Laser ablation micro propulsion technology is one of the space micro propulsion technologies. It is a kind of electric propulsion technology based on the principle of laser propulsion. It can be used for micro nanosatellite attitude and orbit control. In this paper, the development of laser ablation micro propulsion technology is reviewed. The basic theory is briefly described. The research status is discussed. Various types of micro thrusters are compared and analyzed. Combined with the characteristics of laser ablation micro propulsion technology, the development trend is analyzed, and suggestions are given for reference.

Micro cathode vacuum arc thruster has the advantages of simple structure, light weight, low power consumption and high specific impulse, thus has a broad application prospect in the field of space propulsion. Currently, some key problems encountered in the thruster design and development, reliability and lifetime improvement are closely related to the basic physics of the micro cathode vacuum arc discharge process. In this paper, the electron emission, inter electrode arcing process, cathode spot formation and characteristics, ablation and morphological changes, and plasma jet acceleration process involved in the operation of micro cathode arc thruster are reviewed, and the related understanding can lay the foundation for further micro cathode arc thruster design optimization and performance improvement in the future.

Radio frequency(RF) ion thrusters occupy an important position in the field of electric propulsion due to the advantages of high specific impulse, long life, high efficiency, and high reliability. In order to further reduce the mass and volume of the propulsion system and reduce the cost, new RF ion thrusters are developed, like the freeneutralizer RF ion thrusters. In this paper, the research and development status of traditional RF ion thrusters are summarized, the key technologies in RF ion propulsion technology are analyzed. The principle and research progress of freeneutralizer RF ion thrusters are summarized, and the development direction of RF ion thruster is given.

In recent years, in order to meet the needs of space missions such as deep space exploration, manned spaceflight and onorbit service of spacecraft, the highpower electric propulsion technology with high thrust, high specific impulse, long lifetime and high thrust density has attracted the continuous attention of many scholars. Compared with other types of high power electric propulsion technologies, Electrodeless Lorentz Force (ELF) has obvious advantages in thrust density, thrusttoweight ratio and overcomes the restriction of electrode erosion on the lifetime of high power electric thrusts. According to the research status of high power electric propulsion equipment, this paper compares the similarities and differences of the technical approaches in the development process of the ELF thruster, introduces the development of each component in detail, analyzes the problems encountered in the research process, and puts forward the key research directions of ELF thrusters in the future.

Hydroxylammonium nitrate (HAN)/1ethyl3methylimidazolium ethylsulfate(［Emim］［EtSO4］) blend ionic liquid propellant is a potential replacement with nontoxic, highperformance and high degree of ionization characteristics for hydrazine type liquid propellants, which can be used in both chemical and electrical propulsion system. This paper introduces the thermogravimetric experimental analysisdifferential scanning calorimetry (TGADSC) results of HAN/［Emim］［EtSO4］ ionic liquid propellant with the thermal decomposition and catalytic decomposition process. Its massloss process and exothermic process under different reaction conditions at a heating rate of 5 K/min~15 K/min are studied. Generally, the massloss results show that there are four characteristic stages during the decomposition process of the ionic liquids, and the DSC curves show that there are two obvious exothermic processes in the decomposition. Using catalyst can significantly reduce the decomposition temperature of the propellant and the residual mass. Finally, a model thruster with 200 mN thrust is developed. The results of hot fire test show that the propellant can be ignited stably by catalyst. And it has a good application prospect in space propulsion.

