Plume modeling of stationary plasma thrusters and interactions with the Express-A spacecraft

Hall-effect thruster flight measurements are compared with results from two-dimensional plume and three-dimensional spacecraft interactions computer simulations. The measurements were acquired onboard Express-A 2 and A 3, two Russian communications satellites in geosynchronus orbit. The spacecraft carry four propulsion units for east-west and north-south station keeping. Each unit consists of two stationary plasma thrusters. Ion flux and energy spectra were recorded at various positions with respect to the thrusters and are compared with results from simulations using a uniform electron temperature, two-dimensional plume code that computes the expansion of the main ion beam by a fluid approach. The dynamics of the charge-exchange plasma are determined by a particle-in-cell method. Comparisons suggest good agreement for plume angles less than 40 deg and electron temperature between 8 and 11 eV At approximately 4 and 9 m away from the thruster, and at plume angles less than 10 deg, the discrepancy between measured and computed values is found to be less than 10%. At larger angles, ion flux measurements exhibit large variations during operation of the same thruster. At 80 deg and 1.35 m away from the thruster, flux sensors recorded current densities that ranged between 12 and 55 mA/m(2). The two-dimensional code computes 27 mA/m(2) for an anode mass flow rate of 5.3 mg/s at this location. Moments induced on the spacecraft during the operation of each thruster were also recorded by the attitude control system and are compared with results from a three-dimensional spacecraft interactions code. These measurements were taken during rotation of the solar arrays.