Ballistics, navigation, and motion control for a spacecraft during its landing on the surface of Phobos

Basic concepts and algorithms laid as foundations of the scheme of landing on the Martian moon Phobos (developed for the Phobos-Grunt project) are presented. The conditions ensuring the landing are discussed. Algorithms of onboard navigation and control are described. The equations of spacecraft motion with respect to Phobos are considered, as well as their use for correction of the spacecraft motion. The algorithm of estimation of the spacecraft’s state vector using measurements with a laser altimeter and Doppler meter of velocity and distance is presented. A system for modeling the landing with a firmware complex including a prototype of the onboard computer is described.     

Numerical simulation of circulation of the Titan’s atmosphere: Interpretation of measurements of the <Emphasis Type="Italic">Huygens</Emphasis> probe

The results of numerical simulation of the general circulation in the Titan’s atmosphere at heights from 0 to 250 km are presented, obtained using a new model based on numerical solution of complete equations of motion of viscous compressible gas at the temperature distribution given by an empirical model. The model uses no hydrostatic equation and, as compared with traditional models, has higher resolution in vertical and over horizon. The results presented differ from results of other models and agree with the vertical profile of the zonal component of wind velocity measured by the Huygens spacecraft. Interpretation of this profile is given, including its main peculiarity consisting in a nonmonotonic behavior at heights from 60 to 75 km.     

小型试验固体火箭发动机研究

从理论上分析了影响固体火箭发动机性能散布的主要因素,设计了相应配套的小型试验固体火箭发动机,用于提高燃速测试精度,并应用于大型发动机的研制和批产。理论分析和测试结果表明,燃速的测试精度以及复合固体推进剂自身的燃速散布是影响固体火箭发动机性能的最主要因素,把握了复合固体推进剂燃速,可减小性能散布,确保大型固体火箭发动机批次研制和生产性能的稳定性和准确性。     

耦合凝相-气相动力学机理的二硝酰胺铵燃烧模型

为了研究二硝酰胺铵ADN(Ammonium Dinitramide)固体推进剂燃烧物理化学过程并预测其燃 烧特性,建立一个耦合凝相-气相动力学机理的ADN燃烧模型。该模型基于凝相与气相的总连 续方程、组元连续方程、能量守恒方程及有限速率化学动力学方程而建立,并引入多组元系 统状态方程封闭方程组。模型中包含34种组元,1个固相（凝相）ADN分解总化学反应和165 个气相细节（基元）化学反应,并使用以温度函数表示的物性参数进行计算。应用气相燃烧 模型 对0.6 MPa下ADN燃烧火焰温度、组元摩尔浓度分布进行预测;应用耦合凝相-气相的燃烧模 型对0.2 MPa～36 MPa压强区域内柱状端燃ADN推进剂燃速、燃烧表面温度进行预测,计算结 果与文献报道试验数据较吻合。说明该燃烧模型能够较准确描述ADN气相燃烧波结构和ADN固 体推进剂燃速特性。
     

固液火箭冲压发动机燃烧室流场数值仿真

固液火箭冲压发动机通过固液两种燃料匹配工作,相比传统的固体火箭冲压发动机和液体燃料冲压发动机具有较为明显的优势.基于离散相模型和单步反应模型,采用Fluent 对设计点飞行参数下,不同结构和不同工况条件下的燃烧室两相反应流场进行了数值仿真.结果表明,燃气发生器喷管参数和进气道进气角度主要影响空气与燃气流的撞击以及头部区...     

卫星遥感影像外方位元素的误差传播研究

高分辨率卫星遥感影像的几何定位精度与影像外方位元素精度密切相关.文章针对单景影像直接对地定位和立体影像前方交会定位两种典型情况,对影像各外方位元素在目标几何定位中的误差传播规律进行分析比较,相关结论可供卫星姿控及相机载荷设计方参考.     

双组元统一推进系统加注混合比改进算法及应用

卫星双组元统一推进系统加注混合比,是确定卫星氧化剂和燃烧剂加注量的重要参数。正确地确定加注混合比可以减少卫星的呆重,增加推进剂余量和卫星寿命。文章在原有混合比计算的基础上,分析了在轨不同阶段的不同压力、温度条件下10N推力器和490N变轨发动机的流量情况和入口压力、氧化剂和燃烧剂压力变化情况,利用推力器和变轨发动机地面...     

一种基于SIFT和KLT相结合的特征点跟踪方法研究

在目标发生明显姿态和大小变化条件下,为了利用基于特征点的跟踪算法实现对目标可靠、稳定跟踪,提出了一种SIFT算法和KLT(Kanade-Lucas-Tomasi)匹配算法相结合的特征点跟踪方法。通过对SIFT算法进行优化,使得到特征点分布相对均匀,同时不存在聚集现象;通过对KLT匹配算法进行分层迭代设计,提高了目标作快速运动时的匹配精度;最后根据特征点匹配结果,结合Greedy算法得到目标的准确位置。实验结果表明：该算法能够很好地适应目标姿态和大小的变化,实现对结构复杂目标的稳定跟踪;比KLT跟踪算法具有更好的鲁棒性和稳定性,能得到更加准确的目标位置。      

自由段弹道扰动引力计算的球谐函数极点变换

为提高弹道导弹自由段扰动引力赋值速度,提出了自由段扰动引力计算的球谐函数极点变换一般方法。重点针对轨道动量矩与天球交点为极点及主动段关机点为极点两种情况,推导了考虑侧向偏差和地球旋转修正的扰动引力计算的球谐函数极点变换模型。仿真分析表明:从落点偏差来看,前者扰动引力计算相对误差为1.89%,后者为6.07%,满足诸元和制导精度要求。     

The results of flight tests of an attitude control system for the Chibis-M microsatellite

The attitude control system of the Chibis-M microsatellite is described. Results of flight experiments on damping the initial angular velocity (made using magnetorquers) are considered, as well as stabilization in the orbital referece frame, and orientation of solar arrays toward the Sun using reaction wheels. The operation of algorithms of satellite attitude determination on sunlit and shadow segments of the orbit is also under study. The general logic of operation of the attitude control system in automatic mode is presented and discussed.