中国通信卫星的回顾与展望

一、引言 1945年,英国人克拉克曾在一篇文章中大胆地提出了利用3颗地球静止轨道人造卫星进行准全球通信的设想。当时人类还未步入宇航时代,这一有关应用卫星的设想无疑带有浓厚的科学幻想色彩。但到了50多年后的今天,它不但变成了现实,而且发挥得淋漓尽致:通信卫星作为空间技术和无线电通信技术的美妙结合,得到了飞速的发展,成为各种卫星中最早投入商业市场,效益最为显著的一种。通信卫星具有通信距离远,覆盖面积大,信道质量高,通信容量大的优点,已广泛应用于国际、国内或区域通信、军用通信、海事通信、电视广播以及航天器的跟踪和数据中继…     

加强工艺标准化提高工艺技术水平

工艺标准化是工艺技术工作的重要内容,是搞好科研、生产工作的重要环节和有效手段。本文着重介绍了在贯彻和制定工艺标准过程中的一些作法和原则,从而使工艺技术水平不断提高,产品质量控制得到可靠的保证。     

中国军转民的实践与发展

当今世界，和平与发展成为不可阻挡的潮流。军转民正在成为世界各国争取和平与裁军活动的重要组成部分，也是许多国家重视和关注的一个重要课题。军转民的基本实质是各国从战争或冷战环境转向和平环境的条件下，调整国防战略，削减防务预算，压缩军队和国防规模，调整和改革国防工业，将原先只用于国防的国家资源，重新配置，优化组合，转向为国民经济建设服务。军转民不仅关系到国家的国防、经济、科技发展战略、产业政策、劳动力转移等诸方面，而且关系到巩固国际军控与裁军成果，人类社会的进步与稳定，世界的和平与发展。一、中国军转民…     

国外汽车业是如何做好供应商质量保证工作的

介绍了国外汽车业对其零部件供应商的现代化管理方式，并紧紧围绕对供应商质量保证体系程序化的运作方式，分析了如何才能使零件质量不断完善和提高，从而促进汽车业的健康发展。     

国防科技工业质量工作长效机制的总体框架研究与思考

以当前国防科技工业质量形势分析为出发点，分析了建立质量工作长效机制的必要性和紧迫性，研究提出了质量工作长效机制的总体目标，基本内涵，基本要求和建设途径。     

处于变革中的欧洲导弹工业

处于变革中的欧洲导弹工业近来，欧洲的导弹工业格局发生了重大变化。面对美国导弹工业的激烈竞争和国防预算的日益削减，法国马特拉公司和英国宇航公司已着手合并其导弹业务，以减少欧洲内部的对抗与竞争，更好地利用研究和发展费用，占领更大的市场。但是，两家公司各自...     

以色列的战术导弹工业

本文评述了以色列战术导弹工业的发展历史、现况、管理体制与方针政策,介绍了其主要企业、机构及主要战术导弹的性能、产量和产值。     

军民结合是国防科技工业发展之路

和平与发展是当今世界的主流。知识经济的兴起,环境与资源危机以及“可持续发展”战略促使高技术和信息产业的高速发展。为适应全球经济一体化,促进国防工业高技术市场的双向流动,已成为发展趋势。因此,研究国防工业军转民发展具有重大的现实意义。 我院成立于1961年。在40年的发展历程中,塑造了一支高素质的职工队伍,积累了雄厚的技术基础,拥有较强的科研生产和技术创新能力。近20年来,我院根据国民经济发展需要,转变观念,改革管理体制和经营机制,在军转民道路上迈出了坚实的步伐,取得了一定的经验。一、民品发展回顾 改革开放以来,我院确…     

航天科技集团总经理张庆伟谈深化航天质量管理

航天科技工业正在进入一个新的战略发展机遇期。在“十一五”发展规划中,航天科技工业是国家及国防科技工业战略性发展的重点。航天科技集团公司制定了铸造国际一流宇航公司的战略目标。新体制、新形势和新任务对集团公司质量工作提出了更高的要求。集团公司质量工作面临着新挑     

导弹技术遍及全世界

目前,导弹技术已迅速发展到世界各地。许多国家已有能力创办本国的武器和宇航工业,几年前少数国家拥有导弹技术的垄断局面已被打破。本文着重介绍了亚洲的巴基斯坦、欧洲各国以及世界其它地区导弹技术的发展和合作现状。     

