System Design And Performance Analysis Of Co-axial Micro Cathode Arc Thruster

Micro-nano satellite has been developing rapidly in recent years.As a micro-propulsion system which provides attitude control and station keeping for micro-nano satellites,it has gained more attention than before.A kind of co-axial micro cathode arc thruster is developed in this paper.Its working principle is as follows: the pulsed high voltage is used to excite an arc,to generate the plasma.The generated plasma is accelerated by the multi-physical field to be ejected from the thruster to generate the thrust force.The thrsuter has the advantages of light weight,small size,low power consumption and low cost,which meets the requirements of micro-nano satellite's space propulsion.In this paper,the working principle of ?CAT system is analyzed in detail,and a set of co-axial ?CAT prototype is developed according to the relevant theory.The key technologies,including arc ignition,uniform ablation of cathode and applied magnetic field system,have been broken.?CAT consists of a coaxial arrangement of rod copper anode and cylindrical titanium cathode.The vacuum arc ignition without spark plug can be achieved by coating conductive film on the surface of the insulator between anode and cathode.The experiments showed that ?CAT can fire repeatedly and the ignition voltage is only several hundred volts.A set of external magnetic field system is developed,and the magnetic field configuration and specific parameters are determined by theoretical analysis and simulation.Based on the principle of inductive energy storage and boost,the power processing unit with adjustable operating frequency and duty cycle is designed.MOS's on-off state is controlled by square wave generator,and then MOS determines the inductor charging/discharging and thruster pulse frequency.More than 100,000 times of pulsed ignition experiments were carried out in the vacuum chamber,and the plume image,discharge characteristics and cathode ablation of ?CAT were analyzed.The influence factors of impulse duration were investigated and analyzed experimentally.The results show that pulse duration increases when energy storage increases or applied magnetic field strength decreases.To get the key performance parameters of ?CAT and explore the working mechanism,several sets of experimental devices were designed and built.The cathode loss rate was measured by accurate electronic balance.To solve the problem of measurement of thrust in the order of ?N,a device which is based on shooting method was established to measure the impulse bit of ?CAT.Through analyzing the plume spectrum which was measured by spectrograph,the particle composition in the plume was obtained.An ionic current measuring device was set up,and the ionic current under different external magnetic fields was collected,measured and analyzed using a ball-and-barrel collector plate.The results show that the thruster can keep working stably and the ignition voltage is about 620 V.The plume is mainly composed of Ti+ and Ti atoms and the ionization rate ranges from 9% to 14%,which is changed with applied magnetic field.The impulse bit,specific impulse and thrust-topower ratio are 0.485?N·s,195.6s and 2.62?N/W respectively without external magnetic field.The application of external magnetic field can effectively improve the thruster performance parameters.When external magnetic field's magnetic induction intensity is 0.044 T,the impulse bit,specific impulse and thrust-to-power ratio are 1.285 ?N·s,518.2s and 6.91?N/W respectively.The average thrust of ?CAT is in the order of 10 ?N.