Impact-induced failures of solar array cable bundles

Solar arrays are the spacecraft component that expose the largest surface to the orbit environment. Previous work has shown that effects of micrometeoroid and space debris impacts on the photovoltaic network are effectively mitigated through common measures of redundancy and discharge prevention. The experiments conducted in this work show that the highest risk for impact-induced power degradations is posed by impacts on the power transfer harness on solar array rear side. Permanent short circuits are caused by severing powerlines of opposed polarity. These come in contact through the impact generated plasma and, more importantly, by their direct mechanical contact. Projectiles as small as 1.27 mm at >7 km/s led to a permanent loss of a cable bundle carrying the power output of whole solar array section. The ballistic limit criteria are assessed to be ≥ 0.8 mm for unprotected external harness, but more tests are needed to reliably quantify the threshold conditions and evaluate the effectiveness of protective measures with minimal system impact like added multi-layer shielding.