Table of Content

    25 October 2018, Volume 38 Issue 5 Previous Issue    Next Issue
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    Influence of hygrothermal environment on discharge characteristics of modified barium tungsten emitter hollow cathode
    FENG Jie, LIU Mingzheng, GU Zengjie
    2018, 38 (5):  1-6.  doi: 10.16708/j.cnki.1000-758X.2018.0049
    Abstract ( 892 )   PDF (4892KB) ( 365 )   Save
    The traditional barium tungsten hollow cathode has the advantages of low working temperature and high emission efficiency, but its antipoisoning ability is poor. The life of electric thruster is mainly limited by hollow cathode. To ensure the longterm onorbit working of thruster, a new kind of modified barium tungsten cathode with a strong antipoisoning ability was developed. The cathode was exposed to environment of 90% humidity, 60℃ and accumulated 240h.The discharge voltage variation before and after test was less than 1V, satisfing the requirement of criterion. The test results also show that the steady working temperature of the modified barium tungsten cathode is 1050℃, 250℃ lower than that of lanthanum hexaboride type cathode. The componentlevel anode voltage is 21V, 4~5V lower than the lanthanum hexaboride hollow cathode. The thrusterlevel anode voltage is 35V, 8~10V lower than the lanthanum hexaboride hollow cathode. The experimental results show that the modified barium tungsten cathode has strong antipoisoning ability and excellent performance, and the application of the cathode can effectively meet the long life requirement of the thruster.
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    An investigation of the sputtering influence on the solar panel by Hall thruster plume
    YU Bo, WANG Xuan, YU Shuilin, KANG Xiaolu
    2018, 38 (5):  7-16.  doi: 10.16708/j.cnki.1000.758X.2018.0051
    Abstract ( 350 )   PDF (11662KB) ( 173 )   Save
    The sputtering effect of the Hall thruster plume has a large influence on operating performance and power support stability of the solar panel. In order to study the sputtering mechanism of plume bombarding on the solar panel under different installation conditions of Hall thruster, a hybrid model based on Particle in Cell/Directional Simulation of Montecarlo Collisions was employed ,and the ion diffusion model was corrected to solve the plume field. Meanwhile, the Yamamura sputtering model was used to calculate the sputtering yield on the solar panel caused by the plume bombardment. A diagnose test of plume in the vacuum chamber was conducted to verify and correct the feasibility and accuracy of the calculation model, and the diffusion coefficient was corrected to make calculation agree with the test. According to the comparison between the test and calculation results, the error of the calculation model is about 87% with kd=126×10-36N·m4. Based on those, the corrected model was used to calculate the sputtering yield on the solar panel with different onorbit conditions of thruster installation angle and thrusterpanel distance. The calculation results provide the changing rules of the surface sputtering mass distribution on the panel under different conditions, and the light transmittance influenced by sputtering was also predicted. This paper can provide a reference of Hall thruster installation strategy on the satellite.
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    Plasma discharge characteristics of wall segmentation with high biased electrode in Hall thruster
    LI Wenqing, DUAN Ping, HU Xiang, SONG Jilei, BIAN Xingyu, CHEN Long
    2018, 38 (5):  17-29.  doi: 10.16708/j.cnki.1000-758X.2018.0052
    Abstract ( 326 )   PDF (40698KB) ( 209 )   Save
    Hall thruster plasma has strong interactions with the channel wall. In order to reduce the surface corrosion and enhance the lifetime, a twodimensional physical model was established based on the discharge process of Hall thruster, and a Particleincell (PIC) simulation method was applied to study the influences of segmented low emissive graphite electrodes on discharge characteristics of the Hall thruster channel. The influences of biased segmented electrode arranged in the ionization region on electric potential, ion number density, electron temperature, ionization rate, discharge current and impulse were discussed. The results show that segmentation of high biased electrodes at different positions in the ionization region has obvious influences on the plasma discharge characteristics. When the electrode position is in the front ionization region and the electrode bias voltage is 60V higher than the anode, the plasma parameters of discharge channel are almost unchanged. When the electrode is at the end of the ionization region, and the electrode bias voltage is 18V higher than the anode, the accelerating region expands axially, the ion velocity vectors are more focused, the electron temperature increases significantly which decreases the interaction between electrons and wall, and the divergence angle of the plume also reduces. The thruster specific impulse increases about 12%, the performance and lifetime of the thruster are improved.
