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991.
微型脉冲推力器点火启动过程计算与点火药量选择 总被引:10,自引:2,他引:8
建立了微型脉冲推力器点火启动模型,模型中考虑了两相流动和颗粒对推进剂表面的冲击传热。根据数值计算结果,给出了不同产物颗粒含量下的点火药量选择参考范围。该参考范围对于产物颗粒含量小于50%的点火药是适用的;由于过多的颗粒含量将对装药表面产生强烈的热力冲蚀破坏作用,产物颗粒含量超过50%的点火药不适合微型火箭发动机。 相似文献
992.
993.
Comparison between statistical properties of Forbush decreases caused by solar wind disturbances from coronal mass ejections and coronal holes 总被引:1,自引:1,他引:0
994.
面向月球采样返回任务分析需求,对月面上升段的轨迹优化及燃料消耗影响因素进行了研究。基于上升器运动模型,建立以燃料消耗最优为目标考虑入轨约束的轨迹优化模型,通过Gauss伪谱法和序列二次规划求解上升过程最优推力方向。改变运动模型中的初始推重比、入轨约束中的目标轨道参数,根据轨迹优化结果得到对应的燃料消耗,分析了这些因素对上升器燃料消耗的影响。针对上升器非共面起飞的问题,提出了上升偏航、升交点调整、倾角调整3种方案,从燃料消耗的角度分析了各方案的适用情况,为未来工程应用提供参考。 相似文献
995.
A new modeling scheme for powered parafoil unmanned aerial vehicle platforms: Theory and experiments
《中国航空学报》2019,32(11):2466-2479
A novel framework is established for accurate modeling of Powered Parafoil Unmanned Aerial Vehicle (PPUAV). The model is developed in the following three steps: obtaining a linear dynamic model, simplifying the model structure, and estimating the model mismatch due to model variance and external disturbance factors. First, a six degree-of-freedom linear model, or the structured model, is obtained through dynamic establishment and linearization. Second, the data correlation analysis is adopted to determine the criterion for proper model complexity and to simplify the structured model. Next, an active model is established, combining the simplified model with the model mismatch estimator. An adapted Kalman filter is utilized for the real-time estimation of states and model mismatch. We finally derive a linear system model while taking into account of model variance and external disturbance. Actual flight tests verify the effectiveness of our active model in different flight scenarios. 相似文献
996.
M. Prabhu K. Unnikrishnan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(7):1672-1688
In the present work, we analyzed the daytime vertical E × B drift velocities obtained from Jicamarca Unattended Long-term Ionosphere Atmosphere (JULIA) radar and ΔH component of geomagnetic field measured as the difference between the magnitudes of the horizontal (H) components between two magnetometers deployed at two different locations Jicamarca, and Piura in Peru for 22 geomagnetically disturbed events in which either SC has occurred or Dstmax < ?50 nT during the period 2006–2011. The ΔH component of geomagnetic field is measured as the differences in the magnitudes of horizontal H component between magnetometer placed directly on the magnetic equator and one displaced 6–9° away. It will provide a direct measure of the daytime electrojet current, due to the eastward electric field. This will in turn gives the magnitude of vertical E × B drift velocity in the F region. A positive correlation exists between peak values of daytime vertical E × B drift velocity and peak value of ΔH for the three consecutive days of the events. It was observed that 45% of the events have daytime vertical E × B drift velocity peak in the magnitude range 10–20 m/s and 20–30 m/s and 20% have peak ΔH in the magnitude range 50–60 nT and 80–90 nT. It was observed that the time of occurrence of the peak value of both the vertical E × B drift velocity and the ΔH have a maximum (40%) probability in the same time range 11:00–13:00 LT. We also investigated the correlation between E × B drift velocity and Dst index and the correlation between delta H and Dst index. A strong positive correlation is found between E × B drift and Dst index as well as between delta H and Dst Index. Three different techniques of data analysis – linear, polynomial (order 2), and polynomial (order 3) regression analysis were considered. The regression parameters in all the three cases were calculated using the Least Square Method (LSM), using the daytime vertical E × B drift velocity and ΔH. A formula was developed which indicates the relationship between daytime vertical E × B drift velocity and ΔH, for the disturbed periods. The E × B drift velocity was then evaluated using the formulae thus found for the three regression analysis and validated for the ‘disturbed periods’ of 3 selected events. The E × B drift velocities estimated by the three regression analysis have a fairly good agreement with JULIA radar observed values under different seasons and solar activity conditions. Root Mean Square (RMS) errors calculated for each case suggest that polynomial (order 3) regression analysis provides a better agreement with the observations from among the three. 相似文献
997.
利用碳纤维三向编织物(triaxial woven fabric,TWF)作为增强材料,与柔性基体材料硅橡胶复合,制成兼具一定柔性和刚性的复合材料壳膜结构,用于卫星天线反射器,是一种新型的高精度可展开天线实现方案。采用复合材料细观方法,对碳纤维增强硅橡胶TWF复合材料进行了力学性能的研究。首先由纤维和基体的材料特性得到均质纤维束的材料特性;接下来考虑纤维束交织情况(起伏波动)建立由纤维束组成的单胞实体有限元模型;然后对单胞实体有限元模型进行均匀化分析,施加周期性边界条件,最终得到等效的均质材料特性;为满足天线反射器高性能需求,分析了碳纤维种类、纤维体积分数对单胞等效性能的影响规律。对该材料力学性能的研究,可以为其未来应用于大型高精度可展开天线反射器提供一定的理论依据。 相似文献
998.
999.
S.A. Demin Y.A. Nefedyev A.O. Andreev N.Y. Demina S.F. Timashev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(2):639-644
The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously. 相似文献
1000.
Fuyu Sun Jianping Zhou Zheyao Xu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):189-206
This study proposes a new simulation platform named Simulation Integrated Management (SIM) for the analysis of parallel and distributed systems. The platform eases the process of designing and testing both applications and architectures. The main characteristics of SIM are flexibility, scalability, and expandability. To improve the efficiency of project development, new models of early-warning satellite system were designed based on the SIM platform. Finally, through a series of experiments, the correctness of SIM platform and the aforementioned early-warning satellite models was validated, and the systematical analyses for the orbital determination precision of the ballistic missile during its entire flight process were presented, as well as the deviation of the launch/landing point. Furthermore, the causes of deviation and prevention methods will be fully explained. The simulation platform and the models will lay the foundations for further validations of autonomy technology in space attack-defense architecture research. 相似文献