We determined the emissivity of molten oxides using a commercially available pyrometer combined and an electromagnetic levitation system based on the liquid Fe emissivity and its melting temperature. Our method for determining molten oxide emissivity is based on immiscible molten oxides and liquid Fe. From the processes, we obtained 0.80  0.03 for molten Al2O3 and 0.76  0.01 for our desired molten oxide of SiO2-CaO-Mn3O4-TiO2 system with welding flux model compositions of SiO2:CaO:Mn3O4:TiO2=27:7:13:53 mass% . This is necessary when using ELF (electrostatic levitation furnace) in the ISS (International Space Station) to measure the thermophysical properties of molten oxides. We could correct the temperature monitored with emissivity set at 1 to the real temperature during density measurement by ELF in ISS using normal spectral emissivity for molten SiO2-CaO-Mn3O4-TiO2 system and we find the temperature dependence of molten oxides density of SiO2:CaO:Mn3O4:TiO2=27:7:13:53 mass% in the temperature range of 1200K - 2000K. We also find that the multicomponent oxide system of SiO2-CaO-Mn3O4-TiO2 has a low coefficient of density temperature dependence.

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Fluid behavior in microgravity is different from that in normal gravity since surface tension and wetting are dominant in microgravity. In propellant tanks for future in-orbit spacecraft, sloshing due to disturbance and a settling behavior from changes in acceleration must be understood for the design of the propellant supply system and attitude control system. As a target to understand the liquid behavior when the tank is accelerarated and decelerated in the second-stage rocket propulsion system, this study investigated the liquid behaviors in the cylindrical test tank via microgravity experiments and numerical calculations when the acceleration was applied in the axial direction in microgravity. The effects of acceleration direction (upward and downward), magnitude, and tank size on liquid behavior were clarified. As a result, it was shown that the experimental results agreed with the analytical ones when a large downward axial acceleration was applied, in which the liquid film on the solid wall became thicker. On the other hand, when the axial acceleration was small and the applied direction was upward, the breakage of the liquid film on the solid wall occurred in the numerical calculation, which was not observed in the experiment. From these results, it was shown that it was important to realize the thin liquid film on the solid wall surface by numerical calculations. Furthermore, based on the obtained knowledge, the effect of the liquid behavior under acceleration on the second-stage rocket propulsion system was considered.

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