Progress in Testing of QM and FM HEMP Thruster Modules

Thales Electronic Systems GmbH develops and qualifies an electric propulsion system based on the High Efficiency Multistage Plasma Thruster (HEMPT). The HEMPT Assembly is being developed under the HEMPTIS DLR contract. It shall be used in the frame of the ESA (SGEO) program, the platform developed by OHB System AG for the Hispasat AG1 mission. Four HTM Flight Models (FM) and one HTM Qualification Model (QM) were characterized for initial performance according to the acceptance/qualification program by now. These tests included a HTM long-time operation at the nominal operation point (>4 h @1000V, 1.38A), a characterization in t he range of anode voltages 850..1050V and anode currents 0.3..1.45A, three nominal operation pulses (with typical mission firing duration of 40 min each) at different HTM interface temperatures, as well as the plasma beam characterization. The HTM FMs and HTM QM comply with the requirements, operated stable in the whole range of voltages and currents and have low performance variation. In particular, the thrust was ≥44 mN and the total specific impulse >2400s. Beam characterization confirmed the compliance to the re quirements on the plasma beam sputtering ability. The HTMs demonstrated a stable and reproducible ignition of neutralizer and thruster.