Injury Risk Differences between Male and Female Spacecraft Occupants under Spaceflight Dynamic Loads: a Computational Study

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 (4.7-16.1g peak, 60-100 ms rise time) and five directions ranging from caudo-cephalic (+Gz) to poster-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.