用Schamberg方法计算卫星阻力系数

Schamberg的“超热自由分子流”粒子-表面作用模型比较真实地反映了高空大气分子与空间飞行器材料之间的相互作用,它可以用来计算卫星的阻力系数。本文简要叙述该模型的基本思想,介绍几种常见简单几何形体卫星的阻力系数计算公式,并给出计算曲线。     

复杂空间载流管道系统流固耦合动力学模型及其验证

 针对飞机复杂管路系统振动分析,提出了一种复杂空间管道系统流固耦合动力学模型,在模型中用梁单元对管道进行了离散,每个节点考虑了x、y、z这3个方向的平动以及绕x、y、z这3个方向的转动,共计6个自由度;在单元中考虑了流固耦合效应,计及了流体流速对管道振动的影响;建立了管道与基础、管道与管道间的弹性连接,以适应多个管道之间的耦合振动分析;模型采用Newmark-β数值积分法获取系统响应。针对实际液压试验台的空间管路系统,利用锤击法进行实验模态分析,将本文模型的仿真结果与实验结果和商用有限元软件ANSYS Workbench的计算结果进行了分析比较,验证了本文模型的正确性。最后,仿真计算了流固耦合作用下流速对管道系统固有频率的影响规律。     

海上舰船目标的宽带雷达散射特征信号仿真

提出一种将目标高频电磁（EM）散射计算多径回波模型与不同海况条件下粗糙海面前向复反射系数模型相结合的方法,对海上舰船目标宽带雷达回波进行仿真和分析。简要分析了目标-海面相互作用的多径回波模型,给出了目标体的电磁散射计算方法,研究了不同海况条件下海面前向复反射系数随频率和擦地角的变化特性,并通过仿真分析了海面对舰船目标雷达回波的影响。对比分析舰船目标体直接散射及在不同海况条件下考虑多径效应时的雷达散射截面（RCS）变化特性,并在不同海况条件下对目标进行二维逆合成孔径雷达（ISAR）成像仿真,验证了本文方法的有效性。     

霍尔效应推力器羽流的PIC/MCC模拟(英文)

采用粒子网格单元与蒙特卡洛碰撞相结合的方法,建立霍尔效应推力器羽流的二维轴对称模型.模型中电子作为流体处理且服从等熵假设,离子(Xe~+和Xe~(2+))采用粒子描述,中性原子为背景气体.自洽电势通过求解非准中性、线性化Poisson方程获得.模拟结果与实验数据相比较表明,模型能够可靠预估羽流的物理特性;粒子入射发散角为30°～40°时模拟结果与实验数据吻合较好;倒流区离子数密度可达10~(14)m~(-3),会对飞行器表面造成损害;且等离子体密度和电子温度沿轴线方向衰减很快.     

空间原子氧环境对航天器表面侵蚀效应及防护技术

文章阐述了空间原子氧环境及其对航天器表面的侵蚀机理、损伤效应、防护方法,介绍了北京卫星环境工程研究所在原子氧防护技术研究方面取得的进展。过去5年里,该所采用物理气相沉积、溶胶-凝胶化学等方法制备了原子氧防护涂层,并对涂层样品进行了环境适应性评估试验,获得了初步的研究结果。结果表明这些样品均表现出很好的抗原子氧性能。     

电路功能可靠性仿真分析技术

电路功能可靠性仿真分析技术是性能与可靠性一体化设计工程中的一项关键技术。文章介绍了面向工程应用的电路功能可靠性仿真技术的概念、技术体系和主要技术,还介绍了国内外的发展情况。     

箔片预变形对箔片气体径向轴承静特性影响分析

针对箔片预变形对波箔型气体径向轴承静特性影响进行了数值仿真研究.建立了考虑气体可压缩性、箔片预变形等因素的气膜厚度数学模型.运用牛顿迭代和有限差分法耦合求解Reynolds方程和气膜厚度方程,研究了箔片预变形对轴承气膜厚度分布、压力分布和承载能力等特性的影响.与有名义半径间隙情况的波箔型气体轴承特性对比分析,结果表明,有箔片预变形的波箔型轴承具有更好的旋转稳定性和轴承承载能力,同时有较大预变形的波箔型气体轴承具有更高的轴承承载能力.      

Deployment dynamic analysis of deployable antennas considering thermal effect

Dynamic analysis of flexible multibody systems is complex. Several successful methods have been demonstrated. However, few works discussed the dynamic performance of the flexible multibody under different temperatures. This paper uses the absolute nodal coordinate formulation to analyze the flexible body dynamics of deployment structures under different temperatures to simulate space environments. The dynamic equations of finite element in temperature field are developed. Then a computer-aided simulation of flexible multibody systems in temperature field is implemented. A general four-bar mechanism under different temperatures as a simulation example is demonstrated, and the deployment characteristics of a special four-bar mechanism as a basic module of the hoop truss deployable antenna is analyzed under different temperatures in order to evaluate the dynamic performance of the deployable antenna in space environments. The simulation results indicate the influence factors of deployment dynamic characteristics include the structural form, material properties, geometric parameters and deployment planning in ambient and thermal/vacuum environments.     

动压转子陀螺的气动交叉耦合误差

采用动压气浮轴承转子的单自由度陀螺,如果在陀螺输出轴（即框架轴或浮子轴）方向有外加速度作用时,由于动压轴承的气动交叉耦合效应,转子在输出轴方向产生位移的同时还会在输入轴方向产生位移。这将使陀螺产生与输出轴加速度和转子轴加速度有关的漂移。由于这项漂移还具有振动整流特性,难于进行补偿,因此需要在设计、生产上加以控制。     

Statistical survey on sawtooth events,SMCs and isolated substorms

Solar wind driving can cause a variety of different responses in the magnetosphere. Strong and steady driving during geomagnetic storms may result in sawtooth events. Strong to moderate driving may be followed by either sawtooth events or steady magnetospheric convection (SMC) events. Lower solar wind energy input typically leads to the formation of isolated non-storm substorms. This study uses superposed epoch analysis to reveal the typical properties of these three event groups as well as their similarities and differences. We use IMF and solar wind parameters, as well as ground-based indices (AL, SYM-H, ASY-H, PCN) to examine the level of solar wind driving and its response in the magnetosphere. Our results show that sawtooth events are associated with the strongest ionospheric activity. The subgroups of events during constant solar wind _EY$E_Y$ show that the key difference between the events is the average solar wind speed. Particularly, the high activity during sawtooth events is driven by high solar wind speed, while the lowest average speed during the SMCs may explain the lack of substorm activity during the steady convection periods.