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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Experimental and analytical study of nitric oxide formation during combustion of propane in a jet-stirred combustor

A jet-stirred combustor, constructed of castable zirconia and with an Inconel injector, was used to study nitric oxide formation in propane-air combustion with residence times in the range from 3.2 to 3.3 msec and equivalence ratios varying from 0.7 to 1.4. Measurements were made of combustor operating temperature and of nitric oxide concentration. Maximum nitric oxide concentrations of the order of 55 ppm were found in the range of equivalence ratio from 1.0 to 1.1. A finite-rate chemical kinetic mechanism for propane combustion and nitric oxide formation was assembled by coupling an existing propane oxidation mechanism with the Zeldovich reactions and reactions of molecular nitrogen with hydrocarbon fragments. Analytical studies using this mechanism in a computer simulation of the experimental conditions revealed that the hydrocarbon-fragment-nitrogen reactions play a significant role in nitric oxide formation during fuel-rich combustion.

Wakelyn, N. T.↗
NASA NTRS1978

Isoprenoid hydrocarbons produced by thermal alteration of Nostoc muscorum and Rhodopseudomonas spheroides

The potential of algae and photosynthetic bacteria to serve as precursors of kerogen was studied to determine what factors affect the relative rates of formation of precursor hydrocarbons. Cells of Nostoc muscorum and Rhodopseudomonas spheroides were subjected to thermal alteration (by heating samples in glass tubes sealed under nitrogen) for two, four, and twelve weeks. Both unextracted and extracted cells in the absence and presence of montmorillonite were investigated, and the isoprenoid hydrocarbons produced in these experiments were determined. Phytane and five isomeric phytenes were the main hydrocarbons observed; their relative rates of formation in the different experimental conditions are described. No phytadienes, pristane, or pristenes were detected.

Philp, R. P.↗
NASA NTRS1977

Multi-attribute subjective evaluations of manual tracking tasks vs. objective performance of the human operator

A computational method to deal with the multidimensional nature of tracking and/or monitoring tasks is developed. Operator centered variables, including the operator's perception of the task, are considered. Matrix ratings are defined based on multidimensional scaling techniques and multivariate analysis. The method consists of two distinct steps: (1) to determine the mathematical space of subjective judgements of a certain individual (or group of evaluators) for a given set of tasks and experimental conditionings; and (2) to relate this space with respect to both the task variables and the objective performance criteria used. Results for a variety of second-order trackings with smoothed noise-driven inputs indicate that: (1) many of the internally perceived task variables form a nonorthogonal set; and (2) the structure of the subjective space varies among groups of individuals according to the degree of familiarity they have with such tasks.

Siapkaras, A.↗
NASA NTRS1979

Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described.

Williams, J. G.↗
NASA NTRS1979

Effect of sterilization irradiation on friction and wear of ultrahigh-molecular-weight polyethylene

The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against 316L stainless steel in dry air at 23 C was determined. A pin-on-disk apparatus was used. Experimental conditions included a 1-kilogram load, a 0.061- to 0.27-meter-per-second sliding velocity, and a 32000- to 578000-meter sliding distance. Although sterilization doses of 2.5 and 5.0 megarads greatly altered the average molecular weight and the molecular weight distribution, the friction and wear properties of the polymer were not significantly changed.

Jones, W. R., Jr.↗
NASA NTRS1978

Assessment of the impact of increased solar ultraviolet radiation upon marine ecosystems

Reduction of the earth's ozone layer, with a resultant increase in transmission of solar ultraviolet radiation in the 290 to 320nm waveband (UV-B), via space shuttle operations through the stratosphere is considered. It is shown that simulated solar ultraviolet radiation can, under experimental conditions, detrimentally affect the marine organisms that form the base of the food web of oceanic and estuarine ecosystems. Whether a small increase in biologically harmful ultraviolet radiation might overwhelm these mechanisms and produce changes that will have damaging consequences to the biosphere is discussed. The potential for irreversible damage to the productivity, structure and/or functioning of a model estuarine ecosystem by increased UV-B radiation and whether these ecosystems are highly stable or amenable to adaptive change is studied. Data are provided to assess the potential impact upon marine ecosystems if space shuttle operations contribute to a reduction of the stratospheric ozone layer and the sensitivity of key community components to increased UV-B radiation is examined.

Worrest, R. C.↗
NASA NTRS1978

Axisymmetric disturbances in a disk galaxy

The Lin-Shu dispersion relation, with corrections to match experimental conditions and in combination with a quantization rule, permits growth rates to be calculated for axisymmetric disturbances in an axisymmetric disk of stars. Growth rates calculated this way are in reasonable quantitative agreement with recently published results from a series of numerical experiments. The agreement confirms the physical basis of the theory and demonstrates that the theory remains valid even when strained somewhat in the application to galactic models.

