Graphite Ablation Experiments in the LHMEL Laser Facility

Understanding the surface reactions of ablating materials is an important need for modeling Thermal Protection Systems (TPS). There are many experiments out there that capture ablation phenomena seen in hypersonic flows, but ones that can be used to validate Computational Fluid Dynamics (CFD) codes are limited. Most experiments are conducted in arcjet wind tunnels where the enthalpy of the flow is increased by plasma heating due to arc discharges. These flows are hard to characterize due to the unknown dissociated state of the flow that varies spatially along the length of the plasma jet exiting the arc heater. These types of experiments are best for engineering design and not for looking at fundamental physics of surface chemistry. Other options for experimentally measuring surface reaction rates are in ovens or by laser heating of the surface. Laser ablation testing is currently conducted by the Air Force Research Lab Materials Directorate in the LHMEL facility. This work will describe an effort to conduct experiments to be used as validation tools for modeling surface reaction rates