Modeling and Characterization of Electrospray Propellant-Surface Interactions

Electrospray thrusters are a promising technology for small satellite propulsion. The potential interaction of thruster plumes with spacecraft surfaces is of interest for mission design and assurance, especially due to the novelty of their ionic liquid propellants and limited flight heritage. Knowledge of plume byproducts is important for mission scientists to distinguish spacecraft-generated material from target measurements and for propulsion engineers seeking to understand and extend the lifetime of the thruster system. Plume deposition, erosion, and byproduct characterization will allow for wider adoption of these technologies and new mission architectures. These processes are investigated through a simulation framework across multiple scales, including the fluid dynamical processes governing the emission at the source, plume propagation and molecular-scale analysis of direct particle impingement on the extractor grids. In particular, this study focuses on the surface effects resulting from a flux of low-energy neutral clusters (at less than 34 eV). The outcome depends on both the cluster temperature and its impact energy. Ranges of impact energy conditions for neutral cluster impingement on the extracting electrode surfaces are informed by the plume model. Two temperatures are considered: 1000 K and 300 K. At 1000 K, most of the neutral particles scatter off the surface they impinge on intact and will start to split into their charged constituents around 34 eV. Molecular deposition on the plate has only been observed at 300 K and for low impact energies (< 0.1 eV).