Testing and Evaluation of Ultra-Thin Loop Heat Pipe as Lightweight Flexible Thermal Strap for Spacecraft

Thermal strap with high thermal conductance are required. Usually, thermal strap is made of high thermal conductive materials such as copper, aluminum, and graphite sheet. In order to obtain high thermal conductance, the thickness of the materials is increasing, and, as a result, the weight of the strap is increasing. To avoid this problem, this work proposes to apply an ultrathin loop heat pipe (UTLHP) as a thermal strap because the LHP has characteristics of high effective thermal conductivity more than several thousand W/mK even the thickness of the LHP is below 1mm. The thickness of the UTLHP in this work is only 0.6mm, and can operate even bending condition. The UTLHP is made of six layers of pure copper foils. The wick of the UTLHP is made by etching process. Pure water with the freezing point of 0 ? is used as a working fluid. In order to apply the UTLHP to the spacecraft, following factors should be guaranteed. -The UTLHP can operate with no degradation even after the working fluid has melted. -The UTLHP can operate with no degradation even in a vibrating environment. -The UTLHP can operate without leakage under a vacuum condition. In this paper, following evaluations were conducted for the UTLHP to evaluate a potential of this UTLHP as a thermal strap for spacecraft; -Thermal performance of the UTLHP before and after freezing. -Thermal performance of the UTLHP begore and after vibration testing. -Thermal performance of the UTLHP under the vacuum condition. The details of the experimental results will be presented in the full paper.