Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Thermal experience”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The observation of damage regions produced by neutron irradiation in lithium-doped silicon solar cells.

Study regions of lattice disorder produced in lithium-doped float-zone melted n/p-type silicon solar cells by irradiation with monoenergetic neutrons at doses between 10 to the 10th and 10 to the 13th per cu cm. The defect regions were revealed by chemically etching the surface of the solar cells and by observing carbon replicas in an electron microscope. It was found that the defect density increased with increasing irradiation dose and increased lithium content, whereas the average defect diameter was found to decrease. From thermal annealing experiments it was found that in the lithium-doped material the defect structure was stable at temperatures between 300 and 1200 K. This was found to be in contrast to the undoped material where at the lowest doses considerable annealing was observed to occur. These results are discussed in terms of the theoretical predictions and models of defect clusters proposed by Gossick (1959) and Crawford and Cleland (1959).

Ghosh, S.↗
NASA NTRS1974

The science of the Viking missions

The Viking missions involve the launching of two identical spacecraft in the summer of 1975. Each spacecraft consists of a Lander and an Orbiter combination. The initial deceleration of the Lander during its descent to the Martian surface will be caused by aerodynamic drag. At about 5 km above the surface, a parachute is deployed. At 2 km three retrorockets are fired. The investigations to be conducted are discussed, giving attention to studies of the Martian surface with the aid of TV cameras, water mapping with an IR spectrometer, a thermal mapping experiment, studies of the Martian atmosphere, investigations conducted with a surface sampler, the search for life, and studies of the Martian surface composition.

Soffen, G. A.↗
NASA NTRS1976

Diffusion artifacts in dating by stepwise thermal release of rare gases

It is demonstrated that the age of an isochron of apparent age plateau can be easily altered during a thermal release experiment, and that constant rare gas compositions can be observed which are artifacts of the experimental technique and are not chronologically meaningful. Examples are selected from 40Ar-39Ar dating of lunar samples in which anomalous variations in apparent ages can be ascribed to such experimental artifacts.

Huneke, J. C.↗
NASA NTRS1978

Thermal resistance of naturally occurring airborne bacterial spores

Simulation of a heat process used in the terminal dry-heat decontamination of the Viking spacecraft is reported. Naturally occurring airborne bacterial spores were collected on Teflon ribbons in selected spacecraft assembly areas and subsequently subjected to dry heat. Thermal inactivation experiments were conducted at 105, 111.7, 120, 125, 130, and 135 C with a moisture level of 1.2 mg of water per liter. Heat survivors were recovered at temperatures of 135 C when a 30-h heating cycle was employed. Survivors were recovered from all cycles studied and randomly selected for identification. The naturally occurring spore population was reduced an average of 2.2 to 4.4 log cycles from 105 to 135 C. Heating cycles of 5 and 15 h at temperature were compared with the standard 30-h cycle at 111.7, 120, and 125 C. No significant differences in inactivation (alpha = 0.05) were observed between 111.7 and 120 C. The 30-h cycle differs from the 5- and 15-h cycles at 125 C. Thus, the heating cycle can be reduced if a small fraction (about 0.001 to 0.0001) of very resistant spores can be tolerated.

Puleo, J. R.↗
NASA NTRS1979

Electron Radiation Damage of (alga) As-gaas Solar Cells

Solar cells (2 cm by 2 cm (AlGa) As-GaAs cells) were fabricated and then subjected to irradiation at normal incidence by electrons. The influence of junction depth and n-type buffer layer doping level on the cell's resistance to radiation damage was investigated. The study shows that (1) a 0.3 micrometer deep junction results in lower damage to the cells than does a 0.5 micrometer junction, and (2) lowering the n buffer layer doping density does not improve the radiation resistance of the cell. Rather, lowering the doping density decreases the solar cell's open circuit voltage. Some preliminary thermal annealing experiments in vacuum were performed on the (AlGa)As-GaAs solar cells damaged by 1-MeV electron irradiation. The results show that cell performance can be expected to partially recover at 200 C with more rapid and complete recovery occurring at higher temperature. For a 0.5hr anneal at 400 C, 90% of the initial power is recovered. The characteristics of the (AlGa)As-GaAs cells both before and after irradiation are described.

Loo, R.↗
NASA NTRS1980

Solar thermal power systems point-focusing thermal and electric applications projects. Volume 1: Executive summary

The activities of the Point-Focusing Thermal and Electric Applications (PETEA) project for the fiscal year 1979 are summarized. The main thrust of the PFTEA Project, the small community solar thermal power experiment, was completed. Concept definition studies included a small central receiver approach, a point-focusing distributed receiver system with central power generation, and a point-focusing distributed receiver concept with distributed power generation. The first experiment in the Isolated Application Series was initiated. Planning for the third engineering experiment series, which addresses the industrial market sector, was also initiated. In addition to the experiment-related activities, several contracts to industry were let and studies were conducted to explore the market potential for point-focusing distributed receiver (PFDR) systems. System analysis studies were completed that looked at PFDR technology relative to other small power system technology candidates for the utility market sector.

