LaB_(6)空心阴极发射体失效的工作寿命预测及可靠性定量评估

Lifetime Prediction and Reliability Quantitative Evaluation of LaB_(6) Hollow Cathode under Cathode Insert Depletion Failure Mode

随着电推进技术在空间任务中的广泛应用,推力器的寿命预测及可靠性评估显得尤为重要。空心阴极的寿命是制约电推力器寿命和可靠性的关键因素之一,其主要失效模式包括发射体失效、触持极结构失效等。针对LaB_(6)空心阴极发射体失效这一模式,建立了空心阴极工作在额定发射电流下的发射体损耗过程及工作寿命预测模型,通过发射体损耗预测形态与试验结果对比证实了所建模型的合理性。在此基础上,通过对寿命预测模型中各输入参数在其各自不确定度范围内的随机抽样组合,模拟多个空心阴极独立工作情况,获得这些空心阴极对应发射体失效模式的工作寿命数据,利用威布尔统计规律及分析方法给出了空心阴极的可靠性定量评估结果,并分析讨论了模型敏感参数对寿命的影响。

With the wide application of electric propulsion technology in space missions,the life prediction and reliability evaluation of thrusters are particularly important.One of the key factors restricting the service life and reliability of electric thrusters is the service life of the hollow cathode,whose main failure modes are cathode insert depletion,structural failure of keeper,etc.Based on the insert depletion failure mode,an insert consumption model and lifetime prediction method under rated emission current are established.Comparing the consumption computed from the model with that from experiment,the rationality of the model is confirmed.Furthermore,hollow cathodes lifetime data under the insert depletion failure mode is attained by random sampling of the input parameters of the model within their respective uncertainty range in order to simulate several hollow cathodes working independently.Weibull distribution method is used to give the quantitative evaluation of hollow cathode reliability,and the influence of model sensitive parameters on the cathode’s lifetime is analyzed and discussed.