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    Feasibility analysis of airbreathing plasma propulsion system
    YANG Zhaolun, GUO Ning, CHEN Xuekang, YAN Nengwen, WANG Cong
    Chinese Space Science and Technology    2020, 40 (1): 54-.   DOI: 10.16708/j.cnki.1000-758X.2020.0007
    Abstract344)      PDF(pc) (1591KB)(303)      
    The airbreathing plasma propulsion system has been studied as a potential technology for longlife super low altitude flight. According to different orbital environmental conditions, the feasibility of the airbreathing plasma propulsion system was discussed by using the tubular inlet and the mechanical pressurization suction method. The analysis shows that the ratio of the total power required by the spacecraft to the windward surface should be greater than 2kW/m2, and that the specific impulse of the plasma thruster should be greater than 4×104m/s, so as to meet the requirements of pushdrag balance. It is pointed out that in order to realize the application of suction system in earth orbit, the key technology is to increase gas collection efficiency and reduce collection power consumption, while the efficiency of plasma thruster needs to be further improved.
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    Attitude and orbit coupling control for fly-around observation of multi-satellite proximity operation
    XU Ying, ZHANG Jin, YU Moyao, XU Dandan
    Chinese Space Science and Technology    2019, 39 (6): 21-.   DOI: 10.16708/j.cnki.1000-758X.2019.0046
    Abstract305)      PDF(pc) (6611KB)(172)      
    Aiming at the observation mission of multi-satellite proximity operation, dynamics models of relative attitude and orbit are established. Two kinds of desired triangular formation configurations of observation satellites in elliptical and space circular orbits are considered respectively. The desired attitude is designed that the observation satellite's line of sight always points to the target satellite. The proportional-differential control law based on the quaternion and angular velocity error feedback and an improved guidance method based on artificial potential field method are used to control the relative attitude and orbit. The simulation results show that all observation satellites can effectively track the desired relative attitude and desired relative orbit under the action of the control law. In the triangular formation configuration of space circular orbit, after starting from the same initial position, the formation configuration of three observation satellites always keeps a regular triangle. Moreover, the side length of the regular triangle increases gradually from zero to finally the desired value.
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    Verification on electromagnetic vector modulation of plasma flow generated in helicon plasma thruster#br#
    DING Liang, ZHENG Huiqi, PENG Yuchuan, REN Qiongying, ZHAO Hua
    Chinese Space Science and Technology    2020, 40 (4): 38-43.   DOI: 10.16708/j.cnki.1000-758X.2020.0043
    Abstract276)      PDF(pc) (10374KB)(142)      
    The electromagnetic vector modulation of electrical thruster′s flow is based on magnetic field reforming which leads to the orientation altering of plasma flow. To verify the electromagnetic vector modulation of electrical thruster, the theoretical simulation and experiments were carried out for the helicon plasma thruster (HPT). The magnetic field can be altered with electromagnetic vector modulation coils illustrated in theoretical simulation results. The plasma flow is deflected as the magnetic field is adjusted as shown in experimental results. Plasma density fluctuates according to an accessional magnetic field generated periodically. The plasma flow changes its orientation with 60 degrees at most with a modulated frequency which reaches 15Hz. The electromagnetic vector modulation for helicon plasma thruster is verified feasible.
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    Parameter selection and control of field emission electric thrusters
    LIU Zijian, SHEN Yan, GENG Jinyue, LIU Xuhui, QIN Yu
    Chinese Space Science and Technology    2020, 40 (4): 1-10.   DOI: 10.16708/j.cnki.1000-758X.2020.0039
    Abstract269)      PDF(pc) (5166KB)(217)      
    Field emission electric thrusters have different working modes, and can produce either droplets or ions. The thrust parameters change widely due to different charge to mass ratio of the charged particles.For different space applications, different types of field emission electric thrusters need to be designed to achieve the corresponding thrust parameters. The emission process of the thrusters and the selection and control method of the thrust parameters were discussed. The basic working principle of field emission electric thrusters and each working mode were discussed. The calculation results show that different emission modes can be achieved with different propellants, followed by the conclusion that the thrust parameters are controlled by the propellants′ species, extract voltage and propellant flow rate, etc. Design and experiment results of an ionic liquid electro spray thruster show that the thrust and specific impulse produced by the thruster can be modified by changing the applied voltage. The thrust and specific impulse can reach 16~10μN and 154~978s respectively.
