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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Experimental results for the transpired turbulent boundary layer in an adverse pressure gradient

The fluid mechanics of transpired incompressible turbulent boundary layers under zero and adverse pressure gradient conditions is investigated using an open-ended wind tunnel with a porous floor in the test section and a secondary air system for supply and metering of the transpiration air. All velocity profiles and turbulence profiles are obtained by linearized constant-temperature hot-wire anemometry. The wall shear stress is determined by measuring the shear stress away from the wall and extrapolating to the wall by integrating the boundary layer equations for the shear-stress profile. Equilibrium boundary layers are obtained when the transpiration velocity is varied such that the blowing parameter and the Clauser pressure gradient parameter are held constant. The experimental results obtained are presented in tabular and graphical forms.

Andersen, P. S.↗
NASA NTRS1975

Heavy solar cosmic rays in the January 25, 1971 solar flare

A detailed study of the charge composition of heavy solar cosmic rays measured in the January 25, 1971 solar flare including differential fluxes for the even-charged nuclei from carbon through argon is presented. The measurements are obtained for varying energy intervals for each nuclear species in the energy range from 10 to 35 MeV per nucleon. In addition, abundances relative to oxygen are computed for all the above nuclei in the single energy interval from 15 to 25 MeV per nucleon. This interval contains measurements for all of the species and as a result requires no spectral extrapolations. An upper limit for the abundance of calcium nuclei is also presented. These measurements, when combined with other experimental results, enable the energy dependence of abundance measurements as a function of nuclear charge to be discussed. It is seen that at energies above about 10 MeV per nucleon, the variations of abundance ratios are limited to about a factor of 3 from flare to flare, in spite of large variations in other characteristics of these solar events.

Pellerin, C. J., Jr.↗
NASA NTRS1975

Glauber exchange amplitudes

The extrapolation method of Ochkur, valid for intermediate energies (about 50 eV), is applied to the exchange form of the Glauber amplitudes. In the case of elastic scattering of electrons from hydrogen atoms at 54.4 Ev the 'post' and 'prior' forms of the exchange amplitude are equivalent, whereas for the case of inelastic scattering there is a minute discrepancy between the two forms of the amplitude. The results are compared with the close-coupling calculation. The investigation is expected to be useful for optically forbidden exchange-allowed transitions due to electron impact at intermediate energies.

Madan, R. N.↗
NASA NTRS1975

Crab Nebula observations - 0.2-10 MeV

Observations of the total emission from the Crab Nebula and also of the pulsed component were made over the 0.2 to 10-MeV range during three balloon flights in 1971 with an actively-collimated NaI scintillator. The total emission flux was positively observed over the entire interval. The observed spectrum to 1 MeV agrees with an extrapolation of the E to the -2.2 power law, which fits lower-energy data. The observations above 1 MeV are factors of 3 and 20 above this law and are better fit with a spectral index of 0.8. Confidence levels are 3 sigma or better for each half-decade band. The three observations are consistent with a constant flux level. The NP 0532 flux, detected during one flight only (August 8) between 0.2 and 0.38 MeV, agrees with the exponential power law spectrum already determined from other observations. The possibility of a rapidly rising pulsed emission fraction over the 0.1- to 1-MeV interval is excluded by this observation.

Gruber, D. E.↗
NASA NTRS1975

On a numerical sufficiency test for monotonic convergence of finite element models

Finite element analyses characterized by monotonic convergence include the discipline for meaningful measurements of convergence rate and consequently economical extrapolation. Few proposers of element models guarantee monotonic convergence for their elements. Thus, a need exists for an automatic test to classify available element models. This paper describes such a test - a test can be performed using a digital computer to guarantee that a particular element model imbues monotonicity. It describes the test and its basis. It examines seven element models for a rectangular membrane to illustrate the value of the tests. Besides confirming results already known, the application yields new data. It 'proves' monotonicity for two improved models, defines the range of element proportions for which another element can be guaranteed to exhibit monotonicity, and suggests that another element is deficient. In the special case of absolutely convergent membrane displacement models, proof of monotonicity is a necessary and sufficient condition to insure that upper bound estimates of strain energy are developed. Accordingly, the test furnishes a proof of bound solutions independently of requirements on displacement continuity the element basis may or may not satisfy.

