The Research Of Pulsed Plasma Characteristics For Small Satellite Propulsion Applications

The optimization of small satellite thrusters is an important part of the development of small satellites.At present,the research of small satellite thrusters mainly focuses on simplifying the structure of thrusters,reducing the volume and mass,and increasing the specific impulse and efficiency of propulsion.However,different types of thrusters use different working propellant and they have completely different thrust formation mechanisms.Based on the simple structure of electromagnetic thruster,the vacuum arc thruster(VAT)and pulsed plasma thruster(PPT)with solid propellant are studied in this paper,and the simulation and experiment are carried out to verify each research point.Both VATs and PPTs operate in a pulse discharge mode with single discharge discharge time in ?s range and current amplitude above 100 A.In this paper,a plasma research platform based on vacuum pulse discharge is built and the corresponding system simulation model is established.The transient process of the pulse discharge system and the dynamic process of electrode breakdown based on the electrode equivalent circuit are analyzed.The influence of circuit parameters on the dynamic response characteristics of the electrode during discharge is analyzed.It is proved that the optimization of the circuit parameters can effectively increase the discharge power of the electrode and improve the energy utilization of the system.The thrust of the VATs originates from the directional propagation characteristics of the metal plasma.In this paper,the influence of the basic parameters of the coaxial electrode geometry on plasma generation is studied.Cathode structure parameters for improving electrode discharge stability and metal plasma propagation are analyzed from the aspect of the cone tip angle and the cathode material.Through the study of the electrode distance,the inner diameter of the insulating cylinder,the shape of the nozzle and the anode "self-magnetic field",the method of increasing the peak value of the Hump potential and increasing the axial propagation density of the plasma by the ?-pinch is obtained.Aiming at the problems of some low melting point and oxidizable metal triggering failures and maintenance difficulties in space existing in "triggerless" arc initiation,a "self-triggered" low-voltage triggering method based on carbon fiber is proposed.Reliable vacuum arc triggering down to several hundred volts is achieved,which provides an alternative choice for the triggering of VAT.Aiming at the problem of low efficiency caused by radial divergence of plasma jet in VAT,a discharge method of long gap vacuum breakdown based on multi-anode electrode geometry is proposed.The discharge characteristics of the multi-anode electrode geometry are analyzed,and and the Z pinch characteristics of plasma density distribution in the axial direction are studied by changing the current flow path in the process of electrical discharge.The PPTs mainly use a large current formed by surface flashover to ablate the propellant to generate plasma and produce thrust.In this paper,the basic electrode geometry of the coaxial PPT is analyzed,and the influence of the axial ablation distance of propellant,the inner diameter of the propellant tube and the surface parameters of the propellant on the discharge characteristics and plasma generation characteristics of the electrode are obtained.The conventional PPTs mainly use the spark plug triggering method.In this paper,the method of reducing the trigger voltage of the surface flashover is studied in the case of simplifying the thruster strucutre and eliminating the spark plug A triggering method for increasing the electric field intensity of the cathode triplejunction(CTJ)and optimizing the electric field vector distribution of the electrodes by using the potential-suspended induction electrode is proposed.Aiming at the problem of low propulsion efficiency caused by plasma plume divergence of conventional electrode PPT,a non-contact surface discharge method using multi-anode electrode geometry is studied Based on the Z-pinch characteristics of multi-anode electrode geometry,the spatial density distribution of ablative plasma is studied.On the basis of multi-anode electrode geometry,a plasma plume optimization method of cathode "self-magnetic field" is proposed,which proves the effectiveness of further optimizing the plasma density distributionIn order to verify the research points of this paper,a micro-thrust test platform is built.The single-pulse thrust characteristics of the two thrusters are measured by the impulse pendulum micro-thrust measurement system and the PVDF piezoelectric film micro-thrust measurement system.The propulsion parameters of the VAT and the PPT before and after the electrode optimization are compared and analyzed,and the effectiveness of impoving the small satellite propulsion charcteristics by optimizing the plasma plume is verified.