太阳帆航天器的关键技术

将太阳帆航天器所涉及的关键技术划分为4个方面：总体设计、轨道和姿态动力学与控制、太阳帆材料及其性能、太阳帆折叠与展开。针对每项关键技术,基于对国外长期研究结果进行分析并阐述主要技术特征,梳理国内相关研究进展,包括笔者与合作者的研究成果,分析存在的主要问题。根据上述分析,指出我国发展太阳帆航天器应该重视的若干问题。     

充气薄膜桁架的协同折叠设计及展开过程仿真

充气薄膜桁架结构可应用于大型空间充气薄膜航天器的展开部件和支撑结构。研究了充气薄膜桁架结构的协同折叠设计方案,首先推导了蒙皮结构的折叠状态几何公式,然后设计充气桁架的折叠方案,以几何适应于蒙皮结构折叠状态。建立了协同折叠设计方法,并得到了参数化模型。方案实现了横向和纵向同时折叠,横向折叠率为2.67,纵向折叠率为8.82。基于改进的弹簧-质点系统,完成了充气薄膜桁架结构的充气展开动力学仿真,得到了展开动力学行为和参数。仿真结果表明展开过程平稳可靠,未发生各构件间的物理干涉,从而评估了协同折叠设计方案的合理性,为此类结构的工程应用提供了技术支撑。     

展开式薄膜遮光罩设计及重复展开精度研究

针对星敏感器的杂光抑制需求,设计了一种可以实现轴向展开的圆柱状展开式薄膜遮光罩,包括充气支撑管、薄膜蒙皮和挡光环,并完成了各构件的结构和材料设计。建立了薄膜蒙皮的运动学模型,分析了构型随着二面角的变化情况,验证了薄膜蒙皮采用hexagonal折纸样式可以完全折叠和展开。通过试验研究了遮光罩的重复展开精度,包括轴向和径向展开精度等。研制了遮光罩原理样机,并开展了地面展开试验,表明在充气支撑管的驱动下能够顺利展开,为大尺寸遮光罩的工程应用提供了新的技术方案。     

大型网状天线展开过程温度及展开时机分析

大型网状天线在轨展开过程复杂,风险大。反射器在展开过程中的温度影响展开动力与碳纤维管件抗弯能力,是反射器展开安全的关键因素。通过测试得到反射器展开动力的传动效率、桁架管件抗弯能力随温度变化规律,即-65℃时管件抗弯能力最好,而传动效率随温度升高而提高。通过建立大型网状天线有限元模型与节点矩阵转换算法,模拟展开臂与反射器的展开过程,对管件与T型铰链在轨温度变化规律进行分析,确定最佳展开时机,降低展开过程中展开动力不足、管件强度过载等风险。分析结果表明：布置在地球静止轨道卫星东舱板的大型网状天线展开时机为6:00~9:00时,管件抗弯能力最强;展开时机为4:00时,T型铰链展开动力传动效率最高。     

卫星太阳翼展开运动分析

卫星太阳翼是许多应用卫星必不可少的主要部件,太阳翼在轨道上的展开运动分析对卫星设计起着很重要的作用。文章提出利用能量守恒的原理,以太阳翼展开角(?)为参数的分析方法。该方法计算简捷,精度高,并且方便判断,特别适用于工程应用。     

基于ANCF的薄膜太阳帆自旋展开动力学模拟

执行深空探测任务的薄膜太阳帆在入轨展开过程中,其薄膜结构在宏观力学响应上表现出显著的拉压不对称特性.系统的动力学行为呈现出强烈的非线性特征,使其动力学建模与仿真计算面对巨大挑战.基于绝对节点坐标方法(Absolute Nodal Coordinate Formulation,ANCF),整合张力场和不同模量弹性理论,推...     

基于充气薄膜的可展开帆板结构设计

充气薄膜结构具有质量轻、收纳比高的优势。通过理论分析及实验验证的方法,得到了充气薄膜管承载力矩与充气内压、管道内径、展开程度之间的映射关系。进一步通过“厚度包边”法处理二级展开帆板的厚度问题,设计了转动锁定、转动-滑移锁定、搭接锁定连接结构,提出薄膜管驱动的二级可展开矩形帆板、圆形帆板以及百叶窗式矩形帆板三种大尺度可展开帆板结构形式,并进行展开状态的模态仿真,对比其模态振型。本设计可为大尺度充气可展开结构形式提供参考。     

空间可展开薄膜遮光罩设计与分析

对于觅音计划的光学系统而言,太阳光是其杂散光的首要来源,是影响成像质量的重要因素.通过将仿生技术和折纸理论相结合,完成光学系统的遮光罩设计.依据花朵开放过程,获取遮光罩的拓扑构型,完成遮光罩折展设计,并根据光学系统任务需求,优化遮光罩拓扑构型.采用底面为正六边形的拓扑构型时,遮光罩的折展比为8,且折叠后的包络空间和卫星...     

太阳帆柔性结构动力学仿真分析

研究了太阳帆结构的有限元仿真分析问题.针对太阳帆航天器实际结构特点,建立合理的有限元模型;得出合理的边界预紧力的大小与方向;给出太阳帆航天器伸展臂对预紧力的屈曲模态分析以及屈曲临界载荷;进行了太阳帆结构的无预紧力结构模态分析与有预紧力结构模态分析,并对结果进行了比较.研究结果表明,太阳帆航天器预紧力结构模态分析更为合理,为太阳帆航天器控制系统工程设计与仿真提供了参考数据基础.     

