Japanese universities recently began to develop small satellites for educational purpose. These activities are primary for education; i.e. to provide students with opportunities to experience the whole cycle of space projects including mission conceptualization, design, fabrication, test, launch, operation and analysis of the results. However, they are also aiming for the ``university type'' contribution to the actual space development, by, for example, providing quick and cheap space demonstration opportunities with university small satellites or finding new seeds for future space technologies. Micro gravity experiment has provided a unique and effective opportunity to evaluate the onboard equipment on ground or verify the feasibility of experiments to be done on small satellites. This paper reviews the current status of small satellite development activities in Japan and micro gravity experiments utilized for them, and then discuss the requirements on micro gravity environment from the satellite developers' side.
NASDA has developed a micro satellite named ``μ-LABSAT'' on which University of Tokyo is planning to perform target motion estimation and target tracking experiments together with NASDA, Communication Research Laboratory (CRL) and National Aerospace Laboratory (NAL). The technology important for the mission success is the target release mechanism, which should release the target with a specified relative velocity and direction. Micro gravity and vacuum experiment has been performed to verify the design of this mechanism as well as to determine a certain design parameter. The paper describes this satellite project, the planned on-orbit experiment, outline of the micro-gravity experiment, and the results.
Technical issues for micro-gravity experiments of space robotics and space-used mechanisms are discussed in this article and some examples mainly conducted at Tokyo Institute of Technology are introduced. One example is a micro-gravity flight experiment of the Reconfigurable Brachiating space Robot (RBR) developed at Tokyo Institute of Technology. The RBR model used in the flight has 4 degree-of-freedom and an end-effector. The airplane (MU300) generates micro-gravity environment for about 20 seconds in parabolic flight operation. The other example is a free-fall type micro-gravity experiment of the docking mechanism developed for small mothership-daughtership satellite. The free-fall experiment was conducted by using the facility of Japan Micro Gravity Center ( JAMIC), and a drop capsule generates micro-gravity environment for about 10 seconds. In this article, overviews and brief results of these experiments are reported.
The feasibility study has been investigated to build a small satellite (so called `nano-satellite') which has 3-kg mass
and less than 30-W power, since October in 1998. A 3-axes attitude control experiment of the nano-satellite under micro-gravity field is conducted at in Japan Micro-gravity Center ( JAMIC) in 2001. The small reaction wheel is used as an actuator for the attitude control and is developed by Hokkaido Institute of Technology as one of the important key technologies of the nano-satellite. The 3-axes attitude control by using wireless CCD camera (VHF wave) and image processing was demonstrated under micro-gravity.
For the use of ballistic launches of a small satellite, the development study of a high thrust hybrid rocket motor has been made. To enhance the regression rate of the solid fuel and augment the thrust, the authors employed a new fuel configuration. This new configuration allows mixing and combustion to occur around the stagnation points on solid fuel surfaces. The static firing tests using a LOX/PMMA hybrid motor with a LOX cooling system have proved sufficiently prompt ignition, high thrust level, and stable combustion. Based on the obtained data, a flight performance of a small hybrid rocket for a ballistic test launch was estimated.
High quality of protein crystals is very important to determine the molecular structure of protein by X-ray diffraction analysis. The effect of a magnetic field on the protein crystal growth is quite a new research field. Topics for protein crystallization in magnetic fields are reviewed, including making the low-gravity environment on the earth, the formation of protein crystals in low-gravity, the improvement of crystal quality, the magnetic orientation of protein crystals, damping of natural convection caused by Lorentz force etc. Judging from these researches, magnetic fields are suitable for the protein crystallization.
The effect of melt flow, coming to dendrite tip, is studied analytically on the morphology of needle dendrite during unidirectional growth. The melt flow around the paraboloid body is analyzed under Oseen approximation for Navier-Stokes flow equation. Solutions of diffusion equation for temperature and solute distribution are studied under melt flow. The tip radius of curvature of needle dendrite is predicted by perturbation analysis just before for the growth of secondary arms of the needle. It is shown that the melt flow decreases the tip radius of curvature of dendrite and the effect becomes significant in low growth rate. The predicted radius is compared with experimental one and the correspondence between them is fairly well.
Two experiments for eutectic and peritectic system alloys using the sounding rocket, TR - 1A No. 4 and No. 6, were performed in 1995 and 1997. Both experiments were successful because some problems which occurred during preparation of the experiments were discussed and resolved perfectly. It was clarified that the gravity segregation of eutectic system alloys generates during solidifying process and metallic compounds of TiAl3 in Al-Ti or TiB2 in Al-Ti-B grain refiners added in the aluminum alloys promote to nucleate primary aluminum crystals. All results obtained can apply the solidification processing and the foundry industry.
The Multi-Purpose Furnace (MPF) was developed and launched for micro-gravity experiment used the sounding rocket TR-IA#5, #6 and #7. We describe lessons learned through development of the MPF from a viewpoint of equipment development.