Spallation Particle Characterization for Ablative Thermal Protection Systems

Spallation Particle Characterization for Ablative Thermal Protection Systems Abstract Spallation is a phenomenon in which solid particles are ejected off the surface of an ablative material in a high-enthalpy, high-shear flow field. The main contributor to this phenomenon in carbon-based heat shields is the mechanical erosion of carbon fibers weakened by oxidation decomposition. The dynamics of this phenomenon, which are poorly characterized in the literature, strongly affect the ablation rate of the material. In state-of-the-art codes, ablation by spallation is modeled using a "failure" ablation rate that is empirically determined. The present study aims at experimentally investigating spallation products ejected in the flow field and using this information to estimate the importance of spallation in the rate of ablation of low-density carbon/phenolic materials. Results will be obtained from a test campaign to be performed at the NASA Langley HYMETS arc jet facility, including direct particle capture and high-speed multi-camera imagery, will be used to measure the dimensions and characteristics of particles emitted from carbon-fiber samples exposed to an arc jet airflow. The purpose of this graduate fellowship request is to support Ms. Kristen Price''s graduate research developing and conducting the experiment, as well as analyzing its results.