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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The Apollo 17 drill core - Chemistry of size fractions and the nature of the fused soil component

It is shown that the Apollo 17 drill core 70009-70001 is heterogeneous with depth, containing five stratigraphic units, and has a bulk soil chemistry governed by the coarse fractions because of their greater weight proportions. The four components (1) KREEP, (2) anorthositic gabbro, (3) mare basalt, and (4) orange glass are used to model the compositions of the coarse and fine fractions of the entire drill core. It is found that the chemistry of the fused soil component in the five stratigraphic units is more similar to the chemistry of the fine, less than 20-micron fractions than the coarse fraction, suggesting that agglutinates may prefferentially meld and replicate the chemistry of the finer size fractions. The sources of Zn are the orange/black glasses, and the Zn profile is anticorrelated with the maturity index of Morris et al (1979), indicating the liberation of Zn during soil maturation.

Laul, J. C.↗
NASA NTRS1982

Model calculations of the molecular composition of interstellar grain mantles

A chemical reaction scheme comprising gas phase as well as grain surface reactions is used for the numerical calculation of the chemical composition of mantles accreting on interstellar grains. The composition of the growing grain mantle is determined on the basis of the relative accretion rates of the gas phase molecules and diffusion-controlled surface reactions. Results show that grain mantles generally consist of the molecules H2O, H2CO, N2, O2, CO, CO2, H2O2, and NH3. A detailed examination of the formation of H2 on grain surfaces leads to the conclusion that it proceeds through hydrogen abstraction from such molecules as H2CO, H2S, N2H2, and N2H4. The IR characteristics of the calculated grain mantles are discussed with emphasis on the observed ice band at the 3250/cm wavelength.

Tielens, A. G. G. M.↗
NASA NTRS1983

Mechanics of composite materials: Recent advances; Proceedings of the Symposium, Virginia Polytechnic Institute and State University, Blacksburg, VA, August 16-19, 1982

The present conference on the mechanics of composites discusses microstructure's influence on particulate and short fiber composites' thermoelastic and transport properties, the elastoplastic deformation of composites, constitutive equations for viscoplastic composites, the plasticity and fatigue of metal matrix composites, laminate damping mechanisms, the micromechanical modeling of Kevlar/epoxy composites' time-dependent failure, the variational characterization of waves in composites, and computational methods for eigenvalue problems in composite design. Also discussed are the elastic response of laminates, elastic coupling nonlinear effects in unsymmetrical laminates, elasticity solutions for laminate problems having stress singularities, the mechanics of bimodular composite structures, the optimization of laminated plates and shells, NDE for laminates, the role of matrix cracking in the continuum constitutive behavior of a damaged composite ply, and the energy release rates of various microcracks in short fiber composites.

Hashin, Z.↗
NASA NTRS1984

Helicopters for the future

Technology needed to provide the basis for creating a widening rotary wing market include: well defined and proven design; reductions in noise, vibration, and fuel consumption; improvement of flying and ride quality; better safety; reliability; maintainability; and productivity. Unsteady transonic flow, yawed flow, dynamic stall, and blade vortex interaction are some of the problems faced by scientists and engineers in the helicopter industry with rotorcraft technology seen as an important development for future advanced high speed vehicle configurations. Such aircraft as the Boeing Vertol medium lift Model 360 composite aircraft, the Sikorsky Advancing Blade Concept (ABC) aircraft, the Bell Textron XV-15 Tilt Rotor Aircraft, and the X-wing rotor aircraft are discussed in detail. Even though rotorcraft technology has become an integral part of the military scene, the potential market for its civil applications has not been fully developed.

Ward, J. F.↗
NASA NTRS1985

Lateral distribution of high energy muons in EAS of sizes Ne approximately equals 10(5) and Ne approximately equals 10(6)

Muon energy spectra and muon lateral distribution in EAS were investigated with the underground magnetic spectrometer working as a part of the extensive air showers (EAS) array. For every registered muon the data on EAS are analyzed and the following EAS parameters are obtained, size N sub e, distance r from the shower axis to muon, age parameter s. The number of muons with energy over some threshold E associated to EAS of fixed parameters are measured, I sub reg. To obtain traditional characteristics, muon flux densities as a function of the distance r and muon energy E, muon lateral distribution and energy spectra are discussed for hadron-nucleus interaction model and composition of primary cosmic rays.

