An acoustic evaluation of circumferentially segmented duct liners
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Watson, W. R.↗
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Results for “Segments”
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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Core segment 15008: Regolith stratigraphy at Apennine Front Station 2 using multispectral imaging
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Pieters, C. M.↗
Radiofrequency testing of satellite segment of simulated 30/20 GHz satellite communications system
A laboratory communications system has been developed that can serve as a test bed for the evaluation of advanced microwave (30/20 GHz) components produced under NASA technology programs. The system will ultimately permit the transmission of a stream of high-rate (220 Mbps) digital data from the originating user, through a ground terminal, through a hardware-simulated satellite, to a receiving ground station, to the receiving user. This report contains the results of radiofrequency testing of the satellite portion of that system. Data presented include output spurious responses, attainable signal-to-noise ratios, a baseline power budget, usable frequency bands, phase and amplitude response data for each of the frequency bands, and the effects of power level variation.
Leonard, R. F.↗
Segmented tubular cushion springs and spring assembly
A spring which includes a tube with an elliptical cross section, with the greater axial dimension extending laterally and the lesser axial dimension extending vertically is disclosed. A plurality of cuts in the form of slots passing through most of a wall of the tube extend perpendiculary to a longitudinal axis extending along the tube. An uncut portion of the tube wall extends along the tube for bonding or fastening the tube to a suitable base, such as a bottom of a seat cushion.
Haslim, L. A.↗
On an algorithm for analysis of the radiation patterns of dual reflector and segmented reflector antennas
An algorithm has been developed to calculate the radiation patterns of a large reflector antenna for space applications. The algorithm treats each panel in the reflector array as an analytic surface having n-sided polygonal boundaries. The radiation fields for individual panels are computed and stored separately, and then added to yield a uniform radiation pattern for the entire reflector. Numerical methods developed to reduce the overlap of the aperture fields of adjacent panels are described in detail. Calculations of the tangential field components of the aperture plane are carried out based on the principles of geometric optics (GO). Some radiation patterns calculated with the algorithm are compared with patterns produced by other methods, together with measured data for a classical Cassegrain antenna and the calculated patterns are illustrated.
Christodoulou, C. G.↗
Refining image segmentation by polygon skeletonization
A skeletonization algorithm was encoded and applied to a test data set of land-use polygons taken from a USGS digital land use dataset at 1:250,000. The distance transform produced by this method was instrumental in the description of the shape, size, and level of generalization of the outlines of the polygons. A comparison of the topology of skeletons for forested wetlands and lakes indicated that some distinction based solely upon the shape properties of the areas is possible, and may be of use in an intelligent automated land cover classification system.
Clarke, Keith C.↗
Pactruss support structure for precision segmented reflectors
The application of the Pactruss deployable structure to the support of large paraboloidal reflectors of very high precision was studied. The Pactruss concept, originally conceived for the Space Station truss, is shown to be suitable for use in a triangular arrangement to support a reflector surface composed of hexagonal reflector panels. A hybrid of Pactruss structural and deployable single-fold beams is shown to accommodate a center body. A minor alteration in the geometry is in order to avoid lockup during deployment. To assess the capability of the hybrid Pactruss structure, an example truss supporting a full-scale (20 meter diameter) infrared telescope was analyzed for static and dynamic performance. A truss structure weighing 800 kilograms gave adequate support to a reflector surface weighing 3,000 kilograms.
Hedgepeth, John M.↗
Verification of spatial and temporal pressure distributions in segmented solid rocket motors
A wide variety of analytical tools are in use today to predict the history and spatial distributions of pressure in the combustion chambers of solid rocket motors (SRMs). Experimental and analytical methods are presented here that allow the verification of many of these predictions. These methods are applied to the redesigned space shuttle booster (RSRM). Girth strain-gage data is compared to the predictions of various one-dimensional quasisteady analyses in order to verify the axial drop in motor static pressure during ignition transients as well as quasisteady motor operation. The results of previous modeling of radial flows in the bore, slots, and around grain overhangs are supported by approximate analytical and empirical techniques presented here. The predictions of circumferential flows induced by inhibitor asymmetries, nozzle vectoring, and propellant slump are compared to each other and to subscale cold air and water tunnel measurements to ascertain their validity.
Salita, Mark↗
Temperature control in wafer-level testing of large multi-segment electromigration test structures
The paper describes two methods for maintaining a constant metallization temperature throughout a wafer-level isothermal electromigration test of large multisegment test structures where Joule-heating is high and chip to chuck thermal contact is poor. In the first method, an initial calibration of Joule heating versus metal temperature is carried out. During the isothermal electromigration test, the Joule heating is continuously monitored and the chuck temperature is adjusted based on the calibration results to maintain a constant metal temperature. In the second method, temperature sensors are fabricated on the chip and then the sensors are used to monitor the chip temperature directly. The chuck temperature is then adjusted as needed.
