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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Fissioning uranium plasmas and nuclear-pumped lasers

Current research into uranium plasmas, gaseous-core (cavity) reactors, and nuclear-pumped lasers is discussed. Basic properties of fissioning uranium plasmas are summarized together with potential space and terrestrial applications of gaseous-core reactors and nuclear-pumped lasers. Conditions for criticality of a uranium plasma are outlined, and it is shown that the nonequilibrium state and the optical thinness of a fissioning plasma can be exploited for the direct conversion of fission fragment energy into coherent light (i.e., for nuclear-pumped lasers). Successful demonstrations of nuclear-pumped lasers are described together with gaseous-fuel reactor experiments using uranium hexafluoride.

Schneider, R. T.↗
NASA NTRS1977

Hybrid optical/digital detector

Device for automatic-diffraction pattern recognition is designed around concentric-ring fiber-optic array. Coherent light passes through film-image transparency and lens producing Fourier transform of image. Transform is converted to digital data, the basis of diffraction-pattern recognition program performed by computer.

Shackelford, R. G.↗
NASA NTRS1977

Conceptual design of an on-board optical processor with components

The specification of components for a spacecraft on-board optical processor was investigated. A space oriented application of optical data processing and the investigation of certain aspects of optical correlators were examined. The investigation confirmed that real-time optical processing has made significant advances over the past few years, but that there are still critical components which will require further development for use in an on-board optical processor. The devices evaluated were the coherent light valve, the readout optical modulator, the liquid crystal modulator, and the image forming light modulator.

Walsh, J. R.↗
NASA NTRS1978

Speckle techniques for determining stresses in moving objects

Laser speckle interferometry is a relatively new experimental technique which shows promise of alleviating many difficult problems in experimental mechanics. The method utilizes simple high-resolution photographs of the surface which is illuminated by coherent light. The result is a real-time or permanently stored whole-field record of interference fringes which yields a map of displacements in the object. In this thesis, the time-average theory using the Fourier transform is developed to present the application of this technique to measurement of in-plane displacement induced by the vibration of an object.

Murphree, E. A.↗
NASA NTRS1980

Optical comparator uses holographic subtraction

Integrated optical comparator compares reference and signal voltages by their effects on coherent light beam. If both voltages are same, beam is essentially unperturbed. If voltages differ, light is deflected by previously recorded hologram to detector.

Vahey, D. W.↗
NASA NTRS1978

Petrology of Apollo 16 breccia 66075

66075 is a coherent, light matrix breccia with a seriate fabric and is composed of large lithic, mineral and glass clasts in a matrix of lithic, mineral and glass fragments. The lithic clasts are ANT-suite rocks and a texturally diverse suite of impact-generated melt-rocks. The mineral fragments in the matrix and the mineral clasts are mostly plagioclase with subordinate amounts of pyroxene and olivine. The mineral compositions and/or bulk compositions of most of the components of the breccia, as well as the U-Pb isotopic systematics, are compatible with an origin involving impact-melting and fragmentation of an ANT-suite protolith. The major element composition of the breccia matrix can be successfully modeled in terms of mixing the observed clast types. Previously suggested components such as 'dunite' and 'KREEP' are absent or occur in very low abundance.

Quick, J. E.↗
NASA NTRS1980

Side-looking airborne radar image interpretation and geological mapping: Problems and results

Geological experiments and surveys conducted by BRGM and GDTA members to evaluate interest in SLAR image interpretation are summarized. Two surveys were selected for presentation: Les Vans (Massif central, France) and Guyana (South America). They have permitted a comparison between different types of SLAR: Goodyear, Motorola, JPL, and Vigie in term of lithological and structural applications. On the Les Vans test site conclusions reached concern radiometry, which is better on L-band imagery, polarization, HV being more useful than HH for geological mapping in an L-band system, wavelength and illuminations. Over Guyana, the use of Goodyear X-band SLAR enables satisfactory geological and structural mapping under heavy equatorial forest with cloud cover conditions. A differential program was developed for fracture filtering and image enhancement with a coherent light laser, and significant results were obtained.

