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分子凝结与凝结表面温度的关系机理研究 总被引:6,自引:0,他引:6
飞行器所用大量非金属材料在轨道环境下将发生出气逸出行为。逸出的分子极易沉积凝结于光学系统表面或其它敏感表面形成分子污染,且这种分子凝结行为的量级与附着强度和凝结表面的温度有最为直接的关系机制。本文基于近年对此关系机制的相关理论研究,并藉助新近研究的“分子污染低温凝结效应设备”,就我国飞行器型号设计密切相关的分子凝结与凝结表面温度的关系机制进行了四个月余的试验研究,取得了相关的二千余个数据。在此基础上,结合相关的理论对数据进行了拟合和分析,得到了分子凝结与凝结表面温度广泛遵循的一般关系——指数关系。对型号设计而言,此结论具有重要的参考价值。 相似文献
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A new method of determining the absorptivity and emissivity of surfaces with the use of a radiation flux of variable intensity is described. It is expedient to use this method in order to control the variations of integral optical coefficients of temperature-controlling coatings in the course of a long-term spacecraft flight. The method is developed on the basis of solving the inverse problem for a mathematical model of thermal balance for a thin metal plate. The stability of the algorithm of processing the results of measurements is analyzed for various levels of random errors. Some recommendations concerning the technical implementation of the method in the laboratory and space conditions are given. The method suggested has a number of advantages in comparison with methods used before, especially if it is used in space conditions. The main advantage is the possibility of varying the radiation flux incident on the surface of a specimen under study from an external source according to any smooth law. 相似文献
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V. V. Afonin 《Cosmic Research》2004,42(1):32-38
The problem of maintenance of the equipotentiality of spacecraft surfaces is considered. The method under examination is the use of the conductive thermal-vacuum multilayer blanket (CMLB), whose outer surface represents a fabric woven of threads of glass fiber type with interwoven metal threads. The process of spacecraft potential formation and methods of the potential calculation are described, and the results of such a calculation for the illuminated and shadowed parts of spacecraft surfaces in some characteristic near-Earth plasma environments are presented. The CMLB model is described, and the potential distribution near the CMLB surface is calculated. The conclusion was drawn that the conductive thermal-vacuum multilayer blanket used in some cases on Russian spacecraft does not ensure the equipotentiality of spacecraft surfaces, and in the case of using CMLB, the differential spacecraft charging in outer regions of the Earth's magnetosphere may reach a dangerous level for onboard electronic systems. In spite of the fact that CMLB guards against large-scale powerful discharges, one cannot exclude discharges completely, what may result in broadband noise enhancement and cause onboard systems failures. 相似文献
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A system of two-degree-of-freedom force gyroscopes (gyrodynes) is considered to be used for spacecraft attitude control. Possible values of its total angular momentum form some finite region P in the frame of reference rigidly connected with the spacecraft. Near the boundary of this region and singular surfaces located inside it the control of the angular momentum is complicated or impossible. The program angular momentum of the gyrodynes, realizing the law of variation of the spacecraft orientation, should lie inside P and outside some singular surfaces, and due to this fact the boundary and internal singular surfaces should be studied. This work is dedicated to the numerical construction of region P and its internal singular surfaces by the method of parameter continuation. Using the results by E.N. Tokar’ we formalize sufficient conditions which in some cases allow one to determine the type of the singular surface. As an example, a system of six gyrodynes is considered, for which the regions of variations of the intrinsic angular momentum and singular surfaces are constructed. The possibilities of the system are demonstrated for the case when one gyrodyne fails. 相似文献
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M. V. Zakhvatkin Yu. N. Ponomarev V. A. Stepan’yants A. G. Tuchin G. S. Zaslavskiy 《Cosmic Research》2014,52(5):342-352
A developed method of determination of orbital parameters allows one to estimate, along with orbit elements, some additional parameters that characterize solar radiation pressure and perturbing accelerations due to unloadings of reactiion wheels. A parameterized model of perturbing action of solar radiation pressure on the spacecraft motion is described (this model takes into account the shape, reflecting properties of surfaces, and spacecraft attitude). Some orbit determination results are presented obtained by the joint processing of radio measurements of slant range and Doppler, laser range measurements used to calibrate the radio measurements, optical observations of right ascension and declination, and telemetry data on spacecraft thrusters’ firings during an unloading of reaction wheels. 相似文献
