SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Techniques are presented for detecting and correcting errors in a vector field. These methods employ median filters which are frequently used in image processing to enhance edges and remove noise. A detailed example is given for wind field maps produced by a spaceborne scatterometer. The error detection and replacement algorithm was tested with simulation data from the NASA Scatterometer (NSCAT) project.
The fabrication of the first Z-technology module with 128 active layers of readout electronic circuitry is being pursued. Several issues which will be investigated regarding the 128-layer module build, such as photolithographic processing at the edge of the module (edge effects) and module buttability, are discussed in this paper. Other topics which are covered apply to future applications of fully populated HYMOSS modules. These topics include possible reductions of thermal mass for quick cool-down time applications and improvements of end-to-end yield for low-cost applications.
When an infinite plane layer of dust having a number-density profile normal to the plane is exposed to an ambient e(sup -), p(sup +) plasma, one can imagine the features of the charging process near the layer boundary. If the e(sup -), p(sup +) temperatures are equal, and the B field is normal to the dust layer, the controlling factor is the large electron relative to proton speeds. Since the collision rate between plasma particles of number density n and speed v and an uncharged dust grain of radius a is estimated as the product n v pi a(exp 2), electrons dominate the charging process. The outer edge of the layer charges negatively, setting up an electrical potential that inhibits penetration of electrons into the layer and at the same time accelerates protons inward. Interior to the outer negative region then, one would expect many energetic protons compared to a reduced number of electrons from the ambient plasma. Charge imbalances are bound to arise, but the details are not so easy to deduce from simple arguments. These details are the subject of the present study.
In order to better interpret gravimetric data from orbiters such as GRAIL and LRO to understand the subsurface composition and structure of the lunar crust, it is import to have a reliable database of the density and porosity of lunar materials. To this end, we have been surveying these physical properties in both lunar meteorites and Apollo lunar samples. To measure porosity, both grain density and bulk density are required. For bulk density, our group has historically utilized sub-mm bead immersion techniques extensively, though several factors have made this technique problematic for our work with Apollo samples. Samples allocated for measurement are often smaller than optimal for the technique, leading to large error bars. Also, for some samples we were required to use pure alumina beads instead of our usual glass beads. The alumina beads were subject to undesirable static effects, producing unreliable results. Other investigators have tested the use of 3d laser scanners on meteorites for measuring bulk volumes. Early work, though promising, was plagued with difficulties including poor response on dark or reflective surfaces, difficulty reproducing sharp edges, and large processing time for producing shape models. Due to progress in technology, however, laser scanners have improved considerably in recent years. We tested this technique on 27 lunar samples in the Apollo collection using a scanner at NASA Johnson Space Center. We found it to be reliable and more precise than beads, with the added benefit that it involves no direct contact with the sample, enabling the study of particularly friable samples for which bead immersion is not possible
Flame spread over solid fuels is a canonical problem in fire science, due to its direct implications on material flammability and importance in fire development. Flames in a microgravity environment can behave very differently than on Earth, posing additional risks for spaceflight life safety. Sub-atmospheric pressures in ground-based experiments have been proposed to approximately replicate the burning behavior of solid fuels in reduced gravity conditions because of similar effects on heat and mass transfer mechanisms from the flame to the solid. In opposed-flow flame spread, the solid fuel is heated by the flame ahead of its leading edge, and this process is strongly affected by the ambient conditions. In this work, we consider flames spreading over flat thin acrylic samples exposed to a forced flow of 20 cm/s, and pressures between 30 and 100 kPa. When radiation losses and chemical kinetic effects are neglected, experimental and theoretical results suggest an independence of the spread rate on pressure. However, the spread rate shows a decreasing trend with lower pressure in the range 30-60 kPa. The mass burning rate, calculated from the samples weight measured before and after the experiments, shows a similar trend. The flame length, on the other hand, shows a non-monotonic behavior, reaching a maximum at 60 kPa. Additionally, gas emissions measured during the experiments are used to estimate the heat release rate of the spreading flames. The comparison of the heat release rate obtained from the measured emissions and the estimated mass burning rates, suggests that chemical kinetics is not driving the decrease in flame spread observed at low pressures, whereas radiation losses could be responsible in analogy to what has been observed in micro and partial gravity studies. These results could provide more information to guide future Earth-based material flammability testing for spacecraft applications.
