(Invited) The Electrostatic Levitation Furnace Onboard the International Space Station for Container-Less Material Processing and Thermophysical Property Measurements at Extremely High Temperature

Abstract

Electrostatic levitation is one of the container-less processing methods which utilizes Coulomb force between a charged sample and surrounding electrodes. Contrary to the other methods, electrostatic levitation cannot create a potential minimum, so high-speed feedback position control is necessary. Because of this technical difficulty, development of this method was behind to other methods, such as electromagnetic levitation, or acoustic levitation. Samples can be levitated even in ground. However, to levitate samples against gravity, huge electric field and huge surface charge on the sample are required. This creates some limitations in ground experiments. Firstly, Oxides samples are hard to levitate due to low surface charge. Secondly, experiment in inert gas environment is impossible to prevent electric discharge among electrodes. These limitations can be easily solved in microgravity. Oxides sample cane be levitated and melted. Metals and alloys can be processed in inert gas to suppress evaporation.The electrostatic levitation furnace on the International Space Station (ISS-ELF) developed by Japan Aerospace Exploration Agency, was launched to the ISS in 2015. Then, Installation to the MSPR (multi-purpose Small Payload Rack) was conducted in the next year. Since then, a variety of oxide/ metal samples have been levitated and melted in the facility. The ISS-ELF has a capability to measure thermophysical property of extremely high temperature melts. Density, Surface tension, and viscosity can be measured by this facility. Status of thermophysical property measurements is described in this presentation.