Numerical modeling of the flow discharge in MPD thrusters

Abstract

Two theoretical models for calculating the current and flow distributions in self-field MPD thrusters have been developed and are applied to evaluate the effects of geometry, propellant type, scaling, and other parameters on the thruster performance. For continuous thrusters, a stationary code has been developed. The extended Ohm's law is used to calculate the current contour lines, and a one-dimensional, two-component expansion flow model is applied to obtain the velocity, temperature, and pressure distributions for calculating the gas properties, which are again used in Ohm's law. An integration over the volume and thermal forces equals the thrust. The differential equation is solved by means of a finite-difference method for the geometry of the nozzle-type plasma thruster DT2-IRS, which has been investigated experimentally in a steady-state as well as in a quasi-steady-state mode. The calculated current density distribution and the computed thrust are compared with these experimental results. For the starting phase of the steady-state MPD thrusters as well as for pulsed thrusters, a time-dependent, fully two-dimensional code has been developed. It uses a modified McCormack FD method in cylindrical coordinates to calculate the time-dependent flow, temperature, and pressure fields.