月球坑内空间环境热流的分布研究

文章推导获得了月面阳光矢量和月球坑内探测器表面关系的表达式,采用蒙特卡罗法数值计算探测器各表面的辐射热流,分析了月球坑内环境辐射热流的分布特征。讨论了月面纬度、月球坑尺寸、月面发射率等参数对探测器表面热流的影响。计算表明:月面纬度增加及月球坑坑口半径的减小均会导致某些时刻阳光无法照射到坑底,从而与其他工况有较大的计算差别,两参数对探测器各面热流的影响规律不同;月面发射率对探测器表面热流的影响作用较大,增加月面发射率能明显降低探测器某些表面的辐射热流。     

Experimental evaluation of the radiative heat flux from rocket plumes on satellite structures

An experimental method capable of directly measuring the net radiant heat flux on complex geometry surfaces by non invasive methods has been devised, designed, realized and tested. The method is based on a computerized thermographic system capable of directly outputting the radiative heat fluxes absorbed by the surface to be examined. The calibration tests have shown the feasibility and the accuracy of the proposed method. Preliminary tests are presented which simulate the radiation flux from a jet exhaust.     

高超声速化学平衡流辐射流场数值解

本文用数值方法研究了高超声速大钝头体绕流辐射流场。采用粘性激波层控制方程和平衡化学反应气体模型。辐射部份包括连续辐射和线辐射。采用切平板辐射输运模型解决了空间推进的问题，计算结果表明：辐射传热与飞行器再入飞行速度，高度及头部半径密切相关，在计算的条件下，当再入速度小于７．６公里／秒时，辐射传热的影响可以忽略，当再入速度为１１公里／秒左右时，辐射传热可以与对流传热相比拟。当再入速度更大时，辐射传热远     

隔热层厚度和数量对太空多层光学窗口温度分布的影响

 航天器上常安装有用于科学观察的多层光学窗口,其温度分布的均匀性会影响成像质量。运用射线踪迹-节点分析法的任意多层镜反射辐射与导热耦合换热模型,研究了隔热层厚度及数量对太空中多层光学窗口温度分布的影响。光学窗口的吸收系数、折射率随波长的变化用一组矩形谱带来近似。研究显示太空中热辐射在光学窗口的冷却过程中起着非常重要的作用,在离玻璃层表面附近很薄的一层玻璃介质内,辐射与导热存在强烈的耦合作用。隔热层厚度越薄,其内的温度分布越均匀,有利于提高成像质量。隔热层数量越多,光学窗口各层玻璃的温度分布越均匀,有利于提高成像质量,但是隔热层最佳数量的确定还需综合考虑其它因素。     

空间辐射散热器含液滴介质的辐射特性和辐射传热

本文从米氏电磁散射理论出发，计算了含液滴介质的辐射特性。考察了中向同性散射能量传递份额的再分配，导出了吸收、发射、各几同性散射介质的辐射传递系数。计算了空间辐射散热器液滴层瞬态辐射换热，经与文献［４，５］的比较表明，本文所导出的辐射传递系数计算方法正确，精度高。用计算机辅助实验，分析液滴发生器产生粒子的大小、粒径分布对瞬态辐射换热的影响，可减少空间辐射散热器设计过程中的实验次数。     

Radiative Electrification of Spacecraft Construction Elements: Physical Modeling of Charge Accumulation and Neutralization

The basic principles of physical modeling of spacecraft radiative electrification in the ionosphere and the magnetosphere are formulated. It is shown that recorded cyclograms and current pulses of discharges provide complete information on the electrophysical properties of materials. The efficiency of plasma neutralization of electro-radiative effects depends on the density of low temperature plasma and the structure of the irradiated surface.     

火星进入气体辐射加热研究进展

针对飞行器进入火星大气时气体辐射加热对防热设计带来不确定性，在简述火星探测和气体辐射研究的发展历程的基础上，对火星进入气体辐射加热研究的进展进行综述。首先，针对火星大气环境描述了气体辐射加热的概念和问题由来。其次，重点综述了近年来火星进入气体辐射加热基础模型的数值和试验研究进展，其中包括：热化学非平衡气体动力学、气体辐射特性和辐射传输的计算模型与方法等数值研究；地面测试设备、试验技术和模拟火星大气环境的气体辐射测量与验证等试验研究。再次，综述了流动辐射耦合和后体气体辐射加热等火星进入器设计方面开展的研究。最后，对未来火星进入气体辐射加热研究进行了展望，提出了研究建议。     

薄膜二次表面镜热控涂层的辐射物性分析

认识热控涂层的热辐射物性对航天器热控制设计具有重要指导作用。文章根据薄膜二次表面镜涂层的吸收与反射过程分析,建立模型方程,结合已有的太阳吸收比、红外发射率等表观数据,采用非线性参数最小二乘法获得了薄膜材料的吸收系数和反射率等辐射物性,并分析了厚度对热控涂层太阳吸收比和红外发射率的影响。研究结果表明,聚酰亚胺薄膜对太阳光的表面反射率为0.571,吸收系数为19.343 mm-1,对红外辐射的表面反射率为0.227,吸收系数为39.615mm-1;F46薄膜对太阳光的表面反射率为0.744,吸收系数为0.757mm-1,对红外辐射的表面反射率为0.111,吸收系数为9.240mm-1。     

