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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Energetic charged particle angular distributions near (r less than or equal to 2 Neptune radii) and over the pole of Neptune

Energetic ion (greater than 28 keV) and electron (greater than 22 keV) pitch angle distributions very close to (r less than or equal to 2 Neptune radii) and over the north planetary pole of Neptune are presented using data from the Low Energy Charged Particle and magnetometer Experiments on the Voyager 2 spacecraft. The particle data are temporally structured and spectrally soft; a similarity with earth-like auroral signatures has previously been noted. However, the pitch angle distributions (showing trapped distributions at high magnetic latitudes) do not support an earth-like auroral interpretation, and alternative explanations for the temporal dynamics must be sought. Between r of about 1.6 and 2.0 Neptune radii and in the vicinity of the magnetic equator, the higher energy ion and electron pitch angle distributions (E greater than or equal to 80 keV) display dramatic 'bite-outs' at 90 deg. This bite-out feature could be caused by interactions with the newly discovered ring 1989N3R.

Mauk, B. H.↗
NASA NTRS1991

R-Parameterization Of Linear Feedback Systems

Classification of all compensators stabilizing given plant in linear, time-invariant, multiple-input/multiple-output feedback system developed. Necessary and sufficient conditions for stability examined via Q and R. Classification made according to stability conditions of compensators and plant by themselves, while necessary and sufficient conditions based on stabilities of Q and R by themselves.

Chen, Robert T. N.↗
NASA NTRS1989

On the polarization mechanism in the R Mon/NGC 2261 complex

The detection of circular polarization in R Mon and NGC 2261 is reported. This detection implies that the mechanism responsible for the linear and circular polarization is most likely multiple scattering in a flattened distribution. It replaces the previously suggested scenario where dichroic extinction by elongated dust grains aligned by a toroidal magnetic field was producing the polarization. The multiple scattering interpretation of linear polarization maps also means that these maps now provide direct evidence for a circumstellar disk around R Mon and possibly around many other young stellar objects.

Menard, Francois↗
NASA NTRS1991

Thermal performance of a liquid hydrogen tank multilayer insulation system at warm boundary temperatures of 630, 530, and 152 R

The results are presented of a study conducted to obtain experimental heat transfer data on a liquid hydrogen tank insulated with 34 layers of MLI (multilayer insulation) for warm side boundary temperatures of 630, 530, and 150 R. The MLI system consisted of two blankets, each blanket made up of alternate layers of double silk net (16 layers) and double aluminized Mylar radiation shields (15 layers) contained between two cover sheets of Dacron scrim reinforced Mylar. The insulation system was designed for and installed on a 87.6 in diameter liquid hydrogen tank. Nominal layer density of the insulation blankets is 45 layers/in. The insulation system contained penetrations for structural support, plumbing, and electrical wiring that would be representative of a cryogenic spacecraft. The total steady state heat transfer rates into the test tank for shroud temperatures of 630, 530, 152 R were 164.4, 95.8, and 15.9 BTU/hr respectively. The noninsulation heat leaks into the tank (12 fiberglass support struts, tank plumbing, and instrumentation lines) represent between 13 to 17 pct. of the total heat input. The heat input values would translate to liquid H2 losses of 2.3, 1.3, and 0.2 pct/day, with the tank held at atmospheric pressure.

Stochl, Robert J.↗
NASA NTRS1991

Thermal performance of a liquid hydrogen tank multilayer insulation system at warm boundary temperatures of 630, 530, and 152 R

The results are presented of a study conducted to obtain experimental heat transfer data on a liquid hydrogen tank insulated with 34 layers of MLI (multilayer insulation) for warm side boundary temperatures of 630, 530, and 150 R. The MLI system consisted of two blankets, each blanket made up of alternate layers of double silk net (16 layers) and double aluminized Mylar radiation shields (15 layers) contained between two cover sheets of Dacron scrim reinforced Mylar. The insulation system was designed for and installed on an 87.6 in. diameter liquid hydrogen tank. Nominal layer density of the insulation blankets is 45 layers/in. The insulation system contained penetrations for structural support, plumbing, and electrical wiring that would be representative of a cryogenic spacecraft. The total steady state heat transfer rates into the test tank for shroud temperatures of 630, 530, 152 R were 164.4, 95.8, and 15.9 BTU/hr, respectively. The noninsulation heat leaks into the tank (12 fiberglass support struts, tank plumbing, and instrumentation lines) represent between 13 to 17 pct. of the total heat input. The heat input values would translate to liquid H2 losses of 2.3, 1.3, and 0.2 pct/day, with the tank held at atmospheric pressure.

