List of investigators Plasma Electrolysis Rocket Professor John Foster & Professor Alec Gallimore + The University of Michigan & Department of Nuclear Engineering and Radiological Sciences + Department of Aerospace Engineering

Plasma Electrolysis Propulsion Background and Motivation Water electrolysis propulsion — electrochemical decomposition of water into hydrogen and oxygen propellants Water electrolysis identified years ago as promising propulsion approach Higher thrust/power ratio than electric propulsion Isp >350 s, higher than other storable chemical options Propellant is environmentally friendly and low cost Water storage is straightforward Enables in situ propellant production from water-ice sources on the Moon and Mars Can be used in conjunction with fuel cells and environmental control systems, respectively Previous efforts involved the use of membranes and electrochemical catalysts —limited throughput, increased complexity, and reduced reliability

Plasma Electrolysis Rocket Electrolysis can be carried out using high-pressure, non-thermal plasmas High-pressure plasma discharge offers distinct advantages over conventional approaches Increased reliability and higher throughput through the elimination of physical catalyst Simplification through the elimination of electrolytes Gas production rate depends on discharge power Reactivity involves interaction of energetic electrons and radicals with water Greater control over reactivity Diffusion of hydrogen and oxygen through water rather than an electrochemical cell also increases throughput Reduced system complexity Background and Motivation

Plasma Electrolysis Rocket Technical Approach and Objectives Atmospheric plasma surface discharge test bed experiment Discharge will be characterized as a function of power, excitation frequency/mode, and electrode geometry Emission spectra will be used to assess production rates Assess hydrogen/oxygen production rates directly via holding cell pressure measurements and compositional sampling Higher TRL level plasma electrolysis model will be developed based on experiments –Model will characterize performance –Long-duration test to understand electrode wear and general durability Design simple rocket demonstrator Water plasma approach leverages heritage from ongoing water plasma tests at the Plasma Science and Technology Laboratory and the Plasmadynamics and Electric Propulsion Laboratory

Plasma Electrolysis Rocket Anticipated Results Discharge optimization and product characterization – DC operation – Low-frequency RF Pulse modulated Continuous wave – Sensitivity to water salinity accessed Completion of experiments aimed at assessing throughput Assessment of efficiency and power requirements relative to conventional electrolysis Demonstration of a high- fidelity, laboratory model unit Schematic Depiction of Test Cell