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    High speed onboard router based on LEO constellation
    LYU Yuancao, WANG Fengchun, XU Nan, HAN Xiaodong, FENG Yanjun, XING Chuan
    Chinese Space Science and Technology    2019, 39 (6): 87-.   DOI: 10.16708/j.cnki.1000-758X.2019.0054
    Abstract249)      PDF(pc) (5344KB)(160)      
    With the explosion of the internet traffic, the IPbased large volume data transmission provided by satellite network becomes a prerequisite to integrate satellite network and terrestrial network. Onboard router,whose transmission rate and QoS (Quality of Service) determine the throughput and efficiency of the entire network,is the key facility of the satellite network. Based on the low throughput of existing onboard routers, a design of high speed onboard router for LEO (Low Earth Orbit) satellite constellation is proposed. Implementing dynamic routing into the snapshotbased routing scheme makes it possible to minimize packet drop when link failure happens. This scheme enables iterative data switching after one time route computing. By using sharedmemory mode to build switchingmemory unit, also with Spacewire and Serdes interface units deployment, the intersatellite throughput can achieve up to 51 Gbit/s in theory. Moreover, the onboard router supports IPbased transmission, which lays the foundation for integrating with terrestrial network.
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    Numerical study of electromagnetic acceleration mechanism for pulsed plasma thruster
    YANG Sanxiang, LIU Chao, WANG Shangmin, FENG Jie, CHEN Juanjuan, WU Chenchen, JIA Yanhui, GUO Ning, GENG Hai
    Chinese Space Science and Technology    2020, 40 (4): 11-21.   DOI: 10.16708/j.cnki.1000-758X.2020.0040
    Abstract210)      PDF(pc) (12440KB)(164)      
    In order to get a clear understanding of electromagnetic acceleration mechanism for pulsed plasma thrusters, and offer a theoretical foundation for the performance optimization and minification of the thruster,numerical simulation of the pulsed plasma thruster characteristic is necessarily to be researched. In this paper, a onedimensional integrated circuit model that includes the capacitance, inductance, electrodes and plasma is used to numerically study pulsed plasma thrusters. The electromagnetic acceleration mechanism of pulsed plasma thrusters is systematically investigated by varying the initial discharge voltage and separation distance of the electrodes. The results show that the thrust, specific impulse, impulse bit of pulsed plasma thrusters, and temperature and density of plasma increase with initial discharge voltage. Similarly, the thrust and specific impulse of thrusters also increase with the separation distance of electrodes. However, the igniting difficulty of thruster increases since the resistance between electrodes increases with the electrodes spacing. Therefore, there is an optimal value of distance between electrodes of the pulsed plasma thruster. 
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    High specific impulse Hall thruster startup characteristics
    CHEN Jie, KANG Xiaolu, ZHAO Zhen, CHENG Jiabing, LIANG Wei
    Chinese Space Science and Technology    2020, 40 (4): 22-28.   DOI: 10.16708/j.cnki.1000-758X.2020.0041
    Abstract202)      PDF(pc) (4663KB)(143)      
    High specific impulse Hall thrusters have been valued from the early stage of the development of Hall thrusters, but there are few studies on parameter comparison, current changes and oscillation characteristics related to engineering applications. The performance and startup characteristics of HET80HP high specific impulse Hall thruster were given by measuring the thrust, current variation and oscillation of the thruster under different working conditions. The research results show that HET80HP high specific impulse Hall thruster has better performance than the traditional Hall thruster under the conditions of large flow rate and high discharge voltage. During cold start, there is a current spike in the discharge current under normal magnetic field conditions, and the current takes a long time to achieve relative stability. The variation of current during the hot start of different magnetic field configurations indicates that the presence of current spikes is mainly related to the magnetic field configuration and has no obvious relationship with the startup  temperature. In addition, by comparing the difference in thruster specific impulse and average frequency under different magnetic fields, it can be seen that the average frequency of lowfrequency oscillation of thruster can better reflect the magnitude of thruster specific impulse.
