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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

FE Line Diagnostics of Multiply Shocked Stellar Atmospheres: The Mira S. Carinae

Extensive LWP-HI spectra were obtained of the Mira S Car at a rapid time cadence as compared with the shock cycle time of S Car. These spectra were obtained in an attempt to understand the velocity structures in the shocked wind using the fluoresced iron lines. Data analysis of the IUE observations, which included the primary calibration of all of the IUE spectra obtained of S Car, was carried out. In addition, line identifications, flux calculations, background subtractions, and line profile analysis as a function of S Car's pulsational phase were performed. The database incorporated all line identifications as a function of pulsation phase for all IUE LWP-HI observations to date of S Car. At least 45 separate iron line features are identified in the S Car spectrum at one or more phases of the shock cycle, including those due to Fe II (UV 161) which is pumped by three different iron lines; Fe I(UV 44) which is pumped by the Mg II k line. Other strong multiplets that have been identified include UV(1), UV(2), UV(5), UV(32), UV(60), UV(63), UV(161), UV(207), and UV(399). Over 300 weaker lines have also been tentatively identified with Fe line transitions.

Bookbinder, Jay↗
NASA NTRS2002

Latitude-Dependent Effects in the Stellar Wind of Eta Carinae

The Homunculus reflection nebula around eta Carinae provides the rare opportunity to observe the spectrum of a star from more than one direction. In the case of eta Car, the nebula's geometry is known well enough to infer how wind profiles vary with latitude. We present STIS spectra of several positions in the Homunculus, showing directly that eta Car has an aspherical and axisymmetric stellar wind. P Cygni absorption in Balmer lines depends on latitude, with relatively high velocities and strong absorption near the polar axis. Stronger absorption at high latitudes is surprising, and it suggests higher mass flux toward the poles, perhaps resulting from equatorial gravity darkening on a rotating star. Reflected profiles of He I lines are more puzzling, and offer clues to eta Car's wind geometry and ionization structure. During eta Car's high-excitation state in March 2000, the wind had a fast, dense polar wind, with higher ionization at low latitudes. Older STIS data obtained since 1998 reveal that this global stellar-wind geometry changes during eta Car's 5.5 year cycle, and may suggest that this star s spectroscopic events are shell ejections. Whether or not a companion star triggers these outbursts remains ambiguous. The most dramatic changes in the wind occur at low latitudes, while the dense polar wind remains relatively undisturbed during an event. The apparent stability of the polar wind also supports the inferred bipolar geometry. The wind geometry and its variability have critical implications for understanding the 5.5 year cycle and long-term variability, but do not provide a clear alternative to the binary hypothesis for generating eta Car s X-rays.

Smith, Nathan↗
NASA NTRS1979

X-rays from Eta Carinae and the surrounding nebula

Two X-ray pictures have been obtained of the Eta Car nebula using the imaging detectors of the Einstein Observatory. One covers a field 1-deg square with a resolution of 1 arcmin; the second covers a field 25 arcmin in diameter with resolution of a few arcsec. These show a region of diffuse X-ray emission with luminosity 10 to the 35th ergs/s. The sources have been positively identified as the peculiar object Eta Car, a Wolf-Rayet star, a cluster of O stars, and five individual O stars. The Eta Car X-ray source is extended and coincides with the outer shell of the diffuse object Eta Car itself. One X-ray bright spot may be emission from a central object within Eta Car.

Seward, F. D.↗
NASA NTRS1983

Simultaneous observation of rotational coherent Stokes Raman scattering and coherent anti-Stokes Raman scattering in air and nitrogen

Rotational coherent Stokes Raman scattering (CSRS) and coherent anti-Stokes Raman scattering (CARS) in air and in nitrogen were observed simultaneously by using broadband generation and detection. In the broadband technique used, the entire CARS and CSRS spectrum was generated in a single laser pulse; the CSRS and CARS signals were dispersed by a spectrograph and detected simultaneously by an optical multichannel analyzer. A three-dimensional phase-matching geometry was used to achieve spatial resolution of the CSRS and CARS beams from the input beams. Under resonant conditions, similar experiments may provide a means of investigating the possible interaction between the CSRS and CARS processes in driving the rotational levels.

