SEARCH · Engineering Papers

Results for “Mask”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,531 records · Page 85

All sources NASA NTRS DOE OSTI

NASA NTRS1982

Space Construction Experiment Definition Study (SCEDS), part 2. Volume 2: Study results

The Space Construction Experiment (SCE) was defined for integration into the Space Shuttle. This included development of flight assignment data, revision and update of preliminary mission timelines and test plans, analysis of flight safety issues, and definition of ground operations scenarios. New requirements for the flight experiment and changes for a large space antenna feed mask test article were incorporated. The program plan and cost estimates were updated. Revised SCE structural dynamics characteristics were provided for simulation and analysis of experimental tests to define and verify control limits and interactions effects between the SCE and the Orbiter digital automatic pilot.

Source record↗

NASA NTRS1982

An experimental study of dynamic stall on advanced airfoil sections. Volume 1: Summary of the experiment

The static and dynamic characteristics of seven helicopter sections and a fixed-wing supercritical airfoil were investigated over a wide range of nominally two dimensional flow conditions, at Mach numbers up to 0.30 and Reynolds numbers up to 4 x 10 to the 6th power. Details of the experiment, estimates of measurement accuracy, and test conditions are described in this volume (the first of three volumes). Representative results are also presented and comparisons are made with data from other sources. The complete results for pressure distributions, forces, pitching moments, and boundary-layer separation and reattachment characteristics are available in graphical form in volumes 2 and 3. The results of the experiment show important differences between airfoils, which would otherwise tend to be masked by differences in wind tunnels, particularly in steady cases. All of the airfoils tested provide significant advantages over the conventional NACA 0012 profile. In general, however, the parameters of the unsteady motion appear to be more important than airfoil shape in determining the dynamic-stall airloads.

Mccroskey, W. J.↗

NASA NTRS1982

The Faint Object Camera

The Faint Object Camera fully exploits the spatial resolution capability of the Space Telescope on the very faintest detectable objects over a broad wavelength range. A full complement of filters, objective prisms and polarizers, a choice of coronograhic masks, and a variety of scan formats extend the scientific versatility of the direct imaging mode. In addition, the Faint Object Camera provides the unique facility of long-slit spectroscopy to Space Telescope observers.

Macchetto, F.↗

NASA NTRS1981

The use of intermolecular potential functions in fitting pressure induced spectra

An example is presented which demonstrates the importance of using physically realistic derivatives of the intermolecular potential when fitting pressure-induced spectra. The use of nonrealistic derivatives may mask second-order temperature effects in the theory. As the temperature decreases, the intermolecular potential may have an important angular dependence.

Goorvitch, D.↗

NASA NTRS1982

Mars residual north polar cap - Earth-based spectroscopic confirmation of water ice as a major constituent and evidence for hydrated minerals

A description is presented of new earth-based reflectance spectra of the Martian north residual polar cap. The spectra indicate that the composition is at least mostly water ice plus another component with a 'gray' reflectance. The other minerals in the ice cap appear to be hydrated. The data were obtained with a cooled circular variable filter spectrometer on February 20, 1978, using the 2.2-m telescope on Mauna Kea, Hawaii. It is pointed out that the identification of water ice in the north polar cap alone does not indicate that water makes up all or even most of the bulk of the cap. Kieffer (1970) has shown that a small amount of water will mask the spectral features of CO2.

Clark, R. N.↗

NASA NTRS1981

Wide field of view laser beacon system for three-dimensional aircraft position measurement

This paper presents a new wide field of view laser beacon system for measurement, in three dimensions, of aircraft or other remote objects. The system is developed for aircraft collision hazard warning independent of ground-based hardware, as well as for flight research, helicopter-assisted construction and rescue, and robotic manipulation applications. Accurate information describing the relative range, elevation, and azimuth of the aircraft are generated by the sweep of a low-power fan-shaped rotating laser beacon past an array of optical detectors. The system achieves a wide angle of acceptance of laser beacon light through use of compound parabolic concentrators, which collimate the light for spectral filtering to minimize solar interference. An on-board microprocessor system converts the pulse sequence to aircraft position in real time. System reliability and performance are enhanced through narrow pass filtering of the pulse signals, digital logic design to mask spurious signals, and adaptive modulation of trigger threshold levels.