Parameterization of surface temperature retrieval for remote sensing experiments

A simple parameterization has been developed for determining the actual surface temperature from the effective brightness temperature measured radiometrically in the 11 μm window region. This algorithm allows the computation of atmospheric correction without performing detailed radiative transfer calculations. Correction due to atmospheric water vapor is represented in terms of the integrated water vapor burden. Correction due to variation of surface emittance is represented in terms of its deviation from unity. Parameteric representation has also been developed for simultaneous variation of both parameters. The parameterization is based on model calculations performed with a line-by-line radiative transfer program. Sensitivity of the retrieved surface temperature to uncertainties of water vapor burden and surface emittance have also been examined.     

发动机和羽流对地球同步卫星底部辐射加热的计算研究

地球同步卫星工作过程中法兰底座所受的辐射加热对法兰上的控制开关等零件的安全有重要影响。为此,建立了节点网络法计算发动机和隔热屏对卫星法兰底座及控制开关的辐射加热,比较了发动机、隔热屏和羽流3种辐射源的作用大小,还研究了发动机位置的平移对底部法兰及控制开关辐射加热的影响。研究表明:羽流对法兰和控制开关的辐射热流最小,发动机对法兰和控制开关的辐射热流最大;法兰和控制开关上不同侧面受到的辐射加热很不均匀,面向发动机正面的侧面辐射加热最强,面向发动机头部的侧面辐射最小;发动机向后平移可以显著降低法兰和控制开关上辐射热流的最大值。     

Role of interface deformations in Benard-Marangoni instability

This work is concerned with a linear analysis of natural thermoconvection in a two-layer system formed by a liquid surmounted by an upper immiscible gas layer (Bénard-Marangoni problem). Emphasis is put on the role of the air layer on the thermoconvective instability. It is shown that the motion inside the gas phase can be disregarded provided its thickness is smaller than the thickness of the liquid layer. The gas can then be modelled as a purely conductive medium. Another important problem discussed here is the role of surface deformations on the onset of convection. In that respect, the use of Boussinesq's approximation is discussed and its limits of validity are specified. The main results are the following. First, it is concluded that overstability cannot be observed in ordinary fluids under realistic experimental conditions. Besides, it is shown that, among the relatively larger number of parameters appearing in the problem, the viscosity is by far the most important. Moreover, new dimensionless numbers are introduced to better apprehend the physical context. The experimental conditions required to observe the surface zero-wave number instability are also determined, as well as the conditions under which gravity effects may be neglected on earth. Finally it is examined under which circumstances the interface can be considered as remaining flat.     

Uniform solution for the flow past a slender body with an attached shock wave in radiative magnetogasdynamics

A systematic perturbation scheme is used to study the propagation of a weak shock wave attached to a slender body in a supersonic flow of plasma with thermal radiation and investigate as to how the coupling between the radiative transfer and magneto-hydrodynamic phenomena affects the flow field. The analytical solution of the flow field has been presented up to the second order of ε. The shape of the shock wave attached to the slender body of revolution is obtained, which however can be expressed explicitly in terms of known functions when the radiative decay length is of the same order as the typical body length. Also, the shock angle at the tip of the projectile is obtained.     

On radiative and conductive heat transfer in spacecraft

The “radiative” boundary condition in a heat conduction problem relates the heat flux in a point of the wall to the temperatures in all the other points of the surface system.That is, this condition is of a “functional” type. This “functional” can be solved in discrete terms by using the conventional technique of dividing the body in small discrete elements or “nodes”. This paper instead presents an approach on a continuous scheme, by which the functional is solved in terms of “spacewise harmonics” of the temperature inside the body; the heat conduction problem is thus reduced to an ordinary form differential system whose unknowns are these “harmonics”. An interative linearized procedure to solve this system is also suggested, by which “exact” solutions are obtained. The merits of these solutions, with respect to practical discrete element computations, are in the better spacewise resolution and in the consequent more accurate treatment of both radiation and conduction. The application of the procedure is, however, limited to particular geometries. It is relevant to note that among these possible geometries many are included of practical interest, like hollow cylinders and polygons, cubic boxes etc. A numerical example completes the work.     

