The ion engine is suitable for a primary or auxiliary propulsion of the long mission time spacecraft because of its high specific impulse. An optimum system design and an engine operation optimization are described in case of an ion engine application for north-south stationkeeping of a synchronous communication statellite.
The optimum design analysis which allows determination of the necessary ion engine operating conditions to yield the lightest possible system to perform N-S stationkeeping is presented. The engine characteristics are modeled and identified by the experimental data, then the daily thrust period about nodal points and the engine net-accelerating voltage are optimized for the lightest system design.
Moreover an on-line computer steady-state optimization technique to keep optimum operating conditions under system component characteristic changes in the environment is presented. The evolutionary optimization (EVOP) approach that uses an iterative procedure with statistical significances which adjust the control variables in successive moves to arrive at the optimum of the objective function is used as an optimization procedure. The net-accelerating voltage and the vaporizer temperature or the propellant mass flow rate are used as the control variables. In this case the controlled object is a 5cm diameter mercury electron-bombardment ion engine. The strategy convergence time was about a few hours. This means that it is possible to optimize engine operating conditions during daily thrust period by this optimization procedure.