Scanvic, J. Y.↗
NASA NTRS1980

Measurement of velocity fields in fluid dynamics experiments

A microcomputer-video system was used to measure both spatial and temporal variations of two dimensional fluid flow velocity fields. The system utilizes two methods: the first method is the traditional one in which tracers are introduced into the fluid and their position compared at two closely spaced times; and the second method involves scattering coherent light in the fluid and obtaining motion by analyzing the multiple exposed speckle pattern recorded on photographic film.

Fitzjarrald, D. E.↗
NASA NTRS1981

Bulk and integrated acousto-optic spectrometers for radio astronomy

The development of sensitive heterodyne receivers (front end) in the centimeter and millimeter range, and the construction of sensitive RF spectrometers (back end) enable the spectral lines of interstellar molecules to be detected and identified. A technique was developed which combines acoustic bending of a collimated coherent light beam by a Bragg cell followed by detection by a sensitive array of photodetectors (thus forming an RF acousto-optic spectrometer (AOS). An AOS has wide bandwidth, large number of channels, and high resolution, and is compact, lightweight, and energy efficient. The thrust of receiver development is towards high frequency heterodyne systems, particularly in the millimeter, submillimeter, far infrared, and 10 micron spectral ranges.

Chin, G.↗
NASA NTRS1983

Interferometric angle monitor

Two mutually coherent light beams formed from a single monochromatic light source were directed to a reflecting surface of a rotatable object. They were reflected into an imaging optical lens having a focal plane optically at infinity. A series of interference fringes were formed in the focal plane which were translated linearly in response to angular rotation of the object. Photodetectors were located adjacent the focal plane to detect the fringe translation and output a signal in response to the translation. The signal was fed to a signal processor which was adapted to count the number of fringes detected and develop a measure of the angular rotation and direction of the object.

Minott, P. O.↗
NASA NTRS1981

Bulk and integrated acousto-optic spectrometers for molecular astronomy with heterodyne spectrometers

A survey of acousto-optic spectrometers for molecular astronomy is presented, noting a technique of combining the acoustic bending of a collimated coherent light beam with a Bragg cell followed by an array of sensitive photodetectors. This acousto-optic spectrometer has a large bandwidth, a large number of channels, high resolution, and is energy efficient. Receiver development has concentrated on high-frequency heterodyne systems for the study of the chemical composition of the interstellar medium. RF spectrometers employing acousto-optic diffraction cells are described. Acousto-optic techniques have been suggested for applications to electronic warfare, electronic countermeasures and electronic support systems. Plans to use integrated optics for the further miniaturization of acousto-optic spectrometers are described. Bulk acousto-optic spectrometers with 300 MHz and 1 GHz bandwidths are being developed for use in the back-end of high-frequency heterodyne receivers for astronomical research.

Chin, G.↗
NASA NTRS1983

Application of optical fibers to wide-band differential interferometry

A broadband differential optical interferometer that uses an optical-fiber waveguide to transmit coherent light to a surface under inspection is discussed. Input laser light is coupled into two single-mode optical fibers in a stationary input optics enclosure. The fibers transmit the light to a small, remote detection head where it is used in a wide-band differential interferometer to detect continuous and pulsed surface-particle displacements. The effective separation between the input optics and the detection head allows simple surface scanning and probe alignment. Detection of simulated acoustic emission pulses by a prototype test unit is reported.

Garg, A. O.↗
NASA NTRS1986

Optical distance measuring instrument

An optical instrument, such as a stability monitor or a target range finder, uses an unstabilized laser to project a composite optical signal of coherent light having two naturally occurring longitudinal mode components. A beamsplitter divides the signal into a reference beam which is directed toward one photodetector and a transmitted beam which illuminates and is reflected from a distant target onto a second photodetector optically isolated from the first photodetector. Both photodetectors are operated on the square law principle to provide electrical signals modulated at a frequency equal to the separation between the frequencies of the two longitudinal mode components of the optical signal projected by the laser. Slight movement of the target may be detected and measured by electrically monitoring the phase difference between the two signals provided by the photodetectors and the range of the target measured with the aid of a microprocessor by changing the separation between the longitudinal modes by shifting the length of the resonator cavity in an iterative series of increments.

