Table of Content

    25 August 2020, Volume 40 Issue 4 Previous Issue   
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    Parameter selection and control of field emission electric thrusters
    LIU Zijian, SHEN Yan, GENG Jinyue, LIU Xuhui, QIN Yu
    2020, 40 (4):  1-10.  doi: 10.16708/j.cnki.1000-758X.2020.0039
    Abstract ( 482 )   PDF (5166KB) ( 367 )   Save
    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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    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
    2020, 40 (4):  11-21.  doi: 10.16708/j.cnki.1000-758X.2020.0040
    Abstract ( 432 )   PDF (12440KB) ( 245 )   Save
    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
    2020, 40 (4):  22-28.  doi: 10.16708/j.cnki.1000-758X.2020.0041
    Abstract ( 499 )   PDF (4663KB) ( 298 )   Save
    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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    Effect of temperature on magnetic field configuration of magnetically shielded Hall thruster#br#
    ZHAO Zhen, CHENG Jiabing, KANG Xiaolu
    2020, 40 (4):  29-37.  doi: 10.16708/j.cnki.1000-758X.2020.0042
    Abstract ( 371 )   PDF (6885KB) ( 104 )   Save
    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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    Verification on electromagnetic vector modulation of plasma flow generated in helicon plasma thruster#br#
    DING Liang, ZHENG Huiqi, PENG Yuchuan, REN Qiongying, ZHAO Hua
    2020, 40 (4):  38-43.  doi: 10.16708/j.cnki.1000-758X.2020.0043
    Abstract ( 537 )   PDF (10374KB) ( 190 )   Save
    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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    Research on intelligent cooperative attitude control of assembled spacecraft#br#
    WU Jiaqi, KANG Guohua, HUA Yinmiao, ZHANG Han, ZHANG Qi
    2020, 40 (4):  44-53.  doi: 10.16708/j.cnki.1000-758X.2020.0044
    Abstract ( 312 )   PDF (5252KB) ( 131 )   Save
    The control force borne by each single satellite in the process of attitude maneuver of assembled spacecraft is uneven. In this paper, the interaction model between the assembled spacecrafts was established to analyze the relationships between internal forces,internal torque and attitude,control torques respectively based on the theory of multi-body dynamics. The distribution of internal torques under extreme conditions was simulated, which may exceed the bearing range of torque of common docking mechanism. The particle swarm optimization (PSO) algorithm was used to optimize the distribution of control torques, and the convergence rate of PSO algorithm was speeded up by default initial values and inheritance initial values. Real-time adjustment of control torque distribution reduced the interaction between satellites and realized the intelligent cooperative control of assembled combination, to ensure that the connection hinge of assembled spacecraft would not be damaged due to excessive force. The simulation of the algorithm and the verification analysis of Adams software show that the interaction model established in this paper can accurately calculate the inter-star interaction force, and the proposed intelligent cooperative attitude control algorithm can significantly reduce the interstar internal force in the process of attitude control, ensuring the safety of the assembled spacecraft.
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    Fast reentry landing footprint calculation using differential evolution algorithm#br#
    LIN Jun, HE Yingzi, HUANG Panxing
    2020, 40 (4):  54-60.  doi: 10.16708/j.cnki.1000-758X.2020.0045
    Abstract ( 291 )   PDF (2543KB) ( 119 )   Save
    A hybrid optimization method based on differential evolution algorithm and bank angle interpolation was proposed for the reentry landing footprint calculation of high lift-drag ratio hypersonic vehicle. The reentry process equality constraints and inequality constraints were added to the optimization index by designing the penalty function and the fitness function maximization. In order to reduce the search space of the parametric bank angle profile, a constrained differential evolution algorithm was used to solve the reentry trajectory that satisfies the process constraints and terminal constraints. After obtaining bank angle profiles with the maximum cross-range and down-range voyages respectively, the interpolation bank angle method was used to quickly produce the bank angle command set, and then the fast calculation of the reentry landing footprint was realized. The simulation is designed with the high lift-to-drag ratio vehicle CAV-H. The results show that the hybrid optimization solution is easy to implement and has good maneuverability.
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    Improved multiscale filtering algorithm of multisensor integrated navigation system#br#
    LIN Xueyuan, SUN Yumei, DONG Yunyun, QIAO Yuxin, CHEN Xiangguang
    2020, 40 (4):  61-68.  doi: 10.16708/j.cnki.1000-758X.2020.0046
    Abstract ( 267 )   PDF (3643KB) ( 101 )   Save
    Multi-scale filtering algorithm has been successfully used in multisensor integrated navigation system, but this algorithm uses measurement vectors at different times, thus causing heavy computation burden and affecting the system′s real-time performance. According to the shortcomings of the application, the block partition technique and wavelet transformation were used to change the system state equation described in timedomain into block state equation. Then,the real-time measurement vector was expressed in the form of block state equation. At last, an improved multi-scale filtering method of multi-sensor integrated navigation system was established using Kalman filter and sequential filter. The algorithm was applied to the GPS/SST/SINS multisensor integrated navigation system, and the simulation results show that this algorithm has not only better realtime and recursive performance, but also better fused precision.
