In Situ Quantitative Spatially-resolved Ablation Diagnostics in High-Enthalpy Flows

ABSTRACT: The objective of the STTR Phase-I effort proposed by Spectral Energies LLC and The University of Tennessee is to demonstrate the feasibility of an in situ quantitative measurement of the products generated by the degradation of a material surface exposed to a hypersonic environment. The concept is based on a state-of-the-art diagnostic method: Coherent Microwave Rayleigh Scattering from Resonance-Enhanced Multi-Photon Ionization (Radar REMPI) measurements of atomic species of O, C, and N and molecular species CN. Using this approach, quantitative, spatially-resolved, quenching-free measurements of key intermediate species in high-enthalpy gas-surface interactions will be achieved. Laboratory tests will be conducted in the Phase I to demonstrate the quantitative diagnostic capabilities by the novel platform. Temporally and spatially resolved nonintrusive measurements will not only provide benchmark quality data for CFD validations, but also offer unprecedented insight into the fundamental processes occurring within high-enthalpy flows. The integrated laser diagnostics platform will provide quantitative benchmark measurements relevant to a broad spectrum of aerospace applications and have great potential for transition to a commercially available diagnostic product.; BENEFIT: The development of hypersonic systems capable of flight at Mach numbers greater than 5 will greatly enhance the ability of the Air Force and DoD to accomplish time-critical missions for strike and Intelligence, Surveillance, Reconnaissance (ISR). To achieve this goal, a detailed understanding of the fundamental processes of high-enthalpy gas-surface interactions (GSI) is required to significantly increase the reliability of Thermal Protection Systems (TPS) for hypersonic and reentry vehicles. Under the current program, a novel in situ quantitative spatially-resolved ablation diagnostic tool will be developed, enabling unprecedented insight into the fundamental mechanisms of GSI and the potential for a commercializable system with broad applications across a variety of aerospace areas. Specifically, 1. Immediate benefits to AFRL test facilities Implement of novel multiple spectral diagnostics system in AFRL test facilities will greatly help improve the productivity of material and structure development for hypersonic and reentry vehicles. Further understanding of the chemistry in the hypersonic environments will significantly improve the hypersonic vehicle design and testing. 2. Scientific discovery Understanding the fundamental behavior of gas surface interactions under high enthalpy and high pressure conditions is a rich field of intellectually stimulating scientific challenges, which can quickly translate into technologies that provide societal benefits into material and structure development for the hypersonic and reentry vehicles. 3. National security and homeland defense Hypersonic aviation is vital to national security and homeland defense. Hypersonic speed provides options for engagement of time sensitive targets in anti-access/area-denial environments, and improves the survivability of Air Force systems. Hypersonic speed weapons are also a force multiplier as fewer are required to defeat difficult targets and fewer platforms are required from greater standoff distances. The proposed research will enhance our ability to validate integrated vehicle material and structure, to significantly reduce gas turbine and scramjet engine specific fuel consumption, and to flight test air-breathing hypersonic vehicles with global reach. 4. Economic security and prosperity The enormous roles of air transportation and aviation in the modern life are overwhelming. Further improvement into the hypersonic regime by development of novel materials and structures will have huge impacts on almost every corner of the US economy. The successful development of the commercial products will extend the global leadership of US on manufacturing and R&D in next-generation aviation system.