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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 487 records · Page 27

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NASA NTRS1974

Effect of electron beam pulse width on time-of-flight spectra

A simple but useful formula describing the effect of electron gun pulse width on the time of flight (TOF) spectra measured in translational spectroscopy experiments is developed. An approximately monoenergetic pulsed electrostatically focused electron beam traverses a scattering cell filled with a Maxwellian gas. Inelastic electron collisions with the gas produce metastable particles, ions, scattered electrons, and photons which then pass through a collimating slit system at right angles to the electron beam. TOF techniques are used to separate the photon signal from the metastable particle signal and to measure the TOF distribution of the metastable species.

Misakian, M.↗

NASA NTRS1974

Study of radar pulse compression for high resolution satellite altimetry

Pulse compression techniques are studied which are applicable to a satellite altimeter having a topographic resolution of + 10 cm. A systematic design procedure is used to determine the system parameters. The performance of an optimum, maximum likelihood processor is analysed, which provides the basis for modifying the standard split-gate tracker to achieve improved performance. Bandwidth considerations lead to the recommendation of a full deramp STRETCH pulse compression technique followed by an analog filter bank to separate range returns. The implementation of the recommended technique is examined.

Dooley, R. P.↗

NASA NTRS1974

The aerothermal environment and material response: A review

Aerothermal environments are discussed with emphasis on the cold dense and warm atmospheres of Saturn and Uranus. The spectral distribution of the incident radiation flux is given for the Saturn nominal entry. Saturn and Uranus stagnation point heat pulses with no ablation are compared. Calculations for small flow rates, important in the Saturn-Uranus nominal type entries, are given to investigate the effects due to the mixing layer separation. Analytical and experimental techniques applicable to flowfield calculations are reviewed with emphasis on two--dimensional flow capabilities. Transport properties are reviewed in terms of flowfield calculations along with radiation transport codes. Various approaches to entry calculations are presented. It is indicated that only certain aspects of the aerothermal environment can be simulated in the laboratory and that although flight experiments are becoming feasible they are so expensive that they are prohibitive. Recommendations for further study are included.

Nicolet, W. E.↗

NASA NTRS1974

Recent wake turbulence flight test programs

In early flight tests the size and intensity of the wake vortexes generated by aircraft ranging in size from the Learjet to the C-5A and the B-747 were studied to determine the effects of aircraft configuration, weight, and speed. Early problems were related to vortex marking, the measurement of separation distance, and test techniques. Recent tests conducted with B-747 showed that vortexes were alleviated by reducing the deflection of the outboard flaps. It was found that a more rapid dissipation of the vortex system can be obtained through alterations in the span lift distribution.

Tymczyszyn, J. J.↗

NASA NTRS1974

Apollo 17 1-2 mm fines - Mineralogy and petrology

Nine 1-2 mm Apollo 17 soil samples from the South Massif and the Sculptured Hills are examined using petrographic and microprobe techniques. Each soil was separated into six groupings based on macroscopic features observed under a stereomicroscope. The groups and their characteristics are described. Minor differences observed include a higher content of fine-grained, dark, friable breccia and a higher content of high-Mg mafic-bearing fragments in the Sculptured Hills soils. The olivine and pyroxene compositions for light breccia from the soil samples are summarized. During the soil examination, several distinctive fragments seen include coarse orthopyroxene-plagioclase fragments with diopside-rich veins, a plagioclase-forsterite fragment with an igneous texture and a pyroxene-plagioclase fragment with isotropic, subhedral plagioclase grains.

Steele, I. M.↗

NASA NTRS1977

Low cost silicon solar array project silicon materials task

A program was established to develop a high temperature silicon production process using existing electric arc heater technology. Silicon tetrachloride and a reductant will be injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction is expected to occur and proceed essentially to completion, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection of the molten silicon will be developed using standard engineering approaches, and the salt vapor will later be electrolytically separated into its elemental constituents for recycle. Preliminary technical evaluations and economic projections indicate not only that this process appears to be feasible, but that it also has the advantages of rapid, high capacity production of good quality molten silicon at a nominal cost.

