氮氧化物羽烟在电离层局部的光热效应

在航天器羽烟一次性抛出和呈球状近似情况下,模拟了电离层E层NO羽烟与周围大气压力平衡时的最大亮度及其随时间的变化．在110km抛出的5molNO羽烟可使它获得瞬时夜间中等偏强极光那样的亮度,在140km抛出的同样数量的NO羽烟亮度却急剧地减弱．还模拟了白天夜间温度为1000K的NO2羽烟在190km和250km两个高度、50mol和500mol两种抛出总量所造成的局部大气温度短时间内的下降．在F层下部,夜间较大抛出量所造成的冷却效应是显著的．     

GOES—9将使美国天气预报能力进一步加强

１９９５年５月２３日，美国在卡纳维拉尔角发射了一颗新的静止气象卫星，这是美国为进一步加强其天气预报能力的又一新举措。这颗静止气象卫星是ＮＯＡＡ新一代地球静止环境业务气象卫星（ＧＯＥＳ－ＮＥＸＴ）系列中的第二颗，卫星入轨前叫ＧＯＥＳ－Ｊ，入轨后则按习惯改称ＧＯＥＳ－９。随着它的发射，美国将拥有一个具有先进技术的双星观测系统，从而大大增强了美国气象部门在追踪和预报美国本土及附近区域灾害性天气系统的能力。ＧＯＥＳ－ＮＥＸＴ系列由５颗共耗资１０亿美元的卫星组成，其中ＧＯＥＳ－９的造价为２．２亿美元。该系…     

磁暴期间中纬度电离层剖面结构变化的数值模拟

利用电离层理论模型模拟了磁暴期间热层大气温度、成分、中性风和电场扰动对电离层电子密度剖面结构，特别是峰值密度和峰值高度变化的影响，结果表明，热层大气温度变化所引起光化反应系数的改变对电离层剖面结构影响不大；热层大气成分特别是Ｎ２／Ｏ的变化能有效地引起密度剖面变化，Ｎ２增加足以使峰值密度产生所观测到的负相暴；由中性风和电场引起等离子体漂移是峰值高度ｈｍＦ２变化的主要原因，但对电子密度的影响不足以抵消     

H—2火箭的OREX有效载荷

日本Ｈ－２火箭在１９９４年２月４日的首次发射中携带了２个试验性有效载荷：火箭性能评估载荷（ＶＥＰ）和轨道再入试验载荷（ＯＲＥＸ）。ＶＥＰ用于测定Ｈ－２火箭的性能参数，为日本发射第６颗技术试验卫星（ＥＴＳ－６）作准备；ＯＲＥＸ是为日本计划在１９９９年发射的小型不载人航天飞机ＨＯＰＥ，收集再入数据和试验热防护系统。外形酷似飞碟的ＯＲＥＸ重１９００磅（约８６２千克），高１．４６米，外：径为３．４米，由ＮＡＳＤＡ和日本科学技术局国家宇航实验室共同研制。日本计划在ＯＲＥＸ的飞行过程中收集４方面的数据，即收…     

从ACCV‘95看计算机视觉技术的发展

介绍了第二届亚洲计算机视觉会议（ＳＥＣＯＮＤ ＡＳＩＡＮ ＣＯＮＦＥＲ－ＥＮＣＥ ＯＮ ＣＯＭＰＵＴＥＲ ＶＩＳＩＯＮ，ＡＣＣＶ’９５）的一些情况；回顾了在该领域及相关学科的研究成果，讨论了当前计算机视觉所面临的理论与实际应用问题，并对中国空间技术研究院这一学科的发展提出看法。     

日本霍普—X的飞行控制系统

“霍普”（ＨＯＰＥ）是日本Ｈ－２轨道飞机（Ｈ－２ＯｒｂｉｔｉｎｇＰｌａｎｅ）的缩写,为日本国家航天实验室（ＮＡＬ）和日本宇宙开发事业团（ＮＡＳＤＡ）联合研制的一个无人有翼空间运输系统。为了验证ＨＯＰＥ所用的各种技术,专门研制了几个试验飞行器,它们是Ｏ...     

