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Results for “GRAVITATIONAL EFFECT”

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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Growth and differentiation of mammalian embryonic tissues exposed to hypergravity in vivo and in vitro

In about 10 years or so, men and women from Earth will be long-term inhabitants of a space station aboard which plants and animals will be growing and developing in gravities other than that of Earth. The effect of gravitational changes on development was examined. It is indicated that differentiation is speeded up under excess G and slowed in low or null G. The effects of exposure to excess gravity on fusion of the embryonic mouse secondary palate were studied. During fusion, the palatal shelves first adhere by means of glycoproteins appearing along the medial epithelial edge (MEE). The contacting epithelia then reorganize and undergo programmed cell death, allowing the underlying mesenchymes to come in contact. The process of cell death occurs in vitro at about the same rate that it occurs in vivo.

Duke, P. J.↗
NASA NTRS1986

Tethered constellations, their utilization as microgravity platforms and relevant features

The gravitational, thermal, and dynamic docking effects on tethered platforms were studied. The near-earth environment has gravitational effects such a g-jitters and intermittencies, g-noise, and frequency and amplitude features which may influence life science, materials processing, and fluid processes research and commercial activities. Artificial gravity is produced by minute accelerations imparted by tethers. The magnitudes of gravitational forces produced by tethers 100 and 100,000 m long at various altitudes from 463 to 35,786 km are calculated. Thermal analyses were performed for stainless steel and Kevlar tethers, showing the steel tether could vary 300 m in length and the polyamide 25 m during one orbit. Finally, consideration given to docking with a tethered platform revealed that the center of mass could change, which would produce, however, negligible changes in orbit and therefore gravity.

Napolitano, L. G.↗
NASA NTRS1996

Infrared light-emitting diode radiation causes gravitropic and morphological effects in dark-grown oat seedlings

Oat (Avena sativa cv Seger) seedlings were irradiated with IR light-emitting diode (LED) radiation passed through a visible-light-blocking filter. Infrared LED irradiated seedlings exhibited differences in growth and gravitropic response when compared to seedlings grown in darkness at the same temperature. Thus, the oat seedlings in this study were able to detect IR LED radiation. These findings call into question the use of IR LED as a safe-light for some photosensitive plant response experiments. These findings also expand the defined range of wavelengths involved in radiation-gravity (light-gravity) interactions to include wavelengths in the IR region of the spectrum.

NASA Center KSC↗
NASA NTRS1991

Gravitational lensing and the Lyman-alpha forest

Possible connections between the inhomogeneities responsible for the Lyman-alpha forest in quasar spectra and gravitational lensing effects are investigated. For most models of the Lyman-alpha forest, no significant lensing is expected. For some versions of the CDM model-based minihalo hypothesis, gravitational lensings on scales less than abour 0.1 arcsec would occur with a frequency approaching that with which ordinary galaxies cause arcsecond scale lensing.

Ikeuchi, Satoru↗
NASA NTRS1993

Gravitational instability of a rotating partially-ionized plasma carrying a uniform magnetic field with Hall effect

The problem of gravitational instability of an infinite homogeneous self-gravitating medium carrying a uniform magnetic field in the presence of Hall effect has been investigated to include the effect due to rotation. The dispersion relation has been obtained. It has been found that the Jeans's criterion for the instability remains unaffected even when the effect due to rotation is considered in the presence of Hall effect carrying a uniform magnetic.

Kumar, Vinod↗
NASA NTRS1991

Maximum expiratory flow-volume curves during short periods of microgravity

Nine normal subjects were studied in a NASA microgravity research aircraft to elucidate the effect of normal gravitation on the shape of the maximum expiratory flow-volume (MEFV). They performed multiple MEFV maneuvers at 0, 1, and approximately 2 G. The MEFV curves for each subject were filtered, aligned at residual volume, and ensemble-averaged to produce an average MEFV curve for each state, allowing differences to be studied. Most subjects showed a decrease in the forced vital capacity at 0 G. The mean lung volume associated with a given flow was lower at 0 G over about the upper half of the vital capacity. There were consistent but highly individual changes in the position and magnitude of detailed features of the curve. This supports the concept that the location and motion of choke points that determine the detailed individual configuration of MEFG curves can be significantly influenced by gravitational forces, presumably via the effects of change in longitudinal tension on local airway pressure-diameter behavior and thus wave speed.

