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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The Liquid Droplet Radiator - an Ultralightweight Heat Rejection System for Efficient Energy Conversion in Space

A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets ( 100 micron diameter) of low vapor pressure liquids the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejectioon are discussed and solutions are suggested.

A T Mattick↗
NASA NTRS1994

Diurnal heating and cloudiness in the NCAR Community Climate Model (CCM2)

In this paper, the authors assess the suitability of the heating fileds in the latest version of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM2) for modeling the thermal forcing of atmospheric tides. Accordingly, diurnal variations of the surface pressure, outgoing longwave radiation (OLR), cloudiness, and precipitation are examined in the CCM2. The fields of radiative, sensible, and latent heating are similarly analyzed. These results are subjectively compared with available data. Equatorial diurnal surface pressure tides are fairly well simulated by CCM2. The model successfully reproduces the semidiurnal surface pressure tides; however, this may result in part from reflection of wave energy at the upper boundary. The CCM2 large-scale diurnal OLR is generally consistent with observations. The moist-convective scheme in the model is able to reproduce the diurnally varying cloudiness and precipitation patterns associated with land-sea contrasts; however, the amplitudes of CCM2 diurnal continental convective cloudiness are weaker than observations. The CCM2 boundary-layer sensible heating is consistent with a very limited set of observations, and with estimates obtained from simple models of diffusive heating. Although the CCM2 tropospheric solar radiative heating is similar in magnitude to previous estimates, there are substantial differences in the vertical structures. A definitive assessment of the validity of the CCM2 diurnal cycle is precluded by the lack of detailed observations and the limitations of our CCM2 sample. Nevertheless, the authors conclude that the global-scale components of the CCM2 diurnal heating are useful proxies for the true diurnal forcing of the tides.

Lieberman, Ruth S.↗
NASA NTRS2014

Grid Sensitivity Study for Slat Noise Simulations

The slat noise from the 30P/30N high-lift system is being investigated through computational fluid dynamics simulations in conjunction with a Ffowcs Williams-Hawkings acoustics solver. Many previous simulations have been performed for the configuration, and the case was introduced as a new category for the Second AIAA workshop on Benchmark problems for Airframe Noise Configurations (BANC-II). However, the cost of the simulations has restricted the study of grid resolution effects to a baseline grid and coarser meshes. In the present study, two different approaches are being used to investigate the effect of finer resolution of near-field unsteady structures. First, a standard grid refinement by a factor of two is used, and the calculations are performed by using the same CFL3D solver employed in the majority of the previous simulations. Second, the OVERFLOW code is applied to the baseline grid, but with a 5th-order upwind spatial discretization as compared with the second-order discretization used in the CFL3D simulations. In general, the fine grid CFL3D simulation and OVERFLOW calculation are in very good agreement and exhibit the lowest levels of both surface pressure fluctuations and radiated noise. Although the smaller scales resolved by these simulations increase the velocity fluctuation levels, they appear to mitigate the influence of the larger scales on the surface pressure. These new simulations are used to investigate the influence of the grid on unsteady high-lift simulations and to gain a better understanding of the physics responsible for the noise generation and radiation.

Lockard, David P.↗
NASA NTRS1979

The dynamics and stability of radiatively driven gas clouds. I - Plane-parallel slabs

A combination of numerical and analytical techniques has been used to investigate the dynamics and stability of optically thin plane-parallel radiatively driven slabs of gas confined by the thermal gas pressure of a high-temperature low-density medium. Scaling laws allow the individual model 'clouds' to be characterized by a single free parameter, chi, a normalized column density which measures the strength of the acceleration due to radiation pressure relative to that due to thermal gas pressure. It is found that these clouds are stable and coherently accelerated only when chi is small. In this regime a simple slab model is constructed which accurately reproduces the more complex gasdynamic results. The low-chi clouds are marginally able to reach the high velocities seen in the atmospheres of quasi-stellar objects, but only if their motion is subsonic with respect to the external confining medium. This implies either that the medium is extremely hot and tenuous or that it is moving outward with the clouds.

