Nuclear power for Mars surface

Safe, reliable, low-mass, low-volume, long-life nuclear fission power supplies are an attractive option for meeting lunar and Martian surface power requirements. Two factors will have a strong impact on the suitability of a surface nuclear power supply: the technology used by the reactor and the overall system mass. Because thermionic technology is well suited for surface applications, this paper briefly discusses the existing 6 kWe Russian TOPAZ II reactor and two near-term US thermionic space nuclear power supplies capable of providing 40 kWe. Man-rated shielding will be a significant fraction of the mass of any surface nuclear fission power supply. Because of the importance of optimizing the reactor shield, this paper presents detailed calculations related to the shielding properties of lunar and Martian soil, and the effectiveness of using existing craters to shield a reactor. Preliminary results indicate that it may be desirable to incorporate neutron shielding into the reactor design, but when possible in-situ materials should be used. Preliminary calculations also indicate that while existing craters could provide substantial shielding, radiation scatter off of the crater rim may limit the overall shielding effectiveness of the crater. 7 refs