Zamani, Nasser↗
Structural stereo matching of Laplacian-of-Gaussian contour segments for 3D perception
The stereo correspondence problem is solved using Laplacian-of-Gaussian zero-crossing contours as a source of primitives for structural stereopsis, as opposed to traditional point-based algorithms. Up to 74 percent matching of candidate zero crossing points are being achieved on 240 x 246 images at small scales and large ranges of disparity, without coarse-to-fine tracking and without precise knowledge of the epipolar geometry. This approach should prove particularly useful in recovering the epipolar geometry automatically for stereo pairs for which it is unavailable a priori. Such situations occur in the extraction of terrain models from stereo aerial photographs.
Boyer, K. L.↗
Design and fabrication of an erectable truss for precision segmented reflector application
The design of a first generation, 4-meter-diameter, doubly-curved, tetrahedral support truss for precision parabolic reflector panels, incorporating joints specifically designed for on-orbit astronaut assembly, is presented. Operational and design features of the erectable joint are detailed. Methods used to achieve very accurate strut lengths are described. Initial static and dynamic truss test results are presented which demonstrate linear structural response and predictability. Truss surface accuracy, determined photogrammetrically, is shown to be within 0.003 inch (RMS) of design.
Bush, Harold G.↗
NASA's Precision Segmented Reflectors (PSR) project
The PSR project representing a step toward developing the technology base needed to support future advanced astrophysics missions is described. The project is focused on producing high precision lightweight panels, large structures with proven erectability and accuracy, and lightweight and low power controls capable of achieving a high degree control of accuracy. Panels of sizes from 0.4 to 0.9 meter are fabricated to verify various design concepts for improving panel surface accuracy; in particular, a 0.4 meter panel is fabricated and refinished to a high degree of accuracy.
Pawlik, E.↗
Space Station Freedom - Status of the U.S. segment
An overview of the Space Station Freedom program is given. The results of a technical audit of the U.S. program, and the reorganization taking place at NASA HQ are discussed. Some areas resolved in the past year such as the type of power to be delivered to each pressurized module and the definition of common payload interfaces within all modules are reviewed. The utility of the Space Station Freedom is emphasized.
Bartoe, John David F.↗
The MSAT-X MARECS B2 satellite experiment - Ground segment results
The results of a recently completed satellite experiment employing the JPL MSAT-X developed land-mobile satellite communication terminal are described. In this experiment, a full duplex 4800-b/s digital data and voice communication link was established through the INMARSAT Marecs B2 satellite between Atlantic City, New Jersey, and Southbury, Connecticut. A series of experiments was performed to characterize the terminal performance over this link. The basic experimental setup and the preliminary results of the speech and data experiments are presented. The satellite environment proved to be near to what was expected, and as a result the experimental results were very close to theory/simulation/laboratory experiments. It was found that the ground-to-ground communication links were more benign links than the ground-to-air and air-to-ground links, and this is reflected in the improved margins for the ground-to-ground links (approximately 5 dB versus 3.2 dB for the aeronautical links).
Jedrey, Thomas C.↗
Design and fabrication of an erectable truss for precision segmented reflector application
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Bush, Harold G.↗
Numerical Arc-Segmentation Algorithm For A Radio Conference
NASARC computer program developed from general planning principles and decisions of both sessions of World Administrative Radio Conference on Use of Geostationary Satellite Orbit and on Planning of Space Services Utilizing It (WARC-85 and WARC-88). Written to help countries satisfy requirements for nationwide fixed-satellite services from at least one orbital position within predetermined arc. Written in ANSI standard FORTRAN 77.
Whyte, W. A.↗
A Segmented Ion-Propulsion Engine
New design approach for high-power (100-kW class or greater) ion engines conceptually divides single engine into combination of smaller discharge chambers integrated to operate as single large engine. Analogous to multicylinder automobile engine, benefits include reduction in required accelerator system span-to-gap ratio for large-area engines, reduction in required hollow-cathode emission current, mitigation of plasma-uniformity problem, increased tolerance to accelerator system faults, and reduction in vacuum-system pumping speed.
Brophy, John R.↗
AFSCN command and control segment evolution
An overview is presented of the Air Force Satellite Control Network (AFSCN). The AFSCN is a worldwide network providing DOD satellite control capability including satellite tracking and commanding, telemetry data processing, and communications. The network elements are listed including test center, space operations center, tracking stations, and network engineering and system development. Space Systems Div. responsibilities are given along with A.F. Space Command and Logistics Command responsibilities.
Whipple, Larry K.↗