The Influence of Hypersonic Flight Regimes on Electron Transpiration Cooling Systems

Electron transpiration cooling (ETC) is a candidate thermal management strategy for hypersonic vehicle surfaces, utilizing thermionic emission to dissipate heat. Thermionic electrons carry heat energy away from hot leading edges as potential and kinetic energy, and are redeposited on a cooler surface downstream. However, an operational understanding of the regimes of hypersonic flight where ETC is applicable, as well as the power requirements ETC systems entail, is incomplete. To further this understanding, an model to estimate the composition of a hypersonic environment is constructed. This model is coupled to a one-dimensional ETC model, and thermionic cooling effectiveness is assessed across various hypersonic trajectory parameters. The role of material choices is investigated, and flight regimes where ETC is effective, as well as ineffective, are identified. Finally, ETC is incorporated into the trajectory optimization of a hypersonic vehicle. Integrated parameters, such as system energy requirements and heat loads, are computed for trajectories subject to constraints such as a maximum wall temperature. Results suggest that the cooling performance predicted for an ETC system can successfully reduce peak surface temperatures and improve the performance of a hypersonic vehicle for reasonable power requirements.