"High-Power Hall Devices: Status and Current Challenges"

Consideration of the high power electric propulsion (EP) orbit transfer vehicles, interplanetary robotic and manned missions from one side and successful application of Hall thrusters onboard of numerous GEO satellites (Russian EXPRESS and YAMAL series), European scientific mission SMART-I on the other side stimulate interest to high power Hall devices, suitable for the future applications. Current experience for the Hall flight thrusters is limited by 1-kW-class of propulsion systems. At the same time engineering thrusters have demonstrated power level about 25 kW (Fakel Design Bureau, Russia) and almost 100 kW (NASA GRC) with using xenon as a propellant, 150 kW for bismuth thruster (TSNIIMASH, Russia). It is necessary to underline, that principal limits have not been identified for the further increasing of the thruster size and power. This makes the Hall devices at least very competitive for high power application as compared with other types of electric thrusters: MPD and ION thrusters. For high power EP systems two typical operation modes may be considered, namely "high specific impulse (Isp)" and high thrust" modes. Correspondingly challenges to develop Hall EP system are different for each one. For high thrust" mode the development issues associate with increasing of propellant flow and thruster size. Discharge voltage to get "high thrust" regime with best power-to-thrust ratio should be 150..300 V, and it is inside of well studied operation range of Hall thrusters. For "high Isp" mode required discharge voltage in several times than one for flight qualified Hall EP systems, while mass flow does not essentially exceed already achieved level.