| Due to the low cost of designing,testing and launching microsatellites,which can be launched by hundreds or thousands at a time.In addition,microsatellites,mainly working in the mode of team network,can complete many complex space tasks with higher efficiency than the traditional working mode of a single large satellite.It makes microsatellites gradually occupy a dominant position in the satellite field.CubeSat,a particular type of micro-satellite with a total weight less than 1.33 kg,is a modular 10 cm cubic satellite.CubeSat has attracted research attention at home and abroad.Micro propulsion systems are needed to assist Cubesats with orbital propulsion and attitude control,but are currently limited.So,the research work on micro thrusters suitable for CubeSats is in urgent need.Based on the working principle of the radio-frequency(RF)electrothermal inductively coupled plasma micro thruster in this thesis.Firstly,the HELIC program is used to calculate the RF power deposition under different antenna configurations.The results show that the dual-antenna scheme of Loop++is superior to the single-antenna scheme of the loop type.Then an experimental device for the study of discharge characteristics of single tube RF plasma is designed and developed,which includes vacuum system,gas source system,discharge system and diagnosis system.In the argon discharge experiment,the plasma density,electron temperature and ion energy distribution function were measured by RF compensated Langmuir probe and retarding potential analyzer.The plasma parameters and antenna-plasma power coupling efficiency of the two antenna schemes are compared under the same experimental conditions.The initial probe diagnosis results show that the ionization degree of dualantenna scheme is higher than that of single-antenna case,the plasma density is about 1018 m-3 at 100 W of power,and electron temperature is higher.There are ions accelerated to supersonic speed by the potential drop along the plume in dual-antenna scheme.According to the study on the power coupling efficiency of the two schemes and the characteristics and mechanism of the dual-antenna ion acceleration shows that the antenna-plasma power coupling efficiency of the dual antenna scheme is 2.6 times that of the single-antenna scheme.In addition,the thrust measurement method is used to evaluate the thrust performance of the dual-antenna scheme.A little 1 sccm nitrogen was added into 100 sccm argon for discharge,and the temperature of the neutral gas was directly measured by the optical emission spectrum(OES)matching the rotating vibration band of the first negative band system of nitrogen ion(N2+).A typical result shows that the temperature of the heated neutral gas is about 1700 K at 100 W power.At this time,the thrust formed by the neutral gas is 1.98 mN.Due to the dual-antenna case producing the ion beam,the ion thrust calculation model was established to evaluate the thrust generated by the ion beam.The ion beam energy is measured by the retarding potential analyzer and ion beam density is calculated by plasma density.The density and energy of ion beam were substituted into the calculation model,and the ion beam thrust is 0.249 mN at 100 W power and 100 sccm flow rate of argon.According to the evaluation and calculation,the typical total thrust,specific impulse and thruster efficiency of the dual-antenna micro-plasma thruster are 2.23 mN,76 s and 0.8%,respectively,at 100 sccm flow rate of argon and 100 W power.Compared with the cold gas thrust of 0.83mN,the total thrust increased by 168%,and the ion thrust accounted for 11%of the total thrust.Finally,a 3×3 array scheme is designed and a vector propulsion control model is established theoretically in this thesis.The interaction between multiple plasma plumes is preliminarily studied.The results show that the array discharge will generate influences on the magnitude and direction of thrust. |
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