Simulations of electrospray in a colloid thruster with high resolution particle-in-cell method

A new multi-scale Particle-in-Cell (PIC) methodology to simulate multispecies electrosprays in colloid thrusters is presented. The ionic liquid particles, whose formation is simulated by molecular dynamics (MD), are introduced into the computational domain of the PIC model and tracked as they travel towards the extractor ring. The PIC solver is based on the solution of Poisson's equation in the absence of magnetic fields. The spatial domain is discretized by the finite difference method with a multi-level grid. The computational domain is decomposed in one dimension along the expansion axis and the corresponding linear equations are solved within the framework of PETSc. Number density distributions of ion and droplet species, thrust, specific impulse, and current are computed for different operating conditions of the electrospray. The results of the PIC simulations are compared with experiment and found to be in good agreement. The use of MD simulations to define the initial conditions for the PIC solver extends the atomistic length scale to that of an electrospray device.