Engineering Aeroscience and Fright Mechanics

NGT-44-001-800 S-2-I Hypersonic spacecraft reentering the earth's atmosphere encounter ex_eme heat due to atmospheric friction. Thermal protection system (TPS) materials shield the craft from this searing heat, which can reach temperatures of 29000 F. Various thermophysical and optical properties of TPS materials are tested at the Johnson Space Center Atmospheric Reentry Materials and SU'uctures Evaluation Facility, which has the capability to simulate critical environmental conditions associated with entry into the earth's atmosphere. Emissivity is an optical property that determines how well a material will reradiate incident heat back into the atmosphere upon reentry, thus protecting the spacecraft from the intense frictional heat. This report describes a method of measuring TPS emissivities using the SRS000 Scanning Spectroradiometer, and includes system characteristics, sample data, and operational procedures developed for arc-jet applications. S-2-