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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 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Phase-Locked Laser Array With Nonuniform Spacing

To obtain phase-locked array that reliably produces single far-field lobe, configuration includes lasing stripes not placed on regular centers but located in regular way with nonuniform centers (i.e., with spacing determined by some function). Alternatively, lasing stripes placed on set of periodic arrays with different stripe-to-stripe centers interlaced onto single chip or placed in structure in which stripe-to-stripe spacing is random or pseudorandom. Monolithic, phase-locked, semiconductor-laser array design produces output laser beam comprising substantially single lobe.

Ackley, D. E.↗
NASA NTRS1986

Timed Multiple-Laser Array

Pulse power, frequency, and shape variable and combined to suit particular applications. Versatile laser system combines high power with high efficiency, long life, and low cost. System consists of array of excimer lasers fired under microcomputer control. When fired in unison, array produces high-power pulse at higher efficiency than otherwise possible. When fired in sequency, array produces pulses at a high rate without unduly stressing components and shortening their lives.

Laudenslager, J. B.↗
NASA NTRS1986

Low-Concentration-Ratio Solar-Cell Arrays

Paper presents design concept for mass-producible arrays of solar electric batteries and concentrators tailored to individual requirements. Arrays intended primarily for space stations needing about 100 kW of power. However, modular, lightweight, compact, and relatively low-cost design also fulfill requirements of some terrestrial applications. Arrays built with currently available materials. Pultrusions, injectionmolded parts, and composite materials used extensively to keep weight low. For added flexibility in design and construction, silicon and gallium arsenide solar-cell panels interchangeable.

Biss, M. S.↗
NASA NTRS1985

Planning for VLA/DSN arrayed support to the Voyager at Neptune

Preplanning for the use of the National Radio Astronomy Observatory's Very Large Array (VLA) in support of Voyager at Neptune has been underway since early 1982. When arrayed with the Deep Space Network (DSN) antennas at Goldstone, CA, the VLA more than doubles the potential data return over the American longitude for the 1989 Voyager encounter. The background, rationale and current status of planning for VLA-DSN Arrayed Support to the Voyager at Neptune are discussed.

Layland, J. W.↗
NASA NTRS1983

Jet array impingement heat transfer characteristics

Two dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. In addition to the crossflow which originates from the jets following impingement, an initial crossflow is present which approaches the array through an upstream extension of the channel. The configurations considered are intended to model the impingement cooled midchord region of gas turbine airfoils in cases where an initial crossflow is also present. A major objective is determination of the effect of initial crossflow air temperature relative to jet array air temperature on impingement surface heat fluxes.

Florschuetz, L. W.↗
NASA NTRS1986

Computation of the radiation characteristics of a generalized phased array

With the advent of monolithic microwave integrated circuit (MMIC) technology, the phased array has become a key component in the design of advanced antenna systems. Array-fed antennas are used extensively in today's multiple beam satellite antennas. A computer program based on a very efficient numerical technique for calculating the radiated power (Romberg integration), directivity, and radiation pattern of a phased array is described. The formulation developed is very general, and takes into account arbitrary element polarization, E- and H-plane element pattern, element location, and complex element excitation. For comparison purposes sample cases have been presented. Excellent agreement has been obtained for all cases. Also included are a user guide and a copy of the computer program.

Acosta, R. J.↗
NASA NTRS1985

Characterization of EMI generated by the discharge of a VOLT solar array

The interaction of a high-voltage solar array with the space plasma environment is investigated in a laboratory simulation experiment. Discharges are observed to occur when the solar array is at a sufficiently high negative bias with respect to the plasma. The frequency of occurrence of discharge is found to depend critically on the plasma density and on the geometry of the array. The electromagnetic interference (EMI) associated with a discharge is also measured. The amplitude of EMI increases with the magnitude of the high voltage. Since the discharge-generated EMI is of significant amplitude, its effect on the performance of systems in space must be evaluated.

