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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Low-temperature Brayton radiator performance in a variable-sink-temperature environment

An analysis of the performance of a low-temperature Brayton space radiator is presented. The cylindrical radiator with circumferential tubes was subjected to an equivalent sink temperature environment that varied along the fluid flow path. The radiator performance, as measured by fluid outlet temperature, was found to be dependent on the orbital position and the location of the radiator inlet relative to the sink temperature environment. An approximate dynamic analysis of sun-shade variations in performance is included.

Bien, D. B.↗
NASA NTRS1972

Review of deformation behavior of tungsten at temperature less than 0.2 absolute melting temperature

The deformation behavior of tungsten at temperatures 0.2 T sub m is reviewed, with primary emphasis on the temperature dependence of the yield stress and the ductile-brittle transition temperature. It appears that a model based on the high Peierls stress of tungsten best accounts for the observed mechanical behavior at low temperatures. Recent research is discussed which suggests an important role of electron concentration and bonding on the mechanical behavior of tungsten. It is concluded that future research on tungsten should include studies to define more clearly the correlation between electron concentration and mechanical behavior of tungsten alloys and other transition metal alloys.

Stephens, J. R.↗
NASA NTRS1973

An efficient technique for determining apparent temperature distributions from antenna temperature measurements

A method by which the apparent microwave temperature characteristic of a flat scene is estimated from dual polarized measurements is derived and interpreted. Approximate linear relationships between antenna and apparent temperatures are established by weighting emission components in spherical bands under the assumption that the surface is isotropic. The weighting factors are formed by integrating the antenna pattern functions over these bands. The vector aspect of the formulation is retained to account for the difference between the definition of the antenna polarizations and the polarizations of the emitted fields. The method is largely applicable to the measurement of smooth temperature distributions by an antenna having good spatial resolution of the distributions and is considered efficient for inverting large volumes of measurements. Sample cases are presented and the implications of these cases on remote radiometer observations are discussed. It is shown that cross-coupling occurs between the polarizations of the emitted fields and the polarizations of the antenna. For this reason and because practical antennas have cross-polarized patterns associated with them, it is necessary to conduct measurements at both horizontal and vertical polarizations to realize the inversion. It is also made evident that thorough inversions require that the apparent temperatures be sampled at a sufficient number of points between nadir and zenith.

Claassen, J. P.↗
NASA NTRS1974

Experimental transient vane temperatures in a cascade for gas stream temperature cycling between 922 and 1644 K (1200 and 2500 F)

Experimental transient turbine vane metal temperatures were obtained from tests conducted on air-cooled vanes installed in a four-vane cascade for a gas temperature cycled between 922 and 1644 K (1200 and 2500 F). Transient data were recorded by a high-speed data acquisition system. Temperatures at the same phase of each transient cycle were repeatable between cycles to within 11 kelvins (20 F), simulated cruise and idle steady-state readings were repeated by the cruise and idle readings taken from the ends of a transient half-cycle at low pressure to within 17 kelvins (30 F). The tests were conducted at pressure levels of 31 and 83 N-sq cm (45 and 120 psia) with coolant temperatures of 811 and 589 K (1000 and 600 F), respectively.

Gauntner, D. J.↗
NASA NTRS1975

Experimental transient turbine blade temperatures in a research engine for gas stream temperatures cycling between 1067 and 1567 k

Experimental transient turbine blade temperatures were obtained from tests conducted on air-cooled blades in a research turbojet engine, cycling between cruise and idle conditions. Transient data were recorded by a high speed data acquisition system. Temperatures at the same phase of each transient cycle were repeatable between cycles to within 3.9 K (7 F). Turbine inlet pressures were repeatable between cycles to within 0.32 N/sq cm (0.47 psia). The tests were conducted at a gas stream temperature of 1567 K (2360 F) at cruise, and 1067 K (1460 F) at idle conditions. The corresponding gas stream pressures were about 26.2 and 22.4 N/sq cm (38 and 32.5 psia) respectively. The nominal coolant inlet temperature was about 811 K (1000 F).

Gauntner, D. J.↗
NASA NTRS1976

Sensitivity of surface temperature and atmospheric temperature to perturbations in the stratospheric concentration of ozone and nitrogen dioxide

A radiative-convective model is proposed for estimating the sensitivity of the atmospheric radiative heating rates and atmospheric and surface temperatures to perturbations in the concentration of O3 and NO2 in the stratosphere. Contribution to radiative energy transfer within the atmosphere from H2O, CO2, O3, and NO2 is considered. It is found that the net solar radiation absorbed by the earth-atmosphere system decreases with a reduction in O3; if the reduction of O3 is accompanied by an increase in NO2, there is a compensating effect due to solar absorption by NO2. The surface temperature and atmospheric temperature decrease with decreasing stratospheric O3. Another major conclusion is the strong sensitivity of surface temperature to the vertical distribution of O3 within the atmosphere. The results should be considered as reflecting the sensitivity of the proposed model rather than the sensitivity of the actual earth-atmosphere system.