Snow, J. B.↗
NASA NTRS1990

Effects of atmospheric CO2 on photosynthetic characteristics of soybean leaves

Soybean (Glycine max. cv. McCall) plants were grown at 500, 1000, and 2000 umol mol (exp -1) CO2 for 35 days with a photosynthetic photon flux of 300 umol m (exp -2) s (-1). Individual leaves were exposed to step changes of photosynthetic photon flux to study CO2 assimilation rates (CAR), i.e., leaf net photosynthesis. In general, CAR increased when CO2 increased from 500 to 1000 umol mol (exp -1), but not from 1000 to 2000 umol mol (exp -1). Regardless of the CO2 level, all leaves showed similar CAR at similar CO2 and PPF. This observation contrasts with reports that plants tend to become 'lazy' at elevated CO2 levels over time. Although leaf stomatal conductance (to water vapor) showed diurnal rhythms entrained to the photoperiod, leaf CAR did not show these rhythms and remained constant across the light period, indicating that stomatal conductance had little effect on CAR. Such measurements suggest that short-term changes in CO2 exchange dynamics for a controlled ecological life support system can be closely predicted for an actively growing soybean crop.

Wheeler, R. M.↗
NASA NTRS1994

The axisymmetric stellar wind of AG Carinae

We present optical linear spectropolarimetry of the Luminous Blue Variable AG Carinae obtained after a recent visual brightness increase. The absence of He II lambda 4686 emission, together with the weakening of the He I spectrum and the appearance of Fe lines in the region around 5300 A, confirm that AG Car has started a new excursion across the HR diagram. The H alpha line profile exhibits very extended line wings that are polarized differently in both amount and position angle from either the continuum or the line core. The polarization changes across H alpha, together with variable continuum polarization, indicate the presence of intrinsic polarization. Coexistence of the line-wing polarization with extended flux-line wings evidences that both are formed by electron scattering in a dense wind. The position angle rotates across the line profiles, in a way that presently available models suggest is due to rotation and expansion of the scattering material. AG Car displays very large variations of its linear polarization with time, Delta P approximately 1.2%, indicating significant variations in envelope opacity. We find that the polarization varies along a preferred position angle of approximately 145 deg (with a scatter of +/- 10 deg) which we interpret as a symmetry axis of the stellar wind (with an ambiguity of 90 deg). This position angle is co-aligned with the major axis of the AG Car ring nebula and perpendicular to the AG Car jet. Our observations thus suggest that the axisymmetric geometry seen in the resolved circumstellar environment at various distances already exists within a few stellar radii of AG Car. From the H alpha polarization profile we deduce an interstellar polarization of Q = 0.31%, U = -1.15% at H alpha. The inferred interstellar polarization implies that the intrinsic polarization is not always of the same sign. This indicates either significant temporal changes in the envelope geometry, or it may arise from effects of multiple scattering in conjunction with density variations.

Schulte-Ladbeck, Regina E.↗
NASA NTRS1997

The Cloud Absorption Radiometer HDF Data User's Guide

The purpose of this document is to describe the Cloud Absorption Radiometer (CAR) Instrument, methods used in the CAR Hierarchical Data Format (HDF) data processing, the structure and format of the CAR HDF data files, and methods for accessing the data. Examples of CAR applications and their results are also presented. The CAR instrument is a multiwavelength scanning radiometer that measures the angular distributions of scattered radiation.

Li, Jason Y.↗
NASA NTRS1999

Novel Receptor-Based Countermeasures to Microgravity-Induced Bone Loss

The biological actions mediated by the estrogen receptor (ER), vitamin D receptor (VDR) and Ca(sup 2+) (sub o) -sensing receptor (CaR) play key roles in the normal control of bone growth and skeletal turnover that is necessary for skeletal health. These receptors act by controlling the differentiation and/or function of osteoblasts and osteoclasts, and other cell types within the bone and bone marrow microenvironment. The appropriate use of selective ER modulators (SERMS) which target bone, vitamin D analogs that favor bone formation relative to resorption, and CaR agonists may both stimulate osteoblastogenesis and inhibit osteoclastogenesis and the function of mature osteoclasts, should make it possible to prevent the reduction in bone formation and increase in bone resorption that normally contribute to the bone loss induced by weightlessness. Indeed, there may be synergistic interactions among these receptors that enhance the actions of any one used alone. Therefore, we proposed to: 1) assess the in vitro ability of novel ER, VDR and CaR agonists, alone or in combination, to modulate osteoblastogenesis and mature osteoblast function under conditions of 1g and simulated microgravity; 2) assess the in vitro ability of novel ER, VDR and CaR agonists, alone or in combination, to modulate osteoclastogenesis and bone resorption under conditions of lg and simulated microgravity; and 3) carry out baseline studies on the skeletal localization of the CaR in normal rat bone as well as the in vivo actions of our novel ER- and VDR-based therapeutics in the rat in preparation for their use, alone or in combination, in well-established ground-based models of microgravity and eventually in space flight.

