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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Identification of frequency components in electron content data by nonlinear filtering

A nonlinear filtering technique, called multiplicative homomorphic signal processing, is used to identify three groups of frequency components in electron content data. The first group of components results from the modulation of solar activity produced by the 27 day solar rotation. The second group is of lunar origin. The lunar frequencies are caused by nonlinear processes which probably occur in the dynamo region. The precise nature of these processes is not fully understood. The third group of frequency components, with a fundamental period of 13.9 days, has an unknown origin.

Bernhardt, P. A.↗
NASA NTRS1980

Composite components on commercial aircraft

The paper considers the use of composite components in commercial aircraft. NASA has been active in sponsoring flight service programs with advanced composites for the last 10 years, with 2.5 million total composite component hours accumulated since 1970 on commercial transports and helicopters with no significant degradation in residual strength of composite components. Design, inspection, and maintenance procedures have been developed; a major NASA/US industry technology program has been developed to reduce fuel consumption of commercial transport aircraft through the use of advanced composites.

Dexter, H. B.↗
NASA NTRS1980

Narrow-band Jovian kilometric radiation - A new radio component

The paper describes a new component of Jupiter's radio spectrum. This component emits in a very narrow bandwidth (less than 40 kHz) near 100 kHz. Its waveform is a very smooth and gradual rise and subsequent fall in intensity over typically two hours. The emission is polarized with left-hand polarization associated with the Jovian northern magnetic hemisphere and righthand with the south. The most interesting feature of the emission is its deviation from a strict System III rotation period repetition rate. The emission source of this narrow-band component clearly rotates slower by 3-5% than all other forms of Jovian radio emission. Propagation considerations coupled with this observed lack of corotation point to a source region near the magnetic equatorial plane at the outer 'edge' of the Io plasma torus.

Kaiser, M. L.↗
NASA NTRS1980

Component-adaptive grid embedding

One of the major problems related to transonic flow prediction about realistic aircraft configuration is the generation of a suitable grid which encompasses such configurations. In general, each aircraft component (wing, fuselage, nacelle) requires a grid system that is usually incompatible with the grid systems of the other components; thus, the implementation of finite-difference methods for such geometrically-complex configurations is a difficult task. An approach was developed to treat such a problem. The basic idea is to generate different grid systems, each suited for a particular component. Thus, the flow field domain is divided into overlapping subdomains of different topology. These grid systems are then interfaced with each other in such a way that stability, convergence speed and accuracy are maintained.

Atta, E. H.↗
NASA NTRS1980

Estimation procedures to measure and monitor failure rates of components during thermal-vacuum testing

Estimation procedures are described for measuring component failure rates, for comparing the failure rates of two different groups of components, and for formulating confidence intervals for testing hypotheses (based on failure rates) that the two groups perform similarly or differently. Appendix A contains an example of an analysis in which these methods are applied to investigate the characteristics of two groups of spacecraft components. The estimation procedures are adaptable to system level testing and to monitoring failure characteristics in orbit.

Williams, R. E.↗
NASA NTRS1981

Radiation studies of optical and electronic components used in astronomical satellite studies

The synchronous orbit of the IUE carries the satellite through Earth's outer electron belt. A 40 mCi Sr90 source was used to simulate these electrons. A 5 mCi source of Co60 was used to simulate bremmstrahlung. A 10 MeV electron Linac and a 1.7 MeV electron Van de Graaf wer used to investigate the energy dependence of radiation effects and to perform radiations at a high flux rate. A 100 MeV proton cyclotron was used to simulate cosmic rays. Results are presented for three instrument systems of the IUE and measurements for specific components are reported. The three instrument systems were the ultraviolet converter, the fine error sensor (FES), and the SEC vidicon camera tube. The components were optical glasses, electronic components, silicon photodiodes, and UV window materials.

Becher, J.↗
NASA NTRS1981

Preliminary vibration, acoustic, and shock design and test criteria for components on the Lightweight External Tank (LWT)

The Space Shuttle LWT is divided into zones and subzones. Zones are designated primarily to assist in determining the applicable specifications. A subzone (general Specification) is available for use when the location of the component is known but component design and weight are not well defined. When the location, weight, and mounting configuration of the component are known, specifications for appropriate subzone weight ranges are available. Along with the specifications are vibration, acoustic, shock, transportation, handling, and acceptance test requirements and procedures. A method of selecting applicable vibration, acoustic, and shock specifications is presented.

Source record↗
NASA NTRS1980

Testing of ceramic gas turbine components under service-like conditions

The German firm MTU, Munich, West Germany, is developing gas turbine components made of special ceramics (silicon nitride, silicon carbide) which can withstand temperatures up to 1600 K. Various components such as the combustor and turbine wheel are being developed. Various preliminary tests of components are discussed.

Siebmanns, W.↗
NASA NTRS1981

Two-component Fermi-liquid theory - Equilibrium properties of liquid metallic hydrogen

It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.

Oliva, J.↗
NASA NTRS1982

A new interstellar component in the spectrum of HD 72127A

New high dispersion observations are reported of the very strong, broad interstellar K line of Ca II in the spectrum of HD 72127A, a star located near a filament of the Vela supernova remnant. When compared with similar observations made in 1977, the new data reveal temporal variability of the interstellar absorption, as shown both by the presence of a new, sixth line component and by a 25% increase in the total equivalent width of the K line. All five Ca II components which were seen in both years show very large column-density ratios N(Ca II) /N(Na I) at least equal to 9, probably arising from anomalously large interstellar gas-phase abundances of Ca caused by disruption of interstellar grains. Marked differences in the structure of the K line between the two early-type components of this binary star, which are separated by only 3000 AU, are confirmed.

