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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Competition between charge exchange and chemical reaction - The D2/+/ + H system

Study of the special features of molecular charge exchange and its competition with chemical reaction in the case of the D2(+) + H system. The trajectory surface hopping (TSH) model proposed by Tully and Preston (1971) is used to study this competition for a number of reactions involving the above system. The diatomics-in-molecules zero-overlap approximation is used to calculate the three adiabatic surfaces - one triplet and two singlet - which are needed to describe this system. One of the significant results of this study is that the chemical reaction and charge exchange are strongly coupled. It is also found that the number of trajectories passing into the chemical regions of the three surfaces depends very strongly on the surface crossings.-

Preston, R. K.↗
NASA NTRS1973

Product distributions and rate constants for ion-molecule reactions in water, hydrogen sulfide, ammonia, and methane

The thermal energy, bimolecular ion-molecule reactions occurring in gaseous water, hydrogen sulfide, ammonia, and methane have been identified and their rate constants determined using ion cyclotron resonance methods. Absolute rate constants were determined for the disappearance of the primary ions by using the trapped ion method, and product distributions were determined for these reactions by using the cyclotron ejection method. Previous measurements are reviewed and compared with the results using the present methods. The relative rate constants for hydrogen-atom abstraction, proton transfer, and charge transfer are also determined for reactions of the parent ions.

Huntress, W. T., Jr.↗
NASA NTRS1974

Reaction of HO2 with NO and NO2

A kinetic study is made of the reaction of HO2 with NO2, and relative rate coefficients are derived for this reaction and for the reaction of HO2 with NO. It is shown that irradiation of mixtures of N2O-O2-H2 in the presence of small amounts of NO2 at 2139 A and 25 C leads to the consumption of NO2. The results clearly indicate that NO2 is consumed during irradiation to form a product which thermally decomposes to regenerate NO2 thermally and that this product is undoubtedly HONO. In the case of mixtures of N2O-O2-H2 and N2O-O2-H2-CO in the presence of small amounts of both NO and NO2 the NO2 pressure increases initially, reaches a maximum, and then decreases at a constant rate.

Simonaitis, R.↗
NASA NTRS1974

Correlation changes in EEG, conditioned and behavioral reactions with various degrees of oxygen insufficiency

The dynamics of change in bioelectric activity of the brain during acute hypoxia are studied for the time that working capacity and active consciousness are preserved, and to establish the correlation between EEG changes and behavioral reactions under oxygen starvation. Changes in body functions and behavioral disturbances are related to the degree of oxygen saturation in the blood, to bioelectric activity of the brain, and to an increase in conditioned reflexes. The capacity for adequate reaction to external signals and for coordinated psychomotor activity after loss of consciousness returns to man after 30 seconds. Repeated effects of hypoxia produce changes in the physiological reactions of the body directed toward better adaptation to changing gaseous environments.

Agadzhanyan, N. A.↗
NASA NTRS1974

Kinetics of the reaction of nitric oxide with hydrogen

Mixtures of NO and H2 diluted in argon or krypton were heated by incident shock waves, and the infrared emission from the fundamental vibration-rotation band of NO at 5.3 microns was used to monitor the time-varying NO concentration. The reaction kinetics were studied in the temperature range 2400-4500 K using a shock-tube technique. The decomposition of nitric oxide behind the shock was found to be modeled well by a fifteen-reaction system. A principle result of the study was the determination of the rate constant for the reaction H + NO yields N + OH, which may be the rate-limiting step for NO removal in some combustion systems. Experimental values of k sub 1 were obtained for each test through comparisons of measured and numerically predicted NO profiles.

Flower, W. L.↗
NASA NTRS1975

Evaluation and characterization of the methane-carbon dioxide decomposition reaction

A program was conducted to evaluate and characterize the carbon dioxide-methane (CO2-CH4) decomposition reaction, i.e., CO2 + CH4 = 2C + 2H2O. The primary objective was to determine the feasibility of applying this reaction at low temperatures as a technique for recovering the oxygen (O2) remaining in the CO2 which exits mixed with CH4 from a Sabatier CO2 reduction subsystem (as part of an air revitalization system of a manned spacecraft). A test unit was designed, fabricated, and assembled for characterizing the performance of various catalysts for the reaction and ultraviolet activation of the CH4 and CO2. The reactor included in the test unit was designed to have sufficient capacity to evaluate catalyst charges of up to 76 g (0.17 lb). The test stand contained the necessary instrumentation and controls to obtain the data required to characterize the performance of the catalysts and sensitizers tested: flow control and measurement, temperature control and measurement, product and inlet gas analysis, and pressure measurement. A product assurance program was performed implementing the concepts of quality control and safety into the program effort.