Source record↗

NASA NTRS1979

Supercritical flow about a thick circular-arc airfoil

The supercritical flow about a biconvex circular-arc airfoil is being thoroughly documented at Ames Research Center in order to provide experimental test cases suitable for guiding and evaluating current and future computer codes. The effects of angle of attack, effects of leading and trailing-edge splitter plates, additional unsteady pressure fluctuation (buffeting) measurements and glow-field shadowgraphs, and application of an oil-film technique to display separated-wake streamlines were studied. Computed and measured pressure distributions for steady and unsteady flows, using a recent computer code representative of current methodology, are compared. It was found that the numerical solutions are often fundamentally incorrect in that only strong (shock-polar terminology) shocks are captured, whereas experimentally, both strong and weak shock waves appear.

Mcdevitt, J. B.↗

NASA NTRS1980

Bandwidth compression of color video signals

The different encoder/decoder strategies to digitally encode video using an adaptive delta modulation are described. The techniques employed are: (1) separately encoding the R, G, and B components; (2) separately encoding the I, Y, and Q components; and (3) encoding the picture in a line sequential manner.

Schilling, D. L.↗

NASA NTRS1980

Development of a process for high capacity arc heater production of silicon for solar arrays

A high temperature silicon production process using existing electric arc heater technology is discussed. Silicon tetrachloride and a reductant, liquid sodium, were injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction occurred, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection of the molten silicon were developed. The desired degree of separation was not achieved. The electrical, control and instrumentation, cooling water, gas, SiCl4, and sodium systems are discussed. The plasma reactor, silicon collection, effluent disposal, the gas burnoff stack, and decontamination and safety are also discussed. Procedure manuals, shakedown testing, data acquisition and analysis, product characterization, disassembly and decontamination, and component evaluation are reviewed.

Meyer, T. N.↗

NASA NTRS1981

Electrorefining process for lunar free metal - Space and terrestrial applications and implications

An electrochemical refining process is proposed for the separation and recovery of principal and trace elements from reduced metallic particles found in lunar soils. A process variation is presented for purification and recovery of chromium and manganese from electrodeposited impure iron available from lunar silicate and other minerals. The process involves anodic dissolution of impure metal and cathodic deposition in divided cells using aqueous chloride solutions. The anolyte is withdrawn and separated using ion exchange techniques.

Waldron, R. D.↗

NASA NTRS1983

Chlorophyll and carotenoid pigments of prochloron (prochlorophyta)

High-performance liquid chromatography (HPLC) with a gradient-elution technique was utilized to separate and quantify chlorophylls a and b as well as major carotenoid pigments present in freeze-dried preprations of prochloron-didemnid associations and in Prochloron cells separated from host colonies. Results confirm earlier spectrophotometric evidence for both chlorophylls a and b in this prokaryote. Chlorophyll a:b ratios range from 4.14 to 19.71; generally good agreement was found between ratios determined in isolated cell preprations and in symbiotic colonies (in hospite). These values are 1.5 to 5-fold higher than ratios determined in a variety of eukaryotic green plants. The carotenoids in Prochloron are quantitatively and qualitatively similar to those found in various freshwater and marine blue-green algae (cyanopbytes) from high-light environments. However, Prochloron differs from cyanophytes by the absence of myxoxanthophyll and related glycosidic carotenoids. It pigment characteristics are considered sufficiently different from those of cyanophytes to justify its assignment to a separate algal division.

Paerl, H. W.↗

NASA NTRS1984

Comparison of Land Cover Information from LANDSAT Multispectral Scanner (MSS) and Airborne Thematic Mapper Simulator (TMS) Data for Hydrologic Applications

Detailed land cover classifications were performed on the Thematic Mapper Simulator (TMS) and MSS data of the Clinton River Basin (acquired on August 19, 1981, and June 28, 1980, respectively) using supervised classification techniques. Differences in interclass separability were compared to select several promising TMS band combinations, selected from the 27 covering the Clinton River Basin. The TMS data produced a more accurate and spatially contiguous classification than MSS for this study site. While the accuracy of the 4-band TM data set was as good as the 7-band, the 3-band TMS data sets were also better than the MSS. These results indicate that both the increased spectral discrimination and spatial resolution contribute to improved classification accuracy. The possibility of reducing the data analysis burden associated with large TM data volumes through effective band selection therefore appears promising. The implications of the improved classification accuracy of TMS data are important for hydrologic and economic modeling. In particular, the higher accuracies for the developed categories (residential and commercial) should improve the predictions of runoff in flood forecasting models and of flood damage for damage calculation models appreciably.

