Elizabeth Benson

The Effects of Extravehicular Activity (EVA) Glove Pressure on Tactility

The purpose of the current study was to quantify finger tactility while wearing a Phase VI Extravehicular Activity (EVA) glove. Subjects were fully suited in an Extravehicular Mobility Unit (EMU) suit. Data was collected under three conditions: bare-handed, gloved at 0 psid, and gloved at 4.3 psid. To test tactility, a series of 30 tactile stimuli (bumps) were created that varied in both height and width. With the hand obscured, subjects applied pressure to each bump until detected tactilely. The amount of force needed to detect each bump was recorded using load cells located under a force plate. Results showed that amount of force needed to detect a bump was positively related to width, but inversely related to height. In addition, as the psi of the glove increased, more force was needed to detect the bump. In terms of application, it was possible to determine the optimal width and height a bump needs to be for a specific amount of force applied for tactility.

Use of Traditional and Novel Methods to Evaluate the Influence of an EVA Glove on Hand Performance

The gloved hand is one of an astronaut s primary means of interacting with the environment, and any restrictions imposed by the glove can strongly affect performance during extravehicular activity (EVA). Glove restrictions have been the subject of study for decades, yet previous studies have generally been unsuccessful in quantifying glove mobility and tactility. Past studies have tended to focus on the dexterity, strength, and functional performance of the gloved hand; this provides only a circumspect analysis of the impact of each type of restriction on the glove s overall capability. The aim of this study was to develop novel capabilities to provide metrics for mobility and tactility that can be used to assess the performance of a glove in a way that could enable designers and engineers to improve their current designs. A series of evaluations were performed to compare unpressurized and pressurized (4.3 psi) gloved conditions with the ungloved condition. A second series of evaluations were performed with the Thermal Micrometeoroid Garment (TMG) removed. This series of tests provided interesting insight into how much of an effect the TMG has on gloved mobility - in some cases, the presence of the TMG restricted glove mobility as much as pressurization did. Previous hypotheses had assumed that the TMG would have a much lower impact on mobility, but these results suggest that an improvement in the design of the TMG could have a significant impact on glove performance. Tactility testing illustrated the effect of glove pressurization, provided insight into the design of hardware that interfaces with the glove, and highlighted areas of concern. The metrics developed in this study served to benchmark the Phase VI EVA glove and to develop requirements for the next-generation glove for the Constellation program.

The Effect of Pressurized Space Gloves on Operability of Cursor Controls, Mobility, and Strength

Space Human Factors Engineering (SHFE) researchers at Johnson Space Center (JSC), in collaboration with the Extravehicular Activity (EVA) Suit Team, performed a glove box study investigating operability of cursor controls, mobility, and strength of the participants while wearing pressurized gloves. Performance time was collected under a range of glove pressures (0, 0.8, 4.3, 6.3, and 8.1 psid), as well as bare-handed. Controls tested included a Castle switch, Rocker switch, and Trackball. The study was undertaken to determine impacts of operating controls under higher than nominal (i.e., > 4.3 psid) suit pressures. Operability when using cursor control devices was tested with an interactive software task representative of the types of actions that will be required to interact with space vehicle displays (display navigation and selection of a target). Results indicate that cursor control devices can be operated at pressures up to 8.1 psid, albeit with some difficulty. With respect to mobility, increased pressure seemed to affect thumb mobility more than the fingers. As the number of participants was limited in this initial feasibility study, further studies should be performed with a larger number of participants to evaluate performance with different hand/glove sizes, as well as with alternative device designs that are more ergonomically flexible and forgiving of hand and finger dimension changes brought on by increases in pressure. Results from this study may have implications for other gloved task environments.

An Ergonomic Evaluation of the Extravehicular Mobility Unit (EMU) Spacesuit Hard Upper Torso (HUT) Size Effect on Mobility, Strength, and Metabolic Performance

Introduction: The objective of this project was to develop a comprehensive methodology to assess the suit fit and performance differences between a nominally sized extravehicular mobility unit (EMU) spacesuit and a nominal +1 (plus) sized EMU. Method: This study considered a multitude of evaluation metrics including 3D clearances and pressure point mapping to quantify potential issues associated with using off-nominal suit sizes. Results: There were minimal differences with using a plus suit size. Discussion: Analysis of the results indicates that future suit size evaluations should consider this ergonomic approach to understand and mitigate potential suit fit and performance issues.

Development of Underwater Motion Capture System for Space Suit Mobility Assessment

The objective of this study was to develop and deploy a novel motion capture system that utilizes off-the-shelf, dive-rated hardware to measure 3-D whole body reach envelopes of space suits in an underwater analog, which simulates a microgravity environment. The accuracy of the developed system was compared to a gold standard motion capture system in a dry-land condition before deployment. This study is ultimately aimed at providing a methodology for quantitative metrics to evaluate and compare the mobility performances of a newly developed prototype space suit versus an existing space suit at the Neutral Buoyancy Laboratory (NBL) at NASA’s Johnson Space Center.

