Analytical ion thruster discharge performance model

A particle and energy balance model of the plasma discharge in magnetic ring-cusp ion thrusters has been developed. The model follows prior work in the development of global zero-dimensional discharge models that use conservation of particles into and out of the thruster, conservation of energy into the discharge and out of the plasma in the form of charged particles to the walls and beam, and plasma radiation. The present model is significantly expanded over the prior art by closing the set of equations with self-consistent calculations of the internal neutral pressure, electron temperature, primary electron density, electrostatic ion confinement (due to the ring-cusp fields), plasma potential, discharge stability, and time-dependent behavior during recycling. The model only requires information on the thruster geometry, ion optics performance, and electrical inputs, such as discharge voltage and currents, to produce accurate performance curves of discharge loss vs mass utilization efficiency. The model has been benchmarked against several ion thrusters, and successfully predicts the thruster discharge loss as a function of mass utilization efficiency for a variety of thrusters. The discharge performance model will be described and results showing ion thruster performance and stability presented.