Theoretical And Experimental Study Of Pulsed Plasma Thruster Operation Process

Electric propulsion devices have been used widely in space flight mission for its superior performance. Pulsed plasma thruster (PPT) is a kind of electromagnetic thruster, which has characters of high specific impulse, low power, simplicity, light weight and so on. It can be applied in station-keeping, attitude control and formation flying requirements of micro-satellites, which has become a highlight of electric propulsion research internationally currently. By means of theoretical analysis, experimental investigation and numerical simulation, working process of parallel-plate solid-propellant PPT was studied, factors affecting thrust performance were analyzed, the way to improving thrust performance was explored.PPT experimental system was established, which includes vacuum system, micro-thrust measure system and electric parameters measure system. Technique requirements, targets and characters of experimental system were analyzed in detail. Based on electromagnetism balance micro-thrust measurement device was developed, which resolved key technique problem in PPT research.Electromechanical model was used to predict PPT performance parameters. Influences of variations of electric parameters (capacitor capacitance, initial voltage, circuit resistance and electron temperature) and configuration parameters (electrodes distance, electrode width and electrode ratio of height to width) on thruster performance were studied by numerical simulation.A breech-fed parallel-plate PPT was designed and manufactured. Ignition experiments were performed under different working conditions. Performance parameters such as discharge voltage and current waveform, ablation mass per pulse and thrust per pulse were measured, and performance parameters such as impulse bit, specific impulse, thruster efficiency were calculated. Influence of variations of electric parameters and configuration parameters on thruster performance was analyzed. The experimental results showed, at the same discharge energy smaller capacitance and higher initial voltage can effectively improve thruster impulse bit, specific impulse and thrust efficiency, within reasonable range increasing electrode length can improve impulse bit, specific impulse and thrust efficiency, at the same discharge energy smaller propellant ablation area is of advantage to specific impulse and thrust efficiency, and to the same ablation area, increasing the ratio of height to width of propellant can improve impulse bit, specific impulse and thrust efficiency.On the assumption of local thermodynamic equilibrium and quasi-neutral plasma, 1 -D PPT working process unsteady mathematic model based on magnetohydrodynamic was established, which described physics mechanisms and couple effects of mechanisms in PPT, reflected the physics progress of convection, energy and momentum transportation, Lorentz force, ohmic heating and magnetic field diffusion, etc. The eigenvalues and eigenvectors of the ideal MHD equations were analyzed and deduced. MHD equations with ohmic heating source were solved by second order MacCormack scheme. Calculation results showed, ionized gases mostly come out at the pulsed time, exhaust velocity accelerated by Lorentz force is primary source of thrust, propellant ablation surface temperature is above Teflon decompose temperature in a pulse time after discharge for a long time, which lead to late ablation of propellant to reduce the use efficiency of propellant.