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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

The X-43 Fin Actuation System Problem - Reliability in Shades of Gray

Following the loss of the first X-43 during launch, the mishap investigation board indicated the Fin Actuator System (FAS) needed to have a larger torque margin. To supply this added torque, a second actuator was added. The consequences of what seemed to be a simple modification would trouble the X-43 program. Because of the second actuator, a new computer board was required. This proved to be subject to electronic noise. This resulted in the actuator latch up in ground tests of the FAS for the second launch. Such a latch up would cause the Pegasus booster to fail, as the FAS was a single string system. The problem was corrected and the second flight was successful. The same modifications were added to the FAS for flight three. When the FAS underwent ground tests, it also latched up. The failure indicated that each computer board had a different tolerance to electronic noise. The problem with the FAS was corrected. Subsequently, another failure occurred, raising questions about the design, and the probability of failure for the X-43 Mach 10 flight. This was not simply a technical issue, but illuminated the difficulties facing both managers and engineers in assessing risk, design requirements, and probabilities in cutting edge aerospace projects.

Peebles, Curtis↗
NASA NTRS1991

Slope-aspect color shading for parametric surfaces

The invention is a method for generating an image of a parametric surface, such as the compass direction toward which each surface element of terrain faces, commonly called the slope-aspect azimuth of the surface element. The method maximizes color contrast to permit easy discrimination of the magnitude, ranges, intervals or classes of a surface parameter while making it easy for the user to visualize the form of the surface, such as a landscape. The four pole colors of the opponent process color theory are utilized to represent intervals or classes at 90 degree angles. The color perceived as having maximum measured luminance is selected to portray the color having an azimuth of an assumed light source and the color showing minimum measured luminance portrays the diametrically opposite azimuth. The 90 degree intermediate azimuths are portrayed by unique colors of intermediate measured luminance, such as red and green. Colors between these four pole colors are used which are perceived as mixtures or combinations of their bounding colors and are arranged progressively between their bounding colors to have perceived proportional mixtures of the bounding colors which are proportional to the interval's angular distance from its bounding colors.

Moellering, Harold J.↗
NASA NTRS2008

In the Shade of Affluence: The Inequitable Distribution of the Urban Heat Island

The urban heat island is an unintended consequence of humans building upon rural and native landscapes. We hypothesized that variations in vegetation and land use patterns across an urbanizing regional landscape would produce a temperature distribution that was spatially heterogeneous and correlated with the social characteristics of urban neighborhoods. Using biophysical and social data scaled to conform to US census geography, we found that affluent whites were more likely to live in vegetated and less climatically stressed neighborhoods likely to live in than low-income Latinos in Phoenix, Arizona. Affluent neighborhoods had cooler summer temperatures that reduced exposure to outdoor heat-related health risks, especially during a heat wave period. In addition to being warmer, poorer neighborhoods lacked critical resources in their physical and social environments to help them cope with extreme heat. Increased average temperatures due to climate change are expected to exacerbate the impacts of urban heat islands.

Harlan, Sharon L.↗
NASA NTRS2020

150 Shades of Green: Using the Full Spectrum of Remote Sensing Reflectance to Elucidate Color Shifts in the Ocean

This article proposes a simple and intuitive classification system by which to define full spectral remote sensing reflectance (Rrs(λ)) data with a quantitative output that enables a more manageable handling of spectral information for aquatic science applications. The weighted harmonic mean of the Rrs(λ) wavelengths outputs an Apparent Visible Wavelength (in units of nanometers), representing a one-dimensional geophysical metric of color that is inherently correlated to spectral shape. This dimensionality reduction of spectral information combined with the output along a continuum of wavelength values offers a robust and user-friendly means to describe and analyze spectral Rrs(λ) in terms of spatial and temporal trends and variability. The uncertainty in the algorithm's estimation of spectral shape is demonstrated on a global scale, in addition to the utility of the algorithm to discern spectral-spatial-temporal trends in the ocean, on a per-pixel basis for the entire 22 year continuous ocean color (SeaWiFS and MODIS-Aqua) time-series. This technique can be applied to datasets of varying multi- and hyper-spectral resolutions, providing continuity between heritage and future satellite sensors, and further enabling an effective means of elucidating similarities or differences in complex spectral signatures within the constraints of two dimensions. This straightforward means of conceptualizing multi-dimensional variability can help maximize the potential of the spectral information embedded in remote sensing data.

