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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Effect of Varying HUT Sizing on Human-Spacesuit Contact Patterns

Fit, comfort, and mobility of the spacesuit rely on the location, magnitude, and type of contact between the suit and wearer. Typically, spacesuits include the Hard Upper Torso (HUT) comprising the upper torso of the spacesuit. Potential injuries from hard contact between the wearer’s shoulders and the HUT are a concern; therefore, to investigate spacesuit-wearer contact patterns, data from a retrospective study was analyzed. This study had eight subjects wearing the Shuttle Extravehicular Mobility Unit (EMU) spacesuit in two configurations, one with a nominally sized HUT and another with an oversized HUT. The subjects were sized per the NASA standard suit fit procedure. The suit’s arms and lower body were also resized to provide nominal arm and lower body fit, accounting for the larger HUT. Subjects held various shoulder postures (neutral posture, and various maximum shoulder rotations) with the suit pressurized to 4.3 PSI. For each posture, subjects reported the intensity of their perceived contact with the suit on a Borg CR10 scale, 0 indicating a non-existent contact intensity, and 10 representing a maximal contact intensity. Ratings were recorded for 11 regions covering the upper body and these ratings were used to determine the impact of body shape and size on suit contact. Our preliminary findings suggest that oversized HUTs had less contact regions than compared to the nominal HUT; and the region of contact, contact patterns, and contact intensities varied from person to person with the oversized HUT. This variance could be linked to subjects’ body shape and size. The next goal is to establish a causal factor between body shape and size, pose, contact region, and the HUT size. The outcome is expected to help understand the overall contact trends and insights into the influence of HUT sizing on suit fit.

Will Green↗
NASA NTRS2024

3D Scanning System to Assess Gravity-Dependent Body Shape Changes

The human body shows unique physiological and morphological changes when exposed to different gravity conditions, including muscle atrophy, fluid shift, spinal elongation, and body posture adjustments. Such changes need to be incorporated for human-system integration in the vehicle habitat, garment, and spacesuit designs, as inaccurate body measurements can result in suboptimal crew protection that can potentially decrease injury tolerance. However, the traditional linear measurements, such as stature, segment lengths or circumferences measured using a caliper or tape measure, often show limited consistency and are unable to capture the nonlinear characteristics of the human body. While 3D body scanning can provide significant advantages over linear measurements, the technologies have not been fully developed or customized for in-flight scanning. For ground laboratory use, several different scanner types are commercially available. However, in-flight scanning requires additional technical considerations, such as minimal scan time, simplified calibration, and sufficient capture volume. This work aims to develop a prototype 3-D body scanning system that is customized for in-flight use to scan crewmembers, with the configuration and performance optimized for detecting known gravity-dependent body shape and posture changes. A hardware system will be custom built using a network of commercial off-the-shelf 3D sensors. The sensor parameters and settings will be optimized to detect the targeted body shape changes, specifically using body manikins of which the shape and size are iteratively permuted to simulate the known changes by fluid shift and spinal elongation. The capture volume will be also matched for a range of body sizes from a 1st percentile female to 99th percentile male. Unintentional body motions or floating in microgravity will be also simulated and incorporated. A data acquisition software will be developed for efficient in-flight operations with minimal overhead and easy-to-use user interface. A simplified calibration procedure will be designed for robust scanning against frequent vibration or unexpected sensor position shifts. The system will be tested in the ground laboratory for accuracy and reliability against a reference scanning system. New anthropometry measurements will be also identified to sensitively capture the gravity dependent body shape changes, in addition to the traditional anthropometry measurements. A novel landmark-based technique will be tested for consistent anthropometry measurements across posture variations. If successfully developed and deployed, the new system is expected to provide previously unavailable body shape and size data from different gravitational environments, including 0-g, 1/6-g, and 1-g. Such data can improve suit fit, habitat design, exercise efficacy quantification and sizing of orthostatic intolerance garments.