Haas, M. R.↗
NASA NTRS1983

Temperatures of shock-induced shear instabilities and their relationship to fusion curves

New emission spectra for MgO and CaAl2Si2O8 (glass) are observed from 430 to 820 nm. Taken with previous data, it is suggested that transparent solids display three regimes of light emission upon shock compression to successively higher pressures: (1) characteristic radiation such as observed in MgO and previously in other minerals, (2) heterogeneous hot spot (greybody) radiation observed in CaAl2Si2O8 and previously in all transparent solids undergoing shock-induced phase transformations, and (3) blackbody emission observed in the high pressure phase regime in NaCl, SiO2, CaO, CaAl2Si2O8, and Mg2SiO4. The onset of the second regime may delineate the onset of shock-induced polymorphism whereas the onset of the third regime delineates the Hugoniot pressure required to achieve local thermal equilibrium in the shocked solid. It is also proposed that the hot spot temperatures and corresponding shock pressures determined in the second regime delineate points on the fusion curves of the high pressure phase.

Schmitt, D. R.↗
NASA NTRS2009

Terahertz NDE of Stressed Composite Overwrapped Pressure Vessels - Initial Testing

Terahertz radiation nondestructive evaluation was applied to a set of Kevlar composite overwrapped pressure vessel bottles that had undergone a series of thermal and pressure tests to simulate stress rupture effects. The bottles in these nondestructive evaluation tests were bottles that had not ruptured but had survived various times at the elevated load and temperature levels. Some of the bottles showed evidence of minor composite failures. The terahertz radiation did detect visible surface flaws, but did not detect any internal chemical or material degradation of the thin overwraps.

Madaras, Eric I.↗
DOE OSTI2023

Thermodynamic and kinematic drivers of atmospheric boundary layer stability in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC)

Observations collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) provide a detailed description of the impact of thermodynamic and kinematic forcings on atmospheric boundary layer (ABL) stability in the central Arctic. This study reveals that the Arctic ABL is stable and near-neutral with similar frequencies, and strong stability is the most persistent of all stability regimes. MOSAiC radiosonde observations, in conjunction with observations from additional measurement platforms, including a 10 m meteorological tower, ceilometer, microwave radiometer, and radiation station, provide insight into the relationships between atmospheric stability and various atmospheric thermodynamic and kinematic forcings of ABL turbulence and how these relationships differ by season. We found that stronger stability largely occurs in low-wind (i.e., wind speeds are slow), low-radiation (i.e., surface radiative fluxes are minimal) environments; a very shallow mixed ABL forms in low-wind, high-radiation environments; weak stability occurs in high-wind, moderate-radiation environments; and a near-neutral ABL forms in high-wind, high-radiation environments. Surface pressure (a proxy for synoptic staging) partially explains the observed wind speeds for different stability regimes. Cloud frequency and atmospheric moisture contribute to the observed surface radiation budget. Unique to summer, stronger stability may also form when moist air is advected from over the warmer open ocean to over the colder sea ice surface, which decouples the colder near-surface atmosphere from the advected layer, and is identifiable through observations of fog and atmospheric moisture.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1979

Effects of probe shape change on flow phenomena during Jovian entry

The effects of probe shape change on the flow phenomena around a Jovian entry body is investigated. The initial body shapes considered are: 45-degree sphere cone, 35-degree hyperboloid, and 45-degree ellipsoid. The radiating shock-layer flow is assumed to be axisymmetric, inviscid, and in chemical and local thermodynamic equilibrium. The radiative transfer is calculated with an existing nongray radiation model that accounts for molecular band, atomic line, and continuum transitions. The results indicate that the shock-standoff distance, shock temperature and density, wall pressure distribution and radiative heating to the body are influenced significantly because of the probe shape change. The effect of shape change on radiative heating of the afterbody was considerably larger for the sphere cone and ellipsoid than for the hyperboloid. For the peak heating conditions, the net radiative heating to the body was found to be highest for the ellipsoid

