離子推進器蓋為一電能式推進系統，將離子團以電磁場加速以產生推力。相比於化學式推進系統，電能推進以其高比衝值之優勢，廣泛運用於深太空推進之中。比衝值其定義為單位重量推進劑產生之衝量，或單位重量流量之推進劑所產生之推力，可簡單以「燃料效率」蓋括。電能推進中尤以「離子推進器」之比衝值為最大，因此吾人選定離子推進器做為本論文研究之主題。遍觀全球，離子推進器曾應用於諸多著名任務如美國太空總署於一九八八年發射之「深太空一號」、歐洲太空總署於二零一一年發射之「阿緹蜜絲號」與日本宇宙航空研究開發機構於二零一四年發射之「隼鳥二號」等等。

現今由於微小與輕量化之微衛星與立方衛星發展正盛，吾人設計微型離子推進器其直徑為八十毫米、長度為九十四毫米，恰可應用於輕量級衛星；且為彌補離子推進器之推力甚小之弱處，吾人採用「電子迴旋共振電漿」之機制，以期生成高密度之電漿團，據此產生高效率之指向性推力。本研究之電子迴旋共振電漿需以固定之微波頻率搭配相對應之背景磁場。運作中，離子經由金屬電網提供之平行電場進行加速：由最初之電漿產生區加速至前加速區，並且在主加速度區域中進一步成為高速離子。

其中，於前加速區域(離子萃取段)，為增進推進器效率並顧及燃料消耗率，應當大幅通過多數帶一定能量與初速之離子，並保留多數中性粒子（燃料）與較低能量和初速之離子，持續供給能量使其達到足夠能量再向後加速推出。因此，為了研究電磁場對所有加速區域的離子運動有何影響，以及了解離子之運動軌跡，吾人使用SIMION軟體進行粒子運動模擬。

吾人於模擬中得知，可以通過調整推進器之電網電位來提高離子透鏡效應，同時降低離子傾斜角所造成之壁面轟擊以增加離子通透率，並可以此確定最佳之前加速區長度應設計與離子透鏡焦距相同。同時經由SIMION之粒子運動模擬，吾人可據模擬之參數，設計出微型離子推進器。此外，螺線管線圈亦可提供壁面電壓以協助提高離子萃取效率。由於真空艙中具有非常少量之背景電漿，當吾人產生微量之電漿團做為電漿源後，「電子迴旋共振」將啟動鏈鎖反應，透過中性粒子和電子之間的碰撞效應增強電漿密度，此現象可概略為電子迴旋共振促成加速電子之迴旋運動以製造高密度離子源。概言之，吾人需一高密度離子源，再經電網之電位搭配加速推出離子，將可產生良好之推進效果。

本研究根據電磁場中離子行為之模擬結果，進行微型電子迴旋共振離子推進器之開發。目前該原型系統可生成近0.9毫牛頓之推力，其比衝量約為1025至3076秒，以上數值均以量測資料換算得之。本研究之推進器仰賴臺灣國立成功大學太空與電漿科學研究所之太空電漿實驗艙中進行測試。

Ion thruster is a form of electric propulsion by generating thrust from ion acceleration. Unlike chemical propulsions, electric propulsion, especially ion thruster, has the strength of higher specific impulse (ISP), which means higher propulsion efficiency. Accordingly, it can meet the requirement of deep space exploration mission. Ion thrusters have been used for many space missions, such as Deep Space 1 in 1998 from NASA, Artemis in 2001 from ESA, Hayabusa 2 in 2014 from JAXA etc. In the near future, small, lightweight, low power satellites with correspondingly low power thrusters, such as micro satellites or CubeSats, will be implemented for deep space explorations. We have designed a micro ion thruster with 80 mm in inner diameter and 94 mm in length for future CubeSat applications. Electron Cyclotron Resonance (ECR) Plasma is generated under 875 G background magnetic fields supplied by solenoid. The ions are initially accelerated from plasma generation region to the pre-acceleration region, and further accelerated to high speed in main acceleration region. Ions are accelerated by parallel electric fields supplied by metal grids. In the thruster, ion gyro-radius is 0.13 cm and its temperature is closed to room temperature.

To enhance thruster efficiency, ion transparency should be much higher than neutral particle (fuel) transparency in the pre-acceleration region. Ions should also be accelerated to higher initial speed before entering main acceleration region. To investigate the combination effects of electric and magnetic fields on ion motion in this region, single particle motion simulation is performed by SIMION software. Ion lensing effect, which reduces ion pitch angle effect and increases ion transparency, can be raised by increasing thruster boundary potential. Then the optimum pre-acceleration length can be determined to be the same as ion lensing focal length. Furthermore, the solenoid also provide a wall voltage to help increasing ion extraction efficiency. Since we have few plasma inside the chamber, cyclotron motion will initiate the chain reaction to enhance plasma density by collision effects between neutral particles and electrons. Thus, electron cyclotron resonance will do the job to accelerate electrons in order to make a high density ion source.

