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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Construction concepts for precision segmented reflectors

Three construction concepts for deployable precision segmented reflectors are presented. The designs produce reflectors with very high surface accuracies and diameters three to five times the width of the launch vehicle shroud. Of primary importance is the reliability of both the deployment process and the reflector operation. This paper is conceptual in nature, and uses these criteria to present beneficial design concepts for deployable precision segmented reflectors.

Mikulas, Martin M., Jr.↗
NASA NTRS1992

Modeling and initialization of a segmented telescope

The closely integrated design effort entailed by such prospective NASA-JPL project hardware as the Large Deployable Reflector, encompassing controls, dynamics, structures, optics, and thermal considerations, has prompted the development of the Figure Control Simulation, or 'FCSim' simulation program. This code is presently demonstrated for the case of a 7-segment, 3.65-m diameter primary mirror designed for 100-800 micron wavelengths. The optical component of the analysis can handle multispectral images, extended sources, image smear due to structural jitter, and mirror segment surface irregularities.

Sirlin, Samuel W.↗
NASA NTRS1993

Internal vibrations of a molecule consisting of rigid segments. I - Non-interacting internal vibrations

For molecular crystals, a procedure is proposed for interpreting experimentally determined atomic mean square anisotropic displacement parameters (ADPs) in terms of the overall molecular vibration together with internal vibrations with the assumption that the molecule consists of a set of linked rigid segments. The internal librations (molecular torsional or bending modes) are described using the variable internal coordinates of the segmented body. With this procedure, the experimental ADPs obtained from crystal structure determinations involving six small molecules (sym-trinitrobenzene, adenosine, tetra-cyanoquinodimethane, benzamide, alpha-cyanoacetic acid hydrazide and N-acetyl-L-tryptophan methylamide) have been analyzed. As a consequence, vibrational corrections to the bond lengths and angles of the molecule are calculated as well as the frequencies and force constants for each internal torsional or bending vibration.

He, X. M.↗
NASA NTRS1992

Robustness of Spann-Wilson segmentation on SAR imagery

The performances of the Spann-Wilson algorithm on simulated synthetic aperture radar (SAR) images with varying degrees of speckle (one to four looks and varying amounts of white noise) is described. One hundred forty-eight test images are considered, of which the algorithm segmented most without any adjustment to the algorithm's parameters. The effect of speckle on fractal boundaries is studied. The effect of varying multiplicative and additive noise distributions for a fixed set of segmentation parameters is examined. The modified Spann-Wilson algorithm on four-look imagery is evaluated.

Daida, Jason M.↗
NASA NTRS1994

Laser Metrology System For A Segmented Telescope Reflector

Report describes proposed laser metrology system in far-infrared telescope with segmented primary reflector. Telescope to be flown in outer space and used to observe celestial objects. Laser metrology system mounted on structure that supported secondary telescope reflector and measures relative positions and alignments of segments of primary reflector. System used in pointing as well as in maintaining surface figure.

Lau, Kenneth H.↗
NASA NTRS1994

Unsupervised texture image segmentation by improved neural network ART2

We here propose a segmentation algorithm of texture image for a computer vision system on a space robot. An improved adaptive resonance theory (ART2) for analog input patterns is adapted to classify the image based on a set of texture image features extracted by a fast spatial gray level dependence method (SGLDM). The nonlinear thresholding functions in input layer of the neural network have been constructed by two parts: firstly, to reduce the effects of image noises on the features, a set of sigmoid functions is chosen depending on the types of the feature; secondly, to enhance the contrast of the features, we adopt fuzzy mapping functions. The cluster number in output layer can be increased by an autogrowing mechanism constantly when a new pattern happens. Experimental results and original or segmented pictures are shown, including the comparison between this approach and K-means algorithm. The system written in C language is performed on a SUN-4/330 sparc-station with an image board IT-150 and a CCD camera.

Wang, Zhiling↗
NASA NTRS1994

Design of ground segments for small satellites

New concepts must be implemented when designing a Ground Segment (GS) for small satellites to conform to their specific mission characteristics: low cost, one main instrument, spacecraft autonomy, optimized mission return, etc. This paper presents the key cost drivers of such ground segments, the main design features, and the comparison of various design options that can meet the user requirements.

