Design of Jupiter Europa Orbiter Using Emerging Radioisotope Power System Technologies

Abstract

This study analyses a single Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) unit, and two Stirling Radioisotope Generator (SRG) units for powering Jupiter Europa Orbiter. The RTG power system will independently produce an uninterrupted power supply, as opposed to a solar powered orbiter, as studied by Astrium for ESA, which depends on distance from Sun, eclipse and Jupiter’s occultation. The orbiter’s thermal control system uses excess heat from the RTG to maintain the spacecraft’s temperature using a heat transfer loop. The additional heat loads received by the spacecraft during Venus and Earth flybys are removed with this heat transfer loop through the RTG radiators. The MMRTG provides a continuous power output of 110 W with a 13% reduction in mass compared to a solar powered equivalent. The total radiation dose from the MMRTG is about 5 krad behind 10 mm aluminium shielding, which is much lower than the expected mission natural radiation dose. The electromagnetic interference produced by the MMRTG magnetic field strength is only 17 nT which is less than the NASA standard requirement of 25 nT at one meter distance. The power system with two SRG units has an overall mass saving of 9% compared to the solar cell equivalent and requires only four General Purpose Heat Sources (GPHS) to produce 220 W of electrical power. It emits less radiation and has a weaker magnetic field than the MMRTG. Results show that a Jupiter Europa Orbiter spacecraft designed with single MMRTG unit or with two SRG units as power source would be the best choice for the proposed ESA Jovian Minisat Exploration mission.