ocean color↗
NASA NTRS2017

Fabrication of coronagraph masks and laboratory scale star-shade masks: characteristics, defects and performance

NASA WFIRST mission has planned to include a coronagraph instrument to find and characterize exoplanets. Masks are needed to suppress the host star light to better than 10-8 – 10-9 level contrast over a broad bandwidth to enable the coronagraph mission objectives. Such masks for high contrast coronagraphic imaging require various fabrication technologies to meet a wide range of specifications, including precise shapes, micron scale island features, ultra-low reflectivity regions, uniformity, wave front quality, etc. We present the technologies employed at JPL to produce these pupil plane and image plane coronagraph masks, and lab-scale external occulter masks, highlighting accomplishments from the high contrast imaging testbed (HCIT) at JPL and from the high contrast imaging lab (HCIL) at Princeton University. Inherent systematic and random errors in fabrication and their impact on coronagraph performance are discussed with model predictions and measurements.

Casey Wilson, Robert↗
NASA NTRS2021

A Dusty Veil Shading Betelgeuse During Its Great Dimming

Red supergiants are the most common final evolutionary stage of stars that have initial masses between 8 and 35 times that of the Sun. During this stage, which lasts roughly 100,000 years, red supergiants experience substantial mass loss. However, the mechanism for this mass loss is unknown. Mass loss may affect the evolutionary path, collapse and future supernova light curve of a red supergiant, and its ultimate fate as either a neutron star or a black hole. From November 2019 to March 2020, Betelgeuse—the second-closest red supergiant to Earth (roughly 220 parsecs, or 724 light years, away)—experienced a historic dimming of its visible brightness. Usually having an apparent magnitude between 0.1 and 1.0, its visual brightness decreased to 1.614 ± 0.008 magnitudes around 7–13 February 2020—an event referred to as Betelgeuse’s Great Dimming. Here we report high-angular-resolution observations showing that the southern hemisphere of Betelgeuse was ten times darker than usual in the visible spectrum during its Great Dimming. Observations and modelling support a scenario in which a dust clump formed recently in the vicinity of the star, owing to a local temperature decrease in a cool patch that appeared on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. Our findings suggest that a component of mass loss from red supergiants is inhomogeneous, linked to a very contrasted and rapidly changing photosphere.

Time-domain astronomy↗
DOE OSTI2024

Shading and Energy Impacts for Farmer-Friendly Agrivoltaics Arrays

When designing agrivoltaic solar arrays, farmers’ natural row tilling directions might be reasonable choices for array alignment, especially in cases where the tilling direction helps prevent soil erosion or has other benefits for the farmer’s operations. We examined the light field and energy production effects when installing arrays that have azimuth values that deviate from the typical ideal for three important array types: fixed-tilt, single-axis tracking, and vertical bifacial arrays. On a fractional annual energy production basis, though, all three array types lose very little output when rotated away from their ideal. This offers farmers and solar developers a wider range of system design to possibly align solar array rows with the farmer’s preferred tilling directions.

14 SOLAR ENERGY↗
DOE OSTI2015

Control algorithms for dynamic windows for residential buildings

This study analyzes the influence of control algorithms for dynamic windows on energy consumption, number of hours of retracted shades during daylight and shade operations. Five different control algorithms - heating/cooling, simple rules, perfect citizen, heat flow and predictive weather were developed and compared. The performance of a typical residential building was modeled with EnergyPlus. The program Widow was used to generate a Bi-Directional Distribution Function (BSDF) for two window configurations. The BSDF was exported to EnergyPlus using the IDF file format. The EMS feature in EnergyPlus was used to develop custom control algorithms. The calculations were made for four locations with diverse climate. The results showed that: (a) use of automated shading with proposed control algorithms can reduce the site energy in the range of 11.6-13.0%; in regard to source (primary) energy in the range of 20.1-21.6%, (b) the differences between algorithms in regard to energy savings are not high, (c) the differences between algorithms in regard to number of hours of retracted shades are visible, (e) the control algorithms have a strong influence on shade operation and oscillation of shade can occur, (d) additional energy consumption caused by motor, sensors and a small microprocessor in the analyzed case is very small.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2012