K H Kim↗
NASA NTRS2000

Influence of central set on anticipatory and triggered grip-force adjustments

The effects of predictability of load magnitude on anticipatory and triggered grip-force adjustments were studied as nine normal subjects used a precision grip to lift, hold, and replace an instrumented test object. Experience with a predictable stimulus has been shown to enhance magnitude scaling of triggered postural responses to different amplitudes of perturbations. However, this phenomenon, known as a central-set effect, has not been tested systematically for grip-force responses in the hand. In our study, predictability was manipulated by applying load perturbations of different magnitudes to the test object under conditions in which the upcoming load magnitude was presented repeatedly or under conditions in which the load magnitudes were presented randomly, each with two different pre-load grip conditions (unconstrained and constrained). In constrained conditions, initial grip forces were maintained near the minimum level necessary to prevent pre-loaded object slippage, while in unconstrained conditions, no initial grip force restrictions were imposed. The effect of predictable (blocked) and unpredictable (random) load presentations on scaling of anticipatory and triggered grip responses was tested by comparing the slopes of linear regressions between the imposed load and grip response magnitude. Anticipatory and triggered grip force responses were scaled to load magnitude in all conditions. However, regardless of pre-load grip force constraint, the gains (slopes) of grip responses relative to load magnitudes were greater when the magnitude of the upcoming load was predictable than when the load increase was unpredictable. In addition, a central-set effect was evidenced by the fewer number of drop trials in the predictable relative to unpredictable load conditions. Pre-load grip forces showed the greatest set effects. However, grip responses showed larger set effects, based on prediction, when pre-load grip force was constrained to lower levels. These results suggest that anticipatory processes pertaining to load magnitude permit the response gain of both voluntary and triggered rapid grip force adjustments to be set, at least partially, prior to perturbation onset. Comparison of anticipatory set effects for reactive torque and lower extremity EMG postural responses triggered by surface translation perturbations suggests a more general rule governing anticipatory processes.

Non-NASA Center↗
NASA NTRS1998

Relation of blood volume and blood pressure in orthostatic intolerance

A complex but crucial relationship exists between blood volume and blood pressure in human subjects; it has been recognized that in essential hypertension, renovascular hypertension, and pheochromocytoma, the relationship between plasma volume and diastolic blood pressure is an inverse one. This phenomenon has not been studied in individuals with low normal and reduced blood pressures. Orthostatic intolerance is a commonly encountered abnormality in blood pressure regulation often associated with tachycardia in the standing position. Most of these patients have varying degrees of reduced blood volume. We tested the hypothesis that the relationship previously found between plasma volume and diastolic blood pressure in pressor states would also hold in orthostatic intolerance. We studied 16 patients with a history of symptomatic orthostatic intolerance associated with an elevation in plasma norepinephrine in the upright posture and hypovolemia in 9 patients and normovolemia in 7 patients. Our studies demonstrate an inverse relationship between plasma volume and diastolic blood pressure in patients with orthostatic intolerance. This finding also holds for the change in diastolic blood pressure in response to upright posture. In this relationship, patients with orthostatic intolerance with high plasma norepinephrine resemble those with essential hypertension, renovascular hypertension, and pheochromocytoma. We conclude that in a variety of conditions at both ends of the blood pressure spectrum, the seemingly paradoxical association of hypovolemia and diastolic blood pressure is preserved.

