Molecular Dynamics Insights into Ionic Liquid Transport-Emission Mechanisms in Electrospray Thrusters

The rapid advancement of microsatellite technology has heightened interest in ionic liquid electrospray thrusters (ILETs) due to their compact size and high thrust precision. This study investigates the microscopic transport and emission mechanisms of ionic liquids (ILs) in externally wetted ILETs through molecular dynamics (MD) simulations. The findings reveal that cations predominantly detach from the liquid surface on the imidazolium side and maintain a consistent posture, with the imidazolium on top and the alkyl chain downward, during the emission process. The potential energy, kinetic energy, and velocity increment of a single ion are approximately 16 kcal/mol, 0.084 kcal/mol, and 7 × 10^-4 Å/fs, resulting in a thrust and specific impulse of about 1.04 × 10^-3 nN and 6 s. The IL properties and emitter characteristics govern the emission process during the initial and early transport stages and the subsequent mid to-late transport stage, respectively. The ionic posture is primarily governed by long-range Coulomb forces, while short-range interactions significantly affect the preemission process. Optimal thruster performance occurs with emitter inclination angles of <45° and electric field strengths between 1.2 and 1.3 V/nm. Additionally, heating the IL to 330 K further increases emission efficiency and decreases the onset electric field by 0.1 V/nm compared to 260 K. This study provides a theoretical basis for optimizing emitter design, IL selection, and operational parameters, facilitating the development of high-precision, low-noise propulsion systems for microsatellites.