椭圆轨道拱线相位调节方法研究

分析了两个大小相同、拱线不同的椭圆轨道问的轨道转移,研究了单脉冲转移和双脉冲对称转移方法。用遗传算法解决了对称转移方法中最优变轨点的位置确定,获得了对称转移问题的数值解。仿真结果表明：对称转移较单脉冲转移更省能量。     

基于微型固体推力器阵列的轨道控制点火算法

为了解决基于微型固体推力器阵列轨道控制的推力器组合点火问题,优化了阵列布局,使其适用于轨道控制,得出了推力器坐标位置分布律。在此基础上研究了推力器阵列组合点火算法,建立了相应数学模型,进行了算法验证。仿真结果表明,设计的推力器阵列优化方案能够满足皮纳卫星轨道控制要求,所建数学模型能有效解决点火问题,设计的算法能够实现较快寻址。     

基于小波分析的信号滤波方法研究

设计了模拟温度信号的数据采集系统,采集了温度信号T．分别利用最小二乘平滑滤波方法和小波变换滤波方法对传感器输出的原始温度信号T进行滤波,通过对比滤波后波形和残差体现了小波分析在信号滤波应用中的优越性。     

基于圆形轨道的卫星位置递推方法

卫星无源定位系统对目标进行定位时,用于定位的卫星位置与时差或相位差等信息可能不同步,无法进行定位,需要把定位信息统一到同一时刻。针对这一问题,提出了基于圆形轨道的卫星位置递推方法,把卫星位置信息同其它信息统一到同一时刻,然后进行定位。该方法比常用的直线轨道递推方法误差更小,准确度更高,对提高定位精度具有较大应用价值。     

卫星轨道误差的相关性

卫星的轨道误差是卫星测控中需加以约定的重要指标之一,其常用的表示方法主要有Kepler轨道根数形式和RTN投影形式。本文推导了RTN形式的卫星位置、速度误差与Kepler根数误差间的关系,给出了近圆轨道中RTN形式位置、速度误差间的定量关系,分析了RTN形式位置误差约束下Kepler根数误差的相关性,并分别给出了验证算例。该结果可用于分析确定卫星轨道误差指标,使其彼此匹配。     

Spinning solar sail orbit steering via spin rate control

The orbit of a solar sail can be controlled by changing the attitude of the spacecraft. In this study, we consider the spinning solar power sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which is managed by Japan Aerospace Exploration Agency (JAXA). The IKAROS attitude, i.e., the direction of its spin-axis, is nominally controlled by the rhumb-line control method. By utilizing the solar radiation torque, however, we are able to change the direction of the spin-axis by only controlling its spin rate. With this spin rate control, we can also control indirectly the solar sail’s trajectory. The main objective of this study is to construct the orbit control strategy of the solar sail via the spin-rate control method. We evaluate this strategy in terms of its propellant consumption compared to the rhumb-line control method. Finally, we present the actual flight attitude data of IKAROS and the change of its trajectory.     

Orbit determination performances using single- and double-differenced methods: SAC-C and KOMPSAT-2

In this paper, Global Positioning System-based (GPS) Orbit Determination (OD) for the KOrea-Multi-Purpose-SATellite (KOMPSAT)-2 using single- and double-differenced methods is studied. The requirement of KOMPSAT-2 orbit accuracy is to allow 1 m positioning error to generate 1-m panchromatic images. KOMPSAT-2 OD is computed using real on-board GPS data. However, the local time of the KOMPSAT-2 GPS receiver is not synchronized with the zero fractional seconds of the GPS time internally, and it continuously drifts according to the pseudorange epochs. In order to resolve this problem, an OD based on single-differenced GPS data from the KOMPSAT-2 uses the tagged time of the GPS receiver, and the accuracy of the OD result is assessed using the overlapping orbit solution between two adjacent days. The clock error of the GPS satellites in the KOMPSAT-2 single-differenced method is corrected using International GNSS Service (IGS) clock information at 5-min intervals. KOMPSAT-2 OD using both double- and single-differenced methods satisfies the requirement of 1-m accuracy in overlapping three dimensional orbit solutions. The results of the SAC-C OD compared with JPL’s POE (Precise Orbit Ephemeris) are also illustrated to demonstrate the implementation of the single- and double-differenced methods using a satellite that has independent orbit information available for validation.     

Microstructure and mechanical properties of hybrid fabricated 1Cr12Ni2WMoVNb steel by laser melting deposition

 Laser melting deposition was carried out to deposit a 1Cr12Ni2WMoVNb steel bar on a wrought bar of same material. Room-temperature tensile properties of the hybrid fabricated 1Cr12Ni2WMoVNb steel sample were evaluated, and microstructure, fracture surface morphology, and hardness profile were analyzed by an optical microscope (OM), a scanning electron microscope (SEM), and a hardness tester. Results show that the hybrid fabricated 1Cr12Ni2WMoVNb steel sample consists of laser deposited zone, wrought substrate zone, and heat affected zone (HAZ) of the wrought substrate. The laser deposited zone has coarse columnar prior austenite grains and fine well-aligned dendritic structure, while the HAZ of the wrought substrate has equiaxed prior austenite grains which are notably finer than those in the wrought substrate zone. Besides, austenitic transformation mechanism of the HAZ of the wrought substrate is different from that of the laser deposited zone during the reheating period of the laser deposition, which determines the different prior austenite grain morphologies of the two zones. Microhardness values of both the laser deposited zone and the HAZ of the wrought substrate are higher than that of the wrought substrate zone. Tensile properties of the hybrid fabricated 1Cr12Ni2WMoVNb steel sample are comparable to those of the wrought bar, and fracture occurs in the wrought substrate zone during the tensile test.     

向变革要效益——韩国空军训练变革情况介绍

介绍了韩国空军原训练体制和变革需求,分析了韩国空军变革后的新训练体制,详细阐述了引入T-50战斗教练机之后训练情况,最后对其训练效益进行了总结.     

Synthesis of TiNi/Ti_2Ni Composite Particles in Molten Salts

A new process of synthesizing TiNi/Ti2Ni composite particles, high temperature molten salts method, is introduced. This method uses molten salts as a reaction medium that does not take part in the chemical reaction and can be easily dissolved in rinsing water. Ac-cording this method, the composite particles were prepared in molten salts at 700 ℃-900 ℃. By means of differential scanning calo-rimetry (DSC), the reversible martensitic transformation of TiNi particles in these composite particles was confirmed.