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    Design of LEO satellites augmented constellation for navigation
    TIAN Ye, ZHANG Lixin, BIAN Lang
    Chinese Space Science and Technology    2019, 39 (6): 55-.   DOI: 10.16708/j.cnki.1000-758X.2019.0050
    Abstract195)      PDF(pc) (7032KB)(58)      
    A constellation design method of LEO (Low Earth Orbit) satellites augmentedconstellation for navigation is presented since global LEO satellites becoming a hot spot. Firstly, the relationship between the orbit altitude and the visible spherical crown is deduced, thus the constellation altitude can be computed with the space debris distribution, economy and collision risk. Then, the relationship between the elevation and the orbit inclination is derived, and meanwhile the constellation inclination is determined to get north and south poles coverage. Next, compared with Iridium, it is demonstrated that a single constellation can′t achieve a uniform visible satellites distribution and DOP(Dilution of Precision)on global scale. Finally, an LEO satellites constellation design method is proposed, which can achieve global coverage while make the DOP (Dilution of Precision) and the visible satellites distribute evenly around the world. The results show that the mixed constellation designed by the method can achieve a global coverage and even distribution of visible satellite numbers and DOP.
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    Emergency return analysis of hybrid trajectory based on one impulse for human lunar mission
    LYU Pengwei, SHANG Zhi, WANG Ping
    Chinese Space Science and Technology    2020, 40 (1): 1-.   DOI: 10.16708/j.cnki.1000-758X.2020.0001
    Abstract191)      PDF(pc) (3881KB)(127)      
    For human earthmoon transfer mission, emergency return trajectories are key to astronauts′ safe return to earth. Emergency return trajectories based on human translunar hybrid trajectory were proposed, considering safety the most important requirement in human earthmoon transfer mission. There are three emergent return methods,which are direct return, immediate transfer and steer by the moon, and steer by the moon and return. The characteristics of transfer time and velocity increment of the three emergent return methods were studied. The advantages and disadvantages of the three emergency return methods were analyzed, providing reference for translunar trajectory selection in subsequent human lunar exploration missions.
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    Design of satellite-borne microwave photonic mixer based on DDMZM
    HUI Jinxin, ZHAO Ying, DENG Xiangke, ZHENG Feiteng, SUN Shufeng
    Chinese Space Science and Technology    2020, 40 (3): 36-42.   DOI: 10.16708/j.cnki.1000.758X.2020.0030
    Accepted: 19 February 2020

    Abstract176)      PDF(pc) (2308KB)(76)      
    Due to the influence of distributed parameters on microwave components, there is certain frequency selectivity, and it is difficult to achieve the broadband and multi-band compatible frequency conversion system, which can no longer meet the needs of the high-throughput satellite communication payload. Microwave photonics technology provides the possibility of realizing high-throughput satellite communication needs with its advantages of large bandwidth and no frequency selectivity. Based on dual-drive Mach-Zehnder modulator (DDMZM), the solution of the frequency conversion unit of the satellite communication system was explored. Through theoretical analysis of the link model, the software VPI was used to simulate and optimize the link to find the best offset point of the DDMZM. The experimental results show that when the modulator is biased at the minimum point, the frequency conversion efficiency is high, and it has certain carrier suppression function, which can achieve broadband, multi-band and anti-interference performance,and is superior to microwave frequency conversion performance.
