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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 307 records · Page 17

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NASA NTRS1995

Velocity Fields of Axisymmetric Hydrogen-Air Counterflow Diffusion Flames from LDV, PIV, and Numerical Computation

Laminar fuel-air counterflow diffusion flames (CFDFs) were studied using axisymmetric convergent-nozzle and straight-tube opposed jet burners (OJBs). The subject diagnostics were used to probe a systematic set of H2/N2-air CFDFs over wide ranges of fuel input (22 to 100% Ha), and input axial strain rate (130 to 1700 Us) just upstream of the airside edge, for both plug-flow and parabolic input velocity profiles. Laser Doppler Velocimetry (LDV) was applied along the centerline of seeded air flows from a convergent nozzle OJB (7.2 mm i.d.), and Particle Imaging Velocimetry (PIV) was applied on the entire airside of both nozzle and tube OJBs (7 and 5 mm i.d.) to characterize global velocity structure. Data are compared to numerical results from a one-dimensional (1-D) CFDF code based on a stream function solution for a potential flow input boundary condition. Axial strain rate inputs at the airside edge of nozzle-OJB flows, using LDV and PIV, were consistent with 1-D impingement theory, and supported earlier diagnostic studies. The LDV results also characterized a heat-release hump. Radial strain rates in the flame substantially exceeded 1-D numerical predictions. Whereas the 1-D model closely predicted the max I min axial velocity ratio in the hot layer, it overpredicted its thickness. The results also support previously measured effects of plug-flow and parabolic input strain rates on CFDF extinction limits. Finally, the submillimeter-scale LDV and PIV diagnostics were tested under severe conditions, which reinforced their use with subcentimeter OJB tools to assess effects of aerodynamic strain, and fueVair composition, on laminar CFDF properties, including extinction.

Pellett, Gerald L.↗

NASA NTRS2000

Full Field Scalar Measurements in a Pulsating Helium Jet using Rainbow Schlieren Deflectometry

The flow structure of a pulsating helium jet was investigated using quantitative rainbow schlieren deflectometry. The operating parameters included the tube inside diameter, the jet Reynolds number and the jet Richardson number. The jet structure was characterized by the frequency spectrum, temporal evolution of the oscillations and mean and root-mean-square profiles of the species mole fraction, which in this case, was helium. Experiments were conducted using a variable nozzle facility. Angular deflection data were obtained using rainbow schlieren deflectometry across full field of color images taken at a temporal resolution of 60Hz. The flicker cycle was analyzed by instantaneous rainbow schlieren images, contour plots of deflection angle and helium mole fraction placed sequentially in time. Two observe the flow downstream, the tube was lowered with respect to the optical setup and images were taken at different axial planes. In this way, the laminar, transition and turbulent regions of the jet flow were observed. Abel inversion algorithm was utilized to reconstruct the refractive index field from the measurements of the beam deflection angle. The concentration field was then generated from the refractive index field. The phenomenon of vortex initiation and propagation in the flicker cycle was described by correlating the ray deflection angle and concentration contour plots. Experiments in the flickering jet reveal global oscillation in the flow field. The effect of jet exit Reynolds number and jet Richardson number on the flickering frequency was analyzed. The effect of jet Richardson number was more pronounced than that of the jet exit Reynolds number. The flow field was studies quantitatively in terms of temporal evolution and statistical description of helium mole fraction.

Pasumarthi, Kasyap S.↗

NASA NTRS1998

[Results of the EGRET Detector Program]

This NASA grant has funded studies of cosmic objects observed by both the EGRET detector aboard the Compton Gamma-ray Observatory and Whipple Gamma-ray imaging telescope. The former has sensitivity up to a few GeV and latter has sensitivity starting at about 200 GeV extending up to beyond 10 TeV. Thus these instruments probe some of the most energetic phenomena in the universe. This program has been in place for several years and led to important results referred to below. The Whipple Observatory Imaging Cherenkov Telescope consists of a 10-meter reflector with a nanosecond photomultiplier-tube camera at the focal plane. During the time period covered by this grant, it had either 109 pixels or 151 pixels on a 1/4 degree hexagonal pattern. As a TeV gamma ray enters the atmosphere, it produces an electron/positron pair initiating an extensive air shower. Cherenkov light from the electrons and positrons in the shower form an image of the shower at the phototube camera. The shape and intensity of this image is used to distinguish gamma-ray initiated showers from cosmic-ray (largely proton and alpha-particle) background showers and to derive an energy estimate for the primary gamma-ray. The Whipple Observatory gamma-ray collaboration pioneered this imaging technique which normally rejects over 99 percent of the cosmic-ray background while keeping over 70 percent of the gamma-ray signal. One of its key features is 2 large collection area which can exceed 50,000 meters. This grant covered primarily correlated observations of Markarian 421 and observations of the Cygnus region. The former resulted in a multiwavelength campaign showing correlations in several wavebands. The TeV data showed dramatic variability with the emission characterized by day-scale flickering and with now well defined steady component.

