NASA EPSCoR FY22 R3 Appendix B (ARC): Wavelength-dependent Micro and Meso Scale Measurements of Radiative Properties

Wavelength-dependent micro and meso scale measurements of radiative properties Design and development of thermal protection systems (TPS) materials is an integral part of most NASA missions. Missions under development now include the degradation of the TPS material through in-depth radiative transfer (transport) as a design metric. New modeling tools to understand penetration of radiative signatures from the shock layer into the TPS material are being developed by researchers at the University of Kentucky, supported through prior support from NASA and NASA KY EPSCoR. In the proposed effort, complementary experiments will be performed to provide insights into the complicated photon paths through complex heterogenous structures of TPS materials and improve the understanding of radiative transport in TPS materials. Additionally, the data will help to rigorously validate the radiative modeling tools that are being developed, both at NASA and the University of Kentucky. Wavelength-dependent radiative properties and functions will be obtained both at the microscopic and mesoscopic length scales in the range of 200-700 nm using continuous light sources, which covers most of the shock layer emissions relevant to planetary entry, including re- entry back to Earth. Additionally, fixed wavelength near-IR source will be used for CO and CO2 emissions to cover wavelength emissions for entry into Mars. The refractive index and absorptivity on a single fiber will be quantified at the microscale, and the reflection and transmission functions for the bulk TPS material will be quantified at the mesoscale. The ability to measure wavelength-dependent properties in the range of 200-700 nm is crucial because all previous measurements have only been performed in the near-IR region. Finally, the two sets of measurements will minimize any uncertainty in model inputs, allowing a direct comparison between the experiments and simulations, making this validation effort a one-of-a-kind effort in the TPS mesoscale modeling paradigm. Kentucky’s NASA EPSCoR jurisdiction solicited proposals from Kentucky university-led research teams to address NASA research needs listed as topics for the FY2022 NASA EPSCoR Rapid Response Research (R3) announcement (NNH22ZHA004C). The NASA Kentucky EPSCoR program collaborated with responding faculty researchers to develop and submit relevant proposals that address R3 task objectives. The proposed work in this proposal is in response to FY22 R3 Appendix B: Ames Research Center and the topic of B.1.2: “Measurements for Characterizing In-Depth Spectral Radiative Properties of TPS Materials.”