Search NASA⌕ Search

SEARCH · Search NASA

Results for “Extrapolation”

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.

At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Longitudinal variations of thermospheric composition indicating magnetic control of polar heat input.

Measurement of neutral N2, O, and He densities from Ogo 6 over the south polar region during magnetically quiet periods in late August and early September 1969. It is found that N2 densities, when they are extrapolated to a common altitude, maximize at about 0800 UT near 70 deg invariant latitude. The density of He has a minimum at this time, and the density of O has a slight maximum. It is proposed that these phenomena are the result of cyclic variations in soft electron precipitation, which heats the thermosphere either directly or through enhanced Joule heating. This heat energy would increase the gas temperature, the increase in the gas temperature leading to the N2 increase, and would vary the composition by generation of a wind system.

Hedin, A. E.↗
NASA NTRS1972

Two successful geomagnetic-field-line tracing experiments.

Two field-line tracing experiments were conducted on an L = 1.26 magnetic flux tube over Kauai, Hawaii. Barium vapor was created by the detonation of a highly explosive shaped charge aligned with the geomagnetic field at a 467-km altitude. Barium ions traveled along the field line to the conjugate ionosphere in a tube 3 to 5 km in diameter, producing a visible streak along the entire 6900-km path length. Electric fields perpendicular to the magnetic field caused the ions to drift away from the true conjugate during transit, but extrapolation from subsequent ion drift rates allowed the conjugate to be identified and compared with several field models. Differing ion drift rates and directions at the conjugate points indicated that the electric field is not transferred unattenuated along field lines.

Wescott, E. M.↗
NASA NTRS1972

The NASA/GE quiet engine 'A.'

The National Aeronautics and Space Administration and the General Electric Company are jointly developing two low noise propulsion technology demonstrators (Engine 'A' and 'C' incorporating respectively a low tip speed and high tip speed fan) under the Experimental Quiet Engine Program. The acoustic and aerodynamic performance characteristics of Engine 'C' which is currently on test will be reported at a later date. The present paper describes the design, component development and engine evaluation of the 'A' demonstrator. The aerodynamic and acoustic performance obtained on the fan component are discussed. The demonstrator engine acoustic test program is outlined. The effect of inlet geometry and duct acoustic treatment are presented. The static acoustic data are extrapolated to flight and compared with the FAA noise regulations.

Benzakein, M. J.↗
NASA NTRS1972

Viscosity and thermal conductivity of moderately dense gas mixtures.

Derivation of a simple, semitheoretical expression for the initial density dependence of the viscosity and thermal conductivity of gaseous mixtures in terms of the appropriate properties of the pure components and of their interaction quantities. The derivation is based on Enskog's theory of dense gases and yields an equation in which the composition dependence of the linear factor in the density expansion is explicit. The interaction quantities are directly related to those of the mixture extrapolated to zero density and to a universal function valid for all gases. The reliability of the formulation is assessed with respect to the viscosity of several binary mixtures. It is found that the calculated viscosities of binary mixtures agree with the experimental data with a precision which is comparable to that of the most precise measurements.

Wakeham, W. A.↗
NASA NTRS1972

Electron showers of high primary energy in lead.

The development of electron cascade showers in a lead-scintillator sandwich of 8 plastic scintillators in about 20 radiation lengths of lead has been investigated. This detector, which was used for cosmic-ray studies, has been calibrated with electrons with energies from 2 to 15 GeV at SLAC. Measured shower profiles are presented, and expressions are given which allow an extrapolation of the measured data up to energies around 1000 GeV. The results are compared with analytical shower theories and Monte Carlo calculations.

Mueller, D.↗
NASA NTRS1972

Type III solar noise observed below 100 kHz on OGO 3.

Type III solar noise bursts have been observed in the frequency range 25-100 kHz with the VLF detector on OGO 3. The bursts decrease in frequency from 100 kHz (the highest frequency of observation) to as low as 25 kHz in approximately 45 min. The intensity at 100 kHz increases for about 20 min then decays over a period of approximately 1 hr. The variation of the intensity with time becomes less regular at lower frequencies. Bursts are predominantly associated with west-limb flares. Their commencement at 100 kHz tends to follow type III bursts observed at 2-4 MHz by about 10 min. Observed drift rates and decay times correspond roughly to those extrapolated from higher frequency measurements.