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    Study on maneuver methods of satellites constellation with continual small-thrust propulsion
    YANG Shengqing, WANG Yu, WANG Danna, LIN Rongfeng, DU Yaoke, ZHONG Chao
    2020, 40 (4):  69-77.  doi: 10.16708/j.cnki.1000-758X.2020.0047
    Abstract ( 409 )   PDF (4819KB) ( 166 )   Save
    Based on the orbit dynamic characteristics, orbit maneuver methods of satellites constellation with continual small-thrust propulsion are studied in this paper. Because of the huge scales of constellations, orbit maneuver of constellation in near-earth orbit can hardly be managed by traditional method as trajectory planning. Orbit insertion for constellation configuration is considered as a relative semimajor axis control problem in timedelay maneuver sequence. Meanwhile, offset control of inclination is considered for drift of right ascension of ascending node(RAAN) during arisingorbit maneuver. For consideration of orbit discarded problem, a unitedcontrol for combination of semimajor axis and eccentricity is designed for a rapid orbit decay with energy-saving. Because of the curveeffect for continual smallthrust propulsion, curvilinear integral of orbit control should be investigated for all the strategy optimizations.
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    Ionospheric VTEC fusion based on BP neural network technology
    GUO Chengjun, PANG Guoqiang
    2020, 40 (4):  78-83.  doi: 10.16708/j.cnki.1000-758X.2020.0048
    Abstract ( 352 )   PDF (3366KB) ( 124 )   Save
    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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    Research on trusted fullproxy homomorphic transmission  mechanism for satellite communication#br#
    DING Yi, SHEN Wei, LI Jie, CHENG Zijing, JIN Jun, SUN Jianing
    2020, 40 (4):  84-96.  doi: 10.16708/j.cnki.1000-758X.2020.0049
    Abstract ( 377 )   PDF (6604KB) ( 150 )   Save
    Satellite communication and its applications have become an important part in current social life. In order to ensure the secure transmission of satellite communication data, privacy protection of information, and to sovle the problem of dependency on the receiving side, a set of full proxy reencryption transmission model (FPRM) was proposed based on typical application scenarios of the transmission of low orbit constellation meteorological data. It was instantiated according to the satellite communication architecture to design a trusted proxy homomorphic transmission system. Computable ciphertext and full proxy transmission have been implemented by adding security of system communication and privacy protection to the mechanism. It is of great practical significance and values to integrate satellite, commercial data centers and Internet resources to reduce costs and improve resource utilization. Finally, it proves that the performance and data scalability of this model are feasible through experiments.
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    Research on policybased remote sensing satellite control method
    XU Yudong, HAO Jigang, LIU Boyang
    2020, 40 (4):  97-106.  doi: 10.16708/j.cnki.1000-758X.2020.0050
    Abstract ( 362 )   PDF (5263KB) ( 181 )   Save
    For the problems of complex operation and many manual interventions caused by the tight coupling of business applications and underlying scheduling in remote sensing satellite management and control, a policy-based remote sensing satellite control method is proposed. On the basis of constructing the policy management model, the closed loop structure of hierarchical control is adopted to complete the closed loop of satellite control. A domain management method for satellite clusters is proposed, and a policy deployment mechanism is set up. The implementation method of policy-based remote sensing satellite management and control is discussed in detail. Simulations are performed on a typical case of the search mission for a lost ship, and it is verified that the method can complete eventbased closedloop control of heterogeneous satellite clusters. The policybased management method can effectively reduce the complexity of remote sensing satellite management and control services, and realize the automatic control of remote sensing satellite clusters.
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    A yaw angle adjustment strategy during IGSO satellite orbit maintaining#br#
    CUI Zhen, JI Ye, LIU Weijie, WANG Chunyuan, FENG Jiajia
    2020, 40 (4):  107-112.  doi: 10.16708/j.cnki.1000-758X.2020.0051
    Abstract ( 333 )   PDF (2318KB) ( 133 )   Save
    Aiming at the problem of maintaining the orbit of the inclined geosynchronous orbit (IGSO) satellite, a yaw angle adjustment strategy under various working conditions was proposed. The purpose was to reduce the yaw angle adjustment range and shorten the yaw angle adjustment time, and to reduce the impact of the orbit maintenance process on the continuity of satellite services. The law of yaw angle motion and the effect of the right ascension of ascending node on the yaw angle were analyzed. On this basis, the influences of the right ascension of ascending node, the range of the solar altitude angle, the orbit control time, and the position of the intersection on the yaw angle adjustment strategy were analyzed. The method of adjusting the yaw angle and the choice of thruster when the satellite orbit is being maintained were given. For satellites whose intersections are located in China, the range of yaw angle adjustment does not exceed 45°. This method can be applied to the  management of satellite orbit maintenance.
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