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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Relativistic Radiative and Auger Rates for Fe XXIV

As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of radiative and Auger rates for transitions involving the K-vacancy states in Fe XXIV. By making use of several computational codes, a detailed study is carried out of orbital representation, configuration interaction, relativistic corrections, cancellation effects, and fine tuning. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%.

Bautista, M. A.↗
NASA NTRS1995

The Efficiency of "Viscous Interaction" Between the Solar Wind and the Magnetosphere During Intense Northward IMF Events

We examined 11 cases when the interplanetary magnetic field (IMF) was intensely northward (>10 nT) for long durations of time (>3 hours), to quantitatively determine an upper limit on the efficiency of solar wind energy injection into the magnetosphere. We have specifically selected these large BN events to minimize the effects of magnetic reconnection. Many of these cases occurred during intervals of high- speed streams associated with coronal mass ejections when viscous interaction effects might be at a maximum. It is found that the typical efficiency of solar wind energy injection into the magnetosphere is 1.2 x 10-3 to 4.0 x 10-3, 100 to 300 times less efficient than during periods of intense southward IMFs. Other energy sinks not included in these numbers are discussed. Estimates of their magnitudes are provided.

Viscous↗
NASA NTRS1987

Mach number effects on conical surface features of swept shock boundary-layer interactions

A joint experimental and computational study is made of the shock-wave turbulent boundary-layer interaction generated by sharp fins, with emphasis on Mach-number effects. The Mach number range is from 2 to 4 and the unit Reynolds number is from 50 to 80 million per meter. Fin angles are varied from 4 to 22 deg. Surface-flow patterns are obtained using a color surface-flow-visualization technique. The results show that the upstream-influence response in the conical far-field region is a function of the freestream Mach number and the shock strength. A new interpretation of the behavior of the upstream influence with changes of the inviscid shock angle is given. Agreement between the experimental and the computed upstream-influence lines becomes poorer for stronger interactions, with the computations underpredicting the upstream-influence line.

Lu, F. K.↗
NASA NTRS2005

Effects of Cutoffs on Galactic Cosmic-Ray Interactions in Solar-System Matter

The energetic particles in the galactic cosmic rays (GCR) induce many interactions in a variety of solar-system matter. Cosmogenic nuclides are used to study the histories of meteorites and lunar samples. Gamma rays and neutrons are used to map the compositions of planetary surfaces, such as Mars, the Moon, and asteroids. In almost all of these cases, the spectra of incident GCR particles are fairly similar, with only some modulation by the Sun over an 11-year cycle. Strong magnetic fields can seriously affect the energy spectrum of GCR particles hitting the surface of objects inside the magnetic fields. The Earth s geomagnetic field is strong enough that only GCR particles with magnetic rigidities above approx. 17 GV (a proton energy of approx. 17 GeV) reach the atmosphere over certain regions near the equator. This effect of removing lower-energy GCR particles is called a cutoff. The jovian magnetic fields are so strong that the fluxes of GCR particles hitting the 4 large Galilean satellites are similarly affected. The cutoff at Europa is estimated to be similar to or a little higher than at the Earth s equator.

Kim, K. J.↗
NASA NTRS2002

Atomic Data for the K-Vacancy States of Fe XXIV

As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

Bautista, M. A.↗
NASA NTRS2003

Atomic Data for the K-vacancy States of Fe XXIV

As part of a project to compute improved atomic data for the spectral modeling of iron K lines, we report extensive calculations and comparisons of atomic data for K-vacancy states in Fe XXIV. The data sets include: (i) energy levels, line wavelengths, radiative and Auger rates; (ii) inner-shell electron impact excitation rates and (iii) fine structure inner-shell photoionization cross sections. The calculations of energy levels and radiative and Auger rates have involved a detailed study of orbital representations, core relaxation, configuration interaction, relativistic corrections, cancellation effects and semi-empirical corrections. It is shown that a formal treatment of the Breit interaction is essential to render the important magnetic correlations that take part in the decay pathways of this ion. As a result, the accuracy of the present A-values is firmly ranked at better than 10% while that of the Auger rates at only 15%. The calculations of collisional excitation and photoionization cross sections take into account the effects of radiation and spectator Auger dampings. In the former, these effects cause significant attenuation of resonances leading to a good agreement with a simpler method where resonances are excluded. In the latter, resonances converging to the K threshold display symmetric profiles of constant width that causes edge smearing.