Evaluation of metal artifacts in MVCT systems using a model based correction method

Purpose: To evaluate the performance of a model based image reconstruction method in reducing metal artifacts in the megavoltage computed tomography (MVCT) images of a phantom representing bilateral hip prostheses and to compare with the filtered-backprojection (FBP) technique. Methods: An iterative maximum likelihood polychromatic algorithm for CT (IMPACT) is used with an additional model for the pair/triplet production process and the energy dependent response of the detectors. The beam spectra for an in-house bench-top and TomoTherapy Trade-Mark-Sign MVCTs are modeled for use in IMPACT. The empirical energy dependent response of detectors is calculated using a constrained optimization technique that predicts the measured attenuation of the beam by various thicknesses (0-24 cm) of solid water slabs. A cylindrical (19.1 cm diameter) plexiglass phantom containing various cylindrical inserts of relative electron densities 0.295-1.695 positioned between two steel rods (2.7 cm diameter) is scanned in the bench-top MVCT that utilizes the bremsstrahlung radiation from a 6 MeV electron beam passed through 4 cm solid water on the Varian Clinac 2300C and in the imaging beam of the TomoTherapy Trade-Mark-Sign MVCT. The FBP technique in bench-top MVCT reconstructs images from raw signal normalized to air scan and corrected for beam hardening using a uniform plexiglass cylinder (20 cm diameter). The IMPACT starts with a FBP reconstructed seed image and reconstructs the final image in 150 iterations. Results: In both MVCTs, FBP produces visible dark shading in the image connecting the steel rods. In the IMPACT reconstructed images this shading is nearly removed and the uniform background is restored. The average attenuation coefficients of the inserts and the background are very close to the corresponding values in the absence of the steel inserts. In the FBP images of the bench-top MVCT, the shading causes 4%-9.5% underestimation of electron density at the central inserts with an average of (6.3 {+-} 1.8)% for the range of electron densities studied. In the uniform plexiglass background, the shadow creates 0.8%-4.7% underestimation of electron density with an average of (2.9 {+-} 1.2)%. In the corresponding IMPACT images, the underestimation in the shaded plexiglass background is 0.3%-1.8% with an average of (0.9 {+-} 0.5)% and 1.4%-6.8% with an average of (2.8 {+-} 2.7)% in the central insert region. In the FBP images of the TomoTherapy Trade-Mark-Sign MVCT, this shading creates 2.6%-6.7% underestimation of electron density with an average of (3.7 {+-} 1.4)% at the central inserts and 5.9%-7.2% underestimation in the background with an average of (6.4 {+-} 0.5)%. In the IMPACT images, the uniform background between the steel rods is restored with 0.3%-1.0% underestimation of electron density with an average of (0.7 {+-} 0.3)%. The corresponding underestimation at the central inserts of the IMPACT images is -0.4%-0.1% with an average of (-0.1 {+-} 0.2)%. Conclusions: The shading metal artifact has been nearly removed in MVCT images using the IMPACT algorithm with the accurate geometry of the system, proper modeling of energy dependent response of detectors, and all relevant photon interaction processes. This results less than 1% difference in electron density in the background plexiglass and less than 3% averaged over the range of electron densities investigated.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Penumbra: A spatially distributed, mechanistic model for simulating ground-level incident solar energy across heterogeneous landscapes

