空间电子设备意外跌落冲击响应分析

文章针对空间部件意外跌落事件,利用冲击分析原理,结合具体跌落时的路面和部件包装箱刚度,对空间部件的冲击加速度载荷进行了分析,为评价意外冲击事件是否影响产品性能提供了数值依据。     

卫星太阳电池阵在板展开阶段的撞击特性研究

研究了卫星太阳电池阵在板展开阶段的撞击特性,导童重要性一多体系统的动力学方程,介绍了撞击力的计算方法,计算了太阳电池阵在撞击阶段的撞击力和一些特殊节点的加速度和变化规律,计算结果表明,各点的撞击力在不同的时刻达到峰值,说明柔性板在撞击时发生了扭转,此外还发现靠近撞击处的节点的加速度在撞击瞬间比其它节点大,通过冲击波的传播引起外侧板的边界上节点的加速度不断上下振动,可以解释外侧帆板在撞击后上下、左右     

Trajectory reshaping based guidance with impact time and angle constraints

This study presents a novel impact time and angle constrained guidance law for homing missiles. The guidance law is first developed with the prior-assumption of a stationary target, which is followed by the practical extension to a maneuvering target scenario. To derive the closed-form guidance law, the trajectory reshaping technique is utilized and it results in defining a specific poly-nomial function with two unknown coefficients. These coefficients are determined to satisfy the impact time and angle constraints as well as the zero miss distance. Furthermore, the proposed guidance law has three additional guidance gains as design parameters which make it possible to adjust the guided trajectory according to the operational conditions and missile’s capability. Numerical simulations are presented to validate the effectiveness of the proposed guidance law. ? 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).     

卫星太阳能帆板的撞击问题

本文研究卫星帆板展开过程中的撞击问题，用子结构方法和单向递推组集方法行到经铰坐标和柔性体模态坐标为系统广义坐标的撞击阶段柔性多体系统的动力学方程，由与撞击有关约束方程的Ｌａｇｒａｎｇｅ乘子导出撞击力的计算公式，计算了卫星帆板在撞击过程中撞击力的最大值和卫星姿态角速度的变化规律。计算结果表明，对柔性体之间的碰撞，卫星姿态角速度在变化过程中呈现上下波动的趋势。     

空间碎片撞击概率分析软件开发、校验与应用

航天器空间碎片撞击概率分析软件是我国独立设计开发的"空间碎片防护设计软件包"的重要组成部分。本文简要介绍了撞击概率分析软件的主要功能模块组成;重点对该软件的正确性进行了国际标准工况校验,并给出工程应用算例。     

Nuclear fragmentation database for GCR transport code development

A critical need for NASA is the ability to accurately model the transport of heavy ions in the Galactic Cosmic Rays (GCR) through matter, including spacecraft walls, equipment racks, etc. Nuclear interactions are of great importance in the GCR transport problem, as they can cause fragmentation of the incoming ion into lighter ions. Since the radiation dose delivered by a particle is proportional to the square of (charge/velocity), fragmentation reduces the dose delivered by incident ions. The other mechanism by which dose can be reduced is ionization energy loss, which can lead to some particles stopping in the shielding. This is the conventional notion of shielding, but it is not applicable to human spaceflight since the particles in the GCR tend to be too energetic to be stopped in the relatively thin shielding that is possible within payload mass constraints. Our group has measured a large number of fragmentation cross sections, intended to be used as input to, or for validation of, NASA’s radiation transport models. A database containing over 200 charge-changing cross sections and over 2000 fragment production cross sections has been compiled. In this report, we examine in detail the contrast between fragment measurements at large acceptance and small acceptance. We use output from the PHITS Monte Carlo code to test our assumptions using as an example ⁴⁰Ar data (and simulated data) at a beam energy of 650 MeV/nucleon. We also present preliminary analysis in which isotopic resolution was attained for beryllium fragments produced by beams of ¹⁰B and ¹¹B. Future work on the experimental data set will focus on extracting and interpreting production cross sections for light fragments.     

Extraterrestrial environmental impact assessments – A foreseeable prerequisite for wise decisions regarding outer space exploration,research and development

Although existing international instruments such as the Outer Space Treaty and Moon Agreement generally express sentiments for minimizing missions' extraterrestrial environmental impacts, they tend to be limited in scope, vague and generally unenforceable. There is no formal structure for assessing how and to what extent we affect those environments, no opportunity for public participation, no uniform protocol for documenting and registering the effects of our actions and no requirement to mitigate adverse impacts or take them into consideration in the decision-making process. Except for precautions limiting forward biological contamination and issues related to Earth satellites, environmental impact analysis, when done at all, remains focused on how missions affect the Earth and near-Earth environments, not how our actions affect the Moon, Mars, Europa, comets and other potential destinations. Extraterrestrial environmental impacts are potentially counterproductive to future space exploration, exploitation and scientific investigations. Clear, consistent and effective international protocols guiding a process for assessing such impacts are warranted. While instruments such as the US National Environmental Policy Act provide legally tested and efficient regulatory models that can guide impact assessment here on Earth, statutory legal frameworks may not work as well in the international environment of outer space. A proposal for industry-driven standards and an environmental code of conduct based, in part, on best management practices are offered for consideration.     

耐候钢活性MAG 焊接接头组织及冲击断口特征

针对焊枪可达性差等难熔合焊接结构,提出了活性熔化极气体保护焊焊接新方法。该方法可增加焊接熔深,改善难熔焊接结构的熔合不良,获得高质量的焊接接头。采用活性熔化极气体保护焊接对耐候钢进行了工艺试验,对焊接接头组织、冲击韧性及断口形貌进行分析。结果表明,相对熔化极气体保护焊,活性熔化极气体保护焊在同等焊接热输入下熔深显著增加,焊缝表面及焊接接头内部质量高,接头组织更为细化,过热区析出碳化物相也更加细小弥散,冲击韧性提高,冲击断口韧性特征更明显。     

The Coma of Comet 9P/Tempel 1

As comet 9P/Tempel 1 approaches the Sun in 2004–2005, a temporary atmosphere, or “coma,” will form, composed of molecules and dust expelled from the nucleus as its component icy volatiles sublimate. Driven mainly by water ice sublimation at surface temperatures T > 200 K, this coma is a gravitationally unbound atmosphere in free adiabatic expansion. Near the nucleus (≤ 10² km), it is in collisional equilibrium, at larger distances (≥10⁴ km) it is in free molecular flow. Ultimately the coma components are swept into the comet’s plasma and dust tails or simply dissipate into interplanetary space. Clues to the nature of the cometary nucleus are contained in the chemistry and physics of the coma, as well as with its variability with time, orbital position, and heliocentric distance. The DI instrument payload includes CCD cameras with broadband filters covering the optical spectrum, allowing for sensitive measurement of dust in the comet’s coma, and a number of narrowband filters for studying the spatial distribution of several gas species. DI also carries the first near-infrared spectrometer to a comet flyby since the VEGA mission to Halley in 1986. This spectrograph will allow detection of gas emission lines from the coma in unprecedented detail. Here we discuss the current state of understanding of the 9P/Tempel 1 coma, our expectations for the measurements DI will obtain, and the predicted hazards that the coma presents for the spacecraft. An erratum to this article is available at .