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Results for “secondary source”

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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

An elementary theory of eclipsing depths of the light curve and its application to Beta Lyrae

An elementary theory of the ratio of depths of secondary and primary eclipses of a light curve has been proposed for studying the nature of component stars. It has been applied to light curves of Beta Lyrae in the visual, blue, and far-ultraviolet regions with the purpose of investigating the energy sources for the luminosity of the disk surrounding the secondary component and determining the dominant radiative process in the disk. No trace of the spectrum of primary radiation has been found in the disk. Therefore, it is suggested that LTE is the main radiative process in the disk, which radiates at a temperature of approximately 12,000 K in the portion that undergoes eclipse. A small source corresponding to 14,500 K has also been tentatively detected and may represent a hot spot caused by hydrodynamic flow of matter from the primary component to the disk.

Huang, S.-S.↗
NASA NTRS2024

Hydrogen Isotopic Composition of Hydrous Minerals in Particles From Bennu

On September 24, 2023, NASA’s OSIRIS-REx mission delivered to Earth ~121 g of pristine carbonaceous regolith from asteroid Bennu. A first series of mineralogical observations and chemical/isotopic analyses of Bennu aggregate samples (fine to coarse particles up to a few mm) revealed that this material resembles the most chemically primitive chondrites and the samples returned by the JAXA’s Hayabusa2 mission from the carbonaceous asteroid Ryugu. Laboratory studies have confirmed the story gleaned from the spacecraft encounter that Bennu’s rock fragments underwent extensive aqueous alteration and are predominantly composed of hydrated minerals (serpentine, smectite) and other secondary minerals (e.g., magnetite, carbonates). The secondary phases were likely formed under the presence of liquid water on Bennu’s parent asteroid. The isotopic compositions of hydrous minerals and secondary phases can increase our understanding of the source and distribution of water and volatile elements in the protoplanetary disk [e.g., 5-8]. However, direct estimates of the hydrogen isotopic ratios (D/H) in hydrous minerals cannot be obtained easily in primitive rocks due to the difficulty in estimating the organic matter (OM) contribution to the whole H budget. In order to obtain hints on the initial constituents of Bennu’s parent asteroid and to test if Bennu's parent asteroid have formed beyond the snow line (hypothesis 4 of [9]), we measured the D/H and C/H ratios in chondritic matrices by secondary ion mass spectrometry (SIMS) and obtain information on the D/H ratio of water retained in the hydrated minerals. The method also gives clues on the hydrogen isotope variability among different Bennu rock fragments made available for measurement.

L Piani↗
NASA NTRS1987

Observations of young low-mass stars in dense cores

In this period the first maps were made during two flights of the Kuipper Airborne Observatory (KAO) in January 1986. One of these shows extended emission at 100 and 160 microns from the dense core B35 containing the IRAS point source 05417+0907. The 160 micron emission has approximately the same extent as the NH3 (1,1) line emission at 1.4 cm, indicating close correspondence between the warm dust and the dense gas. The 160 micron map shows a previously unknown secondary maximum about 90 arcsec north of the IRAS source.

Myers, Philip C.↗
NASA NTRS1973

Spectroscopic observations of the optical candidate for Cygnus X-1.

The spectroscopic binary BD+34 3815 (= HDE 226868) with a period of 5.6 days, which is the brightest object in the position box for the X-ray source Cyg X-1, is studied to determine whether it meets all the requirements for being a black hole. Evidence is presented that the mass of the secondary is larger than the upper limits for white dwarfs or neutron stars, but there is no conclusive evidence that the optical binary is an X-ray source, and that the secondary is a collapsed object.

Brucato, R.↗
NASA NTRS1980

Low cost cryostat

A cryostat for use in a low or a substantially gravity-free environment adapted to cool an experiment through the use of helium 2, or helium in its super fluid state is characterized by a number of interchangeable daughter dewars and helium supply or mother dewar. A low pressure venting system is provided for converting helium contained in the mother dewar to a superfluid state for use as a primary cryogen. Each daughter dewar is adapted to be removably mounted in mated relation on the mother dewar and is characterized by support for an experiment package, a source of helium to be employed as a secondary cryogen. A heat pipe is suspended from each daughter dewar and adapted to be extended into the mother dewar for facilitating cooling of the secondary cryogen. A transfer of heat from the package to the primary cryogen, via the secondary cryogen, is accommodated as a film flow of helium 2 progresses from the heat pipe to the experiment dewar.

Stephens, J. B.↗
NASA NTRS1980

Galactic and extragalactic high energy neutrinos

Estimates of fluxes from cosmic diffuse sources are made using the generic relationship between secondary gammas and neutrinos and using recent cosmic gamma-ray satellite observations. A quantitative estimate of the observability above the atmospheric background of 1-10 TeV neutrinos from the inner Galaxy for a DUMAND type detector is then given.

