Table of Content

    25 August 2005, Volume 25 Issue 04 Previous Issue    Next Issue
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    Study on an Electric/Manual Hatch for the Manned Space Vehicles
    Liu Zhiquan Ji Jingquan (China Academy of Space Technology, Beijing 100094)
    2005, 25 (04):  1-7+46. 
    Abstract ( 1796 )   Save
    In order to meet the requirements of EVA (Extra-Vehicular-Activity)and RVD (RendzVous and Docking) of manned space vehicles, it is necessary to develop a hatch mechanism with high reliability and good seal performance which can be operated by both electromotion and manual. Based on analyses of the hatch characteristics of manned space vehicles, a new design project for the electric latching mechanism of the hatch is put forward. The switch mechanism used to transfer the modes of electric/manual operation is designed, which make the manual mode separate from electromotion. By software Pro/E, the models of hatch mechanism parts are constructed and assembled. Kinematic simulation on the hatch mechanism is carried out with software ADAMS. The simulation results show that the new electric/manual hatch can realize its motion correctly and has the advantage of simple structure, little resistance force and high transmission efficiency.
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    The Thermal Control Design and Simplified Theoretical Analysis of the Porthole Area in Spacecraft
    Zhang Jiaxun (China Academy of Spacecraft Technology, Beijing 100094)
    2005, 25 (04):  8-13. 
    Abstract ( 1746 )   Save
    In the design scheme, the isothermal design realized by heat pipe technique and high-efficiency heat conductance material technique is explained in details. Addtionally, on the basis of the two techniques, the equivalent heat conductance coefficient of the porthole flange in different heat transfer direction is analyzed. Finally, a mathematical model of the characteristic heat transfer process of the porthole is provided as the spacecraft operates in orbit, and its simplified analytical solution is presented.
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    Identify Space Target Solar Wing Orientation Mode by Frequency Analysis
    Dong Yunfeng Wang Ting (Beijing University of Aeronautics and Astronautics, Beijing 100083)
    2005, 25 (04):  14-18+24. 
    Abstract ( 1789 )   Save
    The orbit determination difference between space target and controllable vehicle are compared and analyzed, the solar wing orientation mode and it′s influence to orbit is discussed. The Fourier transform of distance from space target to center of earth is chosen as key parameter if the earth station orbit measure data is limited on distance, azimuth and elevation. The calculation step is given to identify the space target solar wing orientation mode. Two case is simulated and the feasibility is verified for near earth sun synchronize orbit and geostationary orbit.
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    Experimental Investigation of Deprime of a CPL Coupled with Multi Loops
    Liu Qingzhi Miao Jianyin Zhang Jiaxun Hou Zengqi (China Academy of Space Technology, Beijing 100086)
    2005, 25 (04):  19-24. 
    Abstract ( 1869 )   Save
    Evaporator maybe deprimes when a Capillary Pumped Loop (CPL) is operating, which affects its reliability greatly. Deprime of evaporator may result from many factors which are analyzed in this paper. Moreover, a multiple loop coupling CPL experiment system is developed and tests are conducted to observe transient responses and deprime procedures of the system when some thermal boundary conditions change.
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    Analysis and Calculation of Separation Process of Spacecraft Modules
    Xiao Yelun Li Chenguang (Beijing University of Aeronautics and Astronautics, Beijing 100083)
    2005, 25 (04):  25-30. 
    Abstract ( 1875 )   Save
    The process of escape and sucedent emergency separation of spacecraft modules when spacecraft rising besides aerosphere is a complex process of multi-body relative motion. The mathematic models of relative trajectory motion and attitude motion for that process, including dynamic, kinematic and geometric equations, are constructed. The combinatorial objects are defined, the relation between subject and object is emphasized, and the flight phase according to practical situation is partitioned. On the base of mathematic model, body definition and phase partition, a large-scale software to analyze and simulate is established. Some result samples of typical condition are given.
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    The Control Strategy for the Final Translation of Space Rendezvous
    Zhu Renzhang Yin Yan (Beijing University of Aeronautics and Astronautics, Beijing 100083) Tang Yi (China Academy of Space Technology, Beijing 100086)
    2005, 25 (04):  31-38. 
    Abstract ( 1657 )   Save
    The control strategy for the final translation of space rendezvous is investigated in this paper. A main aim is keeping the target vehicle in the view field of RLS. The attitude angle and the relative position coordinations of the chaser are taken as controlled variables. The lateral boundary is set according to the limited value of the azimuth angle and elevation angle of the target as well as the attitude of the chaser. The velocity increments of control maneuvers are divided into several levels.
