Search Results (5)

Our goal is to further understand how a simulated extravehicular mobility unit (xEMU) spacesuit affects the relative movement of one’s body segments. The effect of the xEMU spacesuit on gait is not yet fully understood. Here, gait was examined in terms of postural strategies, defined by the absolute angle with standard deviation (AAD) and the anchoring index (AI). The AAD values allowed the measurement of the absolute angles of body segments and their standard deviation, whereas the AI provided a measure of how stable a body segment was relative to a global reference frame and the inferior body segment. The body segments examined were the head, thorax, lumbar, and pelvis segments of 17 participants (26.53 ± 6.51 years old). The configurations tested included unsuited, or using a xEMU Vest or a hard upper body torso (HUT) for four walking conditions: eyes open/closed, with either forward or backward walking. The AAD values of the xEMU Vest were insignificant compared to those of the unsuited condition. The HUT significantly affected the AAD values compared to the unsuited condition. The AI for the HUT also indicates a new unique postural strategy being employed by the HUT group that was not previously observed. Full article

Maintaining balance is critical to minimizing astronauts’ risk of falling and reducing injury or suit damage. Previous studies involving spacesuits have not examined the effects of the superior shift of the center of gravity (CoG) on astronauts’ ability to balance. Here, the purpose of our study was to investigate the effects of CoG shift due to a simulated Extravehicular Mobility Unit (xEMU) on balance. Seventeen participants’ standing balance was examined for three test configurations: unsuited, weighted with an Extravehicular Mobility Unit (xEMU) vest, and xEMU hard upper body torso (HUT). Using a Tekscan forceplate walkway, the CoG locations were determined. Balance assessments were performed to determine the limits of stability and standing balance performance during wide or tandem stances with eyes open/closed. The center of pressure (CoP) time series was examined in terms of displacement, velocity, and frequency measures. During the eyes-open wide stance, the xEMU vest significantly increased the mediolateral balance parameters, while the HUT significantly increased the total displacement (TOTEX), mean velocity (MVELO), and mean frequency (MFREQ) of the CoP. In the eyes-closed wide stance, the HUT significantly increased these parameters. In the eyes-closed tandem stance, the xEMU vest significantly decreased the parameters. The xEMU vest significantly reduced the TOTEX, MVELO, and MFREQ (improved standing balance), while the HUT decreased standing balance ability, seen with significant increases in said parameters. By quantifying CoG’s effect on balance, our results form the basis for future balance and posture studies of xEMU spacesuits. Full article

The special use environment and uncertainty of extravehicular activities (EVAs) make it difficult to predict the lifetime consumption of extravehicular spacesuits in the traditional way. This paper presents a flexible reliability dynamic simulation model to predict the life loss of extravehicular spacesuits. Based on the images of traditional reliability change curves, new life assessment parameters, based on geometric analysis, are proposed as indicators of spacesuit life loss. Multiple influence factors are used to correct the spacesuit failure rate. The results of the study show that mission intensity is the main factor affecting the health status of the spacesuit, and the higher the mission intensity, the higher the failure rate. Additionally, the more frequently the spacesuit is used, the more times it is available, however, the overall service time will decrease. Concentrating on the mission at an early stage would lead to a significant and irreversible loss of life. Reliability is higher when more intense work is scheduled later in the EVA. Therefore, it is important to rationalize the mission duration, frequency, and work intensity of spacesuits. These reliability models predict the health status of the spacesuit and assist in optimizing the scheduling of EVA. Full article

The hand-transmitted vibration generated by extravehicular activity (EVA) power tools has an important impact on the health of astronauts and the efficient completion of maintenance tasks when astronauts use EVA power tools for on-orbit maintenance. Based on the hand-transmitted vibration zero-gravity simulation test platform to measure the vibration response of the EVA power tool to human hands. Given the influence of the length of the operating rod and the number of non-detaching fastening devices on daily vibration exposure when astronauts wear extravehicular spacesuit gloves, a second-order polynomial model and a quadratic cumulative nonlinear model of daily vibration exposure are established. The experimental results show that the second-order polynomial model is more explanatory and predictive of the test data in the scope of the test. The R-values of the palm and opisthenar prediction model are 0.9930 and 0.9940 respectively, and the RMSEs are $7.973\times {10}^{-4}$ m/s² and $1.034\times {10}^{-3}$ m/s². The quadratic cumulative nonlinear model can accurately predict the vibration exposure of the hand outside the scope of the test. This study can provide theoretical reference and data support for the prediction of vibration exposure generated by astronauts using the EVA power tools during on-orbit maintenance. Full article

The objective of this paper is to accurately measure the vibration response of tools and hands by simulating the hand-held power tools, which are operated by astronauts wearing extravehicular spacesuit gloves under microgravity conditions. The total vibration value and the daily vibration exposure of the subject’s hand are obtained. The results show that the opisthenar is more sensitive to the vibration frequency less than 200 Hz. After frequency weighting, the vibration exposure in the composite state of wearing an unpressurized spacesuit glove on the opisthenar is 23.6% greater than the vibration exposure of the palm, and for the bare hand, the percentage is 25.1% under the same condition. Because the operation time of tightening a screw is longer than that of loosening, the tightening operation performed by wearing spacesuit gloves produces 15.7% more mean vibration exposure on the palm and opisthenar than the loosening operation. The results of vibration transmissibility characterized by the total vibration weighted method and the total vibration unweighted method are 0.039 and 0.094, respectively. In comparison with bare hands, the mean daily vibration exposure on the palm and opisthenar in the composite state by wearing spacesuit gloves is 16.3% less, indicating that the unpressurized spacesuit gloves have an effect on vibration reduction. The research reveals the law of hand-transmitted vibration caused by the coupling of the extravehicular activities (EVA) power tools and spacesuit gloves, and provides a novel method for further similar tests and verification of hand-held EVA power tools. Full article