High Resolution Synchrotron X-Radiation Diffraction Imaging of Crystals Grown in Microgravity and Closely Related Terrestrial Crystals

Irregularities in three crystals grown in space and in four terrestrial crystals grown under otherwise comparable conditions have been observed in high resolution diffraction imaging. The images provide important new clues to the nature and origins of irregularities in each crystal. For two of the materials, mercuric iodide and lead tin telluride, more than one phase (an array of non diffracting inclusions) was observed in terrestrial samples; but the formation of these multiple phases appears to have been suppressed in directly comparable crystals grown in microgravity. The terrestrial seed crystal of triglycine sulfate displayed an unexpected layered structure, which propagated during directly comparable space growth. Terrestrial Bridgman regrowth of gallium arsenide revealed a mesoscopic structure substantially different from that of the original Czochralski material. A directly comparable crystal is to be grown shortly in space.     

Measurement of the thermal conductivity of molten InSb under microgravity

Thermal conductivity of molten InSb was measured on board the TEXUS-24 sounding rocket by the transient hot-wire method using the originally designed thermal conductivity measurement facility (TCMF). Measurements made through this facility were affected by natural convection on the ground. This natural convection was confirmed to be sufficiently suppressed during a microgravity environment. The thermal conductivity of molten InSb was 15.8 and 18.2 W·m^–1·K^–1 at 830 and 890 K, respectively.     

Effect of baffles on orbital accelerations - Induced bubble oscillations in microgravity

The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations with partially-filled rotating fluids has been studied. Present study is applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffle. Results of slosh wave excitation along the liquid—vapor interface induced by jitter acceleration-dominated orbital accelerations provide a torsional moment with an up-and-down movement of bubble oscillations in the rotating dewar. The results show rightward and leftward movement of bubble oscillations transverse to the rotating axis, and up-and-down movement of bubble oscillations longitudinal to the rotating axis of dewar container. The orbital accelerations also induce an eccentric contour of bubble oscillations in a horizontal r—θ plane. As viscous force between liquid—solid interface, and surface tension force between liquid—vapor—solid interface can greatly contribute to the damping effect of slosh wave excitation, the rotating dewar with baffle provides more areas of liquid—solid and liquid—vapor—solid interfaces than that of a rotating dewar without baffle. Results show that the damping effect provide by a baffle reduce the amplitude of slosh wave excitation and reduce the degree of asymmetry in liquid—vapor distribution. Computation of bubble (helium vapor) mass center fluctuations also verifies that a rotating dewar with baffle produces less fluctuations than that of a rotating dewar without baffle.     

微重力环境对层流射流扩散火焰形貌特征的影响

研究微重力环境下层流射流扩散火焰的形貌特征,可为航天领域中火灾探测的研究提供理论支持。本文首先选取可控的层流射流扩散火焰,对火焰炭黑特性及其对火焰温度和热辐射的影响进行了理论分析。其次,在国家微重力实验室落塔设备中进行实验,微重力水平可达10-2~10-3 g,实验结果表明,微重力环境下随着伴流空气速度增大火焰亮度增大,火焰辐射分数降低,火焰温度升高,同时火焰内高温区位于火焰两翼处。     

溶质表面张力对流模型及其对空间实验的解析

空间高温实时观察装置（SHITISOI）被用于观察和记录在Li₂B₄O₇溶体中KNbO₃胞状结晶的整个生长过程,并对胞状结晶生长过程中浮力对流和表面张力对流的影响进行了研究．首次观察到空间条件下,Li₂B₄O₇溶体中稳态表面张力对流图像,它呈镜面对称的抛物线状．由于表面张力对流的作用,KNbO₃胞晶生长且充满了整个的溶体．而在地面上,由于浮力抑制表面张力,降低了胞晶在流体中的生长速度,使溶质KNbO₃胞晶在Li₂B₄O₇溶体中分布不均匀,本文还提出了胞状结晶生长理论的模型．这个模型的主要特点是表面张力对流起始于KNbO₃胞晶的界面上;这是由于KNbO₃溶质扩散速率减少而引起的KNbO₃溶质表面张力梯度．本模型的预言和实验所观察的现象吻合得比较好,这说明该理论模型是合理、可靠的．     

在空间（微重力）凝固的金属材料

简述了与新材料开发相关的空间微重力科学研究成果以及在此基础研制的新产品。求救空间微重力科学应从事更多有应用背景的基础研究,为工业产业奠定理论基础。     

空间烟幕的扩散机理及衰减性能研究

烟幕干扰是针对红外探测器的一种无源干扰手段,在战场环境中,可以在目标与探测器之间释放烟幕形成屏障,降低探测器对目标的能见度,达到对目标的有效遮蔽。首先研究了在微重力高真空环境中,采用气固两相流喷射方法形成烟幕云的机理,并进行了数值模拟。然后,基于烟幕的扩散规律、材料特性及其吸收、散射和反射能力,建立了空间烟幕对红外信号的衰减性能模型。最后,基于实例仿真验证了利用空间烟幕衰减目标红外信号的可行性。     

磁补偿微重力环境实现及磁流体微重力内角流动研究

由于表面张力的作用,流体在微重力环境中沿一定夹角的内角壁面爬升过程与常重力状态不同。为了对微重力内角流动的物理过程进行研究,利用磁补偿方法搭建了常温磁流体微重力补偿实验台,实现了目标区域内纵向小于5%非均匀度的磁补偿微重力环境。并对不同重力条件下水基磁流体沿若干材料内角爬升过程进行了可视化实验研究,探究了微重力环境下流体与材料间的接触角以及内角角度对液体导流性能的影响以及毛细流动规律。结果表明,在满足Concus-Finn条件时,液面爬升高度和重力加速度近似呈反比关系。接触角和内角角度越小,流体输运能力越强,且重力水平越低,越为明显。当不满足Concus-Finn条件时,液面爬升高度和重力加速度近似呈线性关系,接触角和内角角度对流体输运能力的影响并不明显。