Application of Ab-initio Quantum Chemistry Techniques to Hypersonic Flows for Plasma Blackout Alleviation

Abstract

Plasma blackout in hypersonic flows produced by weakly-ionized air plasma sheaths is a phenomenon that attenuates or completely blocks communications with vehicles flying in a high-enthalpy flow environment. The ability to mitigate this issue can be useful from various re-entry vehicles to in-atmosphere hypersonic vehicles, especially with aerospace largely pushing into the hypersonic field across the industry.

This thesis asks how effective are electrophilic compounds at reducing the number density of electrons within a hypersonic plasma sheath environment. This reduction in the electron number density reduces the critical plasma frequency, thus allowing for the successful propagation and transmission of electromagnetic signals.

This work presents three contributions. First, a framework is proposed for the construction of viscous hypersonic chemistry models using \textit{ab-initio} quantum chemistry techniques, which accounts for both spin-adiabatic and spin-nonadiabatic chemical processes. Next, an analysis is performed on the pressure-dependence of the chemical reactions that are typically seen in hypersonic flow environments, showing that pressure-dependent chemical rate coefficients are a key aspect in these environments and thus should not be ignored. Lastly, a first principles approach to assessing the feasibility of such a system and the resulting sizing requirements is presented, including a method for identifying and calculating the predominant chemical timescales which govern the electron quenching process. Together, these contributions provide a fundamental way to model and solve the problem of alleviating plasma blackout using electrophilic compounds.