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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 1,423 records · Page 79

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NASA NTRS1987

Reduction of Orifice-Induced Pressure Errors

Use of porous-plug orifice reduces or eliminates errors, induced by orifice itself, in measuring static pressure on airfoil surface in wind-tunnel experiments. Piece of sintered metal press-fitted into static-pressure orifice so it matches surface contour of model. Porous material reduces orifice-induced pressure error associated with conventional orifice of same or smaller diameter. Also reduces or eliminates additional errors in pressure measurement caused by orifice imperfections. Provides more accurate measurements in regions with very thin boundary layers.

Plentovich, Elizabeth B.↗

NASA NTRS1987

Measuring Gases With Laser-Induced Fluorescence

Temperature, density, and pressure at selected point in low-temperature, turbulent gaseous flow measured simultaneously by pulsed laser-induced fluorescence (LIF). Measurements made with spatial and temporal resolution. LIF measurements nonintrusive and constitute first alternative means of measuring turbulent fluctuations in temperature and density that compares with conventional hot-wire-anemometer data. Laser beams focused to small spots in wind tunnel and reference cell induce fluorescence in nitric oxide, small amount s mixed with main gas flow. Fluorescence radiation depends on main-gas temperature, pressure, and density and measured to deduce these quantities.

Mckenzie, Robert L.↗

NASA NTRS1987

Radiation from large space structures in low earth orbit with induced ac currents

Large conducting space structures in low earth orbit will have a nonnegligible motionally induced potential across their structures. The induced current flow through the body and the ionosphere causes the radiation of Alfven and lower hybrid waves. This current flow is taken to be ac and the radiated power is studied as a function of the ac frequency. The current may be ac due either to inductive coupling from the power system on the structure or by active modulation. A Space Station-like structure and tether are studied. For the Space Station structure the radiation impedance is particularly high for frequencies in the tens of kilohertz range which suggests that the Space Station may be efficient source of lower hybrid waves. The tether is also shown to be a generator of VLF waves up to source ac frequencies in the megahertz range. The implications for these two structures are discussed.

Hastings, D. E.↗

NASA NTRS1986

Shock-induced volatile loss from a carbonaceous chondrite Implications for planetary accretion

Solid recovery impact-induced volatile loss experiments on the Murchison C2M meteorite indicate that for an impact of a given velocity, H2O and total volatiles are driven from the sample in the same proportion as present initially. The primitive surface volatile budget of a planet growing by accretion would have the same bulk elemental composition as the volatiles in the incident planetesimals. Incipient devolatilization of Murchison occurs at an initial shock pressure of about 11 GPa and complete devolatilization occurs at a pressure of about 30 GPa. For the earth, incipient and complete devolatilization of accreting planetesimals would occur when the planet reached approximately 12 percent and 27 percent, respectively, of its present-day radius. Impact-induced devolatilization would profoundly affect the volatile distribution within the accreting planet. Prior to metallic core formation and internal differentiation the growing planet would have a very small core with the same volatile content as the incident material, a volatile depleted mantle, and an extremely volatile rich surface. In the case of the earth, 99.4 wt pct of the total incident volatile material would end up on or near the planetary surface.

Tyburczy, James A.↗

NASA NTRS1987

Solar ultraviolet radiation induced variations in the stratosphere and mesosphere

The detectability and interpretation of short-term solar UV induced responses of middle atmospheric ozone, temperature, and dynamics are reviewed. The detectability of solar UV induced perturbations in the middle atmosphere is studied in terms of seasonal and endogenic dynamical variations. The interpretation of low-latitude ozone and possible temperature responses on the solar rotation time scale is examined. The use of these data to constrain or test photochemical model predictions is discussed.

Hood, L. L.↗

NASA NTRS1987

Ram ion scattering caused by Space Shuttle v x B induced differential charging

Observations of secondary, high-inclination ions streams have been reported in the literature. The authors of these previous papers attributed the source of the secondary ions to a disturbed region in the plasma about 10 m from the Space Shuttle Orbiter. A new theory has been developed which shows how v x B induced differential charging on the plasma diagnostics package (PDP) can scatter the ram ion flux. Some of these ions are reflected back to the PDP and may be the sorce of the observed ion distributions. The effect is unique to large spacecraft; it occurs only when the magnitude of the induced v x B potentials are much larger than the electron thermal energy and of the order of the ion ram energy. That the ion streams observed at large angles must have been reflected from the PDP surface is demonstrated with three-dimensional sheath and particle trajectory calculations using the low earth orbit version of the NASA Charging Analyzer Program (NASCAP/LEO).

