航天器用回转支撑机构设计优化及试验验证

本文结合国内空间站对日定向驱动机构所采用的回转支撑机构方案,重点围绕滚轮-导轨运动副接触形式,分析了圆柱形滚轮外形方案所存在的“滚中带滑”情况,针对性地开展了滚轮外形结构设计优化,提出了圆锥形设计改进方案。为了验证该方案的设计正确性、工程可行性以及改进有效性,计算了改进方案的运动副滚滑比,评估了零件加工精度、产品装配偏差以及空间温度环境等对滚滑比的影响,分析了改进方案对机械接口和载荷条件的影响,开展了真空寿命试验。结果表明:改进方案能够实现在理论上滚轮-导轨运动副为纯滚动运动,对零件加工精度、产品装配偏差以及空间温度环境有较好的容差性和适应性,并且对机械接口和载荷条件无影响,能够有效改善滚轮-导轨运动副接触状态,延长寿命,满足使用需求。     

Validation of IRI-2012 TEC model over Ethiopia during solar minimum (2009) and solar maximum (2013) phases

This paper investigates the capacity of the latest version of the International Reference Ionosphere (IRI-2012) model in predicting the vertical Total Electron Content (vTEC) over Ethiopian regions during solar minimum (2009) and solar maximum (2013) phases. This has been carried out by comparing the IRI-2012 modeled and experimental vTEC inferred from eight ground based dual frequency GPS (Global Positioning System) receivers installed recently at different regions of the country. In this work, the diurnal, monthly and seasonal variation in the measured vTEC have been analyzed and compared with the IRI-2012 modeled vTEC. During the solar minimum phase, the lowest and highest diurnal peak of the experimental vTEC are observed in July and October, respectively. In general, the diurnal variability of vTEC has shown minimum values around 0300 UT (0600 LT) and maximum values between around 1000 and 1300 UT (1300 and 1600 LT) during both solar activity phases. Moreover, the maximum and minimum monthly and seasonal mean hourly vTEC values are observed in October and July and in the March equinox and June solstice, respectively. It is also shown that the IRI-2012-model better predicts the diurnal vTEC in the time interval of about 0000–0300 UT (0300–0600 LT) during the solar minimum phase. However, the model generally overestimates the diurnal vTEC except in the time interval of about 0900–1500 UT (1200–1800 LT) during the solar maximum phase. The overall result of this work shows that the diurnal vTEC prediction performance of the model is generally better during the solar minimum phase than during solar maximum phase. Regarding the monthly and seasonal prediction capacity of the model, there is a good agreement between the modeled and measured monthly and seasonal mean hourly vTEC values in January and December solstice, respectively. Another result of the work depicts that unlike the GPS–TEC the IRI-2012 TEC does not respond to the effect resulted from geomagnetic storms.     

Spectra of the two official GLEs of solar cycle 24

Based on ground-level data and on satellite data we determine in this work the observational spectrum of both, the Ground Level Enhancement of May 17, (2012) the so-called GLE71 and the Ground Level Enhancement of September 10, 2017 (GLE 72). We describe a simplified method to obtain the experimental spectrum at ground level. Data of the GLE71 and GLE72 indicate the presence of two different populations, each one with a different energy spectrum. On the other hand, we explore the kind of phenomena that take place at the source in these two particular events. In contrast with other methods based on the temporal synchronization between electromagnetic emissions of flares and coronal mass ejections (CME), here we develop an alternative option based on the study of the accelerated particles, by adjusting our theoretical spectra to the observational spectra. The main results of this work are the derivation of the source and acceleration parameters involved in the generation process. These results lead us to construct possible scenarios of particle generation in the source for each one of the two studied GLEs.     

航天器太阳圆面速度差/太阳视方向组合导航

针对航天器，尤其是深空探测器的自主导航问题，提出了一种新的太阳圆面速度差天文量测信息，该信息利用太阳的较差自转所造成的太阳圆面各点速度不同的特性，是探测器当前位置的函数，其几何本质是一个探测器的位置圆锥。在此基础上，基于太阳圆面速度差和太阳视方向互补的特性，提出了一种太阳圆面速度差/太阳视方向组合导航新方法，将太阳圆面速度差与太阳视方向2种量测量结合起来，实现了量测量之间的优势互补，进一步提高了导航性能。以太阳探测器为例进行了仿真，仿真结果表明相比较于单独用太阳圆面速度差或太阳视方向的导航方法，基于太阳圆面速度差/太阳视方向的组合导航方法精度分别提升了10.2%和16.0%。此外，还分析了光谱仪精度、采样周期和光谱仪数量对导航性能的影响，为深空探测自主导航提供了新的理论与方法。     