OMalley, Bert W.↗
NASA NTRS1997

Automotive Insulation

Under a Space Act Agreement between Boeing North America and BSR Products, Space Shuttle Thermal Protection System (TPS) materials are now used to insulate race cars. BSR has created special TPS blanket insulation kits for use on autos that take part in NASCAR events, and other race cars through its nationwide catalog distribution system. Temperatures inside a race car's cockpit can soar to a sweltering 140 to 160 degrees, with the extreme heat coming through the engine firewall, transmission tunnel, and floor. It is common for NASCAR drivers to endure blisters and burns due to the excessive heat. Tests on a car insulated with the TPS material showed a temperature drop of some 50 degrees in the driver's cockpit. BSR-TPS Products, Inc. now manufactures insulation kits for distribution to race car teams around the world.

Source record↗
NASA NTRS2000

Extracellular calcium elicits a chemokinetic response from monocytes in vitro and in vivo

Recruitment of macrophages to sites of cell death is critical for induction of an immunologic response. Calcium concentrations in extracellular fluids vary markedly, and are particularly high at sites of injury or infection. We hypothesized that extracellular calcium participates in modulating the immune response, perhaps acting via the seven-transmembrane calcium-sensing receptor (CaR) on mature monocytes/macrophages. We observed a dose-dependent increase in monocyte chemotaxis in response to extracellular calcium or the selective allosteric CaR activator NPS R-467. In contrast, monocytes derived from mice deficient in CaR lacked the normal chemotactic response to a calcium gradient. Notably, CaR activation of monocytes bearing the receptor synergistically augmented the transmigration response of monocytes to the chemokine MCP-1 in association with increased cell-surface expression of its cognate receptor, CCR2. Conversely, stimulation of monocytes with MCP-1 or SDF-1alpha reciprocally increased CaR expression, suggesting a dual-enhancing interaction of Ca(2+) with chemokines in recruiting inflammatory cells. Subcutaneous administration in mice of Ca(2+), MCP-1, or (more potently) the combination of Ca(2+) and MCP-1, elicited an inflammatory infiltrate consisting of monocytes/macrophages. Thus extracellular calcium functions as an ionic chemokinetic agent capable of modulating the innate immune response in vivo and in vitro by direct and indirect actions on monocytic cells. Calcium deposition may be both consequence and cause of chronic inflammatory changes at sites of injury, infection, and atherosclerosis.

Non-NASA Center↗
NASA NTRS2006

Detection of a Hot Binary Companion of eta Carinae

A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from eta Car shortward of Lyman alpha disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, eta Car B, was also eclipsed by the dense wind or extended atmosphere of eta Car A. Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. N II 1084-1086 emission disappears at the same time as the far-UV continuum, indicating that this feature originates from eta Car B itself or in close proximity to it. The strong N II emission also raises the possibility that the companion star is nitrogen rich. The observed FUV flux levels and spectral features, combined with the timing of their disappearance, is consistent with eta Carinae being a massive binary system

Sonnebom, G.↗
NASA NTRS2006

Detection of a Hot Binary Companion of eta Carinae

A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1 180 Angsroms) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from eta Car shortward of Lyman alpha disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, eta Car By was also eclipsed by the dense wind or extended atmosphere of eta Car A. Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. N II 1084-1086 emission disappears at the same time as the far-UV continuum, indicating that this feature originates from eta Car B itself or in close proximity to it. The strong N II emission also raises the possibility that the companion star is nitrogen rich. The observed FUV flux levels and spectral features, combined with the timing of their disappearance, are consistent with eta Carinae being a massive binary system.

Sonneborn, G.↗
NASA NTRS2015

The Suomi National Polar-Orbiting Partnership (SNPP): Continuing NASA Research and Applications

