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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 307 records · Page 17

Interannual variability of the global net radiation balance and its consequence on global energy transport

Global cloudiness and radiation budget data from Nimbus 6 and 7 are used to investigate the role of cloud and surface radiative forcing and elements of the earth's general circulation. Although globally integrated cloud forcing is nearly zero, there are large regional imbalances and well regulated processes in the shortwave and longwave spectrum that control the meridional gradient structure of the net radiation balance and the factors modulating the east-west oriented North Africa-western Pacific energy transport dipole. The analysis demonstrates that clouds play a dual role in both the shortwave and longwave spectra in terms of tropical and midlatitude east-west gradients. The key result is that cloud forcing, although not always the principle regulator of interannual variability of the global climate, serves to reinforce the basic three-cell meridional circulation.

Smith, Eric A.↗

Analysis of local delaminations caused by angle ply matrix cracks

Two different families of graphite/epoxy laminates with similar layups but different stacking sequences, (0,theta,-theta) sub s and (-theta/theta/0) sub s were analyzed using three-dimensional finite element analysis for theta = 15 and 30 degrees. Delaminations were modeled in the -theta/theta interface, bounded by a matrix crack and the stress free edge. The total strain energy release rate, G, along the delamination front was computed using three different techniques: the virtual crack closure technique (VCCT), the equivalent domain Integral (EDI) technique, and a global energy balance technique. The opening fracture mode component of the strain energy release rate, Gl, along the delamination front was also computed for various delamination lengths using VCCT. The effect of residual thermal and moisture stresses on G was evaluated.

Salpekar, Satish A.↗

History and Development of the USAF Agriculture Meteorology Modeling System and resulting USAF-NASA Strategic Partnership

The USAF Weather (AFW) supports a number of military and U.S. government agencies by providing authoritative weather analysis and forecast products for any location globally, including soil moisture analyses. The long history of supporting soil moisture products and partnering with other U.S. government agencies led to the partnering between the U.S. Air Force (USAF) and NASA Goddard Space Flight Center, resulting in a merger of those organizations’ modeling systems, collaborative development of the Land Information System (LIS), and operational fielding of the system within the USAF 557th Weather Wing [557 WW; formerly, Headquarters Air Force Weather Agency (HQ AFWA)]. In 2009, the USAF implemented the NASA LIS and later made it the primary software system to generate global soil hydrology and energy budget products. The implementation of LIS delivered a significant upgrade over the existing Land Data Assimilation System (LDAS) the USAF operated, the Agriculture Meteorology (AGRMET) system. Implementation enabled the rapid integration of new LDAS technology into USAF operations, and led to a long-term NASA–USAF partnership resulting in continued development, integration, and implementation of new LIS capabilities. This paper documents both the history of the USAF Weather organization capabilities enabling the generation of soil moisture and other land surface analysis products, and describes the USAF–NASA partnership leading to the development of the merged LIS-AGRMET system. The article also presents a successful example of a mutually beneficial partnership that has enabled cutting-edge land analysis capabilities at the USAF, while transitioning NASA software and satellite data into USAF operations.

John Eylander↗

Laer-induced Breakdown Spectroscopy Instrument for Element Analysis of Planetary Surfaces

One of the most fundamental pieces of information about any planetary body is the elemental and mineralogical composition of its surface materials. We are developing an instrument to obtain such data at ranges of up to several hundreds of meters using the technique of Laser-Induced Breakdown Spectroscopy (LIBS). We envision our instrument being used from a spacecraft in close rendezvous with small bodies such as comets and asteroids, or deployed on surface-rover vehicles on large bodies such as Mars and the Moon. The elemental analysis is based on atomic emission spectroscopy of a laser-induced plasma or spark. A pulsed, diode pumped Nd:YAG laser of several hundred millijoules optical energy is used to vaporize and electronically excite the constituent elements of a rock surface remotely located from the laser. Light emitted from the excited plasma is collected and introduced to the entrance slit of a small grating spectrometer. The spectrally dispersed spark light is detected with either a linear photo diode array or area CCD array. When the latter detector is used, the optical and spectrometer components of the LIBS instrument can also be used in a passive imaging mode to collect and integrate reflected sunlight from the same rock surface. Absorption spectral analysis of this reflected light gives mineralogical information that provides a remote geochemical characterization of the rock surface. We performed laboratory calibrations in air and in vacuum on standard rock powders to quantify the LIBS analysis. We performed preliminary field tests using commercially available components to demonstrate remote LIBS analysis of terrestrial rock surfaces at ranges of over 25 m, and we have demonstrated compatibility with a six-wheeled Russian robotic rover vehicle. Based on these results, we believe that all major and most minor elements expected on planetary surfaces can be measured with absolute accuracy of 10-15 percent and much higher relative accuracy. We have performed preliminary systems analysis of a LIBS instrument to evaluate probable mass and power requirements; results of this analysis are summarized.

