Chemistry research in the space environment was classified into two areas: the area related to chemical processes that become significant under microgravity, and that to chemical reactions in the special environment of space. On this basis, the following subjects for chemistry research in space were considered: 1) chemical processes in critical fluids, 2) dynamics of higher-order structure formation, 3) interfacial phenomena driven by molecular interactions, and 4) chemical kinetics enhanced in space enviroments, such as in the low-orbital condition of atomic-oxygen abundance, at very lowtemperatures on the surface of cosmic dust, etc.

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Non- equilibrium superfluid-normal (SN) interface of liquid He was created by cooling the liquid from the bottom. Propagation of the interfacial wave was observed by visualizing the SN interface using a shadowgraph method. Velocity of the wave was about c=1 cm/sec.

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Adiabatic Demagneti ation Refrigeration (ADR) does not use working fluids contrary to conventional refrigerators that make use of the fluid density difference, which leads to superiority of the ADR under the weak gravity condition. In this study, we will develop a new continuous ADR system to provide the cooling temperatures between 0.06 K and 4 K. The system will consists of multi-stage of magnetic materials and magnets cascaded with heat switches for each tempera- ture range. The ADR cooler is planned to test to confirm the ability of the continuous ADR system under the milli-gravi- ty condition in airborne flight experiments. The ADR development will be accomplished through the collaborative works with NASA/SGFC and AXA/ISAS.

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Recent progress in our study on the behaviors of colloids in hot and compressed water is described. Dynamic light scattering measurements revealed that model colloids, which remain dispersed stably in water at ambient conditions, flocculate rapidly upon hrating under pressure. In order to obtain further insights into the colloidal dispersions at such extreme conditions, an optical microscope system equipped with a high-temperature and -pressure sample chamber was developed. Diffusion coeffcient of polystyrene latex (d＝2.092μm) that undergose Brownian motion near a quartz surface was measured successfully in water at temperatures between 298K and 573K at constant pressure of 24.6 MPa, and abalyzed in terms of a large temprature dependent change of the density of water. Our experomental setups allow performing the measurements even in supercritical water (Tc=647 K, Pc=22.1 MPa). It seems lilely that intense density fluctuation and anomalies of physical properties such as heat capacity and thermal expansion coefficient near the critical point affect the colloidal behaviors. Future sirections of the work in relation to the critical phenomena and possible applications of the experiments under microgravity are discussed.

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In one of the space experiments made by Don Pettit, a liquid film was sustained in a wire ring, and one side of the ring was heated by a soldering iron. Then a convection was induced in the liquid film. Since the liquid film is heated by the soldering iron, one may expect that the flow would be from the heated part to the film center owing to the produced temperature gradient. In the experiment, however, the flow was induced from the film center to the soldering iron. In this study, ground experiments and a numerical simulation have been conducted to investigate a cause of the induced convection.

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A new method of rapid crystal growth from a thin solution film has been proposed, in which NaCl or K-Alum crystals have been grown from a kitchen detergent liquid film held with a thin steel loop, ～φ20. Due to the rapid evaporation of water from the large surface of the thin solution film, the concentration of salt in the liquid rapidly increases and thus crystals grow to a few mm size in a few tens seconds. Crystal nucleation site and movement of crystals grown in the film can be compared with the experiments in the Space Shuttle done by Don Petitt. It is interesting to note that nucleation in microgravity takes place mostly on the surface of the metal loop due to heterogeneous nucleation and then these crystals move toward the center of the loop with the help of Marangoni convection. Whereas, under normal gravity, crystal nucleation takes place at the middle of the liquid film and then these crystals move radially towards outside.

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Behavior of oscillating bubble (s) is of great importance for application under microgravity environment; boiling heat transfer in high performance heat exchanger, removing process of bubbles in material manufacturing, etc. In the present study, shape oscillation of single bubble and its interaction among multiple bubbles under ultrasonic vibration are focused. Through the observation with the high-speed camera, dynamic behaviors of the bubble exhibiting a transition from radial volume oscillation to shape oscillation and the preferable mode number of the shape oscillation were successfully detected.

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The current-voltage characteristics of the array electrodes on the dielectric material in laboratory plasma have been studied in association with the interaction of high-voltage solar array with the ambient space plasma. It has been found that the charging effect and secondary electrons of the dielectric material surrounding the electrodes play an important role in collection of the electrode current. The charging effect suppresses the electrode current, while the secondary electrons enhance the electron current to the electrode. In the electrode array (3 × 3 electrodes separated by 0.5~10 cm) , the current of each electrode was generally smaller than that of single electrode, but a rapid enhancement of the electrode current was observed when spacing of the electrodes was less than 1.5 cm. These results indicate a possibility that we can reduce the risk of electric discharge if we use the dielectric material with a low secondary-emission yield and select the distribution of the solar array voltage minimizing the high voltage-plasma interaction.

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