Design And Experiment Of A New Z-Pinch Pulsed Plasma Thruster

Since the 1980 s,the development of microsatellites in the world has been very rapid.Pulsed plasma thruster(PPT)has the advantages of simple structure,high specific impulse,low cost and easy control of thrust,so it has received more and more attention in the research field of microsatellites.However,the conventional ablative pulsed plasma thruster must be able to achieve ignition by means of a spark plug,which limits the miniaturization and weight reduction of the thruster.The ignition voltage is as high as several kilovolts,which poses a safety hazard to the on-orbit operation of the PPT.Although the coaxial PPT does not require a spark plug,the ignition voltage still requires several kilovolts.In addition,although the specific impulse of conventional PPT is relatively high,the thrust-to-power ratio is relatively low and the propellant utilization efficiency is not high,which limits its on-orbit application.In order to remove the spark plug,lower the ignition voltage,and increase the thrust-to-power ratio,the lightweight and miniaturization of the solid propellant PPT can be achieved.The safety and propellant utilization efficiency can be improved,and the application range of the propellant can be expanded.This paper applies the Z-Pinch principle to the PPT.Combined with self-ignition technology,a new type of pulsed plasma thruster(Z-Pinch SI-PPT)without spark plug was developed.By modifying the surface of PTFE,the ignition voltage is reduced,and the ignition and discharge are integrated,so that the spark plug is successfully removed.The two electrodes of the new thruster are made of brass.The anode is in the form of a spike.A small orifice is located at the center of the cathode,and axially flowing plasma is ejected from the orifice.At the same time,the power processing unit is designed using the principle of energy storage and boosting.The power processing unit consists of square wave signal generators,MOSFET,inductors,and battery packs.When a thruster placed in a vacuum chamber is energized,the voltage at both ends rises due to the weak conductivity of the surface of the cylindrical propellant between the cathode and the anode.The surface temperature of the propellant rises accordingly,and a small amount of propellant steam are generated.The steam discharge at a high voltage completes the self-ignition process.The propellant is ionized,the ablative product is ejected at high speed to form thrust.The electron microscope was used to scan the surface of the propellant after multiple ignition and operations.The results showed that the surface of the propellant appeared a slight carbonation phenomenon,and a small amount of continuous electrode was deposited during the working process.Sputtered metal maintained the surface's weak conductivity,enabling sustained pulses and re-ignition without spark plugs.According to the measurement requirements of Z-Pinch SI-PPT's ignition voltage,ionic current and impulse bit,several sets of experimental measurement devices were designed and built.The experimental results of more than 10,000 accumulated pulses in the vacuum chamber indicate that the main performances of the Z-Pinch SI-PPT: ignition voltage is 480 V,thrust-to-power ratio is 17.83?N/W,thrust is 85.6?N,impulse bit is 4.28?N?s,and ionic current is 40 mA.Compared with conventional pulsed plasma thrusters,the ignition voltage of the Z-Pinch SI-PPT is 24% of the coaxial pulsed plasma thruster and 2.4% of the gas short-pulse plasma thruster.Its thrust-to-power ratio is 69.8% higher than that of conventional PPT.