Abstract
Lifetime evaluations by the numerical analysis of ion engines has become important for long-term missions. To use numerical analysis as a tool for evaluating the engine lifetime, a code that predicts grid erosion caused by the impact of ions quantitatively is required. In most codes, the electron number density is estimated from the Boltzmann relation because the calculation time of three-dimensional analyses becomes huge. In this paper, to evaluate the applicability of the Boltzmann relation in ion engine analysis, three-dimensional analyses of a Hayabusa type three-grid ion engine using a full-PIC (particle in cell) code and hybrid-PIC code using the Boltzmann relation were performed. The comparison of the results revealed that the electron number densities obtained by the two analyses agree well in almost the entire region. However, in the downstream neutralizing region, where the electric potential is positive, the electron number density for the hybrid-PIC code increases up to about seven times higher than that for the full-PIC code.
