Browsing by Author "Kim, Han"
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Item Design for Custom Shaped Spacesuit, and Optimizing the Fit of Spacesuit Hard Upper Torsos(2023 International Conference on Environmental Systems, 2023-07-16) Green, Will; De Leon, Pablo; Rhoades, Jesse; Kim, HanThe next era of human spaceflight will see the return of astronauts to the lunar surface, requiring frequent planetary EVAs by an astronaut corps in diverse body shapes and sizes. Future suits must be designed to accommodate the growing and changing population of astronauts, and provide optimal fit, comfort, and mobility. The torso of the spacesuit is a critical component in determining the fitment and function of a suit system. This paper presents a design framework for generating custom shaped Hard Upper Torsos (HUTs) from a 3-dimensional body scan. In this framework a principal component (PC) analysis was performed on a 3D body scan database of the general population. A set of clusters was statistically identified, each of the which represents a distinct torso shape and size. The computer design of the HUT geometry was manually adjusted for optimal fit for each cluster. The obtained HUT geometries were processed for PC analysis and statistically modelled, so that an arbitrary torso shape can predict a HUT geometry hypothetically yielding an optimal fit. While this technique constituted a custom sizing scheme, a “standard” sizing scheme was additionally built, in which a discrete number of HUT sizes (small, medium, large, etc.) was identified for maximum accommodation of the population. To determine the improvement of fit, 3D printed mockups were fabricated for the standard and the custom shaped HUT, based on the 3D body scan of test volunteers. The perceived fit and comfort was assessed by a structures survey. Mobility was measured by patterns and ranges of the upper extremity motions. The testing and data analysis is currently in progress, and the details will be presented in the full manuscript.Item Development of ARGOS Offloading Assessments and Methodology for Lunar EVA Simulations(2023 International Conference on Environmental Systems, 2023-07-16) Jarvis, Sarah; Vu, Linh; Gupta, Garima; Benson, Elizabeth; Kim, Han; Rhodes, Richard; Rajulu, SudhakarThe Active Response Gravity Offload System (ARGOS) at NASA Johnson Space Center (JSC) is an analog environment that can offload pressurized suited subjects at various gravity levels. The suit is suspended from a robotic overhead crane by a cable connected to the suit via a gimbal with an adjustable pivot point. There has been increased interest in providing lunar pressurized suited training at ARGOS in preparation for lunar missions. Determination of the appropriate gimbal pivot point location for a given subject is vital for a high-fidelity and functional lunar simulation. Interactions between the pivot point location and center of gravity (CG) can result in righting moments that may lead to artificially stable or unrealistically challenging configurations. Changing the pivot point location is time consuming and repeated adjustment can result in significant loss of valuable pressurized suited time. This paper aims to share the knowledge obtained from the offloading characterization efforts during pressurized suited testing at ARGOS and document the ongoing process to define an appropriate pivot point location through iterative quantitative and qualitative assessments. The human-spacesuit CG locations for the ARGOS lunar simulation were estimated using a 3D body scan and density model combined with spacesuit hardware CAD and specifications. Early pilot testing of the gimbal revealed that setting the pivot point coincident with the modeled CG location was not always possible due to the current gimbal design, and small shifts forward and aft had noticeable effects on subject stability. Fifteen subjects performed a series of CG-related tasks in the xEMU spacesuit to assess simulation acceptability. Through iterative testing, this task list evolved to streamline the process needed to efficiently identify a suitable pivot point for a given subject. The developed methodology will be critical to determine pivot point selection for astronaut training in the xEMU ARGOS environment.Item Development of Weigh-out Process and Evaluations for Underwater Partial Gravity EVA Simulations(2024 International Conference on Environmnetal Systems, 2024-07-21) Sabahi, Pouyan; Yao, Joseph; Tejral, Zach; Flaspohler, Christine; Vu, Linh; Kim, Han; Rajulu, Sudhakar; Newby, NathanielFor the upcoming Artemis lunar missions, astronauts will need to train in a spacesuit where partial gravity can be simulated such as NASA Neutral Buoyancy Lab (NBL). At the NBL, dive weights and foam can be added around the spacesuit to attain a satisfactory center of buoyancy (CB) and center of gravity (CG) location to simulate the lunar gravity (1/6th G) effects. If CG and CB are not co-located properly, incorrect righting moments can be introduced, and both simulation quality and EVA task performance can be impaired. Based on the findings from the initial testing using xEMU spacesuits, it was observed that the weigh-out method (i.e., determination of the weights and foam quantities and position) needed further development to improve the simulation quality, especially for the subjects who experienced excessive instability. This paper aims to present the on-going effort to improve the weigh-out process for enabling NBL lunar EVA simulations. For this effort, a human-suit model was created to use suit CAD and 3D human body scans to estimate both CB and CG location for each suited subject. NBL weigh-out testing was performed to characterize the effects of CG and CB positioning, in which the 3D human-suit model was used to determine optimal weigh-out combinations of weights and foam. Postural, balance, and subjective feedback were gathered for each weigh-out configuration. The results indicated that, as the CB was shifted higher and the CB and CG located closer to each other, the subject tended to be more stable, and their EVA performance improved. A high CB location was then prioritized across 4 additional subjects in both small and large size spacesuits. When