The Suomi National Polar-orbiting Partnership (SNPP) satellite was successfully launched into a polar orbit on October 28, 2011 carrying 5 remote sensing instruments designed to provide data to improve weather forecasts and to increase understanding of long-term climate change. SNPP provides operational continuity of satellite-based observations for NOAA's Polar-orbiting Operational Environmental Satellites (POES) and continues the long-term record of climate quality observations established by NASA's Earth Observing System (EOS) satellites. In the 2003 to 2011 pre-launch timeframe, NASA's SNPP Science Team assessed the adequacy of the operational Raw Data Records (RDRs), Sensor Data Records (SDRs), and Environmental Data Records (EDRs) from the SNPP instruments for use in NASA Earth Science research, examined the operational algorithms used to produce those data records, and proposed a path forward for the production of climate quality products from SNPP. In order to perform these tasks, a distributed data system, the NASA Science Data Segment (SDS), ingested RDRs, SDRs, and EDRs from the NOAA Archive and Distribution and Interface Data Processing Segments, ADS and IDPS, respectively. The SDS also obtained operational algorithms for evaluation purposes from the NOAA Government Resource for Algorithm Verification, Independent Testing and Evaluation (GRAVITE). Within the NASA SDS, five Product Evaluation and Test Elements (PEATEs) received, ingested, and stored data and performed NASA's data processing, evaluation, and analysis activities. The distributed nature of this data distribution system was established by physically housing each PEATE within one of five Climate Analysis Research Systems (CARS) located at either at a NASA or a university institution. The CARS were organized around 5 key EDRs directly in support of the following NASA Earth Science focus areas: atmospheric sounding, ocean, land, ozone, and atmospheric composition products. The PEATES provided the system level interface with members of the NASA SNPP Science Team and other science investigators within each CARS. A sixth Earth Radiation Budget CARS was established at NASA Langley Research Center (NASA LaRC) to support instrument performance, data evaluation, and analysis for the SNPP Clouds and the Earth's Radiant Budget Energy System (CERES) instrument. Following the 2011 launch of SNPP, spacecraft commissioning, and instrument activation, the NASA SNPP Science Team evaluated the operational RDRs, SDRs, and EDRs produced by the NOAA ADS and IDPS. A key part in that evaluation was the NASA Science Team's independent processing of operational RDRs and SDRs to EDRs using the latest NASA science algorithms. The NASA science evaluation was completed in the December 2012 to April 2014 timeframe with the release of a series of NASA Science Team Discipline Reports. In summary, these reports indicated that the RDRs produced by the SNPP instruments were of sufficiently high quality to be used to create data products suitable for NASA Earth System science and applications. However, the quality of the SDRs and EDRs were found to vary greatly when considering suitability for NASA science. The need for improvements in operational algorithms, adoption of different algorithmic approaches, greater monitoring of on-orbit instrument calibration, greater attention to data product validation, and data reprocessing were prominent findings in the reports. In response to these findings, NASA, in late 2013, directed the NASA SNPP Science Team to use SNPP instrument data to develop data products of sufficiently high quality to enable the continuation of EOS time series data records and to develop innovative, practical applications of SNPP data. This direction necessitated a transition of the SDS data system from its pre-launch assessment mode to one of full data processing and production. To do this, the PEATES, which served as NASA's data product testing environment during the prelaunch and early on-orbit periods, were transitioned to Science Investigator-led Processing Systems (SIPS). The distributed data architecture was maintained in this new system by locating the SIPS at the same institutions at which the CARS and PEATES were located. The SIPS acquire raw SNPP instrument Level 0 (i.e. RDR) data over the full SNPP mission from the NOAA ADS and IDPS through the NASA SDS Data Distribution and Depository Element (SD3E). The SIPS process those data into NASA Level 1, Level 2, and global, gridded Level 3 standard products using peer-reviewed algorithms provided by members of the NASA Science Team. The SIPS work with the NASA SNPP Science Team in obtaining enhanced, refined, or alternate real-time algorithms to support the capabilities of the Direct Readout Laboratory (DRL). All data products, algorithm source codes, coefficients, and auxiliary data used in product generation are archived in an assigned NASA Distributed Active Archive Center (DAAC).

remote sensing↗
NASA NTRS2021

VLTI-MATISSE Chromatic Aperture-Synthesis Imaging of η Carinae’s Stellar Wind Across the Brα Line: Periastron Passage Observations in February 2020

Context: Eta Carinae is a highly eccentric, massive binary system (semimajor axis∼15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, ηCar A, is a luminous blue variable (LBV); the secondary, η Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV η Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims: Our aim is to study the intensity distribution and kinematics of η Car’s WWC zone. Methods: Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Brα imaging of η Car’s distorted wind. Results: We present the first VLTI-MATISSE aperture-synthesis images of η Car A’s stellar wind in several spectral channels distributed across the Brα 4.052 μm line (spectral resolving power R∼960). Our observations were performed close to periastron passage in February 2020 (orbital phase∼14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (∼14 au). The radius of the faintest outer wind regions is∼26 mas (∼60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84±0.06 mas (6.54±0.14 au). We compare the derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.

