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At least 217 records · Page 12

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NASA NTRS1971

Altered susceptibility to motion sickness as a function of subgravity level

Large interindividual differences among 74 normal subjects in the change in susceptibility to motion sickness with effective lifting of the normal g-load by parabolic flight maneuvers were recorded with high test-retest reliability. Most subjects, who were required to make standardized head movements while seated in a chair rotating at a constant speed, demonstrated either a substantial increase or a decrease in susceptibility, in confirmation of a previous study, while a few appeared to be more or less unaffected by the 1 g to 0 g gravitational change. A similar test procedure conducted with eighteen of the subjects at lunar- and Martian-gravity levels revealed further interindividual differences in susceptiblity as a function of g-level. The subjects with gravity-dependent susceptibility revealed: (1) a progressive change in susceptibility as a function of g-load in either the positive or negative direction that was characteristic of the individual, (2) a susceptibility level that appeared to be maintained at the fractional g-load, and (3) immunity to motion sickness at all g-levels tested below the earth standard. The case history as well as ground-based functional and provocative tests of normal subjects proved to be inadequate in predicting susceptibility to motion sickness under subgravity conditions.

Miller, E. F., II↗

NASA NTRS1973

Altered susceptibility to motion sickness as a function of subgravity level.

Miller, E. F., II↗

NASA NTRS1973

Human eye movements during various forms of linear acceleration and weightlessness

Eye movements of human subjects were recorded electronystagmographically in complete darkness during rectilinear horizontal accelerations as achieved in cars on the ground and also during aircraft parabolic flight. The results were compared to the movements of blinded goldfish subjected to similar changes of gravitoinertial forces. The results indicate that there is a human correlation with the gravity reference response of fish. During horizontal forward accelerations on the ground the human eyes turn downward and during horizontal backward acceleration the eyes turn upward. The human eye response to g-loads below 1 g and to weightlessness is the reverse of the tilt of the fish. While fish dive down during low g, or loop forward during weightlessness, the eyes of subjects sitting upright in an aircraft which flies at 0 g move upward.

Vonbaumgarten, R. J.↗

NASA NTRS1975

Static-kinetic reactions of man under conditions of brief weightlessness

Physical characteristics of human responses to weightlessness simulation during parabolic flights establish body immobilization and visual illusions as the most manifest causes of sensory distrubances. Repeated brief weightlessness exposures gradually decreased expressions of static-kinetic disorders.

Kolosov, I. A.↗

NASA NTRS1975

Motor activity of astronauts in unsupported state

The performance quality of movements away and approaches to an airlock by astronauts was tested during parabolic flights for weightlessness simulation. Coordination of movement, orientation and performance capacity of the astronauts were not singificantly disrupted. Observed physiological shifts are characterized by an increase in pulse and respiration rate and an increase in arterial pressure under g-forces, a gradual decrease in these indices during repeated stays in weightlessness or during the prolonged effect of it, by a reduction of the length of postrotational nystagmus and counterrotation illusions under weightless conditions.

Kasyan, I. I.↗

NASA NTRS1974

Susceptibility to motion sickness among Skylab astronauts

The mechanisms causing susceptibility to motion sickness in zero gravity are not well understood. Preflight and postflight motion sickness susceptibility tests conducted on the three Skylab crews are described. Under operational conditions, the first Skylab crew experienced no motion sickness, while the other two crews did. Susceptibility was greater in the Skylab workshop than in the command module. Weightlessness in itself is a unique motion environment. Changes occur in nonrigid body parts and in the response of macular receptors in the otolith organs. Tests in parabolic flight, where zero gravity is the only significant factor in motion sickness susceptibility, indicate that some people need to adapt to weightlessness and others do not. A comparison of all US and Soviet manned missions indicates that a headward shift of fluid on transition to zero gravity is not a predisposing factor in motion sickness. Under certain conditions after adaptation susceptibility was lower in the Skylab workshop than on the ground. The anti-motion sickness drugs used in Skylab are judged effective for prevention and treatment.

Graybiel, A.↗

NASA NTRS1975

Effects of prolonged weightlessness on the swimming pattern of fish aboard Skylab 3

Looping behavior of minnows aboard Skylab 3 is analyzed. Extensive looping patterns were observed at first look on the third day of weightlessness; thereafter, the frequency of the looping episodes diminished until complete adaptation on the twenty-first day, at which time the fish oriented themselves with their backs to the light. The swimming anomaly could be due to (1) absence of continuous bending of sense hairs to a certain extent by gravity, causing the fish to tilt forward in an attempt to increase leverage on the hairs - in the absence of all gravity, tilting is continued into looping (this hypothesis is supported by parabolic flight experiments with partial gravity, in which only tilting was seen); or (2) an attempt by the fish to create a gravitoinertial stimulus by 'centrifuging' its otoliths by looping.