Stochl, Robert J.↗
NASA NTRS1992

Beamwidth effects on Z-R relations and area-integrated rainfall

The effective radar reflectivity Ze measured by a radar is the convolution of the actual distribution of reflectivity with the beam radiation pattern. Because of the nonlinearity between Z and rain rate R, Ze gives a biased estimator of R whenever the reflectivity field is nonuniform. In the presence of sharp horizontal reflectivity gradients, the measured pattern of Ze extends beyond the actual precipitation boundaries to produce false precipitation echoes. When integrated across the radar image of the storm, the false echo areas contribute to the sum to produce overestimates of the areal rainfall. As the range or beamwidth increases, the ratio of measured to actual rainfall increases. Beyond some range, the normal decrease of reflectivity with height dominates and the measured rainfall underestimates the actual amount.

Rosenfeld, Daniel↗
NASA NTRS1992

A comparative assessment of R. M. Young and tipping bucket rain gauges

Rain rates as derived from standard tipping bucket rain gauges have variable integration times corresponding to the interval between bucket tips. For example, the integration time for the Weathertronics rain gauge is given by delta(T) = 15.24/R (min), where R is the rain rate expressed in mm/h and delta(T) is the time between tips expressed in minutes. It is apparent that a rain rate of 1 mm/h has an integration time in excess of 15 minutes. Rain rates larger than 15.24 mm/h will have integration times smaller than 1 minute. The integration time is dictated by the time it takes to fill a small tipping bucket where each tip gives rise to 0.254 mm of rainfall. Hence, a uniform rain rate of 1 mm/h over a 15 minute period will give rise to the same rain rate as 0 mm/h rainfall over the first 14 minutes and 15 mm/h between 14 to 15 minutes from the reference tip. Hence, the rain intensity fluctuations may not be captured with the tipping bucket rain gauge for highly variable rates encompassing lower and higher values over a given integration time. The objective of this effort is to provide an assessment of the features of the R. M. Young capacitive gauge and to compare these features with those of the standard tipping bucket rain gauge. A number of rain rate-time series derived from measurements with approximately co-located gauges are examined.

Goldhirsh, Julius↗
NASA NTRS1992

The alpha-process and the r-process

The paper explores the alpha-rich freeze-out for values of neutron excesses larger than previously treated, and reports the discovery of nuclear systematics that, for neutron excesses greater than about 0.05, allow the creation of heavier elements all the way up to A of about 100, even when most of the ejecta is in the form of heavy elements. It is found that a large part of the nuclear flow in the r-process may be carried by charged particle reactions up to about A of about 100. It is speculated that the site of these processes is the high-entropy 'wind' of a young neutron star in which neutrino energy deposition is driving mass loss. The pass of r-process ejected per supernova is expected to be about 0.0001 solar mass per Type II or Ib supernova, but this is sensitive to details of the presupernova structure, the explosion mechanism, and the amount of material that falls back onto the neutron star when the reverse shock arrives there.

Woosley, S. E.↗
NASA NTRS1991

S-R compatibility effects with orthogonal stimulus and response dimensions

An experiment was conducted to assess the relative influence of several factors on performance with orthogonal stimulus-response arrays. Subjects responded to the onset of one of three aligned light circles with a press of one of three aligned response keys. The response array was aligned parallel, angled, or orthogonal to the stimulus array. The results indicated that performance with orthogonal arrays is worse than with parallel or angled S-R arrays. For the orthogonal arrangements, the results also indicate that each hand prefers a mapping directly opposite to the other hand, and that this mapping reverses when the orientation of the stimulus and response arrays are transposed. In addition, the results also revealed that the relative costs of orthogonal S-R arrangements are somewhat attenuated when the assigned mapping associates (i.e., colocates) a given display with its closest control.

