载人航天飞行任务USB测控网优化配置解决方案

以我国载人航天飞行任务为背景,针对历次任务中USB测控网使用上出现的测站任务准备时间过长、与其他任务测站使用相冲突、测站使用效率不高等问题,在统计和分析实战任务数据的基础上,给出了一个载人航天飞行任务USB测控网优化配置的可行性方案,并提出了任务中选择测站的原则和测站配置确定流程,以期能够在今后的任务中更为合理地分配有限的USB测控网资源,提高其使用效率。     

多指标约束下考虑报废的可修复备件携行方案优化

针对任务期间普遍存在的故障件报废和备件多指标约束问题,提出了多层级装备的可用度近似评估方法及携行备件方案优化方法。首先通过忽略维修时间将考虑报废率的多层级可修件转化为单层级消耗件,进而利用伽马分布的可加性建立装备可用度评估模型。在此基础上以装备可用度、备件总质量为约束指标,以备件总体积最低为目标构建多约束备件优化模型。模型求解过程中引入拉格朗日因子,并采用边际算法对约束因子进行动态调整。算例中通过与仿真结果的对比、分析得出：当维修时间取值在部件等效平均寿命的一半以内时,提出的近似方法合理可行,平均误差小于5%。     

Cometary probes

The studies carried out in the U.S.A. and in Europe to investigate the possibilities and the scientific merit of a cometary probe are surveyed and reviewed. The scientific objectives of such a mission are given and the conditions are stated which a feasible comet must fulfill. Further, proposals of the different groups for the instrumentation of the probe are discussed.Though not all the groups propose the same comets for a first mission, due to different selection criteria, they agree that a mission to a new, non-periodic comet is out of consideration at present, and that a mission to a periodic comet, though possible in principle, presents various difficulties with respect to orbit accuracy and energy requirements. It is emphasized that a mission to Comet Halley in 1986 would be of special value.     

Possible Future Use of Laser Gravity Gradiometers

With the GRACE mission under way and the GOCE mission well along in the design process, detailed questions concerning the type of future mission that may follow them have arisen. It is generally agreed that determining the time variations in the Earth's gravity field with as high spatial and temporal resolution as is feasible will be the main driver for such a mission. The possible use of laser heterodyne measurements between separate satellites in such a mission has been discussed by a number of people. The first suggestion of emphasizing time variation measurements in a laser mission was the TIDES concept presented in 1992 by Colombo and Chao. Then, in 2000, a GRACE Follow-On mission using laser measurements between two drag-free satellites was discussed by Watkins el al. (2000). More recently, the possibility of utilizing laser measurements between more than two satellites in order to determine two or more components of the gravity gradient tensor simultaneously has been proposed by Balmino. This approach may be desirable in order to reduce the aliasing of time variations between geopotential terms of different degree and order, as well as to improve the resolution in longitude, despite the cost of the additional satellites. In this paper, we discuss specific possible mission geometries for measuring the two diagonal in-plane components of the gravity gradient tensor simultaneously. This could be done, for example, by laser heterodyne measurements between two pairs of satellites in coplanar and nearly polar orbits. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fast calculation method for mission opportunities in orbital interception and rendezvous problems

This paper proposes a fast calculation method to solve all mission opportunities for orbital interception and orbital rendezvous under the impulse-magnitude constraint. Different from the existing search methods, the proposed method does not need to solve Lambert’s problem in the whole process. Three cases are considered for either departure time or transfer time being free, or both being free. For fixed departure time, the feasible windows of transfer time are obtained by solving a single-variable nonlinear equation only of terminal true anomaly. Similarly, for fixed interception (or rendezvous) time, the feasible windows of departure time are obtained. For free departure time and free transfer time, all mission opportunities are obtained by using a one-dimensional search strategy. The hyperbolic-transfer and the multiple-revolution cases are also analyzed. Numerical results show that the proposed method is superior to the typical pork-chop plot method and the two-dimensional launch window method in computational time.     