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    Cfield optimization for magnetic state selection of cesium beam tube based on PID algorithm
    CHEN Shi, WANG Ji, HUANG Liangyu, LIU Zhidong
    Chinese Space Science and Technology    2020, 40 (2): 54-.   DOI: 10.16708/j.cnki.1000-758X.2020.0020
    Abstract174)      PDF(pc) (3810KB)(75)      
    Optimization for Cfield of magnetic state selection cesium beam tube was introduced. The test system developed for cesium beam tube provided the necessary test environment, and different kinds of PID control algorithms were designed to optimize and analyze Cfield of cesium beam tube. Finally a more reasonable optimization parameter was obtained. By optimizing multiple cesium beam tubes, the frequency difference between the (0~0) peak and ±1 peak of the cesium beam tube was controlled within the range of 42820kHz ± 20Hz. By comparison with the results from an earlier cesium beam tube test platform, the error of the optimal Cfield current does not exceed 002 mA, which verifies the correctness of the optimization results.
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    Influence of 3D regular surface morphology on secondary electron emission
    ZHANG Na, CUI Wanzhao, CAO Meng, WANG Rui, HU Tiancun
    Chinese Space Science and Technology    2020, 40 (3): 1-7.   DOI: 10.16708/j.cnki.1000.758X.2020.0025
    Accepted: 04 March 2020

    Abstract170)      PDF(pc) (3603KB)(80)      
    It has been applied in many fields to customize specific surface morphology to control secondary electron emission of materials.The regular surface morphology can easily reveal the influence of the suppression and the influence mechanism on the secondary electron emission. Meanwhile, photolithography, plasma etching and other processes can better achieve the specific design of regular morphology. Therefore, custom regular morphology is often used in the initial research stage of multipactor or in the process of principle experimental verification. Taking the threedimensional cylindrical hole as an example, multi-generation Monte Carlo method which considers multiple interactions between electrons and complex surface morphology was used to systematically study the influence of regular morphology parameters such as depthwidth ratio and duty cycle ratio on secondary electron yield (SEY), secondary electron spectrum (SES) and emission angle distribution. It was found that the larger the depthwidth ratio of regular morphology is, the wider the SES broadening, the stronger the selectivity of the morphology to emission angle, and the better restraint effect of SEY, but the restraint effect is not indefinite. When the morphology does not overlap, SEY can also be effectively reduced by increasing the duty cycle ratio. However, due to the relatively small proportion of emitted electrons of the cylindrical hole compared with flat surface, the SES and the emission angle distribution is close to flat surface. The secondary electron emission properties of regular morphology obtained in the paper provide a reference for the comprehensive evaluation of its influence on multipactor effect.
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    Effect of temperature on magnetic field configuration of magnetically shielded Hall thruster#br#
    ZHAO Zhen, CHENG Jiabing, KANG Xiaolu
    Chinese Space Science and Technology    2020, 40 (4): 29-37.   DOI: 10.16708/j.cnki.1000-758X.2020.0042
    Abstract169)      PDF(pc) (6885KB)(64)      
    Magnetostatic simulation in room temperature condition is mostly applied for Hall thruster design and verified with measurement in non-working state. Severer thermal issues will be addressed for larger power Hall thrusters and result in magnetic deviation under high temperature. In order to study thermal influence, 10kW Hall thruster thermomagnetic coupling simulation was carried out. Comparing both results, discrepancy of magnetic radial component on Br centerline near anode was larger than that in exit. Magnetic shielding obtained in room temperature simulation was deviated in thermal state with non-compliance between field and wall up to 13%, through wall shape recorrection, magnetic shielding was restored with noncompliance below 4.8%. Reasonable design reduced thermal loads. Simulation showed that the maximal circuit temperature was less than 500℃, lower than 0.78 times of Curie temperature, which would not lead to sharp drop in magnetic performance, but thermal impact on magnetic configuration needs to be considered in magnetic shielding simulation.
