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 (EP) by ion thrusters, in particular. Ion thrusters are nowadays used as primary propulsion systems in space. This article describes how these changes related to NEW SPACE affect various aspects that are important for the development of EP systems. Starting with a historical overview of the development of space flight and of the technology of EP 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. This article concludes with a presentation of the interaction of EP systems with the spacecraft.

No abstract

Die um Größenordnungen höhere Treibstoffeffizienz elektrischer Weltraumantriebe gegenüber chemischen motiviert deren Nutzung für die Lage‐ und Bahnstabilisierung, für Spiralflüge auf höhere Orbits (orbit raising) sowie für interplanetare Raumflüge. Ganz besonders hohe Effizienz bieten Radiofrequenz‐Ionentriebwerke (RIT), da sie den Schub über Ionen eines Plasmas erzeugen, die in einem elektrostatischen Feld sehr stark beschleunigt werden. Dieser Artikel beschreibt die grundlegenden physikalischen Zusammenhänge innerhalb dieser Triebwerke, die zu einer hocheffizienten, feinst dosierbaren Schubgenerierung beitragen. Weiterhin wird eine ganzheitliche Betrachtung des Antriebssystems geliefert, indem besonders auf den energieeinspeisenden Radiofrequenz‐Generator (RFG), der maßgeblich den Gesamtwirkungsgrad des Antriebssystems definiert, eingegangen wird. Als forschungsintensiver Ausblick werden alternative Treibstoffe zur Bereitstellung des notwendigen Plasmas diskutiert, welche die Kostenbilanz einer Mission erheblich begünstigen könnten.

An important task in the development of electric propulsion devices is ground-based testing. In order to characterize electric thrusters, their generated ion beams are regarded as figures of merit and have to be well-known and understood. We present an approach to measure DC ion beam currents generated by electric thrusters by means of an inductive direct-current current transformer. In contrast to commonly used devices like Faraday cups, this device can measure the beam current non-intrusively by means of magnetic field coupling rather than charge collection. This paper shows the development of a prototype sensor which can measure currents in the typical range for electric thrusters with high resolution and satisfactory accuracy. A detailed SPICE model to assist during hardware development is also introduced and verified by test case measurements. The prototype has been tested and validated with a radio-frequency ion thruster. Its readout shows very good agreement with the output of an analytical model which computes a Gaussian-shaped ion beam in the far-field based on experimental input data.