Engineering a robotic exoskeleton for space suit simulation

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 177-181).Novel methods for assessing space suit designs and human performance capabilities are needed as NASA prepares for manned missions beyond low Earth orbit. Current human performance tests and training are conducted in space suits that are heavy and expensive, characteristics that constrain possible testing environments and reduce suit availability to researchers. Space suit mock-ups used in planetary exploration simulations are light and relatively inexpensive but do not accurately simulate the joint stiffness inherent to space suits, a key factor impacting extravehicular activity performance. The MIT Man-Vehicle Laboratory and Aurora Flight Sciences designed and built an actively controlled exoskeleton for space suit simulation called the Extravehicular Activity Space Suit Simulator (EVA S3), which can be programmed to simulate the joint torques recorded from various space suits. The goal of this research is to create a simulator that is lighter and cheaper than a traditional space suit so that it can be used in a variety of testing and training environments. The EVA S3 employs pneumatic actuators to vary joint stiffness and a pre-programmed controller to allow the experimenter to apply torque profiles to mimic various space suit designs in the field. The focus of this thesis is the design, construction, integration, and testing of the hip joint and backpack for the EVA S3. The final designs of the other joints are also described. Results from robotic testing to validate the mechanical design and control system are discussed along with the planned improvements for the next iteration of the EVA S3. The fianl EVA S3 consists of a metal and composite exoskeleton frame with pneumatic actuators that control the resistance of motion in the ankle, knee, and hip joints, and an upper body brace that resists shoulder and elbow motions with passive spring elements. The EVA S3 is lighter (26 kg excluding the tethered components) and less expensive (under $600,000 including research, design, and personnel) than a modem space suit. Design adjustments and control system improvements are still needed to achieve a desired space suit torque simulation fidelity within 10% root-mean-square error.by Forrest Edward Meyen.S.M

Robotic Joint Torque Testing: A Critical Tool in the Development of Pressure Suit Mobility Elements

Pressure suits allow pilots and astronauts to survive in extreme environments at the edge of Earth’s atmosphere and in the vacuum of space. One obstacle that pilots and astronauts face is that gas-pressurized suits stiffen when pressurized and greatly limit user mobility. As a result, a critical need exists to quantify and improve the mobility characteristics of pressure suits. A historical survey and critique of pressure-suit testing methodologies is first presented, followed by the results of recent pressure suit testing conducted at the MIT Man-Vehicle Laboratory (MVL). MVL researchers, in cooperation with the David Clark Company (Worcester, MA), used an anthropometrically-realistic robotic space suit tester to quantify pressure suit mobility characteristics of the S1034 Pilot Protective Assembly (PPA), a pressure suit worn by U-2 pilots. This suit was evaluated unpressurized, at a vent pressure of 5.5 kPa (0.8 psi), and at an emergency gauge pressure of 20.7 kPa (3 psi). Joint torque data was collected for elbow flexion/extension, shoulder flexion/extension, shoulder abduction/adduction, and knee flexion/extension motions. The aim of this study was to generate a robust baseline mobility database for the S1034 PPA to serve as a point of comparison for future pressure suit designs, and to provide recommendations for future pressure garment testing

System modeling, design, and control of the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) and implications for atmospheric ISRU processing plants

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 201-204).As humankind expands its footprint in the solar system, it is increasingly important to make use of Earth independent resources to make these missions sustainable and economically feasible. In-Situ Resource Utilization (ISRU), the science of using space resources to support exploration missions, unlocks potential destinations by significantly reducing the mass to be launched from Earth. Mars is considered a promising location with significant indigenous resources. The carbon dioxide that comprises nearly 96% of the Martian atmosphere can be utilized to produce oxygen for propulsion and life support systems. The Mars Oxygen ISRU Experiment (MOXIE) is a payload being developed by NASA for the Mars 2020 mission. MOXIE will demonstrate oxygen production at a rate of at least 6 grams per hour from the Martian atmosphere by using solid oxide electrolysis (SOXE) technology. Individual SOXE cells form a 10-cell SOXE stack. The stack consists of two 5-cell groups to generate oxygen and carbon monoxide molecules from a CO₂ electrolysis reaction. MOXIE is the first step to creating an oxygen processing plant that might enable a human expedition to Mars in the 2030s through the production of the oxygen needed for the propellant for a Mars Ascent Vehicle (MAV). MOXIE will be the first demonstration of ISRU on another planet. The goal of this program is to learn what technological advancements are needed for development of larger scale ISRU systems to support human spaceflight missions. This thesis studies solid oxide electrolysis based atmospheric ISRU systems from a controls and system performance perspective. The purpose is to use the results of this analysis to inform MOXIE operation and the design of a full-scale ISRU system for Mars. A novel, tunable grey electrochemical model is developed from experimental characterization and used to predict oxygen production and safe operational limits for MOXIE. This model is then incorporated into the first multi-domain physical system model of a solid oxide electrolysis system implemented in Simscape. This model, named SimSitu, is used to test MOXIE control interactions and performance. A new control system, The Safe Margin Active Reduction Tracking (SMART) controller is proposed to safely maximize oxygen production from MOXIE. A strategy for characterizing and selecting space flight SOXE stacks based on discoveries from experimental results is also proposed. The models and lessons learned from MOXIE are then applied to make scaling estimates and recommendations for a full-scale ISRU system.by Forrest Edward Meyen.Ph. D