Characteristics of Polyimide Debris Clouds Produced by Hypervelocity Impact

Polyimide is a typical complex high-molecular polymer of imide monomers,which is widely used in the manufacture of parts for aerospace engineering.The hypervelocity impacts between the spacecraft and orbital debris can induce great damage to the spacecraft.In order to improve the safety of spacecraft,the characteristics of polyimide debris clouds produced by hypervelocity impact should be studied.Firstly,a MieGrüneisen equation of state based on the shock adiabat for polyimide,which describes the mechanical behavior in the numerical simulation,was obtained from hypervelocity impact experiments,then a 3-dimentional smoothed particle hydrodynamics program was compiled to numerically simulate the hypervelocity impact between aluminum projectiles(orbital debris)and polyimide targets with different impact velocities(3 km/s,5 km/s,8 km/s)and angles(0°,30°,45°,60°),finally typical shapes of debris clouds produced in different impact velocities and angles were collected from simulation results,the characteristics of which were systemically discussed.     

航天器微流星体及空间碎片防护结构性能分析

微流星体及空间碎片是航天器的公认威胁，微流星体及空间碎片的高速撞击能导致航天器严重的损伤和灾难性的失效，防护结构设计是航天器设计的一个重要问题，在综合分析国际上已采用和研究航天器微流星体系及空间碎片防护结构防护性能预报方程的基础上，给出了不同防护材料和结构形式防护在超高速撞击下的撞出极限曲线，讨论了防护结构参数变化对防护性能的影响，通过曲线分析得出各防护结构在第一门槛值速度区间的防护性能是比较低的，正撞击损伤更严重，填充防护结构的性能优于其他防护结构。     

SPH Simulation of Hypervelocity Impacts

The smooth particle hydrodynamics (SPH) method is a very important tool to resolve hypervelocity problems. The basic principle of SPH method and how to generate a proper SPH mesh is described. The results of SPH simulations of hypervelocity impacts on thin or thick aluminum plates, performed by using the LS-DYNA 3D computer code, are also reported. The forming process and composition of the debris clouds simulated are identical with the experiment results. It can be concluded that the simulation is reasonable and SPH method is an ideal method for hypervelocity impact simulation.     

Experimental Study of Hypervelocity Impact on Multi-Shock Structure

Hyperveloeity impact tests on multi-shock shields are carried out in order to develop space structures against space debris impacts. Sheets of LY12 aluminum were used as bumpers. The total thickness of shield structure, which consists of several sheets with various thickness, is 3.0 mm or 2.0 mm. Results of the tests show that the type 0.5 mm 0.5 mm 0.5 mm 0.5 mm is a better choice of spacecraft shield structure.     

超高速撞击加速技术及其应用研究

给出了二级轻气炮、三级轻气炮、静电加速器、等离子体加速器和聚能加速器等现代加速技术的原理,讨论了它们的弹丸质量和速度范围以及在超高速撞击实验中的应用．作为应用的例子给出了超高速撞击条件下航天器空间碎片防护结构以及压力容器损伤特性实验研究的结果．     

玄武岩纤维布Whipple防护结构超高速撞击损伤分析

针对加入玄武岩纤维织物对Whipple防护结构损伤产生的影响进行了实验研究.探讨了将玄武岩纤维织物作为航天器空间碎片超高速撞击损伤防护结构的增强材料用于航天领域的可行性.实验采用的基本构形为Whipple防护结构,玄武岩纤维布按不同方案布置在结构中.实验分析表明,玄武岩纤维布的防护作用在于:其发生击穿破坏时,击穿孔处的纤维束产生的断裂和孔边处纤维束产生的变形消耗和吸收了撞击物的撞击能量;破坏时,玄武岩纤维束中逐次断裂的纤维丝与撞击物的撞击除了对撞击物产生切割作用外还在撞击物中产生高频的间歇冲击波,两者都对撞击物产生碎化作用;玄武岩纤维布自身的破坏不会再产生新的大碎片.     

航天器空间碎片单护屏防护结构参数优化

为解决微流星体及空间碎片高速撞击威胁航天器的安全运行等问题，采用防护结构防护性能预报的Nysmith模型，以非线性优化方法分析撞击条件和结构参数对优化结果的影响。得出了最优解存在的可行性条件和防护间距下界与撞击参数的关系，以曲线图给出了各参数对优化结果的影响。研究表明优化结果在低撞击速度时随撞击速度的增加急剧增加，而在高撞击速度时趋于平缓。     