含多间隙柔性可展帆板动力学建模及仿真

为研究柔性和多级铰链间隙对帆板展开过程动力学特性的影响，以月球车两级往复可展太阳帆板为研究对象，采用修正Coulomb模型表述摩擦力，通过接触碰撞力描述间隙，运用有限元法进行帆板柔性化，进而建立多间隙-柔性耦合的动力学模型。采用变步长伦哥库塔法进行数值求解，模拟帆板展开过程，分析了多间隙和柔性对帆板质心加速度、铰链间隙碰撞力等参数的影响。结果表明，在保证展开机构刚度要求的前提下，帆板柔性可补偿因铰间隙引起的加速度波动，减弱间隙处碰撞的剧烈程度，减小碰撞力幅值，进而改善帆板展开机构的动态特性。研究结果可用于指导月球车两级往复可展太阳帆板等同类型的可展机构动态优化设计。     

一种可扩展的末制导雷达通用检测系统

介绍了采用ＩＥＥＥ－４８８总线标准实现的末制导雷达通用检测系统,概述了其硬件的组成和系统特点。并针对末制导雷达的测试规程和要求,阐述了软件系统的模块化设计思想,介绍了采用虚拟面板和虚拟仪器技术的ＡＴＥ软件设计方法。     

太阳电池片间隙区域充电电场的数值计算

高压太阳电池阵在空间带电粒子环境中易发生静电放电,特别是太阳电池片间隙区域存在着诱发二次放电的风险。文章建立了太阳电池片间隙区域充电模型,基于静电理论研究了计算太阳电池片间隙区域充电电场的算法。数值计算结果表明:太阳电池片间隙区域两侧,充电电场呈对称分布;玻璃盖片与基底之间存在明显的电位差,且玻璃盖片的电位高于其他部位。     

蜂窝夹层板强度分析模型对比研究

在蜂窝夹层板强度设计中,为了降低计算成本,并得到准确的计算结果,需要对蜂窝夹层板进行有效的等效建模。以简化的仪器安装板为例,对比研究了等效板、三明治夹芯板、三明治实体夹芯板和蜂窝体夹芯板4种强度分析模型,并基于蜂窝体夹芯板计算模型,对4种强度分析模型下的变形、应力和频率计算结果分别进行了对比研究,得到计算精度、适用范围等工程结论,同时形成相关软件应用界面,指导飞行器结构设计。     

UltraFlex太阳电池阵的结构优化

以提高圆形太阳电池阵的展开过程稳定性和固有频率为优化目标,以UltraFlex太阳电池阵为模型,采用有限元软件SAMCEF对其进行结构优化。以承重梁材料、斜梁开口高度、斜梁位置、梁截面高度及厚度5种结构参数为优化变量,进行了多种工况的展开动力学仿真和模态计算。经分析发现,结构展开后期太阳毯与支撑梁拉扯会导致支撑梁剪切应力激增;梁材料、斜梁位置与支撑梁截面高度对太阳电池阵的展开过程稳定性影响较大;当梁材料为碳纤维,斜梁位置为1100 mm,梁截面高度为20 mm时,展开过程稳定性最好;斜梁位置和承重梁截面厚度对结构固有频率影响较大;当斜梁位置为900 mm或1100 mm、承重梁截面厚度从3 mm增至3.5 mm时,系统固有频率涨幅最大,由此带来的质量增加可以接受。     

跨流区超低轨航天器快速气动力计算方法

超低轨飞行器常工作在过渡流区中,过渡流区中气动特性多变,建模困难,目前缺少较好的快速气动力计算方法。在面元法的基础上,提出了设计迎风单元筛选算法与logistics-log桥函数,对连续流区与自由流区结果进行加权,实现超低轨卫星的气动力估算。在方法验证中,对圆柱与钝头双楔体在宽努森数(Kn)范围下的气动力进行测算,发现结果与直接模拟蒙特卡洛法(DSMC)数据一致。对典型超低轨飞行器地球重力场和海洋环流探测卫星(GOCE)的气动力进行分析,发现GOCE随着姿态变化阻力变化明显,需要舵面或陀螺仪进行姿态控制;在不同高度下的阻力量级变化大,在超低轨运行时需要动力系统维持高度。