Development of a Depth Camera-Based Instructional Tool for Resistive Exercise During Spaceflight

Resistive exercise is essential to maintaining proper musculoskeletal health during spaceflight. Therefore crewmembers receive instruction from strength, conditioning, and rehabilitation specialists on proper exercise technique to maximize exercise effectiveness and prevent injuries. However, long duration missions can make real-time exercise instruction and feedback problematic. A depth camera-based software tool was developed to provide exercise instruction and feedback during the deadlift exercise. The software tool uses a machine learning algorithm to identify 5 common deadlift technique mistakes. A subset containing 2 subjects with no deadlift training experience were coached on the deadlift exercise and separated into 2 groups: experimental group using the software tool or a control group without the tool. Motion-capture data were collected to evaluate the kinematic characteristics between the test and control group. It was found that the software tool assisted with increased torso, hip, and knee joint angle consistency and improved form during deadlifts.

Evaluating Suit Fit Using Performance Degradation

The Mark III planetary technology demonstrator space suit can be tailored to an individual by changing the modular components of the suit, such as the arms, legs, and gloves, as well as adding or removing sizing inserts in key areas. A method was sought to identify the transition from an ideal suit fit to a bad fit and how to quantify this breakdown using a metric of mobility-based human performance data. To this end, the degradation of the range of motion of the elbow and wrist of the suit as a function of suit sizing modifications was investigated to attempt to improve suit fit. The sizing range tested spanned optimal and poor fit and was adjusted incrementally to compare each joint angle across five different sizing configurations. Suited range of motion data were collected using a motion capture system for nine isolated and functional tasks utilizing the elbow and wrist joints. A total of four subjects were tested with motions involving both arms simultaneously as well as the right arm by itself. Findings indicated that no single joint drives the performance of the arm as a function of suit size; instead it is based on the interaction of multiple joints along a limb. To determine a size adjustment range where an individual can operate the suit at an acceptable level, a performance detriment limit was set. This user-selected limit reveals the task-dependent tolerance of the suit fit around optimal size. For example, the isolated joint motion indicated that the suit can deviate from optimal by as little as -0.6 in to -2.6 in before a 10% performance drop occurs in the wrist or elbow joint. This study identified a preliminary method to quantify the impact of size on performance and developed a new way to gauge tolerances around optimal size.

Functional Mobility Testing: A Novel Method to Create Suit Design Requirements

This study was performed to aide in the creation of design requirements for the next generation of space suits that more accurately describe the level of mobility necessary for a suited crewmember through the use of an innovative methodology utilizing functional mobility. A novel method was utilized involving the collection of kinematic data while 20 subjects (10 male, 10 female) performed pertinent functional tasks that will be required of a suited crewmember during various phases of a lunar mission. These tasks were selected based on relevance and criticality from a larger list of tasks that may be carried out by the crew. Kinematic data was processed through Vicon BodyBuilder software to calculate joint angles for the ankle, knee, hip, torso, shoulder, elbow, and wrist. Maximum functional mobility was consistently lower than maximum isolated mobility. This study suggests that conventional methods for establishing design requirements for human-systems interfaces based on maximal isolated joint capabilities may overestimate the required mobility. Additionally, this method provides a valuable means of evaluating systems created from these requirements by comparing the mobility available in a new spacesuit, or the mobility required to use a new piece of hardware, to this newly established database of functional mobility.

FUNCTIONAL MOBILITY TESTING: A NOVEL METHOD TO ESTABLISH HUMAN- SYSTEM INTERFACE DESIGN REQUIREMENTS

Across all fields of human-system interface design it is vital to posses a sound methodology dictating the constraints on the system based on the capabilities of the human user. These limitations may be based on strength, mobility, dexterity, cognitive ability, etc. and combinations thereof. Data collected in an isolated environment to determine, for example, maximal strength or maximal range of motion would indeed be adequate for establishing not-to-exceed type design limitations, however these restraints on the system may be excessive over what is basally needed. Resources may potentially be saved by having a technique to determine the minimum measurements a system must accommodate. This paper specifically deals with the creation of a novel methodology for establishing mobility requirements for a new generation of space suit design concepts. Historically, the Space Shuttle and the International Space Station vehicle and space hardware design requirements documents such as the Man-Systems Integration Standards [1] and International Space Station Flight Crew Integration Standard [2] explicitly stated that the designers should strive to provide the maximum joint range of motion capabilities exhibited by a minimally clothed human subject. In the course of developing the Human-Systems Integration Requirements (HSIR) [3] for the new space exploration initiative (Constellation), an effort was made to redefine the mobility requirements in the interest of safety and cost. Systems designed for manned space exploration can receive compounded gains from simplified designs that are both initially less expensive to produce and lighter, thereby, cheaper to launch.