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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 253 records · Page 14

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NASA NTRS1999

Omniview motionless camera orientation system

A device for omnidirectional image viewing providing pan-and-tilt orientation, rotation, and magnification within a hemispherical field-of-view that utilizes no moving parts. The imaging device is based on the effect that the image from a fisheye lens, which produces a circular image of at entire hemispherical field-of-view, which can be mathematically corrected using high speed electronic circuitry. More specifically, an incoming fisheye image from any image acquisition source is captured in memory of the device, a transformation is performed for the viewing region of interest and viewing direction, and a corrected image is output as a video image signal for viewing, recording, or analysis. As a result, this device can accomplish the functions of pan, tilt, rotation, and zoom throughout a hemispherical field-of-view without the need for any mechanical mechanisms. The preferred embodiment of the image transformation device can provide corrected images at real-time rates, compatible with standard video equipment. The device can be used for any application where a conventional pan-and-tilt or orientation mechanism might be considered including inspection, monitoring, surveillance, and target acquisition.

Zimmermann, Steven D.↗

NASA NTRS1972

Effects of circular geometry in simulation of convection in rotating spacecraft tanks

For computational simulation of the convection and mixing of stratified fluid in a rotating tank (such as used in Apollo flights) with time-dependent rotation, the Navier-Stokes convection problem was formulated for a circular tank configuration. The final equations results from a general approximate theory for combined forced and contained natural convection in a time-dependent rotating system. The equations are cast in terms of vorticity and stream function in a form convenient for computation, with a transformed coordinate system, and appropriate boundary conditions are derived. Accurate representations for the cryogenic supercritical oxygen thermodynamic properties are used in the computations, and an efficient numerical finite difference scheme and computational method are employed.

Martin, E. D.↗

NASA NTRS1973

Hybrid-coordinate spacecraft dynamics using large-deformation modal coordinates

For a vehicle amenable to idealization as a set of n + 1 rigid bodies interconnected by n line hinges (implying tree topology), a set of minimum-dimension matrix equations of motion is recorded in terms of variables including the relative rotations of contiguous bodies. When a substructure or portion of the vehicle is subjected to large gross deformations but is restricted to 'small' strains or local deformations, the n-body model is (for sufficiently large n) assumed to experience 'small' relative rotations of contiguous bodies within the substructure, and the equations of motion are linearized in these variables. The application of coordinate transformations and truncations to the linearized subset of the system equations of motion then produces a hybrid-coordinate formulation of the problem involving both discrete and distributed coordinates.

Likins, P. W.↗

NASA NTRS1978

Measurement and analysis of magnetic field variation during a class 2b flare

A digital analysis of high-time-resolution videomagnetograms taken during a class 2b flare that occurred at 60 deg east is reported. The data were obtained at the Big Bear Observatory and calibrated by a Mt. Wilson magnetogram. Changes of weak magnetic fields (less than 100 G) with an amplitude of 30% to 100% have been detected over 55% of the optical flare region, apparently taking place at the initial phase of the flare. Statistical considerations suggest a real flare association with most of these changes. H-alpha observations show that large changes took place over the footpoints of heavily inclined structures like penumbral fibrils, while smaller changes took place over the plage region. An apparent polarity reversal was found at the feet of erupted fibrils. Based on force-free field calculations these changes can be reasonably explained as a transformation of the current-carrying fields to potential fields which produced large changes in the field-line inclination and rotation.

Tanaka, K.↗

NASA NTRS1985

Line positions and strengths of CO2 in the 1200-1430/cm region

A study is reported in which the vibrational rotation spectrum of CO2 in the 1200-1430/cm region has been studied at a 0.005/cm resolution with a Fourier transform spectrometer. The positions and strengths of lines in the 10001-00001 bands of the species 628, 627, and 638 and the 11101-01101 and 11102-01101 bands of 628 have been measured and analyzed. Based on the results obtained, the band center frequencies, upper and lower state vibrational constants, band strengths, and coefficients in the F factor expression are determined.

Toth, R. A.↗

NASA NTRS1985

Some new results concerning the dynamic behavior of annular turbulent seals

The dynamic characteristics of annular turbulent seals applied in high pressure turbopumps can be described by stiffness, damping, and inertia coefficients. An improved procedure is presented for determining these parameters by using measurements made with newly developed test equipment. The dynamic system seal, consisting of the fluid between the cylindrical surfaces of the rotating shaft and the housing, is excited by test forces (input), and the relative motion between the surfaces (output) is measured. Transformation of the input and output time signals into the frequency domain leads to frequency response functions. An analytical model, depending on the seal parameters, is fitted to the measured data in order to identify the dynamic coefficients. Some new results are reported that show the dependencies of these coefficients with respect to the axial and radial Reynolds numbers and the geometrical data of the seal.