Mace, Guy↗
NASA NTRS1995

Avionics architecture for the U.S. segment of the international space station alpha

The International Space Station Alpha (ISSA) is a joint project between the United States, European Space Agency, Japan, Canada and Russia to develop and fly a space station in the later part of the 1990s. The United States will be the largest hardware contributor to this project, and this paper will describe the avionics architecture for the U.S. provided pressurized modules and truss segments. The avionics contained within these U.S. modules and segments will perform many of the core engineering and payload support functions for the ISSA. These functions include: the command and data handling, communications and tracking, guidance navigation and control (in partnership with the Russian elements), and electrical power generation and distribution. This paper will describe the architecture of the avionics systems that will perform these core engineering avionics functions, as well as provide a discussion on the avionics necessary for the proper functioning of the core engineering avionics supported functions such as thermal control, life support, and mechanisms.

Smith, Joseph F.↗
NASA NTRS1997

Final Design and Integration of Micro-Chip Inductive Edge Sensors for the Seven Segment Demonstrator. Testing of Integrated Edge Sensors in Test Packages

The contractor attended the critical design review and evaluated the presentations of other team members and presented data on the inductive edge sensor. The prototype micro-chip inductive edge sensor was evaluated, and devices were found to have a number of characteristics which made them unsuitable for installation on the seven segment demonstrator. The amplifier bandwidth was too low, the output drive current was too small, and there is an interaction between the digital circuitry and the amplifier that causes the amplifier to stop functioning. Therefore, the inductive edge sensors were not installed on the seven segment demonstrator. The contractor has participated in instruction, problem analysis, and provided technical assistance to NASA and its contractors for the development of 8 hexagonal mirror faceplates with electronics and edge sensors.

Karpinsky, John↗
NASA NTRS1996

Systematic Underestimation of Earthquake Magnitudes from Large Intracontinental Reverse Faults: Historical Ruptures Break Across Segment Boundaries

Because most large-magnitude earthquakes along reverse faults have such irregular and complicated rupture patterns, reverse-fault segments defined on the basis of geometry alone may not be very useful for estimating sizes of future seismic sources. Most modern large ruptures of historical earthquakes generated by intracontinental reverse faults have involved geometrically complex rupture patterns. Ruptures across surficial discontinuities and complexities such as stepovers and cross-faults are common. Specifically, segment boundaries defined on the basis of discontinuities in surficial fault traces, pronounced changes in the geomorphology along strike, or the intersection of active faults commonly have not proven to be major impediments to rupture. Assuming that the seismic rupture will initiate and terminate at adjacent major geometric irregularities will commonly lead to underestimation of magnitudes of future large earthquakes.

Rubin, C. M.↗
NASA NTRS1989

Precision Segmented Reflectors (PSR)

Current Precision Segmented Reflectors (PSR) technology development is intended for LDR-like applications: (1) Large segmented reflector systems; (2) Lightweight composite panels at 3 micron root-mean-square (RMS); (3) Precision lightweight structure at 500 microns; (4) Active figure control at 1 micron RMS accuracy; and (5) 5 micron RMS overall surface accuracy. Development of PSR technologies to date has demonstrated the potential of: (1) Lightweight composite panels at 0.1 micron RMS via polishing and re-finishing; (2) Shape control of composite panels by imbedded actuators; (3) Precision lightweight structure at 100 microns or better; and (4) Smart structure strut that can suppress vibrations and change its length.

Lin, Richard Y.↗
NASA NTRS1999

Five-Segment Reusable Solid Rocket Booster Upgrade

The Five Segment Reusable Solid Rocket Booster (RSRB) feasibility status is presented in viewgraph form. The Five Segment Booster (FSB) objective is to provide a low cost, low risk approach to increase reliability and safety of the Shuttle system. Topics include: booster upgrade requirements; design summary; reliability issues; booster trajectories; launch site assessment; and enhanced abort modes.