Andre, Anthony D.↗
NASA NTRS1993

Evidence for precession of the R Aquarii jet

Several models of the R Aqr northeast jet have been proposed which attempt to explain the presence of shock excitation, resulting in a confusing picture of this nearest astrophysical jet. This paper compares observations of the jet in the R Aqr system with the HST's Faint Object Camera (FOC) and radio continuum images acquired with the VLA. The forbidden-O III jet structure is derived from restored FOC imagery, which has been convolved with an elliptical Gaussian of the same size as the restoring beam of the 6-cm VLA maps, allowing image comparison at the same spatial resolution. It is found that, at increasing distances from the central star, the forbidden O III emission knots that comprise the optical jet occur at systematically larger position angles when compared with corresponding features in the radio images. The angular separation of forbidden O III and radio continuum emission can be understood in terms of a shock formed when ejecta in the stream interacts with previously existing circumstellar material and subsequently cools by nebular line emission.

Hollis, J. M.↗
NASA NTRS1994

Nonlinear bulging factor based on R-curve data

In this paper, a nonlinear bulging factor is derived using a strain energy approach combined with dimensional analysis. The functional form of the bulging factor contains an empirical constant that is determined using R-curve data from unstiffened flat and curved panel tests. The determination of this empirical constant is based on the assumption that the R-curve is the same for both flat and curved panels.

Jeong, David Y.↗
NASA NTRS1994

Application of electron paramagnetic resonance imaging to the characterization of the Ultem(R) exposed to 1 MeV electrons. Correlation of radical density data to tiger code calculations

A major long-term goal of the Materials Division at the NASA Langley Research Center is the characterization of new high-performance materials that have potential applications in the aircraft industry, and in space. The materials used for space applications are often subjected to a harsh and potentially damaging radiation environment. The present study constitutes the application of a novel technique to obtain reliable data for ascertaining the molecular basis for the resilience and durability of materials that have been exposed to simulated space radiations. The radiations of greatest concern are energetic electrons and protons, as well as galactic cosmic rays. Presently, the effects of such radiation on matter are not understood in their entirety. It is clear however, that electron radiation causes ionization and homolytic bond rupture, resulting in the formation of paramagnetic spin centers in the polymer matrices of the structural materials. Since the detection and structure elucidation of paramagnetic species are most readily accomplished using Electron Paramagnetic Resonance (EPR) Spectroscopy, the NASA LaRC EPR system was brought back on-line during the 1991 ASEE term. The subsequent 1992 ASEE term was devoted to the adaptation of the EPR core system to meet the requirements for EPR Imaging (EPRI), which provides detailed information on the spatial distribution of paramagnetic species in bulk media. The present (1994) ASEE term was devoted to the calibration of this EPR Imaging system, as well as to the application of this technology to study the effects of electron irradiation on Ultem(exp R), a high performance polymer which is a candidate for applications in aerospace. The Ultem was exposed to a dose of 2.4 x 10(exp 9) Rads (1-MeV energy/electron) at the LaRC electron accelerator facility. Subsequently, the exposed specimens were stored in liquid nitrogen, until immediately prior to analyses by EPRI. The intensity and dimensions of the EPR Images that were generated for the irradiated specimens showed that the electrons penetrated the material to a depth of approximately 0.125 inch. These data show a very high degree of correlation to the energy deposition profile as predicted by the Tiger Code, a Monte Carlo code that provides guidelines for the transport of electrons in matter. Subsequent efforts will focus on delineating the transport properties of energetic protons in Ultem(R).

Suleman, Naushadalli K.↗
NASA NTRS1959

Water-Film Cooling of an 80 deg Total-Angle Cone at a Mach Number of 2 for Airstream Total Temperatures up to 3,000 deg R

Film-cooling tests, with water as the coolant, were made on an 80 deg total-angle cone in a Mach number 2 free jet at sea-level pressure. The tests were made at free-stream total temperatures from 1,500 deg R to 3,000 deg R and at free-stream Reynolds numbers per foot from 8 x 10(exp 6) to 3 x 10(exp 6). The tests showed that the downstream end of the model became very hot if the coolant rate was too small to cover the complete model with a water film. This water film was fairly symmetrical when the model was at zero angle of attack but was very asymmetrical when the model was at an angle of attack of 5 deg. A comparison with results of a previous transpiration-cooling test showed that, with water as the coolant, transpiration cooling was at least 2.5 times as efficient as the film cooling of the present tests.