Guy, H. J. B.↗
NASA NTRS1990

The effect of hyperdynamic fields on the oxidative metabolism of the paraventricular nucleus

An important issue in space biology and medicine is understanding the effect of gravitational changes on the mechanisms that regulate fluid homeostasis. The results of this study show that, following 7-d exposure to a 2 G or 3 G hyperdynamic field, rats exhibited a linear increase in the cytochrome oxidase staining of neurons in the paraventricular nucleus (PVN). The elevated oxidative metabolism in the PVN suggests that there was an increase in the manufacturing and release of vasopressin into the plasma in response to a perceived hypovolemic condition caused by increased hydrostatic pressure and redistribution of fluid to the periphery. Since vasopressin also has widespread cardiovascular effects, it will be important to understand the relationship between vasopressin and altered gravitational fields.

Murakami, Dean M.↗
NASA NTRS1996

Microgravity Particle Dynamics

This research seeks to identify the experiment design parameters for future flight experiments to better resolve the effects of thermal and velocity gradients on gas-solid flows. By exploiting the reduced body forces and minimized thermal convection current of reduced gravity experiments, features of gas-solid flow normally masked by gravitationally induced effects can be studied using flow regimes unattainable under unigravity. This paper assesses the physical scales of velocity, length, time, thermal gradient magnitude, and velocity gradient magnitude likely to be involved in laminar gas-solid multiphase flight experiments for 1-100 micro-m particles.

Clark, Ivan O.↗
NASA NTRS1990

Prediction of the ullage gas thermal stratification in a NASP vehicle propellant tank experimental simulation using FLOW-3D

As part of the National Aero-Space Plane (NASP) project, the multi-dimensional effects of gravitational force, initial tank pressure, initial ullage temperature, and heat transfer rate on the 2-D temperature profiles were studied. FLOW-3D, a commercial finite difference fluid flow model, was used for the evaluation. These effects were examined on the basis of previous liquid hydrogen experimental data with gaseous hydrogen pressurant. FLOW-3D results were compared against an existing 1-D model. In addition, the effects of mesh size and convergence criteria on the analytical results were investigated. Suggestions for future modifications and uses of FLOW-3D for modeling of a NASP tank are also presented.

Hardy, Terry L.↗
NASA NTRS1997

NASA Microgravity Combustion Science Program

Combustion is a key element of many critical technologies used by contemporary society. For example, electric power production, home heating, surface and air transportation, space propulsion, and materials synthesis all utilize combustion as a source of energy. Yet, although combustion technology is vital to our standard of living, it poses great challenges to maintaining a habitable environment. For example, pollutants, atmospheric change and global warming, unwanted fires and explosions, and the incineration of hazardous wastes are major problem areas which would benefit from improved understanding of combustion. Effects of gravitational forces impede combustion studies more than most other areas of science since combustion involves production of high-temperature gases whose low density results in buoyant motion, vastly complicating the execution and interpretation of experiments. Effects of buoyancy are so ubiquitous that their enormous negative impact on the rational development of combustion science is generally not recognized. Buoyant motion also triggers the onset of turbulence, yielding complicating unsteady effects. Finally, gravity forces cause particles and drops to settle, inhibiting deconvoluted studies of heterogeneous flames important to furnace, incineration and power generation technologies. Thus, effects of buoyancy have seriously limited our capabilities to carry out 'clean' experiments needed for fundamental understanding of flame phenomena. Combustion scientists can use microgravity to simplify the study of many combustion processes, allowing fresh insights into important problems via a deeper understanding of elemental phenomena also found in Earth-based combustion processes and to additionally provide valuable information concerning how fires behave in microgravity and how fire safety on spacecraft can be enhanced.

King, Merrill K.↗