Study on Variation and Movement of Extraction-Ion Beam by Grid Wear in Miniature Ion Engines

Abstract

This paper focuses on the variation in extraction-ion beam performances in miniature ion engines due to grid erosion. Because speed and cost are very important issues in microspacecraft development, we replace time-consuming grid wear tests with numerical simulations using the JAXA Ion Engine Development Initiatives (JIEDI) tool. By comparing the results obtained for a miniature ion engine with those of a 10 ion engine, we observe significant extraction-ion beam performance degradation in the miniature ion engine. Because miniature ion engines tend to omit gimballing devices to save their masses, we also present a numerical simulation for predicting erosion-induced movement in the thrust-vector direction for the estimation of the accumulation of thrust-vector misalignment toque, which must be unloaded by firing low-Isp chemical thrusters. Using the JIEDI tool, we can successfully calculate its movement by grid erosion and obtain the averaged thrustvector direction during the operation of the ion engine. This time-averaged thrust-vector direction provides the best initial thruster setting angle for each miniature ion engine.

Erosion rate measurement in ion thrusters using Cavity Ring-Down Spectroscopy technique

“…The sputtered atom trajectory is calculated using DSMC method, as well. The JIEDI tool has shown its usefulness, for example in the development of MIPS, Miniature Ion Propulsion System [9]. There are not enough verifiable data, especially in case of redeposition rate of the grid and for the validation of the numerical analysis tool, a sensor for lifetime estimation in situ is required.…”