Yuko Inatomi

Scope of biological science in space is widely discussed with the long ranged planning of space science. Three sub-discipline defined are; astrobiology to explore the origin of life in solar system, planetary biology to understand evolution and adaptation of living organisms against planetary environment of Earth, and biological/ecological engineering to extend human presence in space. Space agriculture relates to all three supporting astrobiology exploration on Mars, based on basic knowledge of planetary biology. The concept of space agriculture has been developed with model space menu based on nutritional requirements and productivity at limited resource of farming area and other aspects. Combination of rice, sweet potato, soybean, green-yellow vegetable, silkworm pupa, loach fish, and sodium salt was selected. Co-culture of rice, azolla and loach is a candidate of space farming. Generation of agricultural soil was considered of Martian regolith mixed with compost of inedible biomass and human metabolic waste. Several concepts were compared for the recycle loop of sodium and potassium. Marine macro-algae, ulva, and halophyte species, iceplant are studied for this purpose. Fundamental characteristics of these two species are examined.

The Twenty-second Space Utilization Symposium (January 17-19, 2006: Science Council of Japan, Roppongi, Tokyo, Japan)This working group was started for joint research for thin films and fine powders of carbon and related materials, specially aimed for the future microgravity environmental experiment for diamond or fullerene synthesis.Meeting sponsors: The Science Council of Japan, The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS)(JAXA)

The Twenty-second Space Utilization Symposium (January 17-19, 2006: Science Council of Japan, Roppongi, Tokyo, Japan)Achievement of an extremely weak state of natural convection by utilization of microgravity environment is regarded as a promising method which leads us to investigate the influence of convection on growth process from liquid phase on the terrestrial condition. A main subject of this working group is to make proposals for microgravity experiments concerning to a bulk crystal growth from solution or from melt.Meeting sponsors: The Science Council of Japan, The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS)(JAXA)

The following results are described in the present report.(1) In situ observation experiments of semiconductor solution growth using a near-infrared microscope have been performed to investigate an influence of surface orientation of a substrate crystal upon the morphological change of the solid/liquid (S/L) interface. The orientation dependence of step kinetic coefficient at the interface in GaP/GaP growth was obtained under a reduced convection condition in order to evaluate a behavior of macrosteps during the growth. A morphological change of a S/L interface at the early stage of GaAs_xP_<1-x>/GaP hetero-LPE growth was also discussed from the view point of the surface orientation dependence. (2) A S/L interface of a CdZnTe crystal grown from Te solution with a traveling heater method under a static magnetic field was investigated by a quenching technique during the crystal growth. The results shows that a high quality CdZnTe crystal can be obtained even with high growth rate by damping the buoyancy convection.

In situ observations were carried out in faceted transparent organic materials grown unidirectionally by multiwavelength interferometry, which enabled us to measure the distribution of temperature and solute concentration distributions in the liquid in the vicinity of the solid/liquid interface simultaneously. The aim of the experiments was to reveal a mechanism of a faceted cellular array growth taking account of an influence of latent heat of fusion of the material upon a temperature distribution in the melt. Some experimental results were briefly summarized in the present report.

The purpose of the present study was to investigate a suitable condition to damp the convection in order to measure a reliable diffusion coefficient in electrically conducting liquid under the terrestrial condition by utilizing a static magnetic field based on a numerical simulation. Consequently, application of an axial magnetic field is not effective to damp effect on the convection in melt with high aspect ratio.

Under the microgravity environment, it is considered that thermal convection is suppressed. Therefore, diffusion becomes the main factor of material transport. Thus it is expected that one can synthesize materials with fewer defects or unique structures and get new information about the growth mechanism of materials. Diamond possesses superior properties, for example, high hardness, high thermal conductivity, high transparency, high electron and hole mobilities, and a wide bandgap. These unique properties suggest many potential applications. The conventional techniques for depositing diamond at low pressure utilize a flow of a hydrocarbon-hydrogen gas mixture with complicated gas tubing for introducing the reaction gas into a reaction chamber and evacuating reactant gas from it. For few years, one of us (YT) had been concentrated on developing completely closed diamond synthesizing system aimed for microgravity conditions. With our experiments, we successfully confirmed that diamond was synthesized with this completely closed system, and that this system was very suitable for mounting on large centrifuges and in spacecraft.

In this research, the morphological changes during GaP LPE growth of the S/L interface were observed under strong static magnetic field using near-infrared microscopic interferometer. We discussed the damping effect of convection on the surface morphology during dissolution and growth.

The concentration distribution change in a hen-egg-white lysozyme solution was measured in situ using a microscopic interferometry to investigate the influence of the magnetic field on the process of protein crystal growth. It was found that highly oriented lysozyme crystals were obtained under a magnetic field without any apparent change of solubility. Some influences on the growth kinetics in the early stages of the crystal growth were also found in this research.

In situ observation experiments of GaAs_xP_<1-x>/GaP LPE growth were performed to investigate the influence of the surface orientation of the substrates upon the morphological change at the early stage of the growth.