Numerical simulations of the XR-5 Hall thruster for life assessment at different operating conditions

Abstract

NASA's Jet Propulsion Laboratory has been investigating the applicability of Aerojet Rocketdyne's XR-5 thruster, a 4.5 kW class Hall thruster, for deep-space missions. Major considerations for qualifying the XR-5 for deep-space missions are demonstration of a wide throttling envelope and a usable life capability in excess of 10,000 h. Numerical simulations with the 2-D axisymmetric code Hall2De are employed to inform the qualification process by assessing erosion rates at the thruster surfaces in a wide range of throttling conditions without the need for conducting costly endurance testing. In previous work at JPL by Jorns et al., the anomalous collision frequency distribution for 11 different throttling conditions of the XR-5 spanning 0.3-4.5 kW were identified based on probe measurements of the electron temperature in the near plume region. In this paper, we provide estimates for the erosion rates at the channel walls and pole covers for the same 11 conditions. Uncertainties in the plasma measurements and in the anomalous collision frequency distribution are addressed by determining upper and lower bounds of the erosion rates. Results suggest that erosion of the walls only occurs in the last 5% of the acceleration channel and the rate of such erosion decreases as the geometry of the thruster changes in time due to magnetic shielding. A quasi-zero-erosion state is eventually achieved in all the examined throttling conditions. Examination of the results for pole surface erosion and estimated cathode life indicates that the XR-5 propellant throughput capability will exceed 700 kg, which provides 50% margin over the usable throughput capability of 466 kg as already demonstrated in wear testing

Facility pressure effects on a Hall thruster with an external cathode: I. Numerical simulations

“…We present a numerical investigation of the effects of vacuum facility backpressure on the performance and life of Hall thrusters using the SPT-140 as a benchmark. We employ Hall2De [16,17], a 2D axisymmetric (r-z) scientific code that has been used in the past to investigate performance [18][19][20][21] and erosion rates [18][19][20][21][22][23][24] of multiple Hall thrusters including the H6 [18,20,21,24], HERMeS [23], and the XR-5 (formerly, the BPT-4000) [19,22]. Hall2De was also employed in the development and demonstration of magnetic shielding [19].…”

Predictive, data-driven model for the anomalous electron collision frequency in a Hall effect thruster

“…These latter measurements are informed by probeand laser-based techniques for measuring the plasma (see [53,54]). Using the numerical inversion technique, Hall2De has been shown to yield numerical results that are quantitatively consistent with many aspects of experimentally-measured thrusters (see [49,55,56]). Moreover, the empirically determined collision frequency profiles found with this technique exhibit qualitatively and quantitatively similar features to the profiles that actually have been measured with direct probing techniques (compare, e.g.…”

Trends in mass utilization of a magnetically shielded Hall thruster operating on xenon and krypton

“…We used Hall2De, a 2D axisymmetric multi-fluid/particle-incell (PIC) Hall thruster code developed at the Jet Propulsion Laboratory [23,35,42], as our virtual diagnostic to infer internal plasma properties.…”

“…We note here that a weakness of this approach is the relatively poorly-calibrated electron temperature in the simulations, which is determined by the electron energy equation. Previous simulation efforts have revealed the difficulty of calibrating both electron temperature and ion velocity simultaneously [35,42]. Given the availability of the ion velocity profiles, we use this as our calibration metric.…”