Carter-Lewis, D. A.↗

NASA NTRSDate not supplied

Investigating Pyroclastic Volcanism in the Taurus-Littrow Valley (TLV) Using the Station 3 Double Drive Tube 73001-73002

Well over 100 pyroclastic deposits have been identified on the Moon. Eruptive processes such as represented by these deposits transported endogenous volatiles from the Moon’s mantle to its surface. Debris from pyroclastic deposits has been identified in all Apollo and Luna samples. The high-Ti pyroclastic de- posit sampled at Shorty Crater by the Station 4 double drive tube (74001-74002) is our best sampling of these types of deposits. Samples 78500 and 78526, NAC images of fissures in the Sculptured Hills, ash identified in 70001-7, and other green volcanic glass indicate that very low-Ti basalt (VLT) erup- tions also occurred in TLV. The double drive tube core being investigated by the ANGSA initiative provides an- other view of TLV pyroclastic eruptions. The regolith in 73001-73002 and the regolith breccias therein have nu- merous pyroclastic beads. Some individual regolith brec- cia fragments have abundant pyroclastic beads (>50 in a polished surface). In this work, we address the following questions. Do these glass beads overlap in composition with those sampled elsewhere in the TLV or do they rec- ord another episode of pyroclastic eruption? Are the magmas associated with pyroclastic eruptions petroge- netically related to the crystalline mare basalts in the TLV? Finally, is the volatile record of the pyroclastic eruptions better preserved in the newly opened and spe- cially contained Station 3 double drive tube core?

C.K. Shearer↗

NASA NTRS1975

Development of a CCD for ultraviolet imaging using a CCD photocathode combination

CCD in the electron-in mode, coupled with a bi-alkali photocathode to produce UV photon conversion, provides the following desirable features: (1) high UV response of the bi-alkali photocathode; (2) excellent imaging quality of a CCD area array; and (3) high signal-to-noise ratio due to the EBS (electron bombarded silicon) gain of the CCD operating in a tube configuration. This paper describes the rationale and progress made in developing a CCD for use as an UV imager.

Collins, D. R.↗

NASA NTRS1980

A computer system for geosynchronous satellite navigation

A computer system specifically designed to estimate and predict Geostationary Operational Environmental Satellite (GOES-4) navigation parameters using Earth imagery is described. The estimates are needed for spacecraft maneuvers while prediction provide the capability for near real-time image registration. System software is composed of four functional subsystems: (1) data base management; (2) image processing; (3) navigation; and (4) output. Hardware consists of a host minicomputer, a cathode ray tube terminal, a graphics/video display unit, and associated input/output peripherals. System validity is established through the processing of actual imagery obtained by sensors on board the Synchronous Meteorological Satellite (SMS-2). Results indicate the system is capable of operationally providing both accurate GOES-4 navigation estimates and images with a potential registration accuracy of several picture elements (pixels).

Koch, D. W.↗

NASA NTRS1994

Vortex tubes in turbulent flows: Identification, representation, reconstruction

In many cases the structure of a fluid flow is well-characterized by its vortices, especially for the purpose of visualization. In this paper we present a new algorithm for identifying vortices in complex flows. The algorithm produces a skeleton line along the center of a vortex by using a two-step predictor-corrector scheme. The vorticity vector field serves as the predictor and the pressure gradient (in the perpendicular plane) serves as the corrector. We describe an economical description of the vortex tube's cross-section: a 5-term truncated Fourier series is generally sufficient, and it compresses the representation of the flow by a factor of 4000 or more. We reconstruct the vortex tubes as generalized cylinders, providing a polygonal mesh suitable for display on a graphics workstation. We show how the reconstructed geometry of vortex tubes can be enhanced to help visualize helical motion in a static image.