Landscape solar energy is a significant environmental driver, yet it remains complicated to model well. Several solar radiation models simplify the complexity of light by estimating it at discrete point locations or by averaging values over larger areas. These modeling approaches may be useful in certain cases, but they are unable to provide spatially distributed and temporally dynamic representations of solar energy across entire landscapes. We created a landscape-scale ground-level shade and solar energy model called Penumbra to address this deficiency. Penumbra simulates spatially distributed ground-level shade and incident solar energy at user-defined timescales by modeling local and distant topographic shading and vegetative shading. Spatially resolved inputs of a digital elevation model, a normalized digital surface model, and landscape object transmittance are used to estimate spatial variations in solar energy at user-defined temporal timesteps. The research goals for Penumbra included: 1) simulations of spatiotemporal variations of shade and solar energy caused by both objects and topographic features, 2) minimal user burden and parameterization, 3) flexible user defined temporal parameters, and 4) flexible external model coupling. We test Penumbra’s predictive skill by comparing the model’s predictions with monitored open and forested sites, and achieve calibrated mean errors ranging from -17.3 to 148.1 μmoles/m 2 /s. Penumbra is a dynamic model that can produce spatial and temporal representations of shade percentage and ground-level solar energy. Outputs from Penumbra can be used with other ecological models to better understand the health and resilience of aquatic, near stream terrestrial, and upland ecosystems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Heat Island Mitigation Assessment and Policy Development for the Kansas City Region

Lawrence Berkeley National Laboratory partnered with Mid-America Regional Council (MARC) to quantify the costs and benefits from the adoption of urban heat island (UHI) countermeasures in the Kansas City region (population 1.5 million), and identify the best regional implementation pathway for MARC. The team selected cool (high-albedo) roofs and increased vegetation as the two countermeasures to evaluate. For vegetation, there were two strategies: (1) planting new trees to shade building surfaces, and (2) increasing urban irrigation (a surrogate for the use of vegetation to manage stormwater) to increase evapotranspiration. Using the Weather Research and Forecasting (WRF) model we simulated selected weeks during summer time, across five years (2011 2015) representing a range of normal summer conditions. We also simulated six of the most intense heatwaves that occurred between 2004 and 2016. We found under typical summer conditions (non-heatwave) average daytime (07:00 19:00 local standard time) regional near-ground air temperature reductions of 0.08 and 0.28 C for cool roofs and urban irrigation, respectively. We calculated the building electricity, electricity cost, and emission savings that result from the reduction in outdoor air temperature (indirect savings) and found maximum regional annual indirect electricity savings of 42.8 GWh for cool roofs and 85.6 GWh for urban irrigation-yielding maximum regional annual indirect electricity cost savings of $\$ $5.6M ($\$ $0.05/m 2 roof) and $\$ $11.1M ($0.01/m 2 irrigated land), respectively, and maximum regional annual CO 2 savings of 43.4 kt and 80 kt, respectively. We next evaluated the building energy, energy cost, and emission savings from reducing direct absorbed radiation on the building surfaces using cool roofs and shade trees (direct savings). For cool roofs, we found regional annual direct energy cost savings of $\$ $10.9M ($\$ $0.15/m 2 roof) with regional annual CO 2 savings of 66.4 kt. For shade trees, the regional annual direct energy cost savings were $\$ $21M ($\$ $21/tree) with regional annual CO 2 savings of 126 kt. We investigated cool roof cost premiums (the additional cost for selecting a cool roof product in lieu of a conventional roof product, estimated to be zero to $\$ $2.15/m 2 ) and shade tree first costs (assumed to be $\$ $100 per tree). The regional cool roof cost premium was calculated using the regional roof area per roofing material type and the range of cool roof product premiums for each material type. The extra cost of selecting cool roofs across the region ranged from $\$ $4.33M to $\$ $87.1M, while the additional shade trees planted across the region were assumed to cost $\$ $102M. When we compared the regional annual direct cost savings to the regional cool-roof cost premium and the regional shade-tree first cost, we found regional simple payback times up to 8.0 years for cool roofs and 4.9 years for trees, respectively. Since this comprehensive assessment of UHI countermeasures is a valuable methodology for other local governments to apply, we developed a step-by-step guide for others to follow. Based on the benefits and costs of the UHI countermeasures, MARC will pursue the inclusion of these countermeasures in existing regional plans where they can complement other regional priorities for transportation, climate resiliency, clean air, and hazard mitigation. They hosted a local workshop in 2016 for stakeholders to introduce the topic and will continue to share these resources to further appropriate adoption of UHI countermeasures.

urban climate↗