空间碎片清理飞行器捕获系统设计与仿真

空间碎片清理飞行器对于解决空间碎片日益增多的问题具有重要意义,非合作目标捕获是其关键技术之一。在对非合作目标捕获系统分析的基础上,设计了飞网式捕获系统,建立飞网简化模型和分析评价指标,并用ANSYS/LS-DY-NA对其进行仿真,分析发射速度和发射角对飞网展开的影响,利用C-W方程分析飞网发射误差。结果表明,空间飞网对于非合作目标捕获具有良好的容错性。     

M/OD Risk Assessment System and Its Applications

A risk assessment system named meteoroid & orbital debris risk assessment system (MODRAS) developed for assessing risks of the spacecraft under the meteoroid and debris environment (M/OD EM) is presented.The computing resolution of MODRAS has been verified by both the three generic spacecraft geometries of inter agency debris committee (IADC) and similar foreign software such as BUMPER,ESABASE,and MDPANTO.The results show that the system is fit well with the computing results of the foreign software.Typical applications of the system are also presented,including a manned spacecraft and a space shuttle.     

航天器微流星和空间碎片的防护方案

微波星和空间碎片是现在任何使用航天器的公认威胁。微流星和空间碎片的超高速撞击能导致航天器严重的损伤和灾难性的失效。因此,提高航天器的生存性是非常必要的。防护方案的确定是航天器设计的一个重要问题。     

一种基于HSI色度空间的磨粒成分分析法

介绍了HSI模型的基本原理,并提出使用HSI模型分析磨粒颜色分布。通过比较不同元素构成的磨粒图片在HSI模型参数上面的颜色分布,来判别该磨粒的元素构成,并且使用主成分分析法对磨粒颜色参数进行了化简,从而可以直观地对磨粒进行分类。实验证明,该方法在铁谱磨粒识别方面效果良好。     

Dynamics of tether-tugging reorbiting with net capture

To control the growth of space debris in the geostationary earth orbit(GEO), a novel solution of net capture and tether-tugging reorbiting is proposed. After capture, the tug(i.e., active spacecraft), tether, net, and target(i.e., GEO debris) constitute a rigid-flexible coupled tethered combination system(TCS), and subsequently the system is transported to the graveyard orbit by a thruster equipped on the tug. This paper attempts to study the dynamics of tether-tugging reorbiting after net capture. The net is equivalent to four flexible bridles, and the tug and target are viewed as rigid bodies. A sophisticated mathematical model is developed, taking into account the system orbital motion, relative motion of two spacecraft and spacecraft attitude motion. Given the complexity of the model, the numerical method is adopted to study the system dynamics characteristics. Particular attention is given to the investigation of the possible risks such as tether slack, spacecraft collision, tether rupture, tether-tug intertwist and destabilizing of the tug's attitude. The influence of the initial conditions and the magnitudes of the thrust are studied.     

考虑跳弹现象的飞机单击中易损性计算方法

飞机在威胁单次打击下的易损性计算方法通常假定威胁的弹道为直线,并且忽略跳弹影响。在实际的飞机遭遇中,当威胁的入射速度满足一定条件时,跳弹现象就会发生,直线弹道假设不再成立。基于该事实,提出了一种新的飞机易损性计算方法,以考虑威胁跳弹对易损性的影响。该方法利用JTCG/M E方程来计算威胁的实际弹道及运动状态的变化,以‘射击线扫描法’来计算每一条射击线对应的易损面积,进而获得飞机在威胁单次打击下总的易损面积及杀伤概率。算例采用传统方法和所提出的方法对某飞机在26个标准攻击方向上的易损性进行了计算与对比,验证了所提出方法的有效性与可行性。分析表明:①由于考虑了跳弹现象,所提出的方法能够更加真实地对飞机易损性进行评估;②当考虑跳弹影响时,所计算的飞机易损性通常要比不考虑跳弹时有所增加,打击方向不同,增加幅度有所不同;③飞机作战生存力/易损性评估中,跳弹影响不容忽视。     

Corrugation Stuffed Shield for Spacecraft and Its Performance

With the increasing number of orbital debris andspace environment continuing to deteriorate,mete-oroid and orbital debris(M/OD)have become a realthreat for space missions.So interest in the problemof M/OD has increased dramatically in the world.Based on observations,the population of orbital debrislarger than1cmin diameter is more than110thou-sand,larger than1mmin diameter is more than35million,andit will be continuing to increase5%an-nually[1].Hypervelocityi mpact of orbital debrislarg-er t…     

地基激光空间碎片清除技术研究

在研究空间碎片来源、危害与减缓对策的基础上,分析了危险空间碎片对航天器的威胁程度,比较了危险空间碎片的清除方法,介绍了地基激光空间碎片清除技术的发展现状和清除原理,给出了系统组成、工作流程和关键技术。介绍的方法对清除空间碎片,保护空间环境有一定的借鉴意义。     