Banks, David C.↗

NASA NTRS1994

A Third Arm for the Surgeon

In laparoscopic surgery, tiny incisions are made in the patient's body and a laparoscope (an optical tube with a camera at the end) is inserted. The camera's image is projected onto two video screens, whose views guide the surgeon through the procedure. AESOP, a medical robot developed by Computer Motion, Inc. with NASA assistance, eliminates the need for a human assistant to operate the camera. The surgeon uses a foot pedal control to move the device, allowing him to use both hands during the surgery. Miscommunication is avoided; AESOP's movement is smooth and steady, and the memory vision is invaluable. Operations can be completed more quickly, and the patient spends less time under anesthesia. AESOP has been approved by the FDA.

Source record↗

NASA NTRS1982

Highly versatile computer-controlled television detector system

A description is presented of a television detector system which has been designed to accommodate a wide range of applications. It is currently being developed for use in X-ray diffraction, X-ray astrophysics, and electron microscopy, but it is also well suited for astronomical observations. The image can be integrated in a large, high-speed memory system, in the memory of a computer system, or the target of the TV tube or CCD array. The detector system consists of a continuously scanned, intensified SIT vidicon with scan and processing electronics which generate a digital image that is integrated in the detector memory. Attention is given to details regarding the camera system, scan control and image processing electronics, the memory system, and aspects of detector performance.

Kalata, K.↗

NASA NTRS2016

The Mapping X-Ray Fluorescence Spectrometer (MAPX)

MapX will provide elemental imaging at ≤100 micron spatial resolution over 2.5 X 2.5 centimeter areas, yielding elemental chemistry at or below the scale length where many relict physical, chemical, and biological features can be imaged and interpreted in ancient rocks. MapX is a full-frame spectroscopic imager positioned on soil or regolith with touch sensors. During an analysis, an X-ray source (tube or radioisotope) bombards the sample surface with X-rays or αlpha-particles / gamma rays, resulting in sample X-ray Fluorescence (XRF). Fluoresced X-rays pass through an X-ray lens (X-ray μ-Pore Optic, "MPO") that projects a spatially resolved image of the X-rays onto a CCD. The CCD is operated in single photon counting mode so that the positions and energies of individual photons are retained. In a single analysis, several thousand frames are stored and processed. A MapX experiment provides elemental maps having a spatial resolution of ≤100 micron and quantitative XRF spectra from Regions of Interest (ROI) 2 centimers ≤ x ≤ 100 micron. ROI are compared with known rock and mineral compositions to extrapolate the data to rock types and putative mineralogies. The MapX geometry is being refined with ray-tracing simulations and with synchrotron experiments at SLAC. Source requirements are being determined through Monte Carlo modeling and experiment using XMIMSIM [1], GEANT4 [2] and PyMca [3] and a dedicated XRF test fixture. A flow-down of requirements for both tube and radioisotope sources is being developed from these experiments. In addition to Mars lander and rover missions, MapX could be used for landed science on other airless bodies (Phobos/Deimos, Comet nucleus, asteroids, the Earth's moon, and the icy satellites of the outer planets, including Europa.

Blake, David↗

NASA NTRS1980

Study of stray light suppression for the large space telescope

Analysis of light scattering, using the APART computer program, begins at the image plane and progresses through the optical system to the front end of the telescope tube. The approach identifies all critical surfaces, computes the geometrical configuration factors (GCF) from each area of the system under study to all other areas of the system, and determines incident and reflected angles which are important for baffle surfaces which do not have Lambertian scattering characteristics. The power input into the optical surface from either point source objects or extended objects such as the bright Earth are computed. The surface scattering characteristics and the GCF values are combined so that the power transfer to the image plane is computed. Capabilities for handling light scattering from baffle surfaces, specular reflectance from black surfaces, scattering from mirror surfaces, diffraction, internal scattering from transmissive optics, and internal thermal emission are assessed.

Fannin, B. B.↗

NASA NTRS1975

Asteroid observations and planetary atmospheres analysis

Photoelectric observations of Eros and 30 other asteroids providing information on their surface characteristics, shape, and rotation axes are reported. Photographs of 18 asteroids and 4 comets yielding accurate position information on various dates were obtained. Photometric observations were made of the Saturn satellite lapetus, and electronographic images of the Uranus and Neptune satellites were obtained experimentally with a Spectracon tube to assess photometry by that method. Planetary patrol photographs of Venus and deconvolved area scans of Uranus were taken. UBV photometry of the Galilean satellites for the period 1973-1974 was completely analyzed and accepted for publication. An improved magnitude and color index for Minas were derived from 1974 area scans. A special photomultiplier tube with a suppressor grid was incorporated into a pulse-counting photometer with special added circuitry for carrying out the observations concerning the constancy of solar system dimensions over cosmic time.