电离层峰下结构的数值模拟

在考虑由扩散与中性风引起的动力学输运与有原子离子Ｏ＾＋（＾４Ｓ），Ｏ＾＋（＾２Ｄ）与Ｏ＾＋（＾２Ｐ）以及分子离子Ｏ２＾＋，ＮＯ＾＋，Ｎ２＾＋参加光化学反应的电离层－热层体系中，提出一个一维时变的电离层剖面数值模型，通过数值计算着重讨论了武昌地区Ｆ２层峰以下，尤其是Ｅ／Ｆ与Ｆ１／Ｆ２谷区的电离层形态与有关过程，得到如下结论：（１）对于原子离子，单一成分Ｏ＾＋（＾４Ｓ）的光化学反应与输运，也有助于形成     

从ACCV＇95看计算机视觉技术的发展

介绍了第二届亚洲计算机视觉会议（ＳＥＣＯＮＤＡＳＩＡＮＣＯＮＦＥＲＥＮＣＥＯＮＣＯＭＰＵＴＥＲＶＩＳＩＯＮ,ＡＣＣＶ’９５）的一些情况;回顾了在该领域及相关学科的研究成果;讨论了当前计算机视觉所面临的理论与实际应用问题,并对中国空间技术研究院这一学科的发展提出看法。     

日研制成功小型自动着陆实验机

１９９５年８月１１日，在富士重工业宇都宫制作所，日本航空宇宙技术研究所（ＮＡＬ）和日本宇宙开发事业团（ＮＡＳＤＡ）宣布，他们已研制成功小型自动着陆实验机（ＡＬＦＬＥＸ）。ＡＬＦＬＥＸ是为２０００年初日本实现天地往返运输系统（ＨＯＰＥ）计划达到实用化程度，并弄清其中个别关键技术而研制的三种实验样机中的一种。富士重工业耗资１２亿日元制成了两架这样的样机。其余两种实验样机其一是由三菱重工业制造的轨道再入实验机（ＯＲＥＸ），已于１９９４年２月由第一枚Ｈ－火箭发射成功，再一种是由川崎重工业正在制造中的高超…     

NOAA拟购买4颗新的地球静止环境业务卫星

美国国家海洋大气局（ＮＯＡＡ）在１９９４年４月成功发射了地球静止环境业务卫星一８（ＧＯＥＳ－８）之后，该星于今年１月１０日定点在西经７５的静止轨道上。ＧＯＥＳ－７则从西经１１２移到西经１３０的位置上，在太平洋上空监视美国西部的天气变化。为了在２００４～２０１０年发射新的ＧＯＥＳ卫星，ＮＯＡＡ在１９９６年预算中提出拟购买４颗新的ＧＯＥＳ卫星，其类似已研制出的５颗ＩＨＧＯＥＳ卫星。在今后两年内将初步研究下一代气象卫星，并在１９９８年提出未来１０年气象卫星发展计划，以迎接２１世纪的到来。预计４颗新的Ｇ…     

三维多组分羽流及其效应的数值模拟

考虑到实际卫星总体布局特点及姿控发动机燃气喷流为多组分的特点,采用差分求解N-S(Navier-Stokes)方程耦合DSMC(Direct Simulation Monte Carlo)方法建立三维多组分羽流场的数值模拟模型,对5 N无水肼单组元姿控发动机喷管产生的燃气羽流场及其效应进行数值模拟,计算得出羽流场的物理参数分布、化学组分分布,得到了羽流对太阳能帆板的羽流气动力和气动热效应.计算结果表明对于太阳能帆板的羽流效应防护应以N2,NH3为主,姿控发动机羽流会对太阳能帆板撞击产生气动力和气动热的影响,在太阳能帆板前沿中点处,存在气动压强峰值和气动热流峰值.计算结果为研究羽流效应提供了参考依据.     

