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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 1,297 records · Page 72
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NASA NTRS1985

Holographic interferometry applied to symmetric aerodynamic models in a wind tunnel

The technique of holographic interferometry provides a means for noninvasive measurement of the air density distribution in the flow field in the vicinity of an aerodynamic model. A test of the applicability of this technique was the objective of this investigation. A holographic interferometer was installed in the 2- by 2-Foot Transonic Wind Tunnel at Ames Research Center. Several tests were conducted with this system on two axisymmetric models, one at subsonic and the other at supersonic speeds. Holograms were made of the flow field around the model for several test conditions. These holograms were reconstructed into interferograms in the laboratory. The fringe distribution (a measure of local densities) from a number of interferograms was digitized for subsequent data reduction. A computer program based on the Fourier transform technique was developed to convert the fringe distribution into a three-dimensional distribution of air density around the model. These results will be presented in this paper.

Perry, R. L.↗
NASA NTRS1985

Model deformation measurements at a cryogenic wind tunnel using photogrammetry

A photogrammetric closed circuit television system to measure model deformation at the National Transonic Facility (NTF) is described. The photogrammetric approach was chosen because of its inherent rapid data recording of the entire object field. Video cameras are used to acquire data instead of film cameras due to the inaccessibility of cameras which must be housed within the cryogenic, high pressure plenum of this facility. Data reduction procedures and the results of tunnel tests at the NTF are presented.

Burner, A. W.↗
NASA NTRS1985

A new 3D LDV system for the NASA Ames 6 x 6 ft. wind tunnel

An obvious extension of wind tunnel laser Doppler velocimetry (LDV), which is currently mainly limited to two-component measurements, would involve the measurement of three simultaneous velocity components. The present paper is concerned with an approach to reduce the degree of optical complexity involved in the design of a three-dimensional (3D) LDV system, taking into account the use of polarization separation. Such a system, utilizing polarization as well as color separation, has been designed and tested in a 6 x 6 foot supersonic wind tunnel. The considered instrument was designed for the on line measurement of three mean velocity components, turbulence levels, and shear stresses on a number of models under a wide variety of test conditions. Attention is given to optical details, data reduction, and sample application.

Owen, F. K.↗
NASA NTRS1986

X-ray observations of the bright quasar survey

Using the Einstein Observatory, X-ray observations of about 80 percent of the quasars in the Bright Quasar Survey located outside the declination range defined by 30 and 60 deg. X-ray emission has been detected above the 3-sigma level for 57 out of 66 quasars observed. This paper describes observations and data reduction and provides a summary of the more detailed analyses and discussion contained in the two accompanying papers (Schmidt and Green 1986, Avni and Tananbaum 1986).

Tananbaum, H.↗
NASA NTRS1985

Prospects for astrometry with the Hubble Space Telescope

The Hubble Space Telescope (HST), a large optical telescope having an aperture of 2.4 meters and a length of 8.8 meters, is being developed by NASA. This telescope will be placed into earth orbit by the Space Shuttle. Astrometric observations with the HST are made using a Fine Guidance Sensor which is capable of measuring the position of one object relative to another with an accuracy of + or - 0.002 arcseconds. The astrometric user of HST will be provided with an Astrometric Data Reduction Software package. The variety of astrometric problems to be investigated with HST is discussed.

Jefferys, W. H.↗
NASA NTRS1986

Radar stereomapping techniques and application to SIR-B images of Mt. Shasta

One of the goals of the SIR-B experiment was the definition of optimum radar incidence and intersection angles for radargrammetric stereoscopy by comparing the results from three separate data-reduction methods. To this end three overlapping images of the prime radargrammetric site (Mt. Shasta in northern California) were obtained, fewer than anticipated. This paper describes the mathematical basis for radar stereomapping, along with preliminary results from one of the methods (using a so-called 'analytical' stereoplotter) for the Mt. Shasta site. Height coordinate errors range from 60 to 170 m depending on the density (number per ground area) of ground control points used.

Leberl, F. W.↗
NASA NTRS1985

Research in lightning swept-stroke attachment patterns and flight conditions with the NASA F-106B airplane

Data on 637 direct lightning strikes and 117 close flashes observed by the NASA instrumented F-106B aircraft as part of the Storm Hazards Program at NASA Langley during 1980-1984 are compiled and analyzed, updating the report of Fisher and Plumer (1983). The airborne and ground-based measurement and recording apparatus and the flight and data-reduction procedures are described, and the results are discussed in terms of lightning-strike-conducive flight conditions and lightning attachment patterns. A peak strike rate of 2.1/min is found at altitude 38,000-40,000 ft and temperature below -40 C, with very few strikes below 20,000 ft. Four categories of swept-flash attachment pattern are identified, but it is pointed out that all exterior surfaces of the F-106B are potential attachment sites.

