Research On Operational Mechanism Of An Inductive Pulsed Thruster

An Inductive pulsed thruster is a sort of in-space propulsion engine,which employs an electromagnetic field induced by a pulsed current to inductively ionize and accelerate gaseous propellant to generate thrust.This thesis performed a comprehensive research on the operational mechanism of inductive pulsed thrusters,combiningtheoretic analysis,numerical simulation and experimental methods.Research efforts mainly focused on the evolution of plasma structure,the bi-directional coupling between plasma and circuit,and the effects of varied operating conditions on the acceleration process of plasma.A two dimensional axisymmetric magnetohydrodynamic model coupled with exciting circuit and ful-domain magnetic field was developed to simulate the working process of inductive pulsed thrusters.The circuit process,magnetic field diffusion,plasma dynamic,and ionization process were solved in a ful y coupled manner using comerical COMSOL platform.The validation and verification of numerical simulationwere checked by comparisons with experimental data reported by literatures.The model successful y captured the time-dependent flow fieldand magnetic field feature of plasma,while the computed thruster performance also agreed well with experimentally measured results.Applying numerical simulation,thephysical process within each pulsed stoke was revealed in depth: the time-dependent plasma parameter distributions were described in detail,the bi-directional coupling effect between plasma and circuit was analyzedquantitatively,and the positive contribution of secondary current sheets to the ultimate thruster performance was also confirmed.Besides,the effects of operation parameters including discharge voltage and pulsed gas mass bit,the effects of initial gas distributions,and the effects of metal structures includingthe grounding plate and vacuum chamber wal s,were also discussed and analyzed.An experimental apparatus for the study of inductive pulsed thruster was developed,which consisted of a thrusterprinciple prototype,as well as the experiment supporting system and the measurement system.The principle prototype integrated a drive-coil,a drive-circuit and a pulsed gas injector.The supporting system included a control subsystem,a high-voltage source and a vacuum chamber.The measurement system involved a self-developed B-dot magnetic probe array,a high-speed camera,a photodetector,together with a current monitor and a high-voltage monitor.Unloaded discharge tests at atmosphere indicated that,with all characteristic indexes(the peak current,the current rise rate,the magnetic field intensity and uniformity,and the precision of control sub-system)being satisfied,the platform could be employed to the study the operational mechanism of inductive pulsed thrusters..Based on the experimental apparatus,the discharge process of ambient fill condition were studiedunder varied operation parameters.The temporal plasma structure,drivecircuit current,plasma radiation density,as well as the magnetic field distributionwere analyzedto study the initial ionization,plasma evolution,energy deposition and propellant accleration process.For pulsed gas injection condition,the optimum delay time between fast pulse gas valve opening and pulsed switch triggering was measured.After that,the discharge process under pulsed gas injection were studied,with special emphasis on the initial ionization,current sheet development and propellant mass use ratio.