Plasma propulsion for three terrestrial planet finder architectures: Free-flying, monolithic and tethered

A systems-level trade-off study is presented comparing the propulsion requirements and associated final masses for different architectural implementations of the Terrestrial Planet Finder (TPF) mission. The study focuses on the mN-level propulsion chores associated with rotation and repointing. Three interferometer configurations; free-flying, monolithic and tethered; lead to estimates of power requirements and spacecraft masses associated with different plasma propulsion systems required to maneuver the interferometer throughout its lifetime. The parametric study includes the following plasma propulsion options: Hall thruster, Field Emission Electric Propulsion (FEEP), Ablative Pulsed Plasma Thruster (APPT), Ablative Z-pinch Pulsed Plasma Thruster (AZPPT) and Gas-Fed Pulsed Plasma Thruster (GFPPT). For the different thruster and architecture combinations, it is found that the initial mass for a system falls between 3200 and 4200 kg. Also, in general, for a given architecture, the tether has the lowest initial mass followed by the free flyer and the monolith. Finally, the initial mass was found not to be particularly sensitive to the type of plasma propulsion system so the choice should be made based on technological readiness, systems integration considerations and spacecraft contamination issues associated with the chosen system.