SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Sandwich construction gives panels structural efficiency. Large panels with compound curvatures are formed from a honeycomb core faced with sheets of graphite/epoxy cloth and tape. Developed for pod on Space Shuttle, construction readily adapted to curved skin panels on cars, trucks, and airplanes.
Theoretical and observational aspects of an SEP violation are discussed. A two-times theory is presented as a possible framework to handle an SEP violation, and tests performed to check the compatibility of such violation with a host of data ranging from nucleosynthesis to geophysics are summarized. Also discussed are the dynamical equations needed to analyze radar ranging data to reveal an SEP violation and in particular the method employed by Shapiro and Reasenberg (1976).
The results of a spectroscopic survey of 21 early-type extreme emission line supergiants of the Large and Small Magellanic Clouds using IUE and optical spectra are presented. The combined observations are discussed and the literature on each star in the sample is summarized. The classification procedures and the methods by which effective temperatures, bolometric magnitudes, and reddenings were assigned are discussed. The derived reddening values are given along with some results concerning anomalous reddening among the sample stars. The derived mass, luminosity, and radius for each star are presented, and the ultraviolet emission lines are described. Mass-loss rates are derived and discussed, and the implications of these observations for the evolution of the most massive stars in the Local Group are addressed.
Explore the source record for details and available documents.
An intense and fast spike-like solar burst was built up of short time scale structures superimposed on an underlying gradual emission, the time evolution of which shows remarkable proportionality between hard X-ray and microwave fluxes. The finer time structures were best defined at mm-microwaves. At the peak of the event, the finer structures repeat every 30 x 60 ms. The more slowly varying component with a time scale of about 1 second was identified in microwave hard X-rays throughout the burst duration. It is suggested that X-ray fluxes might also be proportional to the repetition rate of basic units of energy injection (quasi-quantized). The relevant parameters of one primary energy release site are estimated both in the case where hard X-rays are produced primarily by thick-target bremsstrahlung, and when they are purely thermal. The relation of this figure to global energy considerations is discussed. Previously announced in STAR as N83-35983
Proportions of ingredients and sintering time/temperature schedule changed. Production process for lightweight, high-strength ceramic insulating tiles for Space Shuttle more than just scaled-up version of laboratory process for making small tiles. Boron in aluminum borosilicate fibers allows fusion at points where fibers contact each other during sintering, thereby greatly strengthening tiles structure.
The CO adsorption on a 40 atom cluster model of the (111) surface and a 36 atom cluster model of the (100) surface of the Pt3Ti alloy was studied. Parallel binding to high coordinate sites associated with Ti and low CO bond scission barriers are predicted for both surfaces. The binding of CO to Pt sites occurs in an upright orientation. These orientations are a consequence of the nature of the CO pi donation interactions with the surface. On the Ti sites the orbitals donate to the nearly empty Ti 3d band and the antibonding counterpart orbitals are empty. On the Pt sites, however, they are in the filled Pt 5d region of the alloy band, which causes CO to bond in a vertical orientation by 5 delta donation from the carbon end.
Observations about the relationship between seismic activity and astronomical phenomena are discussed. First, after investigating the seismic data (magnitude 7.0 and over) with the method of superposed epochs it is found that world seismicity evidently increased after the occurring of novae with apparent magnitude brighter than 2.2. Second, a great many earthquakes of magnitude 7.0 and over occurred in the 13th month after two of the largest ground level solar cosmic ray events (GLEs). The causes of three high level phenomena of global seismic activity in 1918-1965 can be related to these, and it is suggested that according to the information of large GLE or bright nova predictions of the times of global intense seismic activity can be made.
A synchrotron source model is presented for the origin of gamma-ray bursts from neutron stars. The field strength and length of time needed for electrons to lose sufficient energy in emitting the gamma rays are calculated, together with the efficiency of the process, limiting frequencies, and the energy output. A Monte Carlo simulation of the synchrotron radiation spectrum of an electron undergoing a self-consistent energy loss demonstrates that a process involving thermalized electrons can be sufficiently efficient to produce 30 keV gamma rays. Problems expected in using the current capabilities of detectors to scan for the projected energy spectra from fields of at least 3 x 10 to the 12th Gauss are discussed.