According to the simulation results of ion behaviors and ion optics, the development of the micro ECR Ion thruster is undertaken. Currently, this is just a prototype system which the thrust is nearly 0.9 milli-newtons and specific impulse is around 1025~3076s with the calculation of diagnostics. The thruster is tested by using Space Plasma Operation Chamber at National Cheng Kung University, Tainan, Taiwan.

[1] A. Mehrparvar, CubeSat Design Specification (CDS) REV 13, California Polytechnic State University, The CubeSat Program, Cal Poly SLO, 2014.
[2] I.S.S. Laboratory, XI-IV CubeSat, University of Tokyo, Tokyo, 2003.
[3] N.S. Organization, YamSat Program, National Space Organization, HsinChu, 2002.
[4] S.L. Vinjam, Theory of Propulsion: Electric Propulsion, India, 2014.
[5] R.R. John, S. Bennett, C. John F, Arcjet Engine Performance: Experiment and Theory, AIAA Journal, 1 (1963).
[6] W.A. Hoskins, R.J. Cassady, O. Morgan, R.M. Myers, F. Wilson, D.Q. King, K. deGrys, 30 Years of Electric Propulsion Flight Experience at Aerojet Rocketdyne, 33rd International Electric Propulsion ConferenceWashington, D.C., 2013, pp. 3.
[7] H.-Y. Lee, Indigenous Tchnology Development of a Prototype Arcjet System, Department of Aeronautics and Astronautics, National Cheng Kung University, Taiwan, 2010.
[8] H.-Y. Li, Development of a Novel Microwave-Plasma Stabilization Mechanism for Flame Stabilization and Electric Propulsion, Department of Aeronautics and Astronautics, National Cheng Kung University, Taiwan, 2013.
[9] O. Räisänen, Gridded ion thruster, Wikipedia, 2012.
[10] M. Patterson, NASA - Ion Propulsion, 2011
[11] R.G. Jahn, Physics of Electric Propulsion, Dover Publications, New York, 2006.
[12] D. Staack, F. McWalter, Hall thruster, Wikipedia, 2007.
[13] R.J. Cybulski, D.M. Shellhammer, R.R. Lovell, E.J. Domino, J.T. Kotnik, RESULTS FROM SERT I ION ROCKET FLIGHT TEST, NASA, U.S.A., 1965.
[14] R. Scrivens, Definition of Ion Sources, CERN Acceleration School, 2012.
[15] E.F. Gibbons, D.B. Miller, Experiments with an electron cyclotron resonance plasma accelerator, AIAA Journal, 2 (1964) 35-41.
[16] G.W. Bethke, D.B. Miller, Cyclotron resonance thruster design techniques, AIAA Journal, 4 (1966) 835-840.
[17] H. Kuninaka, S. Satori, Development and Demonstration of a Cathodeless Electron Cyclotron Resonance Ion Thruster, Journal of Propulsion and Power, 14 (1998) 1022-1026.
[18] I. Funaki, H. Kuninaka, K. Toki, Y. Shimizu, K. Nishiyama, Y. Horiuchi, Verification Tests of Carbon-Carbon Composite Grids for Microwave Discharge Ion Thruster, Journal of Propulsion and Power, 18 (2002) 169-175.
[19] J.E. Foster, M.J. Patterson, Microwave ECR Ion Thruster Development Activities at NASA Glenn Research Center, in: NASA (Ed.)U.S.A., 2002.
[20] J.E. Foster, M.J. Patterson, Discharge Characterization of 40 cm-Microwave ECR Ion Source and Neutralizer, NASA, U.S.A., 2003.
[21] J.E. Foster, T. Haag, M. Patterson, J. George J. Williams, J.S. Sovey, C. Carpenter, H. Kamhawi, S. Malone, F. Elliot, The High Power Electric Propulsion (HiPEP) Ion Thruster, NASA, U.S.A., 2004.
[22] J.E. Foster, H. Kamhawi, T. Haag, C. Carpenter, G.W. Williams, High Power ECR Ion Thruster Discharge Characterization, NASA, U.S.A., 2006.
[23] N. Yamamoto, H. Masui, H. Kataharada, H. Nakashima, Y. Takao, Antenna Configuration Effects on Thrust Performance of Miniature Microwave Discharge Ion Engine, Journal of Propulsion and Power, 22 (2006) 925-928.
