Investigating the impact of electrode materials on the erosion characteristics of pulsed plasma thrusters

Pulsed plasma thrusters (PPTs) are a type of electric propulsion device that generates thrust in space by using an arc discharge to produce a high-speed plasma plume. Despite their low power requirements and miniaturization advantages, PPTs still face challenges related to electrode erosion due to high discharge energy and extremely short arc durations. This study investigates the effects of electrode materials on the erosion characteristics of a 2.5 J PPT prototype. The discharge behavior, plasma morphology, and thrust performance were evaluated using three different electrode materials: copper, tungsten, and graphite, with polytetrafluoroethylene (PTFE) as the propellant. Emission spectroscopy of the PPT reveals distinct erosion and ionization information, as all the elements participate in the ionization process, and erosion occurs. Tungsten exhibited minimal erosion compared to copper and graphite. Long-exposure broadband emission images of the discharge morphology of the three distinct electrodes reveal significant changes in luminous discharge morphology, with tungsten exhibiting better plasma collimation and minimal erosion spots. For the discharge characteristics, tungsten has the most significant initial voltage drop and a more substantial negative peak voltage (−780 V) compared to copper (−500 V) and graphite (−580 V). Thrust measurements highlight performance variations across electrode materials; at 1500 V, tungsten demonstrates an impulse bit of 82 μNs, about 5 % higher than copper's 78 μNs and 16 % higher than graphite's 65 μNs. Since the heat transfer properties of the material also affect the erosion, further multi-physics simulation is conducted to predict the influence of electrode materials due to heat flux. Tungsten demonstrates better erosion performance compared to copper and graphite under high-current conditions. Similar trends were observed at both 2.5 J and 10 J energy levels. The experimental and simulation results in this study will aid in selecting suitable electrode materials to improve PPT performance and reliability.