NASA Discipline Regulatory Physiology↗
NASA NTRS1993

Effect of upright tilt on ventricular/vascular coupling in chronically instrumented primates

Studies of the hydraulic loading conditions on the heart in humans, especially pulsatile load, have primarily been limited to the supine state. Therefore, we have chosen a nonhuman primate model, the baboon, to assess left ventricular/vascular coupling in both supine and upright positions. Primate subjects were studied by catheterization under sedation and then after surgical implantation of transducers. This allowed the evaluation of postural stress in the chronically instrumented conscious baboon and then after light dissociative doses of ketamine. Basic hemodynamic variables were evaluated for baboons in supine and upright positions. Fourier analysis was applied to aortic pressure and flow to obtain input and characteristic impedance and the ratio of pulsatile (Wp) to total (Wt) left ventricular power (Wp/Wt). The aortic reflected, or backward, pressure was also calculated. Peripheral resistance increased (P = 0.01) and reflected pressure decreased (17.74 +/- 1.50 vs. 15.21 +/- 2 mmHg; P < 0.01) in upright subjects. Characteristic impedance and Wp/Wt were unchanged. Postoperatively, peripheral resistance increased (2,651 +/- 311 vs. 3,667 +/- 276; P < 0.05) and mean power and Wt decreased (P < 0.01) without changes in reflected pressure. All variables were unchanged after light dissociative doses of ketamine. Thus there is no significant change in efficiency of left ventricular/vascular coupling formulated in terms of Wp/Wt or input impedance with postural stress.

NASA Program Space Physiology and Countermeasures↗
NASA NTRSDate not supplied

Implementing an Objectives-Driven, Risk-Informed, and Case-Assured Approach to Safety and Mission Success at NASA

NASA is developing a “Standard for Assurance of Space Flight Safety and Mission Success” that implements an objectives-driven, risk-informed, and case-assured approach to safety and mission success (S&MS) for NASA space flight programs and projects. The standard aligns with the philosophy of risk leadership that has recently been established in NASA policy to assure acceptable levels of flight crew safety and mission success risk. It is consistent with existing NASA risk management requirements and is compatible with NASA program management and systems engineering requirements. The methodology described in the standard is presented in terms of an S&MS assurance framework that is designed to allow substantial flexibility in the specific means by which programs and projects achieve acceptable mission S&MS risk. Such flexibility is necessary to accommodate the increasingly broad range of acquisition strategies employed by NASA, including commercial transportation services, as well as to accommodate the increasingly rapid evolution of space flight-related technologies and practices. A key feature of the S&MS assurance framework is the specification of S&MS success criteria for each life-cycle review (LCR). The S&MS assurance case is structured around these criteria, the satisfaction of which indicates that the program/project is adhering to the S&MS risk posture. This enables the evolving S&MS assurance case to be used as a fundamental program/project submittal at each LCR, where its inherent structure of argument, supported by evidence, directly supports the evaluation of the program/project with respect to the S&MS success criteria, and by extension, the S&MS risk posture. As such, the S&MS assurance case is integral to program/project systems engineering, risk management, and S&MS oversight activities, and provides the principal basis for S&MS risk acceptance by the Decision Authority throughout the program/project life cycle.

Risk Posture↗
NASA NTRS1971

A model describing vestibular detection of body sway motion.

An experimental technique was developed which facilitated the formulation of a quantitative model describing vestibular detection of body sway motion in a postural response mode. All cues, except vestibular ones, which gave a subject an indication that he was beginning to sway, were eliminated using a specially designed two-degree-of-freedom platform; body sway was then induced and resulting compensatory responses at the ankle joints measured. Hybrid simulation compared the experimental results with models of the semicircular canals and utricular otolith receptors. Dynamic characteristics of the resulting canal model compared closely with characteristics of models which describe eye movement and subjective responses to body rotational motions. The average threshold level, in the postural response mode, however, was considerably lower. Analysis indicated that the otoliths probably play no role in the initial detection of body sway motion.

Nashner, L. M.↗
NASA NTRS1972

Effects of simulated artificial gravity on human performance

The ability of test subjects to perform operational type tasks was evaluated at rotational rates to 6 rpm and radii to 78 ft (24 m). The tasks included fine motor activity, mental operations, postural equilibrium, cargo handling, radial and tangential locomotion. Performance data indicate that 6 rpm presents a physiological limit at radii to 75 ft (23 m). Radial locomotion was not found to produce excessive adverse stimuli, and tangential locomotion was readily accomplished at walking rates of 2 of 4.8 ft/s (.6 to 1.4 m/s). The absence of vision dramatically reduced an individual's postural equilibrium during rotation. The use of selected anti-motion pharmaceuticals had, generally, a positive effect upon psychomotor performance at 6 rpm, but did not prove to be a panacea for the adverse effects of rotation at this rate.