Leung, P.↗
NASA NTRS1986

Mutual coupling effects in antenna arrays, volume 1

Mutual coupling between rectangular apertures in a finite antenna array, in an infinite ground plane, is analyzed using the vector potential approach. The method of moments is used to solve the equations that result from setting the tangential magnetic fields across each aperture equal. The approximation uses a set of vector potential model functions to solve for equivalent magnetic currents. A computer program was written to carry out this analysis and the resulting currents were used to determine the co- and cross-polarized far zone radiation patterns. Numerical results for various arrays using several modes in the approximation are presented. Results for one and two aperture arrays are compared against published data to check on the agreement of this model with previous work. Computer derived results are also compared against experimental results to test the accuracy of the model. These tests of the accuracy of the program showed that it yields valid data.

Collin, R. E.↗
NASA NTRS1986

Intercontinental antenna arraying by symbol stream combining at ICE Giacobini-Zinner encounter

Deep space tracking stations on different continents were arrayed during the encounter of the International Cometary Explorer (ICE) spacecraft with the comet Giacobini-Zinner during September 9 through 12, 1985. This is the first time that telemetry signals received on different continents have been combined to enhance signal to noise ratio. The arraying was done in non-real time using the method of symbol stream combining. The improvement in signal to noise ratio was typically 2 dB over the stronger of the two stations in each array.

Hurd, W. J.↗
NASA NTRS1985

Application of a silicon photodiode array for solar edge tracking in the Halogen Occultation Experiment

The optical and electronic design of the Halogen Occultation Experiment (HALOE) elevation sunsensor is described. This system uses a Galilean telescope to form a solar image on a linear silicon photodiode array. The array is a self-scanned, monolithic charge coupled device. The addresses of both solar edges imaged on the array are used by the control/pointing system to scan the HALOE science instantaneous-field-of-view (IFOV) across the vertical solar diameter during instrument calibration, and then maintain the science IFOV four arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 0.7 micrometer operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability. The HALOE instrument is a gas correlation radiometer that is now being developed by NASA Langley Research Center for the Upper Atmospheric Research Satellite.

Mauldin, L. E., III↗
NASA NTRS1984

Singular value decomposition with systolic arrays

Systolic arrays for determining the singular value decomposition of a mxn, m greater than or equal to n, matrix A of bandwidth w are presented. After A has been reduced to bidiagonal form B by means of Givens plane rotations, the singular values of B are computed by the Golub-Reinsch iteration. The products of plane rotations form the matrices of left and right singular vectors. Assuming each processor can compute or supply a plane rotation, O(wn) processors accomplish the reduction to bidiagonal form in O(np) steps, where p is the number of superdiagonals. A constant number of processors then determines each singular value in about 6n steps. The singular vectors are computed by rerouting the rotations through the arrays used for the reduction to bidiagonal form, or else along the way by employing another rectangular array of O(wm) processors.

Ipsen, I.↗
NASA NTRS1984

Performance characteristics of multi-anode microchannel array detector systems

The multi-anode microchannel arrays (MAMAs) are state-of-the-art, pulse-counting, photoelectric array detectors designed specifically for use in space astrophysics instruments. The present paper provides a description of recent progress related to the development of ultraviolet and visible-light versions of the MAMA detectors, taking into account a comparison of the operating characteristics of these devices with those of photoconductive array detectors, such as the CCDs. Attention is given to MAMA detector system design parameters, the operating characteristics of MAMAs and CCDs, MAMA performance characteristics, and future developments.

Timothy, J. G.↗
NASA NTRS1984

Results of testing short wavelength HgCdTe hybrid focal plane arrays for earth remote sensing applications

The NASA Imaging Spectrometer program has the objective to develop the next generation of earth remote sensing systems. One part of the program is concerned with the production of advanced short-wavelength mercury cadmium telluride (HgCdTe) hybrid focal plane arrays (FPAs). These arrays are needed for several instruments, including the Shuttle Imaging Spectrometer (SIS), which requires a mosaic of six 64 x 64-element arrays with a cutoff wavelength of 2.5 microns. A device description is provided and the test results are considered. The Airborne Imaging Spectrometer (AIS) is discussed, taking into account an instrument description, focal plane requirements, and AIS results.

