Online

Ballou, Ian

Mechanical Engineering

2023

M.S.

The atmospheric reentry of hypersonic vehicles causes extreme compression of the gas surrounding the hypersonic vehicle due to the extremely high velocities. These compressed gases create a high enthalpy plasma environment at the surface of the vehicle and transfer thermal energy through heating to the surface of the vehicle. An ablative heat shield is used as a thermal protective systems (TPS) for many hypersonic vehicles to mitigate the effects of excessive surface heating. An example of such a TPS material for NASA Mars and Titan missions is Phenolic Impregnated Carbon Ablator (PICA).On production vehicles, a commercially available NuSil coating is applied to the PICA surface to reduce the spread of dust from the phenolic resin into sensitive electronics within the vehicle. This NuSil coated PICA material is known as PICA-N. PICA behavior has been well studied in various experiments and shows that uniform ablation occurs when the material is subject to a high-enthalpy atmospheric entry environment. However, tested PICA-N exhibits a spalling behavior in high heat flux regions of the material. Further understanding of this spalling behavior is of high interest as regions of non-uniform ablation from spalling could lead to possible failure of the implemented PICA-N TPS system. This thesis investigates how the effects of NuSil coating can cause mechanical failures within the PICA-N material. An automated NuSil coating apparatus was designed and built at the UVM Inductively Coupled Plasma (ICP) torch laboratory with the help of a Capstone Design team. Analyse of NuSil coating depth and unifor- mity were completed and showed that NuSil could be applied in a consistent layer on the PICA sample at a precise penetration depth. PICA-N samples that were coated at UVM were then tested within simulated atmospheric environments in the ICP torch facility. Thermal, visual, and spectroscopic data were collected to understand how PICA-N responds to these plasma conditions.