Carter, Howard S.↗
NASA NTRS1994

Preparation and Dielectric Measurements of the Rare Earth Green Phases R2BaCuO(5-x) (R = Y, Sm, Gd, Dy, Ho, Er, Yb)

It has been demonstrated that R2BaCuO(5-x) (R = Y, Sm, Gd, Dy, Ho, Er, Yb) does not undergo significant densification unless the sintering temperatures are near the incongruent melting point or the sintering times are long. Good quality powders of Y2BaCuO(5-x) have been synthesized by using oxide raw materials or precursors such as acetates and nitrates. The acetates- and the nitrates-derived yttrium green phase resulted in finer particle sizes, acceptable dielectric properties and lower melting temperatures than those processed via oxide raw materials. The hot pressing technique has been employed to produce a dense R2BaCuO(5-x) (R=Y,Gd) substrate with satisfactory dielectric properties. Reactivity to reducing conditions, i.e. graphite die, limited the optimization of the properties. A high sensitivity to the annealing atmosphere has been demonstrated in Y2BaCuO,.,,. Oxygen treatment at 950 OC has been shown to improve the dielectric properties while treatment in nitrogen, at the same temperature, degraded desirable properties. A high sensitivity to the annealing atmosphere has been demonstrated in Y2BaCuO(5-x). Oxygen treatment at 950 C has been shown to improve the dielectric properties while treatment in nitrogen, at the same temperature, degraded desirable properties. The dielectric constants of the rare earth green phases R2BaCuO(5-x) were found to be low. Relaxation peaks were detected at low temperatures (T less than 150 K) and at high temperatures (150 less than T greater than 420 K). The dielectric losses and conductivities at 77 K were measured to be in the range of 10(exp -4) and 10(exp -12) (Omega-cm)(exp -1), respectively. Many parameters were found to exhibit dependencies on the rare earth cation sizes.

Gonzalez-Titman, Carlos↗
NASA NTRS2000

Federal R and D Reductions, Market Share, and Aerospace Information Usage

Reductions in federally funded research have a rippling effect over the entire aerospace industry. The decline in federal R&D spending in aerospace in recent years coincides with declines in U.S. aerospace market share, One of the lesser-understood factors in the declining U.S. market share may be the differing ways and intensity with which the U.S. and its competitors approach another trend, the increasing availability of large amounts of aerospace research information on the World Wide Web. The U.S. has been a pioneer in making research information available in electronic form, and the international community has long been a heavy consumer of that information. In essence, the U.S. contributes to the research efforts of its competitors, thus contributing to foreign aerospace consortiums efforts to gain market share in the aerospace industry, This may be a cautionary note to the U.S. aerospace industry to consider the use of R&D output in its own development and strategy because the foreign competition is using the U.S. scientific and technical literature.

Rocker, JoAnne↗
NASA NTRS2000

CM and DM in an ISO R and D Environment

ISO 9000 - a common buzz word in industry is making inroads to government agencies. The National Aeronautics and Space Agency (NASA) achieved ISO 9001 certification at each of its nine (9) Centers and Headquarters in 1998-1999. NASA Glenn Research Center (GRC) was recommended for certification in September 1999. Since then, each of the Centers has been going through the semi-annual surveillance audits. Growing out of the manufacturing industry, successful application of the international quality standard to a research and development (R&D) environment has had its challenges. This paper will address how GRC applied Configuration Management (CM) and Data (or Document) Management (DM) to meet challenges to achieve ISO certification. One of the first challenges was to fit the ISO 9001-1994 elements to the GRC environment. Some of the elements fit well-Management Responsibility (4.1), Internal Audits (4.17), Document and Data Control (4.5). Other elements were not suited or applied easily to the R&D environment-Servicing (4.19), Statistical Techniques (4.20). Since GRC "builds" only one or two items at a time, these elements were considered not applicable to the environment.