Miller, R. H.↗
NASA NTRS1979

Inverse multiple scattering problems. III - Inadequacy of certain limb darkening and phase curves for retrieving atmospheric information and limitations of approximate scattering models

The paper considers three complementary inverse multiple scattering problems relating to a uniquely defined atmospheric scattering model. Consideration is given to the appropriateness, for data inversion purposes, of intensities observed in diffuse reflection under a variety of experimental conditions; the uniqueness of the inverse solution is investigated. It is found that light curves representing monotonic variations, such as limb darkening curves and phase curves for a planetary (e.g., Venus) disk center are unsuitable for inferring atmospheric and scattering parameters.

Fymat, A. L.↗
NASA NTRS1979

Numerical simulation of experiments in the Giant Planet Facility

Utilizing a series of existing computer codes, ablation experiments in the Giant Planet Facility are numerically simulated. Of primary importance is the simulation of the low Mach number shock layer that envelops the test model. The RASLE shock-layer code, used in the Jupiter entry probe heat-shield design, is adapted to the experimental conditions. RASLE predictions for radiative and convective heat fluxes are in good agreement with calorimeter measurements. In simulating carbonaceous ablation experiments, the RASLE code is coupled directly with the CMA material response code. For the graphite models, predicted and measured recessions agree very well. Predicted recession for the carbon phenolic models is 50% higher than that measured. This is the first time codes used for the Jupiter probe design have been compared with experiments.

Green, M. J.↗
NASA NTRS1979

Gating effects in Halobacterium halobium membrane transport

The transport of Na(+) via an H(+)/Na(+) antiporter and of aspartate and serine via Na(+)/amino acid symport systems was studied in Halobacterium halobium cell envelope vesicles. Gradients for H(+) were produced by illuminating the bacteriorhodopsin-containing vesicles at different light intensities, and the rate and extent of Na(+) transport were followed as functions of the electrochemical potential difference for protons. The coupling of Na(+) and H(+) gradients suggested a translocation stoichiometry of 2H(+)/Na(+) for the antiporter. The rate of Na(+) transport increases steeply above a critical transmembrane electrochemical proton gradient, and since the electrical and the chemical potentials of H(+) at this threshold point vary with the experimental conditions, while the sum of these potentials is constant, it was concluded that the gating of the Na(+) transport is caused by the total electrochemical gradient.

Lanyi, J. K.↗
NASA NTRS1980

Restraint ulcers in the rat. 1: Influence on ulcer frequency of fasting and of environmental temperature associated with immobilization of varying durations

The results of the production of experimental ulcers in rats are described. Two experimental conditions were found to regularly provoke the appearance of gastric ulcers in a high percentage of rats: (1) two-and-a-half hour restraint, proceeded by a 24 hour fast; and (2) one-and-a-half hour restraint with lowering of the environmental temperature while fasting.

Buchel, L.↗
NASA NTRS1980

Principles for classification of work load for women

In an attempt to develop guidelines for classification by degree of intensity of various kinds of physical work performed by women, the effects of different work loads on women as compared to men were studied under industrial and experimental conditions, including response of the cardiovascular and respiratory systems to specified physical exercises of increasing intensity. Physiological criteria for assessing female labor in terms of intensity are proposed.

Navakatikyan, A. O.↗
NASA NTRS1980

Efficient ionisation of calcium, strontium and barium by resonant laser pumping

Efficient ionization has been observed when an atomic vapor of strontium, barium or calcium was illuminated with a long pulse tunable laser at the frequency of the atomic resonance line. The variation in the degree of ionization with neutral density and laser intensity has been measured using the 'hook' method. The maximum ionization observed was 94%. Excited state populations were measured yielding an excitation temperature (depending on exact experimental conditions) in the region of 0.4 eV. The decay of ion density after the laser pulse was monitored and the recombination coefficients determined. The results are interpreted in terms of an electron heating model.

Skinner, C. H.↗
NASA NTRS1979

Laboratory simulations of the pyrolytic release experiments - An interim report

During its operation on Mars the pyrolytic release experiment (PR) detected the fixation of small amounts of CO2 and/or CO. Laboratory simulations of the experimental conditions were made in an attempt to substantiate the previous conclusion that these reactions were chemical rather than biological. After pretreatment and incubation under various conditions, pyrolytic analysis was used to indicate the extent of surface catalyzed conversion of (C-14)O2 or (C-14)O to (C-14)-organic compounds. This abiotic synthesis was detected in experiments with three iron oxides, viz. hematite, magnetite and maghemite. When the incubation atmosphere was supplemented with water vapor, the levels of synthesis were in a range comparable to that detected in the Viking PR tests. An abiotic synthesis was also detected in experiments with a mixture of clays and minerals (Mars analog soil) or with montmorillonite artificially enriched in iron. With either substratum the reaction appeared to be the result of a photocatalytic synthesis of (C-14)-organics from (C-14)O and surface hydroxyl groups. This process was not dependent on the presence of water vapor in the incubation atmosphere. Although a duplication of the Viking data has not been achieved, these findings support the abiotic interpretation of the PR results.