Green, J. A.↗
NASA NTRS1975

Hemodynamics, renal function, plasma renin, and aldosterone in man after 5 to 14 days of bedrest

Continuous bedrest for 5 to 14 days had no significant effect on resting heart rate, blood pressure, or cardiac output in six normal men. Head-up tilt induced greater tachycardia in 5 of 6 patients after bed rest than in the control period. Propranolol diminished both tachycardia and the incidence of hypotension and faintness in upright posture. Plasma volume fell, extracellular fluid volume increased, and plasma renin activity was significantly elevated following bedrest. Unusually large increases in plasma renin followed head-up tilt or administration of isoproterenol during bedrest and after resuming normal activity. During bedrest, plasma aldosterone was often increased in the early morning. It is concluded that after bedrest, upright posture evokes strong beta-adrenergic activity as well as exaggerated metabolic and circulatory responses which can be reduced or abolished by the beta-adrenergic blocker, propranolol.

Melada, G. A.↗
NASA NTRS1978

Some influences of touch and pressure cues on human spatial orientation

In order to evaluate the influences of touch and pressure cues on human spatial orientation, blindfolded subjects were exposed to 30 rmp rotation about the Z-axis of their bodies while the axis was horizontal or near horizontal. It was found that the manipulation of pressure patterns to which the subjects are exposed significantly influences apparent orientation. When provided with visual information about actual orientation the subjects will eliminate the postural illusions created by pressure-cue patterns. The localization of sounds is dependent of the apparent orientation and the actual pattern of auditory stimulation. The study provides a basis for investigating: (1) the postural illusions experienced by astronauts in orbital flight and subjects in the free-fall phase of parabolic flight, and (2) the spatial-constancy mechanisms distinguishing changes in sensory afflux conditioned by a subject's movements in relation to the environment, and those conditioned by movements of the environment.

Lackner, J. R.↗
NASA NTRS1979

Man and machine design for space flight

The factors involved in creating effective designs for living and working in a weightless environment are discussed. Among the areas covered are special provisions for eating and drinking, a special shower nozzle to remove soap, electric shavers designed for vacuum containment of the clippings, and the need for restraint systems at the crew's workstations. Attention is given to the fact that the crewmen assume a neutral body posture in weightlessness which is an important consideration in designing displays, controls, and windows. It is concluded that the incorporation of the change in body posture and the requirement for restraint into future designs will greatly facilitate the crewman's task in the weightless environment.

Louviere, A. J.↗
NASA NTRS1981

Decision Aids for Airborne Intercept Operations in Advanced Aircrafts

A tactical decision aid (TDA) for the F-14 aircrew, i.e., the naval flight officer and pilot, in conducting a multitarget attack during the performance of a Combat Air Patrol (CAP) role is presented. The TDA employs hierarchical multiattribute utility models for characterizing mission objectives in operationally measurable terms, rule based AI-models for tactical posture selection, and fast time simulation for maneuver consequence prediction. The TDA makes aspect maneuver recommendations, selects and displays the optimum mission posture, evaluates attackable and potentially attackable subsets, and recommends the 'best' attackable subset along with the required course perturbation.

