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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

A generalized theory on the noise generation from supersonic shear layers.

A generalization is presented of Phillips' (1960) theory of noise generation by supersonic turbulent shear layers. Both Mach wave radiation and non-Mach wave noise radiation mechanisms are considered. The range of validity of Phillips' theory has been expanded to include the low supersonic and transonic ranges. These generalizations are important not only for their analytical rigor, but also for their prospective applications to practical problems in jet noise prediction and control. The noise generation mechanisms in a supersonic jet are found to differ from those in a subsonic jet. The theory is considered to offer some prospects of answering important questions in supersonic jet noise, such as noise source distribution, mean flow refraction effects, directivity, spectrum, and efficiency of noise radiation.

Pao, S. P.↗
NASA NTRS1972

The synchronous meteorological satellite /SMS/ system.

The responsibilities of the National Aeronautics and Space Administration (NASA) and Department of Commerce (DOC) pertaining to SMS are described in this paper. A description of the program objectives, payload, and spacecraft subsystems, is included along with an abbreviated description of the SMS ground system. Particular interest is directed towards the visible and infrared spin-scan radiometer (VISSR) as it will be the prime sensor and its performance directly effect the mission objectives. Also, of significant importance is the description of the communications subsystem since transmission and retransmission of image data, data relay, and data collection platform (DCP) transmissions play such a major role in the system. The conclusion is established that the current plans form a workable system for providing timely, high-quality day and night imaging of the earth's weather.

Burr, P. T.↗
NASA NTRS1973

Directivity of high-energy X-ray emission during flares.

The solar X-ray flare model of Jager and Kundu (1963), supported by the direct evidence recently provided by Tindo et al. (1972) for the presence of radial electron beams indicated in Jager-Kundu's model, is discussed with respect to its apparent conflict with Ohki's (1969) and Pinter's (1969) indications of a directivity effect likely to occur for X-ray flares at very high photon energies. An attempt is made to explain this apparent conflict.

Phillips, K. J. H.↗
NASA NTRS1973

Television studies of faint meteors

Low-light-level television systems have shown considerable promise in the optical extension of meteor flux measurements to faint magnitudes. In particular, the secondary electron conduction vidicon has demonstrated its ability to detect fast, faint meteors. Such a system has been calibrated and used to obtain the cumulative flux of meteors above threshold masses of .1 to .001 gram. The results indicate a basic continuity with photographic and satellite measurements. The observed data were further analyzed for diurnal and directional effects.-

Clifton, K. S.↗
NASA NTRS1974

Anthropometric changes and fluid shifts

Several observations of body size, shape, posture, and configuration were made to document changes resulting from direct effects of weightlessness during the Skylab 4 mission. After the crewmen were placed in orbit, a number of anatomical and anthropometric changes occurred including a straightening of the thoracolumbar spine, a general decrease in truncal girth, and an increase in height. By the time of the earliest in-flight measurement on mission day 3, all crewmen had lost more than two liters of extravascular fluid from the calf and thigh. The puffy facies, the bird legs effect, the engorgement of upper body veins, and the reduced volume of lower body veins were all documented with photographs. Center-of-mass measurements confirmed a fluid shift cephalad. This shift remained throughout the mission until recovery, when a sharp reversal occurred; a major portion of the reversal was completed in a few hours. The anatomical changes are of considerable scientific interest and of import to the human factors design engineer, but the shifts of blood and extravascular fluid are of more consequence. It is hypothesized that the driving force for the fluid shift is the intrinsic and unopposed lower limb elasticity that forces venous blood and then other fluid cephalad.

Thornton, W. E.↗
NASA NTRS1974

A time-dependent diffusion convection model for the long term modulation of cosmic rays

A model is developed which incorporates to first order the direct effects of the time dependent diffusive propagation of interstellar cosmic rays in a slowly changing interplanetary medium. The model provides a physical explanation for observed rigidity-dependent phase lags in modulated spectra (cosmic ray hysteresis). The average distance to the modulating boundary during the last solar cycle is estimated.

