Characterization of a high-power Hall thruster operation in direct-drive

In Hall propulsion systems, a direct and non-isolated connection between the thruster discharge and the solar array implies a significant change in terms of spacecraft grounding, thruster operation and control. In this so-called direct-drive architecture, since discharge voltage and current are no more fixed by a power processing unit but are constrained by the solar array characteristic, which changes during a space mission, specific control laws need to be developed and tested to assess the feasibility of thruster operation. In this paper, in-depth investigations performed in SITAEL on thruster performance and operation controllability of a direct-drive Hall thruster system are presented. The HT5k, a 5 kW-class Hall thruster, was connected to a solar array simulator (SAS) and tested at different operating conditions. Three different thruster control laws were implemented and were proved effective in controlling the thruster behavior with respect to on-orbit-representative variations in the SAS characteristics. The results also highlighted minimal difference between thruster performance parameters in direct-drive and with a conventional power supply. Finally, the impact of grounding on thruster plume interaction with the spacecraft was analyzed.