Injury Risk Differences Between Male and Female Spacecraft Occupants Under Spaceflight Dynamic Loads: A Computational...

This computational study assessed differences in injury risk between male and female spacecraft occupants under spaceflight dynamic loads. The Global Human Body Models Consortium 50th percentile simplified male (GHBMC M50-OS) and female (GHBMC F50-OS) finite element models were used to simulate 150 pairs of impacts. Each model was postured in three spinal alignments, impact-tested across ten landing loads (4.7-16.1 g peak, 60-100 ms rise time) and five directions ranging from caudo-cephalic (+Gz) to postero-anterior (+Gx) in the sagittal plane. Head, neck, and lumbar injury probabilities were calculated using site-specific injury risk functions. The significance of differences was tested using the Wilcoxon signed-rank test. Insufficient evidence of significant differences was found in head injury risk in two-of-three postures. Head rotational acceleration injury risk was high in both males (median 1.48%) and females (1.22%). Significant differences were observed in neck and lumbar spine injury risks. Female necks showed higher risk (maximum 2.24%) due to compressive loads, while male lumbar spines had greater injury risk (maximum 0.26%) and higher intervertebral stress (0.6-2.95 MPa), especially at the L4-L5 joint. Injury risk was found to vary by load direction and spinal posture. For given conditions and chosen risk metrics, lowest injury risk was observed in models seated in a slouched-back posture experiencing rear-end loads. The development of sex-specific spacesuits and posture-conforming seat systems is recommended to mitigate injury during spaceflight landings.