可重复使用热防护材料应用与研究进展

可重复使用热防护系统是为高速重复使用飞行器而发展的关键性技术,涵盖了地球大气环境及非地球大气环境下的弹道式再入、高马赫数巡航等应用场景。根据现有高马赫数飞行器热防护现状,对高马赫数飞行器的主要热防护系统类型、特点和使用场景进行了简要介绍。在此基础上,结合国外里程碑式可重复使用飞行器（X-15、SR-71、航天飞机、X-33、X-37B、Spaceliner等）,梳理了可重复使用热防护材料的应用与研究进展,论述了代表性可重复使用热防护材料的发展、性能、研制进度、特点及应用前景。对国外在可重复使用热防护材料研制中的设计及发展思路,以及所存在的主要问题进行了总结归纳,为可重复使用热防护材料未来的发展提供了思路。     

A null frame for spacetime positioning by means of pulsating sources

We introduce an operational approach to the use of pulsating sources, located at spatial infinity, for defining a relativistic positioning and navigation system, based on the use of four-dimensional bases of null four-vectors, in flat spacetime. As a prototypical case, we show how pulsars can be used to define such a positioning system. The reception of the pulses for a set of different sources whose positions in the sky and periods are assumed to be known allows the determination of the user’s coordinates and spacetime trajectory, in the reference frame where the sources are at rest. We describe our approach in flat Minkowski spacetime, and discuss the validity of this and other approximations we have considered.     

用于直升机现场计量的低频振动校准技术

本文面向直升机健康与使用监测系统(HUMS)的现场计量保障需求,针对其中振动传感器在低频段尚无法实现现场校准的现状,提出了基于直线电机驱动技术的便携式低频振动校准技术方案。该方案利用高精度直线电机构造低频标准振动源,采用稳定性高的石英挠性加速度计作为标准加速度计,具有体积小、精度高、现场环境适应性好的特点,非常适用直升机HUMS的现场计量保障。根据不确定度评估结果,该方案能够实现0.5Hz～20Hz频率范围,0.01m/s~2～20m/s~2加速度范围内不超过1%的校准不确定度(k=2)。     

低轨卫星通信系统地面核心网设计与仿真

文章针对无星际链路的低轨卫星通信系统，利用OPNET软件设计了低轨卫星通信系统在透明转发模式下的核心网构成，并进行了性能仿真。首先介绍核心网的构成、功能和拓扑，在此基础上实现了呼叫处理和切换的仿真，统计了呼叫时延、切换时延等性能指标，分析了仿真结果，为低轨道卫星通信系统的设计奠定了一定的参考价值。     

一类滞后不确定相似组合系统的分散控制

本文给出了一个使滞后的相似组合大系统镇定的分散鲁棒控制器的设计方法。不确定性是时变的,是以不确定参数出现在每个子系统中,而存在于互联项中的不确定性假设可能知道它的边界,当系统具有某种特征时,简化了一般控制器的设计。     

“Modular Biospheres” – New testbed platforms for public environmental education and research

This paper will review the potential of a relatively new type of testbed platform for environmental education and research because of the unique advantages resulting from their material closure and separation from the outside environment. These facilities which we term “modular biospheres”, have emerged from research centered on space life support research but offer a wider range of application. Examples of this type of facility include the Bios-3 facility in Russia, the Japanese CEEF (Closed Ecological Experiment Facility), the NASA Kennedy Space Center Breadboard facility, the Biosphere 2 Test Module and the Laboratory Biosphere. Modular biosphere facilities offer unique research and public real-time science education opportunities. Ecosystem behavior can be studied since initial state conditions can be precisely specified and tracked over different ranges of time. With material closure (apart from very small air exchange rate which can be determined), biogeochemical cycles between soil and soil microorganisms, water, plants, and atmosphere can be studied in detail. Such studies offer a major advance from studies conducted with phytotrons which because of their small size, limit the number of organisms to a very small number, and which crucially do not have a high degree of atmospheric, water and overall material closure. Modular biospheres take advantage of the unique properties of closure, as representing a distinct system “metabolism” and therefore are essentially a “mini-world”. Though relatively large in comparison with most phytotrons and ecological microcosms, which are now standard research and educational tools, modular biospheres are small enough that they can be economically reconfigured to reflect a changing research agenda. Some design elements include lighting via electric lights and/or sunlight, hydroponic or soil substrate for plants, opaque or glazed structures, and variable volume chambers or other methods to handle atmospheric pressure differences between the facility and the outside environment.     

A joint mid-course and terminal course cooperative guidance law for multi-missile salvo attack

Salvo attacking a surface target by multiple missiles is an effective tactic to enhance the lethality and penetrate the defense system. However, existing cooperative guidance laws in the mid-course or terminal course are not suitable for long- and medium-range missiles or stand-off attacking. Because the initial conditions of cooperative terminal guidance that are generally generated from the mid-course flight may not lead to a successful cooperative terminal guidance without proper mid-course flight adjustment. Meanwhile, cooperative guidance in the mid-course cannot solely guarantee the accuracy of a simultaneous arrival of multiple missiles. Therefore, a joint mid-course and terminal course cooperative guidance law is developed. By building a distinct leader-follower framework, this paper proposes an efficient coordinated Dubins path planning method to synchronize the arrival time of all engaged missiles in the mid-course flight. The planned flight can generate proper initial conditions for cooperative terminal guidance, and also benefit an earliest simultaneous arrival. In the terminal course, an existing cooperative proportional navigation guidance law guides all the engaged missiles to arrive at a target accurately and simultaneously. The integrated guidance law for an intuitive application is summarized. Simulations demonstrate that the proposed method can generate fast and accurate salvo attack.     

基于电流注入法的加速度表测试方法研究

针对不同结构的加速度表 ,从理论上研究了利用电流注入法模拟加速度表运动特性的方法 ,研究了加速度表接入闭环测试系统后的相关问题 ,为加速度表的动态测试提供了新的方法     

系统思想在航天企业全面风险管理实施中的应用

介绍了风险管理国际标准ISO31000的核心内容——风险管理框架,以及系统思想的基本理念;以系统观点和方法为基础,对国际标准在航天企业全面风险管理中的应用进行了探讨。通过对全面风险管理工作的系统分解与集成,并以其中的"环境"分系统建设为例,进一步细分工作内容,与现有业务管理工作相结合,探索出全面风险管理工作在航天企业落地的基本路径。     

Spatial approaches to moons from resonance relative to invariant manifolds

In this study, the final approach to a moon or other body from resonance is explored and compared to the invariant manifolds of unstable periodic orbits. It is shown that the stable manifolds of planar Lyapunov orbits can act as a guide for the periods or resonances that are required for the final approach in both the planar and spatial problems. Previously developed techniques for the planar problem are expanded for use with resonances and used for comparison with trajectories approaching a moon from these resonances. A similar technique is then used for exploring the relationship of invariant manifolds to approach trajectories in the spatial problem. It is shown that the invariant manifolds of unstable periodic orbits provide insight into the trajectory design, and they can be used as a guide to the more direct approach trajectories.