Blessinger, M. A.↗
NASA NTRS1985

10 kW solar array switching unit performance test results

Solar array switching unit (SASU) technology is an attractive candidate for output power regulation of solar arrays. It offers greater efficiency, lower parts count, modularity and expandability. Since the SASU has switching frequencies upwards of 15 kHz, it was necessary to determine the performance characteristics of the SASU with a real solar array and to assess the impact of long lead lengths on the switching characteristics. To accommodate these requirements, TRW developed a 10 kW, 120 volt SASU which was tested for steady state and transient resistive and converter type loadings. The results of these tests are presented and discussed in this paper.

Fleck, G. W.↗
NASA NTRS1985

Multiband selection with linear array detectors

Several techniques that can be used in an earth-imaging system to separate the linear image formed after the collecting optics into the desired spectral band are examined. The advantages and disadvantages of the Multispectral Linear Array (MLA) multiple optics, the MLA adjacent arrays, the imaging spectrometer, and the MLA beam splitter are discussed. The beam-splitter design approach utilizes, in addition to relatively broad spectral region separation, a movable Multiband Selection Device (MSD), placed between the exit ports of the beam splitter and a linear array detector, permitting many bands to be selected. The successful development and test of the MSD is described. The device demonstrated the capacity to provide a wide field of view, visible-to-near IR/short-wave IR and thermal IR capability, and a multiplicity of spectral bands and polarization measuring means, as well as a reasonable size and weight at minimal cost and risk compared to a spectrometer design approach.

Richard, H. L.↗
NASA NTRS1986

Direct analysis of gain-guided phase-locked semiconductor laser arrays

A method for analyzing arbitrary one-dimensional waveguides is described and applied to find the lateral modes of gain-guided laser arrays directly, without the need for a coupled-mode approximation. Detailed results are given for a four-element array for which experimental results are available, and the effect of varying device parameters on the relative gains of the modes is considered. The results show differences between gain-guided and real-index guided arrays which are not evident in prior analyses.

Marshall, W. K.↗
NASA NTRS1985

A high energy Space Station (HESS) array for studying extremely energetic cosmic rays

The scientific aims and design concept of a High-Energy Space Station (HESS) cosmic-ray detector array are discussed. The current state of knowledge on cosmic-ray acceleration and high-energy interactions is briefly reviewed, and the need for observations yielding elemental composition and spectra in the 10-10,000-TeV/nucleon range is demonstrated. It is predicted that 2 yr of observations with a space-borne detector of geometry factor 30 sq m sr would provide adequate data to determine the acceleration mechanism (by comparing the energy level at which the spectra of He nuclei and protons break). A modular HESS array comprising W/scintillator/PM-tube calorimeter modules and Cerenkov charge-sensitive detector modules and weighing about 30 tonnes is described. The array could be assembled on orbit after transport in the Space Shuttle cargo bay, and data could be taken as soon as one or two layers of modules had been attached to the mounting-frame/support-electronics unit.

Ormes, J. F.↗
NASA NTRS1986

InSb arrays: Astronomy with a 32x32 CCD/development of a 58x62 DRO

Experience gained in operating infrared detector arrays for high sensitivity astronomical applications at the University of Rochester are summarized. Progress made in operating the 32 x 32 InSb array with bump-bonded Silicon CCD readout is described. Astronomical work done with the 32 x 32 camera is also described. Plans for the future, including improvements for the 32 x 32 camera system as well as implementing a new generation of 58 x 62 InSb array using switched-MOSFET direct readout multiplexing system in the place of the older CCD technology is discussed.

Forrest, W. J.↗