Melosh, R. J.↗
NASA NTRS1975

Photometer calibration problem for extended astronomical sources

Analysis of calibration tests for the Skylab experimental T027 photometer is used to show that if an instrument is focused at infinity, the uniform extended calibration source should be positioned at distances at least equal to the hyperfocal distance and should be large enough to fill the field of view. It is noted that the field depth can be increased by focusing the optical system at the hyperfocal distance and that this method of focusing reduces the needed diameter of the calibration source to half that of a system focused at infinity. Other calibration methods discussed includes determining the radiance responsivity distance and extrapolating the curve to larger distances as well as extensive mapping of the spatial response combined with the irradiance responsivity to obtain the radiance responsivity.

Muscari, J. A.↗
NASA NTRS1974

The grain growth of iron - Implications for the thermal conditions in a lunar ejecta blanket

The times and temperatures for the growth of single-domain to multidomain iron have been determined in a synthetic glass of Apollo 11 composition. All single-domain iron grows to multidomain iron under the following conditions: at 975 C in about 5 hours; at 900 C in about 18 days; at 810 C in about 320 days; and at 700 C in about 1100 years (extrapolated). The results, together with thermal constraints on the metamorphism of lunar breccias, indicate cooling rates of breccias containing single domain iron are appropriate for formation in an ejecta blanket.

Usselman, T. M.↗
NASA NTRS1975

Status report on NASA two-segment approach program

NASA, in cooperation with the FAA, is evaluating the two-segment approach as a routine procedure for reducing aircraft noise. The program calls for separate flight evaluations using a 727 and a DC-8, and an extrapolation of these results to determine the adaptability of the technique to the rest of the fleet. After a review of the total program, this paper presents (1) the profile and procedures developed and the noise reduction achievable, (2) the vortex characteristics behind an aircraft on a two-segment path, and (3) cost estimates for retrofitting aircraft with two-segment avionics.

Denery, D. G.↗
NASA NTRS1975

Estimates of saltation threshold and erosion rates on Mars

The Mariner 9 photographs of the Martian surface include many which show crater-associated streaks caused by atmospheric winds. Due to the low density atmosphere of Mars, the wind speeds necessary to move surface particles and thus cause the streaks are apparently very high. The atmospheric-boundary-layer wind tunnel has been used to determine threshold speeds for particles of varying density and diameter and the results for small particles have been extrapolated to estimate somewhat lower threshold speeds on Mars than previous estimates. A series of streak modeling tests is used to derive an erosion-rate correlation function, which is in turn used to estimate erosion rates to the lee of some of the craters on Mars which exhibited time-dependent streak behavior during the mission.

Iversen, J. D.↗
NASA NTRS1975

Observations in interplanetary space of relativistic electrons from Jupiter

Evidence for the presence of Jovian electrons in interplanetary space as much as 1 AU inside the orbit of Jupiter is summarized. Electron flux patterns at Pioneer 10 can only rarely be correlated with solar activity. Clear variations in intensity and spectrum with a period of 10 hrs are seen at varying distances from Jupiter, consistent with similar observations inside the magnetosphere. Extrapolated electron flux maxima and minima are in good agreement with the observed phase at distances as large as 80 million km from Jupiter, indicating rapid propagation of electrons from the planet. Anisotropy is greatest during the rising phase of the 10 hr variations and in a direction consistent with the interpretation of electrons traveling toward the sun along interplanetary spiral field lines. The propagation time calculated by Chenette's derivation is much larger than that implied by the data.

Chenette, D. L.↗
NASA NTRS1975

Critical flow and pressure ratio data for LOX flowing through nozzles

LOX and LN2 data for two-phase critical flow through nozzles have been acquired with precision control. The principal measured parameters were inlet conditions, critical flow rate and critical flow pressure ratio. The data conclusively demonstrate that the principle of corresponding states can be applied to two-phase choked flow through nozzles. These data also demonstrate that the proper normalizing parameters have been developed and current theories can provide an adequate means for extrapolating to other fluids.

