Performance evaluation of a low energy pulsed plasma thruster / Lee Hong Chun

Lee , Hong Chun (2024) Performance evaluation of a low energy pulsed plasma thruster / Lee Hong Chun. PhD thesis, Universiti Malaya.

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Abstract

Pulsed Plasma Thruster (PPT) is an established electric propulsion system with low cost and simple design. The research on PPT has grown a lot recently due to the demand and increasing interest in low cost and miniature sized satellites. In the PPT, plasma is produced through the surface breakdown of solid PTFE propellant, with the resulting selfinduced Lorentz force propelling the plasma to generate thrust. In this work, the performance of a side-fed, tongue-flared PPT operated at a range of lower discharge energy of 0.5 to 2.5 J has been investigated. The tongue-flared electrode geometry and side-fed polytetrafluoroethylene (PTFE) solid propellant configuration are used as these have been known to produce excellent thrust efficiency. The impulse bit (Ibit), specific impulse (Isp), mass bit (mbit) and thrust efficiency (η) are measured by a torsional thrust stand and these performance parameters are compared to those reported in other PPTs of similar range of discharge energy. Degradation of the solid PTFE propellant is evaluated from the Field Effect Scanning Electron Microscopy (FESEM) imaging and Energy Dispersive X-Ray (EDX) analysis of the PTFE bars after 10,000 discharges. It is found that at discharge energy around 2 J and above, the performance parameters are consistent with those in other PPT systems of similar configuration. Discrepancy observed at energies below 2 J is attributed to the low mass bit related to the discharge behaviour. Triple Langmuir probe is used to measure the spatial distribution of the plasma characteristics, such as electron temperature, Te and electron density, ne. These measurements were carried out up to 30 degrees angle from the centreline. The velocity of plasma ions was determined by calculating transit times from the point of initial surface discharge on the PTFE surface to the probe locations. It showed non-symmetry behaviour in the perpendicular plane, this afforded us a better overall view on how the plasma plume expanded and could facilitate further model simulations of PPT. Comparison with other PPT systems which were operated at a wide range of energies validated this low energy PPT. The measured values of Te and ne were consistent with those reported for other PPTs within the same order of energy range.

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