Step kinetic coefficient of GaP/GaP(111)B surface in liquid phase epitaxy growth was estimated by an in situ observation technique using a near-infrared microscopic interferometer under a reduced convection condition by utilizing a strong static magnetic field. Morphological stability of solid/liquid interface during the growth was evaluated based on a linear perturbational approach taking account of the step kinetic coefficient. The estimated value of the macrostep wavelength agreed well with the measured one.

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Microgravity studies on the dissolution and crystallization of InGaSb were done with a sandwich combination of InSb and GaSb {111} as the starting material using a Chinese recoverable satellite in 1996. The same experiments were performed under normal gravity condition for comparison. The shape of the solid/liquid interface and compositional profiles in the solution were found to be significantly affected by gravity. To study the effect of gravity on the solid/liquid interface and composition profiles, a numerical simulation has been done. Melting and crystallization experiments of InGaSb were done under the reduced gravity condition (10^-2G) in an airplane and at the normal gravity condition (1G) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. However, in the case of the sample prepared at the reduced gravity condition, there was more number of large sized crystals than in the sample prepared under normal gravity. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature.

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Cold spin tests of 3DC/C disk were conducted to elucidate feasibility for the turbine disk of ATREX engine. The fracture speed of the 3DC/C disk was 516 m/s, and this speed satisfied the condition of turbine system in ATREX engine. The fly-out of the fiber-bundles from 3 DC/C disk occurred before the total fracture of the disk and the shaft vibration simultaneously increased. The fly-out behavior was characterized by the delamination of the fiber-bundles from the surface of the 3DC/C disk. The effective preventive methods for fly-out behavior were concluded as to use fine fiber texture and increase inter-bundle bonding strength. Enhancement of the inter-bundle bonding strength by partial Si conversion was shown to be effective to improve the onset speed of fly-out behavior. The machinability of 3DC/Cs for turbine blade was also examined and the tip radius could be machined with 0.5 mm and it remained its shape until 470 m/s.

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New concepts of low-power MPD (Magnetoplasmadynamic) arcjets for high-power applications have been studied in ISAS (Institute of Space and Astronautical Science). There are two categories of these concepts, pulsed-mode and steady-state MPD arcjets. Both are the candidates, because ISAS has several flight experiences of pulsed MPD arcjet, and also R&D experiences of quasi-steady MPD arcjets and low power DC arcjets. This study shows that the cluster of single MPD arcjet will be the reasonable way to realize large-scale high-power MPD arcjet from the viewpoint of ground tests and facility availability. The focal points for such design will be the thermal analysis and electrode erosion for single MPD arcjet that is just a portion clipped out from the cluster configuration. The simple and robust MPD arcjets at high-power evolution will propose a lot of large-scale transportation in the near future.

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A 1kW microwave ion engine system is under development in the Institute of Space and Astronautical Science to meet requirements for an asteroid sample return mission of MUSES-C (Mu Space Engineering Spacecraft) which will be launched by M-V launch vehicle in 2002. An 18,000 hour endurance test for an engineering model was finished in 1999, and prototype models were manufactured to be tested through a series of environment tests for qualification and are undergoing a second time endurance test from 2000. The flight model design was already finalized on the basis of prototype model thrust performances and integration specifications. Now almost all the flight models were combined each other to check out their mutual interfaces as well as bus interfaces. This ion engine system constitutes 4 ion thrusters on a radiation panel with a bi-axially movable gimbal mechanism, 4 microwave supplying units, 3 acceleration power processing units, and 1 propellant management unit. The MUSES-C mission requires the IES to generate thrust of about 24 mN for maximum power input of 1,158 W by 3 of the 4 ion thrusters simultaneous operation.

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