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    Study on Coverage Characteristic of Data Transmission Antenna of LEO Satellite
    Zhang Zhengguang Ye Yunshang (China Academy of Space Technology, Beijing 100094)
    2005, 25 (04):  39-46. 
    Abstract ( 1819 )   Save
    For earth observation satellites with sun-synchronous, circular orbit and three-axis stabilization attitude, we have studied the wireless link characteristic of data transmission and coverage performance of antenna using J2 orbit model and coordinate transformation. The results show that on the elevation plane the antenna beam should be earth-matched to compensate the space loss and maintain the uniformity of received level of ground station. On the conical surface of the maximum angle, the distribution of actual antenna beam pointing is not uniform. The distribution of beam pointing ,when the satellite is entering or leaving the earth station's tracking range, is maximum along the flight direction of the satellite, and minimum in the direction perpendicular to the flight direction. So, combination of optimal beam design based on coverage statistics with proper antennas arrangement on-board, better coverage and higher quality of data link could be achieved.
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    Research on Routing Policies for Low Earth Orbit Satellite Communication System with Intersatellite Links
    Yao Ye Zhu Lidong Wu Shiqi (Institute of Communication and Information Engineering of UESTC, Chengdu 610054)
    2005, 25 (04):  47-53. 
    Abstract ( 1836 )   Save
    The traffic and topology adaptive routing algorithm conbined with topology structure and operating rules is proposed in this paper, which can increase the throughput of the system. Also, due to the dynamic topology of LEO system, the connection may be interrupted because of handover failure. In order to minimize the handover failure probability, dynamic channel reservation strategies are also taken into account at the same time. The simulation results show that the system performance can be improved as a result of dynamic channel reservation for handover calls.
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    Performance Simulation of the Mass Injection Pre-cooled TBCC Engine for Hypersonic Vehicles
    Shang Xusheng Cai Yuanhu Chen Yuchun Shang Xuhong (Northwestern Polytechnical University, Xi′an 710072)
    2005, 25 (04):  54-58. 
    Abstract ( 1852 )   Save
    According to the work mechanism of the pre-cooled TBCC (Turbine Based Combined Cycle), the pre-cooled TBCC function mathematics model that considering calculation of the alterable specific heat was set up, and the homologous calculation software was programmed. Taking the certain small scaled turbojet as an example, the influence by mass injection and pre-cooled engine was calculated and analyzed along fly trajectory. The calculation results show that, similar to the SteamJet given by the United States, adopting water injection and pre-cooled method can expand the regulations turbojet work scope consumedly, and can satisfy the request of the supersonic aircraft or two-stage-to-orbit aircraft of the first stage equip.
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    Relative States Autonomous Determination of Three Satellites Formation
    Chen Hong Chen Gucang Wang Tianxiang Wang Yuanqin (The Academy of Eqwipment Command & Technology, Beijing 101416)
    2005, 25 (04):  59-64+71. 
    Abstract ( 1768 )   Save
    In the system of relative position and attitude determination based on wireless technology, the relative states autonomous determination of three satellites formation is studied. Using parameter adjustment, matrix is singular to working precision because observation geometry is very weak. In order to resolve this problem, a new method based on weighted partial parameters adjustment to get relative position and attitude information is gived. Firstly, the system model is built. Then weighted partial parameters adjustment compares with parameter adjustment. Lastly, the result of simulation is analyzed. The results show that the relative states of three satellites formation are autonomously determinate through using the method based on weighted partial parameters adjustment.
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    An Landsat-TM Image Compression Algorithm Based on Lifting
    Zhuo Hongyan Luo Jianshu Wei Wenjian (National University of Defence Technology, Changsha 410073)
    2005, 25 (04):  65-71. 
    Abstract ( 1839 )   Save
    Based on analyzing the coefficient characteristic of inter wavelet transformed, the 3D SPECK compression of multispectral image is put forward. In the method the zero-tree coding of compression of wavelet transform is extended to the compression of multispectral image. Integer wavelet transform is applied to reduce spatial decorrelation, and DCT is applied to reduce the inter-band correlation. 3D SPECK is used in processing transformed wavelet coefficient. The results of experiment indicate that hardware is easier to realize, the time of coding and decoding is less, and the requirement of EMS memory is fewer.
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