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25 October 1996, Volume 16 Issue 05 Previous Issue    Next Issue

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MATHEMATICAL MODEL OF LIQUID NITROGEN SYSTEM OF SPACE ENVIRONMENTAL SIMULATOR Jia Yang (Beijing Institute of Spacecraft Environment Engineering, Beijing 100029) 1996, 16 (05):  .  Abstract ( 1688 )   Save A mathematical model of liquid nitrogen system of a space environmental simulator is introduced and a quasi-stationary control method is developed in this paper. The variables describing the system characteristics include pressure, temperature, height of liquid, flow, etc. The input variables to the system include travel of valve, heating power, pressure of liquid nitrogen in cooler, heat load, etc. For convenience, a single-phase hermetic cycle system is divided into three blocks: cooler block, pump block and cryogenic sink block. The equations describing pressure and temperature of the three blocks are obtained, and then the mathematical model is built. The pressure, temperature and flow at each critical point in the system are obtained by solving the equations. The regulating valves of the liquid nitrogen system are typical nonlinearity elements, so the control of coupling loops is difficult. Two types of quasi-stationary control method of the regulating valves are developed in this paper, namely absolute regulating method and relative regulating method. The first method depends on the measurement of the flow of each pipe. The secondmethod does not require it and can be used in the nonlinearity control of the valves. The result shows that relative regulating method has many advantages: small overshoot, short regulating time and simple algorithm, which are needed for the control of liquid nitrogen system. Related Articles | Metrics

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ESTIMATION OF SYSTEM ERROR FOR TRACKING DATA OF FREE FLYING TRAJECTORY Wang Zhengming Yi Dongyun(Department of Engineering and Mathematic of National University of Defense Technology, Changsha, 410073) 1996, 16 (05):  .  Abstract ( 2001 )   Save The continuous wave radar is the main tracking equipment for trajectory observing at present. Estimation and calibration of system errors have important significance. In this paper, according to that the trajectory equation in free flyiny can be obtained accurately, we build a nonlinear model for estimating system error of free flying trajectory by use of trajectory equation and give the relevant algorithm. Specially, by use of this method, we can give high precision estimation of system error only using the tracking data of a set of MISTRAM. Related Articles | Metrics

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A NEW IDEA TO SELECT BASE FUNCTION FOR METHOD OF MOMENT Yang Jisong Fu Junmei(Xi'an Institute of Space Radio Technology,Xi'an 710000) (Xi'an Jiaotong University,Xi'an 710049) 1996, 16 (05):  .  Abstract ( 1524 )   Save By analyzing and contrasting the characteristics of entiredomain and sub-domain base functions selected in a general method of moment, the idea and practically realizing method to construct multi-scale sub-domain base function is put forward. Through the computation of several examples, it is confirmed that a stable solution can be achieved by adopting this new kind of base function in the method of moment. Related Articles | Metrics

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METHOD OF STRENGTH CHECK AND PREDICTION OF LIFE TIME FOR WINDOW GLASS OF SPACECRAFT Song Lixin Hu Xingfang(Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050)Wu Gouting (Beijing Institute of Spacecraft Systems Engineering, Beijing 100086) 1996, 16 (05):  .  Abstract ( 1698 )   Save In this paper, the method of proof test and failure predication for thermal tempered glasses has been established for the first time, based upon fracture mechanics and the distribution of stress in thermal tempered glass, which provids the theoretical foundation for the strength check of the window glass of spacecraft. The results of calculation examples show that the permissible loads will different in different application environment, even if the glass has passed the same test stress in prooftest. The life time of glass under the same load also depands greatly on the environmental conditions. Related Articles | Metrics

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STUDY OF PREPARING FILMS ON LARGE AREA FLEXIBLE SUBSTRATE FOR SPACE APPLICATION Lu Yusun Feng Yudong Li Hua (Lanzhou Institute of Physics, Lanzhou 730000) 1996, 16 (05):  .  Abstract ( 1448 )   Save In this paper, report the characteristic and requirement of preparing large area films on the flexible polymer for the space application, the structure and performance of the facility developed for the large area continuously coating. The requirement and effects of magnetron and plasma deposition electric field in continuously coating on large area flexible substrate are discussed deeply, and the preparation technique, properties, evaluation method and results of flexible conductive SSM (Second Surface Mirror) are also described. Related Articles | Metrics

