovery and characterization of new classes of thermal and oxidation resistant high-temperature materials including, but not limited to, complex hybrid engineered structures, composites, or thin films for repeated or sustained use at temperatures exceeding 1,400°C. (3) Development of processing science necessary to realize damage tolerant, complex shaped materials with improved oxidation,reduced defects and near net geometry.
Hypersonic Laminar-Turbulent Transition. The control of the transition process from laminar to turbulent flow has the potential to be one of the most significant air vehicle design breakthroughs in decades.
The National Hypersonic Science Center in Hypersonic Laminar-Turbulent Transition will develop and validate physics-based transition estimation methods for nonequilibrium flows over representative vehicle surfaces and develop strategies for control of the transition process. Research areas may include, but are not limited to the following:
Development of a theoretical basis for identification of instability mode competition and mode interaction leading to well defined physics-based numerical tools for the design environment;
Experimental characterization of mode interactions and competition in transitional flows. Investigation of receptivity processes, instability growth, and both passive and active control approaches;
Assessment of the influence of surface roughness, as-built surface finishes, and degraded surface materials on the transition process and physics-based estimation methods;
Assessment of the influence of nonequilibrium thermodynamics, surface chemistry and catalysis, and ablation product blowing on the transition process; and
Development of strategies and methods for control of the transition process.