Performance investigation of zinc propellant in sub kW class hall thrusters

Abstract

Zinc was successfully integrated and tested in sub-kW class Hall thrusters as an alternative propellant to xenon. The advantages of zinc include a high storage density, low first ionization energy, potentially high specific impulse and low cost. The third iteration (Mark 3) of a novel propellant storage and delivery system (PSDS) for solid propellants was tested and experimentally characterised, demonstrating operational zinc outputs up to 0.36 mg/s in sublimation mode with a peak of 8.2 mg/s near the melting point of zinc. The PSDS power consumption was approximately 20-30 W during thruster operation and 50 W in the start-up sequence. A 100 W laboratory cylindrical Hall thruster (CHT-100) was modified structurally and magnetically to couple with the PSDS Mark 3. Performance was measured during thruster operation on xenon, krypton and zinc with a mass flow rate of 5 SCCM to 10 SCCM, a discharge power of 50-150 W and an electromagnet current of 0.8 A on the main solenoid and 1.0 A on the secondary solenoid. Measured thrust was 1 mN during operation on zinc at an input power of 80 W and 1.2 mN during operation on krypton at an input power of 98 W. At an input power of 80 W the maximum measured specific impulse was 448 s during operation on zinc and 371 s during operation on krypton. Demonstration of throttling and PSDS redundancy in failure mode operation is discussed, as well as deposition and channel erosion.

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