Gallagher, J. J.↗
NASA NTRS1974

Preliminary analysis of Skylab RADSCAT results over the ocean

Preliminary observations at 13.9 GHz of the radar backscatter and microwave emission from the sea were analyzed using data obtained by the radiometer scatterometer on Skylab. Results indicate approximately a square-law relationship between differential scattering coefficient and windspeed at angles of 40 deg to 50 deg, after correction for directional effect, over a range from about 4 up to about 25 meters/sec. The brightness temperature response was also observed, and considerable success was achieved in correcting it for atmospheric attenuation and emission. Measurements were made in June, 1973, over Hurricane Ava off the west coast of Mexico and over relatively calm conditions in the Gulf of Mexico and Caribbean Sea.

Moore, R. K.↗
NASA NTRS1975

Magnetic torque on a rotating superconducting sphere

The London theory of superconductivity is used to calculate the torque on a superconducting sphere rotating in a uniform applied magnetic field. The London theory is combined with classical electrodynamics for a calculation of the direct effect of excess charge on a rotating superconducting sphere. Classical electrodynamics, with the assumption of a perfect Meissner effect, is used to calculate the torque on a superconducting sphere rotating in an arbitrary magnetic induction; this macroscopic approach yields results which are correct to first order. Using the same approach, the torque due to a current loop encircling the rotating sphere is calculated.

Holdeman, L. B.↗
NASA NTRS1975

A time-dependent diffusion-convection model for the long-term modulation of cosmic rays

The model considered incorporates, to first order, the direct effects of the time-dependent diffusive propagation of interstellar cosmic rays in a slowly changing interplanetary medium. A one-dimensional model is discussed along with a three-dimensional radial wind. An evaluation is conducted of average diffusive propagation times. It is found that the effects of time-dependent diffusive propagation can be quite significant. A rigidity-dependent time delay or 'lag' in the modulated spectra is predicted.

Ogallagher, J. J.↗
NASA NTRS1975

Review of measured vibration and noise environments experienced by passengers in aircraft and in ground transportation systems

Measured vibration and interior noise data are presented for a number of air and surface vehicles. Consideration is given to the importance of direction effects; of vehicle operations such as take-off, cruise, and landing; and of measurement location on the level and frequency of the measurements. Various physical measurement units or descriptors are used to quantify and compare the data. Results suggest the range of vibration and noise associated with a particular mode of transportation and illustrate the comparative levels in terms of each of the descriptors. Collectively, the results form a data base which may be useful in assessing the ride of existing or future systems relative to vehicles in current operation.

Stephens, D. G.↗
NASA NTRS1976

Undercooling of materials during solidification in space

A theoretical research program was undertaken on the under cooling and solidification of materials under variable external field conditions. A catalog of theories and models of nucleation of solid phases in the melt is provided, as is a discussion of the relation of undercooling to intermolecular potentials, the dependence of growth rate on undercooling, the influence of undercooling on liquid-solid interface stability and solid structure, the direct effects of external fields on melts, the relation of solid physical properties to structure and the role of nucleants in solidification. Results of the theoretical analysis of several experiments related to the space processing applications program are given, and recommendations for future experiments and further theoretical developments along with procedures for correlation of theory and experiment are specified.

Miller, R. I.↗
NASA NTRS1977

Speculations on the consequences to biology of space shuttle-associated increases in global UV-B radiation

Various aspects of the impact of ozone depletion on the biosphere are assessed and discussed. Speculations on the factors which determine the extent and nature of biological damage due to an increased flux of ultra violet light are presented. It is concluded that a complete assessment must consider both direct effects (organisms) as well as indirect effects (ecosystems). The role of computer simulation of ecosystem models as a predictive tool is examined.

Averner, M. M.↗
NASA NTRS1977

The Viking Relativity Experiment

Measurements of the round-trip time of flight of radio signals transmitted from the earth to the Viking spacecraft are being analyzed to test the predictions of Einstein's theory of general relativity. According to this theory the signals will be delayed by up to approximately 250 microsec owing to the direct effect of solar gravity on the propagation. A very preliminary qualitative analysis of the Viking data obtained near the 1976 superior conjunction of Mars indicates agreement with the predictions to within the estimated uncertainty of 0.5%.