Bautista, M. A.↗
NASA NTRS2002

Overview of the ANITA project

The ANITA project is designed to investigate ultra-high energy (>10^17 eV) cosmic ray interactions throughout the universe by detecting the neutrinos created in those interactions. These high energy neutrinos are detectable through their interactions within the Antarctic ice sheet, which ANITA will use as a detector target that effectively converts the neutrino interactions to radio pulses. This paper will give an overview of the project including scientific objectives, detection description and mission design.

ANITA↗
NASA NTRS1984

Report on final recommendations for IMPS engineering-science payload

Six general categories of key scientific and engineering concerns for the interactions measurements payload for shuttle (IMPS) mission are addressed: (1) dielectric charging; (2) material property changes; (3) electromagnetic interference, plasma interactions, and plasma wake effects associated with high-voltage solar arrays and large space structures; (4) radio frequency distortion and nonlinearities due to the enhanced plasma in the shuttle ram/wake; (5) shuttle glow and contamination; and (6) plasma interactions with the space-based radar. Lesser concerns are the interactions associated with EVA; the radiation and SEU effects peculiar to the auroral/polar cap environments; and space debris. The measurements needed to address the concerns associated with the general categories are described and a list of generic investigations capable of making the required measurements, emphasizing the spectrum of measurements necessary to quantize the interactions in the auroral/polar environments are included. A suggested ground-test plan for the IMPS project, a description of proposed follow-on IMPS missions, and a detailed bibliography for each of the interactions discussed are included.

Garrett, H. B.↗
NASA NTRS2026

Experimental Study of Aeropropulsive Interactions for Electric Ducted Fans on a Wing

The Adaptable Distributed Electric Propulsion Testbed (ADEPT)Wing was tested in the NASA Langley 12-Foot Low-Speed Tunnel to investigate electric propulsion technologies for commercial transport aircraft. The purpose of the test was to study the aeropropulsive effects across angle of attack and fan speed variations for several propulsor placements and array sizes, and to investigate how distributed electric propulsion (DEP) can be leveraged for augmented lift and vehicle control. Six electric ducted fan (EDF) array placements were tested by positioning the fans along the leading and trailing edges on the top and bottom surfaces, as well as centered on the chord line in front of and behind the wing. Each fan placement configuration was tested with an array of one, three, and five EDFs to characterize an aeropropulsive extrapolation effect, and the bare wing was tested separately to provide baseline aerodynamic measurements. The results compare the longitudinal forces and moments for each configuration by analyzing the combined aeropropulsive interaction effects, and offer valuable insight into considerations for fan placement along a wing to enable the benefits of DEP integration.

Rose Weinstein↗
NASA NTRS1995

The efficiency of 'viscous interaction' between the solar wind and the magnetosphere during intense northward IMF events

We examined 11 cases when the interplanetary magnetic field (IMF) was intensely northward (greater than 10 nT) for long durations of time (greater than 3 hours), to quantitatively determine an uppler limit on the efficiency of solar wind energy injection into the magnetosphere. We have specifically selected these large B(sub N) events to minimize the effects of magnetic reconnection. Many of these cases occurred during intervals of high-speed streams associated with coronal mass ejections when viscous interaction effects might be at a maximum. It is found that the typical efficiency of solar wind energy injection into the magnetosphere is 1.0 x 10(exp -3) to 4.0 x 10(exp -3), 100 to 30 times less efficient than during periods of intense southward IMFs. Other energy sinks not included in these numbers are discussed. Estimates of their magnitudes are provided.

Tsurutani, Bruce T.↗
NASA NTRS2020

The Role of the SO2 Radiative Effect in Sustaining the Volcanic Winter and Soothing the Toba Impact on Climate

Volcanic eruptions are an important climate driver. The impact of Pinatubo-sized eruptions has been observed and is well constrained. The magnitude and duration of volcanic winter effects after super-eruptions such as Toba remain disputed due to disagreement between the strong cooling predicted by models, and much milder climate perturbations according to the paleo data. Here we present a re-evaluated climate impact of a Toba-sized super-eruption based on up-to-date GISS ModelE simulations. In this study, we account for all known primary mechanisms that govern the evolution of the volcanic plume and their nonlinear interactions. The SO2 radiative effects are evaluated for the first time in coupled climate simulations with the interactive atmospheric chemistry module. We found that SO2 effects on photochemistry, dynamics, and radiative forcing are especially prominent. Due to strong absorption in ultraviolet, SO2 feedback on photochemistry partially offsets the limiting effect associated with aerosol microphysical processes. SO2 greenhouse warming soothes the radiative cooling exerted by sulfate aerosols. SO2 absorption in the shortwave and longwave causes radiative heating and lofting of the volcanic plume, and boosts the efficiency of SO2 impact on photochemistry. Our analysis shows that SO2 lifetime and magnitude of effects scale up and increase with the amount of emitted material. For a Pinatubo-sized eruption, SO2 feedbacks on chemistry and dynamics are relevant only during the initial stage of the volcanic plume evolution, while local SO2 concentrations are high. For a Toba-sized eruption, SO2 effects are as important as sulfate aerosols, and produce a less extreme volcanic winter.

