Molecular Dynamics Simulations of a Liquid Gallium Electrospray Thruster

Molecular dynamics was used to simulate the operation of a liquid gallium electrospray thruster. Molecular dynamics calculates the motions of the ions and ion clusters of liquid gallium in a high electric field (∼1 V/nm) after they are extracted from a platinum capillary. Liquid gallium at 320 K is simulated with a modified ion–ion potential model. The platinum capillary at 320 K is modeled using a three-zone wall model with a Langevin thermostat, and the flow rate at 30 mm/s is generated by the fluidized piston model. The insertion part of a grand canonical ensemble (μVT) is adopted to supply ions of liquid gallium constantly into the platinum capillary. The electric potential and field generated by the extraction ring are solved by a combination of a finite element method and a finite difference method. The results of the simulations under several different operating conditions are used to characterize the performance of an electrospray thruster.