Overview of the Development of the Solar Electric Propulsion Technology Demonstration Mission 12.5-kW Hall Thruster

Abstract

NASA is developing mission concepts for a solar electric propulsion technology demonstration mission. A number of mission concepts are being evaluated including ambitious missions to near Earth objects. The demonstration of a high-power solar electric propulsion capability is one of the objectives of the candidate missions under consideration. In support of NASA's exploration goals, a number of projects are developing extensible technologies to support NASA's near and long term mission needs. Specifically, the Space Technology Mission Directorate Solar Electric Propulsion Technology Demonstration Mission project is funding the development of a 12.5-kW magnetically shielded Hall thruster system to support future NASA missions. This paper presents the design attributes of the thruster that was collaboratively developed by the NASA Glenn Research Center and the Jet Propulsion Laboratory. The paper provides an overview of the magnetic, plasma, thermal, and structural modeling activities that were carried out in support of the thruster design. The paper also summarizes the results of the functional tests that have been carried out to date. The planned thruster performance, plasma diagnostics (internal and in the plume), thermal, wear, and mechanical tests are outlined. AbbreviationsAFRL = Air Force Research Laboratory ARRM = Asteroid Retrieval and Redirect Mission GRC = Glenn Research Center HEFT = Human Exploration Framework Team HEOMD = Human Exploration and Operations Mission Directorate JPL = Jet Propulsion Laboratory MS = Magnetically Shielded

Finite Pressure Effects in Magnetically Shielded Hall Thrusters

“…The reduced sensitivity of internal cathode configurations has manifested itself in multiple ways, primarily how the thrust, RMS oscillations, power spectral density of the current, and cathode potential respond to pressure changes relative to when the external cathode is used. The testing methodologies developed here will next be implemented in studies of a 12.5 kW Hall thruster now under development by NASA GRC and JPL in support of the Solar Electric Propulsion Technology Demonstration Mission [55].…”

“…We seek in these investigations to: 1) develop the methodologies to measure accurately pressure effects so that they can be applied to other thrusters under development by NASA [55], and 2) assess whether ground tests of highpower Hall thrusters can be relied on as reliable predictors of flight performance. We begin by reviewing the effects of neutral ingestion and cathode position on Hall thruster operation.…”

Near-Surface Plasma Characterization of the 12.5-kW NASA TDU1 Hall Thruster

“…Facility pressure for this study was monitored by four hotcathode ionization gauges, three mounted near the thruster and a fourth mounted on the facility wall mid-section. 7 Ionization gauge #2, mounted at approximately 1 o'clock with respect to the thruster when looking upstream, was pointed towards the facility wall and used as the primary gauge in this study (see Fig. 2).…”

“…The HERMeS thruster is a 12.5-kW class, highly throttleable Hall thruster capable of specific impulses up to 3000 s. The thruster has undergone extensive performance and thermal characterizations at NASA GRC within VF-5. 6,7 For this study, the thruster was placed in the main volume of the facility to assure the lowest possible backpressure conditions were attained during thruster operation. Figure 2 shows a photograph of TDU1 mounted within VF-5 just prior to testing.…”

“…TDU1 has undergone extensive performance and thermal characterization at NASA GRC, with wear testing planned for the near future. 6,7 Performance and environmental testing are currently planned for TDU2 at JPL.…”