Katz, I.↗

NASA NTRS1987

Propulsion-induced effects caused by out-of-ground effects

Propulsion induced effects encountered by moderate- to high-disk loading STOVL or VSTOL aircraft out-of-ground effect during hover and transition between hover and wing-borne flight are discussed. Descriptions of the fluid flow phenomena are presented along with an indication of the trends obtained from experimental investigations. In particular, three problem areas are reviewed: (1) the performance losses sustained by a VSTOL aircraft hovering out-of-ground effect, (2) the induced aerodynamic effects encountered as a VSTOL aircraft flies on the combination of powered and aerodynamic lifts between hover and cruise out-of-ground effect, and (3) the aerodynamic characteristics caused by deflected thrust during maneuvering flight over a wide range of both angle of attack and Mach number.

Margason, Richard↗

NASA NTRS1987

Measurements of temperature, density, pressure, and their fluctuations in supersonic turbulence using laser-induced fluorescence

A laser-induced fluorescence method has been developed that provides simultaneous measurements of temperature, density, and their fluctuations owing to turbulence in unheated compressible flows. Pressure and its fluctuations are also deduced using the equation of state. Fluorescence is induced in nitric oxide that has been seeded into a nitrogen flow in concentrations of 100 ppm. Measurements are obtained from each laser pulse, with a spatial resolution of 1 mm and a temporal resolution of 125 ns. The method was applied to a supersonic, turbulent, boundary-layer flow with a free-stream Mach number of 2. For stream conditions in the range from 150-300 K and 0.3-1 atm, temperature is measured with an uncertainty of approximately 1 percent rms, while density and pressure uncertainties are approximately 2 percent rms.

Gross, K. P.↗

NASA NTRS1987

Thermally induced phase changes, lateral heterogeneity of the mantle, continental roots, and deep slab anomalies

Factors which influence the lateral heterogeneity in density and seismic velocity with depth in the upper earth mantle are discussed. It is emphasized that most of the increases in density and seismic velocity with depth are caused by pressure-induced solid-solid phase changes in the high-density high-velocity phases of mineral assemblage, due to variations in temperature. In particular, the ilmenite form of MgSiO3 and the gamma-spinel form of Mg2SiO4 have broad stability fields in cold mantle and are not stable in hotter mantle. It is emphasized that the density and velocity anomalies associated with temperature-induced phase changes in mineral assemblage must be taken into account in the thermal models of the slabs; when these effects are accounted for, the geoid and seismic anomalies associated with subducted slabs are consistent with slab confinement to the upper mantle and with layered models of mantle convection.

Anderson, Don L.↗

NASA NTRS1987

Changes in the earth's rotation and low-degree gravitational field induced by earthquakes

Analytical formulas based on the normal-mode theory are used together with a spherically symmetric earth model and the centroid-moment tensor solutions for earthquake sources to compute the earthquake-induced changes in the earth's rotation and low-degree harmonics of the gravitational field for the period 1977-1985. Spectral and statistical analyses are conducted on these changes. It is found that the earthquake-induced changes are two orders of magnitude smaller than those observed; most of these changes show strong evidence of nonrandomness either in their polarity or in their directions.

Chao, B. Fong↗

NASA NTRS1988

Propulsion-induced effects caused by out-of-ground effects

Margason, Richard↗

NASA NTRS1988

Air-broadened Lorentz halfwidths and pressure-induced line shifts in the nu(4) band of C-13H4

Air-broadened halfwidths and pressure-induced line shifts in the nu(4) fundamental of C-13H4 were determined from spectra recorded at room temperature and at 0.01/cm resolution using a Fourier transform spectrometer. Halfwidths and pressure shifts were determined for over 180 transitions belonging to J-double prime values of less than or = to 16. Comparisons of air-broadened halfwidths and pressure-induced line shifts made for identical transitions in the nu(4) bands of C-12H4 and C-13H4 have shown that C-13H4 air-broadened halfwidths are about 5 percent smaller than the corresponding C-12H4 halfwidths, and the pressure shifts for C-13H4 lines are about 5-15 percent larger than those for C-12H4.

