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At least 1,693 records · Page 94Linked to original sources
PubMed1989

Moments applied in the manual assembly of space structures: EASE biomechanics results from STS-61B.

Measurements of the level and pattern of moments applied in the manual assembly of a space structure were made in extravehicular activity (EVA) and neutral buoyancy simulation (NBS). The Experimental Assembly of Structures in EVA program included the repeated assembly of a 3.6 m tetrahedral truss structure in EVA on STS-61B after extensive neutral buoyancy crew training. The flight and training structures were of equivalent mass and geometry to allow a direct correlation between EVA and NBS performance. A stereo photographic motion camera system was used to reconstruct in three dimensions rotational movements of structural beams during assembly. Moments applied in these manual handling tasks were calculated on the basis of the reconstructed movements taking into account effects of inertia, drag and virtual mass. Applied moments of 2.0 Nm were typical for beam rotations in EVA. Corresponding applied moments in NBS were typically up to five times greater. Moments were applied as impulses separated by several seconds of coasting in both EVA and NBS. Decelerating impulses were only infrequently observed in NBS.

Algorithms↗
PubMedDate not supplied

Evaluation of safety of hypobaric decompressions and EVA from positions of probabilistic theory.

Formation and subsequent evolution of gas bubbles in blood and tissues of subjects exposed to decompression are casual processes in their nature. Such character of bubbling processes in a body predetermines probabilistic character of decompression sickness (DCS) incidence in divers, aviators and astronauts. Our original probabilistic theory of decompression safety is based on stochastic models of these processes and on the concept of critical volume of a free gas phase in body tissues. From positions of this theory, the probability of DCS incidence during single-stage decompressions and during hypobaric decompressions under EVA in particular, is defined by the distribution of possible values of nucleation efficiency in "pain" tissues and by its critical significance depended on the parameters of a concrete decompression. In the present study the following is shown: 1) the dimensionless index of critical nucleation efficiency for "pain" body tissues is a more adequate index of decompression stress in comparison with Tissue Ratio, TR; 2) a priory the decompression under EVA performed according to the Russian protocol is more safe than decompression under EVA performed in accordance with the U.S. protocol; 3) the Russian space suit operated at a higher pressure and having a higher "rigidity" induces a stronger inhibition of mechanisms of cavitation and gas bubbles formation in tissues of a subject located in it, and by that provides a more considerable reduction of the DCS risk during real EVA performance.

Aerospace Medicine↗
PubMed1997

Frog experiment onboard space station Mir.

Japanese tree frogs (Hyla japonica) showed unique postures and behavior during an 8-day flight to the Russian space station Mir. When floating in the air, the animals arched their back and extended their four limbs. This posture resembles that observed during jumping or parachuting of the animals on the ground. Frog sitting on a surface bent their neck backward sharply, did not fold their hind limbs completely, and pressed their abdomen against the substrate. They walked backwards in this posture. The typical posture resembles that adopted during the emetic behavior process on the ground, although the posture in space lasts much longer. The possible mechanism of induction of this unique posture in orbit is discussed. Frogs in this posture might be in an emetic state, possibly due to motion sickness. Response behavior to some stimuli was observed in orbit. Body color change in response to the background color appeared to be delayed or slowed down. Response behavior to other stimuli showed little change as long as the animal maintained contact with a substrate. Once it left the surface, the floating frog could not control its movements so as to provide coordinated motility for locomotion and orientation. Adaptation to microgravity was observed in the landing behavior after jumping. Readaptation of the frogs to the Earth environment took place within a few hours after return. Postflight histological and biochemical analysis of organs and tissues showed some changes after the 8-day spaceflight. Weakening and density loss in vertebrae was noted. The beta-adrenoreceptor activity of the gastrocnemius was natriuretic decreased. Skin collagen and liver protein synthesis were lowered. The distribution of the atrial factor-like peptides in the brain was changed.

Adaptation, Physiological↗
PubMed1997

Evidence for increased beta-adrenoreceptor responsiveness induced by 14 days of simulated microgravity in humans.