Ramanathan, V.↗
NASA NTRS1977

On coronal temperatures, temperature gradients and compositions

Average solar wind properties at 1 AU either alone or together with the electron density distribution are used to obtain or review some results that relate coronal temperatures, temperature gradients, and compositions. Measured values of the temperature (T) and the temperature gradient parameter are used to find compositions that satisfy the equations used to obtain the results. The total energy equation may be satisfied if the thermal conductivity is reduced by considerable depletions of H(+) in the corona. The hydrostatic approximation (momentum equation) for the electron density distribution appears to require considerable depletions of H(+) in the corona.

Nakada, M. P.↗
NASA NTRS1977

Effect of altered gravity on temperature regulation in mammals: Investigation of gravity effect on temperature regulation in mammals

Male, Long-Evans hooded rats were instrumented for monitoring core and hypothalamic temperatures as well as shivering and nonshivering thermogenesis in response to decreased ambient temperature in order to characterize the nature of the neural controller of temperature in rats at 1G and evaluate chronic implantation techniques for the monitoring of appropriate parameters at hypergravic fields. The thermoregulatory responses of cold-exposed rats at 2G were compared to those at 1G. A computer model was developed to simulate the thermoregulatory system in the rat. Observations at 1 and 2G were extended to acceleration fields of 1.5, 3.0 and 4.0G and the computer model was modified for application to altered gravity conditions. Changes in the acceleration field resulted in inadequate heat generation rather than increased heat loss. Acceleration appears to impair the ability of the neurocontroller to appropriately integrate input signals for body temperature maintenance.

Horwitz, B. A.↗
NASA NTRS1978

Traction and lubricant film temperature as related to the glass transition temperature and solidification

Does a traction fluid have to be a glass or solid under operating conditions. Infrared spectra on dynamic EHD contacts of several types of fluid were used to determine the surface and oil-film temperatures. Polarized spectral runs were made to study molecular alignment. Static glass transition pressures at appropriate temperatures were between 0.1 and 2.0 GPa, with the traction fluid showing the highest. In the EHD contact region, the traction fluid showed both the highest film temperatures as well as the greatest degree of molecular alignment. A plot of the difference between the film and surface temperatures vs shear rate resulted in a master plot valid for all the fluids. From this work, the authors propose a model of 'fluid' traction, where friction between parallel rough molecules provides the traction.

Lauer, J. L.↗
NASA NTRS1979

Electron temperatures and densities in the Venus ionosphere - Pioneer Venus orbiter electron temperature probe results

The Pioneer Venus orbiter electron temperature probe was used to obtain altitude profiles of electron temperature and density in the ionosphere of Venus. Elevated temperatures at times of low solar wind flux might indicate support for a certain model. According to this model, less than 5% of the solar wind energy is deposited at the ionopause and is conducted downward through an unmagnetized ionosphere to the region below 200 km where electron cooling to the neutral atmosphere proceeds rapidly. The patterns of electron temperatures and densities at higher solar wind fluxes are considered, the variability of the ionopause height in the late afternoon is noted, and the role of an induced magnetic barrier in the neighborhood of the ionopause is discussed.

Brace, L. H.↗
NASA NTRS1980

The upper atmosphere of Uranus - Mean temperature and temperature variations

The number-density, pressure, and temperature profiles of the Uranian atmosphere in the pressure interval from 0.3 to 30 dynes/sq cm are derived from observations of the occultation of SAO 158687 by Uranus on 1977 March 10, observations made from the Kuiper Airborne Observatory and the Cape Town station of the South African Astronomical Observatory. The mean temperature is found to be about 95 K, but peak-to-peak variations from 10 K to 20 K or more exist on a scale of 150 km or 3 scale heights. The existence of a thermal inversion is established, but the inversion is much weaker than the analogous inversion on Neptune. The mean temperature can be explained by solar heating in the 3.3 micron methane band with a methane mixing ratio of 4 x 10 to the -6th combined with the cooling effect of ethane with a mixing ratio of not greater than 4 x 10 to the -6th. The temperature variations are probably due to a photochemical process that has formed a Chapman layer.

Dunham, E.↗
NASA NTRS1981

Atmospheric carbon dioxide and chlorofluoromethanes - Combined effects on stratospheric ozone, temperature, and surface temperature

The effects of combined CO2 and CFCl3 and CF2Cl2 time-dependent scenarios on atmospheric O3 and temperature are described; the steady-state levels of O3 and surface temperature, to which the chlorofluoromethane scenario tends in the presence of twice and four time ambient CO2, are examined; and surface temperature changes, caused by the combined effects, are established. A description of the model and of the experiments is presented. Results indicate that (1) the total ozone time history is significantly different from that due to the chlorofluoromethane alone; (2) a local ozone minimum occurs in the upper stratosphere about 45 years from the present with a subsequent ozone increase, then decline; and (3) steady-state solutions indicate that tropospheric temperature and water vapor increases, associated with increased infrared opacity, cause significant changes in tropospheric ozone levels for 2 x CO2 and 4 x CO2, without the addition of chlorofluoromethanes.