卫星结构中的非金属材料

介绍了各种复合材料、胶粘剂、高分子材料和工业陶瓷等非金属材料的性能及其在卫星结构中的应用情况。强调了非金属材料在提高卫星性能、减轻卫星结构质量，以及增大卫星有效栽荷方面的作用。最后指出了卫星结构材料高性能、多功能、复合化、智能化、低成本以及高环境相容性的发展趋势。     

Modelling of Ejecta as a Space Debris Source

When a micro-debris or a micrometeoroid impacts a spacecraft surface, a large number of secondary particles, called ejecta, are produced. These particles can contribute to a modification of the debris environment: either locally by the occurrence of secondary impacts on the components of complex and large space structures, or at great distance by the formation of a population of small orbital debris. This paper describes firstly, the ejecta overall production, and secondly, the lifetime and the orbital evolution of the particles. Finally the repartition of ejecta in LEO is computed. Some results describing the population as a function of size and altitude are presented.     

基于接触理论的一类带锁定机构的间隙铰链分析模型研究

重点研究一类在我国航天器上得到广泛应用的带有锁定机构的间隙铰链，基于接触理论建立了该类型间隙铰链的分析模型。首先，将铰链零件间的接触力假设为单向的非线性弹簧，并将铰链简化为由非线性弹簧组约束的摆；然后。将展开扭簧假设为线性力矩弹簧，得到包含间隙影响的铰链的力矩-转角关系曲线。通过仿真分析和试验验证，认为铰链的力矩转角关系曲线是分段光滑的。是铰链结构尺寸、零件间隙以及材料特性的函数。呈现出明显的非线性特征。     

磁阻尼对火星探测器降落过程的动力学效应

火星稀薄的大气使得探测器再入火星时难以获得足够的减速阻力,为此,文章提出利用磁阻尼增加阻力的概念。高速再入的探测器与火星大气剧烈摩擦产生等离子体,利用探测器上的磁偶极场将等离子体捕获,同时在火星大气中形成一个“磁泡”区域并跟随探测器。由“磁泡”束缚的等离子体与来流的中性气体发生碰撞获得动量,又通过磁场作用将动量传递给探测器,从而使探测器获得一定的减速阻力。在磁阻尼的作用下,在同样的开伞高度探测器速度可降至更低,而低速开伞又可提高阻力伞打开的可靠性。因此,磁阻尼不仅可加快降低再入速度,而且还有助于提高探测器着陆火星的安全性。     

What makes a planet habitable, and how to search for habitable planets in other solar systems

The availability of liquid water is the most important factor that makes a planet habitable, because water is a very effective polar molecule and hence an excellent solvent and facilitator for the complex chemistry of life. Its presence presupposes a planet with a significant mass that guarantees the presence of a substantial atmosphere, and a reasonable spinning rate to avoid overheating. It also implies that the planet is at moderate distances from its central star, a range that is called the Ecosphere or the Habitable Zone. Since the evolution of life to high intelligence seems to take billions of years, it requires also that the central star must be neither too massive, that will produce a lot of lethal UV radiation and will have too short a life-span to allow life to evolve, nor of very small mass which will be producing too feeble a radiation to sustain life. The detection of free Oxygen in the atmosphere of a planet is a very strong evidence for the presence of life, because Oxygen is highly reactive and would rapidly disappear by combining with other elements, unless it is continuously replenished by life as the by-product of the process of photosynthesis that builds food for life (sugars) from CO2 and H2O.     

The development of a Russian communication satellite of small class, operating in the geostationary and high-elliptical orbits

In 1994–1995 Lavochkin Association (Russia) together with the other enterprises in accordance with technical requirements of the Russian Space agency, developed a new Russian communication satellite of a small class that will operate in both the geostationary (GSO) and high-elliptical (HEO) orbits. This satellite may be injected into operational orbits using a SOYUZ-2 launch vehicle (LV) and a FREGAT upper stage (US) from Plesetsk and Baykonur space launch sites (SLS).The main reason for creating such a satellite was to decrease the cost of the support and development of the Russian communication geostationary satellites group.Russian satellites Horizont, Express, Ekran and Gals, which operate in GSO, are the basis of the space segment for communications, radio and TV broadcasting. All of these satellites are injected into GSO by the PROTON LV. PROTON is a launch vehicle of a heavy class. The use of a middle class LV instead of a heavy class will allow to reduce considerably the launch cost. The change of a heavy class LV to a LV of middle class determined one economic reason for this project. Besides, the opportunity to launch S/C into GSO from Russian Plesetsk SLS increases the independence of Russia in the domain of space communications, despite the presence of the contract with Kazachstan about the rent of Baykonur SLS. Finally, use of small satellites with a rather small number of transponders is more effective than the use of big satellites. It will allow also to increase a satellite group (by the launch of additional satellites) precisely in accordance to the development of the ground segment.     

