空间环境防护型薄膜评述

空间环境的复杂性和特殊性对航天器的使用寿命和性能造成严重威胁。提高航天器表面材料抵抗空间环境作用的能力一直是空间技术开发工作的重点关注问题。目前,表面薄膜技术已被广泛应用在航天器热控涂层、光学器件等方面的空间防护。针对航天器在空间原子氧环境、空间等离子体环境、空间污染环境中的空间环境效应问题,详细介绍了相应空间环境防护薄膜的研究现状及主要制备方法。在地面空间模拟实验和飞行试验成果的基础上,对这些防护薄膜的空间环境适应性进行了分析,总结了空间环境防护薄膜应具备的综合性能,提出复杂型薄膜的开发和空间环境防护薄膜标准评价体系的建立是今后研究的重点。     

Microelectromechanical devices for satellite thermal control

Future space missions will include constellations of spacecraft, including nano- and picosatellites, where adaptive thermal control systems will be needed that fit the constraints of space applications with limited power and mass budgets. A microelectromechanical systems (MEMS) solution has been developed that will vary the emissivity on the surface of the small satellite radiator. The system is based on louver thermal controllers, where panels are mechanically positioned to modulate the effective radiator surface area. This system consists of MEMS arrays of gold-coated sliding shutters, fabricated with the Sandia ultraplanar, multilevel MEMS technology fabrication process, which utilizes multilayer polycrystalline silicon surface micromachining. The shutters can be operated independently to allow digital control of the effective emissivity. This first demonstrator technology is limited in the possible emittance range to a 40% change. Early prototypes of MEMS louvers that open away from the structure have shown the capability of a much wider dynamic range. The first generation of this active thermal management system will be demonstrated on NASA's New Millennium Program ST-5 spacecraft. With the opportunity to validate the MEMS thermal control technology in space on ST-5, lightweight, low-power MEMS radiators offer a possibility for flexible thermal control on future nanosatellites.     

3D Graphene‐Infused Polyimide with Enhanced Electrothermal Performance for Long‐Term Flexible Space Applications

Polyimides (PIs) have been praised for their high thermal stability, high modulus of elasticity and tensile strength, ease of fabrication, and moldability. They are currently the standard choice for both substrates for flexible electronics and space shielding, as they render high temperature and UV stability and toughness. However, their poor thermal conductivity and completely electrically insulating characteristics have caused other limitations, such as thermal management challenges for flexible high‐power electronics and spacecraft electrostatic charging. In order to target these issues, a hybrid of PI with 3D‐graphene (3D‐C), 3D‐C/PI, is developed here. This composite renders extraordinary enhancements of thermal conductivity (one order of magnitude) and electrical conductivity (10 orders of magnitude). It withstands and keeps a stable performance throughout various bending and thermal cycles, as well as the oxidative and aggressive environment of ground‐based, simulated space environments. This makes this new hybrid film a suitable material for flexible space applications.     

离子推进器热特性测试与分析

对离子推进器工作状态的热特性进行了测试与分析。测试分析结果表明：离子推进器工作时产生的热量主要以热传导和热辐射向周围环境传递,通过安装环传导到航天器的热量较少,不会对航天器产生影响。热辐射主要向空间辐射,不会对航天器造成热影响。     

NASA at the crossroad

During the quarter-century that Technology in Society has been published, great strides have been made in planetary exploration and space flight in near-Earth orbit, both with robotic spacecraft and with piloted space vehicles. Robotic spacecraft have visited every planet in the solar system and several hundred people have been in space learning how to live and work in that environment. The International Space Station is well on the way to completion and the Earth-orbiting “Great Observatories” have unlocked many of the secrets of the universe. There have also been great difficulties. Management failures have caused delays and cost increases in several major programs. Two of the five space shuttles, Columbia and Challenger, have been lost, at the cost of 14 human lives. NASA has not found a focus for its efforts around which the resources to operate a successful space exploration enterprise can be mobilized. Suggestions to remedy NASA’s management and programmatic problems are made in this paper.     