Massmann, H.↗

NASA NTRS1991

Measurement of the stratospheric hydrogen peroxide concentration profile using far infrared thermal emission spectroscopy

The first unequivocal measurement of hydrogen peroxide in the stratosphere have been made, a concentration profile obtained from a balloon platform using Fourier transform thermal emission spectroscopy in the far infrared. Measurements were made using the 112/cm R-Q5 branch of the rotational-torsional spectrum, with some confirmation from the 94/cm R-Q4 branch. The volume mixing ratio of H2O2 is 1.6 x 10 to the -10th at 38.4 km, decreasing to 0.6 x 10 to the -10th at 23.8 km, with uncertainties of about 16 percent. These measurements are compared to a recent stratospheric model calculation.

Chance, K. V.↗

NASA NTRS1995

A NASTRAN-based computer program for structural dynamic analysis of Horizontal Axis Wind Turbines

This paper describes a computer program developed for structural dynamic analysis of horizontal axis wind turbines (HAWT's). It is based on the finite element method through its reliance on NASTRAN for the development of mass, stiffness, and damping matrices of the tower end rotor, which are treated in NASTRAN as separate structures. The tower is modeled in a stationary frame and the rotor in one rotating at a constant angular velocity. The two structures are subsequently joined together (external to NASTRAN) using a time-dependent transformation consistent with the hub configuration. Aerodynamic loads are computed with an established flow model based on strip theory. Aeroelastic effects are included by incorporating the local velocity and twisting deformation of the blade in the load computation. The turbulent nature of the wind, both in space and time, is modeled by adding in stochastic wind increments. The resulting equations of motion are solved in the time domain using the implicit Newmark-Beta integrator. Preliminary comparisons with data from the Boeing/NASA MOD2 HAWT indicate that the code is capable of accurately and efficiently predicting the response of HAWT's driven by turbulent winds.

Lobitz, Don W.↗

NASA NTRS1984

The 12 micron band of ethane - High-resolution laboratory analysis with candidate lines for infrared heterodyne searches

Attention is given to the results of a laboratory study of the v9 band of ethane at 12 microns, using both high resolution Fourier transform and diode laser absorption spectroscopy. The analysis to which about 2000 transitions in this band have been subjected includes the normal rotational terms as well as the higher order effects of l-doubling, l-resonance, internal rotation, and a Coriolis resonance with the 3v4 state. A model is presented for the v9 band which is able to reproduce the observed features to an accuracy of better than 0.001/cm, and a list has been compiled for v9 transitions, occurring near C-14O2 laser lines, that are good candidates for laser heterodyne searches.

Atakan, A. K.↗

NASA NTRS1988

Hierarchical representation and machine learning from faulty jet engine behavioral examples to detect real time abnormal conditions

The theoretical basis and operation of LEBEX, a machine-learning system for jet-engine performance monitoring, are described. The behavior of the engine is modeled in terms of four parameters (the rotational speeds of the high- and low-speed sections and the exhaust and combustion temperatures), and parameter variations indicating malfunction are transformed into structural representations involving instances and events. LEBEX extracts descriptors from a set of training data on normal and faulty engines, represents them hierarchically in a knowledge base, and uses them to diagnose and predict faults on a real-time basis. Diagrams of the system architecture and printouts of typical results are shown.

Gupta, U. K.↗

NASA NTRS1992

Symmetry properties in polarimetric remote sensing

This paper presents the relations among polarimetric backscattering coefficients from the viewpoint of symmetry groups. Symmetry of geophysical media encountered in remote sensing due to reflection, rotation, azimuthal, and centrical symmetry groups is considered for both reciprocal and nonreciprocal cases. On the basis of the invariance under symmetry transformations in the linear polarization basis, the scattering coefficients are related by a set of equations which restrict the number of independent parameters in the polarimetric covariance matrix. The properties derived under these transformations are general and apply to all scattering mechanisms in a given symmetrical configuration. The scattering coefficients calculated from theoretical models for layer random media and rough surfaces are shown to obey the derived symmetry relations. Use of symmetry properties in remote sensing of structural and environmental responses of scattering media is discussed. As a practical application, the results from this paper provide new methods for the external calibration of polarimetric radars without the deployment of man-made calibration targets.

Nghiem, S. V.↗

NASA NTRS2004

More About the Phase-Synchronized Enhancement Method

A report presents further details regarding the subject matter of "Phase-Synchronized Enhancement Method for Engine Diagnostics" (MFS-26435), NASA Tech Briefs, Vol. 22, No. 1 (January 1998), page 54. To recapitulate: The phase-synchronized enhancement method (PSEM) involves the digital resampling of a quasi-periodic signal in synchronism with the instantaneous phase of one of its spectral components. This resampling transforms the quasi-periodic signal into a periodic one more amenable to analysis. It is particularly useful for diagnosis of a rotating machine through analysis of vibration spectra that include components at the fundamental and harmonics of a slightly fluctuating rotation frequency. The report discusses the machinery-signal-analysis problem, outlines the PSEM algorithms, presents the mathematical basis of the PSEM, and presents examples of application of the PSEM in some computational simulations.

Jong, Jen-Yi↗

NASA NTRS1988

Rotordynamic analysis of a bearing tester

The properties of the solutions of a system of four coupled nonlinear differential equations that model the behavior of the rotating shaft of a bearing tester are studied. In particular, it is shown how the bounds for the rotations of these equations can be obtained from bounds for the solutions of the linearized equations. By studying the behavior of the Fourier transforms of the solution, the approach to the stability boundary can also be predicted. These conclusions are verified by means of numerical solutions of the equations, and of power spectrum density (PSD) plots.

