Satellite collision probability estimation using polynomial chaos expansions

This paper presents the application of polynomial chaos (PC) to estimating the probability of collision between two spacecraft. Common methods of quantifying this probability for conjunction assessment use either Monte Carlo analyses or include simplifying assumptions to improve tractability. A PC expansion, or PCE, provides a means for approximating the solution to a large set of stochastic ordinary differential equations, which includes orbit propagation. When compared to Monte Carlo methods, non-intrusive, i.e., sampling-based, PCE generation techniques may greatly reduce the number of orbit propagations required to approximate the possibly non-Gaussian, a posteriori probability density function. The presented PC-based method of computing collision probability requires no fundamental simplifying assumptions, and reduces the computation time compared to Monte Carlo. This paper considers two cases where the common conjunction assessment assumptions are no longer valid. The results indeed demonstrate a reduction in computation time when compared to Monte Carlo, and improved accuracy when compared to simplified techniques.     

多场环境下涡轮盘的强度与振动安全性仿真优化研究

涡轮盘作为发动机的关键部件,工作在高温、高负荷、高转速及大振动的环境中,由强度与振动问题引起的轮盘破坏是发动机的常见故障之一.本文采用气热固耦合的方法,对某发动机一级涡轮盘进行有限元结构与模态仿真,并采用相应的静强度与振动准则进行安全性分析.结果表明,轮盘中心孔处的静强度安全余量较小,且二节径、三节径耦合频率与工作频率的避开率小于10％,工作时存在共振危险.经过结构优化,将轮盘厚度增加25％,同时根部局部加厚,中心孔处应力水平显著降低,各节径耦合共振频率的避开率均大于20％,涡轮盘的安全性满足要求.     

基于分层体系的现代作战飞机方案评估

针对目前作战飞机方案评估中体系与方法的不足,依据飞机发展的时序性和评估内容的细化程度,确定了现代作战飞机方案评估的5个层次,它们分别为综合作战能力层、综合作战效能层、综合使用效能层、综合使用效费层和方案评价决策层.在分析各评估层特性的基础上,建立了各评估层的细化指标体系,改进和完善了各评估层的理论模型和计算方法,通过现...     

基于混合动态系统理论的事故过程建模方法

为了研究系统事故机理,建立有效的事故过程模型,分析了事故过程的特征,指出其呈现离散与连续动态行为交互的混合特性.针对现有事故过程建模方法在描述该混合特性时的不足,提出了基于混合动态系统理论的建模方法,建立了事故过程的混合自动机模型,在Simulink/Stateflow环境下进行仿真.实现了事故过程的连续机理与状态运转...     

Space Debris Reentry Analysis Methods and Tools

The reentry of uncontrolled spacecraft may be broken into many pieces of debris at an altitude in the range of 75-85 km. The surviving fragments could pose great hazard and risk to ground and people. In recent years, methods and tools for predicting and analyzing debris reentry and ground risk assessment have been studied and developed in National Aeronautics and Space Ad-ministration (NASA), European Space Agency (ESA) and other organizations, including the group of the present authors. This paper reviews the current progress on this topic of debris reentry briefly. We outline the Monte Carlo method for uncertainty analysis, breakup prediction, and parameters affecting survivability of debris. The existing analysis tools can be classified into two categories, i.e. the object-oriented and the spacecraft-oriented methods, the latter being more accurate than the first one. The past object-oriented tools include objects of only simple shapes. For more realistic simulation, here we present an object-oriented tool debris reentry and ablation prediction system (DRAPS) developed by the present authors, which introduces new object shapes to 15 types, as well as 51 predefined motions and relevant aerodynamic and aerothermal models. The aerodynamic and aerothermal models in DRAPS are validated using direct simulation Monte Carlo (DSMC) method.     

基于飞行超限事件的飞行安全评估模型

为了提高航空公司对飞行安全的管理水平,建立了影响飞行安全的飞行超限事件层次结构模型,去除评价指标中定性的描述,使指标通过飞行超限事件发生率进行量化。利用改进的层次分析法（AHP）一致性校验算法,使AHP在给定的判断矩阵下,不需经过一致性检验,能够直接给出所要求的权重值,保证判断矩阵的一致性。通过对飞行超限事件历史数据进行飞行超限事件发生率统计,利用静态评价和动态评价分析飞行安全,并在．NET平台实现了评估模型,仿真实例验证结果表明了该方法的有效性。     

一种基于事故树的安全风险定量评估方法

针对目前安全风险评估方法的不足,提出了基于事故树的飞机部件安全风险定量评估方法.首先采用布尔代数理论对事故树进行逻辑表述,通过概率重要度表示部件故障的后果严重度,在此基础上对飞机部件的危险度进行计算,解决了当前安全风险定量评估的难题.实例证明,该方法能够较为准确地检验飞机部件对飞行安全的影响.     

发动机孔探数据在健康管理与安全运行预测中的应用

基于完善目前航空发动机健康管理体系的目的．探讨了如何利用发动机孔探数据进行发动机健康管理和安全运行预测,同时提出了开展该领域研究与实践的一些建议。     

中国大涵道比涡扇发动机适航技术初步研究

对适航技术在中国大涵道比发动机上的应用进行了初步分析和探索,结合发动机研制情况,对适航工作的开展和存在问题进行了初步研究。     

航空发动机健康评估技术综述

健康评估技术是航空发动机健康管理的关键技术之一。详细阐述了航空发动机健康评估的研究内容,重点分析了发动机气路性能、结构以及机械系统健康评估的特点,并指出了开展航空发动机健康评估关键技术研究的重要性。