We carried out a microgravity experiment of thermomagnetic convection induced in a double cylinder, the aspect ratios of which were 0.44 and 0.53. The dissipative patterns formed in the cylinder were investigated by measuring temperatures with 20 thermocouples set in the cir­cumferential direction along the outer cylinder. 8 and 10 rolls were formed for A= 0.44 and 0.53, respectively. We also investigated the pattern formations by the linear stability theory. The result of the calculation agreed with the experimental result.

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Laser induced fluorescence method has been employed for the remote, non-intrusive and instantaneous measurements of the temperature of a fuel droplet burning under microgravity. A fuel droplet doped with naphthalene and TMPD was allowed to burn in a quiescent gaseous environments. The fluorescence emission spectra from a droplet subjected to the nitrogen laser excitation were measured with an image intensified optical multichannel analyzer . All the measurements were done under microgravity generated in a capsule of the MGLAB drop shaft. The results showed that a newly developed diagnostic system was found to be applicable successfully for the non-intrusive droplet thermometry under microgravity. The ratio of fluorescence emission intensities at two different wavelengths was an appropriate criterion for the in-situ determination of droplet temperature. The black radiation from the soot in the flame caused no serious trouble in the thermometry .

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The Space Flyer Unit (SFU) is an unmanned free flyer flown in orbit from March 18, 1995 to January 20, 1996. Space environments such as microgravity and surrounding atmospheric condi­tions were monitored and are reviewed as reference for future missions. Engineering impacts of microgravity on spacecraft are also reviewed including post flight analyses.

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The Space Flyer Unit (SFU) was launched by the H-II rocket on March 18, 1995 and retrieved by the space shuttle on January 13, 1996 after six months space experiment. The compound semiconductor crystal growth experiments using the microgravity environments in space were executed and all experiments were completely carried out as planned and the experimental operation ended successfully. The evaluation of these specimens comfirmed that the space processed specimens are accompanied by various phenomena with respect to crystal growth mechanism, compositional homogeneity, uniformity of the layer thickness and reduction of crystal line defects, which are likely to have occurred in the presence of microgravity and convection-free conditions. This paper presents summary of results of compound semiconductor crystal growth experiments in the SFU.

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CdTe crystals doped with Zn were grown in Space Flyer Unit (SFU) by the process essentially based on the Bridgman technique. The growth apparatus was intended to realize the contactless growth of melt with growth ampule under microgravity environments. The sample, which has been grown in contact with the growth ampule during its liquid phase, contained many twin lamellae like usual CdTe grown on the ground. While, the sample which has been grown out of contact with the growth ampule during its liquid phase was single-crystalline (twin-free). This contrast suggests that the contact of melt with growth ampule is essential to cause twin lamellae in Cd Te. The single crystal is characterized by etch pit density (EPD) count, X-ray topography, photoluminescence (PL) and electron prove micro analyser (EPMA). The results show that the growth interface has changed from convex to concave along with growth direction. In accordance with the shape of growth interface, EPD increases from 2 x 104 cm- 2 to 2 X 105 cm- 2. The estimated value of the effective segregation coefficient for Zn is less than reported value because of the suppression of thermal convection in microgravity. Additionally, analysis of the crystal shape reveals that receding contact angle is close to 0 and solid-to-liquid density ratio is about 1.1 for CdTe.

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A vapor phase epitaxy of InGaP single crystal on GaP in a closed ampule using chemical vapor deposition (CVD) has been studied under microgravity (µ-g) in a gradient heating furnace (GHF) loaded in space flyer unit (SFU). The targets of the flight experiments are (i) to improve uniformity of the crystal, and (ii) to obtain new knowledge about the gas transport and crystal growth mechanism. The crystals grown under µ-g were demonstrated to have an excellent uniformity of the layer thickness and matrix element content by suppression of the convection. It has also been proved that under microgravity the tranport rate follows simple diffusion theory even in the vapor phase growth with chemical reactions.

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The effects of microgravity on the growth processes of colloidal crystals were evaluated using TR-IA sounding rocket. The merit of studying colloidal crystals lies in the in-situ observation of growth dynamics with visible light. Using reflection spectrum method, expansion of interparticle distances under microgravity was confirmed compared with those of normal-gravity experiments. The growth mechanism of colloidal crystals under microgravity was explained as a diffusion-controlled processe, whereas normal-gravity experiments showed an Ostwald-ripening mechanism. The difference of the growth mechanisms between microgravity and normal-gravity is discussed based on the absence of gravitational sedimentation.

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To clarify the heat transfer mechanisms in microgravity nucleate boling, the experiment was conducted by the use of NASDA TR-IA No. 5 rocket. Detailed heat transfer data and values of liquid film thickness underneath a growing bubble on the surface were otained from a transparent heating surface on which electorodes of the sensors are coated directly. The degree of subcooling of ethanol as test liquid and the heat flux supplied were varied in the wide range under the constant liquid temperature. The following was obtained. i) In the coalesced bubble region, the heat transfer is dominated by the behavior of microlayers underneath primary bubbles which are just generated at the base of the coalesced one. ii) Marked heat transfer enhancement is observed at moderate heat flux under the saturated liquid condition, but it changes easily to the deterioration when the dry patches are extended in the microlayers of enlarged area. iii) In the subcooled boiling, the steady bubble behavior and heat transfer are possible in microgravity by the balance of evaporating and consensing rates. iv) In saturated boiling, the reduction of heat flux supplied results in the deactivation of nucleation site in the liquid film underneath a large coalesced bubble contacting to the heating surface.

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Experimental study on formation of a homogeneous spray and its ignition and combustion were carried out by using microgravity conditions produced by the fifth TR-IA rocket. Condensation method was applied to generate homogeneous sprays. Methanol and air were used as a fuel and ambient gas, respectively. Shadowgraphy, shearing interferometry and PIV were employed to observe behaviors of a flame and droplets. Experiments were performed three times in 6 minutes microgravity conditions. Since enough amount of fuel to make a saturated fuel vapor-air mixture was not charged into a combustion chamber, no spray was generated. However, it was observed that a flame kernel grew spherically up to about 14 mm diameter in very lean premixtures. Temporal variations of the temperature profile of a flame kernel were measured with the shearing interferometer. These detailed data on ignition of lean premixtures have never been obtained under normal gravity conditions.

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The experiment of capillary gap penetration of molten Ag-Cu-Li alloy into gaps of stainless steel sleeves under microgravity using a parabolic flight of the sounding rocket, TR-IA-5 by NASDA, was carried out in the last September. The purpose of this experiment was to understand capillary penetration phenomena under microgravity to establish a guideline for the decision of brazing process parameters in space environments. The test results proved that our theoretical prediction method for capillary gap penetration by the theories of thermal conductivity and surface tension was reasonable one.

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This report reviews papers and reports in which microgravity sciences and technologies concern­ing g-jitter are dealt with. The fluctuation of gravitational acceleration, which is called g-jitter, is in­duced by various factors under low-gravity conditions. Although it is already known that residual and time-varying accelerations exist in the space platforms, the effects of g-jitter on material processing under microgravity conditions have not yet been fully understood . In this brief report, I summarise theoretical and experimental analyses concerning material processing and g-jitter.

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