Hobbs, L. M.↗
NASA NTRS1982

Apollo 11 breccias and soils - Aluminous mare basalts or multi-component mixtures

This paper examines the chemistry of Apollo 11 welded breccias and soils and attempts to ascertain whether the compositional variations in these samples reflect the comminuted remains of an unsampled high alumina basalt, or whether they result from mixing of mare basalts with more aluminous highland components. The data show strong linear compositional trends that are not consistent with magmatic processes. Instead, they indicate two-component mixing involving high-K basalt and an already well-mixed soil component. This is consistent with impact mixing of soil with a high-K mare basalt unit that is stratigraphically above other mare basalt units.

Rhodes, J. M.↗
NASA NTRS1982

The response of Galileo aft cover components to laser radiation

The aft region of the Galileo probe will be subjected to severe heat transfer rates dominated by the radiation contributions. To assess the response of several vehicle aft region components to thermal radiation, tests employing a 10 KW CO2 laser were conducted. The experiments evaluated the annulus/aft cover interface, the umbilical feedthrough assembly and the mortar cover seal assembly. Experimental evidence of the response of the phenolic nylon heatshield and quantitative measures of its effect on gap geometries of several vehicle components were acquired. In addition, qualitative measures of the survivability of the irradiated components were obtained.

Metzger, J. W.↗
NASA NTRS1982

Net shape fabrication of Alpha Silicon Carbide turbine components

Development of Alpha Silicon Carbide components by net shape fabrication techniques has continued in conjunction with several turbine engine programs. Progress in injection molding of simple parts has been extended to much larger components. Turbine rotors fabricated by a one piece molding have been successfully spin tested above design speeds. Static components weighing up to 4.5 kg and 33 cc in diameter have also been produced using this technique. Use of sintering fixtures significantly improves dimensional control. A new Si-SiC composite material has also been developed with average strengths up to 1000 MPa (150 ksi) at 1200 C.

Storm, R. S.↗
NASA NTRS1982

DE-1 observations of the polar wind - A heated and an unheated component

High altitude observations made by DE-1 in the polar regions indicate that the polar wind consists of both a heated and an unheated component. The unheated component constitutes what may be called the 'classical polar wind' while the heated component is thought to be the result of the interaction of the primal polar wind with regions of ion perpendicular heating. The altitude at which the heating occurs is estimated to lie between 8000 and 12000 km.

Gurgiolo, C.↗
NASA NTRS1982

The early-type component in v1 Sagittarii

Four low-resolution UV spectra of v1 Sgr (cK2) were obtained with the IUE satellite to investigate the nature of the hot component in this object, which was detected in the Astronomical Netherlands Satellite UV photometric data. The IUE results show that the spectral energy distribution of v1 Sgr in the FUV is comparable to that of a B9 star. FUV flux level, when compared with that of the mid-ultraviolet flux level, indicates that the luminosity of the hot component is roughly equivalent to that of a main-sequence star, assuming that the mid-ultraviolet flux is dominated almost entirely by a K2 I object. No discernible spectral features are present in the FUV, contrary to what may be expected in a star of B9 spectral type. Two possible interpretations are suggested: the hot component is a rapidly rotating star, or an accretion disk surrounding a central object which could be a collapsed star is being observed.

Kondo, Y.↗
NASA NTRS1982

Two-component proton spectra in the inner Saturnian magnetosphere

Measurements obtained by the Pioneer-11 spacecraft in Saturn's inner magnetosphere revealed the presence of a high energy proton component, primarily confined within the orbits of satellites Enceladus and Mimas. The high energy component was interpreted as due to protons from cosmic ray neutron albedo decay interactions with the Saturnian rings and, secondarily, the planetary atmosphere, but without detailed knowledge of the differential or integral spectrum. The main objective of the present investigation is to examine in some detail the ion spectra in the considered region of the magnetosphere, and to provide some of the basic input necessary in evaluating various models of energetic particle-ring interactions. The conducted measurements clearly show the presence of low energy ions and electrons inside the orbit of Mimas and provide a measure of the evolution of the hot ion spectrum observed inside the orbit of Rhea into a two-component power law spectrum inside the orbits of Enceladus and Mimas.

Krimigis, S. M.↗
NASA NTRS1982

Flight service evaluation of composite helicopter components

This first interim report presents the technical background for including environmental effects in the design of helicopter composite structures, and test results after approximately two year field exposure of components and panels. Composite structural components were removed from Sikorsky S-76 helicopters commercially operated in the Gulf Coast region of Louisiana. Fatigue tests were conducted for a graphite/epoxy tail rotor spar and static test for a graphite/epoxy and Kevlar/epoxy stabilizer. Graphite/epoxy and Kevlar/epoxy panels are being exposed to the outdoor environment in Stratford, Connecticut and West Palm Beach, Florida. For this reporting period the two year panels were returned, moisture measurements taken, and strength tests conducted. Results are compared with initial type certificate strengths for components and with initial laboratory coupon tests for the exposed panels. Comparisons are also presented with predicted and measured moisture contents.

Rich, M. J.↗
NASA NTRS1982

Failure characteristics of graphite-epoxy structural components loaded in compression

Failure characteristics of compressively loaded graphite-epoxy components are described. Experimental results for both strength-critical laminates and structural components with postbuckling strength are presented. Effects of low speed impact damage and circular holes on compressive strength are discussed. Delamination and shear crippling failure mechanisms that limit the performance of strength-critical laminates are described. Transverse shear and skin-stiffener separation failure mechanisms that limit the performance of components with postbuckling strength are also described. The influence of matrix properties on compressive strength improvements for impact damaged laminates is discussed. Experimental data and results from a failure analysis for strength-critical laminates with cutouts are discussed and compared with impact damage results. Typical postbuckling test results are compared with analytical predictions.

Starnes, J. H., Jr.↗