Blacic, J.↗

Challenges Facing Design and Analysis Tools

The design and analysis of future aerospace systems will strongly rely on advanced engineering analysis tools used in combination with risk mitigation procedures. The implications of such a trend place increased demands on these tools to assess off-nominal conditions, residual strength, damage propagation, and extreme loading conditions in order to understand and quantify these effects as they affect mission success. Advances in computer hardware such as CPU processing speed, memory, secondary storage, and visualization provide significant resources for the engineer to exploit in engineering design. The challenges facing design and analysis tools fall into three primary areas. The first area involves mechanics needs such as constitutive modeling, contact and penetration simulation, crack growth prediction, damage initiation and progression prediction, transient dynamics and deployment simulations, and solution algorithms. The second area involves computational needs such as fast, robust solvers, adaptivity for model and solution strategies, control processes for concurrent, distributed computing for uncertainty assessments, and immersive technology. Traditional finite element codes still require fast direct solvers which when coupled to current CPU power enables new insight as a result of high-fidelity modeling. The third area involves decision making by the analyst. This area involves the integration and interrogation of vast amounts of information - some global in character while local details are critical and often drive the design. The proposed presentation will describe and illustrate these areas using composite structures, energy-absorbing structures, and inflatable space structures. While certain engineering approximations within the finite element model may be adequate for global response prediction, they generally are inadequate in a design setting or when local response prediction is critical. Pitfalls to be avoided and trends for emerging analysis tools will be described.

Knight, Norman F., Jr.↗

Design and test of a flywheel energy storage unit for spacecraft application

This paper summarizes the design and test of a development flywheel energy storage device intended for spacecraft application. The flywheel unit is the prototype for the rotating assembly portion of an Integrated Power and Attitude Control System (IPACS). The paper includes a general description of the flywheel unit; specific design characteristics for the rotor and bearings, motor-generators, and electronics; an efficiency analysis; and test results for a research unit.

Cormack, A., III↗

Selected advanced aerodynamic and active control concepts development

A summary is presented of results obtained during analysis, design and test activities on six selected technical tasks directed at exploratory improvement of fuel efficiency for new and derivative transports. The work included investigations into the potential offered by natural laminar flow, improved surface coatings and advanced high lift concepts. Similar investigations covering optimum low-energy flight path control, integrated application of active controls and evaluation of primary flight control systems reliability and maintenance are also summarized. Recommendations are included for future work needed to exploit potential advancements.

Source record↗

A search for gamma-ray point sources with the Carpet shower array

A search for super-high energy gamma-ray point sources has been carried out. The well known source Cyg X-3 was observed first and preliminary results of data analysis are presented. There is not positive excess of showers from the source region, but phase analysis discovers a small pulse at phase 0.6 which corresponds to the integral flux (6 + or - 3) X 10 to the minus 14th power cm-2 sec-1 at E sub gamma 3x10 to the 14th power eV.

Alexeenko, V. V.↗

Analysis of supersonic flows using k-epsilon model and the RPLUS code: Progress towards high speed combustor analysis

The problem of interest here is the analysis of chemically reacting flow inside of supersonic ramjet combustors. Two key parameters need to be determined: mixing/combustion efficiency and kinetic energy efficiency. In order to determine these parameters, several potential loss mechanisms must be modeled correctly, including mixing, shear, turbulence, vorticity, shock waves, heat transfer, fuel injector drag, poor wall pressure integral, and chemical dissociation. This document discusses k-epsilon turbulence models for use in the RPLUS code for numerical modeling of combustor flow fields.