空间材料的原子氧侵蚀理论和预测模型

低地轨道环境中的原子氧对航天器材料的侵蚀导致材料的性能变坏甚至失效，原子氧的侵蚀机理和防护技术是当前空间环境效应研究的热点．在对原子氧效应机理已有理解的基础上，准确预测空间材料在低地轨道环境中由原子氧引起的侵蚀效应，可对设计者在工程选材和飞行器设计提供帮助。本文综述了近年来发展的原子氧与空间材料相互作用的理论模型和侵蚀速率预测模型，并对各种模型进行了分析，也指出了关于原子氧效应的研究重点．     

中国航天器真空技术的进展（一）

围绕着中国航天器真空技术在航天领域中的应用问题,综合地介绍了其技术的发展,重点突出了中国极高真空技术的发展.提出了"分子真空寿命"这一新的物理量,并以此概念推导出测量气体分子热适应系数的方法.指出了在超高和极高真空条件下压力失去了原有的物理意义,引入了"有效压力"、"入射率"、"静压"、"动压"等新概念.探索了在空间条件下真空测量中的方向性效应和理论计算与实际测量偏离问题的特殊性和复杂性.介绍了利用分子沉技术研制的极高真空装置获得了10-11Pa极限真空度,介绍了中国已建立的航天器模拟设备的现状、性能指标和主要用途.概述了中国空间材料的真空效应研究现状,指出了空间材料、活动部件的冷焊及航天器敏感表面分子污染对航天器的长寿命和可靠性的影响.展望了中国航天器真空技术的发展.     

中国航天器真空技术的进展(二)

围绕着中国航天器真空技术在航天领域中的应用问题 ,综合地介绍了其技术的发展 ,重点突出了中国极高真空技术的发展。提出了“分子真空寿命”这一新的物理量 ,并以此概念推导出测量气体分子热适应系数的方法。指出了在超高和极高真空条件下压力失去了原有的物理意义 ,引入了“有效压力”、“入射率”、“静压”、“动压”等新概念。探索了在空间条件下真空测量中的方向性效应和理论计算与实际测量偏离问题的特殊性和复杂性。介绍了利用分子沉技术研制的极高真空装置可获得 10 -11Pa极限真空度 ,介绍了中国已建立的航天器模拟设备的现状、性能指标和主要用途。概述了中国空间材料的真空效应研究现状 ,并指出空间材料、活动部件的冷焊及航天器敏感表面分子污染对航天器的长寿命和可靠性的影响。展望了中国航天器真空技术的发展。     

空间低能电子探测技术综述

空间低能电子是空间辐射环境的重要组成部分,对航天器的安全可靠运行具有重要的影响作用。详细介绍了国内外探测空间低能电子的活动、使用的相关探测器及其技术方法,在此基础上提出了进一步探测空间低能电子的可行性技术和方法,以促进我国空间低能电子探测的发展。     

空间粉尘环境因素对航天器材料损伤的研究动态

简要阐述空间粉尘的定义、来源、空间分布状况及与航天器发生碰撞概率,并从空间粉尘与航天器外表材料交互作用角度,综述空间粉尘环境因素对热控涂层、高温热管、光学材料、太阳电池和绝缘隔热层影响的国内外研究动态.地面模拟试验表明,空间粉尘高速撞击下对这些材料与元器件会产生不同程度的损伤.     

Fault-tolerant spacecraft attitude control system

Spacecraft perform a variety of useful tasks in our day-to-day life. These are such that spacecraft need to function properly without interruptions for 7 to 15 years in space without any maintenance. Though most spacecraft have redundant systems to serve as back-ups in case of failures, they greatly depend on human assistance through ground stations for failure analysis, remedial actions and redundancy management, resulting in itnerruption in services rendered. There is, therefore, need for a fault-tolerant system that functions despite failures and takes remedial action, without human assistance/intervention, autonomously on board the spacecraft. Commonly used techniques for fault-tolerance in computers cannot be directly used for fault-tolerance in sensors and actuators of a closed loop control system. Further, for space applications fault-tolerance needs to be achieved without much penalty in weight and computational requirements. This paper describes briefly the attitude control system (acs) of a spacecraft and highlights the essential features of a fault-tolerant control system. Schemes for fault tolerance in sensors and actuators are presented with an analysis on various failure modes and their effects. Newly developed fault-detection, identification and reconfiguration (fdir) algorithms for various elements ofacs are described in detail. Also an optimum symmetrically skewed configuration for the attitude reference system using dynamically tuned gyros is developed. Some of the schemes have already been used in Indian Spacecraft. As future Indian space missions will directly cater to various applications on an operational basis, the ultimate objective is to have a totally fault-tolerant ‘intelligent’ autonomous spacecraft.     

