Architecture, Functional Features and Operational Characteristics of the HEMPT based Ion Propulsion System for SmallGEO

Thales Electron Devices GmbH has developed and is currently qualifying a novel electric propulsion System, the so called HEMP Thruster Assembly (HTA). The HTA uses a lean topology and design, providing a cost effective solution for commercial geo- stationary satellites. This is achieved by a modularized design of each propulsion unit (HTM) that results also in complete interchangeability. A set of HTMs can be operated from one power supply module without any switching matrix, since HTMs are designed to support a clustered operation. Thrust control can be achieved by control of the propellant throughput only including switch off. This has been utilized for the HTA to reduce the amount of needed power supplies for the thrusters to one high voltage supply for all thrusters, with a second supply in cold redundancy. Also no additional sensors are required for the flow control unit, as the thruster itself is used for the feedback signal to control thrust by propellant flow. In addition the HTM units are designed to be integrated without dedicated pointing mechanisms. In this paper the architecture and the operational and performance characteristics of the HEMPT Assembly ion propulsion system will be presented.