柔性张拉薄膜可展开空间天线研究现状与发展趋势

柔性张拉薄膜可展开天线是将柔性电子、柔性薄膜材料、柔性结构和柔性展开技术融合创新的一种具有广泛应用前景的大型可展开空间天线,具有轻质、高展收比、高增益和波束灵活的特点,可有效满足遥感、通信、深空探测卫星的特殊需求。阐述了柔性张拉薄膜可展开天线的特点与研究现状;对空间薄膜天线研制的基础理论及综合测试方法进行了总结;结合具体工程问题,论述了大型可展开空间薄膜天线研制所需要解决的关键技术难题,并进一步分析了薄膜天线的技术发展趋势。     

Solar sail near the Sun: Point-like and extended models of radiation source

Some modifications of solar sail radiation pressure forces on a plate and on a sphere for use in the numerical simulation of ‘local-optimal’ (or ‘instantaneously optimal’) trajectories of a spacecraft with a solar sail are suggested. The force model development is chronologically reviewed, including its connection with solar sail surface reflective and thermal properties. The sail surface is considered as partly absorbing, partly reflective (specular and diffuse), partly transparent. Thermal balance is specified because the spacecraft moves from circular Earth orbit to near-Sun regions and thermal limitations on the sail film are taken into account. A spherical sail-balloon can be used in near-Sun regions for scientific research beginning with the solar-synchronous orbit and moving outward from the Sun. The Sun is considered not only as a point-like source of radiation but also as an extended source of radiation which is assumed to be consequently as a point-like source of radiation, a uniformly bright flat solar disc and uniformly bright solar sphere.     

Time step size and model stiffness in the simulated slew of a tow of square sails

In order to assess space tow solar sail stability and control feasibility, slew simulations are performed for a simplified but dynamically representative km-class tow-like sail of sixteen 25 m square units (10,000 m² total area and 110 kg gross mass) with a 250 kg payload. It is seen that, for the dimensions considered, the space tow concept is structurally sound and its control is feasible. While observed instabilities are identified as numeric in nature and are eliminated accordingly, their very occurrence highlights the need for a refinement of the model for future studies. The analyses are carried out with custom software implementing non-standard implicit-iterative time integration with innovative elements. A new damping model, specifically tailored for the analysis of truly gossamer systems such as solar sails, is also proposed.     

Analysis of the solar sail deformation based on the point cloud method

The deformation of the solar-sail membrane is an important factor for causing inaccuracies in the solar-sail missions. This paper describes the solar sail under deformation by using a new modelling technique based on point cloud and triangular mesh generation. Two types of deformation, stemming from wrinkling and billowing, are modelled. The changes in the solar radiation pressure force and the moment caused by deformation are calculated and compared to the ideal non-deformed case. The heliocentric spiral trajectory and the orbital angular momentum reversal trajectory are taken as examples to quantify the influence of the deformation from an orbit point of view. Additionally, point cloud simplification, based on the normal vector and bounding box, is utilized to simplify the original deformed-sail model. It involves a reasonable reduction and renewal of the points in the model considering the variation of surface curvature. The simplification and its modelling accuracy are numerically investigated as well as computational efficiency.     

基于滑动多项式回归分析的区间估计和飞行数据异常值处理

针对飞行数据中的异常值给出了一种处理算法,对其进行识别、剔除与补正。根据飞行数据的特点建立了滑动二次多项式回归模型,并变换为正交多项式计算回归系数。在给定的置信概率下求下一个点的置信区间,判断实测数据是否为异常值。将已判定的异常值剔除并用拉格朗日法补正。在某型共轴式直升机的动力学特性研究工作中,利用这一方法对多次外场试飞数据进行了异常值处理,得到了比较满意的结果。     

A superposed epoch study of the effects of solar wind stream interface events on the upper mesospheric and lower thermospheric temperature

The response of mesosphere and lower thermosphere (MLT) temperature to energetic particle precipitation over the Earth’s polar regions is not uniform due to complex phenomena within the MLT environment. Nevertheless, the modification of MLT temperatures may require an event-based study to be better observed. This work examines the influence of precipitation, triggered by solar wind stream interfaces (SI) event from 2002 to 2007, on polar MLT temperature. We first test the relationship between the ionospheric absorption measured by the SANAE IV (South African National Antarctic Expedition IV) riometer and the layer of energetic particle precipitation from POES (Polar Orbiting Environmental Satellites). The combined particle measurements from POES 15, 16, 17 and 18 were obtained close in time to the pass of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) temperature retrieval. Here, a superposed epoch technique is described and implemented to obtain average temperature profiles during SI-triggered particle precipitation. The superposed epoch average shows no significant temperature decrease below 100 km prior to the onset of SI-triggered precipitation, whereas a clear superposed average temperature decrease is observed at 95 km after the SI impact. A case study of SI event also yields similar observations. Results indicate that cooling effects due to the production of mesospheric odd hydrogen might be major contributors to temperature decrease under compressed solar wind stream.     

Physics of ion acceleration in the solar flare on 2005 September 7 determines γ-ray and neutron production

Relativistic neutrons were observed by the neutron monitors at Mt. Chacaltaya and Mexico City and by the solar neutron telescopes at Chacaltaya and Mt. Sierra Negra in association with an X17.0 flare on 2005 September 7. The neutron signal continued for more than 20 min with high statistical significance. Intense emissions of γ-rays were also registered by INTEGRAL, and during the decay phase by RHESSI. We analyzed these data using the solar-flare magnetic-loop transport and interaction model of Hua et al. [Hua, X.-M., Kozlovsky, B., Lingenfelter, R.E. et al. Angular and energy-dependent neutron emission from solar flare magnetic loops, Astrophys. J. Suppl. Ser. 140, 563–579, 2002], and found that the model could successfully fit the data with intermediate values of loop magnetic convergence and pitch-angle scattering parameters. These results indicate that solar neutrons were produced at the same time as the γ-ray line emission and that ions were continuously accelerated at the emission site.