Astronaut EVA : safety, injury and countermeasures

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and, (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 155-161).Extravehicular Activity (EVA) spacesuits are a key enabling technology which allow astronauts to survive and work in the harsh environment of space. Of the entire spacesuit, the gloves may perhaps be considered the most difficult engineering design issue. A significant number of astronauts sustain hand and shoulder injuries during extravehicular activity (EVA) training and operations. In extreme cases these injuries lead to fingernail delamination (onycholysis) or rotator cuff tears and require medical or surgical intervention. In an effort to better understand the causal mechanisms of injury, a study consisting of modeling, statistical and experimental analyses was performed in section I of this thesis. A cursory musculoskeletal modeling tool was developed for use in comparing various spacesuit hard upper torso designs. The modeling effort focuses on optimizing comfort and range of motion of the shoulder joint within the suit. The statistical analysis investigated correlations between the anthropometrics of the hand and susceptibility to injury. A database of 192 male crewmembers' injury records and anthropometrics was sourced from NASA's Johnson Space Center. Hand circumference and width of the metacarpophalangeal (MCP) joint were found to be significantly associated with injuries by the Kruskal-Wallis test. Experimental testing was conducted to characterize skin blood flow and contact pressure inside the glove. This was done as part of NASA's effort to evaluate a hypothesis that fingernail delamination is caused by decreasing blood flow in the finger tips due to compression of the skin inside the extravehicular mobility unit (EMU) glove. The initial investigation consisted of a series of skin blood flow and contact pressure tests of the bare finger, and showed that blood flow decreased to approximately 60% of baseline value with increasing force, however, this occurred more rapidly for finger pads (4N) than for finger tips (ION). A gripping test of a pressure bulb using the bare hand was also performed at a moderate pressure of 13.33kPa (100mmHg) and at a high pressure of 26.66kPa (200mmHg), and showed that blood flow decreased 50% and 45%, respectively. Excessive hyperperfusion was observed for all tests following contact force or pressure, which may also contribute to the onset of delamination. Preliminary data from gripping tests inside the EMU glove in a hypobaric chamber at NASA's Johnson Space Center show that skin blood flow decreased by 45% and 40% when gripping at 3 moderate and high pressures, respectively. These tests show that finger skin blood flow is significantly altered by contact force/pressure, and that occlusion is more sensitive when it is applied to the finger pad than the finger tip. Our results indicate that the pressure on the finger pads required to articulate stiff gloves is more likely to impact blood flow than the pressure on the fingertips associated with tight or ill-fitting gloves. Improving the flexibility of the gloves will therefore not only benefit operational performance, but may also be an effective approach in reducing the incidence of finger injury. Space Policy Abstract EVA injury is only one of many dangers astronauts face in the extreme environment of space. Orbital debris presents a significant threat to astronaut safety and is a growing cause of concern. Since the dawn of satellites in the early 1950's, space debris from intentionally exploded spacecraft, dead satellites, and on-orbit collisions has significantly increased and currently outnumbers operational space hardware. Adding to this phenomenon, the advent of commercial spaceflight and the recent space activities in China and India to establish themselves as spacefairing nations are bound to accelerate the rate of space debris accumulating in low Earth orbit, thus, exacerbating the problem. The policies regulating orbital debris were drafted in the 1960s and 1970s and fail to effectively address the dynamic nature of the debris problem. These policies are not legally enforced under international law and implementation is entirely voluntary. Space debris is a relevant issue in international space cooperation. Unless regulated, some projections indicate space debris will reach a point of critical density, after which the debris will grow exponentially, as more fragments are generated by collisions than are removed by atmospheric drag. Space debris proliferation negatively impacts human spaceflight safety, presents a hazard to orbiting space assets, and may lead to portions of near-Earth orbit becoming inaccessible, thus limiting mission operations. The aim of this research effort was to review current international space policy, legislation and mitigation strategies in light of two recent orbital collision episodes. The first is the February 2009 collision between a defunct Russian Cosmos spacecraft and a commercial Iridium satellite. The second is China's display of technological prowess during the January 2007 intentional demolition of its inactive Fengyun-IC weather satellite using a SC-19 antisatellite (ASAT) missile. In each case the stakeholders, politics, policies, and consequences of the collision are analyzed. The results of this analysis as well as recommendations for alternative mitigation and regulatory strategies are presented.by Roedolph A. Opperman.S.M.in Technology and PolicyS.M

