共查询到20条相似文献,搜索用时 31 毫秒
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简述控制高层大气的主要能源和描绘了高层大气的主要天气变化过程,并且阐明高层大气及其预报研究的量要性和给出高层大气对航天飞行有严重影响的几个实例,最后简介高层大气及其预报研究的新动向。 相似文献
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如何求神经网络控制使非线性空间飞行混沌运动不会发生。该法是在输出层用回归权代替常数权再用EM算法来估计回归权的参数 ,这样修正的RBF的神经网络控制就可使非线性空间飞行不会出现混沌现象。这种算法R Langari,L Wang&J Yen (1997) [1] 在研究径向基函数网络时提出过。其突出的优点是把复杂的多参数的最优化问题分离为N个小型最优化问题 ,这里N是隐藏层单元数。 相似文献
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为了满足飞行器协同飞行任务需求,本文研究了带有时间约束的再入滑翔轨迹设计方法。首先,建立了合理假设条件下的再入滑翔运动模型,并且提出了一种再入滑翔轨迹分段方法。其次,针对不同飞行段特点及任务需求,分别设计了各段导引律。其中,重点推导了滑翔段飞行剩余时间和剩余航程的解析解,将剩余飞行时间与末制导交班点速度建立对应关系,运用解析预测-校正思想,通过在时间调整段和能量调整段调节倾侧角翻转时机和幅值,同时满足末端能量和时间约束。最后,通过理论分析与仿真校验说明了本方法的有效性及鲁棒性。 相似文献
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The locomotor activity of young Drosophila melanogaster (fruit fly) was studied during a Nike-Orion sounding rocket flight, which included a short-duration microgravity exposure. An infrared monitoring system was used to determine the activity level, instantaneous velocity, and continuous velocity of 240 (120 male, 120 female) fruit flies. Individual flies were placed in chambers that limit their motion to walking. Chambers were oriented both vertically and horizontally with respect to the rocket's longitudinal axis. Significant changes in Drosophila locomotion patterns were observed throughout the sounding rocket flight, including launch, microgravity exposure, payload re-entry, and after ocean impact. During the microgravity portion of the flight (3.8 min), large increases in all locomotion measurements for both sexes were observed, with some measurements doubling compared to pad (1 G) data. Initial effects of microgravity were probably delayed due to large accelerations from the payload despining immediately before entering microgravity. The results indicate that short-duration microgravity exposure has a large effect on locomotor activity for both males and females, at least for a short period of time. The locomotion increases may explain the increased male aging observed during long-duration exposure to microgravity. Studies focusing on long-duration microgravity exposure are needed to confirm these findings, and the relationship of increased aging and locomotion. 相似文献
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Commercial suborbital space flights will reach altitudes above 100 km, with 3–5 min of weightlessness bracketed by high-g launch and landing phases. The proposed frequency of these flights, and the large passenger population, present interesting opportunities for researchers in the life sciences. The characteristics of suborbital flight are between those of parabolic and orbital flights, opening up new scientific possibilities and easing the burden for obtaining access to 0g. 相似文献
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高层大气模型对空间站轨道漂移和寿命的影响分析 总被引:2,自引:0,他引:2
本文以轨道摄动分析方法一阶理论为基础,其中大气阻力摄动采用数值积分方法,给出一种可利用各种大气模型进行轨道摄动分析的计算方法,并利用三种高层大气模型(CIRA—72,CIRA—86和DTM)和三个太阳活动水平(F10.7=100,150和200)分析比较了大气阻力振动对高度为400km的空间站轨道漂移和寿命的影响,以及估算修正轨道漂移所需的能量。给出的定量分析结果将为空间站或航天飞行器的轨道设计和能量估算提供依据。 相似文献
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辐射换热条件下空间薄壁圆管结构瞬态温度场、热变形有限元分析 总被引:11,自引:1,他引:11
对航天结构中常见的辐射换热条件下的空间薄壁圆管结构,构造了一种用于非线性瞬态温度计算的傅立叶-有限单元。圆管温度沿杆长用有限元离散,沿周向分布展成三角函数。圆管温度单元每个结点包含平均温度、余弦和正弦分布温度幅三个自由度,并且在每个时间步内实现了平均温度增量与沿截面温差增量的解耦。在结构热变形分析时圆管单元节点上既承受温度轴力,又承受截面温差导致的热弯矩。采用这种单元对非线性换热条件下的复杂空间结构进行离散可以较准确地反映结构的温度场与热变形。经与前人的解析解和三维有限元结果的验证,证明该单元是可靠的。对太阳能帆板梁与空间抛物面天线的热-结构分析说明这种新单元的应用价值。 相似文献
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空间动能武器系统仿真研究 总被引:1,自引:0,他引:1
在介绍空间动能武器系统的基础上 ,对整个系统建立了数学模型 ,进行了仿真 ,并且得到了符合实际、满足要求的仿真结果 ,最后提及了更高层次的仿真方法。达到了对整个系统的运行和性能进行仿真模拟的目的 ,为这一方向的仿真试验工作提供了一个实用可行的方法 相似文献
