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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

On the local standard of rest

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a sipral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars.

Yuan, C.↗
NASA NTRS1983

Plasma rest frame frequencies and polarizations of the low-frequency upstream waves - ISEE 1 and 2 observations

The plasma rest frame frequencies and polarizations of the large amplitude low frequency (0.03 Hz) upstream waves are investigated using magnetic field data from the dual ISEE 1 and 2 spacecraft. The monochromatic sinusoidal waves associated with intermediate ion fluxes are propagating in both the Alfven and magnetosonic modes, in both cases with typical frequencies approximately 0.1 times the local proton gyrofrequency and wavelengths of approximately 1 R(E). It is shown that the generation of the magnetosonic mode can be explained by the cyclotron resonance mechanism driven by narrow reflected ion beams, but the concurrent observation of Alfven mode waves appears to require wave generation by the more isotropic diffuse ion distributions as well.

Hoppe, M. M.↗
NASA NTRS1983

Numerical solutions for spin-up from rest in a cylinder

A set of three-dimensional flow-field data for the region around a cylinder impulsively spun-up from rest was derived with a numerical model based on the Navier-Stokes equations. Laser-Doppler anemometer data in the azimuthal direction was employed to test the model predictions, and data was developed for a flowfield with Ekman numbers from 9.18/1,000,000 to 9.18/10,000. The contributions of inviscid and viscous terms were determined as functions of radius and time. It was found that immediately after start-up viscous diffusion is the dominant factor, which is replaced by nonlinear radial advection. The Coriolis force dominates in the later stages of spin-up. The inward radial flow is a maximum near the front, where the vertical velocity is small, but features strong radial gradients, as it does at the edge of the Ekman layer.

Hyun, J. M.↗
NASA NTRS1983

Human respiration at rest in rapid compression and at high pressures and gas densities

The ventilation (V), end-tidal PCO2 (PACO2), and CO2 elimination rate were determined in men at rest breathing CO2-free gas over the pressure range 1-50 ATA and the gas density range 0.4-25 g/l, during slow and rapid compressions, at stable elevated ambient pressures and during slow decompressions. Progressive increase in pulmonary gas flow resistance due to elevation of ambient pressure and inspired gas density to the He-O2 equivalent of 5000 feet of seawater was found to produce a complex pattern of change in PACO2. It was found that as both ambient pressure and pulmonary gas flow resistance were progressively raised, PACO2 at first increased, went through a maximum, and then declined towards values near the 1 ATA level. It is concluded that this pattern of PACO2 change results from the interaction on ventilation of the increase in pulmonary resistance due to the elevation of gas density with the increase in respiratory drive postulated as due to generalized central nervous system excitation associated with exposure to high hydrostatic pressure. It is suggested that a similar interaction exists between increased gas flow resistance and the increase in respiratory drive related to nitrogen partial pressure and the resulting narcosis.

Gelfand, R.↗
NASA NTRS1983

On the local standard of rest

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a spiral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars. Previously announced in STAR as N83-24443

Yuan, C.↗
NASA NTRS1983

Bed-rest studies - Fluid and electrolyte responses

Confinement in the horizontal position for 2 to 3 weeks results in a chronic decrease in plasma volume, increased interstitial fluid volume, and unchanged or slightly increased extracellular fluid volume. Concentrations of blood electrolytes, glucose, and nitrogenous constituents remain within normal limits of variability when maintenance levels of isometric or isotonic exercise are performed for 1 hr/day. Hematocrit and plasma osmolality can be elevated significantly throughout bed rest (BR). Significant diuresis occurs on the first day, and increases in urine Na and Ca continue throughout BR, although voluntary fluid intake is unchanged. Urine Na and K are evaluated during the second week of BR in spite of stabilization of PV and extracellular volume. The initial diuresis probably arises from extracellular fluid while subsequent urine loss above control levels must come from the intracellular fluid. Preservation of the extracellular volume takes precedance over maintenance of the intracellular fluid volume. The functioning of a natriuretic factor (hormone) to account for the continued increased loss of Na in the urine is suggested. Previously announced in STAR as N83-24160

Greenleaf, J. E.↗
NASA NTRS1988

Creep rupture analysis of a beam resting on high temperature foundation

A simplified uniaxial strain controlled creep damage law is deduced with the use of experimental observation from a more complex strain dependent law. This creep damage law correlates the creep damage, which is interpreted as the density variation in the material, directly with the accumulated creep strain. Based on the deduced uniaxial strain controlled creep damage law, a continuum mechanical creep rupture analysis is carried out for a beam resting on a high temperature elastic (Winkler) foundation. The analysis includes the determination of the nondimensional time for initial rupture, the propagation of the rupture front with the associated thinning of the beam, and the influence of creep damage on the deflection of the beam. Creep damage starts accumulating in the beam as soon as the load is applied, and a creep rupture front develops at and propagates from the point at which the creep damage first reaches its critical value. By introducing a series of fundamental assumptions within the framework of technical Euler-Bernoulli type beam theory, a governing set of integro-differential equations is derived in terms of the nondimensional bending moment and the deflection. These governing equations are subjected to a set of interface conditions at the propagating rupture front. A numerical technique is developed to solve the governing equations together with the interface equations, and the computed results are presented and discussed in detail.

Gu, Randy J.↗
NASA NTRS1989

Orthostatic responses following 30-day bed rest deconditioning with isotonic and isokinetic exercise training

The effects of intensive exercise training on tilt tolerance following deconditioning of astronauts were investigated by studying orthostatic responses of 19 subjects who underwent two intensive exercise-training regimens during 30 days of -6-deg head-down bed rest (BR). Subjects were divided into no-exercise control group, and two exercise groups, one performing isotonic (Quinton ergometer) exercises, the other doing isokinetic (Lido ergometer) exercises. A 60-deg head-up tilt test was administered on the control day 1 and BR day 30; the test was terminated at 60 min or when presyncopal signs and/or symptoms occurred. It was found that exercise training did not affect tilt tolerance significantly.

