微阴极电弧推力器平板电极放电特性实验研究

Experimental Study on Discharge Characteristics of Plate Electrode in Micro-Cathode Arc Thruster

关键词:  微阴极电弧推力器  放电特性  时空演变  平板型电极  电弧特性  导电涂层

Key words:  Micro-cathode arc thruster  Discharge characteristics  Temporal and spatial evolution  Plate electrode  Arc characteristics  Conductive coating

摘要:

微阴极电弧推力器（μCAT）具有比冲高、元冲量小、结构简单等优点，在微纳卫星任务中具有广阔的应用前景。在实际应用中随着推力器点火次数的增加，导电涂层退化不断加剧，导致推力器的性能降低甚至失效，成为制约推力器应用进一步拓展的关键因素。本文采用平板电极结构开展微阴极电弧推力器放电特性及失效机理实验研究，结果表明：在全寿命周期内，电极之间放电形成的电弧分布的演化可以分为四个阶段：集聚型、扩散型、分散型和近失效型放电阶段，主导放电特性变化的主要因素是阴极的烧蚀和涂层的退化。在推力器接近失效时，弧电压大幅升高，弧电流明显降低，单次放电时间进一步缩短，电极间电阻出现陡增，抑制了微阴极电弧的产生和发展。在本文实验工况下点火次数达到69万次，推力器失效，此时阴阳极之间的电阻陡增为153kΩ。对真空条件下电极之间放电特性的时空演变进行分析，有助于明晰推力器失效机理，为提升推力器的寿命和性能提供依据。

Abstract:

Micro-cathode arc thruster （μCAT） has the advantages of high specific impulse，small impulse bit and simple structure， and has broad application prospects in micro-nano satellite missions. In practical application， with the increase of ignition times of thruster， the degradation of the conductive coating continues to intensify. This leads to the performance degradation or even failure of thruster， which becomes a key factor limiting the further development of thruster application. In this paper， the experimental study on the discharge characteristics and failure mechanism of micro-cathode arc thruster was carried out with a plate electrode structure. The results show that the evolution of the arc distribution formed by the discharge between electrodes can be divided into four stages in the whole life cycle： concentrated， diffused， dispersed and near failure discharge stages. The main factors that dominate the change of discharge characteristics are cathode ablation and coating degradation. When the thruster is close to failure， the arc voltage increases significantly， the arc current decreases significantly， the discharge time is further shortened， and the resistance between electrodes increases sharply， which inhibits the generation and development of micro-cathode arc. Under the experimental conditions of this paper， when the ignition times reached 6.9×10⁵， the thruster failed. At this time， the resistance between the anode and cathode increased sharply to 153kΩ. The analysis of the temporal and spatial evolution of the discharge characteristics under vacuum conditions will help to clarify the failure mechanism of the thruster and provide a basis for improving the life and performance of the thruster.