Dunckel, N.↗
NASA NTRS1972

Comparative cut-bar thermal conductivity apparatus.

Construction details, error analysis, and typical data for a rapid comparative device for thermal conductivity measurements are presented. The apparatus consists of a comparative cut-bar arrangement contained in a bell-jar. The cylinder shaped specimen is placed between two ARMCO-iron meter bars of the same diameter. The upper bar is equipped with a heater, while the lower one is terminated in a heat sink. The temperature gradient along the bars is measured with a series of copper/constantan microthermocouples, spot welded to them. The assembly is held together by loading the bars to a desired pressure, via a pneumatic cylinder. Contact resistance at the boundaries between the specimen and the meter bars is minimized by using a Hg/In/Ga alloy film at the interface and sufficient loading force. The gradients determined for the meter bars then may be extrapolated to the boundaries yielding the temperature drop along the specimen. Using two different length specimens, the magnitude of the temperature drop across the interface can be computed, or the true gradient along the specimen can be obtained from the difference in overall temperature drops and lengths.

Gaal, P. S.↗
NASA NTRS1972

New lines of neon ions in the range 50-200 A.

About 180 new spectral lines of Ne V, Ne VI, Ne VII, and Ne VIII have been measured and identified on spectrograms obtained from a large theta-pinch apparatus. The spectrograms covered the range from 50 to 200 A. The lines were classified by means of isoelectronic extrapolations and interpolations.

Hermansdorfer, H.↗
NASA NTRS1973

Microwave emission from granular silicates

Experimental finding is that mass absorption coefficient is independent of frequency but highly dependent on moisture content; effective conductivity increases with frequency, and low tangent is independent of frequency. Computed values of electrical properties are in rough numerical agreement with extrapolated laboratory values on other silicate materials.

Conel, J. E.↗
NASA NTRS1972

The interaction of the solar wind with the interstellar medium

The expected characteristics of the solar wind, extrapolated from the vicinity of the earth are described. Several models are examined for the interaction of the solar wind with the interstellar plasma and magnetic field. Various aspects of the penetration of neutral interstellar gas into the solar wind are considered. The dynamic effects of the neutral gas on the solar wind are described. Problems associated with the interaction of cosmic rays with the solar wind are discussed.

Axford, W. I.↗
NASA NTRS1972

The peculiar O6f star HD 148937 and the symmetrically surrounding nebulae

The ultraviolet continuum of the star is observed and, after standard reddening corrections are applied, it is found to be hotter than a model 05 V star. The Of star and its two companions are photometered around wavelength 4640, 4686, and 4861 A. The results confirm Westerlund's (1960) absolute visual magnitude of about -6 for the Of star and confirm his rejection of NGC 6164-5 as a planetary nebula. Peculiarities of the system of nebular shells around HD 148937, of which NGC 6164-5 are the innermost, are discussed with reference to radiofrequency data. A standard extrapolation from the optical flux density of NGC 6164-5 predicts a detectable radio source but it does not appear in the relevant surveys.

Johnson, H. M.↗
NASA NTRS1972

UK-5 Van Allen belt radiation exposure: A special study to determine the trapped particle intensities on the UK-5 satellite with spatial mapping of the ambient flux environment

Vehicle encountered electron and proton fluxes were calculated for a set of nominal UK-5 trajectories with new computational methods and new electron environment models. Temporal variations in the electron data were considered and partially accounted for. Field strength calculations were performed with an extrapolated model on the basis of linear secular variation predictions. Tabular maps for selected electron and proton energies were constructed as functions of latitude and longitude for specified altitudes. Orbital flux integration results are presented in graphical and tabular form; they are analyzed, explained, and discussed.

