Design Development and Test of the RIT-ÁX Mini Ion Engine System

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Thrust [µN] 500 450 400 350 300 250 200 150 100 50 12:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 Time [hh:mm] THRUST Figure 5 RIT-µX 50µN Thrust stepping Figure 6 Thrust linearity Thrust [µN] 550 500 450 400 350 300 250 200 06:15 06:30 06:45 07:00 07:15 07:30 07:45 Time [hh:mm] THRUST Figure 7 Thrust Stepping I - wide thrust range variation Thrust [µN] 500.5 500.4 500.3 500.2 500.1 500.0 499.9 499.8 499.7 499.6 Window for Data Evaluation 499.5 04:30 07:30 10:30 01:30 04:30 07:30 10:30 Time [hh:mm] THRUST Main Door of Gießen Test Vacility opened 0 0 100 200 300 400 500 8 The 31st International Electric Propulsion Conference, University of Michigan, USA September 20 – 24, 2009 Thrust Response Value [µN] Thrust [µN] 500 400 300 200 100 510 505 500 495 490 Thrust Set-Value [µN] THRUST Linear Fit of Dlin3_THRUST 06:40 06:45 06:50 06:55 07:00 07:05 07:10 07:15 07:20 07:25 Time THRUST Figure 8 Thrust Variation II - Small varaitions on the maximum nominal thrust level Thrust Noise Density [N/Hz^0.5] 1E-5 1E-6 1E-7 1E-8 LISA Requirement Frequency of Cryo Pumps 1E-9 1E-4 1E-3 0.01 0.1 1 10 Frequency [Hz] Figure 9 Thrust vs. time plot for the 500µN Figure 10 Thrust noise density - 500µN Thrust
VI. Conclusion and Outlook The development of a RIT-µX miniaturized ion engine elegant breadboard model has been successfully completed. In an extensive functional test campaign the basic thruster performance has been mapped. For the desired thrust range, 50-500µN, specific impulse and power consumption are available. The performance has been mapped also for lower and higher thrust levels. When sufficient power is available on board the spacecraft, RIT-µX is fully operable in an extended thrust range. With pervance tests the full thrust range has been validated with respect to the dynamic of ion optics. EBS tests showed that the dangerous effect of back streaming electrons is not critical for small ion engines. Especially, when operated with a gasless neutralizer the maximum available electron current is limited. Moreover, the ion optics design shows ample margins. Controllability and thrust noise are key issues for high precision low thrust systems. RIT-µX shows an impressive performance: The function between commanded thrust and thrust response is highly linear. The engine is mastering both small thrust variations and large thrust stepping. A thrust resolution better than +/- 0.1µN is found. The tests show clearly that that the limits for thrust resolution and controllability are given by the thruster electronics and not by the thruster itself. Finally, first thrust noise measurements have been performed. The measurement shows an electric thrust noise even bellow the limits for ESA's challenging LISA mission. In a first endurance test the engine has been operated for more than 1,700 hours at a constant thrust level of 500 µN. The results will be published in a separate document. Meanwhile the European Space Agency has extended the baseline contract for the described activity. In the frame of the extension all steps for the RIT-µX qualification will be performed. Completion of the qualification is scheduled for the second half of 2010. In parallel, ESA has granted contracts for the development of thruster electronics (Astrium Satellites, Friedrichshafen, D) and a dedicated flow control unit (Nanospace, S). A coupled system test is planned before end of 2010. References [1] D. Feili et al.: Testing of New µN-RITs at Giessen, AIAA-2005-4263 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Tucson, Arizona, July 10-13, 2005 [2] H.Leiter et al. “RIT-µX - High Precision Micro Ion Propulsion System Based on RF-Technology”, 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Cincinnati, OH, July 8-11, 2007, No. AIAA- 2007-5250 [3]Horst W. Loeb et al.: Development of a RIT-Millithruster, IAC-04-S.4.04 55th International Astronautical Congress, Vancouver, Canada, Oct. 4-8, 2004 [4] Hans J. Leiter et al.: RIT15S - A radio frequency ion engine for high specific impulse operation, AIAA-2001-3491, 37th Joint Propulsion Conference, Salt Lake City, UT, July 8-11, 2001 [5] M. Zeuner et al.: Ion Beam Characterisation of the RIT 10 Ion Thruster, AIAA-2003-5009, 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Huntsville, Alabama, July 20-23, 2003 [6] S. Weis et al.: An Imaging Spectroscopy System Based On Multi-Fiber Optic For Investigation Of Ion- And Plasma Thrusters, Proceedings Space Propulsion, 2.- 9.Juni 2004, Chia Laguna (Cagliari) Sardinien (Italien) [7] [H.J. Leiter et al.:Perfomance Inprovement of Radiofrequency Ion Thrusters - The Evolution of the RIT 15 Ion, Engine, 26th International Electric Propulsion Conference, Kokuro-kita, Kitkyushu, Japan, 17.-21. Oktober 1999, Paper No. IEPC-99-154 [8] H.J. Leiter et al.: RIT 15 S und RIT 15 LP - The Development of High Performance Mission Optimized Ion Thrusters, 35th Joint Propulsion Conference, Los Angeles, CA, 20.-24. Juni 1999, AIAA-Paper, No. 99-2444 [9] Horst Loeb et al.: Forty-years of Giessen EP-Activities and the recent µN-RIT, IEPC-2005-031 [10]Davar Feili et al.: Performance Mapping of new µN-RITs at Giessen, IPEC-2005-252 [11] H.Leiter et al. RIT-µX - The New Modular High Precision Micro Ion Propulsion System IEPC-2007-209 9 The 31st International Electric Propulsion Conference, University of Michigan, USA September 20 – 24, 2009
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Design Development and Test of the RIT-ÁX Mini Ion Engine System

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