A compact dilution refrigerator which can be boarded on the jet plane (MU-300) was constructed for the purpose of studying solid 4He physics under zero gravity. It was demonstrated that the fridge could cool down to 140 mK on the plane and the lowest temperature was not affected by the parabolic flight. We successfully cooled solid 4He down to the same temperature, and were able to perform the observation of the crystal growth of solid 4He under zero gravity. The detailed description of the construction is presented and an interesting melting and growth of c-facet of 4He at 140 mK under zero gravity is reported.
An overview on theoretical works and numerical simulations on dusty plasmas with cylindrical symmetry is presented. The main purpose of these works has been to investigate strongly coupled dusty plasmas which are expected to be realized in the planned experiments by PK-4 on the International Space Station and experiments by PK-4J, a similar apparatus constructed here. The distribution of dust particles is analyzed, both analytically and numerically, first on the basis of the drift-diffusion equations as continuum and then numerical simulations have been performed, taking the effect of discreteness into account.
Dusty plasmas have been studied under microgravity with utilities boarding on the International Space Station in a joint Russian/German research project. Dynamics of dust particles in cylindrical plasmas is investigated in the next term of the project with the apparatus of PK-4. A research team in Japan studied the cylindrical dusty plasmas to contribute to the project with the PK-4J similar to the original one and developed for microgravity experiments of parabolic flights in Japan. The dust particles distributed in the off-centered position close to the
bottom in balancing of gravity. They changed the distribution and moved to around the center axis in a cylindrical discharge under microgravity. Several particles arranged in a line parallel to the axis, and the lines piled up to a bundle in the discharge.
Parabolic flight lasting 20–30 s and short-term exposure to microgravity for several weeks have been used to examine changes in the neuromuscular system. Previous studies have shown that short-term exposure to microgravity induces an atrophy of fibers, shifting of fiber type from slow-twitch to fast-twitch with synthesis of new fiber types, decreased oxidative enzyme activity, and down-regulation of the mRNA expression of heat shock proteins in the antigravity skeletal muscles of rats. These changes are similar to those observed after decreased muscular activity and loading levels on Earth. Recent studies using long-term exposure to microgravity for several months have also revealed a decreased oxidative capacity of gamma and alpha motoneurons in the spinal cord of mice, as well as degenerative changes in the skeletal muscles. In this article, we reviewed changes in the neuromuscular system in response to parabolic flight of an airplane and short- and longterm exposures to microgravity on orbit around Earth. We especially focused on the oxidative capacity of spinal motoneurons that innervate muscle fibers.
Short duration microgravity experiments are useful tools for the development of experimental apparatus for microgravity researches. Parabolic flights have been frequently used for the development of the electrostatic levitation furnace (ELF) for the International Space Station (ISS). The history of ELF development and parabolic flight experiments conducted for its development are briefly described in this paper.
The “Group Combustion” experiment is planned as the first combustion experiment in the KIBO on the ISS. Flame spread characteristics of n-decane droplet clouds and linear array will be investigated in detail. The experiment will employ the Multi-purpose Small Payload Rack (MSPR), the Chamber for Combustion Experiment (CCE), and the Group Combustion Experiment Module (GCEM) as experimental apparatus. At present, development of the GCEM has been ongoing in parallel to detail planning of the experiment operation onboard the KIBO. In this paper, overview of the parabolic flights employed for development of the GCEM will be introduced.
Studies on flammability limits are briefly reviewed. Firstly, theory for describing combustion limit of planar propagating flame is introduced. Experimental methods to obtain flammability limits are then reviewed, namely the constant-volume bomb method and the counterflow flame method. Based on various studies, flammable regions of different types of flames were found to vary considerably, depending on the flame configuration, the Lewis number, and flame stretch. Deeper understandings were achieved through microgravity experimental results, such as the Self Extinguishing Flames, C shaped extinction curve and flame balls. Finally, preliminary experimental results to construct an unified flammability-limit theory are introduced. Results are then compared to 2D and 3D computational results showing a qualitative match to the experimental observations.