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Neutral Buoyancy Technologies for Extended Performance Testing of Advanced Space Suits

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Neutral Buoyancy Technologies for Extended Performance Testing of Advanced Space Suits 2003-01-2415 Neutral Buoyancy Technologies for Extended Performance Testing of Advanced Space Suits David L. Akin and Jeffrey R. Braden Space Systems Laboratory, University of Maryland Copyright © 2003 SAE International ABSTRACT Performance of new space suit designs is typically Orlan suit. Similarly, focus on manned missions to Mars tested quantitatively in laboratory tests, at both the and return to the Lunar surface provide the drive to component and integrated systems levels. As the suit develop advance space suit systems for these moves into neutral buoyancy testing, it is evaluated endeavors. qualitatively by experienced subjects, and used to perform tasks with known times in earlier generation The development of new, or improved, suit components suits. This paper details the equipment design and test typically culminates in laboratory tests which methodology for extended space suit performance quantitatively measure the performance characteristics metrics which might be achieved by appropriate of the new component. Tests at this level may include instrumentation during operational testing. This paper bench-top measurements of joint torque, range of presents a candidate taxonomy of testing categories motion, strength and/or durability. Next, improved applicable to EVA systems, such as reach, mobility, components are integrated into the suit system and workload, and so forth. In each category, useful tested at the systems level; again, typically through technologies are identified which will enable the standard joint torque, range of motion and strength/ necessary measurements to be made. In the subsequent durability tests [1] [2]. section, each of these technologies are examined for feasibility, including examples of existing technologies At this point, further performance data is typically where available. All of these measurements systems collected qualitatively by experienced test subjects who taken together can provide a much more detailed and can compare new suit performance with that of earlier quantitative evaluation of a pressure suit in realistic generation suits. Facilities like NASA’s Neutral Buoyancy simulations of its operating environment. Laboratory (NBL) at the Johnson Space Center are the typical sites for this level of testing for EVA suits. Planetary suits typically find performance evaluation in INTRODUCTION simulated Martian environments like the simulated Lunar/ Mars terrain area at the NASA Johnson Space Center, Space suit design is a field of continual development or in field trials such as those of recent years at Silver which works to further the capabilities of astronauts Lake, Meteor Crater, or the Mars Society testing grounds working in space or on a planetary surface. The at Devon Island [3] [4]. These simulations can, and are, tremendous increase in extravehicular activities (EVA) being improved by testing under the reduced gravity associated with the International Space Station (ISS) conditions achieved during parabolic flight aboard the provides a continual impetus to improve the Shuttle KC-135. extravehicular mobility unit (EMU) as well as the Russian All of these methods have contributed to substantial improvements in space suit design, and each has proven useful over the years. However, each method of system level testing is not without its drawbacks. complete picture of human/suit performance? Within Terrestrial testing of planetary suits provides a wealth of each metric, what technologies are required to provide data on suit design; however, the reduced gravity of useful quantiative measures of performance? Some both Mars and the Moon will have significant effects on beneficial candidates can be summarized under the suit performance which are not being captured in such following categories. testing. KC-135 flights, while they do capture reduced gravity conditions, are prohibitively expensive and short DEXTERITY AND REACH METRICS in duration. And across the board, including the neutral buoyancy tests for EVA suit evaluation, the largest problem with current performance testing is a lack of The vast majority of EVA development consists of quantitative data collection. answering two questions: Can you reach it? And when you do, can you operate it? A greater degree of rigor in To achieve revolutionary advances in pressure suit the quantification of reach and dexterity metrics would design, testing methodologies need to be further provide hard metrics on critical suit capabilities, as well developed to allow quantitative testing of performance as provide the necessary data base for advanced during suit operations testing, which may be simulations of pressure suit operations. development, training, or even in-flight operations. This paper proposes an integrated approach to advanced In this category, the objective is to quantify the reach of suit instrumentation and testing which applies at a the suit with respect to some fiducial point on the suit number of levels, ranging from simple methodologies to itself. Often this has been the suit upper torso; this obtain quantitative comparison data, to unobtrusive provides a reach envelope of the arms alone. This data sensor systems which will provide information on crew may be reconstructed by forward transformation of arm sensorimotor adaptation, metabolic workload, and other joint angles without external measurements. In other significant metrics of performance for the integrated cases, it has been a reference point between the feet, human/suit system. which allows the incorporation of suit flexibility in reduced or microgravity. These test traditionally involve the use In a sense, this paper really presents a vision of an of neutral buoyancy or parabolic flight, and are therefore integrated system for suit instrumentation, testing, and indicative of microgravity. There are no known full-body evaluation that is compatible with neutral byoyancy, reach envelopes for partial gravity, such as lunar or field trials, and even flight evaluations of advanced Mars conditions. suits. In many cases, examples will be drawn from past and present research projects of the University of Traditional reach envelope testing of pressure suits has Maryland Space Systems Laboratory. These sample been performed in the laboratory (1 g) environment. systems presented range from concepts, to This was traditionally performed with manual breadboarded systems used for proof-of-concept testing, photogrammetry or goniometers, but has lately been to highly developed systems already used for advanced upgraded to automatic photogrammetric analysis. research. In no case will this paper go into the detailed Electromagnetic position sensors also function well in results of any of these individual component this controlled environment. technologies; rather, this paper will focus on developing a set of useful components for an integrated suit Technologies applicable to this category of metrics evaluation system, and will describe how all the include: components may be brought together to create a useful • Accurate automatic position sensing synthesis of performance metrics. • Whole-body partial gravity simulation • Limb pose measurement DESIRABLE EVALUATION METRICS FOR • Standardized dexterity tests SUIT OPERATIONS MOBILITY METRICS When a current space suit reaches integrated test status, the primary focus is on getting experienced While reach envelopes measure the crew's capability to subjects into the suit, and having them perform tests span distances from a fixed point, overall work station which correlate to prior experience. This approach is design relies on the ability to translate from task location adequate for qualitative evaluation of design changes, to location. This translation task frequently is the largest but does not provide a full quantitative insight into the "mass handling" task of the EVA, and suits which effects of suit design modifications. What, then, are the facilitate this type of motion convey an advantage for metrics which need to be included to provide a more the wearer. Looking at the problem in the other direction, EVA timelines which reduce the requirement for the • Environmentally compatible force-torque sensors crew to manipulate their own body positions free up • Suit-compatible low-profile wearable pressure or time to perform the required tasks. However, there has force sensors been little means of measuring body motion other than coarse inference from the work station design. PHYSIOLOGICAL WORKLOAD MEASUREMENTS A system which can monitor the subjects body motion in all six dimensions (three translational and three rotational) could provide much finer-scale data on Ultimately, the true measure of any pressure suit is the mobility as a component of operational tasks. This physiological stress it places on its wearer; that is, the would aid in refining work site design protocols. It would extent to which the EVA crew expends energy in moving also provide sufficient data for direct calculation of crew the suit rather than performing the assigned task. A energy which is expended in body motions, which will common tool in physiology laboratories are help to obtain more accurate energy estimates of the measurement systems for metabolic workload, actual task operations. particularly oxygen uptake (VO2) systems. This capability has been incorporated into pressure suits for Technologies applicable to this metric include: flight EVA measurements, but has never been routinely available for neutral buoyancy or other ground-based • Automated six-axis
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