G Weigelt↗
NASA NTRS1981

IUE spectra of F and late A stars

The International Ultraviolet Explorer (IUE) spectra of alpha CMi (F5 IV-V), beta Cas (F2 IV), alpha Car (F0 Ib), and gamma Boo (A7 III) in the context of the question as to whether chromospheres disappear in the early F late A portions of the Hertzsprung-Russell diagram. Both alpha CMi (Procyon) and beta Cas show bright emission line spectra indicative of chromospheres and transition regions, but neither alpha Car (Canopus) nor gamma Boo show any evidence of emission in their SWP spectra or at the Mg II lines, despite very deep exposures. Alpha CMi has emission line fluxes roughly 6 times those of the quiet Sun, but the rapidly rotating delta Scuti type variable beta Cas has surface fluxes 10 to 50 times those of the quiet Sun. Upper limits on emission line fluxes for alpha Car are 4 to 20 and for gamma Boo 15 to 80 times the quiet Sun. It is concluded that the apparent absence of emission lines in the spectra of alpha Car and gamma Boo should not be interpreted as due to the absence of nonradiatively heated outer atmospheres in stars hotter than spectral type F0, but rather to the inability to see emission lines with IUE against a background of scattered light and a bright photospheric absorption line spectrum either in low or high dispersion.

Linsky, J. L.↗
NASA NTRS1981

Conventional engine technology. Volume 2: Status of diesel engine technology

The engines of diesel cars marketed in the United States were examined. Prominent design features, performance characteristics, fuel economy and emissions data were compared. Specific problems, in particular those of NO and smoke emissions, the effects of increasing dieselization on diesel fuel price and availability, current R&D work and advanced diesel concepts are discussed. Diesel cars currently have a fuel economy advantage over gasoline engine powered cars. Diesel drawbacks (noise and odor) were reduced to a less objectionable level. An equivalent gasoline engine driveability was obtained with turbocharging. Diesel manufacturers see a growth in the diesel market for the next ten years. Uncertainties regarding future emission regulation may inhibit future diesel production investments. With spark ignition engine technology advancing in the direction of high compression ratios, the fuel economy advantages of the diesel car is expected to diminish. To return its fuel economy lead, the diesel's potential for future improvement must be used.

Schneider, H. W.↗
NASA NTRS1983

Advanced automotive diesel assessment program

Cummins Engine Company completed an analytical study to identify an advanced automotive (light duty) diesel (AAD) power plant for a 3,000-pound passenger car. The study resulted in the definition of a revolutionary diesel engine with several novel features. A 3,000-pound car with this engine is predicted to give 96.3, 72.2, and 78.8 MPG in highway, city, and combined highway-city driving, respectively. This compares with current diesel powered cars yielding 41.7, 35.0, and 37.7 MPG. The time for 0-60 MPH acceleration is 13.9 sec. compared to the baseline of 15.2 sec. Four technology areas were identified as crucial in bringing this concept to fruition. They are: (1) part-load preheating, (2) positive displacement compounding, (3) spark assisted diesel combustion system, and (4) piston development for adiabatic, oilless diesel engine. Marketing and planning studies indicate that an aggressive program with significant commitment could result in a production car in 10 years from the date of commencement.

Sekar, R.↗
NASA NTRS1994

Geometry and physical conditions in the stellar wind of AG Carinae

AG Carinae is one of the prototypes of the class of Luminous Blue Variables (LBVs). Since 1990 the star has continuously brightened in its visual continuum. We report on a multi-instrument and -wavelength observing campaign to monitor the current activity phase of AG Car. Ground-based photometry, polarimetry, spectroscopy, and space-ultraviolet spectroscopy and spectropolarimetry have been obtained. From the variability of the polarization at ultraviolet and optical wavelengths we detect significant intrinsic polarization. P(sub int) greater than or equal to 0.5% is a large value for a hot, luminous star, suggesting departure from spherical symmetry in the wind of AG Car. The intrinsic polarization is variable on a timescale of 2 months or less. The measured ultraviolet polarization (intrinsic + interstellar) dropped to 0.5% in 1992 May and returned to 1% in 1992 July. The results are interpreted in terms of a variable outflow with a density enhancement in the equatorial plane. A similar model was suggested for the related object R127 in the Large Magellanic Cloud (LMC). This geometry is reminiscent of the large-scale morphology of the gas nebula and dust 'jet' surrounding AG Car. It is therefore likely that physical conditions close to the stellar surface are responsible for the geometry of the spatially resolved circumstellar material around AG Car. Despite the drastic change of the photospheric conditions, the mass-loss rate did not increase. We find no evidence for a positive correlation between wind density and stellar radius. This makes models that explain the radius increase by opacity effects in the outflow unlikely. The mechanism responsible for the temperature and radius variations is still unknown but most likely has its origin in subphotospheric regions.

Leitherer, Claus↗