Graduation Year

2023

Document Type

Thesis

Degree

M.S.B.E.

Degree Name

MS in Biomedical Engineering (M.S.B.E.)

Degree Granting Department

Biomedical Engineering

Major Professor

Stephanie Carey, Ph.D.

Committee Member

Robert Frisina, Ph.D.

Committee Member

Kyle Reed, Ph.D.

Committee Member

Ed Collins, B.S.E.E.

Keywords

Force Sensing Resistors, Leg Injury, Mock EMU, Spacesuit Injury, Countermeasures

Abstract

Astronauts perform a multitude of tasks in space, both in the spacecraft and outside of the spacecraft. Extravehicular Activity (EVA) refers to any activity that is completed outside of the spacecraft, whether it is work on the actual spacecraft, spacewalks, or conducting sample collections on other planets and moons. To do this safely, a pressurized Extravehicular Mobility Unit (EMU) or commonly known as the spacesuit is used. There have been multiple iterations of the United States EMU with advances to further optimize the astronaut safety and EVA tasks. However, there is still relatively little information on the movement of the astronaut within their spacesuit, and how the interactions affect them. Astronauts are trained at NASA’s Neutral Buoyancy Laboratory (NBL) on performing tasks while wearing the EMU underwater, but injury, discomfort, and limited mobility have been reported. While many of these injuries and discomfort have been observed and reported over the course for human exploration, a general understanding of the interactions and countermeasures are still in development. This project therefore aimed to contribute to the understanding of human-spacesuit interaction (HSI) particularly of the legs, including the knee and ankle area, using a force sensing system made up of force sensing resistor (FSR) sensors.

The first aim of this project was to conduct a review on previous studies to uncover any trends that were observed in terms of specific locations where injury was observed or measured. Various studies and surveys have been conducted to identify regions of the body where injury is more prominent either due to joint movement or a more rigid suit area. A literature review provided a better scope to the high contact regions, and where to place the sensors during the force sensing experiment. Furthermore, several studies have used motion capture and simulations to visualize the human movement within the spacesuit and characterize the interactions that occur. The second aim of this project was to develop a force sensing system that will be made up of Force Sensing Resistors (FSR) sensors and an Arduino Microcontroller. The system was used to take force measurements of human subjects as they performed common EVA tasks such as walking, squatting, and picking up objects while wearing a mock spacesuit over the sensors. The sensors collected interaction data that was then analyzed for percentage of time that the mock suit was in contact with the astronaut as well as force magnitude and evaluated for the risk of injury based on this value. Furthermore, the data provided an insight on the hot spot areas of the leg where contact occurred most of the time.

From this study, knee and shin interactions were documented for knee ROM, weighted and weightless squats, getting on one knee to pick up an object, and walking tasks. As expected, the knee interacted with the mock LTA in each of the tasks as the joint was bent in a high range. The front and back of the knee saw the highest amount of forces, while the sides saw moderate forces. The shin area interacted with the mock LTA during motions where the mock LTA was pulled up or taut, such as the squatting tasks. Furthermore, it was also found that the shin area can also be affected during the tasks that were isolated in the knee, such as the ROM. However, while interaction results of each task were found and analyzed, this thesis solely stood as the groundwork for human interaction studies of the lower body, as further modifications were necessary to have a successful data trial. Ultimately, the objective of this study to provide a framework for further work on the human-spacesuit interaction in the lower body as achieved, which recommendations on future work and improvements for both the study design and the system.

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