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    Analysis of external magnetic field of MPDT superconducting magnetic nozzle
    YAO Lu, YANG Wenjiang, WANG Baojun, TANG Haibin
    2018, 38 (5):  30-37.  doi: 10.16708/j.cnki.1000-758X.2018.0054
    Abstract ( 378 )   PDF (10553KB) ( 208 )   Save
    The traditional liquidcooled copper coils which provide applied magnetic field have significant disadvantages such as large volume, big mass and high power dissipation. Therefore, hightemperature superconducting (HTS) magnets have received widespread attention in the application of appliedfield magnetoplasmadynamic thruster (AFMPDT) because of their tiny volume, low power dissipation and high current density. Due to the critical characteristics of superconductor material, HTS magnets are susceptible to quenching due to the influence of external magnetic field. In this paper, by simplifying the discharge circuit of MPDT, simulation and experimental methods were used to analyze the magnetic field of discharge simulator, and to study the influence on the HTS magnet. The simulation results show that the magnetic field inside the MPDT discharge chamber is mainly composed of the circumferential direction, and due to the shielding effect of the anode current, there is almost no magnetic field distribution outside the discharge chamber. The experimental results also achieved good agreement with the simulation. Therefore, when designing a HTS magnetic nozzle, it is not necessary to consider the influence of the magnetic field from the discharge chamber. This research provides a reference for the application of the HTS magnet on the AFMPDT.
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    The energy distribution mechanism in an ablative pulsed plasma thruster
    HUANG Tiankun, WU Zhiwen, ZHU Kangwu, YU Xuewen, WANG Jinhai
    2018, 38 (5):  38-45.  doi: 10.16708/j.cnki.1000-758X.2018.0055
    Abstract ( 353 )   PDF (4620KB) ( 344 )   Save
    Pulsed plasma thrusters ( PPTs) have been criticized for their low efficiency over long time periods. However, few studies were about the PPT energy distribution mechanism which is very important for providing references for the designs of highperformance PPTs. In this paper, a parallelplate ablative pulsed plasma thruster was studied. The voltage, current and ablated mass of the PPT were measured under four different discharge energies. The propulsion performance of the PPT was estimated by the experimental data. In addition, a numerical model was established and used to calculate propellant utilization of a PPT. The results show that the low efficiency of PPTs comes form their low energy utilization and low propellant utilization. As the discharge energy increases, the PPT efficiency and energy utilization increase from 5.07% to 16.5% and from 2.88% to 5.23%, respectively. However, the propellant utilization decreases from 56.8% to 31.8% as the discharge energy increases.
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    The effect of magnetic topological structure on the performance of the annularengine
    CHEN Juanjuan, ZHANG Tianping, LIU Mingzheng, WANG Yanlong, YANG Hao, LI Xingda, YANG Le
    2018, 38 (5):  46-54.  doi: 10.16708/j.cnki.1000-758X.2018.0056
    Abstract ( 349 )   PDF (8069KB) ( 262 )   Save
    To obtain the most appropriate magnetic topological structure to improve the discharge efficiency and reduce the discharge loss of the annularengine, this paper studied the effect of different types of magnetic structure on the discharge process of the annular discharge channel. By applying the PIC/MCC method to simulate the generation and transport process of the plasma, this paper analyzed the influence of magnetic field distribution on the distribution of plasma, the loss rate and the discharge stability. According to the statistical results, the discharge performance curve of the annularengine was obtained and validated by the experimental results. The results show that the ringcusp magnetic refines the motion of the primary electrons better than the mulipole field, it can reduce the loss rate significantly, increase the probability of the collision between electrons and neutral atoms, improve the discharge efficiency and decrease the discharge loss.
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    The development of research on plasma propulsion with electronegative gases
    ZHANG Junjun, XIA Guangqing, ZHOU Siqi, HAN Yajie
    2018, 38 (5):  55-62.  doi: 10.16708/j.cnki.1000-758X.2018.0057
    Abstract ( 402 )   PDF (3254KB) ( 492 )   Save
    In the wide application of electric thrusters, most of them work on the principle of accelerating positive ions only to provide moderate thrust and high specific impulse. The ion beam current and space charge need to be compensated by the additional neutralization systems in the downstream space to avoid selfcharging of the satellites, damage of the communication equipment and electronic devices as well as cancellation of the acceleration field. In order to simplify the system structure and prolong the life of thrusters, a space electric propulsion system where both positive and negative ions can be accelerated alternately to obtain the thrust was proposed. The background and present situation of the development of plasma propulsion with electronegative gases (PEGASES) were introduced. The way to generate and accelerate positive and negative ions simultaneously was also discussed, including how to choose electronegative gases, magnetic field filter design requirements, the applied bias voltage way for grids in which the positive and negative ions could be accelerated alternately and periodically, as well as the density diagnostics of the plume.
