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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Characterization of point focusing test bed concentrators at JPL

The characterization data were measured using both a flux mapper and a cold water calorimeter. The flux mapper uses a Kendall Radiometer as the sensing device. It is mounted on an x, y, z motor-driven positioning mechanism that allows the sensor to take an x-y flux raster at several Z planes in the vicinity of the concentrators nominal focal plane. Various concepts were tried to protect the concentrator structure from being damaged by the Sun's energy during sun acquisition and deacquisition. A description of both the passive and active protective systems is presented.

Starkey, D. J.↗
NASA NTRS1981

General Electric point focus solar concentrator status

The concentrator design approach evolved by a systemmatic process of examining the operating requirements particular to the solar application, minimizing material content through detail structural design and structurally efficient subsystem features, and utilizing materials and processes compatible with high volume production techniques. The design approach, the present concentrator configuration and the status of the hardware development are described.

Zimmerman, J.↗
NASA NTRS1981

The plasma wake of mesosonic conducting bodies. I - An experimental parametric study of ion focusing by the plasma sheath

The experimental investigation considered is concerned with the deflection of ion streams resulting from the interaction of conducting test bodies with an unmagnetized, mesosonic (supersonic with respect to ions but subsonic with respect to electrons) plasma stream. The investigation is, therefore, limited to plasma-electrostatic interactions. The experimental conditions are similar to those of the spacecraft-ionospheric interaction in that the ionic mass and number density, the electron temperature, and the plasma drift velocity ranges include values appropriate for small satellites or diagnostic probes at 200 to 400 km altitude. The study provides direct observations of deflected ion streams for cylindrical test bodies and gives a detailed description of the effects of the governing, dimensionless parameter ratios obtained from the steady-state, nonmagnetic Maxwell-Vlasov system of equations.

Stone, N. H.↗
NASA NTRS1981

The effects of focusing on the efficiency of coherent anti-Stokes Raman scattering

The efficiency of coherent anti-Stokes Raman scattering (CARS) is calculated as a function of the input beam sizes of the Stokes and pump laser beams. A Green's function formalism is used to show that maximum efficiency occurs when the confocal parameters of the two input beams are unequal and when the phase mismatch between the anti-Stokes field and the nonlinear polarization is nonzero.

Guha, S.↗
NASA NTRS1980

Simulation of isoelectro focusing processes

This paper presents the computer implementation of a model for the stationary electrolysis of two or more charged species. This has specific application to the technique of isoelectric focussing, in which the stationary electrolysis of ampholytes is used to generate a pH gradient useful for the separation of proteins, peptides and other biomolecules. The fundamental equations describing the process are given. These equations are transformed to a form suitable for digital computer implementation. Some results of computer simulation are described and compared to data obtained in the laboratory.

Palusinski, O. A.↗
NASA NTRS1981

A conceptual design study of point focusing thin-film solar concentrators

Candidates for reflector panel design concepts, including materials and configurations, were identified. The large list of candidates was screened and reduced to the five most promising ones. Cost and technical factors were used in making the final choices for the panel conceptual design, which was a stiffened steel skin substrate with a bonded, acrylic overcoated, aluminized polyester film reflective surface. Computer simulations were run for the concentrator optics using the selected panel design, and experimentally determined specularity and reflectivity values. Intercept factor curves and energy to the aperture curves were produced. These curves indicate that surface errors of 2 mrad (milliradians) or less would be required to capture the desired energy for a Brayton cycle 816 C case. Two test panels were fabricated to demonstrate manufacturability and optically tested for surface error. Surface errors in the range of 1.75 mrad and 2.2 mrad were measured.

Source record↗
NASA NTRS1982

Orbiter radiator panel solar focusing test

A test was conducted to determine the solar reflections from the Orbiter radiator panels. A one-tenth scale model of the forward and mid-forward radiator panels in the deployed position was utilized in the test. Test data was obtained to define the reflected one-sun envelope for the embossed silver/Teflon radiator coating. The effects of the double contour on the forward radiator panels were included in the test. Solar concentrations of 2 suns were measured and the one-sun envelope was found to extend approximately 86 inches above the radiator panel. A limited amount of test data was also obtained for the radiator panels with the smooth silver/Teflon coating to support the planned EVA on the Orbiter STS-5 flight. Reflected solar flux concentrations as high as 8 suns were observed with the smooth coating and the one-sun envelope was determined to extend 195 inches above the panel. It is recommended that additional testing be conducted to define the reflected solar environment beyond the one-sun boundary.

Howell, H. R.↗
NASA NTRS1985

Telescoping Shield for Point-Focusing Solar Concentrators

Telescoping shield normally stowed around solar receiver protects heat engine and supporting structure from overheating when concentrator aimed few degrees away from line to Sun. When extended, shield intercepts off center concentrated solar radiation. Heat spread out over thermally conductive shield and reradiated diffusely not to cause structural damage.

