Plasma Propulsion Options for Multiple Terrestrial Planet Finder Architectures

A systems-level trade study is presented comparing the propulsion requirements and associated Ž nal masses for different architectural implementations of the Terrestrial Planet Finder mission. The study focuses on the millinewton-level propulsion chores associated with rotating and repointing an array.Three interferometer conŽ gurations, free  ying, monolithic, and tethered, lead to estimates of thrust and power requirements and spacecraft masses associated with the different plasmapropulsion systems required to perform maneuvers throughouta mission. The parametric study includes the following plasma propulsion options: Hall thruster, Ž eld emission electric propulsion, ablative pulsed plasma thruster, ablative Z-pinch pulsed plasma thruster, and gas-fed pulsed plasma thruster. Not all of the thrusters considered can perform the necessary propulsive chores for each architecture, but for the most promising thruster and architecture combinations, it is found that the initial mass for a system falls between 3050 and 4060 kg. The tether, in general, possesses the lowest initial mass of the three architectures followed by the free  yer and the monolith. Finally, the thrust-to-power ratio, maximum deliverable thrust or impulse bit, and capability of a propulsion system to process enough power to produce a required thrust level are shown to be more important factors than the speciŽ c impulse in determining the proper thruster choice for moderate to high thrust maneuvers.