Gervin, J. C.↗

NASA NTRS1985

A Concept for the Processing and Display of Thematic Mapper Data

The thematic mapper system provides spectral information in seven carefully selected spectral bands. The challenge is to devise the best approach for presenting this complex spectral information in a pictorial format which can be understood and accepted as a standard by the growing user community. For photointerpretation purposes, the overall approach in the processing of multispectral, and especially of Thematic Mapper data is based on the Independent definition and optimization of individual panchromatic and spectral (interpretive) components and the combined display of these individual interpretive components in a perceivable manner. Processing of the Thematic Mapper data within the framework of interpretive components requires the application of special intensity, hue, saturation (IHS) and synthetic stereo (SST) display techniques. The results to date using these techniques demonstrate improved visual separability of spectral surface categories relative to standard multispectral color composites as well as a greater potential for conducting meaningful spectral-diagnostic analysis.

Haydn, R.↗

NASA NTRS1985

Gas chromatography: Possible application of advanced instrumentation developed for solar system exploration to space station cabin atmospheres

Gas chromatography (GC) technology was developed for flight experiments in solar system exploration. The GC is a powerful analytical technique with simple devices separating individual components from complex mixtures to make very sensitive quantitative and qualitative measurements. It monitors samples containing mixtures of fixed gases and volatile organic molecules. The GC was used on the Viking mission in support of life detection experiments and on the Pioneer Venus Large Probe to determine the composition of the venusian atmosphere. A flight GC is under development to study the progress and extent of STS astronaut denitrogenation prior to extravehicular activity. Advanced flight GC concepts and systems for future solar system exploration are also studied. Studies include miniature ionization detectors and associated control systems capable of detecting from ppb up to 100% concentration levels. Further miniaturization is investigated using photolithography and controlled chemical etching in silicon wafers. Novel concepts such as ion mobility drift spectroscopy and multiplex gas chromatography are also developed for future flight experiments. These powerful analytical concepts and associated hardware are ideal for the monitoring of cabin atmospheres containing potentially dangerous volatile compounds.

Carle, G. C.↗

NASA NTRS1986

Method for producing tetraphenoxide-n-aniloxy cyclo phosphazotriene

A method for producing tetraphenoxide-n-aniloxy cyclophosphazotriene, distinguished by the fact that tetraphenoxide dichlorocyclophosphazotriene is processed with an alkaline metal n-acetamidophenolate in an organic solvent, for example pyridine, during heating, after which the resulting compound is saponified in the present of a mineral or organic acid, for example, hydrochloric, and the desired product separated by well known techniques.

Khofbauer, Y. I.↗

NASA NTRS1986

Solar cycle variations of anomalous He-4 as deduced by studies of cosmic ray He-3

Voyager 1 and 2 observations have been used to derive the energy spectrum of 'anomalous' cosmic-ray (ACR) He using a technique based on the separation of the isotopes of He. Previously reported observations show that the ACR oxygen spectrum underwent a change in shape following the solar magnetic field reversal in 1980; in this paper evidence for a corresponding change in the ACR He spectrum is presented. It is found that the energy spectra of ACR He and oxygen and Galactic-cosmic-ray He-4 and He3 can be reproduced both before and after the field reversal using a simple solar modulation model in which the effects of curvature and gradient drifts are arbitrarily neglected.

Cummings, A. C.↗

NASA NTRS1990

Digital filtering of plume emission spectra

Fourier transformation and digital filtering techniques were used to separate the superpositioned spectral phenomena observed in the exhaust plumes of liquid propellant rocket engines. Space shuttle main engine (SSME) spectral data were used to show that extraction of spectral lines in the spatial frequency domain does not introduce error, and extraction of the background continuum introduces only minimal error. Error introduced during band extraction could not be quantified due to poor spectrometer resolution. Based on the atomic and molecular species found in the SSME plume, it was determined that spectrometer resolution must be 0.03 nm for SSME plume spectral monitoring.

Madzsar, George C.↗

NASA NTRS1990

Digital filtering of plume emission spectra

Madzsar, George C.↗