Ultrafast Electron Dynamics in a Chemically Reactive and Biased Inductive Plasma Source
Abstract
Emerging trends in electric propulsion have motivated the use of molecular gases and chemically reactive forms of propellants. These imperatives include the storability of liquid or solid forms of propellant, in-situ harvestability of propellants during other planetary-asteroid missions, and the operation of electric propulsion in a very low Earth orbit environments where tenuous amounts of air is available to harvest. However, little is understood about the viability of existing ionization mechanisms and excitation schemes when they are extended to operate with molecular propellants and multi-component reactive mixtures. Radiofrequency plasma sources are one candidate architecture to process molecular gas streams as they can drive favorable molecular excitation schemes, provide some level of control over distribution functions through pulse shaping, and limit the susceptibility of cathode poisoning and degradation when operated on reactive gases. However, the dynamics of plasmas in these systems, their self-organization and evolution during radiofrequency cycles, and their interaction with molecular propellants still have a variety of open questions. This proposal will develop a modular radiofrequency test cell, an ultrafast plasma diagnostic, and an inference and data fusion framework to answer these questions and improve our understanding of plasma dynamics in chemically reactive radiofrequency systems. Experiments will be performed to probe the spatial and temporal evolution of plasma properties (e.g., plasma density, refractive index, etc.) across different time scales in radiofrequency systems, including periods that resolve the driving radiofrequency oscillations (approx. 10 - 100 ns), electron transport (approx. 1 ns), ion transport (approx. 1 micro s), and collisional energy exchange between neutral molecules (approx. 1 micros - 1 ms). These experiments aim to validate modeling and simulation thrusts, quantify uncertainties within measurements using Bayesian inference, and inform the necessity of different transport timescales to resolve the coupling between plasma dynamics and molecular excitations in emerging electric propulsion architectures.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 06, 2025
- Source ID
- FA95502410335
Entities
People
- Thomas C Underwood
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Texas at Austin