Performance deterioration modeling and optimal preventive maintenance strategy under scheduled servicing subject to mission time

Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterioration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the system expected life-cycle cost per unit time and a constraint on system survival probability for the duration of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strategy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system.     

基于Bayes理论的航空发动机涡轮叶片维修决策

为了更可靠、更经济地实施航空发动机涡轮叶片维修决策,对Bayes统计推断理论在维修中的应用进行了探索。通过仿真试验,对比分析了维修人员在常规情况下根据维修经验和通过采样对叶片维修策略的选择。试验结果表明,基于Bayes统计推断理论的方法,对于航空公司决策者或维修人员进行维修决策是可行的和方便的。     

基于MAS仿真的保障机构维修保障能力评估指标研究

对于由大量不同型号舰艇所构成的舰艇编队,其维修保障系统中涉及各类维修保障资源,如人力、备件、设备、设施等,为了确保舰艇编队具有较高的战备完好性和任务成功性,这些维修保障力量一方面应具有很强的自身能力,另一方面还应具有很强的协同工作的能力。文章针对舰艇编队的维修保障问题,分析维修保障力量的各影响因素,在协同工作的背景下,采用Multi-Agent System(MAS)仿真构架,对这些维修保障力量建立评估指标,建立评估指标,达到资源投入少、保障时间短、保障效果好的保障目标。     

民用飞机维修性参数选取和指标确定方法研究

民用飞机维修性参数选取和指标确定是维修性设计的基础工作之一,为了反映出民用飞机的维修性、运营费用和维修人力等方面的目标,需要选择合适的维修性参数并确定维修性指标。国产民用飞机由于缺少研制经验和设计资料,无法使用成熟方法进行维修性参数选取和指标确定,针对这一问题进行研究。结合民用飞机的设计特点阐述了民用飞机维修性参数的选取方法,通过综合权衡民用飞机设计中各影响因素和维修性参数有效性,从与维修时间相关、与维修工时相关、与维修成本相关的三类参数中选取适当的民用飞机维修性参数。针对民用飞机设计现状,明确维修性指标的确定依据和具有实用性的方法,以使民用飞机具有良好的维修性。解决了国产民用飞机维修性参数选取和指标确定工作无参考依据的问题,为民用飞机维修性参数选取和指标确定提供了一条可行途径。     

固定翼反潜机浮标阵监听飞行航路规划研究

本文结合工程实际应用,研究了固定翼反潜机对浮标阵监听飞行航路规划问题。分析了浮标阵存在公共监听区域的条件,对于不能整体监听覆盖的浮标阵,提出了监听航路的评价指标。针对固定翼反潜机执行监听任务时,属于近距离航路规划范畴,飞行航路受载机机动转弯性能约束的影响较为显著,对监听航路采用了一定转弯策略,并用遗传算法搜索生成监听航路,取得了较好的效果。     

共因失效条件下多状态系统选择性维修优化

共因失效（CCF）广泛存在于多状态系统（MSS）中,研究共因失效条件下多状态系统的维修优化问题,对于提高系统任务成功概率、降低故障损失具有重要意义。考虑多状态系统、任务剖面和随机共因失效的模糊特性,采用模糊马尔可夫模型（FMM）和模糊通用生成函数（FUGF）法,建立了模糊随机共因失效条件下模糊多状态系统（FMSS）任务成功概率评估解析模型（AM）,采用Monte Carlo仿真（MCS）方法对模型进行了验证;考虑维修费用约束,建立了模糊随机共因失效条件下模糊多状态系统选择性维修优化模型,为生成最优维修方案提供支持,结合实际案例,分析了随机共因失效对选择性维修优化和系统各状态的模糊概率的影响,验证了模型的有效性。研究结果表明,模糊随机共因失效和各模糊参数的α水平截集可能会影响选择性维修优化的结果,且忽略模糊随机共因失效会高估系统任务成功概率。     