Tiwari, S. N.↗
DOE OSTI2023

Exposure to multiple ion beams, broadly representative of galactic cosmic rays, causes perivascular cardiac fibrosis in mature male rats

Long-duration space exploratory missions to the Earth’s moon and the planet Mars are actively being planned. Such missions will require humans to live for prolonged periods beyond low earth orbit where astronauts will be continuously exposed to high energy galactic cosmic rays (GCRs). A major unknown is the potential impact of GCRs on the risks of developing degenerative cardiovascular disease, which is a concern to NASA. A ground-based rat model has been used to provide a detailed characterization of the risk of long-term cardiovascular disease from components of GCRs at radiation doses relevant to future human missions beyond low earth orbit. Six month old male WAG/RijCmcr rats were irradiated at a ground-based charged particle accelerator facility with high energy ion beams broadly representative of GCRs: protons, silicon and iron. Irradiation was given either as a single ion beam or as a combination of three ion beams. For the doses used, the single ion beam studies did not show any significant changes in the known cardiac risk factors and no evidence of cardiovascular disease could be demonstrated. In the three ion beam study, the total cholesterol levels in the circulation increased modestly over the 270 day follow up period, and inflammatory cytokines were also increased, transiently, 30 days after irradiation. Perivascular cardiac collagen content, systolic blood pressure and the number of macrophages found in the kidney and in the heart were each increased 270 days after irradiation with 1.5 Gy of the three ion beam grouping. These findings provide evidence for a cardiac vascular pathology and indicate a possible threshold dose for perivascular cardiac fibrosis and increased systemic systolic blood pressure for complex radiation fields during the 9 month follow up period. The development of perivascular cardiac fibrosis and increased systemic systolic blood pressure occurred at a physical dose of the three ion beam grouping (1.5 Gy) that was much lower than that required to show similar outcomes in earlier studies with the same rat strain exposed to photons. Further studies with longer follow up periods may help determine whether humans exposed to lower, mission-relevant doses of GCRs will develop radiation-induced heart disease.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Weather data at The Morton Arboretum 2017-2023

We have been monitoring long-term weather patterns using two weather stations at The Morton Arboretum to link environmental conditions to tree growth and other tree responses. This data package contains weather data at The Morton Arboretum from 2017-08-23 to 2023-12-31; data is located in the "MortonWeatherData2017_2023.csv" file. The two weather stations are located on each side of The Arboretum (e.g., the Nursery station on the East side and the Ware Field station on the West side; the two weather stations are 3.23 km apart and coordinates are included in the "Location_metadata.csv" file). Measured variables include rain accumulation, air temperature, relative humidity, three soil moisture/temperature measurements at various depths (10, 30, and 50 cm for the Nursery weather station, and 10, 25, and 50 cm for the Ware Field), solar radiation, saturation vapor pressure, and vapor pressure deficit.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1992

Synchrotron infrared spectroscopy at megabar pressures - Vibrational dynamics of hydrogen to 180 GPa

New techniques for measuring infrared spectra at megabar pressures using synchrotron radiation have been developed and applied to study the Q1(1), Qi(1) + Si(0), and QR(J) vibrational transitions of solid hydrogen to 180 GPa. The frequency difference between the Q1(1) infrared and Raman vibrons increases from 3/cm (zero pressure) to 510/cm (180 GPa), indicating a dramatic increase in intermolecular coupling with pressure. A negative frequency shift is observed for the infrared vibron above 140 GPa. A significant increase in frequency and LO-TO splitting of the lattice phonon is also documented.

