Optimization Design of Radiation Vault in Jupiter Orbiting Mission

Abstract

In Jupiter missions, one significant challenge is the harsh environment. The radiation in Jovian orbit is much higher than that in earth bf vicinity in terms of intensity and energy level. In spacecraft (S/C) design, key electronics are packaged in an enclosed vault to help them survive through the mission. The preliminary optimization design methods of a radiation vault based on a genetic algorithm (GA) are introduced, including shield structure optimization and layout pattern of electronics optimization. In shield structure optimization, the method is combined with a total ionizing dose (TID) evaluation tool. The goal is to find the optimal multi-layer shield structure so that the TID, after the shielding, is minimal within the threshold of the total mass of the structure. In a 1-year mission with an orbit of $10\,\,R_{j}\times 25\,\,R_{j} \times 0^{\circ }$ , if the areal density is within 0.5–3 g/cm2, the optimal structure is bilayer or trilayer with high-Z material as an external layer and low-Z material as an internal layer. This structure benefits from the fact that the low-Z material is more effective in shielding energetic protons whereas the high-Z material is more effective in shielding energetic electrons. In the 1-g/cm2 situation, the optimal structure is a 0.829-mm lead layer combined with a 0.158-mm magnesium layer. Comparing with the traditional aluminum shielding structure, about 43.6% of mass can be saved. In layout pattern optimization, this method combines a packing algorithm and a 3-D TID simulation tool. Using this method, an effective design layout of the vault can be found. In this design, all avionics can survive through the mission. In addition, the mass of the vault is low enough that the layout pattern is acceptable in S/C design. As an example, 14 instruments with TID threshold of 50 krad (Si) are packaged in a vault. On the premise that one instrument’s walls are thickened to 3.5-mm aluminum, the total mass of the vault is 68.47 kg. This method is a starting point for the iterative design of the radiation vault and gives principle guidelines for the designers.