Molecular Dynamics Simulations of Ion Extraction from Nanodroplets for Ionic Liquid Electrospray Thrusters

• Published in: Journal of electric propulsion Vol. 1; no. 1
• Main Authors: Enomoto, Takaaki, Parmar, Shehan M., Yamada, Ryohei, Wirz, Richard E., Takao, Yoshinori
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 26.09.2022
• Subjects: Applied and Technical Physics; Physics; Physics and Astronomy; Plasma Physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Ionic liquids; Molecular dynamics; Electrospray
• ISSN: 2731-4596
• DOI: 10.1007/s44205-022-00010-1

Molecular dynamics (MD) simulations were performed for ion extraction from electrospray thrusters to investigate relevant extraction processes numerically. To approximate the electrospray jet tip, a simulation domain consisting of 4-5 nm-sized ionic liquid droplets was used. The extracted ion angles and kinetic energies from EMI–BF 4 (1-ethyl-3-methylimidazolium tetrafluoroborate) and EMI–Im (1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide) droplets were quantified by applying uniform electric fields of 1.3–1.7 V nm −1 . The MD simulations are in great agreement with simulations presented in the literature and consistently show a greater preference for monomer emission than reported experimentally. At field strengths above 1.5 V nm −1 , apparent droplet fracturing and breakup lead to an increase in ion angular velocity distributions. Greater mobility of EMI–BF 4 ions than EMI–Im was also observed, indicative of the crucial role of cation-anion hydrogen bond strengths in ion extraction and beam composition between different propellants.