Space exploration challenges : characterization and enhancement of space suit mobility and planetary protection policy analysis

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.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 189-193).This thesis addresses two challenges associated with advanced space and planetary exploration: characterizing and improving the mobility of current and future gas pressurized space suits; and developing effective domestic Planetary Protection policies for the emerging private space industry. Gas-pressurized space suits are known to be highly resistive to astronaut movement. As NASA seeks to return to planetary exploration, there is a critical need to improve full body space suit mobility for planetary exploration. Volume effects (the torque required to displace gas due to internal volume change during movement) and structural effects (the additional torque required to bend the suit materials in their pressurized state) are cited as the primary contributors to suit rigidity. Constant volume soft joints have become the design goal of space suit engineers, and simple joints like the elbow are believed to have nearly achieved such performance. However, more complex joints like the shoulder and waist have not yet achieved comparable optimization. As a result, it is hypothesized that joints like the shoulder and waist introduce a third, and not well studied, contributor to space suit rigidity: pressure effects (the additional work required to compress gas in the closed operating volume of the suit during movement). This thesis quantifies the individual contributors to space suit rigidity through modeling and experimentation. An Extravehicular Mobility Unit (EMU) space suit arm was mounted in a -30kPa hypobaric chamber, and both volume and torque measurements were taken versus elbow angle. The arm was tested with both open and closed operating volumes to determine the contribution of pressure effects to total elbow rigidity. These tests were then repeated using a full EMU volume to determine the actual impact of elbow pressure effects on rigidity when connected to the full suit. In both cases, structural and volume effects were found to be primary contributors to elbow joint rigidity, with structural effects dominating at low flexion angles and volume effects dominating at high flexion angles; pressure effects were detected in the tests that used only the volume of the arm, but were found to be a secondary contributor to total rigidity (on average 75°) flexion angles, suggesting that the underlying mechanisms of these effects are not yet fully understood, and that current models predicting structural effects behavior do not fully represent the actual mechanisms at work. The detection of pressure effects in the well-optimized elbow joint, even if only in a limited volume, suggests that these effects may prove significant for sub-optimized, larger, multi-axis space suit joints. A novel, fast-acting pressure control system, developed in response to these findings, was found to be capable of mitigating pressure spikes due to volume change (and thus, pressure effects). Implementation of a similar system in future space suit designs could lead to improvements in overall suit mobility. A second study, which focused on the implications of the development of the US private space industry on domestic Planetary Protection policy, is also presented. As signatories of the 1967 Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space (commonly known as the Outer Space Treaty), the United States is responsible for implementing Planetary Protection procedures designed to prevent biological contamination of the Solar System, as well as contamination of the Earth by any samples returned from extra-terrestrial bodies. NASA has established policies and procedures to comply with this treaty, and has successfully policed itself independently and autonomously since the signing of the treaty. However, for the first time in the history of the American space program, private entities outside of NASA have developed the capability and interest to send objects into space and beyond Earth orbit, and no current protocol exists to guarantee these profit-minded entities comply with US Planetary Protection obligations (a costly and time-consuming process). This thesis presents a review of US Planetary Protection obligations, including NASA's procedures and infrastructure related to Planetary Protection, and based on these current protocols provides policy architecture recommendations for the emerging commercial spaceflight industry. It was determined that the most effective policy architecture for ensuring public and private compliance with Planetary Protection places NASA in control of all domestic Planetary Protection matters, and in this role NASA is charged with overseeing, supporting, and regulating the private spaceflight industry. The underlying analysis and architecture tradeoffs that led to this recommendation are presented and discussed.by Bradley Thomas Holschuh.S.M.in Technology and PolicyS.M

Mechanical counter-pressure space suit design using active materials

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 253-265).Mechanical counter-pressure (MCP) space suits have the potential to greatly improve the mobility of astronauts as they conduct planetary exploration activities; however, the underlying technologies required to provide uniform compression in an MCP garment at sucient pressures (29.6 kPa) for space exploration have not yet been demonstrated, and donning and dong of such a suit remains a signicant challenge. This research effort focuses on the novel use of active material technologies to produce a garment with controllable compression capabilities to address these problems. We the describe the modeling, development, and testing of low spring index (C = 3) nickel titanium (NiTi) shape memory alloy (SMA) coil actuators designed for use in wearable compression garments. Several actuators were manufactured, annealed, and tested to assess their de-twinning and activation characteristics. We then describe the derivation and development of a complete two-spring model to predict the performance of hybrid compression textiles combining passive elastic fabrics and integrated SMA coil actuators based on 11 design parameters. Design studies (including two specifically tailored for MCP applications) are presented using the derived model to demonstrate the range of possible garment performance outcomes based on strategically chosen SMA and material parameters. Finally, we present a novel methodology for producing modular 3D-printed SMA actuator cartridges designed for use in compression garments, and test 5 active tourniquet prototypes (made using these cartridges and commercially available fabrics) to assess the eect of SMA actuation on the tourniquet compression characteristics. Our results demonstrate that hybrid active tourniquet prototypes are highly effective, with counter-pressures increasing by an average of 81.9% when activated (taking an average of only 23.7 seconds to achieve steady state). Maximum average counter-pressures reached 34.3 kPa, achieving 115.9% of the target MCP counter-pressure. We observed signicant spatial variability in the active counter-pressure profiles, stemming from high friction, asymmetric fabric stretching, and near-field pressure spikes/voids caused by the SMA cartridge. Modifications to reduce tourniquet friction were effective at mitigating a proportion of this variability. System performance and repeatability were found to depend heavily on the passive fabric characteristics, with performance losses attributable to irrecoverable fabric strain, degradation in fabric elastic modulus, and non-linear modulus behavior. The results of this research open the door to new opportunities to advance the field of MCP spacesuit design, as well as opportunities to improve compression garments used in healthcare therapies, competitive athletics, and battlefield medicine.by Bradley Thomas Holschuh.Ph. D