Performance of a low-power ablative Z-pinch pulsed plasma thruster with PTFE-Cu propellant under alternative cathode configurations

Abstract

With a unique front-back coaxial configuration, ablative Z-pinch pulsed plasma thruster (AZPPT) possesses the advantages of a high thrust to power ratio at low power and a simple structure which make itself suitable for small and Nano satellites applications. However, the specific impulse of AZPPT is relatively low, limiting its further application expansion. Therefore, a performance study on a low-power AZPPT adopting a novel alternative propellant of PTFE impregnated with Cu was conducted. The impulse bit, ablation mass, and discharge characteristics of the thruster are obtained and compared under different conditions of Cu fractions in PTFE-Cu propellant, cathode orifice diameters and nozzle configurations. Experiments show that the specific impulse of PTFE-5%Cu is 24 % higher than that of pure PTFE. Triple Langmuir probe indicates that such improvement is caused by the effectively increased ionization rate of ablated propellant and weakened late-time ablation effect. The results also show that the cathode with larger orifice reduces the impulse bit, but increases the specific impulse and effectively reduces the plume divergence angle. Moreover, nozzle configuration hardly affects the ablation characteristics, but shows a significant influence on the impulse bit by converging the plasma plume. The specific impulse with a divergent nozzle can reach 629.5 s at the discharge energy of 5 J, which is 14.89 % higher than that without a nozzle. These detailed insights for the first time clear the influence of impregnated propellant and cathode configuration on the low-power AZPPT, providing new ideas for the performance optimization of AZPPT.