The ablation and ionization characteristics of a rectangular pulsed plasma thruster with hydroxy-terminated polybutadiene propellant

Pulsed plasma thrusters (PPTs) are attractive micro-thrusters for their advantages such as compactness and lightweight compared to other electric propulsion systems. Accordingly, PPTs have been used in station-keeping, drag makeup, and attitude control for small satellites. Instead of the most common PPT propellant PTFE (polytetrafluoroethylene), hydroxyl-terminated polybutadiene (HTPB) propellant was used and some interesting experimental results were obtained; however, the ablation and ionization characteristics of such propellant have never been investigated. In this research, performance experiments using rectangular breech-fed PPT were conducted with HTPB propellant. Mass shot, electrical parameters, and plasma properties were obtained. The ablation process was further analyzed from three perspectives: electrical thermal energy, chemical energy, and ablation energy. The experimental result shows that all mass shots of different HTPB propellants are less than that of PTFE propellant, and the mass shot of HTPB propellant increases with increasing oxidant content. The difference in ablation between HTPB propellant and PTFE propellant could be explained by ablation energy while the difference between HTPB propellants with different proportional compositions could be elucidated by chemical energy. It was observed that the electron densities of these two kinds of propellants were not significantly different. This could be explained by the fact that HTPB propellant produced about three times more electrons than PTFE did even though less mass shot was produced by HTPB propellant.