Electron microscope observations of impact crater debris amongst contaminating participates on materials surfaces exposed in space in low-Earth orbit

Debris particles extracted from a small sampling region on the leading edge of the Long Duration Exposure Facility (LDEF) spacecraft have been examined by analytical transmission electron microscopy and the elemental frequency observed by energy-dispersive X-ray spectrometry and compared with upper atmosphere (Earth) particle elemental frequency and the average elemental compositions of interplanetary dust particles. A much broader elemental distribution was observed for the exposed spacecraft surface debris milieu. Numerous metal microfragment analyses, particularly aluminium and stainless steel, were compared with scanning electron microscope observations of impact crater features, and the corresponding elemental spectra on selected LDEF aluminium tray clamps and stainless steel bolts. The compositions and melt features for these impact craters and ejecta have been shown to be consistent with microcrystalline debris fragments in the case of aluminium, and these observations suggest an ever changing debris milieu on exposed surfaces for space craft and space system materials.     

微流星及空间碎片高速撞击航天器风险度分析

给出了微流星及空间碎片高速撞击航天器风险分析的方法 ,并采用风险分析软件 ,以柱状近地轨道航天器为例 ,对不同防护结构方案、航天器的飞行姿态、防护屏的厚度以及航天器的运行时间等因素对航天器不发生穿孔损伤的影响进行了分析 ,给出了分析的结果     

LEO大型载人航天器主动电位控制技术进展

LEO大型载人航天器主动电位控制技术可以有效的防护空间等离子体充放电效应对于航天器造成的安全隐患,确保航天员出舱和航天器空间对接作业的顺利完成。通过研究LEO大型载人航天器与空间等离子体的相互作用,从原理上认识空间等离子体对于航天器的危害程度。分析回顾国外主动电位控制技术在LEO大型载人航天器上的成功应用及发展情况,得出启示和初步的主动电位控制系统设计设想。对比国内外主动电位控制领域的核心技术,对主动电位控制技术的发展和应用提出了建议。     

空间辐射环境诱发航天器故障或异常分析

空间辐射环境是诱发航天器系统故障或异常的主要因素之一。调研收集了国外航天器在轨的故障信息,总结分析了航天器所出现的各种故障、分析经验和对策,提出了我国航天器的在轨运行的一些具体建议,促进空间环境研究与在轨运行管理的紧密结合,提高空间环境引起航天器在轨异常的原因分析与判断的水平。     

Atomic oxygen effects on POSS polyimides in low earth orbit

Kapton polyimde is extensively used in solar arrays, spacecraft thermal blankets, and space inflatable structures. Upon exposure to atomic oxygen in low Earth orbit (LEO), Kapton is severely eroded. An effective approach to prevent this erosion is to incorporate polyhedral oligomeric silsesquioxane (POSS) into the polyimide matrix by copolymerizing POSS monomers with the polyimide precursor. The copolymerization of POSS provides Si and O in the polymer matrix on the nano level. During exposure of POSS polyimide to atomic oxygen, organic material is degraded, and a silica passivation layer is formed. This silica layer protects the underlying polymer from further degradation. Laboratory and space-flight experiments have shown that POSS polyimides are highly resistant to atomic-oxygen attack, with erosion yields that may be as little as 1% those of Kapton. The results of all the studies indicate that POSS polyimide would be a space-survivable replacement for Kapton on spacecraft that operate in the LEO environment.     