Marriott, A.↗
NASA NTRS1981

Development of the small community solar power system

The status of the Small Community Solar Thermal Power Experiment is presented. Activities on the Phase 2 single/module development effort are presented, together with plans for the Phase 3 1 MWe demonstration plant. A description of the various subsystems and components is given with emphasis on the unmanned microprocessor based plant control subsystem. Latest performance figures are given for the 1 MWe plant, based on 56 power modules, each consisting of a 12m low cost concentrator, a cavity receiver, a Rankine power conversion subsystem and a ground mounted solid-state rectifier. Overall plant efficiency at rated conditions is 15.8 percent. Advanced glass concentrator designs yield 20 percent overall efficiencies.

Babbe, R. H.↗
NASA NTRS1981

Infrared-temperature variability in a large agricultural field

Dunnigan Agro-Meteorological Experiment airborne thermal scanner images of a large varying-terrain barley field are acquired and analyzed. Temperature variability that may occur within instantaneous fields of view (IFOV) is defined (coefficient of variation: standard deviation/mean temperature in degrees C), and the percentage of the area within various IFOV's within + or - 1, 2, 3, and 5 degrees of the mean is determined. With the exception of very rugged terrain, over 80% of the area within 4, 16, 65 and 258 ha cells was at temperatures within + or - 3 C of the mean cell temperature. Remote measurements of field temperature appeared to be slightly influenced by pixel size in the range 4 ha to 259 ha, and the area percentage within any pixel which contributes within + or - 1, 2, 3, and 5 degrees C of the mean, is nominally the same. In conclusion, no great advantage is found in utilizing a small IFOV instead of a large one for remote sensing of crop temperature.

Millard, J. P.↗
NASA NTRS1981

Pressure-Reduction Technique for Crystal Growth

Large crystals grown by varying pressure rather than temperature. In constant temerature pressure-reduction process crystal growth promoted as solubility decreases by factor of more than 10. Technique used to study crystal growth kinetics by "pressure wave"" analog of conventional "thermal wave" experiments. Technique has advantages of faster response and freedom from convective interference.

Shlichta, P. J.↗
NASA NTRS1982

Development status of the small community solar power system

The development status and test results for the Small Community Solar Thermal Power Experiment are presented. Activities on the phase 2 power module development effort are presented with emphasis on the receiver, the plant control subsystem, and the energy transport subsystem. The components include a single prototype power module consisting of a parabolic dish concentrator, a power conversion assembly (PCA), and a multiple-module plant control subsystem. The PCA consists of a cavity receiver coupled to an organic Rankine cycle engine-alternator unit defined as the power conversion subsystem; the PCA is mounted at the focus of a parabolic dish concentrator. At a solar insolation of 100 W/sq m and ambient temperature of 28 C (82 F), the power module produces approximately 20 kW of 3-phase, 3 kHz ac power, depending on the concentrator employed. A ground-mounted rectifier to the central collection site where it is supplied directly to the common dc bus which collects the power from all modules in the plant.

Pons, R. L.↗
NASA NTRS1982

Recent tests on the Carter small reciprocating steam engines

The Jay Carter Enterprises (JCE) Paratransit Vehicle steam engine was tested over a range of conditions which might be experienced by the power converter subsystem of the Small Community Solar Thermal Power Experiment. Some difficulties were encountered getting the engine ready for testing. These difficulties were related to the five year dormancy of the entire system and to incomplete development work that had been going on at the time of cessation of steam engine work at JCE. Other difficulties were related to the fact that the particular expander being tested never ran before and possessed some manufacturing defects. Nevertheless, the engine was operated successfully and results of testing do verify results of computer simulations of the engine in regard to the effect of temperature and power level variations. Engine efficiency was good but generally lower than expected and performance dropped as testing continued. The effect of change in expansion ratio was not demonstrated because of deterioration in engine performance. Post-test inspection revealed numerous correctable defects.

Kiceniuk, T.↗
NASA NTRS1983

OSS-1 - A pathfinder mission for space science on Shuttle

On the third Shuttle flight (STS-3), the Orbiter carried a payload of nine scientific instruments. The payload was designated OSS-1 because the program was originaly managed by the Office of Space Science. The OSS-1 objectives are discussed, taking into account the Plasma Diagnostics Package, a study concerned with vehicle charging and potential, the Thermal Canister Experiment, the Solar Flare X-ray Polarimeter, the Solar Ultraviolet Spectral Irradiance Monitor, the study of the influence of weightlessness on lignification in developing plant seedlings, the Microabrasion Foil Experiment, the Contamination Monitor Package, and a study of the characteristics of the Shuttle/Spacelab induced atmosphere. The OSS-1 payload was launched on STS-3 on March 22, 1982.