[24] Y. Nakayama, I. Funaki, H. Kuninaka, Sub-Milli-Newton Class Miniature Microwave Ion Thruster, Journal of Propulsion and Power, 23 (2007) 495-499.
[25] K. Nishiyama, Y. Toyoda, S. Hosoda, Y. Shimizu, H. Kuninaka, An Ion Machined Accelerator Grid for a 20cm ECR Ion Thruster, J. Plasma Fusion Res. Series, 8 (2009).
[26] H. Koizumi, H. Kuninaka, Miniature Microwave Discharge Ion Thruster Driven by 1 Watt Microwave Power, Journal of Propulsion and Power, 26 (2010) 601-604.
[27] D.M. Goebel, I. Katz, Fundamentals of Electric Propulsion: Ion and Hall Thrusters, John Wiley & Sons, Inc., U.S.A., 2008.
[28] A. Sengupta, J. Brophy, J. Anderson, C. Garner, B. Banks, K. Groh, An Overview of the Results from the 30,000 Hr Life Test of Deep Space 1 Flight Spare Ion Engine, 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, AIAA, Florida, 2004.
[29] R.I. Marques, S.B. Gabriel, Dual Stage Four Grid (DS4G) Ion Engine for Very High Velocity Change Missions, 31st International Electric Propulsion ConferenceAnn Arbor, Michigan, U.S.A., 2009.
[30] S. Anbang, M. Genwang, U. Juan, X. Guangqing, C. Maolin, H. Chao, Particle Simulation of Three-Grid ECR Ion Thruster Optics and Erosion Prediction, Plasma Science and technology, 12 (2010).
[31] L.T. Williams, M.L.R. Walker, Initial Performance Evaluation of a Gridded Radio Frequency Ion Thruster, Journal of Propulsion and Power, 30 (2014) 645-655.
[32] J.E. Polk, R.Y. Kakuda, J.R. Anderson, J.R. Brophy, V.K. Rawlin, J. Sovey, J. Hamley, In-flight performance of the NSTAR ion propulsion system on the Deep Space One mission. Aerospace Conference Proceedings, Aerospace Conference Proceedings, 2000 IEEE, 2000.
[33] M.D. Rayman, T.C. Fraschetti, C.A. Raymond, C.T. Russell, Dawn: A mission in development for exploration of main belt asteroids Vesta and Ceres, Acta Astronautica, 58 (2006) 605-616.
[34] M.T. Domonkos, M.J. Patterson, J.E. Foster, V.K. Rawlin, G.C. Soulas, J.S. Sovey, S.D. Kovaleski, R.F. Roman, G.J. Williams, Extending ion engine technology to NEXT and beyond, IEEE Conference Record - Abstracts. 2002 IEEE International Conference on Plasma Science (Cat. No.02CH37340), 2002, pp. 173.
[35] J.S. Sovey, V.K. Rawlin, M.J. Patterson, Ion Propulsion Development Projects in U.S.: Space Electric Rocket Test I to Deep Space 1, Journal of Propulsion and Power, 17 (2001) 517-526.
[36] A.S. Launchers, ELECTRIC PROPULSION THRUSTER FAMILY, Airbus Safran Launchers, Germany.
[37] JAXA, イオンエンジン Ion Engine, JAXA, 2016.
[38] Obsuser, First Ionization Energy, 2016.
[39] Dave, Circular polarization, Wikipedia, 2016.
[40] S.H. Chen, G. Le, M.C. Fok, Magnetospheric boundary perturbations on MHD and kinetic scales, Journal of Geophysical Research: Space Physics, 120 (2015) 113-137.
[41] R. Geller, Electron cyclotron resonance ion sources and ECR plasmas, IOP Publishing Ltd, London, 1996.
[42] D.M. Pozar, Microwave Engineering, John Wiley & Sons, Inc., U.S.A, 2011.
[43] D. Dahl, T. Appelhans, Advanced SIMION Ion Optics, The Idaho National Engineering and Environmental Laboratory, U.S.A., 2000.
[44] I.S. Scientific Instrument Services, SIMION®, 2017.
[45] I.H. Hutchinson, Principles of Plasma Diagnostics, Cambridge University Press, Cambridge, 2002.
[46] Pace, Example of Langmuir Probe Analysis, 2015.
[47] H.-K. Fang, Ion measurements of Ionosphere Plasma in Space Plasma operation Chamber, Institute of physics, National Cheng Kung University, Taiwan, 2015.