A joint simulation method of liquid sloshing of liquid tanks based on UDP communication protocol is firstly introduced in this paper. The method uses FLUENT to calculate the liquid sloshing force, moment and center of mass results of the moving tanks. Based on the satellite dynamics program, the linear and angular velocities are calculated through control algorithms and strategies after obtaining the tank sloshing results. The twoway data exchange between them is achieved through a communication interface developed in C/C++ code. Then, with the help of the above joint simulation method, the joint simulation analysis of the tank sloshing is carried out and compared with the inorbit remote sensing data. And then the liquid sloshing characteristics of the four tanks in pitch 0~25° maneuvers are analyzed. Finally the liquid sloshing characteristics of the blades with and without holes under the control of the satellite dynamics are compared and analyzed. Under nontrajectory conditions, the peak sloshing force and moment of 2nd and 3rd tanks are larger than those of 1st and 4th tanks. The peak Ydirectional sloshing force of the four tanks is in the range of 1.05 N~1.96 N. The moment values are in the range of 0.05 N·m~0.36 N·m. The stirring effect of the blades with holes on the liquid is weaker than that of the blades without holes. The bubbles stirred by the nonporous blades show a significant stretching and centrifugal motion, and result in greater fluid velocity.

A numerical and experimental study of pulse mode characteristics in a MMH/NTO rocket Engine is proposed via a reduced chemical kinetic model including 20 reactions and 23 species devoted to the gas phase reaction of monomethyl hydrazine/nitrogen tetroxide (MMH/NTO). The results show that the combustion chamber pressure reaches stability rapidly, related 3.7ms to 8ms. The chamber wall heat flux first increases and then decreases, and the film cooling efficiency is significantly affected by the pulse width. The combustion chamber pressure increases and decreases similarly in different pulse mode, and the engine can deliver a steady thrust or impulse after 2.5 ms~3 ms.

To investigate the transient startup of ADNbased 1N monopropellant thruster and provide the reference for the inorbit application, through the Hotfiring test in high altitude simulated vacuum chamber，the influences of preheating temperature, injection pressure, working time on transient startup are studied. The ADNbased 1N monopropellant thruster t90is experimentally obtained with respect to various test conditions. It is shown that the t90 decreases first and then increases with the increase of preheating temperature. When the injection pressure drops, the t90 increases. The ignition test of ADNbased propellants stored for 4 years is investigated. The evaluation results indicate that the t90 is stable in the storage time.

In order to improve the performance of electrospray thruster and beam extraction efficiency, the electric field distribution and particle trajectory of the electrospray thruster with different structural parameters are simulated via the COMSOL software. The results show that under the condition of a certain extraction voltage, the emitter tip field intensity is significantly affected by the emitter structure. It increases with the increase of the emitter rib width and rib spacing. The extraction grid structure has a significant effect on the beam extraction efficiency. Compared with the straight structure, the expansion structure has a better extraction efficiency. The increase of the width of the extraction grid hole is also conducive to the improvement of the extraction efficiency. The distance between the emitter and the extraction grid also has a great effect on the extraction efficiency, and reducing the distance between the two grids is beneficial to improve the extraction efficiency. The horizontal assembly error will obviously affect the trajectory of the emitted particles, but has little influence on the extraction efficiency.

In this paper, a onedimensional simulation model of a selfpressurized butane micropropulsion system is developed via AMESim+AMESet. The key components of this model contain: selfpressurized butane storage tank, stabilized gas accumulator, PIDcontrolled electrically heated thrust, etc. The static operating characteristics of the selfpressurizing tank, solenoid valve, gas accumulator and thruster are first studied, the effects of gas accumulator and thruster heating power and thruster expansion ratio on the system operating characteristics are analyzed, and finally the dynamic response characteristics of the butane propulsion system are discussed. The results show that the fluid in the selfpressurized tank can achieve the stable pressure under the control of the temperature control system. The response of the system is faster at variable target thrust. Increasing the volume of gas volume is helpful to improve the working stability of the system.