Titanium–aluminum–nitride coatings for satellite temperature control

Intense solar irradiation, radiative cooling to outer space, and internal heat generation determine the equilibrium temperature of a spacecraft. The balance between the solar absorption and thermal emittance of the surface is therefore crucial, in particular for autonomous parts directly exposed to the solar radiation and thermally insulated from the main thermal mass of the spacecraft. The material composition but also the coating thickness are found to influence the equilibrium temperature of an object in space. In this paper we report on a systematic search for a suitable composition and thickness of Ti_xAl_yN_z alloy coatings prepared by reactive, unbalanced magnetron sputtering from targets consisting of differently sized titanium and aluminum sectors. The films were deposited on glass, glassy carbon, aluminum sheet metal, and on sputtered aluminum and Ti_xAl_(1−x) films on glass. The stoichiometry and sheet resistance of the films was determined with Rutherford backscattering and four-point probe measurements respectively. Reflectance spectra for the visible and infrared spectral ranges were used to obtain average solar absorptance and thermal emittance values used in model calculations of the equilibrium temperature. Neglecting internal heat contributions, the lowest calculated equilibrium temperature in orbit around the Earth, 32.5°C, was obtained for a 505-nm-thick Ti_0.14Al_0.47N_0.40-film.     

5A06铝合金单层板超高速撞击弹道极限分析

日益增长的空间碎片对在轨航天器的安全运行构成了严重威胁,毫米级空间碎片的防护已成为航天器结构设计必须考虑的问题之一.航天器的蒙皮是抵御空间碎片超高速撞击的最基本防护结构.采用数值仿真并结合试验验证的方法,对5 mm厚5A06铝合金单层板承受2A12铝合金球形弹丸正撞击下的弹道极限进行了研究.研究表明,在验证实验速度范围内,数值仿真结果与实验结果吻合良好;使用数值仿真对实验速度以上的区间进行拓展研究,获得了其弹道极限曲线和弹道极限方程;数值仿真和实验结果与已有经验方程对比表明,经验方程与具体材料的弹道极限有较大偏差,因此,应具体问题具体分析.     

Investigation of radiation doses in open space using TLD detectors

The low energy component of the cosmic radiation field is strongly modified by the shielding of the spacecraft and it is time and location dependent. Thermoluminescent lithium fluoride detectors have been applied to determine the radiation doses inside the ESA-Facility BIOPAN. The BIOPAN facility was mounted outside and launched on a Foton spacecraft and opened to space to allow exposure of several experiments to open space. Standard TLD-600. TLD-700 chips, two layers MTS-Ns sintered pellets with different effective thickness of the sensitive layer and MTS-N of different thickness have been exposed with different shielding thicknesses in front of them. The measured TL signal in the 0.1 mm thick detector just shielded by an aluminised Kapton foil of 25 microm thickness in front yielded a dose of 29.8 Gy (calibrated with 137Cs gamma rays) for an exposure time of 12.7 days: after 2.5 g.cm(-2) shielding the doses dropped to 3 mGy. The monitoring of radiation doses and its depth dose distribution outside the spacecraft are of great interest for radiation protection of astronauts working in open space. The knowledge of depth-dose distribution is a prerequisite to determine the organ doses an astronaut will receive during an extravehicular activity (EVA). The BIOPAN experiments are to be continued in the future.     

空间粉尘对航天器高温热管撞击效应的研究

本文利用爆炸式和电磁式加速器模拟研究空间粉尘粒子对高温热管的碰撞损伤效应.研究表明,微米级粉尘粒子难以击穿航天器高温热管管壁,但对热管表面的热控涂层光学性能变化有较大影响.亚毫米级粉尘粒子取决于速度的不同,高温热管由表面热控涂层光学性能下降一直到被击穿发生载热体的泄漏现象.针对高温热管在高速粉尘粒子撞击下的运行密封性和辐射功率等问题进行了试验研究及理论分析.测量结果表明,高温热管在工作温度T=900K时,被粉尘粒子击穿的速度由常温下的5.3 km/s降为4.8 km/s.