关键词: 离子推力器;在轨环境;工作点;热控措施;栅极间距;启动

Abstract: The grid gap variation is an important factor influencing the normal start-up in orbit of ion thruster under cold condition， and determines the time to start-up and thermal control strategies. Based on finite-element method and ground thermal balance test， an analytical model of the 30cm ion thruster is built and has been demonstrated by test results. The grid temperature distribution and gap variation effected by solar illumination are firstly simulated. After that， when the ion thruster is working in 5kW power and starts up from different initial temperature， the gap variations are considered. Finally， when the thruster starts up from the worst situation， the influence of thermal control on gap variation is calculated. The results show that if solar illumination is only considered， the temperature of grid gap varies periodically and the highest temperature is 100℃ higher than the lowest one and the grid gap deduction varies in the range of 0.06~0.16mm. When 60W active thermal control is applied， the maximum temperature difference decreases to 60℃ and the range of grid gap deduction changes to 0~0.03mm. From the highest temperature point， the ion thruster start-up is most likely to be successful whereas from the lowest temperature point， it is the hardest. In these two situations， the minimum grid gap between the screen grid and the accelerator grid is 0.22 and 0.04mm， respectively. When ion thruster starts up from the lowest temperature point and the thermal control power is 10， 70 and 120W， the minimum grid gap between the screen grid and the accelerator grid is 0.06， 0.20 and 0.29mm， respectively. Active thermal control can effectively reduce the maximum thermal deformation displacement of the grids and 120W heat power （then corresponding target temperature is 50℃） can guarantee a safe grid gap for the 30cm ion thruster starting up from the worst situation.

Key words: Ion thruster;In orbit;Working point;Thermal control;Grid gap;Starting up