Hendricks, R. C.↗
NASA NTRS1975

Ultraviolet observations of classical Cepheids by OAO-2

OAO-2 observations of eight bright classical Cepheids in the wavelength region 1910 A to 4250 A are presented. The data for RT Aurigae, alpha Ursa Minoris, delta Cephei, and gamma Ophiuchi show excellent agreement with ground based photometry in the wavelength region of overlap and are consistent with a simple extrapolation of light curve properties from the visible region. However, in the ultraviolet, the light curve of beta Doradus shows two small flux bumps, at phases of 0.75 and 0.85, in addition to the well known bump at phase 0.0. All three bumps should probably be associated with the arrival of shocks at the stellar surface.

Hutchinson, J. L.↗
NASA NTRS1975

The high current transient generator, theory and operation for simulating lightning induced voltages into aerospace electrical circuits

Because of the difficulty, hazard, and cost of simulating full-scale lightning currents on flight vehicles, a nondestructive test technique using reduced-scale lightning currents was used to determine if threat level voltages will be induced into aircraft electrical circuits in the event the aircraft is actually struck by lightning. The reasoning and theory of selecting a particular simulated lightning waveshape and magnitude is given, showing that extrapolation of induced waveforms over several orders of magnitude should be avoided. The operation of high-current transient generators and hardware are described along with typical applications. The means by which voltages were generated, induced, and measured, as well as possible sources of error, are discussed.

Schulte, E. H.↗
NASA NTRS1975

Optical and infrared transfer function of the GEOS 3 retroreflector array

The transfer function of the retroreflector array carried by the Geos 3 satellite was computed at three wavelength: 5300, 6943, and 10600 A. The range correction is given for extrapolating laser range measurements to the center of gravity of the satellite. The reflectivity of the array was computed for estimating laser-echo signal strengths.

Arnold, D. A.↗
NASA NTRS1975

The isotopic composition of cosmic rays with 5 is less than or equal to z which is less than or equal to 26

Results obtained from a high altitude balloon flight from Thompson, Canada in August, 1973 are reported. The instrument consisted of a spark chamber, a Lucite Gerenkov counter and thirteen layers of scintillators. For heavy particles the Cerenkov-range method of analysis was used to determine the mass of particles energetic enough to produce a Cerenkov signal and then stop in the layered scintillators. The data appear to be consistent with current cosmic-ray propagation models. Using a simple exponential path length propagation model this data is extrapolated to the cosmic-ray source and some implications of the data are discussed as to the nature of the source.

Fisher, A. J.↗
NASA NTRS1976

Thermal conductance of and heat generation in tire-pavement interface and effect on aircraft braking

A finite-difference analysis was performed on temperature records obtained from a free rolling automotive tire and from pavement surface. A high thermal contact conductance between tire and asphalt was found on a statistical basis. Average slip due to squirming between tire and asphalt was about 1.5 mm. Consequent friction heat was estimated as 64 percent of total power absorbed by bias-ply, belted tire. Extrapolation of results to aircraft tire indicates potential braking improvement by even moderate increase of heat absorbing capacity of runway surface.

Miller, C. D.↗
NASA NTRS1975

Study of the commonality of space vehicle applications to future national needs (unclassified portion)

A midterm progress report was presented on the study of commonality of space vehicle applications to future national needs. Two of the four objectives in the entire study were discussed. The first one involved deriving functional requirements for space systems based on future needs and environments for the military and civilian communities. Possible space initiatives based on extrapolations of technology were compiled without regard as to need but only with respect to feasibility, given the advanced state of technology which could exist through the year 2,000. The second one involved matching the initiatives against the requirements, developing a methodology to match and select the initiatives with each of the separate plans based on the future environments, and deriving common features of the military and civilian support requirements for these programs.

Source record↗
NASA NTRS1975

Applications of adenine nucleotide measurements in oceanography

The methodology involved in nucleotide measurements is outlined, along with data to support the premise that ATP concentrations in microbial cells can be extrapolated to biomass parameters. ATP concentrations in microorganisms and nucleotide analyses are studied.

Holm-Hansen, O.↗