Zalik, Richard A.↗

NASA NTRS1999

Fourier Transform Ultraviolet Spectroscopy of the A Pi-2(3/2) Direct Current X Pi-2(3/2) Transition of BrO

The first spectra of the A (2)Pi(sub 3/2) from X (2)Pi(sub 3/2) electronic transition of BrO using Fourier transform ultraviolet spectroscopy are obtained. Broadband vibrational spectra acquired at 298 +/- 2 K and 228 +/- 5 K, as well as high-resolution rotational spectra of the A from X 7,0 and 12,0 vibrational bands are presented. Wavenumber positions for the spectra are obtained with high accuracy, and cross section assignments are made, incorporating the existing literature. With 35 cm(exp -1) (0.40 nm) resolution the absolute cross section at the peak of the 7,0 band is determined to be (1.58 +/- 0.12) x 10(exp -17) sq cm/molecule at 298 +/- 2 K and (1.97 +/- 0.15) x 10(exp -17) sq cm/molecule at 228 +/- 5 K. BrO dissociation energies are determined with a graphical Birge-Sponer technique, using Le Roy-Bernstein theory to place an upper limit on the extrapolation. From the ground-state dissociation energy, D(sub o)" = 231.0 +/- 1.7 kJ/mol, the heat of formation of BrO(g) is calculated, del(sub f)H(0 K) = 133.7 +/- 1.7 kJ/mol and del(sub f)H(298.15 K) = 126.2 +/- 1.7 kJ/mol. Cross sections for the high-resolution 7,0 and 12,0 rotational peaks are the first to be reported. The band structures are modeled, and improved band origins, rotational constants, centrifugal distortion constants, and linewidths are determined. In particular, J-dependent linewidths and lifetimes are observed for the both the 7,0 and 12,0 bands.

Wilmouth, David M.↗

NASA NTRS2009

Multispectrum Analysis of 12CH4 in the v4 Band: I. Air-Broadened Half Widths, Pressure-Induced Shifts, Temperature Dependences and Line Mixing

Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the v4 band of (CH4)-12 over the temperature range 210 to 314 K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006 to 0.01/cm) absorption spectra of pure methane and mixtures of methane diluted with dry air. Line mixing was detected for pairs of A-, E-, and F-species transitions in the P- and R-branch manifolds and quantified using the off-diagonal relaxation matrix elements formalism. The measured parameters are compared to air- and N2-broadened values reported in the literature for the v4 and other bands. The dependence of the various spectral line parameters upon the tetrahedral symmetry species and rotational quantum numbers of the transitions is discussed. All data used in the present work were recorded using the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak.

Smith, MaryAnn H.↗

NASA NTRS1976

A numerical comparison of discrete Kalman filtering algorithms - An orbit determination case study

An improved Kalman filter algorithm based on a modified Givens matrix triangularization technique is proposed for solving a nonstationary discrete-time linear filtering problem. The proposed U-D covariance factorization filter uses orthogonal transformation technique; measurement and time updating of the U-D factors involve separate application of Gentleman's fast square-root-free Givens rotations. Numerical stability and accuracy of the algorithm are compared with those of the conventional and stabilized Kalman filters and the Potter-Schmidt square-root filter, by applying these techniques to a realistic planetary navigation problem (orbit determination for the Saturn approach phase of the Mariner Jupiter-Saturn Mission, 1977). The new algorithm is shown to combine the numerical precision of square root filtering with the efficiency of the original Kalman algorithm.

Thornton, C. L.↗

NASA NTRS1978

DSPOBJ - System for display of multiple sets of three-dimensional data

DSPOBJ is a FORTRAN subroutine to control the display of three-dimensional line networks on a stand-alone, general-purpose, interactive computer graphics system. The program controls the creation and manipulation of transformation matrices for the display and control of multiple sets of line networks. It provides advanced graphics features such as independent and global scaling, rotation and translation, cross-sectioning, reflection, and simultaneous display of four views.

Ashbaugh, J. B.↗

NASA NTRS1980

A polarimeter for the high resolution ultraviolet spectrometer/polarimeter

The design requirements of the polarimeter were established by the scientific optical objectives of the experiment to be launched aboard the Solar Max Mission which will study active solar regions. The polarization of the light is accomplished by a rotating magnesium fluoride quarter wave plate. The quarter wave plates are rotated in 22 1/2 degree steps about an axis coincidental with the light beam. As the light beam passes through the wave plate, the transformation that occurs can be expressed by mathematical equations. By having the wave plates calibrated, the data obtained from solar flares can be analyzed and meaningful information provided to the investigators. The polarimeter has two wave plates with different optical characteristics to provide both redundancy and versatility. A four mirror polarizer was added behind one wave plate to provide additional polarization. The mechanical design, testing, and operation of the polarimeter for the high resolution ultraviolet spectrometer/polarimeter are described.

Calvert, J. A.↗