Engineering topics

White, R. E.

Publications and source records attributed to White, R. E..

At least 19 records

NASA NTRS1992

Calorimetric determination of the thermoneutral potential of Li/BCX and Li/SOCl2 cells

Results are presented of the calorimetric determination of the effective thermoneutral potential, Eetp, of Li/BCS and Li/SOCl2 cells in the temperature range 0-60 C through a continuous recording of the cell voltage, heat flow, and current. The average effective thermoneutral potential at 25 C was 4.0 and 3.84 V for BCX and Li/SOCl2 cells, respectively. Based on the classical approach, the reversible cell potential, Er, and temperature dependence of reversible cell potential, dEr/dT, for BCX cell were 3.74 V and -0.952 mV/K, respectively, and for Li/SOCl2, Er = 3.67 V and dEr/dT = 0.567 mV/K. The thermal polarization (Eetp-E1), where E1 is the load voltage, for both cells, showed that they are the most thermally efficient near 40 C. An overall reaction proposed for the BCX chemistry is supported by the calculated thermodynamic parameters.

Kalu, E. E.↗

NASA NTRS1992

Thermal mathematical modeling of a multicell common pressure vessel nickel-hydrogen battery

A two-dimensional and time-dependent thermal model of a multicell common pressure vessel (CPV) nickel-hydrogen battery was developed. A finite element solver called PDE/Protran was used to solve this model. The model was used to investigate the effects of various design parameters on the temperature profile within the cell. The results were used to help find a design that will yield an acceptable temperature gradient inside a multicell CPV nickel-hydrogen battery. Steady-state and unsteady-state cases with a constant heat generation rate and a time-dependent heat generation rate were solved.

Kim, Junbom↗

NASA NTRS1992

Measurements of the fundamental thermodynamic parameters of Li/BCX and Li/SOCl2 cells

Two experimental techniques - equilibrium or reversible cell discharge and measurement of open circuit potential as a function of temperature - are used to determine the thermodynamic data needed to estimate the heat generation characteristics of Li/BCX and Li/SOCl2 cells. The results obtained showed that the reversible cell potential, the temperature dependence of the reversible cell potential, and the thermoneutral potential of the BCX cell were 3.74 V, -0.857 +/- 0.198 mV/K, and 3.994 +/- 0.0603 V, respectively. The respective values obtained for the Li/SOCl2 cell were 3.67 V, -0.776 +/- 0.255 mV/K, and 3.893 +/- 0.0776 V. The difference between the thermoneutral potential of Li/BCX and Li/SCl2 cells is attributable to the difference in their electroactive components.

Kalu, E. E.↗

NASA NTRS1992

Bulk thermal capacity determination for Li/BCX and Li/SOClN2 cells

The bulk heat capacities of Li/BCX and Li/SOClN2 cells were determined at 0 and 100 percent depth-of-discharge for 2.0 V cut-off voltage, in the temperature range 0 to 60 C by a method that did not involve the destruction of the cell nor the contact of cell with a liquid. The heat capacities are found to be dependent on state-of-charge, increasing with depth-of-discharge. The Li/BCX DD-cell has a lower heat capacity than a high rate Li/SOCl2 D-cell. The results obtained by this method compare favorably well with results reported in the literature through other methods. The bulk heat capacities of the cells did not change significantly in the temperature range 0 to 60 C.

Kalu, E. E.↗

NASA NTRS1992

The self-discharge of the NiOOH/Ni(OH)2 electrode constant potential study

Hydrogen oxidation currents at a NiOOH/Ni(OH)2 electrode were measured directly at constant potentials for various hydrogen pressures and states of charge. It was found that the hydrogen oxidation current is linearly proportional to the hydrogen pressure at all electrode potentials and that the logarithm of the anodic current is a linear function of electrode potential. It was also found that hydrogen oxidation on the nickel substrate material was strongly inhibited by the presence of nickel hydroxide on the substrate surface. By comparing the currents for hydrogen oxidation and oxygen evolution on the NiOOH/Ni(OH)2 electrode and a nickel substrate, it is suggested that the self-discharge of the NiOOH/Ni(OH)2 electrode is mainly due to electrochemical oxidation of hydrogen on the active electrode material.

Mao, Z.↗

NASA NTRS1992

Mathematical modeling of a primary zinc/air battery

The mathematical model developed by Sunu and Bennion has been extended to include the separator, precipitation of both solid ZnO and K2Zn(OH)4, and the air electrode, and has been used to investigate the behavior of a primary Zn-Air battery with respect to battery design features. Predictions obtained from the model indicate that anode material utilization is predominantly limited by depletion of the concentration of hydroxide ions. The effect of electrode thickness on anode material utilization is insignificant, whereas material loading per unit volume has a great effect on anode material utilization; a higher loading lowers both the anode material utilization and delivered capacity. Use of a thick separator will increase the anode material utilization, but may reduce the cell voltage.