High-fidelity, time-dependent simulations of a Boeing-designed, transonic, truss-braced-wing aircraft in cruise (clean) and landing configurations are leveraged to generate synthetic microphone-phased-array data for airframe noise prediction and assessment. These data sets are used to compute source localization (beamform) maps to determine the location and strength of primary and secondary airframe noise sources associated with this unique configuration. The synthetic phased-array implementation mimics the setup of a flight test. As this study is ongoing, preliminary integrated far-field spectra for the cruise configuration obtained at multiple spatial resolutions revealed significant tonal content that lacked convergence with increased resolution. The origin of several of these tones and their unusual convergence behavior was traced to the larger-than-normal trailing-edge thickness of the “as-tested” cruise model being simulated. Reducing the trailing-edge thickness to more realistic values eliminated most of the tones at low to moderate frequencies and improved spectrum convergence significantly. Applying lessons learned from the cruise simulations, several modifications to the geometry of the landing configuration were made and are described in this work. Results from permeable and solid Ffowcs-Williams and Hawkings surfaces at two different spatial resolutions (coarse and medium) are used to illustrate the major noise sources and determine convergence of the CLEAN integrated noise levels for the entire aircraft as well as major subcomponents. We demonstrate that the low-frequency content of the far-field spectrum is dominated by noise generated from the main landing gear, while the medium- and high-frequency content is dominated by the wing-leading-edge Krueger flaps. Since analysis of the acoustic maps for the landing configuration revealed several clusters of multiple sources along the wing leading edge, “high resolution” processing of the array data was used to distinguish more accurately the locations of sources.
A system is described for automatic and semiautomatic tracking of objects on film or video tape which was developed to meet the needs of the microgravity combustion and fluid science experiments at NASA Lewis. The system consists of individual hardware parts working under computer control to achieve a high degree of automation. The most important hardware parts include 16 mm film projector, a lens system, a video camera, an S-VHS tapedeck, a frame grabber, and some storage and output devices. Both the projector and tapedeck have a computer interface enabling remote control. Tracking software was developed to control the overall operation. In the automatic mode, the main tracking program controls the projector or the tapedeck frame incrementation, grabs a frame, processes it, locates the edge of the objects being tracked, and stores the coordinates in a file. This process is performed repeatedly until the last frame is reached. Three representative applications are described. These applications represent typical uses and include tracking the propagation of a flame front, tracking the movement of a liquid-gas interface with extremely poor visibility, and characterizing a diffusion flame according to color and shape.
The soft X-ray band below ≈0.5 keV is expected to provide rich information on metallicity, temperature, and distribution of hot gas in our galaxy and the intergalactic medium. Resolving these densely spaced emission lines requires energy resolution on the order of 1--2 eV. The low count rates from diffuse astrophysical sources also necessitate large collection areas, particularly for a sounding rocket instrument with short exposure times and limited resources. This translates to large pixel sizes (about 1 mm 2 ) for a reasonable number of read-out channels. To achieve the required energy resolution with 200 nm thin Au absorbers (heat capacity C about 1 pJ/K), we are developing TES microcalorimeters with very high temperature sensitivity (αI), low enough current sensitivity (βI), and minimal excess noise (M). Out of the various fabrication approaches for the TES bilayer we have explored, the lift-off approach (as pioneered for Mo/Au TES by Joel Weber at NIST) so far is the simplest to execute. The simple square TES geometries we have tested to date show promising results for αI and βI. Measured complex impedance and noise for bare devices without absorbers are well described by two-body thermal models and their excess noise is found to be consistent with predictions for mixed-down Johnson noise by Wessels et al. More sensitive measurements with larger heat capacity are planned to accurately determine excess noise. In this paper, we give an overview of the process and summarize results of our detailed characterization measurements for thermal conductance G, αI, βI, and noise for several devices across a range of bias points.
An algorithm processes cloud-physics data gathered in situ by an aircraft, along with reflectivity data gathered by ground-based radar, to determine whether the aircraft is inside or outside a cloud at a given time. A cloud edge is deemed to be detected when the in/out state changes, subject to a hysteresis constraint. Such determinations are important in continuing research on relationships among lightning, electric charges in clouds, and decay of electric fields with distance from cloud edges.
Experiments show liquid-crystal light valve (LCLV) exhibits operating mode in which it enhances edges in images projected on it. Operates in edge-enhancing mode (or in combination of edge-enhancing and normal modes) by suitably adjusting bias voltage and frequency. Enhancement of edges one of most important preprocessing steps in optical pattern-recognition systems. Incorporated into image-processing system to enhance edges without introducing excessive optical noise.
A method of processing digital image data to detect edges includes the use of fuzzy reasoning. The method is completely adaptive and does not require any advance knowledge of an image. During initial processing of image data at a low level of abstraction, the nature of the data is indeterminate. Fuzzy reasoning is used in the present method because it affords an ability to construct useful abstractions from approximate, incomplete, and otherwise imperfect sets of data. Humans are able to make some sense of even unfamiliar objects that have imperfect high-level representations. It appears that to perceive unfamiliar objects or to perceive familiar objects in imperfect images, humans apply heuristic algorithms to understand the images
Standard image processing techniques are not applicable to radar images because of the coherent nature of the sensor. Therefore there is a need to develop preprocessing techniques for radar images which will then allow these standard methods to be applied. A random field model for radar image data is developed. This model describes the image data as the result of a multiplicative-convolved process. Standard techniques, those based on additive noise and homomorphic processing are not directly applicable to this class of sensor data. Therefore, a minimum mean square error (MMSE) filter was designed to treat this class of sensor data. The resulting filter was implemented in an adaptive format to account for changes in local statistics and edges. A radar image processing technique which provides the MMSE estimate inside homogeneous areas and tends to preserve edge structure was the result of this study. Digitally correlated Seasat-A synthetic aperture radar (SAR) imagery was used to test the technique.