Abshire, J. B.↗
NASA NTRS1988

Range and range rate system

A video controlled solid state range finding system which requires no radar, high power laser, or sophisticated laser target is disclosed. The effective range of the system is from 1 to about 200 ft. The system includes an opto-electric camera such as a lens CCD array device. A helium neon laser produces a source beam of coherent light which is applied to a beam splitter. The beam splitter applies a reference beam to the camera and produces an outgoing beam applied to a first angularly variable reflector which directs the outgoing beam to the distant object. An incoming beam is reflected from the object to a second angularly variable reflector which reflects the incoming beam to the opto-electric camera via the beam splitter. The first reflector and the second reflector are configured so that the distance travelled by the outgoing beam from the beam splitter and the first reflector is the same as the distance travelled by the incoming beam from the second reflector to the beam splitter. The reference beam produces a reference signal in the geometric center of the camera. The incoming beam produces an object signal at the camera.

Graham, Olin L.↗
NASA NTRS1988

Laser agile illumination for object tracking and classification - Feasibility study

The 'agile illumination' concept for discrimination between ICBM warheads and decoys involves a two-aperture illumination with coherent light, diffraction of light by propagation, and a resulting interference pattern on the object surface. A scanning two-beam interference pattern illuminates one object at a time; depending on the shape, momentum, spinning, and tumbling characteristics of the interrogated object, different temporal signals will be obtained for different classes of objects.

Scholl, Marija S.↗
NASA NTRS1991

Fiber optic sensing system

A fiber optic interferometer utilizes a low coherence light emitting diode (LED) laser as a light source which is filtered and driven at two RF frequencies, high and low, that are specific to the initial length of the resonator chamber. A displacement of a reflecting mirror changes the length traveled by the nonreferencing signal. The low frequency light undergoes destructive interference which reduces the average intensity of the wave while the high frequency light undergoes constructive interference which increases the average intensity of the wave. The ratio of these two intensity measurements is proportional to the displacement incurred.

Adamovsky, Grigory↗
NASA NTRS1989

Two-dimensional high temperature strain measurement system

Two-dimensional optical strain measurements on high temperature test specimens are presented. This two-dimensional capability is implemented through a rotatable sensitive strain axis. Three components of surface strain can be measured automatically, from which the first and second principal strains are calculated. One- and two-dimensional strain measurements at temperatures beyond 750 C with a resolution of 15 microstrain are demonstrated. The system is based on a one-dimensional speckle shift technique. The speckle shift technique makes use of the linear relationship between surface strain and the differential shift of laser speckle patterns in the diffraction plane. Laser speckle is a phase effect that occurs when spatially coherent light interacts with an optically rough surface. Since speckle is generated by any diffusely reflecting surface, no specimen preparation is needed to obtain a good signal. Testing was done at room temperature on a flat specimen of Inconel 600 mounted in a fatigue testing machine. A load cell measured the stress on the specimen before and after acquiring the speckle data. Strain components were measured at 0 C (parallel to the load axis) and at plus or minus 45 C, and plots indicate the calculated values of the first and second principal strains. The measured values of Young's modulus and Poisson's ratio are in good agreement with handbook values. Good linearity of the principal strain moduli at high temperatures indicate precision and stability of the system. However, a systematic error in the high-temperature test setup introduced a scale factor in the slopes of the two-dimensional stress-strain curves. No high temperature effects, however, have been observed to degrade speckle correlation.

Lant, Christian T.↗
NASA NTRS1992

Equal path, phase shifting, sample point interferometer for monitoring the configuration of surfaces

A system for monitoring the configuration of a surface (e.g., a segmented parabolic surface) using orthogonally placed retroreflectors at sets of points 1, 2, and 3 dispersed throughout the surface with a stationary halfwave plate (HWP) in the front of the one retroreflector at a corner point 3 and a rotating halfwave plate (RHWP) over a source of linearly polarized coherent light, thereby causing the direction of linear polarization to continuously rotate through 360 deg and causing light returned by the retroreflector at point 3 to be continuously phase shifted through 360 deg relative to light returned by retroreflectors at points 1 and 2. The returned light from each set of points 1, 2, and 3 is focused onto a bed-of-nails (BON) phase grating diagonally oriented with respect to the orthogonal orientation of the incident beams from retroreflectors 1, 2, and 3, thereby causing overlap in the light from points 1 and 3 to produce interferometric signals 1,3 and 2,3. Any change in phase of the interferometric signals 1,3 and 2,3 indicates both the magnitude and direction of any change in the position of the retroreflector at point 3 relative to retroreflectors at points 1 and 2.

Manhart, Paul K.↗