Investigation of cation and anion emission mechanisms from porous electrospray thrusters using ionic liquid mixtures

In this study, we investigated plume formation, ion emission, and fragmentation using a single emitter ion source to explore mixtures as alternative propellants. Our aim was to unravel the complex interactions between cations and anions by examining combinations of two cations ([EMI+] and [EA+]) and two anions ([BF−4] and [NO−3]). Initial results suggest that dissolving room temperature solid ionic liquids (ILs) within room temperature liquid ILs can improve solution conductivity by 20 %. Our findings indicate that EA-N solutions demonstrate both acceleration region and field-free fragmentation, while pure EMI-BF4predominantly undergoes dimer-to-monomer field free fragmentation, releasing high-energy neutrals. The EMI-N : EMI-BF4 mixture showed an outstanding current emission with lower onset voltage. Time-of-Flight (ToF) mass spectroscopy measurements revealed the emissions of [EA+][EMI-BF4], [EMI+][EA-BF4], [NO+][EMI-N] and [NO+2][EMI-N] from mixtures with EMI-BF4. This study concludes that ionic liquid mixtures can be beneficial as propellants, forming high mass-to-charge ions or emitting higher currents.