compared to the initial xEMU test series, improved performance was observed across all subjects as the CB moved higher and aligned closer to the system CG.Item Integrative Fit Assessments for Multi-Component Stack-Up of xEMU(50th International Conference on Environmental Systems, 7/12/2021) Davis, Kristine; Rhodes, Richard; Rajulu, Sudhakar; Hernandez, Yaritza; Benson, Elizabeth; Jarvis, Sarah; Gupta, Garima; Kim, HanSufficient mobility, proper fit, and adequate comfort are critical design goals for the Exploration Extravehicular Mobility Unit (xEMU), NASA's next generation spacesuit. While component-wise fit assessments can provide baseline information, the wearers' experience might be different when multiple components are stacked and integrated together. This study is concerned with the fit, comfort, and mobility associated with the stack-up of the Hard Upper Torso (HUT), Lower Torso Assembly (LTA) and other interconnecting components. The first aim of this study was to identify the sizing ring configuration preferred by wearers of different body shapes and sizes. Sizing rings are inserts placed between the Body Seal Closure of the HUT and the waist bearing. Sizing rings of different heights can be combined to accommodate the wearer's torso size. Human test subjects wore the stack-up of 3D printed mockups and performed prescribed functional EVA postures as they were surveyed for feedback on fit and comfort. The second aim was to assess the effect of elongating the brief height by 50.8 mm, instead of using a same height sizing ring. The hypothetical benefit was a closer alignment of the mechanical pivot point of the brief with the anatomical low back joint center, especially for wearers with a longer torso. Human-in-the-loop testing was performed to compare the baseline and elongated brief configurations, with a focus on mobility and comfort differences. Based on the test outcome, a statistical model is currently in development to predict the optimal sizing ring and brief configuration as a function of the wearer's anthropometry. This study can also help to determine the largest and smallest body sizes in crew populations that can be accommodated with the HUT-to-LTA stack-up, with increased mobility and comfort.Item Machine-learning Solution for Automatic Spacesuit Motion Recognition and Measurement from Conventional Video(51st International Conference on Environmental Systems, 7/10/2022) Vu, Linh; Kim, Han; Gordon, Alex; Rajulu, SudhakarExtravehicular Activity (EVA) spacesuits exhibit unique movement patterns due to their design characteristics. Mobility assessments using traditional motion capture systems are cost prohibitive and not feasible for some training conditions (e.g., simulated lunar outdoor terrain). This paper aims to present the ongoing development of machine learning solutions to quantify suit motions from conventional videos without special sensors or hardware. Given the fast growth in deep/machine learning technologies, external expertise was sought from open-source communities. This was expected to accelerate development and provide more cost-effective, time-saving solutions. This work was selected for a NASA Crowdsourcing project through an agency-wide solicitation. Partnerships were formed with the NASA JSC Center of Excellence for Collaborative Innovation and an execution crowdsourcing platform partner to solicit framework developments from external contenders. NASA provided contenders with video clips of spacesuits and simultaneously measured motion capture data during EVA simulation tasks. The contenders used this data to train and develop generalized algorithms to predict motions. At the end of the crowdsourcing event, five solutions were selected from 250 submissions. Each submission was tested and scored using video clips not previously disclosed to the contenders. The scoring metrics measured how well the algorithm detected the suit shape, the 2D suit joint detection accuracy, and 3D joint detection accuracy. The winning solution was able to achieve roughly 85% prediction accuracy (weighted combination of scoring metrics). Overall, the algorithms could efficiently detect various types of spacesuits and motions across different EVA simulation environments such as the Neutral Buoyancy Lab (NBL). However, 3D joint identification is less reliable when parts of the suit were obstructed in the image. After continued improvements and validation, the fully developed system will enable EVA stakeholders to quantify suit kinematic patterns, which can help optimize suit, hardware, and task designs.Item xEMU Lower Torso Assembly (LTA) Brief Fleet Sizing Study(2020 International Conference on Environmental Systems, 2020-07-31) Davis, Kristine; Rhodes, Richard; Kim, Han; Benson, Elizabeth; Hernandez, Yaritza; Vu, Linh; Rajulu, SudhakarThe Exploration Extravehicular Mobility Unit (xEMU) project is tasked with building a spacesuit for the lunar 2024 missions. These missions will require a mobile Lower Torso Assembly (LTA) to fit the required range of astronauts’ anthropometry with optimal mobility. The goal of this work is to predict the proportion of the current and projected crew population accommodated by the new LTA design. Initially, virtual fit checks were conducted via CAD modeling. Body shape manikins were iteratively positioned inside the CAD geometry. The resultant suit-to-body contact and overlap was quantified and used to develop a statistical model to predict the probability of fit. Twenty test subjects whose predicted fit is at a borderline level are currently being assessed. The subjects don/doff a 3D printed LTA mockup, and perform basic functional movements, including walking, kneeling and squatting. 3D scans are recorded, and a questionnaire is administered for the overall fit and any discomfort locations. The statistical model will be updated using the physical test outcome and projected to a large database of approximately 2000 male and 1000 female body shapes from the US Army. The model will estimate the overall proportion of the accommodated population to characterize the anthropometry of the crew who would fit in the LTA. This will determine if the current LTA sizing is adequate to meet the xEMU requirements.