Experimental Study On Ignition And Maintenance Characteristics Of Radio Frequency Ion Thruster

The increasing space activities of human beings intensify the demand for space propulsion technology,and electric propulsion has gradually attracted the attention and focus of the space community due to its advantages of high specific impulse,long life,and compact structure.To meet the needs of space missions such as Darwin,Inversion of earth gravity field,Gravitational wave detection,etc.Research institutes in various countries have strengthened the research on micro cattle electric propulsion.The RF ion thruster has become a good choice for micro-cow-scale propulsion because of its good scaling characteristics and simple structure.Since the micro RF ion thruster has the problem of ignition difficulty,this paper carries out an experimental study on its ignition characteristics based on the design of a 4cm diameter thruster and does a comprehensive test on the performance of the thruster,as follows:First,the overall parameter design of the thruster is completed with reference to domestic and international research experience,and on the basis of this paper,the experimental grid positioning and insulation problems encountered in the experiments are specifically optimized and improved.Secondly,according to the common impedance matching and power feed-in problems in RF discharge,the experimental matching network design principle and power feed-in techniques are introduced,and the four ignition schemes are experimentally verified and analyzed for ignition characteristics.The results show that although high-flow impact ignition has high ignition reliability,the matching state before and after ignition will change significantly,and lowering the frequency will improve the flow conditions required for ignition;for the gas-holding ignition method,the pressure pulse required for ignition is relatively high at low forward power,and the reflected power ratio is smaller and the thruster state is more stable after ignition at low flow rate and forward power of 30 W.Although the inter-gate DC voltage ignition can reduce the range of flow adjustment during ignition,the ignition method has a certain randomness of ignition;the gas-holding grid DC voltage ignition scheme effectively reduces the gird voltage required for ignition and the gas-holding time,and the ignition occurs instantaneously,which can achieve high reliability ignition under certain ignition conditions and is a more satisfactory ignition method at present.Finally,the performance parameters of the thruster are tested and the results show that increasing the power,flow rate and acceleration voltage within a certain range can increase the ion draw and thrust of the thruster,and that the thrust and specific impulse vary linearly with the screen grids voltage under certain operating conditions.When the thruster is operated under high operating conditions,the matching characteristics do not change significantly with the increase of the gate voltage,while after reducing the flow rate and power,the ion extraction will have a significant impact on the discharge of the thruster,and even lead to the thruster stalling.