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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Space shuttle SRM plume expansion sensitivity analysis

The exhaust plumes of the space shuttle solid rocket motors can have a significant effect on the base pressure and base drag of the shuttle vehicle. A parametric analysis was conducted to assess the sensitivity of the initial plume expansion angle of analytical solid rocket motor flow fields to various analytical input parameters and operating conditions. The results of the analysis are presented and conclusions reached regarding the sensitivity of the initial plume expansion angle to each parameter investigated. Operating conditions parametrically varied were chamber pressure, nozzle inlet angle, nozzle throat radius of curvature ratio and propellant particle loading. Empirical particle parameters investigated were mean size, local drag coefficient and local heat transfer coefficient. Sensitivity of the initial plume expansion angle to gas thermochemistry model and local drag coefficient model assumptions were determined.

Smith, S. D.↗
NASA NTRS1976

Study of thermal stability and degradation of fire resistant candidate polymers for aircraft interiors

The thermochemistry of bismaleimide resins and phenolphthalein polycarbonate was studied. Both materials are fire-resistant polymers and may be suitable for aircraft interiors. The chemical composition of the polymers has been determined by nuclear magnetic resonance and infrared spectroscopy and by elemental analysis. Thermal properties of these polymers have been characterized by thermogravimetric analyses. Qualitative evaluation of the volatile products formed in pyrolysis under oxidative and non-oxidative conditions has been made using infrared spectrometry. The residues after pyrolysis were analyzed by elemental analysis. The thermal stability of composite panel and thermoplastic materials for aircraft interiors was studied by thermogravimetric analyses.

Hsu, M. T. S.↗
NASA NTRS1976

Ames T-3 fire test facility - Aircraft crash fire simulation

There is a need to characterize the thermal response of materials exposed to aircraft fuel fires. Large scale open fire tests are costly and pollute the local environment. This paper describes the construction and operation of a subscale fire test that simulates the heat flux levels and thermochemistry of typical open pool fires. It has been termed the Ames T-3 Test and has been used extensively by NASA since 1969 to observe the behavior of materials exposed to JP-4 fuel fires.

Fish, R. H.↗
NASA NTRS1977

Carbon monoxide on Jupiter and implications for atmospheric convection

A study of the equilibrium and disequilibrium thermochemistry of the recently discovered carbon monoxide on Jupiter suggests that the presence of this gas in the visible atmosphere is a direct result of very rapid upward mixing from levels in the deep atmosphere where the temperature is about 1100 K and where carbon monoxide is thermodynamically much more stable. As a consequence the observed carbon monoxide mixing ratio is a sensitive function of the vertical eddy mixing coefficient. We infer a value for this latter coefficient which is about three to four orders of magnitude greater than that in the earth's troposphere. This result directly supports existing structural and dynamical theories implying very rapid convection in the deep Jovian atmosphere, driven by an internal heat source.

Prinn, R. G.↗
NASA NTRS1979

Thermodynamics of selected trace elements in the Jovian atmosphere

The thermochemistry of several hundred compounds of twelve selected trace elements (Ge, Se, Ga, As, Te, Pb, Sn, Cd, Sb, Tl, In, and Bi) has been investigated for solar composition material along a Jupiter adiabat. The results indicate that AsF3, InBr, TlI, and SbS, in addition to CO, PH3, GeH4, AsH3, H2Se, HCl, HF, and H3BO3 proposed by Barshay and Lewis (1978), may be potential chemical tracers of atmospheric dynamics. The reported observation of GeH4 is interpreted on the basis of new calculations as implying rapid vertical transport from levels where the temperature is greater than or equal to 800 K. Upper limits are also set on the abundances of many gaseous compounds of the elements investigated.

Fegley, B., Jr.↗
NASA NTRS1980

Effect of HMX on the combustion response function

Over a pressure range of 3.5-7 MPa and a frequency range of 500-2000 Hz and compared to propellants having equivalent energy and burn rate, HMX produces less pressure-coupled acoustic driving than AP and is equivalent to NC/TMETN. Formation of carbonaceous combustion products indicates that binder decomposition does not follow equilibrium thermochemistry, and that this is aggravated by fuel richness or the absence of AP.

Strand, L. D.↗
NASA NTRS1982

Channel and physical models of the Jovian subnebula

A semiempirical physical model of the Jovian subnebula was developed by analogy with the primitive solar nebula itself. The chemical aspects of this model are developed according to the principles developed in the study of the thermochemistry and gas kinetic behavior of the solar nebula, but with important modifications to take into account the higher pressures and densities in the Jovian subnebula. The bulk compositions and densities of the inner satellites of Jupiter are calculated. It is proposed that Europa differs from Io chiefly in that in has suffered a less severe thermal history. The general features of this model are applicable with minor modification to the systems of Saturn and Uranus.

Lewis, J. S.↗
NASA NTRS1982

An investigation of equilibrium concepts

A different approach to modeling of the thermochemistry of rocket engine combustion phenomena is presented. The methodology described is based on the hypothesis of a new variational principle applicable to compressible fluid mechanics. This hypothesis is extended to treat the thermochemical behavior of a reacting (equilibrium) gas in an open system.

Prozan, R. J.↗
NASA NTRS1983

Chlorine nitrate - The sole product of the ClO + NO2 + M recombination

A laser operating at 266 nm is used to photolyze the product of the ClO + NO2 + M reaction, and the yield of Cl atoms, measured by resonance fluorescence, is found to be identical with that from equivalent concentrations of ClONO2. This is interpreted as a strong indication that no other isomers are formed in the recombination reaction. Evidence for isomers is surveyed, and the apparent forward-and-reverse-rate constant discrepancy is explained as a probable uncertainty in the thermochemistry.