Stecker, F. W.↗
NASA NTRS1981

Hotspots, basalts, and the evolution of the mantle

It is noted that the trace element concentration patterns of continental and ocean island basalts and of mid-ocean ridge basalts are complementary. Estimates of the relative sizes of the source regions for these fundamentally different basalt types can be arrived at from the trace element enrichment-depletion patterns. Their combined volume occupies the greater part of the mantle above the 670 km discontinuity. It is pointed out that the source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt. The mid-ocean ridge basalts source evolved from an eclogite cumulate that gave up its late-stage enriched fluids at various times to the shallower mantle and continental crust. The mid-ocean ridge basalts source is rich in garnet and clinopyroxene, while the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment. These relationships are found to be consistent with the evolution of a terrestrial magma ocean.

Anderson, D. L.↗
NASA NTRS1985

The isotopic composition of cosmic ray calcium

Data from the high energy cosmic ray experiment on the international sun earth explorer 3 (ISEE-3) spacecraft have been used to study the isotopic composition of cosmic ray calcium at an energy of approx. 260 MeV/amu. The arriving calcium is found to consist of (32 + or - 6)%. A propagation model consistent with both the light and the subiron secondary element abundances was used for the interpretation of the observed calcium composition. The measured 42Ca+43Ca+44Ca abundance is consistent with the calculated secondary production, while the 40Ca abundance implies a source ratio of 40Ca/Fe = (7.0 + or - 1.7)%.

Krombel, K. E.↗
NASA NTRS1986

Discovery of a new short-period, eclipsing cataclysmic variable

Photometry and spectroscopy of a newly recognized 14th mag eclipsing cataclysmic variable, KPD 1911 + 1212 (= SVS 8130, V1315 Agl) are reported. The system exhibits deep (1.7 mag) eclipses with period 0.1397 day. The spectrum is that of a high-excitation old nova and shows dramatic variability of the emission line strengths through the eclipse. The profiles of the Balmer emission lines are also phase-dependent, with prominent absorption cores appearing briefly near the inferior conjunction of the emission line source. There is no direct evidence for the secondary. A preliminary determination of radial velocity variations at modest spectral resolution yields K = 132 + or - 26 km/s for the Balmer emission lines. A model is presented for the system consistent with current data, which implies a mass for the primary and secondary stars of 0.9 and 0.4 solar mass respectively and in inclination of i = 78 deg.

Downes, R. A.↗
NASA NTRS1986

A review of impulsive phase phenomena

A brief review is given of impulsive phase phenomena in support of the models used to compute the energies of the different components of the flares under study. The observational characteristics of the impulsive phase are discussed as well as the evidence for multi-thermal or non-thermal phenomena. The significance of time delays between hard X-rays and microwaves is discussed in terms of electron beams and Alfven waves, two-step acceleration, and secondary bursts at large distances from the primary source. Observations indicating the occurrence of chromospheric evaporation, coronal explosions, and thermal conduction fronts are reviewed briefly, followed by the gamma ray and neutron results. Finally, a preferred flare scenario and energy source are presented involving the interactions in a complex of magnetic loops with the consequent reconnection and electron acceleration.

Dejager, C.↗
NASA NTRS1987

Global excitation of wave phenomena in a dissipative multiconstituent medium. III - Response characteristics for different sources in the earth's thermosphere

A linear trasnfer function model of the earth's thermosphere which includes the electric field momentum source is used to study the differences in the response characteristics for Joule heating and momentum coupling in the thermosphere. It is found that, for Joule/particle heating, the temperature and density perturbations contain a relatively large trapped component which has the property of a low-pass filter, with slow decay after the source is turned off. The decay time is sensitive to the altitude of energy deposition and is significantly reduced as the source peak moves from 125 to 150 km. For electric field momentum coupling, the trapped components in the temperature and density perturbations are relatively small. In the curl field of the velocity, however, the trapped component dominates, but compared with the temperature and density its decay time is much shorter. Outside the source region the form of excitation is of secondary importance for the generation of the various propagating gravity wave modes.

Mayr, H. G.↗
NASA NTRS1993

Basic statistical analyses of candidate nickel-hydrogen cells for the Space Station Freedom

Nickel-Hydrogen (Ni/H2) secondary batteries will be implemented as a power source for the Space Station Freedom as well as for other NASA missions. Consequently, characterization tests of Ni/H2 cells from Eagle-Picher, Whittaker-Yardney, and Hughes were completed at the NASA Lewis Research Center. Watt-hour efficiencies of each Ni/H2 cell were measured for regulated charge and discharge cycles as a function of temperature, charge rate, discharge rate, and state of charge. Temperatures ranged from -5 C to 30 C, charge rates ranged from C/10 to 1C, discharge rates ranged from C/10 to 2C, and states of charge ranged from 20 percent to 100 percent. Results from regression analyses and analyses of mean watt-hour efficiencies demonstrated that overall performance was best at temperatures between 10 C and 20 C while the discharge rate correlated most strongly with watt-hour efficiency. In general, the cell with back-to-back electrode arrangement, single stack, 26 percent KOH, and serrated zircar separator and the cell with a recirculating electrode arrangement, unit stack, 31 percent KOH, zircar separators performed best.