Sweet, L. M.↗

NASA NTRS1982

Predicting radiation sensitivity of polymers

Recently two independent applications have emerged for highly radiation-sensitive polymers: as resists for production of microelectronic circuitry and as materials to record the tracks of energetic nuclear particles. The relief images used for masking in resist materials are generated by radiation-induced differential dissolution rates, whereas the techniques used in recording nuclear particle tracks employ differential etching processes, that is, development by a chemical etchant that actually degrades the polymer. It is found that the sensitivity of materials to these very different processes is related to their gamma-ray scission efficiency. This correlation provides a predictive capability.

Osullivan, D.↗

NASA NTRS1982

The solar wind interaction with Mars as seen by the Viking retarding potential analyzers

Both energy spectra and continuous monitoring periods of the total flux above 15 eV are available, from Viking retarding potential analyzer measurements of electron fluxes not exceeding 75 eV out to 16,000 km above the Mars surface. Although the mean electron current at energies above 15 eV increases monotonically by almost two orders of magnitude from 9000 to 700 km in Viking 1 data, no clear signature of the bow shock is seen. Total current wave power shows a peak near 1700 km altitude. It is suggested that there may be a highly turbulent shock structure masking a clear signature of the bow shock in the time-averaged data, and it is concluded that the interaction model consistent with the bow shock at 1700 km, together with ionosphere measurements, indicates a permanent magnetic field able to stand off the solar wind during the Viking 1 entry.

Cragin, B. L.↗

NASA NTRS1981

Chemical rings of lunar basins from orbital X-ray data

Chemical patterns related to basin structure have been observed in digital maps of Mg/Al, Mg/Si and Al/Si variations on the nearside lunar surface. A large part of the inner topographic ring of the Smythii basin is distinguishable chemically in the orbital X-ray data because it is more anorthositic than the surrounding soil. The correlations between the chemistry and morphology of the Symthii basin, supported by X-ray data at Langrenus crater, indicate that: (1) the chemical record of basin-formation in pre-Nectarian times persists in lunar soils despite continuous meteorite bombardment of the moon; (2) strata of contrasting chemistry were excavated on the western side of the Smythii basin, whereas the lithology east of the basin is homogeneous to the depths sampled; (3) the geochemical boundary between the provinces of the eastern near side and far side may represent only surficial differences; and (4) the extent of primary ejecta from the younger Crisium basin was insufficient to mask the chemical features created by the Smythii impact approximately one Crisium-basin diameter away.

Andre, C. G.↗

NASA NTRS1982

Lateral epitaxial overgowth of GaAs by organometallic chemical vapor deposition

Lateral epitaxial overgrowth of GaAs by organometallic chemical vapor deposition has been demonstrated. Pyrolytic decomposition of trimethylgallium and arsine, without the use of HCl, was used to deposit GaAs on substrates prepared by coating (110) GaAs wafers with SiO2, then using photolithography to open narrow stripes in the oxide. Lateral overgrowth was seeded by epitaxial deposits formed on the GaAs surfaces exposed by the stripe openings. The extent of lateral overgrowth was investigated as a function of stripe orientation and growth temperature. Ratios of lateral to vertical growth rates greater than five have been obtained. The lateral growth is due to surface-kinetic control for the two-dimensional growth geometry studied. A continuous epitaxial GaAs layer 3 microns thick has been grown over a patterned mask on a GaAs substrate and then cleaved from the substrate.

Gale, R. P.↗

NASA NTRS1983

Two-Degree-of-Freedom Mount System for Flutter Models

Flexible rods replace conventional bearing supports to minimize structural damping. Aerodynamic damping not masked by effects of mount system, making more accurate studies possible of how aerodynamic damping varies as flow over model changed. New system called PAPA.

Farmer, M. G.↗

NASA NTRS1982

Special report on the data collection programs for the ground based nitrogen washout experiment. Volume 1: User's guide

The Nitrogen Washout System measures nitrogen elimination on a breath basis from the body tissues of a subject breathing pure oxygen. The system serves as a prototype for a Space Shuttle Life Sciences experiment and in the Environmental Physiology Laboratory. Typically, a subject washes out body nitrogen for three hours while breathing oxygen from a mask enclosed in a positive-pressure oxygen tent. A nitrogen washout requires one test operator and the test subject. A DEC LSI-11/02 computer is used to (1) control and calibrate the mass spectrometer and Skylab spirometer, (2) gather and store experimental data and (3) provide limited real time analysis and more extensive post-experiment analysis. Five programs are used to gather and store the experimental data and perform all the real time control and analysis.