Bazhutov, Y. N.↗
NASA NTRS1985

A systematic study of magnetic braking in low-mass binaries

A short summary is given of Rappaport et al. (1983) which described results of extending a simplified stellar evolution code covering the evolution of low-mass compact binaries. Magnetic braking is probably an important process in the evolution of such binaries (such as cataclysmic variables and low-mass X-ray sources). The initial simplified code describes the mass-losing star as an n = 3/2 polytrope and was developed to study the evolution of binaries with a secondary of low mass (between 0.01 and 0.4 solar mass) when the angular momentum losses are due to gravitational radiation. In the extended code, a composite polytrope model is used for the secondary, wherein the structure of the radiative core is described by an n = 3 polytrope and the convective envelope by an n = 3/2 polytrope.

Verbunt, F.↗
NASA NTRS1984

An approach to developing specification measures

An approach to developing specification measures is described. A key feature of the approach is the introduction of a new requirements representation, the Composite Specification Model (CSM). Results are reported from an experiment in which the requirements for a real system are recast using the CSM. Specification measures are then extracted from the CSM representation of the system.

Agresti, W. W.↗
NASA NTRS1984

Investigation of specification measures for the Software Engineering Laboratory (SEL)

Requirements specification measures are investigated for potential application in the Software Engineering Laboratory. Eighty-seven candidate measures are defined; sixteen are recommended for use. Most measures are derived from a new representation, the Composite Specification Model, which is introduced. The results of extracting the specification measures from the requirements of a real system are described.

Source record↗
NASA NTRS1986

Simulation and analysis of antennas radiating in a complex environment

A numerical procedure for computing the high-frequency radiation patterns of antennas mounted on curved surfaces is described. The procedure utilizes the uniform geometrical theory of diffraction to examine the antenna system's performance, which is dependent on antenna radiation patterns. Composite ellipsoid models of fuselage shapes are developed and the formation of geodesic paths on the models is studied; the shape of the fuselage affects the radiation patterns. The actual field radiated by the source and scattered by the structure is calculated using the ray field technique. The numerical solution is applied to the analysis of the antenna radiation patterns of a military aircraft, private aircraft, and the Space Shuttle orbiter. Good correlation between the calculated and measured radiation patterns is noted verifying the usefulness and accuracy of the numerical procedure.

Kim, J. J.↗
NASA NTRS1987

Finite element modeling of electromagnetic propagation in composite structures

A finite element Galerkin formulation has been developed to study electromagnetic propagation in complex two-dimensional absorbing ducts. The reflection and transmission at entrance and exit boundaries are determined by coupling the finite element solutions at the entrance and exit to the eigenfunctions of an infinite uniform perfect conducting duct. Example solutions are presented for electromagnetic propagation with absorbing duct walls and propagating through dielectric-metallic matrix materials.

Baumeister, K. J.↗
NASA NTRS1987

Laboratory experiments in the study of the chemistry of the outer planets

It is shown that much information about planetary chemistry and physics can be gained through laboratory work. The types of experiments relevant to planetary research concern fundamental properties, spectral/optical properties, 'Miller-Urey' syntheses, and detailed syntheses. Specific examples of studies of the chemistry in the atmosphere of Titan are described with attention given to gas phase chemistry in the troposphere and the composition of model Titan aerosols. A list of work that still needs to be done is provided.

Scattergood, Thomas W.↗
NASA NTRS1989

The parent magmas of the SNC meteorites

Mineral compositions, partition coefficients, and computer-graphic representations of liquidus phase boundaries are used here to calculate parent magma compositions for Nakhla, Chassigny, and the xenocryst assemblage in EETA79001B, ALHA77005, and the EETA79001A groundmass. The calculated SNC parent magma compositions have low concentrations of Al2O3 and widely varying wollastonitite (CaO) component. In this regard they resemble basaltic komatiites, but their range of Wo is more extensive than that of basaltic komatiites and trace element characteristics are different. The calculated Nakhla parent magma has an unusually high Wo content and does not resemble any other known magmatic composition. A model of SNC petrogenesis is proposed.