Sergey Osipov↗
NASA NTRS1986

A review of aerothermal problems associated with hypersonic flight

A review is presented of some important aerothermal problems associated with hypersonic flight with emphasis on those involved with viscous/inviscid interaction. The flow regimes of importance to hypersonic vehicles of current interest are discussed and the performance of experimental facilities currently available to study real gas phenomena associated with hypervelocity flight are briefly reviewed. Viscous interaction and real gas effects in hypervelocity flight at high altitudes are discussed with reference to measurements which are required to support the development of improved prediction capabilities in this regime. Theoretical and experimental research on 2D and 3D shock wave/laminar boundary layer interaction relevant to the performance of control surfaces and inlets in hypersonic flight at high altitudes is reviewed. The characteristics of transition regions in hypersonic flows are discussed with particular reference to transitional flows over nosetips and swept leading edges. Studies of shock interaction phenomena on indented nosetips are discussed, followed by a review of the surface roughness and blowing effects. Research to describe the characteristics of 2D and 3D regions of shock wave/turbulent boundary layer interaction in hypersonic flow is reviewed with particular reference to intrinsic unsteadiness and potential compressibility effects in these flows. This review is concluded with a brief discussion of observations suggesting a decrease in the spreading rate in shear layer mixing in hypersonic flow.

Holden, M. S.↗
NASA NTRS1994

Effects of leading and trailing edge flaps on the aerodynamics of airfoil/vortex interactions

A numerical procedure has been developed for predicting the two-dimensional parallel interaction between a free convecting vortex and a NACA 0012 airfoil having leading and trailing edge integral-type flaps. Special emphasis is placed on the unsteady flap motion effects which result in alleviating the interaction at subcritical and supercritical onset flows. The numerical procedure described here is based on the implicit finite-difference solutions to the unsteady two-dimensional full potential equation. Vortex-induced effects are computed using the Biot-Savart Law with allowance for a finite core radius. The vortex-induced velocities at the surface of the airfoil are incorporated into the potential flow model via the use of the velocity transpiration approach. Flap motion effects are also modeled using the transpiration approach. For subcritical interactions, our results indicate that trailing edge flaps can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, our results demonstrate the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time-dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented

Hassan, Ahmed A.↗
NASA NTRS1989

Biophysical aspects of heavy ion interactions in matter

The biological effects of high energy, high charge nuclei (HZE particles) occupy a central role in the management of space radiation hazards due to galactic cosmic rays. For the energy range of interest, the mean free path for nuclear interactions of these heavy ions is comparable to the thickness of the material traversed, and a significant fraction of stopping particles will undergo a nuclear reaction with the nuclei of the stopping material. Transport methods for HZE particles are dependent on models of the interaction of man-made systems with the space environment to an even greater extent than methods used for other types of radiation. Hence, there is a major need to validate these transport codes by comparison with experimental data. The basic physical properties of HZE particles will be reviewed and illustrated with the results of nuclear fragmentation experiments performed with 670A MeV neon ions incident on a water absorber and with measurements of multiple Coulomb scattering of uranium beams in copper. Finally, the extent to which physical measurements yield radiobiological predictions is illustrated for the example of neon.

Schimmerling, Walter↗
NASA NTRS1961

Semi-Annual Report: October 15, 1961

Investigations are proposed involving an experimental and theoretical program designed to investigate various properties of the structure of helium both in its atomic form and in the aggregates of the liquid and solid states. The key to the possibilities of performing the experiments lies in the relatively weak electric fields existing in liquid and solid helium and the possibility of producing external fields almost comparable with the internal fields. It is proposed to examine a) the melting pressure curve for helium as a function of electric field b) the dielectric constant of helium as a function of pressure and electric field c) in future, the effect of electric fields on the lambda transition. From the results of these experiments one would expect to be able to gather at least corroborative evidence on a) the crystal structure of solid helium on b) the effect of the Van der Waal interaction of the electric polarizability of helium, c) the possibility of producing helium molecules d) the effective volume available to helium atoms in the liquid and possibly e) the effect of particle interactions on the Bose-Einstein condensation.

HELIUM↗