Performance characterization and optimization of a diverging cusped field thruster with a calibrated counter-weighted millinewton thrust stand

Abstract

The previously developed Diverging Cusped Field Thruster (DCFT) has undergone further investigations and performance characterization. The DCFT is a magnetically conned plasma thruster that uses cusped magnetic fields to confine electron ow and reduce losses to the walls. The magnetic confinement of the plasma away from the walls also reduces wall erosion to increase thruster lifetime. Additionally, modifications to the original DCFT have increased robustness and decreased mass to become more desirable for space flight. Research on reducing the plasma plume divergence of the thruster by altering the magnetic field has also been performed. The DCFT has exhibited competitive thrust and eciency performance when compared to typical Hall thrusters of similar size. Specifically, the anode eciency reached a maximum of 39.3% providing 11.8 mN of thrust with a specific impulse of 1436 s. The xenon mass ow rate to the anode was 8.5 standard cubic centimeters per minute, and the power consumption was 210 W. Two distinct modes, as well as a "mixed" mode, were observed during performance testing and had signicant, though not completely predictable, effects on thruster performance. The modes differ in plasma diffusivity and anode current. Facility effects, such as chamber back pressure and cathode coupling, on performance were also briefly y researched. In order to characterize the performance of the DCFT, the Milli-Newton Thrust Stand (MiNTS) was developed. The MiNTS is a non-conventional torsional-style thrust stand capable of measuring thrust in the range of 3 to 20 mN with an accuracy of up to 0.2 mN. Calibration of the stand is necessary to map the output of the MiNTS to the force felt by it. A calibration stand was designed to apply a known force to the MiNTS using weights. The MiNTS is controlled by a Labview Virtual Instrument that can measure and counteract the force of the DCFT. Drift forces due to external connections to the MiNTS and thermal transfer from the DCFT are also studied, and processes for negating the drift forces are provided.