We studied hemodynamic responses to alpha- and beta-receptor agonists in eight healthy men before and after 14 days of 6 degrees head-down tilt (HDT) to test the hypothesis that increased adrenoreceptor responsiveness is induced by prolonged exposure to simulated microgravity. Steady-state infusions of isoproterenol (Iso) at rates of 0.005, 0.01, and 0.02 microgram.kg-1.min-1 were used to assess beta 1- and beta 2-adrenoreceptor responsiveness. Infusions of phenylephrine (PE) at rates of 0.25, 0.50, and 1.00 microgram.kg-1.min-1 were used to assess responsiveness of alpha 1-vascular adrenoreceptors. Slopes calculated from linear regressions between Iso and PE doses and changes in beat-to-beat heart rate, blood pressure, and leg vascular resistance (occlusion plethysmography) for each subject were used as an index of alpha- and beta-adrenoreceptor responsiveness. HDT increased the slopes of heart rate (1,056 +/- 107 to 1,553 +/- 83 beats micrograms-1.kg-1.min-1; P = 0.014) and vasodilation (-469 +/- 111 to -1,446 +/- 309 peripheral resistance units.microgram-1.kg-1.min-1; P = 0.0224) to Iso infusion. There was no alteration in blood pressure or vascular resistance responses to PE infusion after HDT. Our results provide evidence that simulated microgravity causes selective increases in beta 1- and beta 2-adrenoreceptor responsiveness without affecting alpha 1-vascular adrenoreceptor responses.

Adult↗
PubMed1999

[Intergral criterion and prediction of cosmonauts professional reliability in flight].

Discussed is the problem of professional reliability of cosmonauts simulating manual docking of transport vehicle SOYUZ-TM to space station MIR during acute adaptation to microgravity. A new concept of cosmonaut's reliability qualification is based on the parameters that characterize the systemic body response to job-related factors: integral efficiency and psychophysiological "cost". Justification is given to the statistic methodology of the change-over from prime job quality indices and the functional state of human to integral. Underlined is the possibility to apply this methodical approach to enhancement of the program of assessment and recovery of the professional reliability of cosmonauts in flight.

Adaptation, Psychological↗
PubMed2000

[Mechanisms of volume regulation under the effect of spaceflight factors].

Studied was the significance of the volume regulating system of the human body for adaptive readjustment of the water-electrolyte homeostasis to changed position, immersion, and microgravity. Experiments were made to investigate volume regulation and associated events and their sequence as during simulation studies (bed rest, immersion, tilting, g-loads), so in Salyut-7 and Mir missions from 7 to 438 days of length. Established was a distinct relationship between the central venous pressure and hydration state of the body, and determined were quantitative parameters of circulating blood migration along the body axis during HDT and hypovolemia. The experiments revealed interdependence of g-tolerance and the way hypohydration had been triggered by, the mechanism of which was also explored. Investigations of human early adaptation to space flight allowed development of an approach to the hydration control (pharmacological hypohydration) with the purpose to minimize discomfort and to improve human performance at the beginning of space mission.

Adaptation, Physiological↗
PubMed1995

Growing super-dwarf wheat in Svet on Mir.

In cooperation with Russian colleagues, we will carry out three experiments with a super-dwarf cultivar of wheat in the plant growth chamber Svet on the Russian Space Station Mir: an early test of the root module and other instruments (July-August, 1995), a seed-to-seed experiment (1996), and a third planting that will be harvested after about 35 days, frozen, and returned to Earth for chemical analysis (1996). Plants will be photographed, sampled,and chemically fixed at intervals during the first two plantings. Instrumentation has been constructed to measure CO2, water vapor, air temperatures, infrared leaf temperatures, oxygen, pressure, irradiance levels, and moisture in the root module substrate (Balkanine). The primary objective of this equipment is to allow controllers to eliminate plant environmental stresses, leading to vigorous plant growth in microgravity. We are testing sampling and analysis techniques and growing plants in ground versions of Svet in Moscow and in Svet mockups in Utah: 12 chambers in two temperature-controlled rooms, with two compartments in each chamber (two temperatures, four CO2 concentrations, and three photoperiods in a current experiment).

Air Conditioning↗
PubMed1998

Bioregenerative [correction of bioregnerative] life support: not a picnic.

