Gap DL-201: We do not know how load dynamics and sex differences affect injury risk in spaceflight conditions and do not have adequate injury assessment reference values (IARVs) to mitigate the increased risk of injury to the crew.
Last Published:  07/30/21 01:05:31 PM (Central)
Responsible Element: Human Factors and Behavioral Performance (HFBP)
Status: Open

Initial State of Gap: 
The risk of injury due to dynamic loads is well documented for automotive and military environments; however, there is less evidence available to ascertain the risk to crewmembers given the current vehicle design requirements. This knowledge gap will characterize the risk of injury associated with loading dynamics and sex differences.
Spaceflight exposes humans to impact loading in various directions that sometimes differ from loading dynamics found in terrestrial vehicles. These differences include impact duration, loading direction, and probability of occurrence. Impact duration in spaceflight can vary depending on vehicle design and is a stark departure for the durations typically studied in automotive impacts. Loading direction in spaceflight is also typically a multi-axial, complex impact that is unique to a particular vehicle design, which differs from terrestrial vehicles. Because dynamic loads are expected during even nominal spaceflight missions, injury assessment reference values (IARVs) for spaceflight applications must mitigate the total risk of injury to an acceptable level. Currently, appropriate, validated IARVs that address all of these unique aspects of impact loading do not exist. In addition, planetary landing in a non-seated posture violates the underlying assumptions of the current injury prediction tools and requires additional research and development to protect crewmembers in these novel postures.

Concerning sex differences, data collected from male subjects has made up the majority of the datasets used to define IARVs historically. Recently, significant research on sex differences has been reported in the automotive and military literature; however, this work has yet to translate into appropriate IARVs for protecting women. 

Interim stages: 

  • Identify a list of critical injuries for which to protect to limit the scope of the research required
  • Define the scope of dynamic loads reasonably expected in current and future spaceflight systems to limit the scope of the research required
  • Identify the appropriate human surrogate(s) for implementing IARVs appropriate for spaceflight loading conditions
  • Develop IARVs based on the Definition of Acceptable Risk (DAR) as developed in OP-01
  • Validate the IARVs through sub-injurious human testing at nominal landing loads

The NASA Standing Review Panel for the Occupant Protection risk, as well as various external expert panels have identified loading dynamics, sex differences and probability of occurrence as gaps in knowledge. The approach for addressing this gap is based on identifying the appropriate injuries to mitigate, defining the scope of dynamics expected, selecting the appropriate human surrogate(s) to address both the injuries and dynamics, developing appropriate IARVs based on the DAR, and validating the IARVs through sub-injurious human testing. 

Unfortunately, to date, there is not a human surrogate that can predict any injury associated with impact loading in any direction. To limit the scope of the research required, and to adequately address the knowledge gap, identifying the injuries to mitigate and the expected dynamics are necessary. From these base assumptions, a literature review and expert opinion will inform the selection of an appropriate human surrogate (or surrogates if one surrogate does not adequately address the base assumptions). 

Once the correct human surrogate is selected, IARVs will be developed using the standard approach used in the impact biomechanics community. In this approach, human surrogate responses are correlated with human injury outcomes in identical test conditions, both through physical sled testing and Finite Element Models (FEM). Even if the surrogate responses may not reflect the actual human responses (i.e. neck tension in the surrogate and human may be different in identical loading conditions), this approach may still be valid if the surrogate response is sensitive to changes in the configurations that induce injury (either seat design or loading conditions). Once appropriate IARVs are developed, human impact testing will be conducted to validate them.

Target for Closure
Validated IARVs that address sex differences and expected loading dynamics.
Risk Risk of Injury from Dynamic Loads
You are here! Gap DL-201: We do not know how load dynamics and sex differences affect injury risk in spaceflight conditions and do not have adequate injury assessment reference values (IARVs) to mitigate the increased risk of injury to the crew.

Multi-Disciplinary Research Plans

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