Greenleaf, J. E.↗
NASA NTRS1989

Energy and thermal regulation during bed rest and spaceflight

This paper presents data available from bed-rest and flight studies on the energy metabolism and thermoregulatory parameters and their changes during long-duration space missions which may influence requirements of astronauts for food and water. It is calculated, on the basis of 3100 kcal and 2.2 l water a day, with 1 h/day moderate exercise, that the requirements for a 2-yr flight would be 2,263,000 kcal and 1606 l water for each astronaut. One daily 5-h-long extravehicular sortie would require an additional 529,250 kcal and 1,095 l of water per year. Changes in the efficiency of work or metabolism would affect these nutritional requirements for long spaceflights. Factors that would increase food and water requirements are discussed.

Greenleaf, John E.↗
NASA NTRS1989

Exercise countermeasures for bed rest deconditioning

The major objectives were to evaluate the efficiency of different modes of exercise (isotonic and isokinetic) for countering the effects of bed rest deconditioning on work capacity (peak oxygen uptake), muscular strength, orthostatic tolerance, posture, equilibrium and gait; and to collect additional data of a more fundamental nature to help understand how these deconditioning responses occur. These data will be used for writing prescriptions for exercise to be utilized by astronauts for maintaining work capacity and well-being on Freedom Station, and to determine what exercise devices should be place in the station.

Greenleaf, John↗
NASA NTRS1991

Effect Of Bed Rest On Tolerance To Acceleration

Report describes experimental comparative study of tolerance of aerobically fit men and sedentary men to +Gz acceleration. Designed to confirm or deny previous observations that long-term aerobic training reduces tolerance to acceleration. Data accumulated in study showed decrease in tolerance to acceleration caused by deconditioning effect of bed rest more pronounced in fit men than in sedentary men. Suggests physically fit people need additional measures to reduce loss of tolerance to acceleration during microgravity exposure.

Goldwater, Danielle J.↗
NASA NTRS1992

Deconditioning Under Prolonged, Repeated Bed Rest

Cardiovascular deconditioning from prolonged bed rest not counteracted by mild exercise and requires at least 3 weeks for recovery, report contends. Involves more than simple decrease in volume of plasma; neurohumoral mechanisms, loss of mass of skeletal muscles, and general decrease of body's metabolic needs seem to be major contributors.

Sandler, Harold↗
NASA NTRS1992

Joint U.S./U.S.S.R. Study Of Effects Of Bed Rest

Horizontal and head-down positions investigated at two research centers. Report presents results of joint experimental study of effects of bed rest conducted at Ames Research Center in California and Institute for Biomedical Problems in Moscow. Study conducted under identical conditions at both locations. In addition to generating useful scientific data, provided basis for comparison of physiological reactions and standardization of procedures and methods.

Sandler, H.↗
NASA NTRS1992

Effects Of Exercise During Prolonged Bed Rest

Report describes experiment to investigate effects of isotonic and isokinetic leg exercises in counteracting effects of bed rest upon physical and mental conditions of subjects. Data taken on capacity for work, endurance and strength, tolerance to sitting up, equilibrium, posture, gait, atrophy, mineralization and density of bones, endocrine analyses concerning vasoactivity and fluid and electrolyte balances, intermediary metabolism of muscles, mood, and performance.

Arnaud, S.↗
NASA NTRS1992

Fuel utilization during exercise after 7 days of bed rest

Energy yield from carbohydrate, fat, and protein during physical activity is partially dependent on an individual's fitness level. Prolonged exposure to microgravity causes musculoskeletal and cardiovascular deconditioning; these adaptations may alter fuel utilization during space flight. Carbohydrate and fat metabolism during exercise were analyzed before and after 7 days of horizontal bed rest.

Barrows, Linda H.↗
NASA NTRS1992

Squeezed states, time-energy uncertainty relation, and Feynman's rest of the universe

Two illustrative examples are given for Feynman's rest of the universe. The first example is the two-mode squeezed state of light where no measurement is taken for one of the modes. The second example is the relativistic quark model where no measurement is possible for the time-like separation fo quarks confined in a hadron. It is possible to illustrate these examples using the covariant oscillator formalism. It is shown that the lack of symmetry between the position-momentum and time-energy uncertainty relations leads to an increase in entropy when the system is different Lorentz frames.

Han, D.↗
NASA NTRS1992

User's guide to the Reliability Estimation System Testbed (REST)

The Reliability Estimation System Testbed is an X-window based reliability modeling tool that was created to explore the use of the Reliability Modeling Language (RML). RML was defined to support several reliability analysis techniques including modularization, graphical representation, Failure Mode Effects Simulation (FMES), and parallel processing. These techniques are most useful in modeling large systems. Using modularization, an analyst can create reliability models for individual system components. The modules can be tested separately and then combined to compute the total system reliability. Because a one-to-one relationship can be established between system components and the reliability modules, a graphical user interface may be used to describe the system model. RML was designed to permit message passing between modules. This feature enables reliability modeling based on a run time simulation of the system wide effects of a component's failure modes. The use of failure modes effects simulation enhances the analyst's ability to correctly express system behavior when using the modularization approach to reliability modeling. To alleviate the computation bottleneck often found in large reliability models, REST was designed to take advantage of parallel processing on hypercube processors.

Nicol, David M.↗