Davenport, R. J.↗
NASA NTRS1975

A simple reaction-rate model for turbulent diffusion flames

A simple reaction rate model is proposed for turbulent diffusion flames in which the reaction rate is proportional to the turbulence mixing rate. The reaction rate is also dependent on the mean mass fraction and the mean square fluctuation of mass fraction of each reactant. Calculations are compared with experimental data and are generally successful in predicting the measured quantities.

Bangert, L. H.↗
NASA NTRS1974

Reaction control system plume flow field interaction effects on the Space Shuttle orbiter

This paper presents an analysis of data obtained from wind tunnel tests of the aerodynamic interference induced by the reaction control system jets on Space Shuttle orbiter configurations. The test data was obtained using cold gas simulation techniques with nozzles scaled to match jet exit momentum ratio as the primary parameter at Mach numbers from 2.5 to 10. Significant induced effects have been found that degrade the performance of the pitch and roll reaction controls and that induce cross-coupling effects for yaw reaction control. Analysis of the induced data shows good correlation with jet exit momentum ratio.

Rausch, J. R.↗
NASA NTRS1974

Measurements of positive ion conversion and removal reactions relating to the Jovian ionosphere

Measured rates are presented for the reaction of He(+) ions with H2 (and D2) molecules to form H(+), H2(+), and HeH(+) ions, as well as for the subsequent reactions of H(+) and HeH(+) ions with H2 to form H3(+). The neutralization of H3(+) /and H5(+)/ ions by dissociative recombination with electrons is shown to be fast. The reaction He(+) + H2 is slow (k 1.1 x 10 to the minus 13th cu cm/sec at 300 K) and produces principally H(+) by the dissociative charge transfer branch. It is concluded that there may be a serious bottleneck in the conversion of two of the primary ions of the upper Jovian ionosphere, H(+) and He(+) (which recombine slowly), to the rapidly recombining H3(+) ion.

Johnsen, R.↗
NASA NTRS1974

Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide

The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO, have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for reaction rate was measured over a temperature range of 263-502 K and the data were fitted to an Arrhenius expression with good linearity. A comparison of the present results with those from previous studies of this reaction is also presented.

Klemm, R. B.↗
NASA NTRS1975

Organic synthesis by quench reactions

Study of the effects of chemical quench reactions on the formation of organic compounds at a water surface under simulated primordial earth conditions. A mixture of gaseous methane and ammonia over a water surface was exposed to an arc discharge between an electrode and the water surface, generating reactive species. Various organic molecules were formed by a subsequent quenching of these species generated on the water surface. The effects of these water-surface quench reactions were assessed by comparing the amounts of synthesized molecules to the amounts which formed during the discharge of an arc above the water level. It is concluded that the quench (or wet) discharge led to faster rates of reactions, higher-molecular-weight organic compounds, and one-order-of-magnitude larger yields than the dry discharge.

Park, W. K.↗
NASA NTRS1974

Choice-reaction time to visual motion with varied levels of simultaneous rotary motion

Twelve airline pilots were studied to determine the effects of whole-body rotation on choice-reaction time to the horizontal motion of a line on a cathode-ray tube. On each trial, one of five levels of visual acceleration and five corresponding proportions of rotary acceleration were presented simultaneously. Reaction time to the visual motion decreased with increasing levels of visual motion and increased with increasing proportions of rotary acceleration. The results conflict with general theories of facilitation during double stimulation but are consistent with neural-clock model of sensory interaction in choice-reaction time.

Clark, B.↗
NASA NTRS1975

Sinusoidal reaction formulation for radiation and scattering from conducting surfaces

A piecewise-sinusoidal reaction technique is proposed for the study of scattering and radiation from perfectly conducting bodies of arbitrary shape. The reaction technique described is a moment method based on the integral equation of an electric field. A theory of sinusoidal reaction formulation for radiation and scattering problems is outlined, in which the scattered field is obtained by integrating the surface currents. Numerical results are presented for the scattering patterns of rectangular plates and corner reflectors and the radiation patterns of corner-reflector antennas.

