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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Glass polyimide honeycomb cores for advanced space transportation systems

The use of a glass fiber reinforced polyimide honeycomb was considered for various applications requiring lightweight stiff structures which may experience temperatures up to 600K. The experiences and results of fabricating these core types are reported. The process parameters and most desirable characteristics are noted. The differences in considering resins for making laminates versus their use in surface coatings are stressed. This comparison is made to explain the problems encountered in using the three new resin types for dipping honeycomb to the desired density. Some properties and the effect of post cure, forming and ventilating techniques for the condensation polyimide core types are presented.

Brentjes, J.↗
NASA NTRS1989

Doppler radar observations of the evolution of a small convective storm during Cohmex

Doppler radar observations of a deep convection that developed along the Alabama-Tennesse border on July 14, 1986 are analyzed. The evolution and structure of the convective storm are examined. Two convective cores are observed and both having a radius of about 1 km and maximum reflectivities of about 5 dBz; a third cell is also detected later in the region between the northern and southern cells. It is noted that the northern cell is the most dominant possessing an updraft through the region of maximum reflectivity. Diagrams of the vertical structure of the cells are provided.

Moore, Patrick D.↗
NASA NTRS1980

The core and the magnetic field of Uranus

The existence of a magnetic field on Uranus is suggested by the tentative observation of 0.5 MHz pulses from the planet which are analogous to the Jovian decametric radiation. Analysis of a recent three-layer model leads to the conclusion that the electrical conductivity, physical state, and thermal gradients are such that a thermally driven hydromagnetic dynamo is probably operating in the core. An investigation is conducted to see whether the considered structure is suitable for the generation of a field. It is found that the existence of a magnetic field on Uranus can be understood as being a natural result of gravitational differentiation in a liquid, metallic core. The presence of a heat source in the core implies that the central temperature is approximately 8400 K rather than 7000 K in the original model

Torbett, M.↗
NASA NTRS1972

Photoemission studies of wurtzite zinc oxide.

The electronic structure of wurtzite zinc oxide, investigated over the widest possible photon energy range by means of photoemission techniques, is described. Of particular interest among the results of the photoemission study are the location of the Zn 3rd core states, the width of the upper valence bands, and structure in the conduction-band and valence-band density of states.

Powell, R. A.↗
NASA NTRS2009

Prediction of Launch Vehicle Ignition Overpressure and Liftoff Acoustics

The LAIOP (Launch Vehicle Ignition Overpressure and Liftoff Acoustic Environments) program predicts the external pressure environment generated during liftoff for a large variety of rocket types. These environments include ignition overpressure, produced by the rapid acceleration of exhaust gases during rocket-engine start transient, and launch acoustics, produced by turbulence in the rocket plume. The ignition overpressure predictions are time-based, and the launch acoustic predictions are frequency-based. Additionally, the software can predict ignition overpressure mitigation, using water-spray injection into the rocket exhaust stream, for a limited number of configurations. The framework developed for these predictions is extensive, though some options require additional relevant data and development time. Once these options are enabled, the already extensively capable code will be further enhanced. The rockets, or launch vehicles, can either be elliptically or cylindrically shaped, and up to eight strap-on structures (boosters or tanks) are allowed. Up to four engines are allowed for the core launch vehicle, which can be of two different types. Also, two different sizes of strap-on structures can be used, and two different types of booster engines are allowed. Both tabular and graphical presentations of the predicted environments at the selected locations can be reviewed by the user. The output includes summaries of rocket-engine operation, ignition overpressure time histories, and one-third octave sound pressure spectra of the predicted launch acoustics. Also, documentation is available to the user to help him or her understand the various aspects of the graphical user interface and the required input parameters.

Casiano, Matthew↗
NASA NTRS1990

Spacecraft protective structures design optimization

The optimization of spacecraft protective structures design to defeat hypervelocity impacts of meteoroids and space debris is presented. A space debris environment model is incorporated into an overall optimization methodology employing engineering models developed to predict protective structures design requirements for hypervelocity impact loads. Several nonlinear optimization techniques are used to generate design parametrics based on environment, mission, and configuration variables for the Space Station Core Module Configuration. Results indicate that careful consideration of the spacecraft structural configuration and materials can partially offset the design consequences of dramatic increases in the orbital space debris environment. Furthermore, the use of nonlinear optimization techniques coupled with hypervelocity impact engineering models can provide significant design tradeoff insight through the use of parametric analyses.