复杂可修系统可信度建模中任务维修度计算的统计推断方法

在设定每一部件的致命性故障率为常数并在确定出各部件任务修复时间置信上限的基础上,通过对可能发生的多次致命性故障事件的概率状态描述,得到了部件故障率与系统可信度的定量关系,进而依据这一可信度的建模原理归纳出不考虑任务修复时间的具体分布类型时复杂可修串联系统可信度的计算方法,同时也给出了任务维修度的统计推断表达式;最后,以典型的 ４ 部件串联可修系统为例,探讨了致命性故障次数、允许任务修复时间、部件任务修复时间的不同置信上限等的变化对系统可信度的影响,并论证了系统可靠性、维修性和保障性与可信度的关系。     

Optimal air-launching rocket design using system trades and a multi-disciplinary optimization approach

Compared with the conventional ground rocket launching, air-launching has many advantages. However, a comprehensive and integrated system design approach is required because the physical geometry of air launch vehicle is quite dependent on the installation limitation of the mother plane. For the selection of the best system alternative, a trade study for the first stage engine type and launching speeds is performed using a sequential optimization technique, confirming the feasibility of the baseline air-launching rocket. Then, a system design has been performed using the multi-disciplinary feasible (MDF) design optimization method. Analysis modules include mission analysis, staging, propulsion analysis, configuration, weight analysis, aerodynamics analysis and trajectory analysis. As a result of multi-disciplinary system optimization, a supersonic air launching rocket with total mass of 1244.9 kg, total length of 6.36 m, outer diameter of 0.60 m has been successfully designed to launch a satellite of 7.5 kg to the 700 km circular orbit.     

A multi-agent based intelligent configuration method for aircraft fleet maintenance personnel

A multi-agent based fleet maintenance personnel configuration method is proposed to solve the mission oriented aircraft fleet maintenance personnel configuration problem. The mainte- nance process of an aircraft fleet is analyzed first. In the process each aircraft contains multiple parts, and different parts are repaired by personnel with different majors and levels. The factors and their relationship involved in the process of maintenance are analyzed and discussed. Then the whole maintenance process is described as a 3-layer multi-agent system （MAS） model. A com- munication and reasoning strategy among the agents is put forward. A fleet maintenance personnel configuration algorithm is proposed based on contract net protocol （CNP）. Finally, a fleet of 10 aircraft is studied for verification purposes. A mission type with 3 waves of continuous dispatch is imaged. Compared with the traditional methods that can just provide configuration results, the proposed method can provide optimal maintenance strategies as well.     

Coordinated Continual Planning Methods for Cooperating Rovers

Eight evaluation metrics are used to compare and contrast three coordination schemes for a system that continuously plans to control collections of rovers (or spacecraft) using collective mission goals instead of goals or command sequences for each spacecraft. These schemes use a central coordinator to either: 1) micromanage rovers one activity at a time; 2) assign mission goals to rovers; or 3) arbitrate mission goal auctions among rovers. A self-commanding collection of rovers would autonomously coordinate itself to satisfy high-level science and engineering goals in a changing partially understood environment - making the operation of tens or even a hundred spacecraft feasible     

Optimization of the tether-assisted return mission of a guided re-entry capsule

This paper presents the mission analysis of a tether-assisted payload retrieval from the International Space Station (ISS). The objective is to assess all relevant phases of such a mission in order to allow a comparison with a conventional mission employing a propulsive deorbitation. The controlled tether deployment procedure and the guided return flight of the released re-entry capsule are optimized. A preferable deployment strategy is identified that allows for favorable entry conditions and low flight loads. The optimal deployment trajectories serve as a basis for an optimal dynamic regulator. This approach is extended towards an adaptive concept, where artificial neural networks are applied to deployment control. For the guidance of the capsule a predictive concept is proposed that is based on the optimal re-entry trajectories identified previously. By applying these concepts, the attainable landing accuracy during return amounts to an average of 5 km, and the application of the tether system exhibits overall system mass advantages. This demonstrates that the tether-assisted return mission is a competitive alternative.     

