Direct Measurements of Lightning-Induced Coupling to a Spacecraft Umbilical Cable

Inhalt:
Lightning-induced currents and voltages were directly measured on a legacy spacecraft umbilical cable installed at the Kennedy Space Center in Florida. Measurements were recorded for 88 return strokes that terminated within 3km of the umbilical instrumentation during 2022 and 2023. Overall umbilical current, inner shield current, and inner twistedshielded pair (TSP) conductor current were simultaneously measured in addition to TSP pin voltages. The umbilical current peaks were found to be well correlated with the current peaks of the S12 inner shield, while the peaks of the umbilical current derivative and the S12 inner shield current derivative were found to be strongly correlated with the TSP voltage peaks. Finally, the S12 inner shield current peaks were found to be strongly correlated with the short-circuit current on the TSP conductor. Correlations were established via simple second order polynomial or linear functions. Simultaneous current measurements demonstrated the effectiveness of multi-layer shielding toplogies where the current amplitude and risetime were reduced from overall umbilical current, to S12 inner shield current, to TSP conductor current.