Mog, Robert A.↗
NASA NTRS1981

Closed coronal structures. III - Comparison of static models with X-ray, EUV, and radio observations

Numerical models of static coronal loops in energy balance are compared with high spatial resolution observations of extreme ultraviolet lines, broad-band X-ray emission, and interferometric observations at 2.8 cm of a solar active region. Difficulties of using scaling laws to test static models of coronal loops are reviewed. The theoretical model used for the comparison is summarized; the detailed X-ray, EUV, and microwave observations of the selected active region are presented; and the comparison of the model with the observations is performed. It is shown that simple static models with conductive flux vanishing at the loop base reproduce satisfactorily the observed properties in the upper portion of loop structures from compact, high-pressure loops in the core of the region to more extended, fainter loops and to large-scale loops interconnecting different active regions. Effects of changing loop parameters are investigated, and it is argued, that in contrast to the present approach, scaling laws cannot be used to discriminate between different static energy balance models. Some discrepancy is found between model predictions and observations for the lower sections of loop structures. Possible causes of the discrepancy are discussed.

Pallavicini, R.↗
NASA NTRS1998

Abundances of ethylene oxide and acetaldehyde in hot molecular cloud cores

We have searched for millimetre-wave line emission from ethylene oxide (c-C2H4O) and its structural isomer acetaldehyde (CH3CHO) in 11 molecular clouds using SEST. Ethylene oxide and acetaldehyde were detected through multiple lines in the hot cores NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2. Acetaldehyde was also detected towards G10.47+0.03, G322.2+0.6, and Orion 3'N, and one ethylene oxide line was tentatively detected in G10.47+0.03. Column densities and rotational excitation temperatures were derived using a procedure which fits the observed line intensifies by finding the minimum chi 2-value. The resulting rotational excitation temperatures of ethylene oxide and acetaldehyde are in the range 16-38 K, indicating that these species are excited in the outer, cooler parts of the hot cores or that the excitation is significantly subthermal. For an assumed source size of 20", the deduced column densities are (0.6-1)x10(14) cm-2 for ethylene oxide and (2-5)x10(14) cm-2 for acetaldehyde. The fractional abundances with respect to H2 are X[c-C2H4O]=(2-6)xl0(-10), and X[CH3CHO]=(0.8-3)x10(-9). The ratio X[CH3CHO]/X[c-C2H4O] varies between 2.6 (NGC 6334F) and 8.5 (G327.3-0.6). We also detected and analysed multiple transitions of CH3OH, CH3OCH3, C2H5OH, and HCOOH. The chemical, and possibly evolutionary, states of NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2 seem to be very similar.

Non-NASA Center↗
NASA NTRS1990

Advanced fabrication technology for high speed aircraft structures

An overview of the development of the weld-brazing process for fabricating Ti-6Al-4V skin-stiffened panels, a brazing process for fabricating Bsc/Al titanium honeycomb core panels, and the enhanced diffusion bonding (EDB) process for fabricating Ti-14Al-21Nb titanium aluminide structural elements are presented. Data presented include the shear strengths of full-scale weldbrazed Ti-6Al-4V skin stiffened and Bsc/Al titanium honeycomb core sandwich panels designed to meet the requirements of an upper wing panel on the NASA YF-12. These results verified that the materials, fabrication processes, and structural concepts were qualified for Mach 3 flight. Shear strengths of each of the panel concepts following flight service evaluation are also reported. Comparisons made with the cost and weight of the original wing panel indicated that the weldbrazed titanium panels resulted in a 15-20 percent cost savings and the brazed Bsc/Al panel showed a 30 percent weight savings. It was also shown that the strengths of the EDB joints were sufficient to develop stresses in the Ti-14Al-21Nb face sheets of the sandwich structure which were above the yield strength of the material.