Callis, L. B.↗
NASA NTRS1983

Comparison of winter-nocturnal geostationary satellite infrared-surface temperature with shelter-height temperature in Florida

Geostationary satellite surface temperatures derived from a Visible and Infrared Spin Scan Radiometer (VISSR) sensor (10.5 to 12.6 microns) were compared with 1.5-m air temperatures collected by a thermocouple on a traversing vehicle along rural highway transects in Florida, and with two fixed thermographs located in rural and agricultural areas. Statistical comparisons between satellite and 1.5-m observations yielded a mean correlation coefficient of 0.87 and an average sample standard deviation from regression of 1.57 C during clear nights for four winters (1978-1981). The satellite-temperature image of Lake Okeechobee was compared with its geographic outline for areal image registration. Manual overlays of temporal images were repeatable to within one pixel. Satellite-sensed water temperature of Lake Okeechobee was used as an indicator of satellite radiometer repeatability and stability.

Chen, E.↗
NASA NTRS1989

High-Temperature Strain-And-Temperature Gauge

Two-element gauge used alternately in two different bridge circuits to measure both temperature and strain. Three-lead strain-and-temperature gauge developed for use at temperatures up to 750 degree F (390 degree C) on fiber-reinforced carbon/carbon composite material having coefficient of thermal expansion of 0.8 ppm/degree F. Unlike most temperature-compensated gauges, gauge gives accurate results even during rapid heating and cooling cycles. Similar gauges produced for materials with different coefficients of thermal expansion.

Wnuk, S. P.↗
NASA NTRS1990

The temperature scale of hot DA white dwarfs - Temperatures from far-ultraviolet continuum fluxes

Observed far-UV to visible flux ratios of all DA white dwarfs hotter than about 25,000 K are compared with ratios predicted by models in order to derive effective temperatures for the stars. All suitable IUE spectra of seven hot DA white dwarfs for which accurate temperatures based on hydrogen line profiles were available are used to derive a flux correction to the 1980 IUE absolute calibration. Application of the corrections to the IUE spectra results in derived temperature which are consistent with the line profile temperatures.

Finley, David S.↗
NASA NTRS1992

Sodium Doppler Temperature Lidar Observations of the Mesopause Region Temperature and Wind Structure

Measurements of the mesopause region temperature structure are being routinely conducted at Urbana, Illinois with the University of Illinois (UIUC) Sodium Doppler Temperature Lidar. The first measurements were taken with this system in Jan. 1991 and are now being made, and will soon be done routinely in conjunction with the temperature measurements. The results obtained with the UIUC Sodium Doppler Temperature Lidar (SDTL) are presented. A description of the system is given in accompanying articles.

Senft, Daniel C.↗
NASA NTRS1994

Experiment K-7-35: Circadian Rhythms and Temperature Regulation During Spaceflight: Circadian Rhythms and Temperature Regulation - Part 1

Mammals have developed the ability to adapt to most variations encountered in their everyday environment. For example, homeotherms have developed the ability to maintain the internal cellular environment at a relatively constant temperature. Also, in order to compensate for temporal variations in the terrestrial environment, the circadian timing system has evolved. However, throughout the evolution of life on earth, living organisms have been exposed to the influence of an unvarying level of earth's gravity. As a result changes in gravity produce adaptive responses which are not completely understood. In particular, spaceflight has pronounced effects on various physiological and behavioral systems. Such systems include body temperature regulation and circadian rhythms. This program has examined the influence of microgravity on temperature regulation and circadian timekeeping systems in Rhesus monkeys. Animals flown on the Soviet Biosatellite, COSMOS 2044, were exposed to 14 days of microgravity while constantly monitoring the circadian patterns temperature regulation, heart rate and activity. This experiment has extended our previous observations from COSMOS 1514, as well as providing insights into the physiological mechanisms that produce these changes.

Fuller, C. A.↗
NASA NTRS1999

Temperature Compensated Sapphire Resonator for Ultrastable Oscillator Operating at Temperatures Near 77 Deg Kelvin

A sapphire resonator for an ultrastable oscillator capable of substantial performance improvements over the best available crystal quartz oscillators in a compact cryogenic package is based on a compensation mechanism enabled by the difference between copper and sapphire thermal expansion coefficients for so tuning the resonator as to cancel the temperature variation of the sapphire's dielectric constant. The sapphire resonator consists of a sapphire ring separated into two parts with webs on the outer end of each to form two re-entrant parts which are separated by a copper post. The re-entrant parts are bonded to the post by indium solder for good thermal conductivity between parts of that subassembly which is supported on the base plate of a closed copper cylinder (rf shielding casing) by a thin stainless steel cylinder. A unit for temperature control is placed in the stainless steel cylinder and is connected to the subassembly of re-entrant parts and copper post by a layer of indium for good thermal conduction. In normal use, the rf shielding casing is placed in a vacuum tank which is in turn placed in a thermos flask of liquid nitrogen. The temperature regulator is controlled from outside the thermos flask to a temperature in a range of about 40K to 150K, such as 87K for the WGH-811, mode of resonance in response to microwave energy inserted into the rf shielding casing through a port from an outside source.

Dick, G. John↗