Development of the Passive Thermal Control Design for the 'Kibo' Pressurized Modules

Abstract

After joining the International Space Station (ISS) program in 1980's, JAXA has obtained a wealth of technical knowledge and skills from the development and verification of its first manned space structure named 'Kibo' (translated as 'hope' in Japanese). 'Kibo' has two pressurized modules for inboard experiments called the Pressurized Module (PM) and the Experiment Logistics Module-Pressurized Section (ELM-PS) along with the Exposed Facility for external experiments/observations. Through the early design phase of 'Kibo' to its assembly completion on ISS in July 2009, JAXA was faced with a number of design challenges, but together with the supporting manufacturers, JAXA overcame those challenges with engineering solutions. One of the most challenging was the development and verification of the passive thermal control of the pressurized modules. For example, the PM is one of the largest pressurized elements in ISS, so that JAXA could not conduct a thermal equilibrium test in the space chamber, which was a method commonly used for thermal property verifications of spacecraft. Therefore, JAXA adopted the thermal verification strategy composed of thermal analysis on the PM and verification tests by parts. This paper describes the thermal analysis of the pressurized modules and the thermal tests including the fundamental test conducted at the early design phase and the thermal equilibrium test in the space chamber conducted to verify the flight model of the ELM-PS, whose data was applied for the PM verification since their thermal designs were similar. This paper covers the ELM-PS equilibrium test in detail since it showed the thermal property of the ELM-PS flight model was different from what we had expected. This result lead to the redesign of passive thermal control design for both the ELM-PS and the PM, mainly on their debris shields covering outer surfaces, and re-analysis of the PM thermal model on which the thermal property is unique from the ELM-PS. The cause of the unexpected result on the verification test will be given. The verification test using improved debris shield in the space chamber was conducted, and the validity of the redesign was confirmed. Finally, the paper