We review the containerless-levitation techniques for thermophysical property measurements of high-temperature liquids. Particularly, we describe details of recent research using the techniques under microgravity in International Space Station (ISS). Thermophysical properties of high-temperature liquids are needs for industrial process control design of high temperature material processes by the numerical simulations. Therefore, their temperature dependence is necessary. For the requirements, their measurements should be in high temperature regions. In high temperature regions, the containerless levitation under microgravity has advantage for thermophysical properties measurements of liquid samples. In this article, we focus on the containerless levitation techniques in ISS for thermophysical properties measurements of high temperature alloy’s liquids, and also the interfacial tension between iron melt and molten oxide.
Because mitigation, sampling, and utilization technologies of regolith are critically important for lunar, Mars, and asteroid explorations, we are conducting the following research and development; (1) electrostatic cleaning of dust on optical elements, (2) electrostatic and magnetic cleaners for dust adhering to spacesuits, (3) electrostatic shield for dust entering into mechanical seals of equipment, (4) transport of regolith based on electrostatic traveling-wave and me-chanical vibration, (5) electrostatic particle-size classification, (6) electrostatic and magnetic sampling of regolith, (7) electrostatic precipitation in the Martian environment, and (8) electrostatic manipulation of a small particle.
More than 100 spacecrafts have attempted to softly land on the surface of planet such as a moon, Mars, Venus, a comet and an asteroid in the history of space development. Although the landing success rate is approximately 40 percent, there are few failures caused by unexpected environmental influences and large deviations from the supposed environmental conditions. It is considered that this is due to conducting adequate investigation of environment around the exploration area by remote sensing and steadily progressing the mission while obtained Lessons Learned through a series of project. For this article, we first discuss about the space environment in which the planetary explorer works. Then, we outline how we verify and evaluate the specifications of components and system of the spacecraft with the tests partially simulating harsh environments such as heat, radiation and regolith. Furthermore, countermeasures against the harsh environments where the actuator and absolute angle sensor are exposed are also mentioned.
We have developed a magnetic fluid with greatly improved heat resistance as compared with conventional products by optimizing the molecular weight of base oil and surfactant. In addition, it has also excellent corrosion resistance, ultra-low vapor pressure and low outgassing. These excellent properties make it ideal for magnetic fluid seal used under extreme conditions such as in various semiconductor-manufacturing processes with about 10 times longer service life than conventional products.
In Japan, many kinds of underwater robots have been increasingly developed since the Great East Japan Earthquake. The authors have developed underwater robots for marine survey and conservation activities in the waters around Okinawa for over 10 years. We have been conducting verification test on developed equipment and proposed method to increase the safety and efficiency of underwater work. In this paper, Chapter 2 describes the development of an underwater robot that injects acetic acid into crown-thorns-starfish for coral conservation and the development of a towed underwater robot for coral investigation. Chapters 3 and 4 describe underwater archeological survey and educational activities utilizing our surface and underwater robots. In the survey, we created a seafloor 3D map using photogrammetry technology and underwater camera system.
High temperature superconducting (HTS) cable is kept below the material specific critical temperature utilizing sub-cooled liquid nitrogen. Sub-cooled liquid nitrogen to flow in a HTS cable is cooled and circulated by a refrigerator and a pump. The high efficiency refrigerator is important in order to reduce the transmission loss of HTS cable including the power consumption of refrigerator. Then we have developed the high efficiency and reliability refrigerator.We set a goal of developing a refrigerator with a COP of 0.1, a maintenance interval of 30,000 hours and a cooling capacity of 5kW. Our goal was achieved by using the reverse Brayton cycle and turbo-compressor and expander. A year-long performance test had verified that our cooling system of sub-cooled liquid nitrogen using this refrigerator is stable for long operation.