Cavitation is a common phenomenon in industrial production, ship propulsion, aerospace and other fields. In this paper, a highspeed camera is used to observe the flow field in a rotating cavitation generator in a closed cycle test rig, and the numerical simulation is carried out based on the RNG kε turbulence model and the ZwartGerberBelamri cavitation model. The results show that the numerical simulation results are in good agreement with the experimental observation data, which verifies the accuracy and reliability of the numerical simulation method. Due to the centrifugal force, the pressure in the hole increases gradually from the rotor inside to outside. At the bottom of the hole, large vortexes appear and energy are dissipated due to the effect of axial vortex. The fluid at the hole top interacts with the main flow, impacts on the hole top side, and finally forms a weak vortex. Different hole geometries have an important influence on the cavitation effect of the rotating cavitation generator. Under the same condition, the cavitation intensity of the elliptical hole is less than that of the conical hole and cylindrical hole, which indicates that the hole geometry with smooth profile has less local loss and induces the weaker cavitation. For different hole geometries, the dominant frequency of pressure pulsation in rotating cavitation generator is the rotation frequency fi or 24fi (corresponding to the number of hole rows in the circumferential direction), and the maximum pressure pulsation occurs at the inlet pipe side and the outlet pipe side, mainly due to the influence of rotorstator interaction.

Micro satellites are widely used in scientific research, traffic navigation, natural disaster forecasting, urban planning, environmental monitoring, national defense security, etc. However, liquefied gas propulsion device, which is often used in micro satellite systems, has a problem that its propellant is not completely vaporized, resulting in a decrease in propulsion performance. To effectively control the gasification process, based on electrical capacitance tomography (ECT) technique, the visualization and void fraction detection method of the liquefied propellant gasification process are presented in this paper. A 6electrode flexible PCB sensor is designed to improve the signal noise ratio of the measurement and reduce the difficulty in processing. Due to the poor image quality of the 6electrode ECT system, a pixel interpolation method is proposed based on linear back projection (LBP) and Tikhonov regularization. The mapping model from gray value to void fraction is also established. Simulation results show that after applying pixel interpolation, the average relative error of the reconstructed image is reduced by 7.72%, and the image quality is significantly improved, with the void fraction measurement error significantly reduced (less than 4.86%). Finally, based on the actual situation of micro satellite propellant gasification, an experiment setup is established, which proves the feasibility of the proposed method.

The joint modeling scheme of several main nonlinear characteristics of piezoelectric actuator is studied, including hysteresis, creep and temperature drift. A cascaded single hidden layer feedforward neural network based on NARMAX model is proposed to eliminate the influence of hysteresis. The information criteria and error reduction ratio algorithm are used to determine the regression factors which have the greatest influence on the model error as the input nodes of the network. The experimental results show that the absolute error of the network on the test dataset can be reduced to no more than ±0.1 μm via the multinetwork generalization and regularization. By leveraging the running time, the measured value of the temperature sensor and the frequency of input voltage into the input nodes, the nonlinear factors caused by creep and temperature drift can be compensated, and the final absolute error on the test set can be limited to ±0.01 μm. The network has good generalization ability for different excitation voltage frequencies. The research results can be used as reference in the modeling of multiple nonlinear coupling piezoelectric actuators.

Lowfrequency oscillation is one of the most important problems of Hall thrusters. The use of RLC filter unit is one of the most common method to reduce the discharge current lowfrequency oscillations. For highpower Hall thrusters, the problems of high direct current power consumption and serious heat generation exist in RLC filter. This paper proposes and describes a novel filter with coupled inductor. The filter with the coupled inductor structure has obvious notch characteristics through reasonable parameter settings, and has the effect of better suppressing lowfrequency oscillation. The circuit model is simulated, and the attenuation effects of different parameters on the lowfrequency oscillation frequency signal and the influencing factors of notch frequency are obtained. The results show that the filter with coupled inductance structure can effectively reduce the inductance value, thereby reduce the power consumption and heat generation of the filter. In theory, the coupled inductance structure filter with notch characteristics has better suppression characteristics for lowfrequency oscillation. It can effectively reduce the interference of the lowfrequency oscillation of the discharge current to the power supply system, and has significant engineering application value.