Sandwich module prototype progress for space solar power

Space solar power (SSP) has been broadly defined as the collection of solar energy in space and its wireless transmission for use on earth. This approach potentially gives the benefit of provision of baseload power while avoiding the losses due to the day/night cycle and tropospheric effects that are associated with terrestrial solar power. Proponents have contended that the implementation of such systems could offer energy security, environmental, and technological advantages to those who would undertake their development. Among recent implementations commonly proposed for SSP, the modular symmetrical concentrator (MSC) and other modular concepts have received considerable attention. Each employs an array of modules for performing conversion of concentrated sunlight into microwaves or laser beams for transmission to earth. While prototypes of such modules have been designed and developed previously by several groups, none have been subjected to the challenging conditions inherent to the space environment and the possible solar concentration levels in which an array of modules might be required to operate. The research described herein details our team's efforts in the development of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for microwave-based “sandwich” module prototypes. The implementation status and testing results of the prototypes are reviewed.     

大功率空间核电推进技术研究进展

大功率空间核电推进系统是空间核电源技术和大功率电推进技术的高度融合,具有高能量密度、超高比冲、较大推力的优势,可适用于超大型航天器轨道转移任务、远距离无人深空探测任务、载人火星等大型深空探测任务,能够极大地拓展人类深空探测的能力。本文针对大功率空间核电推进技术,对其工作原理和系统组成进行了介绍,同时开展了关键技术梳理,重点归纳了国内外在技术领域的研究历程和最新进展。     

一种基于NOMA的Q学习卫星通信随机接入方法

基于非正交多址接入(NOMA)的Q学习(Q-Learning)随机接入方法(NORA-QL)是实现物联网中海量设备泛在接入的一项有效技术.为了解决NORA-QL方法仍存在的传输能效和过载容量较低的问题,提出了一种适合卫星通信网络的改进方法(I-NORA-QL).针对传输功耗高的问题,I-NORA-QL利用卫星广播的全局...     

运载火箭故障模式及制导自适应技术应用分析

为提高制导控制系统在运载火箭全发射任务周期中的智慧水平，提高运载火箭完成任务的鲁棒能力，从不同角度阐述了运载火箭故障模式，创新提出了基于能量属性的故障分类方法。针对不同级别的能量故障提出了对制导控制系统的功能、性能需求。尤其针对小、中级别能量故障，简述了运载火箭故障飞行制导自适应方法应用，包含案例及任务目标变更原则等，并分析了制导自适应技术后续工程化应用的实施途径。基于能量属性的故障分类方法及制导自适应方法可应用于后续中国运载火箭工程研制。     

基于通用航空的空中交通管制压力和风险评估方法的探讨

飞行流量管理现已成为业内人士经常研究和谈论的话题,也是民航发展过程中必须解决的重要问题。与运输航空不同,通用航空的流量管理和评估问题却少有人问津。本文结合国内最大的通用航空基地——民航飞行学院的实际运行情况,把空中交通管制工作风险按照能量的概念数据化,借鉴能量控制的理论,提出风险势能的概念,并对这一概念在通用航空空中交通流量管理中的应用进行了探讨。     

含不同氧化剂的复合推进剂能量及特征信号研究

为研究含能氧化剂环三亚甲基三硝胺(RDX)、六硝基六氮杂异戊兹烷(CL-20)、二硝酰胺铵(ADN)、硝仿肼(HNF)逐步取代高氯酸铵(AP)后复合推进剂的能量特性和特征信号性能,采用最小自由能原理对配方进行了化学平衡性能计算.结果表明:四种高能氧化剂逐步取代AP都达到了增加标准理论比冲和降低二次烟的目的,标准理论比冲增加率的峰值分别为0.85％,1.1％,3.37％及5.1％,ADN对降低特征信号二次燃烧火焰效果最好.ADN和HNF逐步取代A1后,标准理论比冲、一次烟及二次燃烧火焰都呈下降趋势,二次烟呈上涨趋势.     