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    A measurement method of dynamic thrust based on cantilever beam
    WANG Dapeng, ZHOU Weijing, CAO Jihong, ZHANG Shan, SHI Xiaoyun, HE Long
    2018, 38 (5):  63-71.  doi: 10.16708/j.cnki.1000-758X.2018.0048
    Abstract ( 353 )   PDF (7046KB) ( 198 )   Save
    To realize dynamic thrust measurement in spaceborne micro thrusters′ performance assessment, the transfer function of the measurement system was determined based on cantilever′s dynamic model.System input and output characteristics were analyzed, and a terminal mean method for solving the steadystate displacement was put forward according to cantilever beams′ characteristics that the response speed is high (vibration frequency is high), the dynamic component is close to constant amplitude oscillation in a small time interval (damping ratio is small), and that the higher order vibration can be regarded as the noise for fundamental frequency vibration. By eliminating the dynamic components in the displacement response, the time variant value of the static displacement was obtained when the error band was large, and thus the dynamic thrust measurement was realized. According to the linear relationship between the thrust magnitude and the steady displacement under the action of step force with the linear coefficient as the system gain value, the parameter calibration method was put forward. An experimental platform was built with response time 156ms by calibration. By comparison with measurement results of torsional balance system, the relative error 4.064% between the impact force on cantilever and the actual thrust was obtained, and the thrust measurement error 4.293% was finally obtained by combination with the measurement error 1.383% of impact force itself.
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    Magnetic circuit design for micro cathode arc thrusters
    GENG Jinyue, ZHOU Siqi, XIA Guangqing, CHEN Jun, SHEN Yan
    2018, 38 (5):  72-80.  doi: 10.16708/j.cnki.1000-758X.2018.0050
    Abstract ( 366 )   PDF (9915KB) ( 362 )   Save
    The microcathode arc thruster is one of the microelectric thrusters, which uses the vacuum arc to erode the cathode material and produce highly ionized high speed plasma, then pull out under the applied magnetic field to generate the thrust. The magnetic circuit design is the important work in the thruster design, it will affect the stability and the performance of the thruster. The multiturn solenoid calculation formula, 2D and 3D simulations were conducted in the magnetic circuit design, and the magnetic field strength increases with the increasing of coil current and coil turns. When the coil current is 15A and the coil has 600 turns, the maximum magnetic field strength along the discharge channel center line is more than 0.3T. The simulation results are in good agreement with the measured results by the Tesla meter. Finally, the timeofflight (TOF) method was used to measure the plasma velocity, it increases with the enhancement of magnetic field strength.
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    Dragfree system modeling and parameters optimization based on cusped field thruster
    LI Bin, SUN Qiangqiang, LIU Hui, YU Daren
    2018, 38 (5):  81-89.  doi: 10.16708/j.cnki.1000-758X.2018.0053
    Abstract ( 380 )   PDF (8998KB) ( 260 )   Save
    With the breakthrough progress of the satellite gravity measurement technology, the demand for the spacecraft's experimental environment increases, and the residual disturbance of the spacecraft must be reduced as far as possible.As the cusped field thruster of China's future alternative gravity thrusters for measuring satellites, the control accuracy of thrusters directly determines the measurement accuracy. A dragfree controller with state mode was designed by the PID method. The controller performs well in predicting the performance of the drag coefficient, the reference mass, the displacement difference and the speed difference of the satellite body. When dealing with satellite operation sudden situation it showed strong stability. However, the PID parameters didn′t reach the optimal solution. Based on this, the control accuracy of the model was optimized. The genetic algorithm was used to filter the PID control parameters. The results show that the control accuracy of the cutoff thruster has improved, the speed and displacement errors in the NTW direction are reduced, the thrust resistance is significantly reduced, the control accuracy is improved, and the requirement is better satisfied.
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    Design and experiment of a new Z-Pinch PPT
    SHI Baochun, WANG Pingyang, LIANG Ke, TIAN Leichao
    2018, 38 (5):  90-97.  doi: 10.16708/j.cnki.1000-758X.2018.0058
    Abstract ( 453 )   PDF (5505KB) ( 373 )   Save
    A new type of pulsed plasma thrusters based on the Z-Pinch principle without igniters was developed. In order to reduce the discharge voltage and size, the discharge chamber consists of a solid inner anode and a hollow cathode with an orifice. The space between the electrodes is occupied by a hollow cylindrical bar of modified polytetrafluoroethylene (PTFE) propellant which can be selfignited. Compared with conventional Z-Pinch PPT and pulsed plasma thrusters in the literature, the advantages of this new PPT lie in no moving parts, igniter and igniter power supply. The envelope size of this PPT is about 21mm and the mass is 15g. Based on the advantage of high thrusttopower ratio, the discharge voltage peak of the new PPT is 24% of the coaxial PPT, and 2.4% of the gasfed PPT. Experiment result based on over ten thousand shots shows that this PPT works well, and the ignition voltage is 480V, the thrusttopower ratio is 17.83μN/W and thrust is 85.6μN.
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