Baum, W. A.↗

NASA NTRS1977

TV fatigue crack monitoring system

An apparatus is disclosed for monitoring the development and growth of fatigue cracks in a test specimen subjected to a pulsating tensile load. A plurality of television cameras photograph a test specimen which is illuminated at the point of maximum tensile stress. The television cameras have a modified vidicon tube which has an increased persistence time thereby eliminating flicker in the displayed images.

Exton, R. J.↗

NASA NTRS1977

Liquid-Cooled Garment

A liquid-cooled bra, offshoot of Apollo moon suit technology, aids the cancer-detection technique known as infrared thermography. Water flowing through tubes in the bra cools the skin surface to improve resolution of thermograph image.

Source record↗

NASA NTRSDate not supplied

Summary of Shock Wave Turbulent Boundary Layer Interaction Experiments In a Circular Test Section

A series of experiments were performed at Mach 2.5 in a 17 cm diameter circular test section to characterize an impinging/reflected shock wave turbulent boundary layer interaction generated by a cone-cylinder centerbody. The cone-cylinder centerbody generates a conical shock wave that interacts with the naturally occurring boundary layer developing on the test section wall. Three different cone angles were used in the experiment to study unseparated, incipiently separated, and separated interactions. When the cone-cylinder centerbody is positioned on the centerline, a flowfield which is two-dimensional in the mean is generated. Three dimensional interactions were also created by offsetting the cone-cylinder centerbody from the test section centerline. The results are intended to provide benchmark quality datasets for computational fluid dynamics (CFD) validation without the pitfalls inherent in rectangular configurations where corner effects prohibit a truly two-dimensional flow in the mean. The experimental measurements included surface flow visualization, wall static pressure, flowfield Pitot tube pressure, constant-voltage anemometry (CVA) normal hot-wire, and particle image velocimetry (PIV) measurements. The hot-wire measurements were used to calculate mean mass flux and total temperature profiles, mass flux and total temperature turbulence intensities, and the mass flux-total temperature correlation. The PIV measurements provide three-dimensional mean velocity measurements. Agreement between the pressure, hot-wire, and PIV measurements is established in the undisturbed upstream flowfield.

Supersonic↗

NASA NTRSDate not supplied

Summary of Shock Wave Turbulent Boundary Layer Interaction Experiments in a Circular Test Section

compressible flow↗

NASA NTRS1989

The soft x ray telescope for Solar-A

The Solar-A satellite being prepared by the Institute for Sapce and Astronautical Sciences (ISAS) in Japan is dedicated to high energy observations of solar flares. The Soft X Ray Telescope (SXT) is being prepared to provide filtered images in the 2 to 60 A interval. The flight model is now undergoing tests in the 1000 foot tunnel at MSFC. Launch will be in September 1991. Earlier resolution and efficiency tests on the grazing incidence mirror have established its performance in soft x rays. The one-piece, two mirror grazing incidence telescope is supported in a strain free mount separated from the focal plane assembly by a carbon-epoxy metering tube whose windings and filler are chosen to minimize thermal and hygroscopic effects. The CCD detector images both the x ray and the concentric visible light aspect telescope. Optical filters provide images at 4308 and 4700 A. The SXT will be capable of producing over 8000 of the smallest partial frame images per day, or fewer but larger images, up to 1024 x 1024 pixel images. Image sequence with two or more of the five x ray analysis filters, with automatic exposure compensation to optimize the charge collection by the CCD detector, will be used to provide plasma diagnostics. Calculations using a differential emission measure code were used to optimize filter selection over the range of emission measure variations and to avoid redundancy, but the filters were chosen primarily to give ratios that are monotonic in plasma temperature.

Brown, W. A.↗

NASA NTRS1976

The response of fluoroscopic image intensifier-TV systems

Three different types of X-ray fluoroscopic TV chains were investigated: two standard clinical units, one with a vidicon camera tube, the other with a plumbicon camera tube; and the third was a large flat-screen unit. In each an X-ray beam generated at 100 kVp was passed through 10 cm of H2O before aluminum absorbers of varying thickness were introduced. Five video recordings were made at each absorber thickness. The video image was digitized directly from the disk recording and quantized into 128 gray levels. The five recordings were averaged on a point-to-point basis, and the central 900 averaged points were again averaged to yield a value for the gray level assigned to each particular image. This 30 by 30 matrix of points corresponds to input screen areas of 29, 8.2, and 3.6 sq cm for the three units investigated.

Baily, N. A.↗