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    Research on unconventional dynamic problems for #br# small satellites
    BAI Zhaoguang, YANG Xinfeng, CUI Yufu, LIU Zhijia, DENG Weihua
    Chinese Space Science and Technology    2019, 39 (6): 1-.   DOI: 10.16708/j.cnki.1000-758X.2019.0044
    Abstract168)      PDF(pc) (2387KB)(139)      
    Some special dynamic problems encountered in small satellites were studied, and the corresponding solutions were developed. To solve the difficulties of analysis and test for high level shock much higher than the frequentlyused shock test standard spectrum, a method was proposed to analyze the high level shock. As for problems in strength design under random vibration for small satellites, the influence of the modal effective mass ratios and modal frequencies on quasistatic load computation was studied. The analysis shows that neglecting the coupling of modal effective masses and the coupling of modal frequencies leads to large error in quasistatic load computation under random vibration. The method for quasistatic load computation with consideration of the coupling of modal effective masses was proposed. Finally, the study on vibration reduction was carried out for a small satellite, and the vibration reduction for sine vibration and random vibration was analyzed. The calculation method of the main frequency for vibration reduction system with symmetrical installation was given.
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    A high accuracy pointing control method for space target
    FENG Tiantian, GAO Jingmin
    Chinese Space Science and Technology    2020, 40 (2): 1-.   DOI: 10.16708/j.cnki.1000-758X.2020.0013
    Abstract166)      PDF(pc) (3717KB)(134)      
    In order to meet the requirement of high accuracy control for satellites in space moving target pointing missions, the control method of the twolayer attitude system by the spacecraft base and fine steer mirror (FSM) are considered. The high accuracy pointing control method for space moving targets is presented. First, the position information of tracking satellite and target satellite was obtained based on the ClohessyWiltshire equation of the nearcircular orbit. Then, the multiple information fusion extended Kalman filter was adopted to estimate tracking satellite attitude. The relative attitude between tracking satellite optical axis and target satellite was calculated in real time so as to obtain the azimuth and elevation angle required for tracking and pointing control. Finally, fast and high accuracy pointing to the target satellite was realized through spacecraft base firstlayer attitude control and payload optical axis secondlayer pointing control based on FSM. Simulation results show that the proposed method can keep dynamic pointing error less than 072″. The method presented can realize high accuracy tracking and pointing control of space target and can provide technical support for space missions such as laser communication.
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    Thermal characteristics optimization of hollow cathode
    YU Bo, SONG Na, KANG Xiaolu
    Chinese Space Science and Technology    2020, 40 (1): 45-.   DOI: 10.16708/j.cnki.1000-758X.2020.0006
    Abstract160)      PDF(pc) (4056KB)(219)      
     The hollow cathode commonly serves as an electron source in ion or Hall propulsion systems, and its thermal characteristics exert a great impact on the cathode’s performance and life time. In order to study the temperature distribution and heat consumption power of the operating hollow cathode, a numerical analysis was conducted. The cathode temperature distribution in steady state was solved by combining the fluid calculation (F process) and the heat transfer calculation (HT process), in which both the F process and the HT process provided the input conditions to each other and iterated over again. A temperature measurement test was performed to justify the model’s accuracy. Five measurement points were set on the cathode surface, and the temperatures solved by the calculation were compared with test results. The maximum calculation error is less than 5%, based on which the thermal characteristics were modeled with different cathode structures and materials. The results show that the heat consumption power presents a trend of firstdecreasethenincrease with the cathode changing from a shorter length to a longer one; the heat consumption power increases and the temperature decreases when higher emissivity keeper shell is adopted.
