Takehiko Ishikawa

第27回宇宙利用シンポジウム (2011年1月24日-25日, 宇宙航空研究開発機構宇宙科学研究所相模原キャンパス), 相模原市, 神奈川県 The Twenty-seventh Space Utilization Symposium (January 24-25, 2011. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan Microgravity conditions have advantages of measurement of surface tension and viscosity of metallic liquids by the oscillating drop method with an electromagnetic levitation (EML) device. Recently, it has been identified that dependence of surface tension on oxygen partial pressure (Po2) must be considered for industrial application of surface tension values. Effect of Po2 on surface tension would apparently change viscosity. Therefore, surface tension and viscosity must be measured simultaneously in the same atmospheric conditions. Moreover, effect of the electromagnetic force (EMF) on the surface oscillations must be clarified to obtain the ideal surface oscillation because the EMF works as the external damping force to the oscillating liquid droplets, so extensive EMF makes apparently the viscosity values large. In our working group (WG), using the parabolic flight levitation experimental facilities (PFLEX) the effects of Po2 and external EMF on surface oscillation of levitated liquid droplets are systematically investigated for the precise measurements of surface tension and viscosity of high temperature liquids. In this year we performed the observation of surface oscillations of levitated liquid Si-Ge alloys using PFLEX on board flight experiments by G-II operated by DAS. The density of liquid Si-Ge was measured by using electromagnetic levitation with a static magnetic field. In these experiments, we obtained the density, the viscosity and the surface tension values. From these measurements, we discussed surface segregation in systems forming intermetallic compounds. The composition dependence of surface tension was expressed by a modified ideal solution model. On the basis of activity of our working group and European WG, we have been preparing the research of thermophysical properties measurement of high-temperature liquids under microgravity conditions in ISS from 2011-2012. 著者人数: 18人 形態: カラー図版あり Number of authors: 18 Physical characteristics: Original contains color illustrations 資料番号: AA0065129024

第27回宇宙利用シンポジウム (2011年1月24日-25日, 宇宙航空研究開発機構宇宙科学研究所相模原キャンパス), 相模原市, 神奈川県 The Twenty-seventh Space Utilization Symposium (January 24-25, 2011. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan Diffusion Phenomena Research Working Group (DPR-WG) was established for the development of strategic plan toward the implementation of microgravity diffusion experiments. We report the activity of our working group in FY 2010. 形態: カラー図版あり Physical characteristics: Original contains color illustrations 資料番号: AA0065129028

第26回宇宙利用シンポジウム(2010年1月25日-26日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス) The Twenty-sixth Space Utilization Symposium (January 25-26, 2010: ISAS/JAXA Sagamihara, Japan) This working group has been established to get fruitful results using an electrostatic levitation furnace (ELF) in the International Space Station. The targets of our group are: (1) expand research area which utilizes ESL, (2) improve techniques of levitation and diagnostics, and (3) identify the necessity of microgravity. Activities of this fiscal year are briefly described in this report. 形態: カラー図版あり 共催: 日本学術会議 著者人数: 15人 Physical characteristics: Original contains color illustrations joint hosting: The Science Council of Japan 資料番号: AA0064730037

第26回宇宙利用シンポジウム(2010年1月25日-26日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス) The Twenty-sixth Space Utilization Symposium (January 25-26, 2010: ISAS/JAXA Sagamihara, Japan) Microgravity conditions have advantages of measurement of surface tension and viscosity of metallic liquids by the oscillating drop method with an electromagnetic levitation (EML) device. Recently, it has been identified that dependence of surface tension on oxygen partial pressure (Psub o2) must be considered for industrial application of surface tension values. Effect of Po2 on surface tension would apparently change viscosity. Therefore, surface tension and viscosity must be measured simultaneously in the same atmospheric conditions. Moreover, effect of the electromagnetic force (EMF) on the surface oscillations must be clarified to obtain the ideal surface oscillation because the EMF works as the external damping force to the oscillating liquid droplets, so extensive EMF makes apparently the viscosity values large. In our working group (WG), using the parabolic flight levitation experimental facilities (PFLEX) the effects of Po2 and external EMF on surface oscillation of levitated liquid droplets are systematically investigated for the precise measurements of surface tension and viscosity of high temperature liquids. In this year we performed the observation of surface oscillations of levitated liquid Si-Cu alloys using PFLEX on board flight experiments by G-II operated by DAS. These observations were performed under the controlled Po2 conditions. In these experiments, we obtained the density, the viscosity and the surface tension values. From these measurements, we discussed surface segregation in systems forming intermetallic compounds. We found the effect of clusters in both density and surface tension experimental data. The composition dependence of surface tension was expressed by a modified ideal solution model. On the basis of activity of our working group and European WG, we proposed the research of thermophysical properties measurement of high-temperature liquids under microgravity conditions to ESA/JAXA-AO as ISS utilization program. 形態: カラー図版あり 共催: 日本学術会議 著者人数: 18人 Physical characteristics: Original contains color illustrations joint hosting: The Science Council of Japan 資料番号: AA0064730036