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A CubeSat mission to study the impact of flow incidence angle, surface material and surface roughness on gas–surface interactions on spacecraft in low Earth orbits has been designed. To accomplish this scientific goal the CubeSat deploys a variable geometry aerofoil capable of exposing different surfaces to the flow at different incident angles. By using the on-board GPS measurements and an orbit determination technique the drag experienced by the CubeSat can be estimated. The CubeSat has been designed to be part of the QB50 mission, and hence it carries a sensor that can take in-situ measurements of the atmosphere. This is then used to estimate the atmospheric density and hence to extract information on the drag coefficient. To minimise any bias present in the measurement chain a differential approach is used. Therefore no absolute drag coefficients are estimated, instead, ratios of drag coefficients are computed. This allows direct comparisons of the drag coefficients of different materials, different surface roughness or different incident angles. Simulations indicate that this CubeSat mission will be able to obtain drag coefficient ratios with an uncertainty level of less than 5%. 相似文献
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Sample return is an essential component of solar system exploration. Samples provide a unique data set that is critical for understanding formation and evolution of our solar system. This uniqueness is based on the scale of observations, precision of measurements, the ability to modify experiments as logic and technology dictate, and the ability to use instruments free of the constraints on mass, power, reliability, and data rate of flight instruments. Advances in analytical capabilities in recent years enable fundamental measurements to be made on extremely small samples, greatly reducing mass constraints on robotic sample return spacecraft. Sample studies provide irreplaceable ground truth for remotely-sensed data on planetary surfaces and fit within a variety of architectures for human exploration of the solar system. 相似文献
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W. Winkler 《Acta Astronautica》1983,10(4):189-205
The Sun mission of the German-US-sunprobe HELIOS-A, the first man-made satellite which approaches the Sun as close as 0.3 AU, covers now more than half a sun-cycle.Therefore the long term behaviour of surface materials which usually are applied on spacecraft as aluminized Teflon, Second-Surface-Mirrors (SSM) made from fused silica and Solar Cells (SC), under extreme stresses and combined loads, shall be evaluated.Based upon the temperature readings of the house-keeping data from HELIOS, a semi-quantitative relationship between the different loads (e.g. radiation, solar wind) and the spacecraft response was established using the results of the first four orbits.From these temperatures, α(t, T)-values were calculated. The related changes of the absorptance values are interpreted in terms of degradation and contamination of the surface materials concerned. Here, not only physico-chemical considerations and models but also the results from thorough ground tests are used to describe the experienced effects by a semi-theoretical function.Taking the derived α(t, T)-values, temperatures are calculated and a long term prediction for 20 orbits is made. The predicted temperature values are compared with the housekeeping data of 15 orbits, i.e. until 1982; the deviations are explained and the validity of the chosen model discussed. 相似文献
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The choice of critical values for developing electron-stimulated discharges (ESDs) in insulator covers of spacecraft is substantiated. In addition, it is found that the error in determination of an estimated potential of the open surface of the quartz film 150 m thick, related to changing the lower limit of integration of the bi-Maxwellian spectrum of electrons for the case of positively charged open dielectric surface relative to the substrate, was less than 12%. 相似文献
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A. A. Chirov 《Cosmic Research》2014,52(3):235-243
Materials on experimental studies to determine the effect of thin condensate films of cesium (used as a model working medium for electric propulsion engines and some spacecraft power sources) on integral optical coefficients of spacecraft thermal control coatings are presented. A technique modified by the author and employing the regular thermal regime of a thin metal plate is used. Measurement results demonstrate that films with thicknesses of 100–1000 Å can seriously degrade the integral optical coefficients of thermal control coatings and thus disturb the heat balance of some spacecraft systems. 相似文献
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航天器总装过程的质量控制方法 总被引:1,自引:1,他引:0
为实现航天器零缺陷的质量管理目标,文章在梳理出导致航天器总装过程质量异常的工艺、操作、设备及材料等方面原因和总装生产流程优化的基础上,应用风险控制理论对各单步工序进行风险点识别和评估,使用多品种、小批量质量统计方法进行过程质量闭环控制,使得航天器总装生产质量得以有效提高。 相似文献
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月球表面热环境测量技术调研分析 总被引:1,自引:1,他引:0
月面热环境探测是我国探月工程中的一项必要工作,具有重要的工程和科学意义。文章从工程角度确定了月面热环境测量的主要物理参数,分析了现阶段我国探月工程中实现月面热环境测量的技术条件和要求;对国内外有关材料热物性测量技术进行了综合调研,了解了国内外关于开展行星表面热环境探测的技术及应用现状;在结合我国航天测量技术的基础上对月面热环境测量所涉及的关键技术进行了分析,并初步勾勒出我国探月工程中月面热环境测量装置的指标、任务和实现方案。 相似文献