Honeycomb-patterned porous polymer films can be prepared by casting a mixed solution of hydrophobic and amphiphilic polymers on a solid substrate utilizing the condensed water droplet arrays as templates. Due to the temperature non-uniformity of the solution surface resulting from the thermal convections, water condenses heterogeneously. The heterogeneous condensation of water droplets induces the formation of irregular-arrangement of domains in the ordered structure of microporous films. In order to evaluate the effect of gravity on the formation of honeycomb-patterned films, we have made microgravity experiments. Even under microgravity, we successfully prepared honeycomb-patterned films. And interestingly, some samples have multi-layered uniform microporous structures, which are formed with vanishing the relative density effect of solvent and water droplets. It is suggested that the microgravity affects the formation of honeycombpatterned films considerably.
In order to establish technology for precise measurement of surface tension of molten metals under microgravity condition during the parabolic flight of an airplane, copper was selected as the sample from the viewpoints of its oxidization tendency, oxygen partial pressure dependence of surface tension of the molten sample, and ease of heating with electromagnetic levitation. The non-combustibility of the Ar3vol. %H2 gas that can reduce the oxygen partial pressure of the measurement atmosphere was experimentally confirmed as stipulated in the civil aeronautics law in order to employ it in the parabolic flight experiment. The surface tension of molten copper was successfully measured under the reducing gas atmosphere in microgravity during a parabolic flight experiment for the first time.
Microgravity and normalgravity experiments were conducted in which a low-speed liquid jet issued from a circular hole. In order to eliminate the effects of the velocity distribution formed by a finite-length nozzle, a thin orifice plate was adopted. In addition to the evaluation of the nondimensional breakup length, the nondimensional wavelength of the unstable wave causing the breakup was estimated through the results of the image analysis. Under microgravity condition, the dominant breakup mode was smoothly changed from the short-wave mode to the long-wave mode as the issue speed increased. On the other hand, under normalgravity condition, due to gravitational acceleration of the baseline liquid jet, the jump in the nondimensional breakup length was observed around the transition of the dominant breakup modes. Gravitational acceleration also affected the behaviors of the unstable waves. In the case where the effect of gravity was large, the nondimensional wavelength was much larger than the value of the unstable wave with the largest amplification
rate. In such cases, the capillary waves propagating upward from the liquid jet tip was converted into the unstable waves before reaching the orifice exit. In other words, the gravity itself can make the unstable waves. The continuous extension of the nondimensional wavelength of the unstable wave led to the larger breakup length under normalgravity condition.
The microgravity-induced deterioration of skeletal muscle properties is one of the health problems, which are the serious medical concerns for the manned long-duration spaceflight mission. Responses of the activities of electromyogram (EMG) in hindlimb muscles and afferent and efferent neurograms at the L5 segmental level of spinal cord in conscious rats to altered levels of gravity were studied using parabolic flight of jet airplane. In soleus, EMG was increased in response to elevation of G during the ascending phase, but was eliminated in
microgravity (μ-G) environment. Similar response of the level of afferent, not efferent, neurogram was also noted. These phenomena were related to the shortening of muscle due to plantarflexion of ankle joints. As for adductor longus, region-specific responses were observed. The EMG activity in the caudal, not rostral, region decreased and activity patterns were changed from tonic to phasic during μ-G exposure. These phenomena were related to shortening of fibers, caused by abduction of hip joints and extension toward backward. These results clearly indicated that unloading-related undesirable adaptation of antigravity muscles is closely related to inhibition of mechanical and/or neural activities.
The essential role of microgravity experiments for understanding solid material flammability is discussed based on the mechanism to determine limiting oxygen concentration to sustain spreading flame over solid material. Then some examples of significant extension of flammability limit of solid material in microgravity are introduced, which are given by short-term microgravity facilities. The limitation of short-term microgravity tests and necessity of long-term microgravity experiments are also described according to the example of large time scale unsteady phenomena included in the combustion process. At the last part of the present report, ongoing research project including ISS/KIBO experiments to build up a new fire safety standard is introduced.
We clarify the aerosol dynamics during thin film formation by using the aerosol deposition (AD) technique under the microgravity conditions. Akedo et al. (1999) showed that AD technique is useful for making thin film of ceramics materials. Using AD technique, we have been trying to make thin film of thermally unstable materials, such as clathrate compounds and/or amorphous materials. However, it is difficult to make homogeneously the aerosol of these materials, because in the terrestrial conditions the fine particles of these materials are settled down below the chamber during making its aerosol. Thus, in the microgravity conditions, we hope to make homogeneously aerosol for good quality of thin film by AD technique. In order to make homogeneous aerosol under microgravity conditions, we developed AD system under microgravity conditions during parabolic flight by MU-300 airplane. Using the system, we succeeded to make thin films of (Pb(Ti,Zr)O3) (PZT) with very smooth surface morphology by the AD technique under microgravity conditions. We also observed aerosol (He gas and PZT fine powders) dynamics during thin films deposition by flow visualization with light scattering technique. From these observations, we conclude that it is possible to make homogeneous aerosol under microgravity. Therefore, if we perform constant microgravity conditions such as in the international space station (ISS) we will be able to high quality films with very smooth surface morphology and with very high hardness.