Drag and energy accommodation coefficients during sunspot maximum

Conditions appropriate to gas-surface interactions on satellite surfaces in orbit have not been successfully duplicated in the laboratory. However, measurements by pressure gauges and mass spectrometers in orbit have revealed enough of the basic physical chemistry that realistic theoretical models of the gas-surface interaction can now be used to calculate physical drag coefficients. The dependence of these drag coefficients on conditions in space can be inferred by comparing the physical drag coefficient of a satellite with a drag coefficient fitted to its observed orbital decay. This study takes advantage of recent data on spheres and attitude stabilized satellites to compare physical drag coefficients with the histories of the orbital decay of several satellites during the recent sunspot maximum. The orbital decay was obtained by fitting, in a least squares sense, the semi-major axis decay inferred from the historical two-line elements acquired by the US Space Surveillance Network. All the principal orbital perturbations were included, namely geopotential harmonics up to the 16th degree and order, third body attraction of the Moon and the Sun, direct solar radiation pressure (with eclipses), and aerodynamic drag, using the Jacchia-Bowman 2006 (JB2006) model to describe the atmospheric density. After adjusting for density model bias, a comparison of the fitted drag coefficient with the physical drag coefficient has yielded values for the energy accommodation coefficient as well as for the physical drag coefficient as a function of altitude during solar maximum conditions. The results are consistent with the altitude and solar cycle variation of atomic oxygen, which is known to be adsorbed on satellite surfaces, affecting both the energy accommodation and angular distribution of the reemitted molecules.     

Mechanical behaviour of adhesively single lap joint under buckling conditions

Adhesive Single Lap Joints have been subjected to tensile and bending investigations by many researchers. However, the joint is also likely to experience buckling loading in some aerospace applications. The aim of this work is to investigate the joint behaviour under quasi-static buckling conditions. For this purpose, the joints with three different adherend thicknesses and 25 mm overlap length were tested using two different types of adherends and an adhesive film. They were modelled using a non-linear Finite Element Method via the ABAQUS Explicit package programme. Load to failure and stress distributions in the joints were predicted and compared with the experimental results, which were found in a good agreement. The adhesive layer in the joint was assumed to experience shear stresses under the buckling mode, similar to that in tensile loading, yet, the stress concentrations at the ends of the overlap, the main cause of the failure, resulted in different effects on the joint performance; for the buckling mode the critical stresses were in compression but for the tensile case in peeling. Unlike the latter, the former was found to prevent failure of the layer depending on the adherend thickness, causing different failure mechanisms. There were two different failure modes of the joints; a complete failure in the adhesive layer and large plastic deformation of adherends which could be a good source for crashworthiness situations. Mechanical properties of the adherends were found to play important roles on the joint performance.     

Aeroelastic prediction and analysis for a transonic fan rotor with the “hot” blade shape

This paper focuses on aeroelastic prediction and analysis for a transonic fan rotor with only its “hot” (running) blade shape available, which is often the case in practical engineering such as in the design stage. Based on an in-house and well-validated CFD solver and a hybrid structural finite element modeling/modal approach, three main aspects are considered with special emphasis on dealing with the “hot” blade shape. First, static aeroelastic analysis is presented for shape transformation between “cold” (manufacturing) and “hot” blades, and influence of the dynamic variation of “hot” shape on evaluated aerodynamic performance is investigated. Second, implementation of the energy method for flutter prediction is given and both a regularly used fixed “hot” shape and a variable “hot” shape are considered. Through comparison, influence of the dynamic variation of “hot” shape on evaluated aeroelastic stability is also investigated. Third, another common way to predict flutter, time-domain method, is used for the same concerned case, from which the predicted flutter characteristics are compared with those from the energy method. A well-publicized axial-flow transonic fan rotor, Rotor 67, is selected as a typical example, and the corresponding numerical results and discussions are presented in detail.