Enhanced dynamic load sensor for the International Space Station : design, development, musculoskeletal modeling and experimental evaluation

Thesis: Ph. D. in Aerospace Systems Engineering, Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 163-179).Prolonged exposure of a vertebrate musculoskeletal system to the microgravity environment of space leads to a reduction in bone mineral density, muscle mass, strength and endurance. Such deconditioning may impede critical astronaut activities and presents an increased injury risk during flight and when exposed to increased gravity like that of Earth or Mars. Exercise countermeasures are used extensively on the International Space Station to mitigate musculoskeletal deconditioning during long duration spaceflight missions. Despite vigorous exercise protocols, bone loss and muscle atrophy are often observed even when countermeasures are in effect. As a first step in understanding the mechanisms of injury and how on-orbit exercise countermeasures compare to those on the ground, an accurate load sensing system is needed to collect ground reaction force data in reduced gravity.To date, no means of continuous, high resolution biomechanical force data collection and analysis has been realized for on-orbit exercise. Such a capability may advance the efficiency of these systems in mitigating the incidence of bone and muscle loss and injury risk by quantifying loading intensity and distribution during exercise in microgravity, thus allowing for cause-effect tracking of ISS exercise regimes and biomechanics. By measuring these forces and moments on the exercise device and correlating them with the post-flight fitness of crewmembers, the efficacy of various exercise devices may be assessed. More importantly, opportunities for improvement, including optimized loading protocols and lightweight exercise device designs will become apparent.The overall goal of this research effort is to improve the understanding of astronaut joint loading during resistive exercise in a microgravity environment through the use of rigorous quantitative dynamic analysis, simulation and experimentation. This is accomplished with the development and evaluation of a novel, self-contained load sensing system. The sensor assembly augments existing countermeasures and measures loads imparted by the crew during exercise. Data collected with this system is used to parameterize a unique musculoskeletal model which is then used to evaluate associated joint reaction forces generated during exercise. The effects of varying body posture and load application points on joint loading were investigated and recommendations for enhancing on-orbit exercise protocols that mitigate both injury and deconditioning are discussed.By validating the sensor and modeling joint loading during on-orbit exercise as described herein, a unique contribution is made in expanding NASA's capability to continuously record and quantify crew loading during exercise on ISS. Data obtained through the system is used to characterize joint loading, inform and optimize exercise protocols to mitigate musculoskeletal deconditioning and may aid in the design of improved, lightweight exercise equipment for use during long-duration spaceflight, including future missions to Mars."This research effort was supported by a NASA Phase I Small Business Innovation Research (SBIR) contract awarded to Aurora Flight Sciences Corporation with MIT as subcontractor. The contract period of performance spanned from June 2014 through August 2016. Contract number: 2012-11 NNX14CS55C"--Page 6by Roedolph Adriaan Opperman.Ph. D. in Aerospace Systems EngineeringPh.D.inAerospaceSystemsEngineering Massachusetts Institute of Technology, Department of Aeronautics and Astronautic

A Non-Invasive Miniaturized-Wireless Laser-Doppler Fiber-Optic sensor for understanding distal fingertip injuries in astronauts

During extra-vehicular activities (EVAs) or space walks astronauts over use their fingertips under pressure inside the confined spaces of gloves/space-suite. The repetitive hand motion is a probable cause for discomfort and injuries to the finger-tips. We describe a new wireless fiber-optic probe that can be integrated inside the astronaut glove for non-invasive blood perfusion measurements in distal finger tips. In this preliminary study, we present blood perfusion measurements while performing hand-grip exercises simulating the use of space tools