Stassinopoulos, E. G.↗
NASA NTRS1972

Predicted trapped particle radiation levels for Tiros-N

Vehicle encountered electron and proton fluxes were calculated for a set of nominal TIROS-N trajectories with new computational methods and new electron environment models. Temporal variations in the electron data were considered and partially accounted for. Estimates of energetic solar proton fluxes are given for the lifetime of the satellite at selected integral energies from 10 to 100 MeV. Field strength calculations were performed with an extrapolated model on the basis of linear secular variation predictions. Orbital flux integration results are presented in graphical and tabular form.

Stassinopoulos, E. G.↗
NASA NTRS1972

A Wind Tunnel Flight Correlation of Apollo 15 Sonic Boom

A correlation of sonic boom pressure signatures recorded during reentry of the Apollo 15 command module with wind-tunnel signatures extrapolated to flight distances has been made for Mach numbers of 1.16 and 4.57. The flight pressure signatures were recorded by pressure sensors located onboard ships positioned near the ground track while the wind-tunnel signatures were measured during tests of a 0.016-scale model of the command module. The agreement between estimates based on wind-tunnel data and flight measurements was better at Mach 4.57 than at Mach 1.16.

Hicks, R. M.↗
NASA NTRS1972

A theoretical study of mixing downstream of transverse injection into a supersonic boundary layer

A theoretical and analytical study was made of mixing downstream of transverse hydrogen injection, from single and multiple orifices, into a Mach 4 air boundary layer over a flat plate. Numerical solutions to the governing three-dimensional, elliptic boundary layer equations were obtained using a general purpose computer program. Founded upon a finite element solution algorithm. A prototype three-dimensional turbulent transport model was developed using mixing length theory in the wall region and the mass defect concept in the outer region. Excellent agreement between the computed flow field and experimental data for a jet/freestream dynamic pressure ratio of unity was obtained in the centerplane region of the single-jet configuration. Poorer agreement off centerplane suggests an inadequacy of the extrapolated two-dimensional turbulence model. Considerable improvement in off-centerplane computational agreement occured for a multi-jet configuration, using the same turbulent transport model.

Baker, A. J.↗
NASA NTRS1972

Directional solidification of eutectic composites in space environment

The Ni-Ni3Ta eutectic and a nickel-base alloy containing 30 wt pct Ta were solidified unidirectionally in an electron beam floating zone melting apparatus. It was found that the volume fraction of the Ni3Ta phase in the Ni-Ni3Ta eutectic mixture was increased from 7.6 to 36 volume pct in agreement with the theory as predicted. Tensile properties of the randomly solidified and unidirectionally solidified Ni-Ni3Ta eutectic were determined as function of solidification rate and temperature. It was found that the ultimate tensile strength decreased as both the test temperature and solidification rate increased. An elongation of 40 pct was obtained for a nickelbase alloy containing 30 wt at room temperature. This unusually large elongation was attributed to the superplastic behavior of the alloy. The critical currents versus the external fields at 2.5, 3.0, 3.5 and 4.2 deg for the unidirectionally solidified Pb-Sn eutectic were measured. The values of critical fields at zero critical currents were obtained by extrapolation.

Yue, A. S.↗
NASA NTRS1973

Approximate thermochemical tables for some C-H and C-H-O species

Approximate thermochemical tables are presented for some C-H and C-H-O species and for some ionized species, supplementing the JANAF Thermochemical Tables for application to finite-chemical-kinetics calculations. The approximate tables were prepared by interpolation and extrapolation of limited available data, especially by interpolations over chemical families of species. Original estimations have been smoothed by use of a modification for the CDC-6600 computer of the Lewis Research Center PACl Program which was originally prepared for the IBM-7094 computer Summary graphs for various families show reasonably consistent curvefit values, anchored by properties of existing species in the JANAF tables.

Bahn, G. S.↗
NASA NTRS1973

A wind tunnel flight correlation of Apollo 16 sonic boom

A correlation of sonic boom pressure signatures recorded during reentry of the Apollo 16 command module with wind-tunnel signatures extrapolated to flight distances was made for Mach numbers of 1.83 and 9.71. The flight pressure signatures were recorded by microphones located onboard ships positioned near the ground track, whereas the wind tunnel signatures were measured during a test of a 0.016-scale model of the command module. The agreement between estimates based on wind tunnel data and flight measurements was good at the tested Mach numbers.

Garcia, F., Jr.↗