卫星姿控发动机高空羽流场工程分析

发展卫星姿控小推力发动机高空羽流场的工程估算方法,计算分析其主要燃气组分的分布特征.采用网格技术将发动机喷管出口截面剖分形成多独立点源,建立了非均匀出口流动条件下的分析模型.与自由分子单一点源模型相比,该模型的计算结果更接近实验值.对MBB 10 N双组元发动机多组分羽流场的研究表明,压强场和内能场的变化较剧烈;不同于轻分子组分,重分子组分主要集中于轴线附近,其密度场呈较强方向性.      

进气旋流对推力喷管性影响的研究

介绍了模拟近代大涵道比发动机排气状况的旋流模型,和在喷管落压比1.2到6.5范围内,进气旋流对轴对称喷管,矩形收-扩喷管,楔形二元喷管,和单边膨胀斜板形喷管等性能和射流流态影响等的一些实验结果。实验数据指出:进气旋流可使喷管出口射流柱中的旋涡加强,射流与外界气流间的混合区扩大,中心核心流区缩小,但它对轴对称喷管出口流态的影响很小。进气旋流同时对喷管推力系数和流量系数均起不利影响,增大进气旋流角度会使喷管推力系数和流量都下降,特别是当旋流角超过某一“临界”值后二者降低很急剧,并且二元喷管降低的程度比轴对称喷管更严重,因之在具体应用情况中,保留多大发动机的旋流,要针对具体情况综合考虑各种因素来选定。     

氢氧发动机真空羽流干扰试验研究

为了研究航天器发动机多股羽流产生的羽流干扰对流场结构及参数的影响,在北京航空航天大学真空羽流效应试验系统（PES）中,采用总压皮托管阵列对60 N氢氧模拟发动机单机羽流和双机干扰羽流的压力场进行了测量。试验结果表明:单机羽流流场压力随着轴向距离的增大而迅速降低;受到钟形喷管产生的压缩波束影响,同一轴向距离上的压力最大值逐渐偏离喷管轴线;双机羽流干扰发生于两股发动机羽流主流之间的区域,干扰流的作用范围和强度随着轴向距离的增大而增大,干扰流压力最高可以达到单机羽流相同位置处压力的5倍以上;受到干扰流压缩波束边界的影响,同一轴向距离上的压力最大值逐渐偏离双发动机对称面。      

Collocated ionosonde and dense GPS/GLONASS network measurements of midlatitude MSTIDs

To analyze midlatitude medium-scale travelling ionospheric disturbances (MSTIDs) over Kazan (55.5°N, 49°E), Russia, the sufficiently dense network of GNSS receivers (more than 150 ground-based stations) were used. For the first time, daytime MSTIDs in the form of their main signature (band structure) on high-resolution two-dimensional maps of the total electron content perturbation (TEC maps) are compared with ionosonde data with a high temporal resolution. For a pair of events, a relationship between southwestward TEC perturbations and evolution of F2 layer traces was established. So F2 peak frequency varied in antiphase to TEC perturbations. The ionograms show that during the movement of plasma depletion band (overhead ionosonde) the F2 peak frequency is the highest, and vice versa, for the plasma enhancement band, the F2 peak frequency is the lowest. One possible explanation may be a greater inclination of the radio beam from the vertical during the placement of a plasma enhancement band above the ionosonde, as evidenced by the absence of multiple reflections and the increased occurrence rate of additional cusp trace. Another possible explanation may be the redistribution of the electron content in the topside ionosphere with a small decrease in the F peak concentration of the layer with a small increase in TEC along the line-of-sight. Analysis of F2 peak frequency variation shows that observed peak-to-peak values of TEC perturbation equal to 0.4 and 1 TECU correspond to the values of ΔN/N equal to 13% and 28%. The need for further research is evident.     