Lee, J.↗

Assessment of climate variability of the Greenland Ice Sheet: Integration of in situ and satellite data

The proposed research involves the application of multispectral satellite data in combination with ground truth measurements to monitor surface properties of the Greenland Ice Sheet which are essential for describing the energy and mass of the ice sheet. Several key components of the energy balance are parameterized using satellite data and in situ measurements. The analysis will be done for a ten year time period in order to get statistics on the seasonal and interannual variations of the surface processes and the climatology. Our goal is to investigate to what accuracy and over what geographic areas large scale snow properties and radiative fluxes can be derived based upon a combination of available remote sensing and meteorological data sets. Operational satellite sensors are calibrated based on ground measurements and atmospheric modeling prior to large scale analysis to ensure the quality of the satellite data. Further, several satellite sensors of different spatial and spectral resolution are intercompared to access the parameter accuracy. Proposed parameterization schemes to derive key component of the energy balance from satellite data are validated. For the understanding of the surface processes a field program was designed to collect information on spectral albedo, specular reflectance, soot content, grain size and the physical properties of different snow types. Further, the radiative and turbulent fluxes at the ice/snow surface are monitored for the parameterization and interpretation of the satellite data. The expected results include several baseline data sets of albedo, surface temperature, radiative fluxes, and different snow types of the entire Greenland Ice Sheet. These climatological data sets will be of potential use for climate sensitivity studies in the context of future climate change.

Steffen, K.↗

Assessment of climate variability of the Greenland ice sheet: Integration of in situ and satellite data

The proposed research involves the application of multispectral satellite data in combination with ground truth measurements to monitor surface properties of the Greenland ice sheet which are essential for describing the energy and mass of the ice sheet. Several key components of the energy balance are parameterized using satellite data and in situ measurements. The analysis will be done for a ten year time period in order to get statistics on the seasonal and interannual variations of the surface processes and the climatology. Our goal is to investigate to what accuracy and over what geographic areas large scale snow properties and radiative fluxes can be derived based upon a combination of available remote sensing and meterological data sets. Data analysis showed the following results: (1)cloud classification based on longwave sky radiation revealed that overcast sky occurred for 25% of the time in winter, and for 15% in spring and summer respectively (winter and summer both show the same occurrence of clear sky of approximately 26%); (2) comparison of aerodynamic profile method with eddy correlation method to derive sensible and latent heat flux showed good agreement in the diurnal cycle and the turbulent fluxes were underestimated with the aerodynamic method by 10 - 30% as compared to the in situ eddy flux method; (3) the katabatic wind shows a distinct diurnal cycle with a maximum in the morning (7-9 h solar time) and a minimum in the later afternoon (18 h solar time); (4) snow grain size was modeled with a surface energy balance model (SNTHERM) and compared with in situ measurements. Sharp decreases in the modeled snow grain size, caused by accumulation events such as precipitation and deposition, could be verified with observational data; (4) radiative transfer modeling of firn supports our beliefs that the observed trends in 18 and 19 GHz passive microwave brightness temperatures are attributable to accumulation rate changes (modeling also indicates the above relationship is detectable because of the presence of depth hoar; (5) snow melt can be detected by a distinct signal in the passive microwave cross-polarized gradient ratio (19h-37v)/(19h+37v) and has been used for wet/dry snow classification; (6) top of the atmosphere (TOA) broadband albedos were derived from AVHRR visible and near infrared reflectances for the entire ice sheet from May 1990 - June 1991, and the highest albedo values are found along the southeast coast of the ice sheet which is consistent with the summer peak of precipitation due to onshore flow loaded with high water vapor content (TOA albedo values dropped to around 40% along the south-western coast during July and August due to bare ice surfaces); and (7) the net all-wave radiation balance at the top of the atmosphere is negative over the entire ice sheet except for the summer months - June-July-August (in June, the net radiation balance is slightly positive over the dry snow areas--15 W/m2).

Steffen, K.↗

Full-Scale Direct Numerical Simulation of Two- and Three-Dimensional Instabilities and Rivulet Formulation in Heated Falling Films

A thin film draining on an inclined plate has been studied numerically using finite element method. Three-dimensional governing equations of continuity, momentum and energy with a moving boundary are integrated in an arbitrary Lagrangian Eulerian frame of reference. Kinematic equation is solved to precisely update interface location. Rivulet formation based on instability mechanism has been simulated using full-scale computation. Comparisons with long-wave theory are made to validate the numerical scheme. Detailed analysis of two- and three-dimensional nonlinear wave formation and spontaneous rupture forming rivulets under the influence of combined thermocapillary and surface-wave instabilities is performed.

