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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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Analog and digital mechanizations contain new combinations of known circuits that generate coefficients of Fourier series terms in accordance with harmonic content of waveform to be transmitted. Technique represents information signal more accurately that previous methods and requires fewer information bits.
Improved semiconductor multivibrator circuit which approaches 100 percent efficiency
Design and performance of injected beam crossed field amplifier
Computer design technique of electron gun for use in spacecraft transmitters
Depressed collector has basic configuration of a dish with a central cone and protruding spike. This geometry velocity sorts and slows the electrons down to minimum velocity at collection, and prevents backstreaming of secondaries and reflected primaries into interaction region of the tube.
It is demonstrated that state-of-the-art communications technology can be implemented and reliably operated on a global basis to increase the transmission rates and efficiencies on circuits with bandwidths greater than the typical speech channel. Optimization is affected by optimum clock recovery procedures, multilevel pulse amplitude modulation, single sideband amplitude modulation, transversal filter equalizers, data scrambling, and active compensation for phase instability.
The development of improved computer algorithms is considered for calculating earth satellite orbital trajectories by optimum selection of the analytical method that minimizes the number of perturbative acceleration computations for a given accuracy. A variation of parameter algorithm considering the equation of motion for a satellite proved superior for the geosynchronous orbit.
Methods for analyzing the stability of satellites are discussed. The subjects considered are: (1) time elements, (2) stabilization by external energy corrections, and (3) long term global solutions for the synchronous satellite. A set of canonical two-body elements referred to as Delaunay-similar elements is presented. In contrast to the classical Delaunay theory which has time as the independent variable, the D-S theory uses an independent variable which is a generalized true anomaly. The numerical integration of the canonical perturbation equations of these elements is developed.
An analytical and experimental program is described, for studying design techniques for optimizing the conversion efficiency of klystron amplifiers, and to utilize these techniques in the development and fabrication of an X-band 4 kW cw klystron, for use in satellite-borne television broadcast transmitters. The design is based on a technique for increasing the RF beam current by using the second harmonic space charge forces in the bunched beam. Experimental analysis was also made of a method to enhance circuit efficiency in the klystron cavities. The design incorporates a collector which is demountable from the tube to facilitate multistage depressed collector experiments employing an axisymmetric, electrostatic collector for linear beam microwave tubes.
A computer program is described which can be used to study the feasibility of conducting relativity experiments on a wide range of hypothetical space missions, and a few applications are presented for solar probes which approach the Sun within 0.25 to 0.35 AU. It is assumed that radio ranging data are available from these spacecraft, and that accuracies on the order of 15 meters can be achieved. This is compatible with current accuracies of ranging to Mariner spacecraft. At this level of accuracy, the range data are sensitive to a number of effects, and for this reason it has been necessary to include a total of up to 23 parameters in the feasibility studies, even though there are only two parameters of real interest in the relativity experiments.
Modifications eliminate contaminant substances from pump fluid during operation, which are principal causes of torpidity on evaporative surface. Diffusion pump is also acting as still. Resulting 100 percent vigorous working surface provides much greater molecular throughput and greatly improved efficiency.
Antenna has beam efficiency of 96 percent. Configuration is compact and relatively inexpensive.
The design, development, and test results are reported for an experimental PPM focused, traveling-wave tube that produces 235 watts of CW RF power over 85 MHz centered at 12.080 GHz. The tube uses a coupled cavity RF circuit with a velocity taper for greater than 30 percent basic efficiency. Overall efficiency of 51 percent is achieved by means of a nine stage depressed collector designed at NASA Lewis Research Center. This collector is cooled by direct radiation to deep space.
Attempts made to raise the efficiency of solar cells for space use are reported. The Helios, violet, and non-reflective cells were studied and it was concluded that the maximum practical efficiency of silicon solar cells is between 17 and 20%.
A detailed theoretical analysis of an n-on-p graded band-gap Al(x)Ga(1-x)As-GaAs solar cell yields a maximum air mass zero power conversion efficiency of 17% compared to 9% for a similar GaAs cell. The analysis includes surface and bulk minority carrier recombination, junction recombination current, spectrally varying surface reflection, and series resistance loss. The maximum efficiency is determined for a surface recombination velocity of 10,000 cm/sec and hole and electron diffusion lengths of 2.1 and 7.6 microns, respectively. The improved efficiency is primarily due to a built-in electric field, caused by the band-gap gradation, accelerating photogenerated holes toward the p-n junction. This field reduces the surface and bulk recombination of the holes, and thereby enhances their collection.
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A description is given of a six-arm conical scanner which was selected to provide a continuous line-of-sight scan. Two versions of the instrument are considered. The two versions differ in their weight. The weight of the heavy version is 600 lbs. A light weight design which employs beryllium and aluminum optical components weighs only 350 lbs. A multiplexer and analog-to-digital converter are to be incorporated into the design. Questions of instrument performance are also discussed.
Variations in temperatures used in experimental processing and their effect on the resulting solar cell performance parameters were investigated. Diffusion temperature variation results in a fairly distinct optimum cell performance for diffusion temperatures in the immediate vicinity of 850 C. An additional effort was also devoted to redesign of the matallization gridline pattern for both minimum light blockage and minimum fill factor alteration due to series resistance. Efforts on improvement of tantalum oxide antireflection coatings were undertaken. Fifty 2 cm x 2 cm cells having a range of thicknesses have been submitted as the first sample group. These cells were processed under conditions tentatively identified during this first contractual quarter's experiments as being optimal for resulting cell performance.