Shapiro, I. I.↗
NASA NTRS1977

Comparative vibration environments of transportation vehicles

Measured vibration data are presented for a number of air and surface vehicles. Consideration is given to the importance of direction effects; of vehicle operating modes such as takeoff, cruise, and landing; and of measurement location on the level and frequency of the measurements. Various physical measurement units or descriptors are used to quantify and compare the data. Results suggest the range of vibration associated with a particular mode of transportation and illustrate the comparative levels in terms of each of the descriptors. Collectively, the results form a data base which may be useful in assessing the ride of existing or future systems relative to vehicles in current operation. In addition, subjective response data obtained from vibration simulator studies are presented to illustrate human response characteristics as well as to indicate a laboratory approach for the development of ride-quality criteria.

Stephens, D. G.↗
NASA NTRS1978

Sound propagation through a subsonic jet due to a source near the duct exit

Matched asymptotic solutions are constructed for the acoustic potentials of a periodic point source located in a two-dimensional subsonic jet near the exit of the duct with the ratio of the duct thickness to the acoustic wave length as the small parameter. The leading term of the far field solution has the same directionality effect as that for an infinite jet without the duct and that when the plane at the duct exit is considered to be a plane of symmetry. However, the intensity is different because of the wave propagation into the duct and is dependent on the location of the source.

Ting, L.↗
NASA NTRS1979

Frontal systems during passage of the Martian north polar hood over the Viking Lander 2 site prior to the first 1977 dust storm

Analysis of a 12-sol period of wind speed, wind direction, temperature, pressure, and optical depth at the Viking Lander 2 site presents the first in situ evidence of high- and low-pressure systems, complete with fronts, on the surface of Mars. The discovery of these systems in the Lander data occurred while analyzing a period during which the north polar hood was advected over the site at midday, dramatically decreasing the surface illumination and surface-to-atmospheric heat flux. This obscuration immediately preceded a global dust storm in the southern hemisphere and low latitudes of the northern hemisphere. The direct effects of the dust storm, reached 48 N, the Lander 2 latitude, later more gradually than they reached the 22 deg N latitude of Lander 1. The system responsible for the polar hood passages is a major disturbance, and it appears that radiational damping is inadequate to stop strong frontal formation. The front analyzed is characteristic of a repetitive series of systems that pass roughly every 3.3 sols. These systems are similar to those predicted by theoretical analyses and by general circulation modeling of the Martian atmosphere and those observed in laboratory experiments.

Tillman, J. E.↗
NASA NTRS1980

Electric propulsion for near-Earth space missions

A set of missions was postulated that was considered to be representative of those likely to be desirable/feasible over the next three decades. The characteristics of these missions, and their payloads, that most impact the choice/design of the requisite propulsion system were determined. A system-level model of the near-Earth transportation process was constructed, which incorporated these mission/system characteristics, as well as the fundamental parameters describing the technology/performance of an ion bombardment based electric propulsion system. The model was used for sensitivity studies to determine the interactions between the technology descriptors and program costs, and to establish the most cost-effective directions for technology advancement. The most important factor was seen to be the costs associated with the duration of the mission, and this in turn makes the development of advanced electric propulsion systems having moderate to high efficiencies ( 50 percent) at intermediate ranges of specific impulse (approximately 1000 seconds) very desirable.

Terwilliger, C. H.↗
NASA NTRS1979

Viking relativity experiment - Verification of signal retardation by solar gravity

Analysis of 14 months of data obtained from radio ranging to the Viking spacecraft verified, to an estimated accuracy of 0.1%, the prediction of the general theory of relativity that the round-trip times of light signals traveling between the earth and Mars are increased by the direct effect of solar gravity. The corresponding value for the metric parameter gamma is 1.000 plus or minus 0.002, where the quoted uncertainty, twice the formal standard deviation, allows for possible systematic errors.

Reasenberg, R. D.↗