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    Research on passive intermodulation based on broadband modulation signal
    LI Yanping, HUANG Hao, HE Jie
    Chinese Space Science and Technology    2020, 40 (3): 13-18.   DOI: 10.16708/j.cnki.1000.758X.2020.0027
    Accepted: 17 February 2020

    Abstract158)      PDF(pc) (1204KB)(82)      
    With the extensive use of transmitter-recevier sharing and digital modulation (BPSK,QPSK) technologies in satellite communication, there are insufficient verification problems in the original continuous wave (CW) and passive inter modulation (PIM) test system. In this paper, a broadband digital signal PIM test method was designed by using the channel power to test PIM. The test results show that digital modulation PIM values of both BPSK and QPSK signals are higher than the CW carriers by 2~9 dB. Considering the operational reliability of the satellite, the digital modulation working mode was adopted to improve the original test system and the new test is closer to the pracical work, which improves the reliability of ground verification.
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    Control method of fast launching and positioning for geostationary satellites#br#
    CHEN Jizheng, SUN Songtao, FENG Gang, XIAO Yuzhi
    Chinese Space Science and Technology    2019, 39 (6): 47-.   DOI: 10.16708/j.cnki.1000-758X.2019.0049
    Abstract157)      PDF(pc) (6501KB)(112)      
    A method of fast launching and positioning for GEO satellites is proposed. After the satellite is launched into the GTO orbit, it is maneuvered into any designated position in the GEO orbit by the upper stage or by itself within 48 hours. Considering the constraints of time and TeleTracking & Controlling, the nominal trajectory of fast positioning is optimized for minimizing fuel consumption. Based on the nonsingular Equinoctial orbital elements, an explicit guidance is proposed for spacecraft maneuvering and positioning with finite thrust. The simulation shows that the fast launching and positioning control of GEO satellite can be achieved by using the proposed maneuvering strategy, trajectory optimization method and guidance law.
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    Ionospheric VTEC fusion based on BP neural network technology
    GUO Chengjun, PANG Guoqiang
    Chinese Space Science and Technology    2020, 40 (4): 78-83.   DOI: 10.16708/j.cnki.1000-758X.2020.0048
    Abstract154)      PDF(pc) (3366KB)(43)      
    With the continuous development of ionospheric detection technology, there are more ionospheric observation data. Using only a single observation datum will cause the problem of low accuracy of ionospheric inversion. In order to improve the inversion accuracy of the ionosphere, the BP neural network technology is used to effectively fuse the vertical total electron content (VTEC) data of ground-based inversion and international reference ionosphere (IRI) model inversion. Ionospheric inversion experiments were performed in temperate regions [35°(N)--45°(N),60°(E)--80°(E)\]. The results show that the data fusion based on BP neural network technology and ground-based inversion can both achieve high accuracy of ionospheric VTEC. The data fusion method based on BP neural network has higher ionospheric inversion accuracy than ground-based inversion, so data fusion based on BP neural network technology can improve the ionospheric inversion accuracy.
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    Design of L-band space based wideband low noise amplifier chip
    ZHAO Bochao, XU Hui, YIN Pan, HE Juan, ZHANG Dawei, XU Xin
    Chinese Space Science and Technology    2020, 40 (3): 19-24.   DOI: 10.16708/j.cnki.1000.758X.2020.0028
    Accepted: 04 March 2020

    Abstract153)      PDF(pc) (4040KB)(104)      
    An L-band monolithic microwave integrated circuit (MMIC) low noise amplifier (LNA) used in satellite microwave receiver was developed with 0.25μm GaAs pseudomorphic high electron mobility transistor (pHEMT) technology. The current reuse topology structure was used to achieve lower current and the precious satellite power resource was saved. The two-stage negative feedback was applied to increase stability and gain flatness, and then satellite communication quality was improved. The constant current source bias stabilized the working conditions where current was slightly influenced by the processes. The test results show that the working current is below 35mA, from 0.9GHz to 1.8GHz, the gain is higher than 33dB with gain flatness less than 0.5dB, the noise figure is below 0.6dB, and the size of the LNA chip is 2.0mm×1.3mm. The circuit can meet the requirement of high performance and miniaturization in space application.
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