High T_c edge-geometry SNS microbridges have been fabricated using ion-damaged YBa_2Cu_3O_(7-x) (YBCO) and a nonsuperconducting phase of YBCO (N-YBCO) as normal metals. Optimization of the ion milling process used for YBCO edge formation and cleaning has resulted in ion-damage barrier devices which exhibit I-V characteristics consistent with the Resistively-Shunted-Junction (RSJ) model, with typical current densities (J_c) of approximately 5 x 10^6 A/cm^2 at 4.2 K. Characterization of N-YBCO films suggests that N-YBCO is the orthorhombic YBCO phase with oxygen disorder suppressing T_c...
Airgap capacitor in deposition chamber is used to monitor deposition. Coating process is completely uniform over edges, points, and internal areas. Areas not requiring coating can be marked. Since deposition process is accomplished at or near room temperature, there is no risk of thermal damage to coated components. With control method, deposition material is fully utilized and no excess coating is necessary to insure protection of coated parts.
Freely suspended smectic films of sub-micrometer thickness and lateral extensions of several millimeters are used to study thermally driven convection and diffusion in the film plane. The experiments were performed during a six minute microgravity phase of a TEXUS suborbital rocket flight (Texus 52, launched April 27, 2015). The project served as a preliminary test for a planned ISS Experiment with liquid crystal films (OASIS), and in addition it provided new experimental data on smectic films exposed to in-plane thermal gradients.We find an attraction of the smectic material towards the cold edge of the film in a temperature gradient, similar to a Soret effect. This process is reversed when this edge is heated up again. Thermal convection driven by two thermocontacts in the film is practically absent, even at temperature gradients up to 10 Kmm, thermally driven convection sets in when the hot post reaches the transition temperature to the nematic phase.An additional experiment was performed under microgravity conditions to test the stability of liquid crystal bridges in different smectic phases.
Reinforced carbon-carbon material specimens were machined from 19 and 33 ply flat panels which were fabricated and processed in accordance with the specifications and procedures accepted for the fabrication and processing of the leading edge structural subsystem (LESS) elements for the space shuttle orbiter. The specimens were then baseline coated and tetraethyl orthosilicate impregnated, as applicable, in accordance with the procedures and requirements of the appropriate LESS production specifications. Three heater bars were ATJ graphite silicon carbide coated with the Vought 'pack cementation' coating process, and three were stackpole grade 2020 graphite silicon carbide coated with the chemical vapor deposition process utilized by Vought in coating the LESS shell development program entry heater elements. Nondestructive test results are reported.
Design work for a photovoltaic module, fabricated using single crystal silicon dendritic web sheet material, resulted in the identification of surface treatment to the module glass superstrate which improved module efficiencies. A final solar module environmental test, a simulated hailstone impact test, was conducted on full size module superstrates to verify that the module's tempered glass superstrate can withstand specified hailstone impacts near the corners and edges of the module. Process sequence design work on the metallization process selective, liquid dopant investigation, dry processing, and antireflective/photoresist application technique tasks, and optimum thickness for Ti/Pd are discussed. A noncontact cleaning method for raw web cleaning was identified and antireflective and photoresist coatings for the dendritic webs were selected. The design of a cell string conveyor, an interconnect feed system, rolling ultrasonic spot bonding heat, and the identification of the optimal commercially available programmable control system are also discussed. An economic analysis to assess cost goals of the process sequence is also given.
A review of visual recognition studies is used to define two levels of information requirements. These two levels are related to two primary subdivisions of the spatial frequency domain of images and reflect two distinct different physical properties of arbitrary scenes. In particular, pathologies in recognition due to cerebral dysfunction point to a more complete split into two major types of processing: high spatial frequency edge based recognition vs. low spatial frequency lightness (and color) based recognition. The former is more central and general while the latter is more specific and is necessary for certain special tasks. The two modes of recognition can also be distinguished on the basis of physical scene properties: the highly localized edges associated with reflectance and sharp topographic transitions vs. smooth topographic undulation. The extreme case of heavily abstracted images is pursued to gain an understanding of the minimal information required to support both modes of recognition. Here the intention is to define the semantic core of transmission. This central core of processing can then be fleshed out with additional image information and coding and rendering techniques.