Mao, Z.↗

NASA NTRS1989

A catalog of stellar spectrophotometry

A machine-readable catalog of stellar spectrophotometric measurements made with rotating grating scanner is introduced. Consideration is given to the processes by which the stellar data were collected and calibrated with the fluxes of Vega (Hayes and Latham, 1975). A sample page from the spectrophotometric catalog is presented.

Adelman, S. J.↗

NASA NTRS1989

A thermal analysis of a spirally wound battery using a simple mathematical model

A two-dimensional thermal model for spirally wound batteries has been developed. The governing equation of the model is the energy balance. Convective and insulated boundary conditions are used, and the equations are solved using a finite element code called TOPAZ2D. The finite element mesh is generated using a preprocessor to TOPAZ2D called MAZE. The model is used to estimate temperature profiles within a spirally wound D-size cell. The model is applied to the lithium/thionyl chloride cell because of the thermal management problems that this cell exhibits. Simplified one-dimensional models are presented that can be used to predict best and worst temperature profiles. The two-dimensional model is used to predict the regions of maximum temperature within the spirally wound cell. Normal discharge as well as thermal runaway conditions are investigated.

Evans, T. I.↗

NASA NTRS1987

A mathematical model of a lithium/thionyl chloride primary cell

A 1-D mathematical model for the lithium/thionyl chloride primary cell was developed to investigate methods of improving its performance and safety. The model includes many of the components of a typical lithium/thionyl chloride cell such as the porous lithium chloride film which forms on the lithium anode surface. The governing equations are formulated from fundamental conservation laws using porous electrode theory and concentrated solution theory. The model is used to predict 1-D, time dependent profiles of concentration, porosity, current, and potential as well as cell temperature and voltage. When a certain discharge rate is required, the model can be used to determine the design criteria and operating variables which yield high cell capacities. Model predictions can be used to establish operational and design limits within which the thermal runaway problem, inherent in these cells, can be avoided.

Evans, T. I.↗

NASA NTRS1986

CO near the Pleiades: Encounter of a star cluster with a small molecular cloud

Although there is a large amount of interstellar matter near the Pleiades star cluster, the observed dust and gas is not a remnant of the placental molecular cloud from which the star cluster was formed. Carbon monoxide (CO) associated with the visible reflection nebulae was discovered by Cohen (1975). Its radial velocity differs from that of the cluster by many times the cluster escape velocity, which implies that the cloud-cluster association is the result of a chance encounter. This circumstance and the proximity of the Pleiades to the sun creates an unique opportunity for study of interstellar processes at high spatial resolution. To study the molecular component of the gas, a 1.7 square degree field was mapped with the AT&T Bell Laboratories 7-meter antenna (1.7' beam) on a 1' grid in the J=1.0 C(12)O line, obtaining over 6,000 spectra with 50 kHz resolution. The cloud core was mapped in the J=1-0 line of C(13)O. Further observations include an unsuccessful search for CS (J=2-1) at AT&T BL, and some C(12)O J=2-1 spectra obtained at the Millimeter Wave Observatory of the University of Texas.

Bally, J.↗

NASA NTRS1982

A survey of interstellar neutral potassium. I - Abundances and physical conditions in clouds toward 188 early-type stars

Observations of interstellar absorption in the resonance doublet 7664, 7698 A of neutral potassium toward 188 early-type stars at a spectral resolution of 8 km/s are reported. The 7664 A line is successfully separated from nearly coincident telluric O2 absorption for all but a few of the 165 stars for which K I absorption is detected, making possible an abundance analysis by the doublet ratio method. The relationships between the potassium abundances and other atomic abundances, the abundance of molecular hydrogen, and interstellar reddening are investigated.

Chaffee, F. H., Jr.↗

NASA NTRS1978

On the detectability of millimeter wavelength spectral lines from planetary atmospheres

This paper adopts a simple line-formation model to estimate detection limits on the fractional absorption produced by molecular lines in the spectra of the planets, when observed with the 14-m antenna and low-noise receivers of the Five College Radio Astronomy Observatory. The results, which can readily be adjusted for receiver and telescope characteristics of other observatories, indicate that three kinds of observing programs may prove fruitful: (1) programs to monitor temporal variations of the strong CO absorption in the spectrum of Venus and Mars; (2) searches for weak absorption lines of other molecules, which are particularly promising for Venus: and (3) efforts to measure broad features in the continuous spectra of Venus, and possibly Jupiter, produced by molecules deep in the planetary atmospheres. Except for delineation of broad features of NH3 and possibly H2O near 25 GHz, hardly any useful observations can be made at frequencies less than 60 GHz.

