HTPB推进剂贮存寿命的理论预估

以ＨＴＰＢ推进剂化学老化机理及其氧化反应动力学为依据,导出了推进剂应变保留值与贮存老化时间的关系,由推进剂中氧化剂ＡＰ低温分解反应和ＨＴＰＢ固化体经反应的动力学参数,计算出了在不同应变保留值时的推进剂的贮存寿命。当推进剂的应变保留值在３０％～５０％之间时,其贮存寿命的理论计算值与高温加速老化实验值之间的相对误差小于１６％。     

Prediction of ionospheric total electron content using adaptive neural network with in-situ learning algorithm

The Ionospheric Total Electron Content is responsible for the group delay of the signals from the Navigation satellites. This delay causes ranging error, which in turn degrades the accuracy of position estimated by the receivers. For critical applications, single frequency receivers resort to Satellite Based Augmentation Systems in order to have improved accuracy and integrity. The performance of these systems in terms of accuracy can be improved if predictions of the delays are available simultaneously with real measurements. This paper attempts to predict the Total Electron Content using adaptive recurrent Neural Network at three different locations of India. These locations are selected at the magnetic equator, at the equatorial anomaly crest and outside the anomaly range, respectively. In-situ Learning Algorithm has been used for tracking the non-stationary nature of the variation. Prediction is done for different prediction intervals. It is observed that, for each case, the mean and root mean square values of prediction errors remain small enough for all practical applications. Analysis of Variance is also done on the results.     

CoRoT and Kepler results: Solar-like oscillators

The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.     

Reducing variability in short term orbital lifetime prediction

Within the last year three major re-entries occurred. The satellites UARS, ROSAT and Phobos-Grunt entered Earth’s atmosphere with fragments reaching the surface. Due to a number of uncertainties in propagating an object’s trajectory the exact place and time of a satellite’s re-entry is hard to determine. Major influences when predicting the re-entry time are the changing precision of the available orbital data, the satellite’s ballistic coefficient, the activity of the sun which influences the Earth’s atmosphere and the underlying quality of the atmospheric model. In this paper a method is presented which can reduce the variability in short-term orbital lifetime prediction induced by fluctuating orbital data accuracies. A re-entry campaign is used as a reference for this purpose. For a window of a few weeks before the re-entry the position data of a synthetic object is disturbed considering different degrees of orbital data errors. As a result different predictions will exist for the generated position data of a given day. Using a regression algorithm on the available data an average position is obtained, which is then used for the orbital lifetime prediction. The effect of this measure is a more consistent prediction of the orbital lifetime. The paper concludes with the comparison of the generated re-entry windows in various test cases for the original and the averaged data.     

Determining CME parameters by fitting heliospheric observations: Numerical investigation of the accuracy of the methods

Transients in the heliosphere, including coronal mass ejections (CMEs) and corotating interaction regions can be imaged to large heliocentric distances by heliospheric imagers (HIs), such as the HIs onboard STEREO and SMEI onboard Coriolis. These observations can be analyzed using different techniques to derive the CME speed and direction. In this paper, we use a three-dimensional (3-D) magneto-hydrodynamic (MHD) numerical simulation to investigate one of these methods, the fitting method of  and . Because we use a 3-D simulation, we can determine with great accuracy the CME initial speed, its speed at 1 AU and its average transit speed as well as its size and direction of propagation. We are able to compare the results of the fitting method with the values from the simulation for different viewing angles between the CME direction of propagation and the Sun-spacecraft line. We focus on one simulation of a wide (120–140°) CME, whose initial speed is about 800 km s⁻¹. For this case, we find that the best-fit speed is in good agreement with the speed of the CME at 1 AU, and this, independently of the viewing angle. The fitted direction of propagation is not in good agreement with the viewing angle in the simulation, although smaller viewing angles result in smaller fitted directions. This is due to the extremely wide nature of the ejection. A new fitting method, proposed to take into account the CME width, results in better agreement between fitted and actual directions for directions close to the Sun–Earth line. For other directions, it gives results comparable to the fitting method of Sheeley et al. (1999). The CME deceleration has only a small effect on the fitted direction, resulting in fitted values about 1–4° higher than the actual values.     

固体火箭发动机装药贮存寿命预测方法

针对固体火箭发动机装药贮存寿命预估的难题,开展了固体火箭发动机贮存可靠性、装药老化性能、药柱结构完整性分析等几个方面的研究,建立了GM-RBF网络模型、基于修正Ar-rhenius的交变温度预测模型、基于加速老化和结构完整性分析的装药贮存寿命预估模型,从不同角度来对装药贮存寿命进行组合预测.在此基础上,设计和开发了预测系统,通过实验数据和仿真分析,得到实例的装药贮存寿命区间为10.5～13.2y.研究表明:这种组合预测的方法避免了单一算法的局限性,提高了预测精度.     

影响奔月飞行器定轨精度的误差源分析

以探月工程为背景,讨论在现有测控网分布、观测弧段以及尽可能接近真实情况的误差源等前提下,利用仿真模拟方法对影响奔月飞行器定轨精度的误差源进行分析。重点考察了观测量精度、初始时刻先验轨道误差、测量船点位误差以及观测资料类型等对奔月飞行器定轨精度的影响。结果表明提高观测量精度和减小测量船点位误差将有助于提高定轨精度,以及采用USB测距、测速和VLBI时延、时延率联合定轨能够提高定轨和轨道预报精度。     

航天器数据预测中的因果关系调整技术应用研究

在航天领域，预测参数不但受其自身时序变化的影响，也普遍受到关联因素的交叉影响。因果因素的影响也需要在时序预测过程中被考虑，该类问题被列入因果调整技术当中。为了更全面地反映航天器参数变化的实际情况，提出了一种基于层次分析法（AHP）的因果调整方法。该方法提供了因果因素的判断调整方法，并将调整系数应用于时序模型预测的修正。最终，建立了一个因果与时序预测有机结合的预测体系。     

航天器故障诊断和预测天地一体化集成系统

在轨航天器和地面航天飞控中心天地2个系统缺乏相互支持和配合，是导致对航天器故障诊断和预测能力不足的重要因素之一。为了提高航天器故障诊断和预测的有效性、可靠性和准确性，需要将天地2个系统集成为一个整体（天地一体化系统）。设计了航天器故障天地一体化集成诊断和预测系统，讨论了航天器故障天地一体化集成诊断和预测方法，对航天器故障天地一体化集成诊断系统和方法的特点进行了分析。将天地2个系统集成在一起对航天器故障进行诊断和预测，其效率、准确性和可靠性较高。     

多处损伤的疲劳裂纹扩展分析方法研究

多处损伤（ＭＳＤ）影响老龄飞机结构完整性的重要因素之一。本文以线弹性断裂力学为基础，建立了一套工程适用且具有良好预测精度的ＭＳＤ疲劳裂纹扩展分析方法。