The development of a Russian communication satellite of small class, operating in the geostationary and high-elliptical orbits

In 1994-1995 Lavochkin Association (Russia) together with the other enterprises in accordance with technical requirements of the Russian Space agency, developed a new Russian communication satellite of a small class that will operate in both the geostationary (GSO) and high-elliptical (HEO) orbits. This satellite may be injected into operational orbits using a SOYUZ-2 launch vehicle (LV) and a FREGAT upper stage (US) from Plesetsk and Baykonur space launch sites (SLS).The main reason for creating such a satellite was to decrease the cost of the support and development of the Russian communication geostationary satellites group.Russian satellites Horizont, Express, Ekran and Gals, which operate in GSO, are the basis of the space segment for communications, radio and TV broadcasting. All of these satellites are injected into GSO by the PROTON LV. PROTON is a launch vehicle of a heavy class. The use of a middle class LV instead of a heavy class will allow to reduce considerably the launch cost. The change of a heavy class LV to a LV of middle class determined one economic reason for this project. Besides, the opportunity to launch S/C into GSO from Russian Plesetsk SLS increases the independence of Russia in the domain of space communications, despite the presence of the contract with Kazachstan about the rent of Baykonur SLS. Finally, use of small satellites with a rather small number of transponders is more effective than the use of big satellites. It will allow also to increase a satellite group (by the launch of additional satellites) precisely in accordance to the development of the ground segment.     

Detour Strategies in Humans: Testing the Predictions of a Cognitive Map Model

In this paper, we test the predictions of a model developed by Voicu and Schmajuk (2002) in a paradigm that consists of placing an obstacle on a path between a start place and a goal after that path has been experienced by human participants several times. The model predicts that more experience with the path increases the likelihood of the participants performing a detour, e.g., circumventing the obstacle and resuming the original path, and decreases the probability of taking a shortcut to the goal. This prediction is tested in humans in a computed-simulated virtual environment. The experimental results agree with the prediction of the model for the case in which subjects have a limited view of the environment. In the case where they have an unrestricted view of the environment, they are more likely to move directly to the goal irrespective of the experience with the path between the two places.     

Strategy for capturing of a tumbling space debris

In general space debris objects do not possess much convenient features and are non-cooperative. In such cases, since the conditions for capture are not favorable, tracking errors will lead to loading, and momentum transfer will occur during the capture process.In most cases, detailed mass and inertial characteristics of the target are unknown, either because design details are unavailable or due to changes as a result of damage sustained when failure occurred or gradual degradation over the years, and this makes impedance matching of the capture arm force control system difficult.This led to us to devise a “joint virtual depth control” algorithm for robot arm control, which brakes the rotation of a target with unknown inertia. This paper deals with a removal work strategy and control method for capturing and braking a tumbling, non-cooperative target space debris.We propose a new brush type contactor as end-effecter of a robot arm for reducing the rotational rate of the target debris. As a means for relieving the loads generated during target tapping, in addition to joint compliance control we propose a new control method that controls the arm tip force according to a contact force profile.     

A low-thrust transfer between the Earth–Moon and Sun–Earth systems based on invariant manifolds

A low-energy, low-thrust transfer between two halo orbits associated with two coupled three-body systems is studied in this paper. The transfer is composed of a ballistic departure, a ballistic insertion and a powered phase using low-thrust propulsion to connect these two trajectories. The ballistic departure and insertion are computed by constructing the unstable and stable invariant manifolds of the corresponding halo orbits, and a complete low-energy transfer based on the patched invariant manifolds is optimized using the particle swarm optimization (PSO) algorithm on the criterion of smallest velocity discontinuity and limited position discontinuity (less than 1 km). Then, the result is expropriated as the boundary conditions for the subsequent low-thrust trajectory design. The fuel-optimal problem is formulated using the calculus of variations and Pontryagin's Maximum Principle in a complete four-body dynamical environment. Then, a typical bang–bang control is derived and solved using the indirect method combined with a homotopic technique. The contributions of the present work mainly consist of two points. Firstly, the global search method proposed in this paper is simply handled using the PSO algorithm, a number of feasible solutions in a fairly wide range can be delivered without a priori or perfect knowledge of the transfers. Secondly, the indirect optimization method is used in the low-thrust trajectory design and the derivations of the first-order necessary conditions are simplified with a modified controlled, restricted four-body model.