分块阳极式激光支持的脉冲等离子体推力器实验研究

Experimental Study of Laser Assisted Pulsed Plasma Thruster with Segmented Anode

关键词:  脉冲等离子体推力器  分块阳极  高速摄影技术  滞后烧蚀  羽流分裂  微推进技术

Key words:  Pulse plasma thruster  Segmented anode  High-speed photography technology  Late-time ablation  Plume splitting  Micropropulsion technology

摘要:

通过纳秒激光烧蚀羽流特性的研究证实了羽流分裂现象的存在，为了抑制羽流分裂现象可能带来的滞后烧蚀而将分块阳极构型引入激光支持的脉冲等离子体推力器中，由此首次提出了分块阳极式激光支持的脉冲等离子体推力器的概念。通过实验对比研究了分块阳极和正常阳极构型的放电特性参数、性能参数和放电电弧发展演化等特性。结果表明，分块阳极构型能获得比正常阳极构型更高的峰值电流，特别是主放电之后的峰值电流，这可以提高对因速度较慢而进入放电通道较晚的工质的电离和加速效果，从而起到抑制滞后烧蚀的目的。分块阳极构型的电流平方积分值高于正常阳极构型，这表明分块阳极构型相比于正常阳极构型能获得更好的推进性能。通过分块阳极构型第二段放电电流特性可知，分块阳极构型推力器对等离子体加速的电磁力主要来源于分块阳极的第一段。分块阳极构型能降低放电回路的总电阻，但分块阳极构型相比于正常阳极构型会增加一定的放电延迟时间。同时，通过阴阳极板之间的放电电弧发展演化过程得到了分块阳极构型提高推力器推进性能的原因，即：通过限制阳极附弧点向阳极末端运动的速度来提高极板间的电流密度，进而提高推力器的性能。

Abstract:

The existence of plume splitting was proved through the study of nanosecond laser ablation plume characteristics. In order to suppress the late-time ablation that the plume splitting may bring， the segmented anode configuration was introduced into the laser-assisted pulse plasma thruster （LAPPT） and the concept of LAPPT with a segmented anode was proposed for the first time. The discharge characteristic parameters， performance parameters as well as the evolution of discharge arc of the segmented anode and normal anode configurations are studied by experiments. The results show that the segmented anode configuration can obtain a higher peak current than the normal anode configuration， especially for the peak current after the main discharge， which can improve the ionization and acceleration of the propellant entering the discharge channel late because of the slow speed， so as to achieve the purpose of suppressing the late-time ablation. The current square integral value of segmented anode configuration is higher than that of normal anode configuration， which indicates that segmented anode configuration can obtain better propulsion performance than normal anode configuration. According to the discharge current characteristics of the second stage of the segmented anode configuration， the electromagnetic force to accelerate plasma is mainly provided in the first stage of the segmented anode. The segmented anode configuration can reduce the total resistance of the discharge circuit， but this configuration will increase the discharge delay time compared with the normal anode configuration. At the same time， by analyzing the development and evolution of the discharge arc between the anode and cathode plates， the reasons for the segmented anode configuration to improve the propulsion performance of the thruster are obtained： by limiting the speed of the anode arc point moving to the end of anode， the current density between the plates is improved， thereby improving the performance of the thruster.