Spacecraft interaction test results of the high performance Hall system SPT-140

Abstract

Ground rests were performed to help characterize modes of interaction between the SPT-140 Hall thruster and spacecraft components. The experiments were performed at NASA Glenn Research Center and at the University of Michigan. Measurements were made of thruster plume current density, electromagnetic interference (EMl), and surface sputtering and contamination. Diagnostics included Faraday probes, collimated sputter/deposition targets, and radio-frequency detectors. Ion current density measurements showed exponential decay with off-axis angle up to approximately 30 degrees. At off-axis angles greater than 30 degrees, results varied with chamber background pressure, presumably due to ambient charge exchange plasma. Sputter rates of solar cell coverglass. Kapton, and RTV were accurately measured I in from the thruster exit for off-axis angles less than 60 degrees. At off-axis angles greater than fiO degrees, the sputter rate was on the order of the measurement uncertainty. EMl tests found very little emission in the traditional RF communication bands. At the lowest frequencies, one band of E-field emission (10 kHz to 20 MHz) was detected which exceeded the MlL-STD-461C specification b\ up to 53 dB.

Pressure Map of a Facility as a Function of Flow Rate to Study Facility Effects

“…6 Several investigations are underway to numerically model thruster performance and the interactions between Hall thrusters and spacecraft. 7,8 The results of these models are highly dependent on experimentally measured boundary conditions. One of the most important auxiliary inputs required by these codes is background pressure of a laboratory vacuum chamber.…”

Numerical Simulation of Probe Measurements in a Non-equilibrium Plasma

“…Common experimental diagnostics include the Faraday cup, Langmuir probe, and Retarding Potential Analyzer (RPA). [3][4][5] Each of these instruments is immersed in the exhaust plume and may affect the plasma condition with both physical obstruction and electrostatic sheaths. These effects make it difficult to recover undisturbed plasma conditions from the measurements.…”

The Performance and Plume Characterization of a Laboratory Gridless Ion Thruster with Closed Electron Drift Acceleration

“…This ion density profile can be integrated to determine total ion current and ion beam plume divergence. The total ion current in the plume, calculated from ion current traces measured with simple Faraday over estimates the ion current by as much as 200% [11,38]. This over prediction has been attributed to the influence of low energy background ions such as those created through chargeexchange (CEX).…”