Assessing the In-Orbit Impact of Cell Cracks - An Electroluminescence Study of Crack Propagation

A set of representative miniature solar arrays was built, featuring triple junction cells with a range of typical production defects. The evolution of these cracks throughout several thousand simulated eclipse phases was studied with the help of electroluminescence imaging and pulsed solar simulator measurements. In addition, the effect of sine vibration and acoustic noise was analyzed by monitoring cell cracks on actual flight panels throughout their testing sequences. A power law dependence was found for the number of crack growth events (CGE) per cycle on the number of thermal cycles and the total number of CGE after 2000 cycles showed a linear dependence on crack size. An unexpected crack growth direction, predominantly parallel to the short cell edge, was found. Sine vibration and acoustic noise testing did not result in crack propagation at all. The electrical impact of propagating cracks originated in most cases from the interruption of the cell front side contact network