Holographic instrumentation applications
Investigating possibilities and limitations of applying holographic techniques to aerospace technology
Brown, R. M.↗
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Results for “limiting techniques”
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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The simulation of high pressure hydrogen/oxygen rocket engines.
Initial experiments have established the feasibility of using a backward running detonation wave in a shock tube to produce the correct enthalpy and chemistry of the simulated combustion chamber gases. This technique produces plume Reynolds numbers higher than those achievable by any other known technique. The practical pressure limitations are being explored and detailed surveys of both single and multiple engine plumes and impingement data on a cylindrical body are being obtained. Facility details to allow safe handling of the high pressure hydrogen and oxygen up to a design chamber pressure of 20,000 psi are described.
Hopkins, H.↗
Stratospheric aerosol layer detection.
The earth's daytime horizon was scanned on several occasions between 1963 and 1968. The limb was observed at six wavelengths in the ultraviolet and visible spectrum with a narrow field of view instrument on the X-15 aircraft. The inversion of such horizon observations to yield atmospheric density and the concentrations of ozone and aerosol extinctions is discussed. The most significant features of the X-15 data are effects attributed to stratospheric aerosols. Observations of both the 20-km aerosol layer and a layer at approximately 50 km are inferred from the data. Both layers apparently possess considerable variability. It is pointed out that the existence of substantial aerosol concentrations above 30 km is an important limitation of the nadir technique of determining ozone concentrations in which the earth's radiance is observed at ultraviolet wavelengths from a satellite.
Cunnold, D. M.↗
Variable conductance heat pipe technology
Research and development programs in variable conductance heat pipe technology were conducted. The treatment has been comprehensive, involving theoretical and/or experimental studies in hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, and materials compatibility, in addition to the principal subject of variable conductance control techniques. Efforts were not limited to analytical work and laboratory experimentation, but extended to the development, fabrication and test of spacecraft hardware, culminating in the successful flight of the Ames Heat Pipe Experiment on the OAO-C spacecraft.
Marcus, B. D.↗
Spectral interpolation - Zero fill or convolution
Zero fill, or augmentation by zeros, is a method used in conjunction with fast Fourier transforms to obtain spectral spacing at intervals closer than obtainable from the original input data set. In the present paper, an interpolation technique (interpolation by repetitive convolution) is proposed which yields values accurate enough for plotting purposes and which lie within the limits of calibration accuracies. The technique is shown to operate faster than zero fill, since fewer operations are required. The major advantages of interpolation by repetitive convolution are that efficient use of memory is possible (thus avoiding the difficulties encountered in decimation in time FFTs) and that is is easy to implement.
Forman, M. L.↗
Detection of upper atmospheric constituents using submillimeter wave /SMMW/ heterodyne radiometry
Submillimeter wave heterodyne radiometry has been applied to the detection and sounding of upper atmospheric constituents. The use of room-temperature Schottky-diode mixers for the receivers has yielded measurements of 70,000 K noise temperature. Coupling losses into the diode and matching of the IF output limit are observed to limit noise temperature. The technique is evaluated by calculating spectra with assumed temperature and constituent profiles. Vertical integrations are made with a multilayer atmosphere and the direct summation of absorption coefficients for the individual spectral lines is used. Results are presented for tangent path parameters for a mid-latitude summer model and the fractional parts of upper atmospheric constituents as a function of altitude.
Mcavoy, N.↗
Imaging radar observations of Askja Caldera, Iceland
A 'blind' test involving interpretation of computer-enhanced like- and cross-polarized radar images is used to evaluate the surface roughness of Askja Caldera, a large volcanic complex in central Iceland. The 'blind' test differs from earlier analyses of radar observations in that computer-processes images and both qualitative and quantitative analyses are used. Attention is given to photogeologic examination and subsequent survey-type field observations, along with aerial photography during the field trip. The results indicate that the 'blind' test of radar interpretation of the Askja volcanic area can be considered suitable within the framework of limitations of radar data considered explicitly from the onset. The limitations of the radar techniques can be eliminated by using oblique-viewing conditions to remove geometric distortions and slope effects.
Malin, M. C.↗
An efficient algorithm for numerical airfoil optimization
A new optimization algorithm is presented. The method is based on sequential application of a second-order Taylor's series approximation to the airfoil characteristics. Compared to previous methods, design efficiency improvements of more than a factor of 2 are demonstrated. If multiple optimizations are performed, the efficiency improvements are more dramatic due to the ability of the technique to utilize existing data. The method is demonstrated by application to subsonic and transonic airfoil design but is a general optimization technique and is not limited to a particular application or aerodynamic analysis.
Vanderplaats, G. N.↗
Photoemission measurements of interface barrier energies for tunnel oxides on silicon
Internal photoemission measurements of the Si/SiO2 and Al/SiO2 barrier heights on oxides of tunneling thickness (43-56 A) are compared with measurements on thick oxides (310 A and greater) and the barrier heights are found to be the same. The results suggest that substantially thinner oxides, grown by the same method, can be characterized by the same barrier heights. Limits to the experimental technique posed by photovoltaic and displacement currents, and transport of hot carriers in the tunnel oxide are discussed.
Dressendorfer, P. V.↗
Figure control of flexible structures - Optical surfaces of thin deformable primary mirrors
Application of a modal control design technique to achieve discrete control of distributed parameter systems is considered. Results are presented for application of the design technique to achieve diffraction limited performance from the primary mirror of a space telescope and to provide flutter suppression for an aircraft wing.
