Data from the Hybrid III and THOR (Test Device for Human Occupant Restraint), anthropomorphic test devices (ATD) currently available to test the Occupant Protection requirements, are not well correlated to low-injury risk, as these ATDs were designed for automotive use. Automotive research is directed at preventing severe injuries in very low probability events. NASA vehicles require a lower risk of injury because the vehicles will land every time, making that a high probability event. The objective of this study is to develop injury risk functions for the Hybrid III and THOR ATDs. Matched pair tests between postmortem human surrogates (PMHS) and each ATD will be used to determine ATD-specific injury criteria. The merit of the matched pair design is the one-to-one correspondence of the results from external loads to both surrogates. Injury outcomes from PMHS tests will be used with region-specific data, such as forces and moments either individually or in combination, to derive ATD-specific injury criteria.
1. Identify appropriate datasets for ATD comparison
2. Test Hybrid III 50th percentile male and THOR in same conditions as historical testing
3. Use historical human data to establish tolerance and injury risk focusing on lower neck injury, lateral responses, and sex differences
4. Perform survival analysis with human tolerance to estimate injury risk and use results of prior data mining and existing literature as prior distribution
5. Develop new Injury Assessment Reference Values (IARVs) based on the new statistical analysis.
For each phase of this study, historical PMHS test cases were first selected from the Medical College of Wisconsin (MCW) database for matched-pair testing. Selection of these cases was made based on their similarity to spaceflight loading dynamics and astronaut demographics. Once these data were selected, the Hybrid III 50th percentile male and THOR ATD are tested in identical conditions. The following injury criteria were evaluated:
1. Lower neck injury in rearward loading
2. Vertical neck loading
3. Upper and lower neck under lateral loading
4. Thorax in lateral loading
5. Pelvis in lateral loading
A survival analysis was used to relate the resulting dynamic responses to identified PMHS injuries and develop injury risk correlation. This correlation was used to improve upon the injury metrics previously developed under the Occupant Protection (OP) Data Mining and Modeling Task. The resulting metrics will be used to update NASA standards and provided to the Orion and Commercial Crew programs to allow additional insight into verification, validation, and risk analysis.