If humans are to live permanently in space, regenerative life support systems are an enabling technology and must replace the picnic approach of taking all supplies required for each mission. These systems are classified by technologies as either physical/chemical or bioregenerative. Both of these system-types can recycle water, remove carbon dioxide, produce oxygen, and recover essential elements from waste products. Bioregenerative can also produce food, thus, making it essential if humans are to exist in space independent of earth. A solely bioregenerative life support system includes plants as a biomass production module and microbial organisms in bioreactors as a resource recovery module. In the Advanced Life Support Program, bioregenerative life support systems are being investigated through a research and technology development project which includes large scale testing as part of the Breadboard Project and human tests conducted in the soon to be constructed BioPlex facility. Research and technology development efforts are directed toward optimizing biomass productivity in controlled chambers by developing light weight, energy efficient, and automated systems; recycling liquid and solid wastes; baselining the operation of bioreactors; determining system microbial stability; assessing chemical contamination; and building models required for long term system operations. The program will include space flight studies in the near future to determine if these life support technologies will function in microgravity. When a bioregenerative system is finally incorporated into a mission, the conversion from a picnic and resupply mentality to permanent recycling and independence from earth will be complete.

Biofilms↗
PubMed1993

European Astronaut Candidates in training in the CIS.

For four weeks in October and November 1992, we--three European Astronaut Candidates from the European Astronauts Centre (EAC) in Cologne--were fortunate enough to have the opportuity to live and be trained in Star City. It proved to be a fascinating experience, both for us and the EAC Training Engineer, Antonio Torres, who accompanied us.

Aerospace Medicine↗
PubMed1992

Computer simulation analysis of the effects of countermeasures for reentry orthostatic intolerance.

Fluid loading is a countermeasure currently in routine use to improve the g-tolerance of crewmembers during reentry and return of Shuttle flights. However, its effectiveness diminishes with mission duration. Countermeasures that will be effective on long-duration flights are needed and are presently under development. This paper discusses the application of computer simulation in the analysis of the effects of countermeasures for reentry orthostatic intolerance. The results suggest improvements upon the fluid loading countermeasure currently in use.

Blood Volume↗
PubMed1994

Gravitational neuromorphology.

This review shows that morphological studies of the central, peripheral and autonomic nervous system of animals exposed to altered gravity yield data which are extremely significant for our understanding of the mechanisms of adaptation of the nervous system, and of the mammalian organism as a whole, to increased and decreased loading. Neuromorphological studies, correlating structure and function, indicate a decreased activity in weightlessness for spinal ganglia neurons and motoneurons of the spinal cord, as well as the neurons of the hypothalamic nuclei producing arginine vasopressin and growth hormone releasing factor. Structural changes of the somatosensory cortex and spinal ganglia suggest a decreased afferent flow to the somatosensory cortex in microgravity. The results characterize the mechanisms of structural adaptation to a decreased afferent flow in microgravity by the neurons in the hemisphere cortex and brain stem nuclei. There is also morphological evidence for an increased sensitivity of the otolith apparatus and for the development of a hyponoradrenergic syndrome in weightlessness. These studies have shown that both microgravity and the simulation of microgravity effects by tail suspension-induced structural changes in the large neurons of lumbar spinal ganglia and motoneurons of the lumbar spinal cord, which occur under conditions of nerve cell hypoactivity. The structural changes, and consequently the development of neuron hypoactivity, are expressed more extensively after microgravity than after tail suspension for the same length of time. The influence of microgravity and hypergravity on animals is expressed by opposing changes in nervous tissue structure in the spinal ganglia, spinal cord, and nodulus of cerebellar vermis. These changes indicate neuron hypoactivity under microgravity and neuron hyperactivity under 2 G. Morphological assessment of the functional state of other structures of the brain under hypergravity will require further study. Can all structural changes which occur in nerve tissue under microgravity or under hypergravity be explained on the basis of increased or decreased activity of its structural elements? The presently available data regarding the correlation of structure and functional state of cells in brain and spinal cord suggest an affirmative answer. Ultrastructural studies of the nodular cortex of the cerebellum in rats after different duration spaceflights provide what appears to be a convincing example. However, it should be pointed out that the criteria for the morphological assessment of the functional state of single nerve cells will certainly be different from those for groups of neurons connected in a nerve cell network.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1975

Oxygen cost during exercise in simulated subgravity environments.

Oxygen cost (VO2) and heart rate (HR) were determined during treadmill walking in simulated subgravity environments. The long axis of the subject's body was suspended parallel to the floor in a slow rotation room with feet aligned on the surface of a treadmill mounted 90 degrees on the wall. Without rotation, the subjects were virtually weightless against the treadmill; with centrifugation, environments of 0.25, 0.5 and 1 G were simulated. VO2 (open circuit) and HR (ECG) were measured during the 5th minute of walking at 3.2, 4.7 and 6.1 km/h. Similar measurements were also determined during walking at 1/2-G using the inclined plane technique. VO2 per unit mass and HR were significantly reduced in all subgravity environments. However, net VO2 per unit weight carried and, therefore, mechanical efficiency was found to be independent of gravity. This supports the idea that the most probable cause for the decreased O2 cost with reduced gravity is less body weight carried.

