某型膨胀循环发动机高空模拟试验方案研究

某型膨胀循环发动机在研制初期基于环境压力可能对膨胀循环发动机起动加速性有较大影响的考虑,采用了全程主动引射高空模拟试验方案,试验结果显示环境压力对发动机起动加速性的影响较小。发动机室压和喷管面积比是影响引射方式的主要参数,该型膨胀循环发动机与采用被动引射的某型燃气发生器循环发动机参数相当,这为该型膨胀循环发动机采用被动引射提供了可能,并对膨胀循环发动机采用被动引射高空模拟试验方案的可行性进行仿真研究。     

A numerical optimization of high altitude testing facility for wind tunnel experiments

High altitude test facilities are required to test the high area ratio nozzles operating at the upper stages of rocket in the nozzle full flow conditions.It is typically achieved by creating the ambient pressure equal or less than the nozzle exit pressure.On average,air/GN2is used as active gas for ejector system that is stored in the high pressure cylinders.The wind tunnel facilities are used for conducting aerodynamic simulation experiments at/under various flow velocities and operating conditions.However,constructing both of these facilities require more laboratory space and expensive instruments.Because of this demerit,a novel scheme is implemented for conducting wind tunnel experiments by using the existing infrastructure available in the high altitude testing(HAT)facility.This article presents the details about the methods implemented for suitably modifying the sub-scale HAT facility to conduct wind tunnel experiments.Hence,the design of nozzle for required area ratio A/A*,realization of test section and the optimized configuration are focused in the present analysis.Specific insights into various rocket models including high thrust cryogenic engines and their holding mechanisms to conduct wind tunnel experiments in the HAT facility are analyzed.A detailed CFD analysis is done to propose this conversion without affecting the existing functional requirements of the HAT facility.     

Feasibility assessment of optical technologies for reliable high capacity feeder links

Space telecom scenarios like data relay satellite and broadband/broadcast service providers require reliable feeder links with high bandwidth/data rate for the communication between ground station and satellite. Free space optical communication (FSOC) is an attractive alternative to microwave links, improving performance by offering abundant bandwidth at small apertures of the optical terminals. At the same time Near-Earth communication by FSOC avoids interference with other services and is free of regulatory issues. The drawback however is the impairment by the laser propagation through the atmosphere at optical wavelengths. Also to be considered are questions of eye safety for ground personnel and aviation. In this paper we assess the user requirements for typical space telecom scenarios and compare these requirements with solutions using optical data links through the atmosphere. We suggest a site diversity scheme with a number of ground stations and a switching scheme using two optical terminals on-board the satellite. Considering the technology trade-offs between four different optical wavelengths we recommend the future use of 1.5 µm laser technology and calculate a link budget for an atmospheric condition of light haze on the optical path. By comparing link budgets we show an outlook to the future potential use of 10 µm laser technology.     

飞机突防航迹的非线性解耦跟踪

针对12维非线性飞机动力学模型,利用非线性逆系统理论和现代最优控制理论设计了一组非线性飞行控制规律。这组控制规律通过解耦控制飞机的飞行速度(V)、滚转角(φ)、航迹角(γ)和偏航角(φ_w),使飞机能够精确地跟踪期望的三维突防航迹。计算结果表明,由于这组控制规律计及了飞机动力学模型中的非线性因素,能够完全消除飞机的剧烈耦合反应,从而有效地改善了飞机的动态特性,提高了其低空机动飞行的安全性,大大减轻了驾驶员的工作负担和精神压力,从而圆满地完成突防袭击任务。     

主动引射高模试车台水喷雾冷却器等效热力系统模型的研究

水喷雾冷却器在主动引射高空模拟试车台中具有重要作用,其出口处温度的有效控制是保障试车正常运行的关键。针对某型号火箭发动机常压试验的喷雾冷却器,建立了等效热力系统模型,并在Simulink平台上建立了相应的动态仿真模型,计算结果与试车测试结果对比证明所建等效热力系统模型正确,从而为实现其出口处温度的有效控制提供依据。     

Preparing for space: Increasing technical readiness of low-cost high-performance remote sensing using high-altitude ballooning

Two widely available, small size, weight and power camera systems were flown above 97 % of Earth’s atmosphere and showed utility in single filter vegetation and soil analysis in a space analogue environment. The experiment was conducted as a low-cost verification and test analogue to flying on vastly more expensive low Earth orbit missions. Normalised Difference Vegetation Index (NDVI) was used as the metric by which performance was analysed for ground calibration testing, low and near-space altitude remote sensing. Ground calibration testing with a laboratory-grade spectrometer revealed that both cameras were able to return consistent NDVI results, and high-altitude balloon flight allowed similar data capture from an environment similar to space. Although compressed captured imagery had been processed using gamma correction and pre-image processing, these were able to be corrected provided that access to radiometrically-calibrated data was available. The two hobbyist cameras were shown to return scientifically useful results, demonstrating performance, and additionally their utility for citizen science applications in the near-space environment.     

临近空间飞艇艇库外约束及稳定性分析

临近空间飞艇在发放前通常停放在艇库内,一旦离开艇库就不可避免地受到艇库外天气,尤其地面风的影响,不仅影响飞艇发放操作的快捷和安全,而且还事关飞行试验的成败。文章建立了大型飞艇在地面受两侧约束时的力学模型,采用动力学方法,分析了受到地面风作用时飞艇的姿态和约束拉力的变化,得到地面风起时和风速稳定后的解析解,评估了飞艇受到地面风作用时的稳定性和安全性。通过分析得到在两侧约束条件下飞艇对正向风和侧风的承受极限,为临近空间飞艇采用两侧约束方式的可行性提供了判据,也为今后发展临近空间飞艇发放技术提供借鉴。     

试论多元化职业指导与城市就业体协同发展研究

大学生就业事关国家的经济发展、社会稳定以及社会对教育和人力资源投资的信心。笔者在近几年高校学生就业工作中发现,职业指导存在理论研究基础薄弱、内容和形式单一、职业指导队伍不稳定、与城市就业体系脱节等问题,以至高校学生就业存在选择性盲区,因此,加强职业指导多元化发展显得尤为重要。本文以研究河北省廊坊市内各大高校毕业生就业去向情况为实例,重点研究职业指导多元化的主要内容和方法。通过对廊坊高校的2013届毕业生跟踪调查与公共服务机构提供就业服务的意见等几方面进行了调查及量化分析,提出解决对策,推进廊坊及河北省高校毕业生就业能力,增强高校毕业生服务区域经济社会发展和服务行业的能力,对进一步推进河北省的高校毕业生工作健康稳定发展,具有重大的现实意义。     

高空平台通信系统中基于预测的小区切换算法

在平流层的环境中,高空平台(HAPS)的扰动特性严重影响了通信系统的小区切换性能。在平台扰动和终端移动的场景中,基于固定门限的切换算法容易增加不必要的切换次数,切换性能较差。建立HAPS覆盖模型,用户终端根据其速度动态选择切换检测周期,提出基于接收信号强度差分最小均方预测的自适应切换算法,推导了无线链路失败率的上限。仿真结果表明,相比传统固定门限的切换算法,本文算法有效降低了不必要的切换,同时还可将无线链路失败率控制在1%以下,能够适应多种通信场景。