Surface Volatilization Investigation of Graphite

The re-entry vehicle posseses enough kinetic energy that it becomes hypersonic while passing throughthe upper atmosphere. This kinetic energy is quickly transferred into thermal energy as the quiescent atmosphere turned hypersonics with reference to the vehicle suddenly stagnates. Furthermore, the high energy process of generating plasma also ablates the leading edge surfaces, causing reactions between the charged gasses and the solid material composing the thermal protection system (TPS) of the aircraft. These reactions can be exothermic an d pose an additional mode of heat transfer into the body of the aircraft. Learning more about the interactions within the boundary layer will provide insight into how TPS will be designed. This thesis investigates the behavior of carbon monoxide within the boundary layer of a graphite surface subjected to oxygen bearing plasmas. Multiple gas species are probed using spectroscopic techniques, including laser diagnostics, so that relative populations along the stagnation line may be determined. This work was performed in an Inductively Coupled Plasma (ICP) chamber along with the use of a room temperature flow reactor to calibrate measurements and spectrally locate probed species with the dye pumped Nd:YAG laser. The first LIF measurements of carbon monoxide in the UVM Plasma Diagnostics Lab were successfully performed in buffered oxygen plasma. The signal recorded for CO was small and did not show rotational features at the J”=22 energy level. This suggests that CO is leaving the graphite surface at a multitude of rotational and vibrational energy levels since a fluorescence lifetime was attained during experiments. The relative populations of O atom, N atom, CN, and CO suggest the existence of an exchange reaction when graphite samples exposed to buffered air and buffered oxygen plasmas, which is considered to be the cause for the depleted CO signal further than 0.3mm from the surface