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In order to justify high expenditure during this period of financial crisis, Space Agencies have attempted to increase the returns on their investments in Space missions by encouraging the commercial use of advanced technologies. The development of a technology transfer process from Space to Earth not only benefits the Aerospace industry but also the network of national companies. Technology transfer has been shown to stimulate innovation in business and commerce, support economic growth and provide a return on public investment in research and development (R&D). The aim of this paper is to systematically review the Space technology transfer literature and to suggest directions for future research. The range of research and studies in the literature on this topic requires a systematic review to summarize the results in an unbiased and balanced manner and to interpret these in a way that highlights the research gaps. This article presents an overview of the dominant thinking (explicit in selected articles from 1995 to present), indicating the problems of analysis, research gaps and a future research program. 相似文献
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近地轨道大型航天器的环境充电 总被引:1,自引:0,他引:1
许多空间实验和电子计算机预测已经揭示,在极光电子环境中大型航天器的充电电位会高达6000--7000V。对采用大功率太阳阵的航天器而言,其相对于空间等离子体的悬浮电位将因太阳阵工作电压的提高而增加。例如表面材料因遭受离子轰击和电弧放电而老化、剥蚀、由于材料再沉积而使表面污染增加以及航天器电子系统因静电放电而受到严重的干扰和破坏等。因而对载人航天和长寿命空间站而言,解决航天器带电问题不可等闲视之。对 相似文献
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Astronauts are often on a voluntarily reduced energy intake during space missions, possibly caused by a metabolic or emotional stress response with involvement of the central serotonergic system (SES). We investigated 24 h urinary excretion (24 h-E) of serotonin (5-HT) and 5-hydroxyindol acidic acid as indicators of the SES in healthy males under two different normocaloric conditions: normal physical activity (NPA) and -6 degree head-down-tilt (HDT). HDT or NPA were randomly arranged with a recovery period of 6 months in between. 24 h-E of hormones varied widely among individuals. Values were higher in HDT compared to NPA. Assuming that the 24 h-E values are, beside being indicators for alterations in the number and metabolism of platelets. Also indicators of central SES, HDT condition seems to activate central SES in a higher degree compared to NPA. Therefore, changes in central SES might be involved in the mechanisms associated with space flight or microgravity, including possible maladaptations such as voluntary undernutrition. 相似文献
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航天飞行器中舷窗温度场及换热的研究:外部界面处于第三类非线性边界条件 总被引:2,自引:0,他引:2
本文采用控制容积法,光线踪迹法结合谱带模型,研究航天飞机返回大气层时舷窗硅玻璃的非稳态复合换热。文章给出了界面S_2处于第三类非线性边界条件下,舷窗硅玻璃内部的温度场和进入机舱内部的热流密度。计算结果表明,如不考虑硅玻璃内部的辐射作用,对温度场影响不太大,但对进入机舱内的热流密度将会产生很大的误差。 相似文献
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The EU 7th Framework Project FAST20XX [1] aimed to enlarge the foundations of suborbital high-speed transportation in a wide variety of fields. One of the key issues of this project was to outline a desirable regulatory framework that would best serve the interests of all European stakeholders in this new activity. 相似文献
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航天飞机的再入飞行走廊及再入飞行轨迹 总被引:1,自引:0,他引:1
在研究航天飞机再入返回问题时,确定再入飞行走廊和再入飞行轨迹是基础的研究问题之一。对于这方面的工作,参考文献[1]作了较详细的介绍。国内的一些作者在航天飞机方案论证时开始注意考虑这类重要的问题[2、3、4]。然而,他们所讨论的基本模型没有考虑地球自转对再入运动的影响。这种近似模型,对深入一步的方案论证就显得不能满足了。本文建立了一个精确的模型,给出与方案论证有关的仿真结果。 相似文献
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火星探测无动力借力飞行轨道研究 总被引:6,自引:1,他引:5
对无动力情形的借金星引力辅助变轨进行了研究,并完成了火星探测轨道的设计;首 先使用Jacobi积分得到了蒂塞朗准则,在利用速度矢量图对借力飞行轨道的特性进行分析后 ,得到了Williams提出的C3匹配法,证明了蒂塞朗准则和C3匹配的同一性;在 搜索借力飞行的可行性转移轨道中,采用C3匹配对借金星引力的火星探测轨道进行了 仿真,并对结果进行了分析,最后使用蒂塞朗准则对C3匹配的仿真结果进行了检验。 相似文献