Madni, A.↗
NASA NTRS1982

Dehydration-induced drinking in humans

The human tendency to experience a delay in rehydration (involuntary dehydration) after fluid loss is considered. The two primary factors contributing to involuntary dehydration are probably upright posture, and extracellular fluid and electrolyte loss by sweating from exercise and heat exposure. First, as the plasma sodium and osmotic concentrations remain virtually unchanged for supine to upright postural changes, the major stimuli for drinking appear to be associated with the hypovolemia and increase in the renin-angiotension system. Second, voluntary drinking during the heat experiments was 146% greater than in cool experiments; drinking increased by 109% with prior dehydration as opposed to normal hydration conditions; and drinking was increased by 41% after exercise as compared with the resting condition. Finally, it is concluded that the rate of sweating and the rate of voluntary fluid intake are highly correlated, and that the dispogenic factors of plasma volume, osmolality, and plasma renin activity are unrelated to sweat rate, but are likely to induce drinking in humans.

Greenleaf, J. E.↗
NASA NTRS1986

Regulation of hematopoiesis in rats exposed to antiorthostatic hypokinetic/hypodynamia. II - Mechanisms of the 'anemia'

The cause of the red cell mass (RCM) deficit, which occurs in rats during suspenion, is investigated. The experimental conditions and procedures, in which male Sprague-Dawley rats are subjected to antiorthostatic hyypokinetic/hypodynamia and changes in RCM are monitored, are described. The influences of stress, reduced food and water consumption, and antiorhostatic posture on RCM are analyzed. Changes in body weight, RCM, radioiron incorporation, red blood cells (RBC), and reticulocytes, for the rats after head-down suspension are graphically presented; only the changes in RBC are related to the antiorthostatic posture. The data reveal that anemia is primarily caused by reduced food and water consumption and secondly by restricted movements.

Dunn, C. D. R.↗
NASA NTRS1987

Leadership and America's future in space

In response to growing concern over the posture and long-term direction of the U.S. civilian space program, a task group was formed to define potential U.S. space initiatives, and to evaluate them in light of the current space program and the nation's desire to regain and retain space leadership. The objectives were to energize a discussion of the long-term goals of the civilian space program and to begin to investigate overall strategies to direct that program to a position of leadership. Four initiatives were identified: mission to planet Earth; exploration of the solar system; outpost on the Moon, and humans to Mars. All four initiatives were developed in detail, and the implications and requirements of each was assessed. The long-term goals, current posturing required to attain these goals, and the need for a continuing process to define, refine, and assess both the goals and the strategy to achieve them are discussed.

Sally K Ride↗
NASA NTRS1987

Effects of hypokinesia and hypodynamia upon protein turnover in hindlimb muscles of the rat

Hypokinesia/hypodynamia was induced in the hindlimb muscles of the rat, using a suspension technique. This caused differing degrees of atrophy in different muscles. However, this atrophy was reduced in muscles held in a lenghthened position. The greatest degree of wasting was observed in the unstretched soleus, a slow postural muscle, where both Type 1 and Type 2a fibers atrophied to the same degree. However, wasting of the gastrocnemius muscle was associated with a reduction in the size of the Type 2b fibers. In both slow-postural and fast-phasic hindlimb muscles, atrophy was brought about by a reduction in the rate of protein synthesis in conjunction with an elevation in the rate of protein degradation. When inactive muscles were passively stretched, both protein synthesis and degradation were dramatically elevated. Even periods of stretch of as little as 0.5 h/d were found to significantly decrease atrophy in inactive muscles.

Loughna, Paul T.↗
NASA NTRS1988

Vestibular reflexes of otolith origin

The vestibular system and its role in the maintenance of posture and in motion sickness is investigated using cats as experimental subjects. The assumption is that better understanding of the physiology of vestibular pathways is not only of intrinsic value, but will help to explain and eventually alleviate the disturbances caused by vestibular malfunction, or by exposure to an unusual environment such as space. The first project deals with the influence on the spinal cord of stimulation of the vestibular labyrinth, particularly the otoliths. A second was concerned with the properties and neural basis of the tonic neck reflex. These two projects are related, because vestibulospinal and tonic neck reflexes interact in the maintenance of normal posture. The third project began with an interest in mechanisms of motion sickness, and eventually shifted to a study of central control of respiratory muscles involved in vomiting.

Wilson, Victor J.↗