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Human Research Program

Spacesuit Trauma Countermeasure System for Intravehicular and Extravehicular Activities

Completed Technology Project

Project Introduction

The objective of this research is to understand human-space suit interaction and design hardware to assess and mitigate injury and discomfort inside the space suit. This will be achieved through the following specific aims.

1.1.1 Specific Aim 1: Analyze data for correlations between anthropometry, space suit components, and injury. Shoulder injuries are some of the most serious and debilitating injuries associated with EVA (extravehicular activity) training. Using a database compiled by NASA personnel on subject anthropometry, training time in different space suit components, and reported shoulder incidents, the following hypotheses will be evaluated:

Hypothesis 1: Anthropometric dimensions will be a predictive factor in identifying astronauts with a reported shoulder incident.

Hypothesis 2: Suit training variables in the planar hard upper torso (HUT), rather than training in the pivoted HUT, will be a predictive factor in identifying astronauts with a reported shoulder incident. Suit training variables are defined by aggregating training information, such number of or percentage of training incidences in the planar or pivoted HUT.

Hypothesis 3: Operational training variables will be a predictive factor in identifying astronauts with a reported shoulder incident. Operational training variables are defined by aggregating training information, such as frequency of training, accumulation of days between training incidences, or career duration of active duty training.

Hypothesis 4: Record of previous injury will be a predictive factor in identifying astronauts with an additional shoulder incident.

Each of these hypotheses investigates a specific causal mechanism found in the literature associated with EVA shoulder injuries and relates it to a reported shoulder incident. Hypothesis 4 will only be evaluated for those subjects with injury incidents directly attributable to the space suit.

1.1.2 Specific Aim 2: Quantify and evaluate human-space suit interaction with a suite of sensors. There is currently no method by which to measure how the person moves inside the space suit. Focusing on the upper body, a pressure sensing tool will be created to quantify human-space suit interaction under different loading regimes. Additionally, a commercially purchased pressure sensing tool will be used over the shoulder under the space suit Hard Upper Torso (HUT). Finally, inertial measurement units (IMUs) will be used to measure and assess kinematics both of the suit and the person inside.

The following design requirements will be evaluated to determine the success or failure in designing a wearable pressure sensing garment for the space suit environment:

Design Requirement 1: A pressure sensing tool will achieve both high wearability and high utility in a space suit environment. Wearability is defined by mobility, comfort, and safety of the user. Utility is defined by range, accuracy, resolution, and coverage of the sensor system.

Design Requirement 2: Human and space suit interaction characterized by interface pressures will show trends consistent with expected loading regimes. Trends are defined by sensor pressure profiles over isolated or functional tasks. Expected loading regimes are defined by subjective feedback or inferred loading based on anticipated contact.

Design Requirement 1 evaluates the performance of the pressure sensing system to ensure it is properly scoped for its intended use. Design Requirement 2 investigates the system’s ability to function properly in the environment of the space suit so its results may be interpreted with confidence.

The pressure sensing tool will be used to evaluate human-space suit interaction to assess consistency of movement. Consistency of movement is an important metric revealing fatigue or changes in biomechanical strategies, both of which could be precursors to EVA injury. The following hypothesis will be evaluated in a human subject experiment inside the space suit:

Hypothesis 5: Subjects with experience working in the space suit will perform motion tasks with consistent movement strategies. Movement strategies are defined by peak pressures averaged over trials or full time averaged pressure profiles.

The commercially purchased pressure sensing tool that is placed at the interface between the shoulder and the Hard Upper Torso will be used to quantify and analyze the pressure distributions and profiles that arise in this region, thus developing a biomechanical understanding of the potential for shoulder injury in pressurized suits. A human subject experiment was performed inside the space suit to evaluate motions and regions that are particularly prone to injury. We determine subject-specific anthropometric regions of concern by considering pressure distributions, frequency of loading, and regional pressure responses. Subject consistency is also evaluated through statistical analysis of the peak pressures.

Hypothesis 6: Subjects perform motion tasks in a consistent manner as measured by pressure values over the shoulder. The kinematic sensors (IMUs) will be used to evaluate human-space suit interaction between body motions and suit motions. Externally measureable suit kinematics may not reflect the human body’s motions inside the suit due to complex design involving non planar bearing or convolutes and pressurization. The following hypothesis will be evaluated in a human subject experiment inside the space suit:

Hypothesis 7: Body and suit joint angle amplitude differ significantly in amplitude for upper body motions.

Hypothesis 8: Body and suit joint angle differ significantly in axis of rotation for upper body motions. The purpose of Hypotheses 6 and 7 are to evaluate differences in suited motion between the person and the space suit. Additionally, we seek to evaluate the impairment of mobility for upper body joints in different suits, using IMUs, as compared to baseline range of motion. The following hypothesis will be evaluated in a human subject experiment inside the space suit:

Hypothesis 9: Space suit pressurization significantly impairs the joint angle amplitude of upper body motions.

1.1.3 Specific Aim 3: Model human-space suit interaction. The purpose of SA3 is to gain a better understanding of the EVA injury mechanisms, particularly strain injuries caused by the Extravehicular Mobility Unit (EMU). The objective is to determine the extent to which muscle activity is affected by the presence of the highly-pressurized space suit. A musculoskeletal human-space suit interaction model is developed in order to quantify musculoskeletal performance of astronauts during Extravehicular Activity, and to assess their injury susceptibility.

1.1.4 Specific Aim 4: Design and Develop modular protective devices. Our work develops conceptual solutions to mitigate injury. As part of this effort, we identify promising materials and build prototype protective devices. We aim to alleviate injury prone areas and improve the person’s comfort within the suit. Protective devices will be integrated to the protective garments and can be personalized for each crewmember.

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