Fisher, B. D.↗
NASA NTRS1986

Mode II interlaminar fracture of graphite/epoxy and graphite/PEEK

The end notched flexure (ENF) specimen is employed in an investigation of the interlaminar fracture toughness in Mode II (skew symmetric shear) loading of unidirectional graphite/epoxy and graphite/PEEK composites. Important experimental parameters such as the influence of precracking and the data reduction scheme for the Mode II toughness are discussed. Nonlinear load-deflection response is significant for the tough thermoplastic resin composite but is also present for the brittle thermoset composite. The observed nonlinearities, which are highly rate dependent, are attributed to a combination of slow stable crack growth preceding unstable crack growth and material inelastic behavior in the process zone around the crack tip.

Carlsson, L. A.↗
NASA NTRS1986

Comet P/Halley 1910, 1986: An objective-prism study

V. M. Slipher of the Lowell Obs. collected a large amount of spectroscopic data during the 1910 apparition of Halley's comet. Three of his post perihelion objective-prism plates were selected, digitized, and subjected to modern digital data reduction procedures. Some of the important steps in the analysis where: (1) Density to intensity conversion for which was used 1910 slit spectra of Fe-arc lamp on similar plates (Sigma) and derived an average characteristic curve; (2) Flux calibration using the fact that during the period June 2 to 7 1910 P/Halley was very close (angular distance) to the bright star Alpha Sex (A0III, V-4.49), and the spectra of both star and comet were recorded on the same plates. The flux distribution of Alpha Sex was assumed to be similar to that of the standard star 58 Aql and derived a sensitivity curve for the system; (3) Atmospheric extinction using the standard curve for the Lowell Obs.; (4) Solar continuum subtraction using the standard solar spectrum binned to the spectral resolution. An example of a flux-calibrated spectrum of the coma (integrated over 87,000km) before the subtraction of solar continuum is presented.

Carsenty, U.↗
NASA NTRS1987

Computations for the 16-foot transonic tunnel, NASA, Langley Research Center, revision 1

The equations used by the 16 foot transonic tunnel in the data reduction programs are presented in eight modules. Each module consists of equations necessary to achieve a specific purpose. These modules are categorized in the following groups: tunnel parameters; jet exhaust measurements; skin friction drag; balance loads and model attitudes calculations; internal drag (or exit-flow distributions); pressure coefficients and integrated forces; thrust removal options; and turboprop options. This document is a companion document to NASA TM-83186, A User's Guide to the Langley 16 Foot Transonic Tunnel, August 1981.

Mercer, Charles E.↗
NASA NTRS1986

Laser fringe anemometry for aero engine components

Advances in flow measurement techniques in turbomachinery continue to be paced by the need to obtain detailed data for use in validating numerical predictions of the flowfield and for use in the development of empirical models for those flow features which cannot be readily modelled numerically. The use of laser anemometry in turbomachinery research has grown over the last 14 years in response to these needs. Based on past applications and current developments, the key issues which are involved when considering the application of laser anemometry to the measurement of turbomachinery flowfields are discussed. Aspects of laser fringe anemometer optical design which are applicable to turbomachinery research are briefly reviewed. Application problems which are common to both laser fringe anemometry (LFA) and laser transit anemometry (LTA) such as seed particle injection, optical access to the flowfield, and measurement of rotor rotational position are covered. The efficiency of various data acquisition schemes is analyzed and issues related to data integrity and error estimation are addressed. Real-time data analysis techniques aimed at capturing flow physics in real time are discussed. Finally, data reduction and analysis techniques are discussed and illustrated using examples taken from several LFA turbomachinery applications.