Margitan, J. J.↗
NASA NTRS1982

Glass shell manufacturing in space

Highly-uniform, hollow glass spheres, which are used for inertial-confinement fusion targets, are formed from metal-organic gel powder feedstock in a drop-tower furnace. The modelling of this gel-to-sphere transformation has consisted of three phases: gel thermochemistry, furnance-to-gel heat transfer, and gravity-driven degradation of the concentricity of the molten shell. The heat transfer from the furnace to the free-falling gel particle was modelled with forced convection. The gel mass, dimensions, and specific heat as well as furnace temperature profile and furnace gas conductivity, were controlled variables. This model has been experimentally verified. In the third phase, a mathematical model was developed to describe the gravity-driven degradation of concentricity in molten glass shells.

Nolen, R. L.↗
NASA NTRS1985

Detailed course of the O + HO2 reaction

The elementary radical-radical reactions that are of such importance in laser, astrophysical, atmospheric, and combustion processes are increasingly open to direct rate measurement. Attention is presently given to the O + HO2 reaction, which has only one exothermic product channel: OH + O2. Isotopic product analysis was conducted spectroscopically using laser-induced fluorescence of OH. It is found that the simple atom-radical reaction takes place by way of the rapid formation and breakup of an unexpected radical intermediate, thereby raising questions as to the formation, thermochemistry, and decomposition of poorly known products in many other radical-radical reaction systems.

Sridharan, U. C.↗
NASA NTRS1986

Drop tube technical tasks

Criteria, using fundamental thermochemical dynamics, were developed to assist a scientist using the Drop Tube Facility in designing a good experiment. The types of parameters involved in designing the experiments include the type of furnace, the type of atmosphere, and in general which materials are better behaved than others as determined by past experience in the facility. One of the major advantages of the facility lies in its ability to provide large undercoolings in the cooling curve during the drops. A beginning was to consider the effect of oxygen and other gases upon the amount of undercooling observed. The starting point of the thermochemistry was given by Ellingham and later transformed into what is known as the Richardson Chart. The effect of surface oxidations upon the nucleation phenomena can be observed in each specimen.

Workman, G. L.↗
NASA NTRS1989

Hydrogen-silicon carbide interactions

A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamic maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of Region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicon carbide is the single stable solid phase in Region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4, and SiH. Analysis of the kinetics of reaction for Region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to Regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

Eckel, Andrew J.↗
NASA NTRS1990

Uranus photochemistry and prospects for Voyager 2 at Neptune

CH4 is the only photochemically active constituent in the atmospheres of Uranus and Neptune. NH3, H2O and H2S are all removed by condensation at pressures greater than 1.5 bars. Although the bulk mole fraction (about 2 percent) of CH4 is 20-30 times its solar value on both planets, it drops to its saturation limit (about 0.0001) at the Uranus tropopause, but remains high (about 2 percent) at the Neptune tropopause. This results in much greater mixing ratios of the product hydrocarbons in the stratosphere of Neptune. On both planets, the photolysis products of CH4 undergo condensation near the tropopause and the upper stratosphere. Voyager observations of the hydrocarbons at Uranus and those planned at Neptune are discussed, along with their implications for upper-atmospheric physics and thermochemistry.

Atreya, S. K.↗
NASA NTRS1990

Solar nebula origin for volatile gases in Halley's comet

The conditions for Comet Halley formation are presently considered in light of the application of physical and chemical processes in the solar nebula environments to the present data base on the composition of the comet's gases. Key molecular ratios are compared to solar nebula model predictions, and the nebular thermochemistry is quantified for a range of solar elemental compositions which correspond to varying water depletion states in the inner nebula. Assuming that inner nebula chemistry is catalyzed by reaction on grains, it is judged that the abundances of the volatile C species CH4, CO, and CO2 in Halley could have been supplied by the solar nebula.

Engel, Steffi↗
NASA NTRS1990

Hydrogen-silicon carbide interactions

A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamics maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicone carbide is the single stable solid phase in region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4 and SiH. Analyses of the kinetics of reaction for region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

Eckel, Andrew J.↗
NASA NTRS1992

Chemical vapor deposition modeling for high temperature materials

The formalism for the accurate modeling of chemical vapor deposition (CVD) processes has matured based on the well established principles of transport phenomena and chemical kinetics in the gas phase and on surfaces. The utility and limitations of such models are discussed in practical applications for high temperature structural materials. Attention is drawn to the complexities and uncertainties in chemical kinetics. Traditional approaches based on only equilibrium thermochemistry and/or transport phenomena are defended as useful tools, within their validity, for engineering purposes. The role of modeling is discussed within the context of establishing the link between CVD process parameters and material microstructures/properties. It is argued that CVD modeling is an essential part of designing CVD equipment and controlling/optimizing CVD processes for the production and/or coating of high performance structural materials.

Goekoglu, Sueleyman↗
NASA NTRS1992

Exhaust plumes and their interaction with missile airframes - A new viewpoint

The present, novel treatment of missile airframe-exhaust plume interactions emphasizes their simulation via a formal solution of the Reynolds-averaged Navier-Stokes (RNS) equation and is accordingly able to address the simulation requirements of novel missiles with nonconventional/integrated propulsion systems. The method is made possible by implicit RNS codes with improved artificial dissipation models, generalized geometric capabilities, and improved two-equation turbulence models, as well as by such codes' recent incorporation of plume thermochemistry and multiphase flow effects.

Dash, S. M.↗