Von Baumgarten, R. J.↗

NASA NTRS1979

Prevention and treatment of space sickness in Shuttle-Orbiter missions

A status report is presented on assessments of antimotion sickness drugs in slow-rotation rooms and, particularly, with two candidate medications - fixed-dose combinations of promethazine plus ephedrine and a transdermal therapeutic system-scopalamine - that are efficacious over long periods with acceptable side effects. Attention is given to evaluating the use of free fall in parabolic flight as a model for orbital flight to assess the efficacy of antimotion sickness drugs. Experience in slow-rotation rooms suggests that programming adaptation (executing head movements) is significantly superior to random head movements when performing required tasks.

Graybiel, A.↗

NASA NTRS1980

Free fall - A partial unique motion environment

Conditions leading to the elicitation of motion sickness have been divided into two main categories: partial motion environments, in which head movements are required to elicit motion sickness, and complete motion environments, in which independent movements of the head are not required for the production of symptoms. It is postulated that, according to this categorization, free fall constitutes a partial motion environment. In support of this hypothesis evidence is reviewed from Skylab missions, experiments in parabolic flight, and ground-based studies.

Graybiel, A.↗

NASA NTRS1980

Fluid mechanics and solidification investigations in low-gravity environments

Fluid mechanics of gases and liquids and solidification processes were investigated under microgravity conditions during Skylab and Apollo-Soyuz missions. Electromagnetic, acoustic, and aerodynamic levitation devices, drop tubes, aircraft parabolic flight trajectories, and vertical sounding rockets were developed for low-g simulation. The Spacelab 3 mission will be carried out in a gravity gradient flight attitude; analyses of sources of vehicle dynamic accelerations with associated g-levels and angular rates will produce results for future specific experiments.

Fichtl, G. H.↗

NASA NTRS1981

Variations in gravitoinertial force level affect the gain of the vestibulo-ocular reflex - Implications of the etiology of space motion sickness

Recordings of horizontal nystagmus were obtained on 16 male subjects exposed to repeated patterns of horizontal angular acceleration, constant velocity rotation, and sudden-stop deceleration in the laboratory and in the free-fall and high-force periods of parabolic flight. Nystagmus intensity was a clear function of gravitoinertial force level: slow phase velocity and beat frequency increased during exposure to high force levels and decreased in free-fall compared to values obtained at 1 G. These findings indicate that the gain of the vestibulo-ocular reflex decreases in free-fall. This fact likely accounts for the disorientation and dizziness sometimes experienced by astronauts when moving their heads in the early phases of orbital flight and again after splashdown. The implications of the present findings, both for the etiology and for the treatment of space motion sickness, are discussed.

Lackner, J. R.↗

NASA NTRS1981

Ocular torsion on earth and in weightlessness

Otolith function is studied by means of measurements of ocular torsion under various acceleration environments on earth and in weightlessness. Photographic measurements of ocular torsion as indicated by the rotation of landmarks on the iris with respect to head-fixed fiducial marks were obtained in subjects undergoing horizontal linear acceleration in a ground-based version of the space sled, lateral acceleration from weightlessness during pullout from the free-fall portion of parabolic flight, and optokinetic stimulation about the roll axis in the supine position in the laboratory and during weightlessness. The responses of ocular torsion to horizontal acceleration are in agreement with a simple low-order linear system with a dominant time constant of 0.33 sec, with a transfer function fit by a model with a pure delay of 0 to 400 msec and a first-order lag. In the pullout experiment, torsion was not observed in response to the onset of acceleration in the right-ear-down position, although it was present in response to the lateral stimulus. Results of the roll vection experiments indicate the independence of ocular torsion and visually induced tilt. In addition, an automatic video system using a soft contact lens target is presented which has been developed for ocular torsion measurements.

Young, L. R.↗

NASA NTRS1982

Mass estimation and discrimination during brief periods of zero gravity

Under zero gravity, the gravitational cues to mass are removed, but the inertial cues remain. A sensation of heaviness is generated if objects are shaken, and hence given a changing acceleration. A magnitude estimation experiment was conducted during the 0-G phase of parabolic flight and on the ground, and the results suggested that objects felt lighter under 0 G than under 1 G. Mass discrimination was also measured in flight, and yielded Weber fractions of .18 under 0 G, .16 under 1.8 G, and .09 under 1 G. Poor performance under microgravity and macrogravity was probably due mainly to lack of time for adaptation to changed G levels. It is predicted that discrimination should improve during the course of prolonged spaceflight, and that there should be an aftereffect of poor discrimination on return to earth.