Hubbard, J. S.↗
NASA NTRS1980

Comparative study of choleretic agents in anesthetized rats as well as in restrained and and unrestrained rats, with or without compensation for biliary loss

Tests were conducted on Wistar rats by using 3 control choleretic agents: 1-phenyl-1-hydroxy n-pentane, dehydrocholic acid, and phenyl-dimethylacetic acid. The effects of these agents were compared in different experimental conditions. The comparative study of choleretic agents in anesthetized rats, in restrained and unrestrained rats, with or without compensation for biliary loss by the biliary secretion of restrained or unrestrained rats does not show, in systematic pharmecodynamic investigations, an obvious superiority over the methods based on the simple technique.

Labrid, C.↗
NASA NTRS1981

Response of selected microorganisms to experimental planetary environments

Anaerobic and aerobic sporeformers and non-sporeformers were cultivated anaerobically in nutrient media under various pressures (up to 1800 psi) of pure H2, CH4, NH3, and H2S. Viability assays were performed periodically to determine growth, survival, or spore survival. Hydrogen up to 1800 psi demonstrated little or no suppression of growth with the possible exception of Bacillus coagulans at 1800 psi. The obligate anaerobes grew very well. Under CH4 the obligate anaerobes again exhibited the most prolific growth, whereas the facultative anaerobes grew well except under higher pressures. Ammonia at low pressure was extremely toxic to all test organisms. At 100 psi all populations were killed within 24 hours except Staphylococcus aureus which survived for 72 hours and the Bacillus spp. which produced a surviving population of approximately 10,000 spores/ml. All populations in H2S were killed within 24 to 48 hours except Proteus mirabilis which decreased to 100 cells/ml and the Bacillus spp. Spore survival studies of two months duration demonstrated that B. coagulans and B. pumilus survived under all experimental conditions. Clostridium novyi type B and C. sporogenes were killed rapidly in NH3 and H2S and demonstrated no sporulation.

Foster, T. L.↗
NASA NTRS1981

Acceleration wave breakup of liquid jets with airstreams

Characteristic mean drop diameters were determined for downstream and upstream injection into nonswirling and swirling airflows. The effects of the aerodynamic and liquid surface forces on the mean drop size were obtained with a scanning radiometer. Water jet breakup was studied primarily in the acceleration wave regime with values of WeRe 10 to the 6th power and the following empirical expression was obtained: D(o)/D(m) =C (WeRe) to the 0.4, power where D(o) and D(m) are the orifice and mean drop diameters, respectively. We and Re are the Weber and Reynolds numbers defined as repectively, We = rho(a)D(o)V(r)/sigma and Re = D(o)V(r)/nu, where V(r) and rho(a) are airstream relative velocity and density, respectively, and sigma and nu are surface tension and kinematic viscosity of the liquid, respectively. The proportionally constant C was evaluated as follows: for downstream injection, C = 0.023 with nonswirling airflow, and C = 0.027 with swirling airflow. For upstream injection, the empirical expression D(o)/D(m) = 0.0045 (WeRe) to the 0.5 power was obtained with nonswirling airflow. Experimental conditions included a water flow rate of 68 liter per hour and an airflow rate per unit area range of 4.6 to 25.2 gm/sq cm sec at 293 K and atmospheric pressure.

Ingebo, R. D.↗
NASA NTRS1981

Combustion of solid carbon rods in zero and normal gravity

In order to investigate the mechanism of carbon combustion and to assess the importance of gravitational induced convection on the process, zero and normal gravity experiments were conducted in which spectroscopic carbon rods were resistance ignitied and burned in dry oxygen environments. In the zero-gravity drop tower tests, a blue flame surrounded the rod, showing that a gas phase reaction in which carbon monoxide was oxidized to carbon dioxide was taking place. The ratio of flame diameter to rod diameter was obtained as a function of time. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter. In the normal gravity tests, direct mass spectrometric sampling was used to measure gas phase concentrations. The gas sampling probe was positioned near the circumference of a horizontally mounted 0.615 cm diameter carbon rod, either at the top or at angles of 45 deg to 90 deg from the top, and yielded concentration profiles of CO2, CO, and O2 as a function of distance from the surface. The mechanism controlling the combustion process was found to change from chemical process control at the 90 deg and 45 deg probe positions to mass transfer control at the 0 deg probe position at the top of the rod. Under the experimental conditions used, carbon combustion was characterized by two surface reactions, 2C + O2 yields 2CO and CO2 + C yields 2CO, and a gas phase reaction, 2CO + O2 yields 2CO2.

Spuckler, C. M.↗