Wang, N. N.↗
NASA NTRS1975

Apparatus for production, measurement and reaction studies of dissociated gases at elevated temperatures

An apparatus is described which is used for the controlled production, characterization, and study of dissociated gases in a microwave discharge at elevated temperatures. A unique feature is the ability to produce and study a microwave discharge plasma in the heated zone. This allows elevated temperature reactions to be studied in high concentrations of dissociated gases. Further, the system permits weight change measurements of specimens in the plasma, thus facilitating reaction rate determinations. Included is a description of a cavity for use on a 50-mm diameter cylindrical reactor. The effects of flow rate, pressure, temperature, power, metal sample, and sampling position on dissociation percentage of oxygen in the apparatus are described as well as a technique for sample temperature measurements in the plasma which permits determination of high temperature recombination coefficients and reaction rates.

Christian, J. D.↗
NASA NTRS1975

Choice reaction time to visual motion during prolonged rotary motion in airline pilots

Thirteen airline pilots were studied to determine the effect of preceding rotary accelerations on the choice reaction time to the horizontal acceleration of a vertical line on a cathode-ray tube. On each trial, one of three levels of rotary and visual acceleration was presented with the rotary stimulus preceding the visual by one of seven periods. The two accelerations were always equal and were presented in the same or opposite directions. The reaction time was found to increase with increases in the time the rotary acceleration preceded the visual acceleration, and to decrease with increased levels of visual and rotary acceleration. The reaction time was found to be shorter when the accelerations were in the same direction than when they were in opposite directions. These results suggest that these findings are a special case of a general effect that the authors have termed 'gyrovisual modulation'.

Stewart, J. D.↗
NASA NTRS1975

Kinetics of the reaction of nitric oxide with hydrogen

The reaction of nitric oxide with hydrogen has been studied in the temperature range 2400-4500 K using a shock-tube technique. Mixtures of NO and H2 diluted in argon or krypton were heated by incident shock waves, and the infrared emission from the fundamental vibration-rotation band of NO at 5.3 microns was used to monitor the time-varying NO concentration. The decomposition of nitric oxide behind the shock was found to be modeled well by a fifteen-reaction system. A principal result of the study was the determination of the rate constant k1 for the reaction H + NO yields N + OH, which may be the rate-limiting step for NO removal in some combustion systems. Experimental values of k1 were obtained for each test through comparisons of measured and numerically predicted NO profiles. The data are fit closely by the expression k1 = 1.34 times 10 to the fourteenth power exp(-49 200/RT) cu cm/mole-sec. These data appear to be the first available for this rate constant.

Flower, W. L.↗
NASA NTRS1975

Shock tube measurements of specific reaction rates in the branched chain CH4-CO-O2 system

Growth constants, obtained by measuring the blue CO flame band emission behind incident shock waves, were obtained for two elementary bimolecular reactions involved in the oxidation of methane. Gas mixtures containing small amounts of CH4 with varying amounts of CO, O2, and in one case CO2, diluted with argon, were investigated, and exponential growth constants were derived from plots of the logarithm of observed light intensity versus gas time. The rate constant for the reaction O + CH4 yields CH3 + OH was found to be 1.9 times 10 to the 14th exp(-5900/T) cu cm per mole per sec in the range 1300-2000 K; for the reaction CH3 + O2 yields CH3O + O, the rate constant was determined to be 2.4 times 10 to the 13th exp(-14,500/T) cu cm per mole per sec in the range 1200 to 1900 K.

Brabbs, T. A.↗
NASA NTRS1976

The reactions of O(ID) and OH with CH3OH, oxidation of the HCO radial, and the photochemical oxidation of formaldehyde

An experimental, laboratory study of the various photochemical reactions that can occur in the mesosphere and stratosphere is presented. N2O was photolyzed at 2139 A in the presence of CH3OH and CO. The O(id) produced in the photolysis reacted with CH3OH to produce OH radicals, and thus the reactions of both O(id) and OH were able to be studied. Also considered was the oxidation of the HCO radical. Mixtures of Cl2, O2, H2CO, and sometimes N2 or He were irradiated at 3660 A at several temperatures to photodecompose the Cl2. The photochemical oxidation of formaldehyde was studied as follows: formaldehyde in the presence of N2 and/or O2 (usually dry air) was photolyzed with a medium pressure Hg lamp used in conjunction with various filters which transmit different relative amounts of Hg lines from 2894 A to 3660 A. Results are presented and discussed, along with a description of experimental procedures and apparatus, and chemical reaction kinetics.

Osif, T. L.↗