The history of the Space Shuttle is already a quarter century and it's retirement is scheduled in the near future in theend. To seek for the next generation of the manned space flight, looking around the past space experiment which is theroad to the model specimen experiment today, and think about the direction we are going to.
The nematode Caenorhabditis elegans is a useful experimental organism for studies on several biological functions because the whole genome has already determined and cell genealogy has been cleared. International Caenorhabditis elegans Experiment-1 (ICE-First) was carried out using Russian Soyuz from April 19 to 30, 2004. JAXA participated in this international cooperative experiment, and acquired the flight samples of C. elegans. JAXA organized the research team and focuses on the following investigations: 1) the role of signal transduction regarding small G protein, Rho, in a gravity sensing mechanism and neural development, 2) whether meiotic chromosomal dynamics and apoptosis in the germ cells are carried out under microgravity condition, 3) the effects of microgravity on cell migration and muscle development, 4) how microgravity affect the aging process. The post flight analyses of above investigations are in progress. In this manuscript, we would like to introduce the ICE-First mission.
The United States of America, Japan, Canada, Russia, and European countries are cooperating to construct and utilize an International Space Station (ISS) . The ISS will be an important facility for space experiments, and will also serve as a symbol of international cooperation and worldwide peace. A centrifugation system is scheduled to be included as part of a laboratory designed to pursue gravitational biology research in the ISS program. Many scientists expect to make use of this centrifuge system for space experiments in orbit in a space environment which will be subjected to microgravity and space radiation. Astronauts have been constantly exposed to space radiation at a dose rate 100 times higher than at the Earth's surface, and thus it is desirable to study the effects of space radiation to learn what the effects will be on human health. It is extremely difficult to reproduce a space radiation environment in a laboratory on the Earth's surface. In addition, it has been reported that the biological effects of space radiation are modified by microgravity. In order to understand the biological effects of space radiation and any interaction with microgravity, the ISS centrifugation system will be a critical tool, and it is hoped that this system will be in operation as soon as possible.
The International Space Station (ISS) will provide a permanent laboratory to address fundamental questions on the influences of a variety of gravity levels on living organisms. To aid in this endeavor, gravitational biology research facility, or ‘‘Centrifuge’’, for the Space Station is currently under development. In practice, long-term habitation in space, settlement on the Moon, and travel to Mars all require that we learn how to sustain life in a variety of gravitational environments, and this facility also includes the capability to provide ‘‘reduced gravity’’ likely on the Moon or on Mars in ways impossible on Earth. This means that the on-orbit studies attainable in the Centrifuge are essential to the future of our space exploration efforts. According to the bilateral barter agreement between the Japanese Space Agency (JAXA) and NASA, JAXA is providing the three payloads, i.e., the Centrifuge Rotor (CR) , Life Sciences Glovebox (LSG) and Centrifuge Accommodation Module (CAM) in exchange for Shuttle transportation oftheJapanese Experiment Module to the station. In the current schedules, the LSG and CR/CAM will be transported to the Kennedy Space Center in Florida in early 2006 and December 2007, respectively. Given the grounding of the Space Shuttle fleet following the Feb. 2003 loss of the Columbia, LSG and CR/CAM launches re-plan efforts are underway.
Aquatic animals, such as small freshwater fish or amphibians, are excellent model both for ground and space experiments. We have developed aquatic animal experiment hardware for Space Shuttle missions from 1992 to 1998. Also, we have been performing technical studies to develop advanced experiment hardware, Aquatic Habitat (AQH) , for longterm experiments in the International Space Station. The AQH will have the capabilities to accommodate three-generations of small freshwater fish (medaka and zebra fish) and egg through metamorphosis of amphibian (African clawed frog). For these purposes, the AQH will have the many brand-new capabilities that the previous facilities have never had. Currently, we are preparing for the start of flight hardware development. In addition, we are advancing another technical studies aiming at precursor mission that precedes the experiments in the International Space Station.
For exact diffusion measurements of liquid metals we improved the shear cell technique which is available for both under , μg-conditions (Foton-M2 satellite mission) and under 1 g-conditions. The main points of the design were minimization of the shear convection, minimization of the Marangoni convection, and improvement of reliable operation. The effect of the shear convection was investigated by short time diffusion experiments both under low-g (parabolic flight in a plane) and under 1 g. As the result the additional mean square diffusion depth caused by the shear convection turned out to be in the order of 10-7 m2, which is smaller than 1% of the usual mean square diffusion depth. We found a correction method for the additional diffusion depth. Using the shear cell diffusion experiments in Sn-Bi, In-Sn, and Al-Ni alloys were performed, with a stable density layering under 1 g-conditions. The concentration profile at each experiment was obtained by the analysis of atom absorption spectroscopy (AAS) and yielded the diffusion coefficient by using the correction method. The diffusion coefficients were the same as the μg-reference data and those from the magnetic field under 1 g-conditions. The temperature dependence of the diffusion coefficient obeyed the power law. On the basis of these results the diffusion types were classified according to the reliability of 1g-measurement.
Experiments have been carried out to throw light on some basic features of solid waste fuels in an atmosphere of high temperature and low oxygen concentration under microgravity. The microgravity environment makes it possible to examine fundamental combustion characteristics of waste fuels by realizing spherical symmetry and by distinguishing radiation dominated processes from convection dominated ones. The range of ambient temperature and oxygen concentration in the electric furnace are 600°C to 1000°C and 7% to 21% by volume, respectively. The mechanism on ignition and flame development has been analyzed in detail against ambient temperature and oxygen concentration