論文

In recent planetary exploration space missions, spacecraft are exposed to severe thermal environments that are sometimes more extreme than those experienced in earth orbits. The development of advanced thermal control materials and devices together with reliable and accurate measurements of their thermophysical properties are needed for the development of systems designed to meet the engineering challenges associated with these space missions. We provide a comprehensive review of the state-of-the-art advanced passive thermal control materials and devices that are available for space applications, specifically, variable emissivity thermal control materials and microelectromechanical systems (MEMS), radiofrequency (RF)-transparent and/or tunable solar absorptivity and total hemispherical emissivity thermal control materials, and a passive re-deployable radiator with advanced materials and insulation. Prior to our in-depth review of these thermal control materials, we briefly summarize the thermal environments surrounding spacecraft, the characteristics of thermophysical properties for spacecraft materials that differ from those of materials for ground use, and the significance of solar absorptivity and total hemispherical emissivity for passive thermal control in space. In all four topics of materials and devices, the following subjects are overviewed: the basic principle of passive thermal control techniques in space, the measurement of thermophysical properties of those novel materials, simulation and/or on-orbit verification thermal performance tests, degradation tests in space environments, and some aspects of the implementation of the above-described materials and devices in actual space missions.

Mass diffusion coefficient measurement techniques with high temporal and spatial resolution have become essential for the research and development of leading-edge technology in a wide range of cross-disciplinary fields, but cannot be achieved using conventional methods. We provide a comprehensive review of the state-of-the-art theoretical and experimental investigations on Soret forced Rayleigh scattering (SFRS), a grating excitation technique (GET) for measuring the mass diffusion coefficient of binary liquid mixtures. SFRS utilizes the Soret effect to create micrometer-order periodic spatial concentration modulation in a sample due to the absorption of an optical interference grating generated by two intersecting heating laser beams. The decay of the concentration modulation by the mass diffusion process within several milliseconds is detected by the diffraction of a probing beam. The theoretical considerations regarding deviations from the ideal mass diffusion conditions are the effects of: (1) the Gaussian beam intensity distribution, (2) the light absorbing material and (3) the cell wall. The proper settings for the optical system are also analyzed, e.g., the effect of coherency and polarization of the heating laser and the effect of the z-direction length of the interference region. We also consider the frame of reference, center of gravity invariance and effect of convection, which are particularly important for mass diffusion experiments. Using the correct implementation of the theory, the optimal SFRS apparatus design and its appropriate use are described in detail. Finally, two successful applications of SFRS are demonstrated using visible light laser heating and mid-wavelength infrared gas laser heating.