SmallSat Missions Enabled by Paired Low- Thrust Hybrid Rocket and Low-Power Long-Life Hall Thruster

The capabilities of a SmallSat-class spacecraft targeting the outer solar system and using a combined chemical and electric propulsion system are explored. The development of compact hybrid rockets has enabled high-thrust engines to be packaged tightly enough to fit on CubeSat and SmallSat spacecraft. These hybrid rockets provide 10's-100 N of thrust depending on the propellant load >300 s of specific impulse and have been demonstrated in both ambient and vacuum environments. Advancements in low -power long-life Hall thruster technologies have provided the potential for significantly greater propellant throughputs, enabling their use as a primary propulsion element on interplanetary spacecraft. In a recent characterization test campaign, the MaSMi-DM Hall thruster demonstrated power throttling from 150 -1000 W with >1500 s of specific impulse available at >500 W and ≥40% total thrust efficiency available at >300 W; peak values of 1940 s and 53%, respectively, were observed. A notional low-mass spacecraft employing a combined hybrid rocket and low-power electric propulsion system was designed and used for mission concept analysis targeting the outer solar system. Using an imposed wet mass limit of 400 kg, mission trajectories to Saturn and Uranus were generated. Orbit capture with >40% of the launch mass was shown to be possible at either target, with mission transfer times of 7.5 years and 13.5 years for Saturn and Uranus, respectively. Significant follow-on mission activities near Saturn (e.g. to Titan Enceladus) were also possible by carrying extra propellant mass while remaining under the total wet mass limit.