Orbit design for future SpaceChip swarm missions in a planetary atmosphere

The effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag.     

传感器安装对平板气动热测量精度的影响

对高超声速飞行器来说，气动热的准确预测是其合理选择防热材料及热结构设计的重要依据，但目前在激波风洞试验中气动热的高精度测量仍较为困难，热流的测量精度受到诸多非理想因素的影响，但传感器安装对热流测量精度的影响却鲜见研究。选取平板模型来研究传感器非理想安装对气动热测量精度的影响，针对不同的传感器安装偏差(凸出或凹入模型表面0.1~0.5 mm)，分析不同雷诺数下传感器安装对气动热测量精度的影响规律及机理。研究结果表明:传感器安装对气动热测量精度有较大影响，凸出安装会导致热流测量结果偏大，而凹入安装则会导致测量结果偏小，热流偏差会随着安装偏差的增大而增大，且高来流雷诺数下传感器非理想安装所引起的热流误差更大；以边界层当地厚度对凹凸程度无量纲化，非理想安装带来的测量偏差只与该无量纲参数相关。研究结果能够为气动热测量的实验方案设计及测量误差分析提供一定的理论指导。      

Effects of TADs on the F region of the mid-latitude ionosphere during an intense geomagnetic storm

Based on observations of two ionosondes at Wuhan and Kokubunji, this paper presents effects of TADs on the daytime mid-latitude ionosphere during the intense geomagnetic storm on March 31, 2001. During a positive ionospheric storm, the start of the enhancement of the foF2 (F2 peak plasma frequency) at Wuhan lags that at Kokubunji by 15 min, which corresponds to the time interval of traveling atmospheric disturbances (TADs’) propagation from Kokubunji to Wuhan. Associated with the uplifting of the hmF2 (height of F2 peak) caused by TADs, it is observed by the two ionosondes that the F1 cusp becomes better developed. Therefore, during a geomagnetic storm, TADs originating from the auroral oval may have a strong influence on the shape of the electron density profile in the F1 region ionosphere at middle latitudes. It is highly likely that TADs are responsible for the evolution of the F1 cusp.     

Phase-Coded Interrupted CW Signals and Processors

High resolution radars require signals with large time-bandwidth product such as CW signal and coherent pulse train (CPT). We discuss a phase-coded interrupted CW (ICW) signal which is the combination of CW signal and CPT. Phase codes used here are with perfect periodic autocorrelation. The periodic ambiguity function of ICW signals is studied including single-carrier signal and multi-carrier signal. It is interesting that the gate function has different effects on two signals and contributes to a multi-carrier ICW signal which yields nearly perfect autocorrelation. Meanwhile we also suggest an efficient receiver approach to ICW signals, which can reduce the computational burden of the processor and utilize the good properties of P3 and P4 codes.     

原子钟调相白噪声降噪方法

原子钟的五种噪声反映了它在一定时间间隔内的性能。当取样间隔小于1h，原子钟主要表现为调相白噪声。在地方协调时UTC（NTSC）的实时监控中，不仅要求参考原子时（RTA，用于地方协调时控制的参考）具有很高的长期稳定度，而且要求其短期稳定度亦很高。影响RTA短期稳定度的主要是个台原子钟的调相白噪声。首先讨论了确定原子钟短期噪声的方法，进而利用小波分析方法研究了原子钟凋相白噪声分离与降噪的方法。     

Vision-based bio-inspired guidance law for small aerial vehicle

During predation, a flying insect can form a stealth flight path. This behavior is called motion camouflage. Based on the study results of this behavior, the perception and neurology of flying insects, a novel bio-inspired guidance law is proposed for the terminal guidance for small aerial vehicle with charge-coupled device imaging seekers. The kinematics relationship between a small aerial vehicle and target is analyzed, and a two-dimensional guidance law model is established by using artificial neural networks. To compare with the proportional guidance law, the numerical simulations are carried out in the vertical plane and in the horizontal plane respectively. The simulation results show that the ballistic of the small aerial vehicle is straighter and the normal acceleration is smaller by using the bio-inspired guidance law than by using the proportional guidance law. That is to say, the bio-inspired guidance law just uses the information of the target from the imaging seeker,but the performance of it can be better than that of the proportional guidance law.     

预混段结构对旋流预混氢火焰回火形式影响的数值研究

为了区分不同类型的回火形式,以便可以对不同类型的回火施加不同的控制方法,引入试验设计(DOE)方法和方差分析方法数值分析了预混段长度L和预混段出口处水力直径D对回火形式和回火极限的影响。主要得到如下结论:L和D对回火极限均有显著影响,通过减少混合物在预混段内的停留时间可以同时改善燃烧诱导涡破碎(CIVB)回火和边界层回火;L/D存在两个临界值,当L/D≤(L/D)cri1时发生边界层回火,当L/D(L/D)cri2时发生CIVB回火,当(L/D)cri1L/D≤(L/D)cri2时可能只发生CIVB回火或两种回火形式共存;L/D通过改变CIVB回火发生所需的临界切向涡量值而作用于CIVB回火,L/D值越大,诱发CIVB回火所需的临界切向涡量值越小,越容易发生CIVB回火。     

太赫兹固态电子器件和电路

随着微电子技术的飞速发展,半导体器件的截止频率已经进入到太赫兹频段,太赫兹电路的频率特性特性得到极大发展。以固态器件为基础的电路的工作频率进入到太赫兹频段。太赫兹固态电子器件与电路技术在空间领域有着重要的应用前景。文章重点介绍InP基三端太赫兹固态电子器件和电路,以及太赫兹肖特基二极管器件和电路的技术发展过程与最新动态。并指出随着器件与电路的整体化与集成化发展趋势,太赫兹单片集成技术是其未来发展方向。     

碳纤维基底真空沉积涂层耐温度循环性能加速试验方法研究

为了考核某低地球轨道卫星微波探测类载荷碳纤维基底天线反射器的真空沉积涂层在轨承受高低温循环的能力,以确保该涂层在轨经历频繁高低温循环后的性能仍满足产品在轨工作要求,提出基于航天产品环境应力筛选建立温度循环加速因子模型的试验方法,并开展不同规格试件的温度循环加速试验。按等效在轨8年寿命,在试验前、试验中和等效寿命延长约1/3后共进行14次试件涂层外观检查和热控性能箱外测试,结果表明涂层外观完好,太阳吸收比和发射吸收比均符合指标要求,耐温度循环性能优异,满足在轨使用要求。     

主动冷却燃烧室燃烧与传热耦合过程迭代分析设计方法

为了对主动冷却超燃冲压发动机进行研究与设计,采用实验与计算相结合的方法,对主动冷却超燃冲压发动机燃烧室内传热与燃烧的耦合过程进行了分析。该方法采用燃烧室静压分布的测量值作为输入条件,开展燃气-结构-燃料耦合传热分析,获得经过冷却系统后燃料的状态参数;将燃料的状态参数作为实验参数,开展直联式超声速燃烧实验,得到新的静压分布,如此反复迭代,直至燃料状态不再变化,最终确定主动冷却燃烧室的各种传热与燃烧特性参数。利用该分析方法,初步开展了不同飞行马赫数条件下主动冷却燃烧室闭环运行状态研究,得到了冷却煤油温度与燃烧室壁温同飞行马赫数的关系。