Neupert, W. M.↗
NASA NTRS1984

Defect studies in one MeV electron irradiated GaAs and in Al/sub x Ga/sub l-x As P-N junction solar cells

Deep level transient spectroscopy reveals that the main electron traps for one-MeV electron irradiated GaAs cells are E9c)-0.31, E(c)-0.90 eV, and the main hole trap is due to the level. Electron trap density was found to vary from 3/tens-trillion ccm for 2/one quadrillion cm 3/3.7 quadrillion cm for 21 sextillion cm electron fluence for electron fluence; a similar result was also obtained for the hole trap density. As for the grown-in defects in the Al(x)Ga(1-x)As p-n junciton cells, only two electron traps with energies of E(c)-0.20 and E(c)-0.34 eV were observed in samples with x = 0.17, and none was found for x 0.05. Auger analysis on the Al(x)Ga(1-x) As window layer of the GaAs solar cell showed a large amount of oxygen and carbon contaminants near the surface of the AlGaAs epilayer. Thermal annealing experiment performed at 250 C for up to 100 min. showed a reduction in the density of both electron traps.

Li, S. S.↗
NASA NTRS1984

Thermal metamorphism of Si2O3 - (A circumstellar dust analog)

The thermal behavior of Si2O3, the metastable condensate from SiO vapor,has been studied experimentally. Si2O3 and its successor, amorphous quartz, have previously been shown to have infrared spectral features similar to some that appear in the spectra of grains in oxygen-rich circumstellar regions. Thermal annealing experiments show that only one Si2O3 decay process operates over the range between 750-1000 K. This process is a unimolecular disproportionation. The rate of this transformation can be expressed as k/hr = 10 to the 9th exp (-40 kcal/mole/RT). By using this rate constant, it is found that a significant fraction of freshly nucleated circumstellar grains can survive passage through a typical circumstellar shell virtually unaltered in structure. It is emphasized that this is only the first in a series of laboratory experiments intended to study the metamorphism of newly condensed circumstellar material ejected into the interstellar medium. Grains similar to these might have been incorporated into the primitive solar nebula, provided that they could also survive passage through the general interstellar medium.

Nuth, J. A.↗
NASA NTRS1984

Validation of water vapor results measured by the Limb Infrared Monitor of the Stratosphere experiment on Nimbus 7

In the LIMS experiment using thermal IR limb scanning to sound the composition and structure of the upper atmosphere, one of the LIMS channels was spectrally centered at 6.9 micrometers to measure the vertical profile and global distribution of stratospheric water vapor. This channel's characteristics, the data from it, and the steps taken to validate results are described. The mean difference between the LIMS measurements and data from 13 balloon underflights is about 0.6 ppmv with LIMS mixing ratios biased high; this difference is of about the same order as estimated LIMS accuracy and less than the sum of the errors for LIMS and the balloon techniques. In-orbit precision is 0.2-0.3 ppmv and accuracy is estimated at 20-30 percent from 50 mbar to the stratopause. An unexplained diurnal variation exists in the vertical profile data which is largest at the 1-mbar level and virtually nonexistent at 10 mbar; day values are higher than night. More confidence is placed in zonal mean distributions averaged over several days than in single profiles. A zonal mean pressure-latitude cross section is described for January 5-9, 1979.

Russell, J. M., III↗
NASA NTRS1984

High pressure cosmochemistry applied to major planetary interiors: Experimental studies

Progress is reported on a project to determine the properties and boundaries of high pressure phases of the H2-He-H2O-NH3-CH4 system that are needed to constrain theoretical models of the interiors of the major planets. This project is one of the first attempts to measure phase equilibria in binary fluid-solid systems in diamond anvil cells. Vibrational spectroscopy, direct visual observations, and X-ray diffraction crystallography of materials confined in externally heated cells are the primary experimental probes. Adiabats of these materials are also measured in order to constrain models of heat flow in these bodies and to detect phase transitions by thermal anomalies. Initial efforts involve the NH3-H2O binary. This system is especially relevant to models for surface reconstruction of the icy satellites of Jupiter and Saturn. Thermal analysis experiments were completed for the P-X space, p4GPa:0 or = 0.50, near room temperature. The cryostat, sample handling equipment, and optics needed to extend the optical P-T-X work below room temperature was completed.

Nicol, M. F.↗
NASA NTRS1985

Some observations of heated gallium arsenide heteroface solar cells

GaAlAs/GaAs heteroface solar cells used in space offer advantages of higher operating temperatures and recovery from radiation damage using thermal annealing. Experiments were conducted to examine the effects on the room temperature photovoltaic properties of cells due to heating in a vacuum at temperatures encountered in radiation damage annealing. Some degradation of photovoltaic properties was observed for all the cells that were heated. The lifetime, due to heating, for a 20-percent degradation in output power was estimated for cells heated at 200 C and 400 C. The results for cells that were heated at 200 C for 1750 hours indicate a lifetime of at least 3 years. The results for cells that were heated at 400 C for 264 hours indicate that lifetimes in the range of 350 hours to 1400 hours may be expected. The results indicate that for cells that must be heated at 400 C the selection of fabrication techniques and materials is particularly important.

Friesen, W. J.↗