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... Electric space engines have evolved out of their shadowy existence due to the abovementioned strong points.  There are a large number of different types of EP systems, some still at a conceptual level, others already at a very high technological maturity level, and a few already in use in space (cf. Fig. 4). ...
The transition from OLD SPACE to NEW SPACE along with increasing commercialization has a major impact on space
flight in general and on electric propulsion by ion thrusters in particular. Ion thrusters are nowadays used as primary
propulsion systems in space. The article describes how these changes related to NEW SPACE affect various aspects that
are important for the development of electric propulsion systems. Starting with a historical overview of the development
of space flight and of the technology of electric propulsion systems, a number of important missions with EP and the
underlying technologies are presented. The focus of our discussion is the technology of the radio frequency ion thruster
as a prominent member of the gridded ion engine family. Based on this discussion, we give an overview of important
research topics such as the search for alternative propellants, the development of reliable neutralizer concepts based
on novel insert materials as well as promising neutralizer-free propulsion concepts. In addition, aspects of thruster
modeling and requirements for test facilities are discussed. Furthermore, we address aspects of space electronics with
regard to the development of highly efficient electronic components as well as aspects of electromagnetic compatibility
and radiation hardness. The article concludes with a presentation of the interaction of electric propulsion systems with
High Voltage Power Modules for Electrical Propulsion have been developed for the European Space Agency's GOCE and ALPHABUS missions, featuring Kaufmann-Type Ion Tiirusters with power levels between 520W and 4.8 kW and output voltages from 1200V to 2000V. Based on these developments a new concept lias been established for modular generic power modules being able to drive various types of ion thrusters, including the new HEMP electric propulsion technology. Initial results have demonstrated that module efficiency can be increased to 97% by introduction of the Flattop ZVS converter especially designed for high voltage applications.