Characterization of Multiband Imager Aboard SELENE

The Multiband Imager (MI) is a high-resolution, multi-spectral imaging instrument for lunar exploration. It consists of two cameras, VIS and NIR, and is carried on the SELenological and ENgineering Explorer (SELENE), launched on Sep. 14, 2007. During the observation from January 2008 to June 2009, MI acquired about 450,000 scenes of multispectral image. The radiometric properties of the cameras were characterized using the pre-flight data derived in laboratory experiments with a calibrated integrating sphere. Twelve light source sets were used to examine the S/N ratio, linearity, and saturation level of the cameras. The dark field signal is quite stable in both cameras, having a noise level of less than 1 DN (VIS) and 2 DN (NIR). The fluctuation in the light field is also low (<2 DN), indicating that the spatial nonuniformity in the camera responses can be removed using a flat field. In order to remove the smear signals due to the frame transfer in the VIS data, we developed an iterate algorithm using all bands in the VIS camera. The S/N ratio, which is critical to the precision of the product, is estimated to exceed 160 for the VIS bands and 400 for the NIR bands under low illumination conditions (5% of lunar surface reflectance). Based on the S/N ratio, the radiometric error due to the noise is calculated to be less than 0.7% for VIS and 0.2% for NIR. The relationship between input and output of the VIS camera is linear with a residual of less than 0.6 DN, corresponding to a radiometric error of 0.3%. The NIR exhibits a non-linear response to the input radiance. A cubic function best fits the pre-flight data with an average residual of 8 DN (corresponds to an error of 0.8%). Validation using in-flight data indicated that the instability of the dark output has not changed, but the level of dark output has slightly changed in the NIR bands (less than 6 DN). The pixel-to-pixel sensitivity variation in the orbit has been changed from that in the pre-flight experiment. The difference between the in-flight data and the pre-flight data ranges within ±2%. There is also a small (less than ±1%) but nonnegligible difference between in-flight data of different cycles in both the VIS and NIR bands, suggesting that the coefficient for spatial ununiformity correction needs to be calculated for each cycle.     

液晶显示方法研究管内马赫数4拟似冲击波流动

在一个压力-真空型超声速风洞中, 剪切应力敏感的液晶表面流动显示技术被用来研究方管内马赫数4拟似冲击波的超声速流动.实验是在日本室兰工业大学的超声速风洞中进行.它提供了关于测试表面流动结构的定性信息,诸如湍流边界层分离和再附, 以及边界层流动的维数等.液晶显示结果与纹影实验照片和油膜方法进行比较,证实了它是一种非常有效的表面流动显示工具.     

八面体桁架结构在内冷通道中的流动传热特性研究

为探究八面体桁架结构在航空发动机热端部件内冷通道中的可应用性,掌握八面体桁架结构的流动传热特性,本文采用理论推导和三维数值模拟的方法,对八面体桁架单体的有效导热系数以及八面体桁架阵列结构的流动结构和传热性能开展了研究。首先,针对八面体桁架单体结构,推导出了考虑节点效应的有效导热系数关系式,并通过与数值计算结果对比,验证了其有效性。其次,针对八面体桁架阵列结构,开展了整体结构的三维数值计算,分析了其内部通道的流动结构和温度分布,获得了不同结构的流动阻力和对流传热系数随雷诺数的变化规律。最后,考虑到结构的综合传热性能,本文针对不同孔隙率的八面体桁架阵列结构,进行了基于相同泵功率下努塞尔数的对比。根据计算结果,本文给出了获得最佳传热性能的无量纲直径范围0.07~0.08,相应的孔隙率变化范围 0.872~0.841。分析其原因,由于随着结构孔隙率的减小,即固体率的增加,对流传热强度不断提高,然而,当孔隙率减小到84.1%以下时,由于内通道中流动阻力骤然增大,导致传热效率降低。将八面体桁架结构应用于航空发动机热端部件内冷通道中,是同时出于高效冷却和力学性能的考虑,本文掌握八面体桁架阵列结构的流动传热特性,为其在实际工程中的应用提供了理论支撑。     

The second stage propulsion system for N-launch vehicle

The pressure-fed second stage propulsion system for N-launch vehicle provides 53,348 N (5440 kg) thrust for about 250 sec at an Isp of 290.2 sec. Aluminum tanks, integral with vehicle structure, carry a minimum of 4.7 ton propellant combination of N₂O₄ and Aerozine 50. The gimbaled engine consists of a regenerative cooled chamber, ablative nozzle spacer, and a radiation cooled nozzle extension with an exit area ratio of 26. Utmost utilization of domestically available technology and facilities underlay the design concept. Development of the propulsion system took 5 years with the first flight occurring in 1975. Five consecutive flight successes up to 1979 have demonstrated the reliability and performance of the system.Improved N vehicle, designated as N-II, will succeed the N vehicle. New second stage propulsion system for N-II delivers 43,816 N (4468 kg) thrust at an Isp of 314.1 sec and has restart-capability.     

液晶流动可视化方法研究拟似冲击波的内部超声速流

在一个压力一真空超声速风洞中,剪切应力敏感液晶流动可视化技术被应用来研究方管内马赫数2拟似冲击波（pseudo-shockwave）的超声速流动。它主要提供关于整个流动的定性信息,诸如湍流边界层分离、再附着位置以及流动的维数等。而且液晶也反映了表面流线,分离区内的涡流和管道流动的角效应。使用两种不同黏度的液晶分别进行实验,分析黏度对结果的影响。液晶实验的结果与纹影照片所得结果比较吻合,说明了液晶是一个非常有效的流动可视化工具。     

Vapor compression distiller and membrane technology for water revitalization.

Water revitalization for a space station can consist of membrane filtration processes and a distillation process. Water recycling equipment using membrane filtration processes was manufactured for ground testing. It was assembled using commercially available components. Two systems for the distillation are studied; one is an absorption type thermopervaporation cell and the other is a vapor compression distiller. Absorption type thermopervaporation able to easily produce condensed water under zero gravity was investigated experimentally and through simulated calculation. The vapor compression distiller was studied experimentally and it offers significant energy savings for evaporation of water.