Argoud, M.↗
NASA NTRS1984

Optical Analysis of Cassegrainian Point Focus Concentrators

A Cassegrainian solar concentrator, using a 7-meter diameter primary reflector, was analyzed in three forms: (1) an unmodified Cassegrainian, (2) the Ritchey-Chretien configuration, and (3) the unmodified Cassegrainian with a non-imaging tertiary reflector. Optical performance was not significantly improved with the Ritchey-Chretien; however, the tertiary resulted in significant improvement in intercept factor and optical efficiency. The effects of misalignment of the secondary and tertiary reflectors on the optical performance of the collector were also analyzed.

Waterbury, S. S.↗
NASA NTRS1984

The 64-m Antenna Automatic Subreflector Focusing Controller

Defocussing of the radio frequency beam arises from gravity-induced structural deformations as the 64 m Deep Space Network antenna rotates about the elevation axis. The subreflector controller generates the axial (z) and lateral (y) offset corrections necessary to move the subreflector, thus minimizing the gain losses due to this defocussing. The technique used to determine these offset errors is discussed, and a description of the new subreflector controller is presented.

Guiar, C. N.↗
NASA NTRS1983

Reduced thermal focusing and birefringence in zig-zag slab geometry crystalline lasers

The present investigation is concerned with interferometric measurements of the thermally induced optical effects in laser crystals, taking into account crystals cut in both the zig-zag slab and the conventional rod geometries. The measurements conducted demonstrate the significant advantages obtained by replacing the rod in a Nd:YAG laser with a slab. A description is provided of simple measures designed to eliminate end and edge effects, and efficiency and threshold data for the Nd:YAG slab and the rod it replaced are presented. The only disadvantage is a small increase in cost due to the more difficult fabrication of the slab and the greater amount of Nd:YAG which is needed to allow the ends to be unpumped.

Kane, T. J.↗
NASA NTRS1984

Double focusing ion mass spectrometer of cylindrical symmetry

A mass spectrometer consisting of an electric sector followed by a magnetic sector is described. The geometry is a cylindrically symmetric generalization of the Mattauch-Herzog spectrometer (1934). With its large annular entrance aperture and a position-sensitive detector, the instrument provides a large geometric factor and 100-percent duty factor, making it appropriate for spacecraft experiments.

Coplan, M. A.↗
NASA NTRS1985

Out-of-Focus Alinement of Solar Concentrators

In new alinement technique, no attempt made to simulate infinitely distant light source, and all mirrors left uncovered throughout procedure. Light source placed at distance of 1,650 feet (503 m); other distances used. Alinement of approximately 250 mirror facets of paraboloidal solar concentrator simplified by precalculated images reflected from all facets. Developed for large solar concentrators, technique used with other multiplemirror or multiple-light-source systems for producing specified illuminance patterns.

Argoud, M. J.↗
NASA NTRS1984

The Interaction of Focused Attention with Flow-field Sensitivity

Two studies were performed to determine whether a subject's response to naturalistic optical flow specifying egomotion would be affected by a concurrent attention task. In the first study subjects stood in a moving room in which various areas of the optical flow generated by room movement were visible. Subjects responded to room motion with strong compensatory sway when the entire room was visible. When the side walls of the room were completely obscured by stationary screens, leaving only the front wall visible, sway was significantly reduced, though it remained greater than in an eyes-closed control. In Exp. 2 subjects were presented with either the full room (large sway response) or the room with only the front wall visible (moderate response), each in combination with either a hard or easy verbal addition task. Preliminary results show that swaying in the fully visible room and in the room with only the front wall visible increased when combined with either the hard or easy tasks. These preliminary results suggest that at the least the pick-up of optical flow specifying egomotion is not affected by concurrent attentional activity.

Stoffregen, T.↗
NASA NTRS1984

Astrometric plates obtained at the primary focus of large aperture reflectors

Coma, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.

Markos, A.↗
NASA NTRS1985

Boundary to Constructive Solid Geometry Mappings: a Focus on 2-D Issues

The problem of converting boundary representation (B-rep) to constructive solid geometry representation (CSG-rep) (and vice versa) is discussed in two phases. The first phase entails finding a CSG-rep that defines the region bounded by a polygonal profile curve. The second phase utilizes the results of the first phase to find a CSG-rep for many non-polygonal profile curves. A mathematically concise representation of a region bounded by a polygonal is presented. Namely, any polygonal region bounded by an n sided polygon may be represented by a binary tree which has at most n planar halfspaces as leaves. A structure for this representation and an algorithm for calculating is discussed.

Peterson, D. P.↗