Creedon, J. F.↗
Limitations on the application of a ground-based spectral technique for determining rain forest leaf area index
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Holben, B. N.↗
The use of frequency methods in rotorcraft system identification
A new approach to model structure determination is examined. Flight data from the Rotor Systems Research Aircraft (RSRA) are transformed into the frequency domain and truncated to provide band limiting. The stepwise regression technique is then used to identify a quasistatic state-space model from the transformed data. The data processing requirements for both time domain and frequency domain identification are discussed and the results of the two techniques are compared.
Duval, R. W.↗
Accurate frequency and intensity measurements of the infrared spectra of atmospheric molecules
Various problems encountered and solutions found in infrared laboratory measurements on atmospheric molecules are discussed. The advantages and limitations of various measurement techniques and equipment are discussed, with emphasis placed on calibration techniques and measurement accuracy and precision. Frequency calibration aids are presented, including the current and planned tables of absorption frequency standards being developed by the Bureau of Standards for the calibration of high-resolution devices with an accuracy of + or - 3 MHz. It is noted that intensity measurements are highly susceptible to systematic errors and that great care must be taken to obtain accuracies better than + or - 10%. What is even more difficult is knowing the accuracy of a particular measurement. Recent work done on providing accurate intensity data are described.
Maki, A. G.↗
Iron and magnesium in the white dwarf GD 40 - A test of diffusion theory
An outstanding problem in interpreting the properties of white-dwarf stars is related to the understanding of the chemical abundances in their atmospheres. The hydrogen-rich white-dwarf stars have monoelemental atmospheres, with small quantities of helium and no heavier elements observed in most, possibly all, stars with visible H lines. The helium-rich stars are more complex, and the existence of metallic lines in many of their spectra is now well confirmed. The DB star GD 40 (Gr 384) is the hottest He-rich white-dwarf star to show metal lines, apart from the extremely hot objects, such as HZ 21 and HD 149499B. The present investigation is concerned with IUE spectra which have been obtained of the GD 40. It is found that the near-UV is marked by strong Mg II lines along with broad blends of Fe II lines. An analysis is conducted of the abundances of Fe and Mg at the surface of GD 40 using a limited spectrum-synthesis technique with the measured equivalent widths of the best Fe II features.
Shipman, H. L.↗
Turbulence characteristics of an axisymmetric reacting flow
Turbulent sudden expansion flows are of significant theoretical and practical importance. Such flows have been the subject of extensive analytical and experimental study for decades, but many issues are still unresolved. Detailed information on reacting sudden expansion flows is very limited, since suitable measurement techniques have only been available in recent years. The present study of reacting flow in an axisymmetric sudden expansion was initiated under NASA support in December 1983. It is an extension of a reacting flow program which has been carried out with Air Force support under Contract F33615-81-K-2003. Since the present effort has just begun, results are not yet available. Therefore a brief overview of results from the Air Force program will be presented to indicate the basis for the work to be carried out.
Gould, R. D.↗
Shuttle flight data analysis
As the STS moves into routine operations, the direction of the work is shifting to an in-depth assessment of performance and its impact on the design and development of a future generation of vehicles. Particular emphasis is placed on providing an accurate physical explanation of anomalies, assessing the quality of simulation provided by the ground test facilities utilized, understanding the ground to flight extrapolation procedures, and the limitations of theoretical prediction techniques. The results are expected to provide direction and focus for future research and technology programs to enable substantial technological improvements in the next generation vehicles. The recent approval of the Orbital Experiments (OEX) Program's Shuttle Infrared Leeside Temperature Sensing (SILTS), Shuttle Entry Air Data System (SEADS), and Shuttle Upper Atmospheric Mass Spectrometer (SUMS) experiments to be integrated for flight on OV-102 in late 1985 is a firm indication of a strong commitment to a continuing and vigorous program in shuttle flight data analysis.
Walberg, G. D.↗
The use of hot-wire anemometry in transonic periodic flow
The unsteady wake profiles of an airfoil with an oscillating flap were measured in the NASA Ames 11 x 11-foot transonic wind tunnel. Laser Doppler Velocimetry (LDV) and holography techniques were used in limited region where optical accessability is available. X-hot-film wire was used to measure the wake profiles in the complete region to obtain magnitude and direction of the flow. A thorough calibration was carried out to determine the sensitivity coefficients of the hot-wire in three different tunnels at transonic speeds. A calculation procedure is established to resolve the hot-wire signals at transonic speeds and applied in the measurements of steady and periodic wake profiles. The effect of flow incidence on the hot-wire signals is evaluated and incorporated in the analyses. Typical hot-wire results are compared with the results of LDV, holography and pitot-static tube embedded with Kulite transducers.
Bodapati, S.↗
Binding constants of phenylalanine for the four mononucleotides
Earlier work has shown that several properties of amino acids correlate directly with properties of their anticodonic nucleotides. Furthermore, in precipitation studies with thermal proteinoids and homopolyribonucleotides, an anticodonic preference was displayed between Lys-rich, Pro-rich and Gly-rich thermal proteinoids and their anticodonic polyribonucleotides. However, Phe-rich thermal proteinoid displayed a preference for its codonic nucleotide, poly U. This inconsistency seemed to be explained by a folding in of the hydrophobic residues of Phe causing the proteinoid to appear more hydrophilic. The present work used nuclear magnetic resonance techniques to resolve a limited question: to which of the four nucleotides does Phe bind most strongly? The results show quite clearly that Phe binds most strongly to its anticodonic nucleotide, AMP.
Khaled, M. A.↗