Development of head injury assessment reference values based on NASA injury modeling

Wyle Integrated Science and Engineering Group, Houston, TX 77058, USA.
Stapp car crash journal 11/2011; 55:49-74.
Source: PubMed


NASA is developing a new crewed vehicle and desires a lower risk of injury compared to automotive or commercial aviation. Through an agreement with the National Association of Stock Car Auto Racing, Inc. (NASCAR®), an analysis of NASCAR impacts was performed to develop new injury assessment reference values (IARV) that may be more relevant to NASA's context of vehicle landing operations. Head IARVs associated with race car impacts were investigated by analyzing all NASCAR recorded impact data for the 2002-2008 race seasons. From the 4015 impact files, 274 impacts were selected for numerical simulation using a custom NASCAR restraint system and Hybrid III 50th percentile male Finite Element Model (FEM) in LS-DYNA. Head injury occurred in 27 of the 274 selected impacts, and all of the head injuries were mild concussions with or without brief loss of consciousness. The 247 noninjury impacts selected were representative of the range of crash dynamics present in the total set of impacts. The probability of head injury was estimated for each metric using an ordered probit regression analysis. Four metrics had good correlation with the head injury data: head resultant acceleration, head change in velocity, HIC 15, and HIC 36. For a 5% risk of AIS≥1/AIS≥2 head injuries, the following IARVs were found: 121.3/133.2 G (head resultant acceleration), 20.3/22.0 m/s (head change in velocity), 1,156/1,347 (HIC 15), and 1,152/1,342 (HIC 36) respectively. Based on the results of this study, further analysis of additional datasets is recommended before applying these results to future NASA vehicles.

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    09/2012; National Aeronautics and Space Administration.
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    ABSTRACT: Currently, NASA occupant protection standards are primarily based on the Multi-axial Dynamic Response Criteria, which NASA refers to as the Brinkley Dynamic Response Criterion (BDRC). The BDRC was developed by the United States Air Force (USAF) and adopted by NASA in the mid-1990s during the development of the Assured Crew Return Vehicle (ACRV) and evaluation of the Soyuz three-person crew vehicle landing impact tests. The BDRC criteria includes a dynamic model, which is used to evaluate the risk of injury using a series of lumped parameter models with mass, spring, and damping properties. The individual model units are arranged orthogonally to respond to linear accelerations and linear components of angular accelerations measured on the vehicle occupant seat. During the BDRC development, these model responses were related to human injury data to develop low, medium, and high injury risk limits. Because of the simplicity of the BDRC, it is very attractive to designers, as it is very simple to evaluate for many design cases with only seat accelerations. However, because of these simplifications and the specific characteristics of the seating systems used, there are application criteria or rules that are necessary to correctly apply the model and interpret the results. In addition, because of the subjects used in the development of the BDRC and some unique considerations for NASA’s applications, several limitations have been identified that limit the injury prediction capabilities of the model. The purpose of this document is to review the BDRC development, document the rules necessary to apply the BDRC, identify limitations for NASA’s application, and describe additional testing and analysis methods necessary to supplement the BDRC.
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    ABSTRACT: A novel approach has been developed to define acceptable risk guidelines for human spaceflight injuries occurring during dynamic phases of flight (launch, abort, and landing). These risk guidelines are a driver for both vehicle and mission design, which in turn drive cost and schedule. The approach outlined in this document was based on three specific inputs. First, an Operationally Relevant Injury Scale was developed to categorize injuries within the framework of the spaceflight environment. Second, a systematic consideration of injury risk in other analogous programs and historic space programs was gathered for a pragmatic examination of realistic injury probabilities. Third, estimated Orion landing types and probabilities were determined along with the type of tasks crewmembers would be expected to perform in each type of situation to ensure mission success. These landing scenarios helped to define the range of injuries expected for capsule-based spaceflight. Considering each of these inputs, a panel of experts convened to define the absolute highest level of injury allowable that still achieved mission success. Once this level was defined, the panel began buying-down the risk with other considerations: ethical, medical, political, and programmatic. The results of this effort led to a Definition of Acceptable Risk for space capsule landings that may be used to help set new standards to protect crews during dynamic phases of flight.
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