A minimized electron cyclotron resonance ion thruster for China’s space-borne gravitational wave detection missions

Abstract

Space-borne gravitational wave (GW) detection spacecraft works in the state of drag free for which a disturbance reduction system is utilized to offset the non-conservative force. The key actuator of drag-free control loop is a micro-thruster with the performance of a high precision thrust and wide-range operations. Ion thruster, such as electron cyclotron resonance ion thruster (ECRIT), is one of the options because its thrust can be controlled precisely by the method of beam current feedback. However, there is still a barrier for the conventional ECRIT to achieve the low thrust of 1 µN as required in space-borne GWs detection missions due to its radial structure. In this work, a minimized ECR ion thruster (mini-ECRIT) is designed by a new idea that it employs an axial ring-cusped field to exploit the low-pressure adaptability of resonance heating. The mini-ECRIT is tested and results in a dynamic thrust range of 1‒100 µN, a resolution of 0.1 µN, a thrust noise of 0.1 µN/Hz1/2, and a response time of about 10 ms. In addition, the specific impulse of this thruster can reach as high as 510 s at low thrust 5 µN, being higher than that of previous ion thrusters by a factor of about 5, which may significantly increase the lifetime of the system. This minimized ECR ion thruster may support China’s space-borne gravitational wave detection missions such as TianQin.