Crowley, Sandra L.↗
NASA NTRS2004

The GOES-R Lightning Mapper Sensor

The Lightning Mapper Sensor on GOES-R builds on previous measurements of lightning from low earth orbit by the OTD (Optical Transient Detector) and LIS (Lightning Imaging Sensor) sensors. Unlike observations from low earth orbit, the GOES-R platform will allow continuous monitoring of lightning activity over the Continental United States and southern Canada, Central and South America, and portions of the Atlantic and Pacific Oceans. The LMS will detect total (cloud-to-ground and intracloud) lightning at storm scale resolution (approx. 8 km) using a highly sensitive Charge Coupled Device (CCD) detector array. Discrimination between lightning optical transients and a bright sunlit background scene is accomplished by employing spectral, spatial, and temporal filtering along with a background subtraction technique. The result is 24 hour detection capability of total lightning. These total lightning observations can be made available to users within about 20 seconds. Research indicates a number of ways that total lightning observations from LMS could benefit operational activities, including 1) potential increases in lead times and reduced false alarms for severe thunderstorm and tornado Warnings, 2) improved routing of &rail around thunderstorms, 3) support for spacecraft launches and landings, 4) improved ability to monitor tropical cyclone intensity, 5) ability to monitor thunderstorm intensification/weakening during radar outages or where radar coverage is poor, 6) better identification of deep convection for the initialization of numerical prediction models, 7) improved forest fire forecasts, 8) identification of convective initiation, 9) identification of heavy convective snowfall, and 10) enhanced temporal resolution of storm evolution (1 minute) than is available from radar observations. Total lightning data has been used in an operational environment since July 2003 at the Huntsville, Alabama National Weather Service office. Total lightning measurements are obtained by the North Alabama Lightning Mapping Array (LMA) and have successfully been used in warning decisions. Every 2 minutes, total lightning counts in 2 km by 2 km horizontal, 1 km vertical grids are available to forecasters on an AWIPS (Advanced Weather Interactive Processing System) workstation. Experience with the LMA total lightning data is used to illustrate the potential use of LMS data that would be available to forecasters across the US. This abstract is for submission as a presentation to the National Weather Association Annual Meeting to be held 16-21 October 2004 in Portland, OR. This abstract will be published in the conference proceedings.

Buechler, Dennis↗
NASA NTRS2004

Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core

We detected three extremely embedded X-ray sources in the R Corona Australis (R CrA) star forming core, IRS 7 region. Two weak X-ray sources are associated with the VLA centimeter radio sources 10E & W, whereas the third brightest source detected in the two XMM-Newton observations on March 2003 has no counterpart at any wavelengths. The large K-band upper-limit (19.4m) measured with the University of Hawaii 88-inch Telescope and strong absorption derived in X-rays (N(sub H) approx. 2.8 x 10(exp 23)/sq cm equivalent to A(sub v) approx. 180 m) indicate that the source is younger than typical Class I protostars, i.e. a Class 0 protostar or an intermittent phase between Class 0 and Class I protostars. The X-ray luminosity was less than one thirtieth (log L(sub x) less than or approx. equals 29.3 ergs/s) in the former Chandra observation in October 2000, which suggests that the X-ray activity, probably generated by magnetic activity, is triggered by an intermittent mass accretion episode such as FU Ori type outbursts. Because the source was detected at high significance in the XMM-Newton observations (approx. 2,000 cnts), X-ray properties of such young protostars can be well investigated for the first time. The light curves were constant in the 1st observation and increased linearly by a factor of two during 30 ksec in the 2nd observation. Both spectra showed iron K lines originated in hot thin-thermal plasma and fluorescence by cold gas. They can be reproduced by an absorbed thin-thermal plasma model with a Gaussian component at 6.4 keV (kT approx. 3-4 keV, L(sub x) approx. 7-20 x 10(exp 30) ergs/s). The rising timescale of the light curves in the 2nd observation was too slow for magnetically generated X-ray flares, whereas large equivalent width of the fluorescence iron K line in the 1st observation (approx. 810 eV) requires strong partial covering of the X-ray source. These results suggest that a confined hot (perhaps accretion) spot on the protostellar core was behind the star in the 1st observation and just appeared in the 2nd observation due to the core rotation with period of greater than or approx. 22.8 days, which is much slower than the break-up velocity previously assumed for young protostars. This means that the source had quiescent X-ray activity during the observations with an order of magnitude stronger level than Class I (older) protostars. We also consider whether the X-ray source associated with 10E could be shock heated plasma by a collision of a jet emanating from the tentative Class 0 object.

Hamaguchi, Ken-Ji↗