Abstract: For the Internal Dielectric Charging (IDC) of a particular spacecraft structure, in this paper, a 3-D IDC simulation is performed to a typical spacecraft complex dielectric structure——Solar Array Drive Mechanism (SADM) disc——considering the Geostationary Earth Orbit (GEO) with severe radiation environment (Flumic3). A charge transportation simulation is carried out by Geant4 and the electric field is numerically computed according to the charge conservation law. Based on those, the effects of shielding thickness on internal dielectric charging is studied, and a technique is proposed to improve the simulation efficiency by adjusting the lower energy limit of the incident electron spectrum according to the shielding thickness. The simulation results show that the most serious internal charging position occurs on the top edge of the contact face between the outermost upper layer dielectric of the disc structure and the metallic conducting ring. The increment of the shielding thickness could mitigate IDC. However, this mitigation effect is weaker as the temperature is falling. In the GEO with severe radiation environment (Flumic3), at temperature of 183 K, since the radiation-induced conductivity dominates the total conductivity, the dielectric conductivity will be cut down as the shielding thickness is increased. In this case, even using a 3 mm aluminum shielding, the peak electric field can reach the level of 10⁷V/m.

Key words: spacecraft, internal dielectric charging, 3-D simulation, dielectric disc structure, shielding thickness