Ross, H. E.↗

NASA NTRS1982

Rapid perceptual adaptation to high gravitoinertial force levels Evidence for context-specific adaptation

Subjects exposed to periodic variations in gravitoinertial force (2-G peak) in parabolic flight maneuvers quickly come to perceive the peak force level as having decreased in intensity. By the end of a 40-parabola flight, the decrease in apparent force is approximately 40%. On successive flight days, the apparent intensity of the force loads seems to decrease as well, indicating a cumulative adaptive effect. None of the subjects reported feeling abnormally 'light' for more than a minute or two after return to 1-G background force levels. The pattern of findings suggests a context-specific adaptation to high-force levels.

Lackner, J. R.↗

NASA NTRS1983

Motion sickness - Acquisition and retention of adaptation effects compared in three motion environments

The acquisition and retention of adaptation effects in motion sickness was invetigated using a sudden-stop vestibulovisual interaction test for measuring susceptibility to motion sickness (Graybiel and Lackner, 1980). The test procedure included four successive assessments that provide not only an index of susceptibility to motion sickness but also the rates of acquisition and decay of adaptation effects. The 14 subjects who had participated in this test had previously served as subjects in parabolic flight experiments and seven of them had also taken part in the assessment of antimotion-sickness remedies in a slow rotation room. A study was conducted to determine whether these subjects' rates of acquisition and decay of adaptation to stressful motion represent consistent general features of their response across motion environments. It is found that an individual's rates of acquiring and losing adaptation are quite consistent in very different situations. In addition, the pattern of results indicate modifications of the sudden-stop vestibulovisual test that should increase its effectiveness as a motion-sickness screening procedure, both for orbital flight and for terrestrial conditions.

Graybiel, A.↗

NASA NTRS1983

Etiological factors in space motion sickness

The human susceptibility to motion sickness during exposure to sudden-stop stimulation as a function of gravitoinertial force level is studied. It is determined that susceptibility is greatly enhanced, both with eyes-closed and eyes-open, for zero-g and 2-g conditions in parabolic flight compared with 1-g test conditions. It is argued that this change in susceptibility is related to alterations in vestibulo-occular function which result from variations in gravitoinertial force level, the altered patterns of otolithic activity resulting during variations in gravitoinertial force level, and the altered canal-otolith response synergies that result during exposure to gravitoinertial force levels greater or less than terrestrial levels. These factors are found to be related to the etiology of space motion sickness and to the alterations in performance and vestibular function that are experienced by astronauts during reentry. An explanation is presented for the decrease in susceptibility to motion sickness exhibited by the Skylab astronauts inflight and for some period postflight during exposure to cross-coupled angular accelerations.

Lackner, J. R.↗

NASA NTRS1984

Development of the sonic pump levitation

A prototype levitating/positioning device termed the Sonic Pump Levitator was designed, built and successfully tested in full gravity and in the reduced gravity of the parabolic flight regime of the KC-135. Positioning is achieved by timely and appropriate application of gas momentum from one or more of six sonic pumps. The sonic pumps, which are arranged orthogonally in opposed pairs about the levitation region, are activated by an electro-optical, computer controlled, feedback system. The sonic pump is a transducer which is capable of converting sound energy into a directed flow of gas. It consists of a loudspeaker whose face is sealed by a closure perforated by one or more orifices. The diaphragm of the loudspeaker is the only moving part of the sonic pump, no valves being needed. This very low inertia electromechanical device was developed to provide the short response time necessary to keep pace with the demands of computerized position keeping.

Dunn, S. A.↗

NASA NTRS1984

Zero-g experiments with a He II active phase separator for space application

An active phase separator (APS) for temperature control of He II space cooling systems was tested in a zero-g environment during a series of parabolic flights on a NASA KC 135 aircraft. The APS provides for liquid-gas separation and features an annular gap, a downstream heat exchanger and an upstream ball closure. The apparatus was operated during acceleration and floating and in two different heat load situations. The tests confirmed that adequate mass flow rates could be maintained using a vacuum pump to simulate space vacuum and that residual liquid could be evaporated from the heat exchanger after closing a ball valve to seal off flows.

Denner, H. D.↗