An in-flight plasma diagnostic package for spacecraft with electric propulsion

The plasma diagnostics presented in this article target the plasma surrounding a spacecraft that is created by the electric thruster and its surface modifying effects. The diagnostic package includes a retarding potential analyzer, a plane Langmuir probe, and an erosion sensor. The paper describes the instrument as well as suitable test environments for mimicking the effects expected in space and shows test results. The system is to fly for the first time on the Heinrich Hertz satellite, which is scheduled to be launched in 2023. The spacecraft will be equipped with a pair of Highly Efficient Multistage Plasma Thrusters (HEMPT) and a pair of Hall thrusters for redundancy

A coupled performance and thermal model for radio-frequency gridded ion thrusters

Recently proposed space missions such as Darwin, eLISA and NGGM have encouraged the development of electric propulsion thrusters capable of operating in the micro-Newton (μN) thrust range. To meet these requirements, radio frequency (RF) gridded-ion thrusters need to be scaled down to a few centimeters in size. Due to the small size of these thrusters, it is important to accurately determine the thermal and performance parameters. To achieve this, a multi-physics performance model has been developed, composed of plasma discharge, 2D axisymmetric ion extraction, 3D electromagnetic and RF circuit models. The plasma discharge model itself is represented using 0D global, 2D axisymmetric and 3D molecular neutral gas, and Boltzmann electron transport sub-models. A 3D thermal model is introduced to determine the temperature distribution for various throttle points, using as inputs the plasma and electromagnetic field heating values obtained from the performance model. This also allows the validation of the performance model itself. Additionally, we analyze the effect the thruster’s temperatures play on the plasma properties/performance and vice versa. The model is based on the RIT 3.5 thruster developed for the NGGM mission geometry and predicts the RIT 3.5 experimental data within approximately 10%

Parametric Study of HEMP-Thruster, Downscaling to µN Thrust Levels

Many on-going European Space Agency (ESA) science and earth observation missions are based on precision attitude control and formation flying. All these missions impose strong requirements on propulsion system which should provide low thrust, low noise, and high-precision thrust vectors in up to 16 directions. Also as most of these missions have a platform with limited solar cell arrays, the power consumption of the propulsion system should be as low as possible. The idea of using a small high-efficiency multistage plasma thruster (HEMPT) system for such missions is very attractive because of its relatively low complexity and low system mass. Thus, the ability of downscaling a HEMPT to the μN range is investigated experimentally. A measurement campaign studying systematically the influence of the geometrical dimensions of main thruster parameters on operation, beam profile, and ion acceleration is presented. Additionally the anode material was varied and showed relevance to ion acceleration distribution. The minimum achieved thrust was 50 μN at an anode voltage of 600 V, corresponding to a specific impulse of 230 s. Operation points with thrusts of 180 and 360 μN demonstrate a specific impulse of 610 and 860 s, respectively

Propulsion technologies in the frame of ESA’s next generation gravity mission

In the first decade of XXI century, European Space Agency (ESA) has extensively promoted studies in order to establish scientific requirements, identify the most appropriate measurement techniques, start the associated technology developments, and define the system scenarios for a Next Generation Gravity Mission (in brief, NGGM). Such a mission will make use of the Low-Low Satellite-to-Satellite Tracking (LL-SST) technique to monitor the temporal variations of the Earth gravity field over a long time span, like the GRACE (Gravity Recovery and Climate Experiment) mission, but with much higher spatial resolution comparable to that provided by the GOCE mission (where GOCE stands for Gravity field and steady-state Ocean Circulation Explorer), and with improved temporal resolution

Radio frequency mini ion engines for fine attitude control and formation flying applications

Many of ESA’s and NASA’s future missions are based on Formation flying, Fine attitude control and (fine) Drag compensation. As prominent examples one could mention LISA, DARWIN, PROBA-III, etc. For all these applications there is a need for propulsion system with:- High thrust accuracy and - High thrust controllabilityTaking into account, that up to 16 of these thrusters are needed for every space craft, there would be other requirements necessary: - Low mass, - High ISP, - Low power consumptionAll these requirements combined with high mission durations of up to 10 years, which enforce a life time of over 20,000hrs show the challenges, which the thruster and system designers are confronted with. University of Giessen started 2004 the works on micro Newton ion thrusters based on Radio frequency discharge. The works leaded to a miniaturized RF ion source with very low power consumption and mass, which is under industrialization to higher TR Levels under ESA contracts. The performance of such a small thruster will be presented in this paper. From the other side the whole system architecture for such a propulsion system will be discussed

The "New Grid Systems for Ion Engines" Technology Project -Results and Conclusion

Abstract: "New Grid Systems for Ion Engines" is a project in the frame of The European Space Agency ESA's Technology Research Program (TRP) aiming on a further improvement of grid systems for ion engines with respect to performance, lifetime and reliability. A consortium of European electric propulsion specialists works together on a project consisting of three phases. In the study phase improvement and validation of numerical tools for grid design was performed. In parallel, standard and advanced grid materials were investigated. From the most potential materials subscale grids were manufactured, tested and assessed. During the design phase a grid system for the BepiColombo mission and a subscale grid for future high specific impulse engines were designed and manufactured. Meanwhile the also the validation phase which contains the intensive endurance test of the grid systems is nearly completed. This paper summarizes the results of the three study phases and a first conclusion is drawn