Strazisar, Anthony J.↗
NASA NTRS1987

High resolution infrared spectroscopy from space: A preliminary report on the results of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment on Spacelab 3

The ATMOS (Atmospheric Trace Molecule Spectroscopy) experiment has the broad purpose of investigating the physical structure, chemistry, and dynamics of the upper atmosphere through the study of the distributions of the neutral minor and trace constituents and their seasonal and long-term variations. The technique used is high-resolution infrared absorption spectroscopy using the Sun as the radiation source, observing the changes in the transmission of the atmosphere as the line-of-sight from the Sun to the spacecraft penetrates the atmosphere close to the Earth's limb at sunrise and sunset. During these periods, interferograms are generated at the rate of one each second which yield, when transformed, high resolution spectra covering the 2.2 to 16 micron region of the infrared. Twenty such occultations were recorded during the Spacelab 3 flight, which have produced concentration profiles for a large number of minor and trace upper atmospheric species in both the Northern and Southern Hemispheres. Several of these species have not previously been observed in spectroscopic data. The data reduction and analysis procedures used following the flight are discussed; a number of examples of the spectra obtained are shown, and a bar graph of the species detected thus far in the analysis is given which shows the altitude ranges for which concentration profiles were retrieved.

Farmer, Crofton B.↗
NASA NTRS1987

Development of wind tunnel techniques for the solution of problems in planetary Aeolian processes

Kutzbach reports wind profiles over a series of roughness elements on a frozen lake and how the wind profile changed as the surface roughness was varied. The approach of the current study was to duplicate Kutzbach's roughness arrays in the wind tunnel at 1/20 and 1/40 scales, and to compare the wind profiles over these scale models to those derived by Kutzbach at full scale in the field. The effects of scale differences and data reduction techniques are discussed. Although the study suggests that wind tunnel scale models can predict parameters measured in the field, the development of more definitive guidelines requires a field experiment designed specifically for comparison with wind tunnel results.

Sullivan, Robert↗
NASA NTRS1987

Rare gas analysis of size fractions from the Fayetteville meteorite

Eight size separates of grains from the Fayetteville meteorite ranging from less than 20 microns to greater than 1 millimeter are being analyzed for their rare gas elemental and isotopic composition. Measurements on five samples were performed. All five reveal a mixture of solar, planetary, cosmic ray produced and radiogenic gases. The solar component is of particular interest since it suggest that the meteorite may represent a fragment of an ancient protoplanetary regolith which was exposed to the solar wind. Solar wind elements are implanted in the outer few hundred Angstroms of exposed grains and are therefore expected to be surface correlated. At present the data do not suggest that such a correlation exists, but the final conclusion must await further analyses and data reduction.

Jordan, Jim L.↗
NASA NTRS1987

HALOE test and evaluation software

Computer programming, system development and analysis efforts during this contract were carried out in support of the Halogen Occultation Experiment (HALOE) at NASA/Langley. Support in the major areas of data acquisition and monitoring, data reduction and system development are described along with a brief explanation of the HALOE project. Documented listings of major software are located in the appendix.

Edmonds, W.↗
NASA NTRS1987

Interlaminar shear fracture toughness and fatigue thresholds for composite materials

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

Obrien, T. Kevin↗
NASA NTRS1986

Data inversion algorithm development for the hologen occultation experiment

The successful retrieval of atmospheric parameters from radiometric measurement requires not only the ability to do ideal radiometric calculations, but also a detailed understanding of instrument characteristics. Therefore a considerable amount of time was spent in instrument characterization in the form of test data analysis and mathematical formulation. Analyses of solar-to-reference interference (electrical cross-talk), detector nonuniformity, instrument balance error, electronic filter time-constants and noise character were conducted. A second area of effort was the development of techniques for the ideal radiometric calculations required for the Halogen Occultation Experiment (HALOE) data reduction. The computer code for these calculations must be extremely complex and fast. A scheme for meeting these requirements was defined and the algorithms needed form implementation are currently under development. A third area of work included consulting on the implementation of the Emissivity Growth Approximation (EGA) method of absorption calculation into a HALOE broadband radiometer channel retrieval algorithm.

Gordley, Larry L.↗
NASA NTRS1985

Experimental techniques for three-axes load cells used at the National Full-Scale Aerodynamics Complex

The necessary information for an aerodynamic investigation requiring load cell force measurements at the National Full-Scale Aerodynamics Complex (NFAC) is provided. Included are details of the Ames 40x80 three component load cells; typical model/load cell installation geometries; transducer signal conditioning; a description of the Ames Standard Computations Wind Tunnel Data Reduction Program for Load Cells Forces and Moments (SCELLS), and the inputs required for SCELLS. The Outdoor Aerodynamic Facilities Complex (OARF), a facility within the NFAC where three axes load cells serve as the primary balance system, is used as an example for many of the techniques, but the information applies equally well to other static and wind tunnel facilities that make use of load cell balances.

Dudley, Michael R.↗