Plume Contamination Measurements of an Additively Printed, Green-Propellant Hybrid Thruster

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Plume Contamination Measurements of an Additively Printed, Green-Propellant Hybrid Thruster

Whitmore, Stephen A.

The dielectric breakdown properties of additively printed acrylonitrile butadiene styrene are leveraged to develop a green hybrid thruster family with capability for on-demand start, stop, and restart. Because acrylonitrile butadiene styrene is a new material for propulsion applications, no exhaust plume database exists, and the associated contamination potential for spacecraft surfaces is unknown. Analytical calculations of associated exhaust plume species are presented to identify predicted concentrations of primary condensable species $H_{2} O$ , ${CO}_{2}$ , and carbon (soot). When the hybrid thruster is operated near optimal equivalence ratio, the analytical studies show that combined mass concentrations of $H_{2} O$ and ${CO}_{2}$ constitute between 10 and 35% of total exhaust plume. Condensable carbon does not occur. This result is compared to 50% or greater mass concentrations of condensable species, ${NH}_{3}$ and residual ${NH}_{4}$ , for monopropellant hydrazine. Thus, the 3-D printed hybrid fuel is likely to burn cleaner than hydrazine. Results from ground-based and space-flight plume contamination experiments are presented. The contaminant sensor uses a light-sensitive photoresistor, mounted behind a quartz glass window to simulate spacecraft optical surfaces. Ground-based tests demonstrate approximately 12–13% optical attenuation after a 10-pulse burn sequence. Space flight data collected from a five-pulse burn sequence demonstrate optical attenuation levels approximately 2% higher.