【作者】 李自然；

【导师】 周进；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2008， 博士

【摘要】 在各种电推进系统中,脉冲等离子体推力器(Pulsed Plasma Thrusters,PPTs)作为一种极有价值的新型空间电磁推力器,具有应用功率范围宽、平均功率小、结构简单、控制方便、响应快速、比冲高、推力小、容易集成等特点,能够广泛应用于微小卫星的姿轨控推进系统,是目前国际上电推进研究的热点之一。本文主要通过理论分析和地面实验研究,对PPT的设计和性能等进行了系统的研究,提出和论证了PPT在微小卫星上的应用方法,探寻了PPT实验样机的设计、性能测量和提升的途经,采用多种实验手段对PPT工作过程和工作机理进行了深入地研究。系统分析和论证了PPT执行微小卫星多种姿轨控推进任务的可行性。研究表明,PPT对于微小卫星的摄动力补偿、东西位置保持、星座相位调整和姿态控制等推进任务具有良好的适用性,且对于不同的推进任务,存在一个与卫星结构参数和PPT推进性能有关的理想速度增量和理想比冲范围。研制了一种采用Teflon固体推进剂尾部馈送式的平行板PPT。分析对比了不同储能单元和点火启动设备的应用特性,改进了放电电极、传输导线、推进剂供应装置以及其他结构件,论证了PPT电源系统的选型和设计方案。所设计的PPT,能够满足地面实验研究的需要,主要性能指标与国外同类PPT相当。设计了PPT放电电流测量系统,通过对放电电流和放电电压等参数的测量,研究了PPT的放电特性,为采用理论和经验公式对PPT推进性能进行计算奠定了基础。改进了钟摆式天平微推力测量方法,结合微量天平对PPT推进剂平均脉冲烧蚀质量的测量,获得了元冲量、比冲和工作效率等PPT推进性能参数,且测量结果与经验公式计算结果较为一致。此外,还提出了一种基于电容器退化失效模型的PPT能量存储单元性能可靠性分析模型,并采用该模型对本文设计的PPT进行了寿命预估。在对PPT点火、能量存储单元充电和放电,以及工作过程中,放电通道内电磁场的变化等进行研究时发现:点火启动影响到PPT的工作可靠性;充电和放电回路中,电阻、电感和电容量等电参数,关系着PPT能量的传递和损耗;放电通道及其邻近区域的电磁场分布及其变化情况,则直接决定了PPT等离子体的形成、加速和推力的产生。此外,通过对PPT工作时,各组成部件表面温度的测量和分析,从热损耗的角度分析了PPT效率低下的原因,探究了PPT的热量损失机理,进一步分析和计算了PPT的能量分配和效率组成。通过对PPT工作过程进行高速摄影,观测了放电通道内等离子体的产生、加速和扩散过程;采用质谱分析的方法,对PPT的羽流成分进行了研究,从分子组成的角度分析了PPT推进剂烧蚀电离、溅射腐蚀和积碳污染的机理;对PPT工作过程中产生的电磁干扰进行了时域和频域的诊断和分析,提出了相应的电磁兼容措施。更多还原

【Abstract】 In various kinds of electric propulsion system, Pulsed plasma thruster (PPT) is a new and valuable type of space electromagnetic thruster, which has the characteristics of wide application range, low average electric power, simple structure, convenient control, fast respond, high specific impulse, small thrust, easy integration and so on. It can be widely applied in attitude or orbit control propulsion system of micro-satellites, and is the highlight of electric propulsion research in the world currently.In the present paper, by means of theoretical analysis and ground experimental investigation, the design and performance of PPT research have been systematically carried out. The method of PPT applied in micro-satellites was presented and discussed. The ways of PPT prototype design, performance measurement and improving, were explored. The operation process and mechanisms were studied thoroughly by several experimental means.The feasibility of PPT performing manifold micro-satellites attitude or orbit control propulsion missions was analysed and testified systematically. The research results show that PPT is very suitable for micro-satellites perturbation compensation, east west station keeping, constellation phase adjusting, attitude control and so forth. For different propulsion missions, there exist an ideal velocity increment and a fine specific impulse range which are related to structure parameters of satellites and propulsion performance of PPT.A breech-fed parallel-plate PPT which uses solid Teflon as propellant was designed and manufactured. The application features of different energy storage units and discharge initiation devices were contrasted and analysed. The electrodes, transmission lines, propellant feed assembly and other accessories were ameliorated. The type and design project of power processing unit were demonstrated. The PPT can meet the demands of PPT ground experiment research, and its main performance parameters are similar to those of the overseas PPTs of the same type.The PPT discharge current measure system was designed, and through the measurement of the discharge current and voltage, the discharge identities of PPT were studied, the foundation of using theoretical and experiential formulas to calculate the PPT propulsion performance parameters was established. The method of using pendulum balance to measure PPT micro thrust was improved, and taking into consideration the metage of propellant average pulse ablation mass by using microbalance, some propulsion performace parameters of PPT, such as the impulse bit, specific impulse and thrust efficiency were obtained, and it is found that the measurements were in agreement with the results calculated from the experience formulas. Besides, a model based on capacitors degradation failure used for analyzing the PPT energy storage unit reliability was presented, and this model was applied to the estimation of the PPT life.According to the research of PPT ignition, charge and discharge of energe storage unit, the change of electric field and the magnetic field in PPT discharge region during the PPT working process, some conclusions were drawn. PPT operation reliability is influenced by ignition process. The circuit parameters such as resistance, inductance and capacitance in charge circuit and discharge circuit influence the energy transfer and consumption. The distribution and change of electric field and the magnetic field in PPT discharge region and the vicinity, directly determines the formation and acceleration of PPT plasma and the generation of the thrust. Furthermore, through measuring and analyzing the surface temperature of PPT components during PPT working process, the reason of PPT low efficiency was explained from the perspective of heat consumption, the mechanism of PPT heat loss was explored, and the energy distribution and the efficiency composition were further analysed and calculated.By means of high speed photograph during PPT working process, the process of plasma forming, accelerating and diffusing in PPT discharge region was observed. By means of mass spectrum analysis, the components of PPT plume were studied, and the mechanisms of propellant ablation, ionization, sputtering erosion and deposition contamination were analysed from the perspective of the molecule buildup. Using the time domain and the frequency domain analysis and diagnosis techniques, the electromagnetic interference produced by PPT works was studied, and the ways of electromagnetic compatibility were put forward.更多还原