Distributions of galaxies and of clusters of galaxies have been investigated using the correlation function, the excess probability over random that there are two objects separated by a distance r. It is shown here that if the amplitudes of the cluster-cluster correlation function are made dimensionless, systematic changes with cluster richness vanish, implying scale invariance in the cluster process. The dimensionless galaxy-galaxy correlation seems stronger, implying gravitational enhancement on smaller scales.
Theoretical and experimental results are provided for the absorption of laser energy by a gas flow. A two-dimensional numerical model described the temperature field, fluid dynamics, variable absorptivity and gas dynamics. The model was tested using a hydrogen-seedant mixture injected with 10.6 micron laser radiation. The laser mix was selected to allow reduced temperature gradients and energy source terms. It was found possible, by varying parameters such as the laser power and flash pressure, to precisely position the peak absorptance region in higher speed flows. More refined models are being tested to achieve accurate absorptance predictions in flows below Mach 0.0001.
The results of a holographic interferometric and analytical examination of shock wave/turbulent boundary layer interactions occurring in a flow near a cone-cylinder intersection are reported. A Mach 2.85 flow with an Re of 18 million was used, along with cone angles of 12.5, 20 and 30 deg. Negligible, incipient and large scale separations were observed. The subsonic layer of the boundary always remained thin and was usually penetrated by the shock wave. An Abel transform, applied to the interferometric traces, yielded a great deal of data on the density field when combined with data from application of laser velocimeter, pressure tap and oil flow techniques.
The late stages of the beam-plasma instability are not yet completely understood. A better knowledge of the evolution of the beam is necessary to explain the results of the electron beam experiments carried out in the ionosphere. An alternative to the complete stabilization by quasi-linear (QL) diffusion is the parametric 'stabilization'. In this case the beam remains unstable for very long distances, while retaining its 'hot-beam' characteristics. A recent flight provides data that indicate the relevance of this mechanism in the evolution of the beam-plasma instability.
An entropy correction method for the unsteady full potential equation is presented. The unsteady potential equation is modified to account for entropy jumps across shock waves. The conservative form of the modified equation is solved in generalized coordinates using an implicit, approximate factorization method. A flux-biasing differencing method, which generates the proper amounts of artificial viscosity in supersonic regions, is used to discretize the flow equations in space. Comparisons between the present method and solutions of the Euler equations and between the present method and experimental data are presented. The comparisons show that the present method more accurately models solutions of the Euler equations and experiment than does the isentropic potential formulation.
Explore the source record for details and available documents.
Initial boundary value problems for the general scalar singularly perturbed parabolic equation in a cylindrical domain are studied. The one-dimensional reaction-diffusion equation is considered in the absence of convection. Then, the general one-dimensional and N-dimensional reaction-convection-diffusion equations are analyzed.
The theory for the generalized first invariant for adiabatic motion of charged particles in regions where there are large gradients in magnetic or electric fields is developed. The general condition for an invariant to exist in such regions is that the potential well in which the particle oscillates change its shape slowly as the particle drifts. It is shown how the Kruskal (1962) procedure can be applied to obtain expressions for the invariant and for drift velocities that are asymptotic in a smallness parameter epsilon. The procedure is illustrated by obtaining the invariant and drift velocities for particles traversing a perpendicular shock, and the generalized invariant is compared with the magnetic moment, and the drift orbits with the actual orbits, for a particular case. In contrast to the magnetic moment, the generalized first invariant is better for large gyroradii (large kinetic energies) than for small gyroradii. Expressions for the invariant when an electrostatic potential jump is imposed across the perpendicular shock, and when the particle traverses a rotational shear layer with a small normal component of the magnetic field are given.
An entropy correction method for the unsteady full potential equation is presented. The unsteady potential equation is modified to account for entropy jumps across shock waves. The conservative form of the modified equation is solved in generalized coordinates using an implicit, approximate factorization method. A flux-biasing differencing method, which generates the proper amounts of artificial viscosity in supersonic regions, is used to discretize the flow equations in space. Comparisons between the present method and solutions of the Euler equations and between the present method and experimental data are presented. The comparisons show that the present method more accurately models solutions of the Euler equations and experiment than does the isentropic potential formulation.