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25 October 1997, Volume 17 Issue 05 Previous Issue    Next Issue

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AN INTRODUCTION TO CONFIGURATION OF CO LOCATED GEOSTATIONARY SATELLITES Zhan Hu Han Chao (Beijing University of Aeronautics and Astronautics,Beijing 100083) 1997, 17 (05):  .  Abstract ( 2060 )   Save Co located geostationary satellites are described as a group of GEO satellites that share the same nominal longitude and a common control box of typical ±0 1° in latitude and longitude.It's convenient to study relative motions in a reference orbital coordinate system using Clohessy Wiltshire equation,provided that the reference orbit is a standard geostationary orbit.However,a set of modified C W equation is presented to avoid a defect of the original C W equation.The satellites follow a combined eccentricity and inclination vector separation strategy,so that the group geometry can be expressed simply by the orbital elements of each member.The group geometry in space (or reference to ground station)can be keeped unchanged with a simple modification of the orbital elements of each member. Related Articles | Metrics

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RECENT DEVELOPMENT OF PARTICLE REINFORCED METAL MATRIX COMPOSITES Li Qinghao Zhao Changxi Liu Hongyang (Beijing Spacecraft,Beijing 100080) Yan Yue (Beijing Institute of Aeronautical Materials,Beijing 100095) 1997, 17 (05):  .  Abstract ( 1699 )   Save Metal Matrix Composites are developing towards the large scale commercialization.Among all kinds of Metal Matrix Composites,Particle reinforced Metal Matrix Composites (PMMCs)takes up the first position due to its low cost product and comprehensive excellent properties.The mechanical properties and physical properties of typical PMMCs were listed.And then the application in space structure and problems existing with regards to farbrication technologies and engineering applications were analyzed,and the measurements which were usually taken to settle these problems were presented. Finally ,the paper briefly previewed the development of PMMCs in China. Related Articles | Metrics

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ON ENVIRONMENTAL TEST AND RELIABILITY OF SPACECRAFT Jin Xunshu (Beijing Institute of Satellite Environment Engineering,Beijing 100029) 1997, 17 (05):  .  Abstract ( 1849 )   Save The paper discusses the role of environmental testing in ensuring improving the reliability of spacecrafts,explains the relationship between environmental testing and reliability testing.According to th author,there is no difference between these two kinds of testing for spacecraft development.Brief introduction is given on the enviromental test of spacecrafts in foreign countries.Some suggestions are made concerning the more effective use of environmental testing as a tool for improving reliability in the development of spacecrafts. Related Articles | Metrics

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A STUDY OF LEAKAGE DETECTING WITH MASS SPECTROMETRY UNDER NON VACUUM ENVIRONMENT Yan Zhiping Huang Shuying (Beijing Spacecraft,Beijing 100080) 1997, 17 (05):  .  Abstract ( 1634 )   Save An economical and practical leak detecting method of mass spectrometry with a part checked in non vacuum container is described.Experiments showed this method is correct.The sensitivity,detecting error and the calibrated leak rate were analysed theoretically. Related Articles | Metrics

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STUDY ON REAL TIME PROCESSING ALGORITHM OF GEOMETRIC CORRECTION FOR CCD REMOTELY SENSED IMAGERY Chen Xiao He Zhiqin (Beijing Institute of Satellite Information Engineering,Beijing 100080) 1997, 17 (05):  .  Abstract ( 1999 )   Save Since the processing of remote sensing images is increasingly in real time,it is important to propose a new geometric correction algorithm for imagery of linear and area array charge coupled devices(CCD),which can be used to fast and accurately calculate the corrected geometric positions and resample their gray scales.In this paper,the relational expression to shift one dimensional position is proved to be a cubic multinomial,to which fast recurrence can be applied finely,and the one dimensional resample algorithm is also described,both offering great time savings.When every line of an image has been done accordingly ,the lines of longitude and latitude is indicated as well,based on positioning data given by GPS.So far,a rectified image product with complete 1B level is available.Simulation tests with PC have showed that the algorithm is believed to achieve real time capability if multiple processors are introduced appropriately. Related Articles | Metrics

