Ground-based experimental study on the contamination potential of a freely expanding 10 N bi-propellant thruster plume

Abstract

Satellite thruster plume constituents pose a challenge when it comes to estimating their potential to degrade or contaminate spacecraft surfaces. Therefore, ESA has commissioned a study that covers the characterization of a European bi-propellant attitude control thruster plume and its potential contamination impact. In this regard, a freely expanding 10 N MMH/MON bi-propellant thruster plume is investigated in this ground-based experimental campaign. Methods of investigation include quartz-crystal microbalance (QCM) and mass spectrometry (MS) measurements. QCM experiments supply data on mass flux as well as desorption rates at temperatures ranging from 80 to 300K, which help to estimate the impact of plume gas on surfaces of different temperatures. Additionally, MS measurements map the chemical composition of gaseous plume species under a wide range of angles, spanning from plume centerline to the backflow region. The optical and chemical analysis of actual spacecraft surface material witness coupons that were exposed to the plume complements this study. Furthermore, high-speed imaging of the thruster nozzle supports the interpretation of results with information on ejected droplet velocities, trajectories and size distribution, especially regarding potential droplet impact features which were identified on witness materials in this on-going study.