Bueker, P. A.↗

NASA NTRS1982

Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices

Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties.

Wood, V. E.↗

NASA NTRS1978

LANDSAT image differencing as an automated land cover change detection technique

Image differencing was investigated as a technique for use with LANDSAT digital data to delineate areas of land cover change in an urban environment. LANDSAT data collected in April 1973 and April 1975 for Austin, Texas, were geometrically corrected and precisely registered to United States Geological Survey 7.5-minute quadrangle maps. At each pixel location reflectance values for the corresponding bands were subtracted to produce four difference images. Areas of major reflectance differences are isolated by thresholding each of the difference images. The resulting images are combined to obtain an image data set to total change. These areas of reflectance differences were found, in general, to correspond to areas of land cover change. Information on areas of land cover change was incorporated into a procedure to mask out all nonchange areas and perform an unsupervised classification only for data in the change areas. This procedure identified three broad categories: (1) areas of high reflectance (construction or extractive), (2) changes in agricultural areas, and (3) areas of confusion between agricultural and other areas.

Stauffer, M. L.↗

NASA NTRS1981

The evaluation of alternate methodologies for land cover classification in an urbanizing area

The usefulness of LANDSAT in classifying land cover and in identifying and classifying land use change was investigated using an urbanizing area as the study area. The question of what was the best technique for classification was the primary focus of the study. The many computer-assisted techniques available to analyze LANDSAT data were evaluated. Techniques of statistical training (polygons from CRT, unsupervised clustering, polygons from digitizer and binary masks) were tested with minimum distance to the mean, maximum likelihood and canonical analysis with minimum distance to the mean classifiers. The twelve output images were compared to photointerpreted samples, ground verified samples and a current land use data base. Results indicate that for a reconnaissance inventory, the unsupervised training with canonical analysis-minimum distance classifier is the most efficient. If more detailed ground truth and ground verification is available, the polygons from the digitizer training with the canonical analysis minimum distance is more accurate.

Smekofski, R. M.↗

NASA NTRS1983

Study of the time evolution of the lithosphere

The behavior and mechanical properties of the lithosphere were studied. This is a prerequisite to an understanding of the mechanisms and processes that occur in the Earth's mantle, which are masked by the lithospere. Geoid heights derived from the GEOS-3 and SEASAT radar altimeters were used. The correlation between bathymetry and geoid heights gives information on the mechanical properties of the lithosphere, such as its thickness, which is related to the age of the lithospheric plate. By probing in several locations spanning various temporal situations, the time evolution of the lithospheric plates were retraced.

Roufosse, M. C.↗

NASA NTRS1982

Use of basaltic magmas to characterize processes in planetary interiors: A test case in the southwestern United States

Whether or not basaltic rocks can be used as mantle probes depends upon the degree to which their compositions reflect their source regions rather than their subsequent histories. Mantle heterogeneities in the central Arizona Transition Zone were studied, and the degree to which interaction with the crust has modified the lavas masking these original variations was examined. Basalts from a thick sequence of basaltic flows in the Hickey Formation and two younger flows were sampled in order to provide a time transgressive suite of rocks. These rocks were dated and an extensive set of analytical data is now available for them.

Wittke, J.↗

NASA NTRS1983

Endurance test of a 30-CM-diameter engineering model ion thruster. Task 12: Investigation of thin-film erosion monitors for ion thrusters

An investigation of short term measurement techniques for predicting the wearout of ion thrusters resulting from sputter erosion damage is described. The previously established laminar thin film techniques to provide high precision erosion rate data. However, the erosion rates obtained using this technique are generally substantially higher than those obtained during long term endurance tests (by virtue of the as deposited nature of the thin films), so that the results must be interpreted in a relative sense. Absolute measurements can be performed using a new masked substrate arrangement which was developed during this study. This new technique provides a means for estimating the lifetimes of critical discharge chamber components based on direct measurements of sputter erosion depths obtained during short duration (10 hour) tests. The method enables the effects on lifetime of thruster design and operating parameters to be inferred without the investment of the time and capital required to conduct long term (1000 hour) endurance tests. Results obtained using the direct measurement technique are shown to agree with sputter erosion depths calculated for the plasma conditions of the test and also with lifetest results. The direct measurement approach is shown to be applicable to both mercury and argon discharge plasma environments and should be useful in estimating the lifetimes of inert gas and extended performance mercury ion thrusters presently under development.

Beattie, J. R.↗