Belief Reliability Modeling and Analysis for the Three-Grid Ion Thruster

The ion thruster is one of the most widely used electric propulsion thrusters, and its failure can directly affect the success of deep-space exploration missions. Therefore, the ion thruster is always required with extremely high reliability. However, few researchers thoroughly analyze the influence of internal and external parameters on reliability, which makes it difficult to provide guidance for reliability improvement. In this paper, based on reliability science principles, a reliability model considering performance degradation and multi-source uncertainties is established for three-grid ion thrusters. Firstly, the electron back streaming limit (EBL) is determined as the key performance parameter based on functional principles and the performance margin model is constructed. Then, the degradation model considering sputter erosion is established through simulation and response surface methodology (RSM). Furtherly, we analyze the sources of uncertainties and quantify uncertainties with probability distributions. Finally, the reliability model is established. A case study of a xenon ion thruster is conducted to perform reliability and sensitivity analysis. The results show that the proposed model can quantify reliability by given internal and external parameters and provide guidance for the designers to meet high reliability requirements.