Lessons learned about fabrication of space solar arrays from thermal cycle failures

Abstract

Lessons have been learned about the fabrication of space solar arrays manufactured at different facilities from thermal cycle failures. One solar array facility had a design with aluminum facesheets that had a significant number of solar cell strings which had open-circuited failures during early on-orbit thermal cycling due to improper cell rework involving both coverglass adhesive encapsulation of interconnect stress relief areas and cell adhesive contamination of interconnect n-bar solder joints. Another solar array facility had a solar array with 8% of the replaced solar cells blowing out with an outward force during acceptance level thermal vacuum cycle testing due to inadequate cell replacement processes. A solar array design with anodized aluminum backside facesheets was found to have anodize flaking off after being subjected to thermal cycling, which significantly lowered the emissivity of the array's back surface. The cause of the thermal cycle failures, analysis and test results, and corrective action to prevent future thermal cycle failures are presented.