White, R. E.↗

NASA NTRS1977

The momentum transfer of incompressible turbulent separated flow due to cavities with steps

An experimental study was conducted using a plate test bed having a turbulent boundary layer to determine the momentum transfer to the faces of step/cavity combinations on the plate. Experimental data were obtained from configurations including an isolated configuration and an array of blocks in tile patterns. A momentum transfer correlation model of pressure forces on an isolated step/cavity was developed with experimental results to relate flow and geometry parameters. Results of the experiments reveal that isolated step/cavity excrecences do not have a unique and unifying parameter group due in part to cavity depth effects and in part to width parameter scale effects. Drag predictions for tile patterns by a kinetic pressure empirical method predict experimental results well. Trends were not, however, predicted by a method of variable roughness density phenomenology.

White, R. E.↗

NASA NTRS1977

Experimental subsonic drag properties of the space shuttle orbiter TPS tiles

The drag characteristics of the space shuttle orbiter thermal protection system (TPS) tiles were studied experimentally in subsonic flow. Full-scale tiles were mounted to a 3.05 x 3.5 m test board in four configurations plus a completely smooth case. Pressure gradients were produced by tilting the board relative to the freestream. The drags due to steps, slots, and gaps between the tiles were evaluated at various orientations, pressure gradients, and Reynolds numbers. Results showed that the contribution of gaps and slots were minor compared to those of typical steps. The results for skin friction did not correlate as a fully rough surface. Thus, the surface area of the TPS tiles was sufficient to allow smooth-wall Reynolds number effects even though the steps between tiles could double the skin friction.

Norton, D. J.↗

NASA NTRS1977

Microturbulence, systematic motions, and line formation in molecular clouds

Microturbulence and systematic motions are viewed as simplifying assumptions made to facilitate treatment of line formation in molecular clouds, and line intensities calculated in the two approximations are compared to estimate how uncertainties about the actual line-broadening mechanism affect the interpretation of molecular emission lines. For lines formed by two-level molecules in an isothermal homogeneous cloud, the alternative assumptions lead to peak and integrated line intensities which agree within the differences (up to a factor of 3) associated with the ignorance of cloud geometry. New multilevel calculations for CO in the same cloud model bear out the generality of this result. It follows that, within the geometrical uncertainties, the Sobolev (1960) approximation may be used confidently in the numerous applications for which this simple cloud model suffices.

White, R. E.↗

NASA NTRS1976

Starsat: A space astronomy facility

Preliminary design and analyses of a versatile telescope for Spacelab missions are presented. The system is an all-reflective Korsch three-mirror telescope with excellent performance characteristics over a wide field and a broad spectral range, making it particularly suited for ultraviolet observations. The system concept is evolved around the utilization of existing hardware and designs which were developed for other astronomy space projects.

Hamilton, E. C.↗

NASA NTRS1976

Isotopic abundances of Hg in mercury stars inferred from the Hg II line at 3984 A

Wavelengths of the Hg II absorption feature at 3984 A in 30 Hg stars are distributed uniformly from the value for the terrestrial mix to a value that corresponds to nearly pure Hg-204. The wavelengths are correlated loosely with effective temperatures inferred from Q(UBV). Relative isotopic abundances derived from partially resolved profiles of the 3984-A line in iota CrB, chi Lup, and HR 4072 suggest that mass-dependent fractionation has occurred in all three stars. It is supposed that such fractionation occurs in all Hg stars, and a scheme whereby isotopic compositions can be inferred from a comparison of stellar wavelengths and equivalent widths with those calculated for a family of fractionated isotopic mixes. Theoretical profiles calculated for the derived isotopic composition agree well with high-resolution interferometric profiles obtained for three of the stars.

White, R. E.↗

NASA NTRS1974

Depletion of interstellar sodium and calcium

New measurements of the Ca II/Ca I ratios in interstellar clouds lead to the conclusion that not only Ca, but also Na, is underabundant in these regions. Recent calculations of element depletion by accretion of atoms onto dust grains probably cannot account for the observed abundance range. The extreme underabundance of Ca, and some part of the abundance range, probably reflect the composition of the grain cores.

White, R. E.↗