微射流强化混合对喷流红外辐射特性的影响

计算了微射流强化混合喷流在3~5μm波段的红外辐射特性,并与无微射流强化混合的喷流红外辐射特性进行了比较,分析了微射流强化混合对喷流红外辐射特性的影响.喷流的流场及温度场结果采用有限体积法求解N-S方程得到,采用Tam-Thies湍流模型模拟喷流.红外辐射特性的计算采用有限体积法求解吸收-发射性介质条件下的三维辐射传输方程得到.计算结果表明,在中等亚音速条件下,微射流可以达到较好的强化混合效果,射流流量占主流流量1%时,喷流的红外辐射强度比基准喷流的红外辐射强度降低15%左右,射流流量达到主流流量的3%时,喷流的红外辐射强度可以降低27%左右.     

Collisions in space: A retrospective overview of ISAS studies

A chronological review of studies in ISAS concerning collisions in space is presented. The collision probability in space with artificial orbiting bodies was estimated, and a Space Traffic Control System was proposed, in 1971. The design of a space station for safety against collision hazards was discussed in 1972. A trajectory optimization technique for low-thrust multiple rendezvous mission in order ti sweep space debris around the earth was developed in 1977. In 1984, the collision probability was reestimated using space bedris data accumulated for more than a decade. Several experimental projects in ISAS, such as hypervelocity impact experiments using a railgun system, sampling and measuring of alumina particles in exhaust plume of solid-propellant propellant rocket motors, and a result of analysis on the behavior of such alumina particles in orbit are also introduced.     

Numerical simulations of water spray on flame deflector during the four-engine rocket launching

This paper aims to study on the cooling effect with two types of water spray nozzle on the flame deflector during the four-engine launch vehicle take-off. To accurately simulate the two-phase flow of the rocket gas with multispecies and the water spray, the three-dimensional compressible Navier-Stokes equations, discrete ordinates methods and realizable k-Ɛ turbulence model are used to establish the rocket supersonic plumes impact model. The Eulerian dispersed phase (EDP) model was used to simulate the water spray into the exhaust gas. The accuracy and effectiveness of the gas-liquid flow model are verified by a good agreement between simulation results and experimental data. On this basis, a series of numerical simulation studies under different water injection position are performed. The results show that the high temperature regions, along the axis of engines on the deflector plate, have no significant temperature decreasing effect by water spray from the nozzles mounted on the apex of the deflector, and the high temperature converts a large quantity of water into vapor near the plume boundary, which would decrease the flow conductivity. With the cooling spray nozzle fixed directly to the deflector plate, the temperature decrease effect is obvious and the effect of thermal shock on deflector plate induced by exhaust plume is reduced, so that it can prevent the flame deflector from thermal ablation. The study results provide indepth information and engineering guidance for designing the water spray systems and increasing the safety of the launch process.     

Study of atmospheric air pollutants during the partial solar eclipse on 15 January 2010 over Udaipur: A semi-arid location in Western India

The paper describes behavior of surface ozone, its precursor gases, BC along with TOCC, TWVC, AOT1020 nm as well as UV and IR radiation intensities observed during the partial solar eclipse of 15th January, 2010 over Udaipur, where 52% solar disc is obscured due to the moon’s shadow. During the beginning to main eclipse phase, the deviation values of several air pollutants concentrations from eclipse to control day values vary in a small range from −9 to −2 ppb in case of surface ozone and −180 to −80 ppb for CO. The corresponding change in the values of BC observed from −3.3 to −.5 μg/m³. No significant change is found in NO₂, NO or in ratio of NO₂/NO values during the partial eclipse time. TOCC values decrease from 3 to 5 DU along with a reduction in UV radiation intensity from 20 to 35% from starting to the main eclipse phase. The AOT1020 nm values are found to increase from .2 to 1.0 along with a reduction in IR radiation intensity order of 50%. However, TWVC values decrease from .22 to .1 cm during the eclipse hours. The low level of dilution in surface ozone in eclipse period may be attributed with change in local atmospheric boundary layer dynamic conditions or limited air pollutants dispersion, in term of decreases in planetary boundary layer height, wind speed and hence ventilation coefficient in the same eclipse hours. Thus, present studies support the argument for the leading roles of photochemical reactions with its precursor gases under presence of solar radiation in surface ozone variability. Other possible controlling factors are advection of air pollutants from the polluted region as evident from backward wind trajectories and altering the local meteorological conditions.