Using biogenic sulfur gases as remotely detectable biosignatures on anoxic planets

We used one-dimensional photochemical and radiative transfer models to study the potential of organic sulfur compounds (CS(2), OCS, CH(3)SH, CH(3)SCH(3), and CH(3)S(2)CH(3)) to act as remotely detectable biosignatures in anoxic exoplanetary atmospheres. Concentrations of organic sulfur gases were predicted for various biogenic sulfur fluxes into anoxic atmospheres and were found to increase with decreasing UV fluxes. Dimethyl sulfide (CH(3)SCH(3), or DMS) and dimethyl disulfide (CH(3)S(2)CH(3), or DMDS) concentrations could increase to remotely detectable levels, but only in cases of extremely low UV fluxes, which may occur in the habitable zone of an inactive M dwarf. The most detectable feature of organic sulfur gases is an indirect one that results from an increase in ethane (C(2)H(6)) over that which would be predicted based on the planet's methane (CH(4)) concentration. Thus, a characterization mission could detect these organic sulfur gases-and therefore the life that produces them-if it could sufficiently quantify the ethane and methane in the exoplanet's atmosphere.     

Diurnal change of MW and IR thermal emissions from lunar craters with relevance to rock abundance

Abnormal “hot spots” during a total eclipse on the lunar surface were revealed by using a ground based infrared (IR) scanner and visible telescope in the early 1960s, which turned out to be “cold spots” on the microwave (MW) brightness temperature distribution at night according to the Chang'E (CE)-1 radiometer's observations. In this paper, a theoretical analysis of radiative transfer is presented to explain this abnormal phenomenon of diurnal changes. Two typical craters, representing the abnormal fresh craters rich in rock abundance and an old one almost free of rocks located at similar latitudes are chosen for comparison of the diurnal temperature change. Using the measurements of CE-1 multi-channel microwave radiometer, brightness temperatures from these two craters are presented and applied to inversions of the physical temperatures of lunar regolith media, based on a three-layer radiative transfer model. The correlation between the diurnal MW and IR thermal changes of the lunar surface and the rock abundance is discussed.     

单元表面间辐射传递系数的新型计算方法

通过对辐射能量传递过程的分解，建立辐射传递系数与角系数之间的关系，提出了一种计算具有漫反射辐射界面特性的单元表面之间辐射传递系数的新型计算方法。该方法分离了单元表面辐射特性和几何特性对辐射传递系数的影响。分别采用新方法和蒙特卡洛法计算了立方体内部单元表面之间的辐射传递系数，并且从理论上对两种计算方法的耗时性和计算精度进行了分析比较。结果表明，相对于蒙特卡洛法，该方法所需的计算时间更少，而且不随单元表面吸收率的变化而变化；在计算精度上，该方法相对于蒙特卡洛法具有更高计算精度。     

地球与大气反射光对空间光学传感器探测能力的影响仿真研究

现有辐射计算模型不考虑地表的各向异性特征,导致计算结果存在较大误差。针对这一问题,提出一种新的地球与大气反射光对传感器照度贡献的计算模型,考虑了地表反射、大气散射和辐射传输三方面的影响因素;在此基础上提出一种启发式蒙特卡罗重点光线采样方法,该方法根据给定的传感器参数和空间几何参数高效解算地球与大气反射光对空间光学传感器探测能力的影响程度。     

The effect of a strong stellar flare on the atmospheric chemistry of an earth-like planet orbiting an M dwarf

Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high-energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect, we estimated a proton flux associated with the flare of 5.9?×?10? protons cm?2 sr?1 s?1 for particles with energies >10?MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the Carrington event. The simulations were performed with a 1-D photochemical model coupled to a 1-D radiative/convective model. Our results indicate that the UV radiation emitted during the flare does not produce a significant change in the ozone column depth of the planet. When the action of protons is included, the ozone depletion reaches a maximum of 94% two years after the flare for a planet with no magnetic field. At the peak of the flare, the calculated UV fluxes that reach the surface, in the wavelength ranges that are damaging for life, exceed those received on Earth during less than 100?s. Therefore, flares may not present a direct hazard for life on the surface of an orbiting habitable planet. Given that AD Leo is one of the most magnetically active M dwarfs known, this conclusion should apply to planets around other M dwarfs with lower levels of chromospheric activity.     

发射特性对线性各向异性散射介质内瞬态温度分布的影响

考虑各向异性散射介质内的辐射传递方向，本文考察了辐射能的重新分配过程。利用射线踪迹法结合Hottel和Sarofim区域法推导了辐射传递系数(RTCs)。考虑一维各向异性参与性半透明灰介质。两边界表面为镜反射，一个表面半透明，另一个表面不透明。辐射传递系数用于计算辐射热源项。瞬态能量方程由全隐式控制容积法求解。外界辐射加热与对流冷却同时作用于边界表面。考虑四个线性散射相函数。以各向同性散射情况比较，研究不透明边界两侧发射特性和线性散射相函数对瞬态温度分布的影响。结果表明，各向异性散射与各向同性散射介质间的相对温度差异与散射不对称参数近似成正比。     

Fluid flow interaction with an obstacle near free surface

The two-dimensional problem of thin obstacle interaction with compressible fluid flow near free surface under microgravity was regarded. The fluid was assumed occupying infinite semi-space, gravity was neglected as compared with fluid inertia. The obtained exact solution shows that for relatively thin layer the resistance force does not depend on the layer thickness, but depend on body length and inclination angle, and surpasses twice the respective values for the infinite medium, which could be explained by additional wave resistance arising in the presence of free surface.