Krishnamoorthy, S.↗

Assessment of Climate Variability of the Greenland Ice Sheet: Integration of In Situ and Satellite Data

The proposed research involves the application of multispectral satellite data in combination with ground truth measurements to monitor surface properties of the Greenland Ice Sheet which are essential for describing the energy and mass of the ice sheet. Several key components of the energy balance are parameterized using satellite data and in situ measurements. The analysis has been done for a 6 to 17 year time period in order to analyze the seasonal and interannual variations of the surface processes and the climatology. Our goal was to investigate to what accuracy and over what geographic areas large scale snow properties and radiative fluxes can be derived based upon a combination of available remote sensing and meteorological data sets. For the understanding of the surface processes a field program was designed to collect information on spectral albedo, specular reflectance, soot content, grain size and the physical properties of different snow types. Further, the radiative and turbulent fluxes at the ice/snow surface were monitored for the parameterization and interpretation of the satellite data. Highlights include AVHRR time series and surface based radiation measurements, passive microwave time series, and geodetic results from the ETH/CU camp.

Steffen, K.↗

Monte-Carlo Analysis of Minimum Thermocouple Depths using Icarus

Icarus is a three-dimensional, unstructured, finite-volume material response solver developed at NASA Ames Research Center and has been verified against other NASA material response tools like FIAT, which have a long history of successfully designing thermal protection system (TPS). Icarus solves a set of conservation equations for mass and energy and uses Darcy’s Law in place of momentum conservation. An ecosystem of material response tools has been built around a general-purposed Icarus library that in addition to the typical material response analysis also supports TPS sizing (1-D and multi-dimensional), uncertainty quantification, and has been successfully integrated into a multi-physics architecture built around US3D. In this paper, a brief overview of Icarus and its capabilities will be presented using an illustrative Monte Carlo analysis of the one-dimensional, in-depth material response of a representative Dragonfly trajectory.

Material Response↗

Monte-Carlo Analysis of Minimal Thermocouple Depths using Icarus

Icarus is a three-dimensional, unstructured, finite-volume material response solver developed at NASA Ames Research Center \cite{Schulz_2017} and has been verified against other NASA material response tools like FIAT, which have a long history of successfully designing thermal protection system (TPS). Icarus solves a set of conservation equations for mass and energy and uses Darcy’s Law in place of momentum conservation. An ecosystem of material response tools has been built around a general-purposed Icarus library that in addition to the typical material response analysis also supports TPS sizing (1-D and multi-dimensional), uncertainty quantification, and has been successfully integrated into a multi-physics architecture built around US3D \cite{Schroeder_2021}. In this paper, a brief overview of Icarus and its capabilities will be presented using an illustrative Monte Carlo analysis of the one-dimensional, in-depth material response of a representative Dragonfly trajectory.

Material Response↗

Criticality experiments and analysis of molybdenum reflected cylindrical uranyl fluoride water solution reactors

Clean criticality data were obtained from molybdenum-reflected cylindrical uranyl-fluoride-water solution reactors. Using ENDF/B molybdenum cross sections, a nine energy group two-dimensional transport calculation of a reflected reactor configuration predicted criticality to within 7 cents of the experimental value. For these reactors, it was necessary to compute the reflector resonance integral by a detailed transport calculation at the core-reflector interface volume in the energy region of the two dominant resonances of natural molybdenum.

Fieno, D.↗

Energetic electrons in the Jovian magnetosphere

Results are reported for a detailed analysis of Pioneer 10 data on energetic particle species in the magnetodisk region of Jupiter's magnetosphere. It is shown that the observed counting rates in the magnetodisk (beyond 20 Jupiter radii) were caused primarily by electrons with energies exceeding 0.06 MeV. Absolute omnidirectional electron intensities in the magnetodisk are presented for five integral energy ranges, and a model electron differential energy spectrum is found to fit the intensities throughout most of the encounter trajectory. It is suggested that the observed spectral shape results from losses of high-energy electrons by pitch-angle scattering. Observed equatorial energy spectra are used to compute distribution functions for several values of the first adiabatic invariant, mu. The radial profiles of the functions are found to have maxima at about 50 Jupiter radii inbound as well as at about 90 radii outbound and to diminish strongly for lesser radii. The large decreases in density are shown to require strong losses, and resonant electron whistler-mode pitch-angle scattering is suggested as a loss mechanism.

Baker, D. N.↗

Technology development for phosphoric acid fuel cell powerplant (phase 2)

The status of technology for the manufacturing and testing of 1200 sq. cm cell materials, components, and stacks for on-site integrated energy systems is assessed. Topics covered include: (1) preparation of thin layers of silicon carbide; (2) definition and control schemes for volume changes in phosphoric acid fuel cells; (3) preparation of low resin content graphite phenolic resin composites; (4) chemical corrosion of graphite-phenolic resin composites in hot phosphoric acid; (5) analysis of electrical resistance of composite materials for fuel cells; and (6) fuel cell performance and testing.

Christner, L.↗