To improve our understanding of Soyuz crewmember injury risk, as well as future crewmembers onboard the three new designs (Orion, SpaceX Dragon2, and Boeing CST-100), we propose a computational study whose key objectives are to assess the risk of injury to Soyuz crewmembers and compare the Soyuz occupant protection design to the three future vehicle designs. Using mid-size male finite element (FE) models of a human with varying levels of complexity, Soyuz landings will be simulated and responses from the model will be analyzed to assess injury risk. These injury risk predictions will be correlated with actual injury outcomes in crewmembers captured in the Human Research Program (HRP)-funded Soyuz Landing Injury Risk Characterization Study (Principal Investigator: Newby). Soyuz human FE injury risk predictions will also be compared to our previous human FE simulations of the three modern vehicle designs from the HRP-funded ATD (Anthropomorphic Test Dummy) Injury Metric Sensitivity and Extensibility Study (Principal Investigator: Somers; Co-Investigators: Stitzel, Gayzik, Weaver, Newby). This will greatly aid NASA to estimate crew injury risk as a design variable for future missions.

By assessing Soyuz landing impacts with a human FE model in flight-like conditions and comparing the Soyuz occupant protection design to other modern vehicle designs, this proposal directly addresses the Human Research Roadmap (HRR) Risk of Injury Due to Dynamic Loads and would provide additional evidence to characterize the risk as well as contribute to addressing three Occupant Protection gaps (OP-101: We do not understand the risk of injury associated with crewed vehicle landings and how this risk relates to the desired acceptable risk; OP-301: We do not have an identified, validated and standardized approach for vehicle instrumentation and biodynamic data collection, and predictive analytic biodynamic modeling that would allow for specific risk injury prediction by mission-phase, crew functionality post-landing, and vehicle design; and OP-401: We do not know the extent to which multiple spaceflight hazards (e.g., spaceflight deconditioning, bone loss, radiation exposure, altered gravity) may interact to synergistically decrease injury tolerance for off-nominal dynamic landing loads, increasing risk to crew’s performance in mission-completing actions immediately after landing.). The project will yield novel scientific knowledge on crewmember injury risk associated with landing events in the Soyuz, Orion, Dragon2, and CTS-100 vehicles. The work will also produce validated analytical tools including a Soyuz seat FE model with mid-size male human body FE models which can be used to verify occupant safety of crewmembers in impact conditions. By achieving the aims of the proposed work, the study will advance our overall understanding of crewmember injury risk due to dynamic loads encountered in spacecraft landings, and produce validated computational models which can be used to predict the associated occupant injury risk when the Soyuz and modern spacecraft vehicle designs are subjected to various dynamic loading events.

Ultimately, the goal of this project was to generate data that will help answer the question: “Why was the rate of injury in the Soyuz vehicle higher than expected?”. The study consisted of two specific aims: (1) Identify expected injury risks associated with nominal and off-nominal landing scenarios in the Soyuz, and quantify differences in injury risk predicted by human body models (HBMs) of varying complexity. (2) Examine differences in injury risk to crews of Soyuz and modern vehicles as it relates to seat and restraint design and loading combinations.

In conclusion, this study developed a finite element model of the Soyuz seat that is usable for future studies. The detailed and simplified Global Human Body Models Consortium (GHBMC) human body models were compared in a limited set of Soyuz landing cases. Little difference was observed for the two models across the full body, with exceptions for head rotational velocity, chest compression, and lumbar moments. Therefore, unless a future study is focused specifically in those regions, the benefits of the significantly faster run-time of the simplified GHBMC can be taken advantage of. It was demonstrated that the lack of a side head guard in the Soyuz produced higher neck tension values, which may explain the increased presence of whiplash-like injuries in the real-world landings. However, the elevated lumbar spine injury rate was unexplained. Therefore, the authors believe that many of the elevated injury occurrences in the Soyuz landings may be attributable to higher impact kinematics than expected. Future work should be focused on reconstructing these landings, and take advantage of the newly developed FE model of the Soyuz seat. As the modern vehicles continue to be used in American spaceflight, instrumentation should be included in the capsules so that landings are documented in real time. If an injury occurs, the impact should be simulated with an appropriately scaled HBM and seat to understand the mechanism of injury. If an obvious design change is clear, and doesn’t affect operation, that change can potentially be made to protect future occupants.

To improve our understanding of Soyuz crewmember injury risk, as well as future crewmembers onboard the three new designs (Orion, SpaceX Dragon2, and Boeing CST-100), we propose a computational study whose key objectives are to assess the risk of injury to Soyuz crewmembers and compare the Soyuz occupant protection design to the three future vehicle designs. Using mid-size male finite element (FE) models of a human with varying levels of complexity, Soyuz landings will be simulated and responses from the model will be analyzed to assess injury risk. These injury risk predictions will be correlated with actual injury outcomes in crewmembers captured in the Human Research Program (HRP)-funded Soyuz Landing Injury Risk Characterization Study (Principal Investigator: Newby). Soyuz human FE injury risk predictions will also be compared to our previous human FE simulations of the three modern vehicle designs from the HRP-funded ATD (Anthropomorphic Test Dummy) Injury Metric Sensitivity and Extensibility Study (Principal Investigator: Somers; Co-Investigators: Stitzel, Gayzik, Weaver, Newby). This will greatly aid NASA to estimate crew injury risk as a design variable for future missions.

By assessing Soyuz landing impacts with a human FE model in flight-like conditions and comparing the Soyuz occupant protection design to other modern vehicle designs, this proposal directly addresses the Human Research Roadmap (HRR) Risk of Injury Due to Dynamic Loads and would provide additional evidence to characterize the risk as well as contribute to addressing three Occupant Protection gaps (OP-101: We do not understand the risk of injury associated with crewed vehicle landings and how this risk relates to the desired acceptable risk; OP-301: We do not have an identified, validated and standardized approach for vehicle instrumentation and biodynamic data collection, and predictive analytic biodynamic modeling that would allow for specific risk injury prediction by mission-phase, crew functionality post-landing, and vehicle design; and OP-401: We do not know the extent to which multiple spaceflight hazards (e.g., spaceflight deconditioning, bone loss, radiation exposure, altered gravity) may interact to synergistically decrease injury tolerance for off-nominal dynamic landing loads, increasing risk to crew’s performance in mission-completing actions immediately after landing.). The project will yield novel scientific knowledge on crewmember injury risk associated with landing events in the Soyuz, Orion, Dragon2, and CTS-100 vehicles. The work will also produce validated analytical tools including a Soyuz seat FE model with mid-size male human body FE models which can be used to verify occupant safety of crewmembers in impact conditions. By achieving the aims of the proposed work, the study will advance our overall understanding of crewmember injury risk due to dynamic loads encountered in spacecraft landings, and produce validated computational models which can be used to predict the associated occupant injury risk when the Soyuz and modern spacecraft vehicle designs are subjected to various dynamic loading events.