KY EPSCoR: Experimental Investigation of Gas-surface Interactions of Ablative Materials in Low Power Plasma Facilities

In the proposed work, a novel methodology for investigating gas surface interactions of a plasma with an ablative heat shield material shall be demonstrated. The data gained in such experiments is needed as validation data for high fidelity material response codes currently under development. Such codes are needed to predict heat shield performance during atmospheric entries to enable a reliable and optimized thermal protection system (TPS) design. The general idea is to gather data in a highly controlled environment while separating as many contributing processes as possible. The environment itself does not necessarily have to reproduce re-entry conditions, as long as it creates a situation relevant to the chemistry under investigation and can be reproduced by numerical simulation. A systematic variation of plasma conditions and surface temperatures will step by step build a database on gas-surface interaction of ablative materials in both equilibrium and non-equilibrium, providing information on selected reaction paths through the use of different working gases. A suitable hierarchy would be given through experiments with argon, argon/oxygen, argon/nitrogen, and argon/air, yielding increasing complexity of the possible chemical interactions between plasma and ablation products. A characterization of the actual interaction processes is foreseen through monitoring the emission of different interaction products such as OH, NH, CN, but also known ablation and trace elements from the ablator such as C, K, Ca, and Na, already observed in ground testing and during flight observation. In future research, different diagnostic methods such as laser diode absorption and laser induced fluorescence might be applied. In the frame of this work, a comprehensive characterization of the material response will not be possible for time reasons. The goal is, to develop and demonstrate the methodology and the capability of the facilities at the example of selected working conditions. Once demonstrated and documented, the PI will seek for agency funding to perform a rather comprehensive study. An initial proposal to NASA showed active interest from agency side but criticized the low Technology Readiness Level (TRL) status of the facilities available at the University of Kentucky (UK). The work fits well into the current activities at the University of Kentucky which is already known as a center for ablation research. It would also support and extend activities in the frame current NASA EPSCoR work on investigation of micro spallation of ablative TPS materials. Presenting an experimental validation test case to the community will add substantial value to the position of the UK research capacities and will significantly strengthen the bonds to NASA.