Sauvageau, Don↗
NASA NTRS1999

Superpolishing and Precision Metrology on a Metal Mandrel and Replicated Segments for Constellation-X

We have superpolished a diamond-turned aluminum mandrel (coated with electroless Ni) to an axial roughness of 6.34 nm rms. The mandrel is made to the Astro-E secondary mirror design for the 81st shell. Precision metrology at 100 mm to submicron scales has established the power spectral density of the mandrel and ultralightweight gold coated replicated segments. Predicted image quality of a set of optimally aligned replicated segments of this and a matching primary is substantially improved as compared to the flight mirrors for Astro-E. This approach using metal mandrels, superpolishing, and replicated ultralightweight foil mirrors, may represent a cost-effective approach to meeting the 15 arcsec half-energy width and weight requirements for the Constellation-X mission. Descriptions of the polishing apparatus, the precision metrology instruments, and the surface data analysis are presented. The general methods described are applicable to precision optics for both normal incidence and grazing incidence optics.

Content, D.↗
NASA NTRS1999

Superpolishing and Precision Metrology on a Metal Mandrel and Replicated Segments for Constellation-X

We have superpolished a diamond-turned aluminum mandrel (coated with electroless Ni) to an axial roughness of 0.34 nm rms. The mandrel is made to the Astro-E secondary mirror design for the 81st shell. Precision metrology at 100 mm to submicron scales has established the power spectral density of the mandrel and ultralightweight gold coated replicated segments. Predicted image quality of a set of optimally aligned replicated segments of this and a matching primary is substantially improved as compared to the flight mirrors for Astro-E. This approach using metal mandrels, superpolishing, and replicated ultralightweight foil mirrors, may represent a cost-effective approach to meeting the 15 arcsec half-energy width and weight requirements for the Constellation-X mission. Descriptions of the polishing apparatus, the precision metrology instruments, and the surface data analysis are presented. The general methods described are applicable to precision optics for both normal incidence and grazing incidence optics.

Content, D.↗
NASA NTRS1999

Superpolishing and Precision Metrology on a Metal Mandrel and Replicated Segments for Constellation-X

We have superpolished a diamond-turned aluminum mandrel (coated with electroless Ni) to an axial roughness of 0.34 nm rms. The mandrel is made to the Astro-E secondary mirror design for the 81st shell. Precision metrology at 100 mm to submicron scales has established the power spectral density of the mandrel and ultralightweight gold coated replicated segments. Predicted image quality of a set of optimally aligned replicated segments of this and a matching primary is substantially improved as compared to the flight mirrors for Astro-E. This approach using metal mandrels, superpolishing, and replicated ultralightweight foil mirrors, may represent a cost-effective approach to meeting the 15 arcsec half-energy width and weight requirements for the Constellation-X mission. Descriptions of the polishing apparatus, the precision metrology instruments, and the surface data analysis are presented. The general methods described are applicable to precision optics for both normal incidence and grazing incidence optics.

Content, D.↗
NASA NTRS2000

Optical Design of Segmented Hexagon Array Solar Mirror

A segmented array of mirrors was designed for a solar concentrator test stand at MSFC for firing solar thermal propulsion engines. The 144 mirrors each have a spherical surface to approximate a parabolic concentrator when combined into the entire 18-foot diameter array. The mirror segments are aluminum hexagons that had the surface diamond turned and quartz coated. The array focuses sunlight reflected from a heliostat to a 4 inch diameter spot containing 10 kw of power at the 15-foot focal point. The derivation of the surface figure for the respective mirror elements is shown. The alignment process of the array is discussed and test results of the system's performance is given.

Huegele, Vince↗
NASA NTRS2001

Segmented Thermal Barrier Coating

An article coated with a thermal barrier coating system, and method for preparation of a coated article. The article has a macro-segmented thermal barrier coating due to the presence of a pattern of three-dimensional features. The features may be a series of raised ribs formed on the substrate surface and being spaced from 0.05 inches to 0.30 apart. The ribs have a width W ranging from 0.005 inches to 0.02 inches, and a height R ranging from 25% to 100% of the thickness of the barrier coating. Alternately, the features may be a similar pattern of grooves formed in the surface of the substrate. Other embodiments provide segmentation by grooves or ribs in the bond coat or alternately grooves formed in the thermal barrier layer.

James L Smialek↗