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SIMULATION OF INFLUENCE OF FILTER'SPHASE-FREQUENCY CHARACTERISTIC ONREMOTE SENSING IMAGE QUALITY Guo Zhaozeng Zhou Fan Li Lingzhi (Beijing Institute of Satellite Information Engineering, Beijing 100080) 1996, 16 (05):  .  Abstract ( 1911 )   Save In this paper, used simulation method to analyze and compare the influences of phase-frequency characteristic of Butterworth and Elliptic filters and sampling keeper and their parameters on image quality. The influences include edge degradation, resolution reduction, generation of new strip, geometric distortion and reduction of registration accuacy of multi-spectral image and so on. Related Articles | Metrics

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LOW THRUST ORBITAL TRANSFER OF SMALLSATELLITE UNDER 3-AXIS ATTITUDESTABILIZATION MODE Jing Wuxing Wu Yaohua Wang Xuexiao Yang Di (Harbin Institute of Technology, Harbin 150001) 1996, 16 (05):  .  Abstract ( 1612 )   Save Small satellite launched together with a main satellite often needs orbital maneuvers to enter its working orbit.The orbital maneuvers are implemented bysmall thrusters. Burning information under low thrust is studied for a small satellite transfering from a elliptic parking orbit to its circular working orbit. Horizontal thrust strategy and constant pitch angle thrust strategy are simulated, and conclusions useful for flight mission design are presented. Related Articles | Metrics

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EXPERIMENTAL TECHNIQUES FOR DETECTING COMPOSITE LAMINATES Shen Zuwei (Beijing Institute of Space Machine and Electricity, Beijing 100076) 1996, 16 (05):  .  Abstract ( 3358 )   Save Three experimental techniques for detecting matrix cracking evolution in composite laminates are investigated: acoustic emission detection, ultrasonic wave C-scan, and replica tape record. In various test stages, the advantages of each test method should be fully used so that more test data can be obtained for each specimen than those in the regular tests, including acoustic emission hit response diagram, ultrasonic wave scanning image throughout the specimen width, and replica tape picture along the edge thickness. The first acoustic emission hit corresponds to the matrix cracking initiation during loading. Through the ultrasonic scan, this first matrix crack can be clearly identified. With the development of the matrix cracking, all the techniques are combined to determine the matrix fracture evolution. Based on the test results, these techniques are evaluated. Related Articles | Metrics

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EXPERIMENTAL INVESTIGATION ONCHARACTERISTICS OF EVAPORATOROF TWO-PHASE CAPILLARY PUMPED LOOP Wang Jinliang Ma Tongze Zhang Zhengfang (Institute of Engineering Therrnalphysics, CAS, Beijing 100080) 1996, 16 (05):  .  Abstract ( 1750 )   Save Based on the investigation of the inverted type evaporator of a two-phase capillary pumped loop (CPL), the improved experimental study of the same evaporator was carried out in this paper. The improved method is the addition of an aluminium plane with vertical and horizontal channels on the compositemetal screens (the capillary structure). The obtained experimental results about the working characteristics of the evaporator with different inclination angles of CPL were analyzed and compared. Related Articles | Metrics

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AN IMPROVED FAST ADAPTIVE ALGORITHM FOR DIGITAL BEAMFORMING Wang Zhong Zhang JiHong Huang Shunji (University of Electronic Science and Technology of China, Chengdu 610054) 1996, 16 (05):  .  Abstract ( 1692 )   Save This paper provides an improved fast adaptive algorithm for digital beamforming. It is an algorithm with strictly constrained minimum power sampling matrix gradient (CSMG). It has merits of both traditional sampling matrix gradient (SMG) and strictly constrained minimum power adaptive algorithm. The outputs of computer simulation are given. The result indicates that direction of beam will change as constraint angle changes. It can adaptively adjust zero very well. The algorithm are fast convergent. Related Articles | Metrics