Space Heritage: The Apollo Heat Shield; Atmospheric Reentry Imprint on Materials’ Surface

Abstract

ABSTRACTThe heat shield is part of a thermal protective system (TPS) essential in shielding the cargo of a spacecraft during reentry to the earth’s atmosphere. The ablated surface of the heat shield is a testimony to the harsh reentry environment, evidenced in melting and charring among other phenomena that occur during reentry at velocity of 9-11 km/sec. The aim of this study was to extrapolate information about atmospheric reentry from the surface of the ablated material. A sample of the heat shield from the test vehicle of the Apollo Program, AS-202, was the subject of the analysis.For the preliminary studies, selected investigation modes from the Global Optimal Strategy model, developed to identify wear of engineering surfaces, were applied: examination of structure, optical observation, physico-chemical characterization and surface morphology. Instrumentation used included: microscopic surface analysis with Extended Depth of Field composite images (EDF), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR), confocal scanning laser microscopy and laser scanning microscopy. The Apollo Program testing vehicle AS-202 (1966) ablated specimen sample was obtained from the collection of the National Air and Space Museum (NASM), Smithsonian Institution, Washington DC. The authors combine their diverse experiences in tribology and in artifacts’ museum conservation so as to contribute to the space heritage material science. This study represents one of the building blocks of a larger project, the Fundamental Model of public outreach and perception (FAM-pop) of complex aerospace technologies.