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MANNED SPACECRAFT LAUNCHING WINDOW AND SOLAR ARRAY OPTIMUM SUNSHINE Xi Xiaoning Wu Ruilin Pan Liang Ni Shouhu (National University of Defense Technology,Changsha 410073) 1997, 17 (05):  .  Abstract ( 1952 )   Save In this paper,firstly,based on the basic features of spacecraft orbit,the formulae are deducted which are those of the optimum angle between the solar direction and the normal direction of solar array of spacecraft and the sunshine factor of circular orbit;Then,according to theoretical analysis,the coefficients of efficiency of the solar array are derived;Finally,having the aid of computer algebra system MATHEMATICA,a direct,clear and simple method is set,which can be used for analyzing the optimum sunshine of the solar array.The results may be of reference value to selection of launching window of a spacecraft. Related Articles | Metrics

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OPTIMIZATION OF SMALL THRUST SPACE ENGINES SYSTEM Wang Zhongwei Zhang Weihua Hu Xiaoping Wang Zhenguo (National University of Defense Technology,Changsha 410073) 1997, 17 (05):  .  Abstract ( 1896 )   Save Based on mass models and models of drift for pressure-feed, liquid propellant space engines system, optimization and analysis of combustion chamber pressures and gas tank shape are carried out in this paper. Some important conclusions are obtained: ① Total mass of the space engines system is reduced to a minimum with optimal pressure value of 1MPa; ② For the space engines system with annular gas tanks, the system mass is smaller and the drift of center of mass of a spacecraft is zero. Related Articles | Metrics

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A METHOD FOR GPS POSITIONING BASED ON LINEAR ALTERNATION OF MEASUREMENT EQUATION Wang Zhong Zhang Jihong Huang Shunji (University of Electronic Science and Technology of China,Chengdu 610054) 1997, 17 (05):  .  Abstract ( 1792 )   Save This paper provides a method that makes measurement equation linear,which is a method that equation reduction rank of direction method is used in measurement equation.Computer simulation shows this approach is efficient. Related Articles | Metrics

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OPTIMIZATION ON A FIN TUBE RADIATOR OF AIRCRAFT UNDER MICRO GRAVITY Zhang Xuexue Liu Jing Zhang Chao (Tsinghua University,Beijing 100084) 1997, 17 (05):  .  Abstract ( 1935 )   Save A heat transfer model on a fin tube radiator under micro gravity is established in this paper.The maximum heat discharge per unit mass and the minimum power to drive fluid are adopted as the optimum objects,and the fin tube radiator of aircraft is thus optimally analyzed.The DSFD method is applied to solve a non linear optimum problem with multi objects and multi constraints and the method to optimize the fin tube radiator on the whole is postulated.The optimum designing parameters for the fin tube radiator is provided as a result. Related Articles | Metrics

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LEARNING DIAGNOSIS METHOD BASED ON NEURAL NETWORK MODEL Ji Changwei (Beijing Polytechnic University,Beijing 100022) Rong Jili Huang Wenhu (Harbin Institute of Technology,Harbin 150001) 1997, 17 (05):  .  Abstract ( 1516 )   Save Fault tree model based diagnosis divides the bottom events of the fault tree into three parts: certain fault sources(CFS)、normal event sources(NES) and possible fault sources(PFS), but it is not clear how to determine the states of the elements in PFS (normal or abnormal). With lots of training examples, learning diagnosis method based on neural network is applied to determine the states of the elements in PFS, and its effectiveness is demonstrated by diagnosing a principle fault simulation testbed of any satellite power system. Related Articles | Metrics

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ON STABILITY OF A DEPLOYABLE/RETRACTABLE FLEXIBLE STRUCTURE Zhang Honghua (Beijing Institute of Control Engineering,Beijing 100080) 1997, 17 (05):  .  Abstract ( 1973 )   Save This paper deals with stability of a deployable flexible structure.It is resulted that the motions of the structure include the attitude motion,dimension motion and flexible vibration;the dynamics of the structure can be described by using hybrid partial differential and ordinary equations.It is proved that the dissipation and accumulation of the vibration energy depends on the dimension motion:in deploying phase the energy is dissipated and in retracting phase the energy is accumulated.Thus,it is concluded that vibration motion of the structure is stable in deploying phase and unstable in retracting phase. Related Articles | Metrics