Adult↗
PubMed1993

European isolation and confinement study. Confinement and immune function.

During spaceflight, several unusual factors act on the physiology of the astronaut: weightlessness, radiation, confinement, isolation, living and working in a small group, workload, and anxiety. The resulting physiological changes are known to include alterations of the immune system. It is difficult to determine from observations on astronauts which space-related factor(s) are responsible for the immune changes. Studies of analogous environments on Earth have supplied only scarce information. Dedicated simulation studies provide a better tool, where some space-related stress factors (weightlessness, radiation) are absent, but others are or can be present: isolation and confinement, small group living, workload, and anxiety. A reduction in immune activity was found in bed rest studies and in long-term Soviet confinement experiments (after 90 days). In the ISEMSI confinement experiment (28 days), a tendency to immune activation (PHA-reactivity and interleukin-2 production) was observed in two out of six subjects. There is a need for further experiments, in which a large number of immunological parameters can be analyzed.

Humans↗
PubMedDate not supplied

[Dynamics of the biochemical makeup of the blood in cosmonauts during flights].

Prolonged space flights (15 to 63 days) led to changes in the biochemical composition of the blood that were observed both during and after flight. Blood samples were withdrawn inflight, stored in a special device onboard and analyzed on return to Earth. The data obtained in real flights were compared with those from the 30-day simulation flight. In real and simulated flights the urea content showed the most significant changes. Inflight it increased to 40 mg% versus 31 mg% preflight. The urea content grew on the 3rd-5th flight day, reaching maximum on the 15-30th day and decreasing again afterwards. The content of glucose and inorganic phosphorus increased slightly whereas that of acid-soluble and lipid phosphorus remained unaltered. The level of cholesterol decreased. The striking similarity between the changes in blood biochemistries during real and simulated flights suggests that they are induced by factors other than weightlessness.

Blood↗
PubMed1998

Recording heart rate and blood pressure in rats during parabolic flight.

The way in which the cardiovascular system adapts to weightlessness is still under discussion. No data are yet available on the responses of rats during space flight, although this animal is commonly used in simulation studies. We have designed and tested a protocol to study the short term responses of the cardiovascular system to weightlessness during parabolic flight. A telemetry system was used to measure heart rate (HR) and blood pressure. It was possible to collect and record radio-signals without any interference. Microgravity caused a reduction in HR, an increase in mean arterial pressure (MAP, 7%), and a non-significant decrease in central venous pressure (CVP, 13%). The change in CVP was similar to the decrease observed in human space flight. This type of study may also be feasible for longer exposure of rats to microgravity (space flight).

Animals↗
PubMed1987

Man in space.

Today, more than 20 years after the first in the world man's space walk, soviet cosmonautics gained large experience of extravehicular activity (EVA). Space suits of high reliability, onboard facilities for passing through the airlock, sets of special tools and technological rigging, as well as procedures for carrying out various EVA's were developed. In the course of the Salyut-7 space station orbital operation the EVA's have become regular. The author of the report as the participant of the EVA's considers the main steps of man activities in space and analyzes specific problems arised in performing such activities.

Astronauts↗
PubMedDate not supplied

EVA worksite analysis--use of computer analysis for EVA operations development and execution.

To sustain the rate of extravehicular activity (EVA) required to assemble and maintain the International Space Station, we must enhance our ability to plan, train for, and execute EVAs. An underlying analysis capability has been developed to ensure EVA access to all external worksites as a starting point for ground training, to generate information needed for on-orbit training, and to react quickly to develop contingency EVA plans, techniques, and procedures. This paper describes the use of computer-based EVA worksite analysis techniques for EVA worksite design. EVA worksite analysis has been used to design 80% of EVA worksites on the U.S. portion of the International Space Station. With the launch of the first U.S. element of the station, EVA worksite analysis is being developed further to support real-time analysis of unplanned EVA operations. This paper describes this development and deployment of EVA worksite analysis for International Space Station (ISS) mission support.

Astronauts↗