Influence of sharp geometry on pulsed plasma thruster plume dynamics

This study investigates the influence of sharp electrode geometry on discharge behavior and plume characteristics in pulsed plasma thrusters (PPTs), aiming to improve plume collimation and discharge repeatability. Conventional parallel-plate PPTs often suffer from plume divergence and discharge instability due to non-uniform electric fields and stochastic ablation. To address these limitations, sharp electrodes were introduced to intensify the local electric field and concentrate discharge activity. Ion velocity and flux distributions were measured using a fast Faraday cup, while high-speed imaging with spectral filters captured the spatiotemporal evolution of charged and neutral species. Compared to planar electrodes, sharp electrodes demonstrated a 13.5 % increase in average axial ion velocity (17.95 km/s vs. 15.82 km/s) and an 11.9 % enhancement in centerline ion flux. Surface analysis revealed localized erosion at the electrode apex, confirming focused ablation behavior. Filtered optical diagnostics identified distinct emission layers corresponding to ionized carbon (C⁺) and molecular carbon (C₂), revealing velocity stratification and differential confinement within the plume. Sharp electrodes exhibited superior collimation and directional stability, driven by enhanced Lorentz acceleration along the central axis. In contrast, planar configurations produced broader, less confined plumes with greater off-axis ion flux and random deflection. These results highlight the advantages of sharp electrode designs in improving discharge repeatability, ionization efficiency, and thrust directionality. The findings contribute to the development of more stable and efficient micro-propulsion systems for CubeSat and small satellite applications, where high specific impulse and precise attitude control are essential.