Electrostatic levitators use strong electric fields to levitate and accurately position a sample against gravity. In this study, the effects of the electric field are investigated with regards to viscosity measurements conducted with the oscillating drop method. The effects of the external field on viscosity measurements are experimentally confirmed by changing the sample size. Moreover, a numerical simulation based on a simple mass-spring-damper system can reproduce the experimentally observed effects. Based on the above results, measurement procedures were improved. These help to minimize the effect of the positioning force and increase the accuracy of the viscosity measurements.

第25回宇宙利用シンポジウム(2009年1月14日-15日, 宇宙航空研究開発機構宇宙科学研究本部相模原キャンパス) The Twenty-fifth Space Utilization Symposium (January 14-15, 2009: ISAS/JAXA Sagamihara, Japan) Microgravity conditions have advantages of measurement of surface tension and viscosity of metallic liquids by the oscillating drop method with an electromagnetic levitation (EML) device. Recently, it has been identified that dependence of surface tension on oxygen partial pressure (Po(sub 2)) must be considered for industrial application of surface tension values. Effect of Po(sub 2) on surface tension would apparently change viscosity. Therefore, surface tension and viscosity must be measured simultaneously in the same atmospheric conditions. Moreover, effect of the electromagnetic force (EMF) on the surface oscillations must be clarified to obtain the ideal surface oscillation because the EMF works as the external damping force to the oscillating liquid droplets, so extensive EMF makes apparently the viscosity values large. In our working group (WG), using the parabolic flight levitation experimental facilities (PFLEX) the effects of Po(sub 2) and external EMF on surface oscillation of levitated liquid droplets are systematically investigated for the precise measurements of surface tension and viscosity of high temperature liquids. In this year we performed the observation of surface oscillations of levitated liquid Cu and Ag using PFLEX on board flight experiments by G-II operated by DAS. These observations were performed under the controlled Po(sub 2) conditions. In these experiments, we obtained the density, the viscosity and the surface tension values as same as reported data, and also obtained the difference of surface oscillations with the change of the Po(sub 2). On the basis of present experimental results, we discussed with European WG member in ESA-ESTEC at this December about the effect of Po(sub 2) on the surface of high-temperature liquids. We agreed to make a proposal of measurement of thermophysical prosperities of high-temperature liquid in controlled Po(sub 2) conditions for next ESA/JAXA-AO. 形態: カラー図版あり 資料番号: AA0064297083

A novel method for micro-gravity experiments using high altitude balloon is now under development in JAXA. The notable feature of this system is its double-shell structure. Dropped from the high altitude balloon, the inner shell falls freely for 30 to 60 seconds because the outer shell is controlled not to collide with the inner shell. Sixteen number of cold gas thrusters are installed on the vehicle to control not only its falling attitude but also spacing between the inner shell and the outer shell. This paper presents design strategy and verifi cation test results of the 50 N cold gas thrusters developed for this micro gravity experimental system. The preliminary results of the fl ight test are also presented to show its feasibility.

Thermophysical properties of several rare earth elements have been measured using electrostatic levitation techniques. The understanding of the nature and behavior of rare earth metals in their liquid phases requires accurate values of their physical properties. However, keeping the samples in their liquid phases free from contamination long enough to carry out measurements represents a formidable challenge. This is due to the high reactivity and contamination of these elements with a crucible or with a gaseous environment. The use of an electrostatic levitator in vacuum circumvents these difficulties and permits the measurements of the density, the surface tension, and the viscosity of these metals above and below their melting temperature. In this paper, the measurement methods as well as the levitation apparatus are introduced and the measured values are reported.