Bales, T. T.↗
NASA NTRS1997

Damage-Tolerance Characteristics of Composite Fuselage Sandwich Structures with Thick Facesheets

Damage tolerance characteristics and results from experimental and analytical studies of a composite fuselage keel sandwich structure subjected to low-speed impact damage and discrete-source damage are presented. The test specimens are constructed from graphite-epoxy skins borided to a honeycomb core, and they are representative of a highly loaded fuselage keel structure. Results of compression-after-impact (CAI) and notch-length sensitivity studies of 5-in.-wide by 10-in.long specimens are presented. A correlation between low-speed-impact dent depth, the associated damage area, and residual strength for different impact-energy levels is described; and a comparison of the strength for undamaged and damaged specimens with different notch-length-to-specimen-width ratios is presented. Surface strains in the facesheets of the undamaged specimens as well as surface strains that illustrate the load redistribution around the notch sites in the notched specimens are presented and compared with results from finite element analyses. Reductions in strength of as much as 53.1 percent for the impacted specimens and 64.7 percent for the notched specimens are observed.

McGowan, David M.↗
NASA NTRS1967

Method of making inflatable honeycomb Patent

Technique for making foldable, inflatable, plastic honeycomb core panels for use in building and bridge structures, light and radio wave reflectors, and spacecraft

Schnitzer, E.↗
NASA NTRS1978

Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature

In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.

Parkin, C. W.↗
NASA NTRS1984

Airfoil interaction with impinging vortex

The tip of a finite-span airfoil was used to generate a streamwise vortical flow, the strength of which could be varied by changing the incidence of the airfoil. The vortex that was generated traveled downstream and interacted with a second airfoil on which measurements of lift, drag, and pitching moment were made. The flow field, including the vortex core, was visualized in order to study the structural alterations to the vortex resulting from various levels of encounter with the downstream airfoil. These observations were also used to evaluate the accuracy of a theoretical model.

Mcalister, K. W.↗
NASA NTRS1983

Composite casting/bonding construction of an air-cooled, high temperature radial turbine wheel

A composite casting/bonding technique has been developed for the fabrication of a unique air-cooled, high temperature radial inflow turbine wheel design applicable to auxilliary power units with small rotor diameters and blade entry heights. The 'split blade' manufacturing procedure employed is an alternative to complex internal ceramic coring. Attention is given to both aerothermodynamic and structural design, of which the latter made advantageous use of the exploration of alternative cooling passage configurations through CAD/CAM system software modification.

Hammer, A. N.↗
NASA NTRS1985

Does orientation affect the smoothness of parsec-scale radio jets?

The compact, nonthermal radio sources which are studied with very-long-baseline interferometry (VLBI) are often found to have a linear structure with a bright, nearly unresolved component at one end. This asymmetric structure is usually referred to as a 'core-jet' morphology. In some sources there are bright bumps or knots - regions of enhanced radio emission - along the 'jets', while other sources have relatively smooth, featureless jets. This paper reports the result of a study of the differences between compact radio sources with bumpy and smooth jets. It is concluded that most, if not all, of the difference in jet smoothness can be attributed to the orientation of the radio axis with respect to the line of sight. Thus, the VLBI observations do not necessarily imply that there are intrinsic differences in the smoothness of parsec-scale radio jets.

Jones, D. L.↗
NASA NTRS1984

Single mode acoustic fiber waveguide

The single mode operation of a clad rod acoustic waveguide is described. Unlike conventional clad optical and acoustic waveguiding structures which use modes confined to a central core surrounded by a cladding, this guide supports neither core nor cladding modes but a single interface wave field on the core-cladding boundary. The propagation of this bound field and the potential improved freedom from spurious responses is discussed.

Jackson, B. S.↗
NASA NTRS1992

On the formation and evolution of plasmoids - A survey of ISEE 3 Geotail data

The magnetic and plasma properties of plasmoids, their evolution with distance downtail, and the effect of the direction of the IMF on the plasmoid magnetic configuration were investigated by examining the ISEE 3 magnetometer and electron plasma measurements of the 1983 ISEE 3 Geotail Mission. Both data sets were systematically examined for the presence of bipolar magnetic signatures that occur while ISEE 3 was in the plasma sheet. Results revealed 366 events consistent with this signature while ISEE was in the plasma sheet. It was found that plasmoids are characterized by high-speed plasma flow and that many of them have a well-defined magnetic core field characterized by a field strength maximum at the center of the pass through the structure. Once completely formed, plasmoids are relatively stable. It was found that the size, velocity, magnetic core strength, and Bz field amplitude of plasmoids do not depend on the distance downtail beyond -100 R(E).

Moldwin, Mark B.↗