Qualification of High Temperature Platings and Corresponding Lessons Learned

Abstract

BepiColombo is an ESA cornerstone mission for the exploration of the Mercury planet. The journey to Mercury is a 6 year long cruise that constitutes a challenge for the materials used because of the long exposure to the high intensity of Sun illumination.

Several metallic and organic materials will reach sustained high temperatures and undergo phenomena such as stress relaxation/creep, and degradation of thermal and mechanical properties. These aspects need to be considered upfront during material selection and evaluation. A specific logic has been for this, which considers the incremental detailed knowledge of the environment, the material use and the spacecraft configuration.

A number of high-temperature platings of titanium alloy substrate have been subject to development, namely the gold-plating of the Medium and High Gain Antenna Rotary Joints, and the silver-plating of the Low Gain Antenna. Their qualification testing has shown how process set up is crucial, to avoid plating degradation during thermal cycling at extreme temperatures. A number of lessons have been learned for the improvement of the processes used.