Longhi, J.↗
NASA NTRS1990

Unique failure behavior of metal/composite aircraft structural components under crash type loads

Failure behavior results are presented on some of the crash dynamics research conducted with concepts of aircraft elements and substructure which have not necessarily been designed or optimized for energy absorption or crash loading considerations. To achieve desired new designs which incorporate improved energy absorption capabilities often requires an understanding of how more conventional designs behave under crash type loadings. Experimental and analytical data are presented which indicate some general trends in the failure behavior of a class of composite structures which include individual fuselage frames, skeleton subfloors with stringers and floor beams but without skin covering, and subfloors with skin added to the frame-stringer arrangement. Although the behavior is complex, a strong similarity in the static/dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models. It is believed that the thread of similarity in behavior is telling the designer and dynamists a great deal about what to expect in the crash behavior of these structures and can guide designs for improving the energy absorption and crash behavior of such structures.

Carden, Huey D.↗
NASA NTRS1990

Behavior of composite/metal aircraft structural elements and components under crash type loads: What are they telling us

Failure behavior results are presented from crash dynamics research using concepts of aircraft elements and substructure not necessarily designed or optimized for energy absorption or crash loading considerations. To achieve desired new designs which incorporate improved energy absorption capabilities often requires an understanding of how more conventional designs behave under crash loadings. Experimental and analytical data are presented which indicate some general trends in the failure behavior of a class of composite structures which include individual fuselage frames, skeleton subfloors with stringers and floor beams but without skin covering, and subfloors with skin added to the frame-stringer arrangement. Although the behavior is complex, a strong similarity in the static and dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models. It is believed that the similarity in behavior is giving the designer and dynamists much information about what to expect in the crash behavior of these structures and can guide designs for improving the energy absorption and crash behavior of such structures.

Carden, Huey D.↗
NASA NTRS1990

The influence of CO ice on the activity and the near-surface differentiation of comet nuclei

A comet nucleus model whose composition is a homogeneous mixture of water ice, CO ice, and dust, in a Halley-type orbit, is presently used to investigate the role of unclathrated CO ice in the activity and near-surface differentiation of comet nuclei. Temperatures of water and CO ice surfaces, CO gas and water steam fluxes, and depths of CO ice, are presented as functions of orbital position. It is determined that CO ice should always exist within 3 m of the surface; CO gas production exceeds water steam production beyond 2.5 AU, with consequences for the planned in situ elemental analysis of nuclei.

Fanale, Fraser P.↗
NASA NTRS1990

Temporal and vertical distribution of acidity and ionic composition in clouds - Comparison between modeling results and observations

Cyclic temporal variations of pH and ionic concentration in sampled clouds which traversed the Mt. Mitchell State Park (North Carolina) site during the summers of 1986, 1987, and 1988 are reported. These clouds typically had a measured pH minimum during their initial and final stages. The cause of this basic cylic pattern is attributed to sampling at different vertical levels of the cloud. This is substantiated by visual observations made while sampling. The results also suggest that the measured pH patterns do not always exhibit minima during the formative and dissipative stages of the cloud, apparently in response to the underlying dynamical processes. The relationship between temporal pH measurements made at a stationary site to vertical cloud levels provides insights into the physical processes (e.g., nucleation scavenging near cloud base, dry air entrainment near cloud top) influencing the observed cloud-water chemistry on a real-time basis and would improve cloud chemistry models.

Defelice, T. P.↗
NASA NTRS1990

Failure behavior of generic metallic and composite aircraft structural components under crash loads

Failure behavior results are presented from crash dynamics research using concepts of aircraft elements and substructure not necessarily designed or optimized for energy absorption or crash loading considerations. To achieve desired new designs incorporating improved energy absorption capabilities often requires an understanding of how more conventional designs behave under crash loadings. Experimental and analytical data are presented which indicate some general trends in the failure behavior of a class of composite structures including individual fuselage frames, skeleton subfloors with stringers and floor beams without skin covering, and subfloors with skin added to the frame-stringer arrangement. Although the behavior is complex, a strong similarity in the static/dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models.

Carden, Huey D.↗