Scheme design of the CHANG’E-5T1 extended mission

Flight schemes for the CHANG’E-5T1 extended mission are investigated in this paper. In the flight scheme and trajectory design, the remaining propellant of the CHANG’E-5T1 mission is utilized. The CHANG’E-5T1 mission is firstly introduced with feasible flight goals derived based on the terminal trajectory and satellite status. The flight schemes are designed to include a lunar return and the libration points in the Sun-Earth/Moon and Earth-Moon systems, with an emphasis on the Earth-Moon triangle libration point thus far unexplored. Secondly, three schemes are proposed for the CHANG’E-5T1 extended mission with different flight goals. The direct libration point orbit transfer and injection method is adopted to solve the issue in the transfer trajectory design. Furthermore, an innovative concept is proposed to transfer from the Earth-Moon collinear libration point to the triangle point using the Sun-Earth/Moon libration point. Finally, the merits and drawbacks of the three schemes are discussed in terms of flight time, control energy and frequency, flight distance, and goal value. As a result, the scheme including a lunar return and the Earth-Moon L2 libration point is selected for the CHANG’E-5T1 extended mission. A flight to the Earth-Moon libration point is achieved, replicating the achievement of the ARTEMIS mission.     

Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA

In this study, a process for establishing design requirements and selecting alternative con-figurations for the conceptual phase of aircraft design has been proposed. The proposed process uses system-engineering-based requirement-analysis techniques such as objective tree, analytic hier-archy process, and quality function deployment to establish logical and quantitative standards. Moreover, in order to perform a logical selection of alternative aircraft configurations, it uses advanced decision-making methods such as morphological matrix and technique for order prefer-ence by similarity to the ideal solution. In addition, a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight perfor-mance of the selected configurations. The present process has been applied for a two-seater very light aircraft (VLA), resulting in a set of tentative design requirements and two families of VLA configurations: a high-wing configuration and a low-wing configuration. The resulting set of design requirements consists of three categories: customer requirements, certification requirements, and performance requirements. The performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer requirements. The flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA.     

Electric space propulsion systems

Active development of electric thrustors began 10 years ago. Today, several kinds of thrustors have achieved efficiencies above 90 % and lifetimes of several thousand hours. The following article derives the basic theory of electric thrust production at constant exhaust velocity, and at variable exhaust velocity programmed for optimum vehicle performance. Electrothermal or arcjet; electrostatic or ion; and electrodynamic or plasma thrustors are described. At the present time, ion thrustors of the electron bombardment and of the surface ionization types are the most promising systems. Electric power in space may be generated by solar cells or nuclear-electric generators. It is expected that the incore thermionic converter will eventually be the preferred system. A variety of missions with electric propulsion systems appear feasible and highly desirable, among them orbital station keeping, attitude control, planetary probes, solar and out-of-the-ecliptic probes, deep-space probes, and manned Mars and Venus exploration. For each mission, a careful systems-design study must be made, which will provide the optimum selection of thrustor type, thrust level, exhaust velocity, thrust program, power source, trajectory, and flight plan.     

人工智能在航天飞行任务规划中的应用研究

 在航天飞行任务中,如何设计航天器的飞行过程,如何确定地面对航天器的控制操作,如何制定飞行控制计划等,是地面飞行控制中心面临的重大问题,也是航天飞行任务规划所要解决的基本问题。在充分认识和把握人工智能基本原理、方法和技术的基础上,提出了一个基于规则演绎和状态演化的生长式推理模型,并对模型的特性进行了详细讨论,然后导出了该模型在航天飞行任务规划问题中的具体形式,从而成功地解决了航天任务自动规划的难题。通过在实际航天任务中的应用和验证,不仅证明该模型和方法是正确的、可行的和高效的,而且证明人工智能在航天飞行任务规划中有着广阔的应用前景。