Effect of Voltage Level on Power System Design for Solar Electric Propulsion Missions

Abstract

This paper presents study results quantifying the benefits of higher voltage, electric power system designs for a typical solar electric propulsion spacecraft Earth orbiting mission. A conceptual power system architecture was defined and design points were generated for system voltages of 28-V, 50-V, 120-V and 300-V using state-of-the-art or advanced technologies. A 300-V “direct-drive” architecture was also analyzed to assess the benefits of directly powering the electric thruster from the photovoltaic array without up-conversion. Fortran and spreadsheet computational models were exercised to predict the performance and size power system components to meet spacecraft mission requirements. Pertinent space environments, such as electron and proton radiation, were calculated along the spiral trajectory. In addition, a simplified electron current collection model was developed to estimate photovoltaic array losses for the orbital plasma environment and that created by the thruster plume. The secondary benefits of power system mass savings for spacecraft propulsion and attitude control systems were also quantified. Results indicate that considerable spacecraft wet mass savings were achieved by the 300-V and 300-V direct-drive architectures.

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“…This efficient electrical performance would make SiC ideal for certain kinds of space applications where high voltage operation could play a key role. One concept is Solar Electric Propulsion (SEP), proposed by NASA and other space agencies to create a "Tugboat" that could transport material around the inner solar system without large amounts of liquid or gas propellant [2]. The idea is to have a very large solar array with a high bus voltage that could produce power in the range of 10 kW or greater, which would be used to power an ion propulsion drive.…”