Devi, V. Malathy↗

NASA NTRS1988

X-ray induced stellar mass loss near active galactic nuclei

The effects of UV and X-ray radiation on stars in active galactic nuclei (AGN) are critically evaluated. Mass loss rates in X-ray-induced winds are evaluated for realistic red giant models, and the effects of the ablation of stellar envelopes by radiation pressure are considered. The importance of X-ray-induced mass loss in the standard quasar model is evaluated and whether it can provide a source of accretion fuel or emission-line clouds is discussed. It is concluded that thermal winds driven by X-ray heating are a minor total supply of mass to AGN, but that thermal plus line-driven winds and stellar ablation may increase the mass loss and improve the chances for supplying a fraction of the necessary mass supply to the central object. It is speculated that when steady winds are inefficient, complex time-dependent processes due to X-ray energy injection deep into a stellar atmosphere could still release significant mass from stars.

Voit, G. Mark↗

NASA NTRS1988

Control of the induced microgravity environment of the Man Tended Free Flyer (MTFF)

Induced disturbance sources have been identified on board the Man Tended Free Flyer (MTFF). Vibration responses at sensitive payload/spacecraft interfaces have been predicted by the application of an empirically found spacecraft dynamic transfer function. Vibrations from fluid loops (Freon, water) and of reaction wheels are assessed to be the main contributors to the induced microgravity environment. The expected payload acceleration response amplitudes presented here are more than one hundred times higher than the admissible values given by the MTFF system requirement, not considering the structural striction-friction effects which could be avoided by appropriate design. Real responses will be significantly lower because the derivation of excitation and transmission functions are based on worst case assumptions. The results indicate that future activities must be concentrated on equipment design improvement and the implementation of vibration reduction along the disturbance transmission path. The activities must be accompanied by early equipment and assembly development tests and transmissibility measurements with the integrated spacecraft engineering and structural models in order to improve the accuracy of payload response predictions.

Schlund, Juergen↗

NASA NTRS1989

Numerical studies of the effects of jet-induced mixing on liquid-vapor interface condensation

Numerical solutions of jet-induced mixing in a partially full cryogenic tank are presented. An axisymmetric laminar jet is discharged from the central part of the tank bottom toward the liquid-vapor interface. Liquid is withdrawn at the same volume flow rate from the outer part of the tank. The jet is at a temperature lower than the interface, which is maintained at a certain saturation temperature. The interface is assumed to be flat and shear-free and the condensation-induced velocity is assumed to be negligibly small compared with radial interface velocity. Finite-difference method is used to solve the nondimensional form of steady state continuity, momentum, and energy equations. Calculations are conducted for jet Reynolds numbers ranging from 150 to 600 and Prandtl numbers ranging from 0.85 to 2.65. The effects of above stated parameters on the condensation Nusselt and Stanton numbers which characterize the steady-state interface condensation process are investigated. Detailed analysis to gain a better understanding of the fundamentals of fluid mixing and interface condensation is performed.

Lin, Chin-Shun↗

NASA NTRS1988

The induced environment around Space Station

The potential impact of the International Space Station on its immediate environment is discussed, summarizing the results of recent investigations by NASA working groups. Consideration is given to the neutral-gas environment, induced photon emission, particulate contamination, the ionized environment, the Induced-environment Monitoring Package proposed for inclusion in the Space Station equipment, and recommendations for further research. Diagrams, drawings, graphs, and tables of numerical data are provided.

Torr, Marsha R.↗

NASA NTRS1988

Elimination of pressure-induced fluorescence in diamond anvils

At pressures above one megabar (100 GPa) in high-pressure diamond anvil cell experiments, the ruby fluorescence signal needed for pressure calibration is increasingly difficult to measure. A primary cause of this difficulty is the presence of an intense pressure-induced diamond fluorescence. A tentative identification of this pressure-induced fluorescence is given, a technique for the elimination of this fluorescence is reported. It is demonstrated that weak ruby signals, completely hidden by diamond fluorescence, are now easily measured with this technique.

Eggert, Jon H.↗

NASA NTRS1989

Shock-wave-induced mixing enhancement in scramjet combustors

An experimental study of the interaction between a weak shock wave and a supersonic shear layer was carried out to determine the possibility of shock-induced mixing enhancement. A supersonic (Mach 2.5) stream of nitrogen was mixed with a sonic helium jet downstream of a rearward-facing step to simulate the mixing region in the vicinity of a SCRAMJET flameholder. A small wedge was used to generate an oblique shock wave that impinges on the mixing layer. Schlieren flow visualization and Rayleigh scattering concentration measurements were carried out. The results indicate that significant spreading of the shear layer may occur downstream of the shock/shear layer interaction region. Further study is required to determine the mechanism of the observed spreading and the extent of the increase in mixing efficiency. Since there are shock-induced losses, an optimum mixing enhancement configuration will have to be determined before the method can be validated and successfully implemented in a SCRAMJET combustor.

Menon, S.↗