星间光通信中BER的口径自适应控制法

从接收机的比特误码率与发射机的振动关系出发,采用OOK调制方式,以APD为光电探测器,推导得到了描述发射机天线口径与发射机振动关系的数学模型。针对比特误码率(BER)随振动幅值增加而上升的问题,提出了用发射天线口径与自适应方法控制BER的解决方案。用MATLAB6.5计算得到了自适应和标准条件下BER与跟踪系统信噪比的关系曲线。计算结果表明,采用天线口径自适应方法可将BER值控制在设计要求以下。     

神舟号载人飞船船载测控通信分系统

介绍了神舟号载人飞船船载测控通信分系统中统-S波段（USB）、C波段、遥测、遥控、图像、话音、超短波（VHF）、短波（HF）和天线等子系统的组成、主要功能与特点，以及跟踪测轨、话音通信、遥控、遥测和天线等的可靠性设计。地面试验和飞行试验结果表明，该测控通信分系统都完成了测量任务，完全能满足载人航天工程的高要求。     

A Geosynchronous Orbit Search Strategy

Since more than 10 years there is evidence that small-size space debris is accumulating in the geosynchronous orbit (GEO), probably as the result of breakups. Two break-ups have been reported in GEO. The 1978 break-up of an EKRAN 2 satellite, SSN 10365, was identified in 1992, and in 1992 a Titan 3C Transtage, SSN 3432, break-up produced at least twenty observable pieces. Subsequently several nations performed optical surveys of the GEO region in the form of independent observation campaigns. Such surveys suffer from the fact that the field of view of optical telescopes is small compared with the total area covered by the GEO ring. As a consequence only a small volume of the orbital element-magnitude-space is covered by each individual survey. Results from these surveys are thus affected by observational biases and therefore difficult to compare. This paper describes the development of a common search strategy to overcome these limitations. The strategy optimizes the sampling for objects in orbits similar to the orbits of the known GEO population but does not exclude the detection of objects with other orbital planes. A properly designed common search strategy clearly eases the comparison of results from different groups and the extrapolation from the sparse (biased) samples to the entire GEO environment.     

Tether Satellite System Collision Study

A study was performed to determine the probability of collision with resident space objects and untrackable debris for the tether component of the Tethered Satellite System (TSS) after it broke away from the Space Shuttle orbiter (mission STS-75) in February 1996. Both an analytical and a numerical approach were used in this study, and the results obtained with these two methods were found to be in good agreement. These results show that the deployed tether is expected to have been impacted by several particles 0.1mm or larger in size. The probability of collision with objects 10cm in size or larger was on the order of 10^–3 per month. Since the severed tether reentered within one month after deployment, the collision hazard to other objects while in orbit was small. The analytical methods used in this study are useful for tether collision evaluations in general.     

有风情况下半弹道式载人飞船返回轨道的计算方法

文中给出了有风情况下半弹道式载人飞船返回轨道的精确计算方法。     

Delta并联微操作手运动学的矢量法分析

利用矢量运算的方法,分析了三维平动Delta并联微操作手的运动学特性.基于雅可比矩阵的可逆性,研究了Delta并联机构的正逆运动奇异性问题. 研究表明,微操作手的雅可比矩阵中存在灵敏参数,灵敏参数的大小及方位影响着位移输入与输出间的关系;利用矢量运算方法进行运动学奇异性问题分析更为简洁和直接.     

航天器舷窗玻璃的强度检验方法和寿命预测

以断裂力学为基础,结合热钢化玻璃应力分布的特点,首次提出了热钢化玻璃的检验试验和寿命预测方法,为热钢化舷窗玻璃的强度检验提供了理论基础。分析示例的计算表明,即使通过相同的检验应力,在不同的使用环境中允许的使用应力是不同的;不同环境下,同样的使用应力,玻璃的使用寿命相差很大。     

建立航空发动机状态空间模型的修正方法

以阶跃输入响应进行模型的检验，提出了状态空间模型的修正方法：基于动态响应较好的状态空间模型，进行其矩阵B，D，F，G的修正，获得基于稳态修正的模型，解决了航空发动机状态空间模型检验与修正的问题。仿真表明，使用该方法修正的状态空间模型具有与原非线性数学模型完全一致的稳态响应和基本一致的动态过程响应。这种方法为航空发动机多变量数字电子控制器的设计奠定了强有力的基础。     

非线性主轴降维映射法在固体火箭发动机设计优化中的应用

为在二维或三维空间中表达固体火箭发动机高维设计空间,引入非线性主轴降维映射法对多维非线性设计优化问题进行降维处理。以某大型固体火箭发动机设计问题为例,将10变量4有效约束优化问题降维映射到二维空间进行研究,拟合的非线性主轴降维映射模型中,目标函数和约束函数的相对误差控制在1.5%以内。研究表明,非线性主轴降维映射法具有发现多变量非线性优化数学模型本征特性的特点,能对设计变量重要性排序;通过降维展示设计空间全景,为优化算法和优化初始点优选提供了直观、有力的工具;优化轨迹实时展示为优化算法性质研究及算法切换提供了依据;根据优化轨迹从优化结果在降维空间中的位置能够判断优化结果是否具有全局最优解特性。     

液体推进系统充填过程的有限元状态变量模型

研究了常温推进剂液体火箭发动机充填过程的建模问题。对推进剂充填管道系统进行有限元分割，应用基本守恒定律于充满推进剂的单元和充满气体的单元，两相单元则采用等效流容方程，建立了常温推进剂管道系统充填过程的有限元状态变量模型。模型面向液体推进系统动态过程控制与通用仿真。利用该模型，对一管道充填过程进行了仿真计算，给出了有关计算结果。