汽车碰撞弹塑性散落物的运动学特性

为研究汽车碰撞散落物的行为力学特性,建立了汽车碰撞弹塑性散落物运动特性的仿真模型,模拟了四种条件下(散落高度一定时速度不同、散落速度一定时散落高度不同、散落高度与散落初速度一定时散落初始角度不同和散落初速度及散落角度一定时形状不同)弹塑性散落物的运动特性,进而分析了汽车碰撞弹塑性散落物的散落距离与散落速度、散落角度、散落高度及散落物形状之间的关系。结果表明:在散落体质量和体积相同的条件下,形状及散落初始角度对散落物距离影响较大,形状迎风面积是影响其运动持续时间、触地后翻滚和滑动的主要因素。散落物的散落角度在-65°≤α≤45°范围内的运动轨迹符合外弹道学理论,而在-90°≤α≤-65°及45°≤α≤90°发生回弹现象,偏离外弹道学理论轨迹。     

基于散射光谱的材质分类识别研究

有效的甄别、掌握空间碎片的状态,是合理利用太空资源和在轨航天器规避风险的前提,为了安全、持续地开发和利用空间资源,基于散射光谱,使用夹角余弦和欧式距离嵌入K临近法(KNN-AC-ED),并与经典的朴素贝叶斯分类器作为对比,对实验室测得的空间碎片中常用的四种材质进行分类识别。分类识别的结果显示,KNN-AC-ED法比经典的朴素贝叶斯分类器总体分类精度高4%。研究表明:朴素贝叶斯分类器需要提取每个光谱曲线的三个特征,而特征提取费时费力;KNN-AC-ED法利用光谱线型和强度两种信息,不仅全面的反应了光谱的信息,且计算相对更快捷。通过对空间碎片常用材质的分类,为进一步研究空间碎片的尺寸、材质等信息提供一定的借鉴意义。     

Influences and drivers of woody debris movement in urban watercourses

It is recognised that the blockage of culverts by woody debris can result in an increased risk of infrastructure damage and flooding. To date, debris transport analysis has focused on regional fluvial systems and large woody debris, both in flume and field experiments. Given the social and economic risk associated with urban flooding, and as urban drainage design shifts away from subsurface piped network reliance, there is an increasing need to understand debris movement in urban watercourses. The prediction of urban watercourse small woody debris (SWD) movement, both quantity and risk, has undergone only limited analysis predominantly due to lack of field data. This paper describes the development of a methodology to enable the collection of accurate and meaningful SWD residency and transportation data from watercourses. The presented research examines the limitations and effective function of PIT tag technology to collect SWD transport data in the field appropriate for risk and prediction analysis. Passive integrated transponder (PIT) technology provides a method to collect debris transport data within the urban environment. In this study, the tags are installed within small woody debris and released at known locations into a small urban natural watercourse enabling monitoring of movement and travel time. SWD velocity and detention are collated with solute time of travel, watercourse and point flow characteristics to identify the relationships between these key variables. The work presented tests three hypotheses: firstly, that the potential for unobstructed or un-detained SWD movement increases with flow velocity and water level. Secondly, that SWD travel distance, and the resistance forces along this travel path, influence SWD transport potential. Thirdly, the relationship between SWD and channel dimensions is examined with the aim of advancing representative debris transport prediction modelling.     

汶川地震灾区帽壳子滑坡形成泥石流的过程和特征

实地调查了汶川地震灾区北川县帽壳子滑坡转化为坡面泥石流和沟道泥石流的基本特征和形成过程,并利用能量守恒原理和Takahashi泥石流运动模型对其运动特征进行了分析。结果表明：对于强震诱发的滑坡,其层间碎块石土体强度低,滑坡体内部裂隙发育,在强降雨作用下容易转化为泥石流;滑坡转化为坡面泥石流的过程为岩土体沿基岩面下滑→撞击→强碎屑化→流动→快速停积;滑坡转化为沟道泥石流的过程为滑坡体崩滑→弱碎屑化→水流掺混→掏蚀沟道→流动堆积;滑坡转化为坡面泥石流后,起始速度较快,但没有沟道限制和水力作用,因此运动阻力较大,冲出距离远小于沟道泥石流;利用Takahashi泥石流运动模型计算得到的沟道泥石流冲出距离与实际观察值比较吻合。     

四川省大瑞乡泥石流灾害特征及减灾对策

在地质勘查的基础上,分析了大瑞乡泥石流形成条件、基本特征,并计算了泥石流的容重、流量、流速、冲出量等动力学参数,计算证明大瑞乡泥石流属于中频暴雨沟谷型泥石流。根据泥石流的具体情况和当地经济、社会、生态建设的需要,以及被保护对象的重要性,提出了"拦防结合"的防治对策。