Study On The Techniques Of High Precision Micro-impulse Measurement Of Pulsed Plasma Thruster

Techniques of high precision micro-impulse measurement of the ablative pulse plasma thruster(APPT) with parallel plate electrodes were systematically studied in both theoretical and experimental methodes in this research.The system error of the C-section torsional pendulum was analyzed in this study, and then the mathematical model of micro-impulse measurement and error propagation formula were established. A mathematical model of optical pry was established and effects of optidal pry configuration on measurement results of C-section torsional pendulum was analyzed by the mathematical model. The result shows that whether the two opposite mirrors is parallel exactly has no effect on the degree of linearity between impulse bits and PSD signal, but it effects the magnitude of system error of measurement results and the position deviation of the reflector has little effect on measurement results.Considering the electromagnetic environment of C-section torsional pendulum and the actual condition, electromagnetic compatibility(EMC) methods, including wire screen and signal filter, have been adopted to damp electromagnetic interference(EMI) in measurement signal. The result shows that the main source of EMI is electromagnetic radiation from the vacuum devices in measurement process, white noise in signal is damped efficiently and signal to noise ratio is enhanced greatly by using EMC methods.The impulse produced by PPT was measured utilizing the C-section torsional pendulum, and the error was analyzed. The result shows that the measure error of impulse is mainly caused by the errors of calibration, the signal peak and the arm of the impulses and the dominant error is caused by signal noise; based on the APPTs with discharge energy at 20 J and 11.25 J, the impulse bits are 422.415?Ns and 244.266?Ns respectively, and the relative measurement errors are 1.28% and 2.05% respectively; in order to improve the measurement precision, the measurement signal of small impulse bitl must be filtered by software after using a filter in electric circuit; the response of torsional pendulum to the same impulse is repeatable.In this paper, the research on techniques of high precision micro-impulse measurement of the APPT provides favorable guidance for the micro-impulse measurement study.