Hanfland, M.↗
NASA NTRS1978

Significance of radiation models in investigating the flow phenomena around a Jovian entry body

Formulation is presented to demonstrate the significance of a simplified radiation model in investigating the flow-phenomena in the viscous radiating shock layer of a Jovian entry body. For this, a nongray absorption model for hydrogen-helium gas is developed which consists of 30 steps over the spectral range of 0-20 eV. By employing this model results were obtained for temperature, pressure, density, and radiative flux in the shock layer and along the body surface. These are compared with results of two sophisticated radiative transport models available in the literature. Use of the present radiation model results in significant reduction in computational time. Results of this model are found to be in general agreement with results of other models. It is concluded that use of the present model is justified in investigating the flow phenomena around a Jovian entry body because it is relatively simple, computationally fast, and yields fairly accurate results.

Tiwari, S. N.↗
NASA NTRS1994

Hot accretion disks with pairs: Effects of magnetic field and thermal cyclocsynchrotron radiation

We show the effects of thermal cyclosynchrotron radiation and magnetic viscosity on the structure of hot, two-temperature accretion disks. Magnetic field, B, is assumed to be randomly oriented and the ratio of magnetic pressure to either gas pressure, alpha = P(sub mag)/P(sub gas), or the sum of the gas and radiation pressures, alpha = (P(sub mag)/P(sub gas) + P(sub rad)), is fixed. We find those effects do not change the qualitative properties of the disks, i.e., there are still two critical accretion rates related to production of e(sup +/-) pairs, (M dot)((sup U)(sub cr)) and (M dot)((sup L)(sub cr)), that affect the number of local and global disk solutions, as recently found by Bjoernsson and Svensson for the case with B = 0. However, a critical value of the alpha-viscosity parameter above which those critical accretion rates disappear becomes smaller than alpha(sub cr) = 1 found in the case of B = 0, for P(sub mag) = alpha(P(sub gas) + P(sub rad)). If P(sub mag) = alpha P(sub gas), on the other hand, alpha(sub cr) is still about unity. Moreover, when Comptonized cyclosynchrotron radiation dominates Comptonized bremsstrahlung, radiation from the disk obeys a power law with the energy spectral index of approximately 0.5, in a qualitative agreement with X-ray observations of active galactic nuclei (AGNS) and Galactic black hole candidates. We also extend the hot disk solutions for P(sub mag) = alpha(P(sub gas) + P(sub rad)) to the effectively optically thick region, where they merge with the standard cold disk solutions. We find that the mapping method by Bjoernsson and Svensson gives a good approximation to the disk structure in the hot region and show where it breaks in the transition region. Finally, we find a region in the disk parameter space with no solutions due to the inability of Coulomb heating to supply enough energy to electrons.

Kusunose, Masaaki↗
NASA NTRS2007

A Reanalysis for the Seasonal and Longer-Period Cycles and the Trends in Middle Atmosphere Temperature from the HALOE

Previously published analyses for the seasonal and longer-period cycles in middle atmosphere temperature versus pressure (or T(p)) from the Halogen Occultation Experiment (HALOE) are extended to just over 14 years and updated to properly account for the effects of autocorrelation in its time series of zonally-averaged data. The updated seasonal terms and annual averages are provided, and they can be used to generate temperature distributions that are representative of the period 1991-2005. QBO-like terms have also been resolved and are provided, and they exhibit good consistency across the range of latitudes and pressure-altitudes. Further, exploratory analyses of the residuals from each of the 221 time series have yielded significant 11-yr solar cycle (or SC-like) and linear trend terms at a number of latitudes and levels. The amplitudes of the SC-like terms for the upper mesosphere agree reasonably with calculations of the direct solar radiative effects for T(p). Those SC amplitudes increase by about a factor of 2 from the lower to the upper mesosphere and are also larger at the middle than at the low latitudes. The diagnosed cooling trends for the subtropical latitudes are in the range, -0.5 to -1.0 K/decade, which is in good agreement with the findings from models of the radiative effects on pressure surfaces due to known increases in atmospheric CO2. The diagnosed trends are somewhat larger than predicted with models for the upper mesosphere of the northern hemisphere middle latitudes.

Remsberg, Ellis E.↗