Development and evaluation of a finite element model of the THOR for occupant protection of spaceflight crewmembers.

New vehicles are currently being developed to transport humans to space. During the landing phases, crewmembers may be exposed to spinal and frontal loading. To reduce the risk of injuries during these common impact scenarios, the National Aeronautics and Space Administration (NASA) is developing new safety standards for spaceflight. The Test Device for Human Occupant Restraint (THOR) advanced multi-directional anthropomorphic test device (ATD), with the National Highway Traffic Safety Administration modification kit, has been chosen to evaluate occupant spacecraft safety because of its improved biofidelity. NASA tested the THOR ATD at Wright-Patterson Air Force Base (WPAFB) in various impact configurations, including frontal and spinal loading. A computational finite element model (FEM) of the THOR to match these latest modifications was developed in LS-DYNA software. The main goal of this study was to calibrate and validate the THOR FEM for use in future spacecraft safety studies. An optimization-based method was developed to calibrate the material models of the lumbar joints and pelvic flesh. Compression test data were used to calibrate the quasi-static material properties of the pelvic flesh, while whole body THOR ATD kinematic and kinetic responses under spinal and frontal loading conditions were used for dynamic calibration. The performance of the calibrated THOR FEM was evaluated by simulating separate THOR ATD tests with different crash pulses along both spinal and frontal directions. The model response was compared with test data by calculating its correlation score using the CORrelation and Analysis rating system. The biofidelity of the THOR FEM was then evaluated against tests recorded on human volunteers under 3 different frontal and spinal impact pulses. The calibrated THOR FEM responded with high similarity to the THOR ATD in all validation tests. The THOR FEM showed good biofidelity relative to human-volunteer data under spinal loading, but limited biofidelity under frontal loading. This may suggest a need for further improvements in both the THOR ATD and FEM. Overall, results presented in this study provide confidence in the THOR FEM for use in predicting THOR ATD responses for conditions, such as those observed in spacecraft landing, and for use in evaluating THOR ATD biofidelity.