Maloney, Thomas M.↗
NASA NTRS1993

Impact mineralogy and chemistry of the cretaceous-tertiary boundary at DSDP site 576

We have identified the K/T boundary in pelagic clay sediments from cores at DSDP Site 576 in the western North Pacific. Detailed geochemical and trace mineralogical analyses of this boundary section are in progress and initial results indicate similarities and differences relative to the only other clay core investigated in detail; DSDP Site 596, a locality in the western South Pacific. Peak Ir concentrations of 13 ng/g in DSDP Hole 576B are virtually identical with those observed in the South Pacific, but in the North Pacific this peak is much narrower and the integrated Ir fluence of 85 ng cm(exp -2) is 4 times lower (320 in Hole 596). Of the 34 elements measured, only Ir and Cr were found to have anomalous concentrations in K/T boundary samples. Trace mineral residues were obtained by washing away clays and sequential chemical leaches (including HF) to remove typical hydrogenous and biogenous sediment components (e.g., zeolites and radiolarian opal). We attempted to quantitatively recover the entire trace mineral assemblage for grains greater than 30 micrometers in diameter. Our mineral residues were dominated by two phases: quartz and magnesioferrite spinel. Other non-opaque mineral grains we have positively identified were trace K-feldspar, plagioclase, corundum, and muscovite. Of these only K-feldspar exhibited planar deformation features (PDF). We have not found abundant plagioclase, as in the South Pacific suggesting that this phase was either not preserved in the North Pacific, or that in the south, it has a non-impact (i.e., volcanic) source. PDF in quartz were commonly obscured by secondary overgrowths on the surfaces of quartz grains, presumably from diagenetic reprecipitation of silica dissolved from opaline radiolarian tests that are common in these sediments. However, careful examination revealed that most grains had multiple sets of PDF. Of the 133 quartz grains greater than 30 micrometers analyzed, 62 percent showed evidence of shock. The largest shocked grain recovered to date had a maximum diameter of 160 micrometers, consistent with other sites in the Pacific.

Bostwick, Jennifer A.↗
NASA NTRS1993

Forback DC-to-DC converter

A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

Lukemire, Alan T.↗
NASA NTRS1995

Forback DC-to-DC converter

A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

Lukemire, Alan T.↗
NASA NTRS1997

Comparison Between Predictions & Observations of Induced Radioactive Background in Interplanetary Missions

Radioactivity induced in detector materials and their immediate surroundings is the major source of discrete-line, gamma-ray background and an important source of continuum background in the performance of remote-sensing, gamma-ray spectroscopy of planetary bodies. In interplanetary space the dominant sources of particles are cosmic rays and their secondaries arising from interactions with the spacecraft and the surface of the target body. In addition, certain future gamma-ray astronomy missions, such as INTEGRAL, are to be located so as to perform their observations in interplanetary space rather than in the traditional low earth orbits. Such location removes contributions from the earth's atmosphere and inner radiation belt at the expense of increased exposure to cosmic rays and solar particle events. Accurate prediction of the activation of key materials by cosmic rays is of the utmost importance for detector design and data interpretation.

Dyer, Clivea↗
NASA NTRS1999

Numerical Simulation of Complex Turbomachinery Flows

An unsteady, multiblock, Reynolds Averaged Navier Stokes solver based on Runge-Kutta scheme and Pseudo-time step for turbo-machinery applications was developed. The code was validated and assessed against analytical and experimental data. It was used to study a variety of physical mechanisms of unsteady, three-dimensional, turbulent, transitional, and cooling flows in compressors and turbines. Flow over a cylinder has been used to study effects of numerical aspects on accuracy of prediction of wake decay and transition, and to modify K-epsilon models. The following simulations have been performed: (a) Unsteady flow in a compressor cascade: Three low Reynolds number turbulence models have been assessed and data compared with Euler/boundary layer predictions. Major flow features associated with wake induced transition were predicted and studied; (b) Nozzle wake-rotor interaction in a turbine: Results compared to LDV data in design and off-design conditions, and cause and effect of unsteady flow in turbine rotors were analyzed; (c) Flow in the low-pressure turbine: Assessed capability of the code to predict transitional, attached and separated flows at a wide range of low Reynolds numbers and inlet freestream turbulence intensity. Several turbulence and transition models have been employed and comparisons made to experiments; (d) leading edge film cooling at compound angle: Comparisons were made with experiments, and the flow physics of the associated vortical structures were studied; and (e) Tip leakage flow in a turbine. The physics of the secondary flow in a rotor was studied and sources of loss identified.

Chernobrovkin, A. A.↗