SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Mathematical analysis calculates effects of transient pointing errors in solar dish collectors treating each pointing error separately. This approach considerably simplifies programming of simulation models for tracking drive, wind effects, and other design parameters.
Report describes method of verification of solar space heating and hot-water systems using similarity comparison, mathematical analysis, inspections, and tests. Systems, subsystems, and components were tested for performance, durability, safety, and other factors. Tables and graphs compliment test materials.
Cesium frequency standards are to be flown on the NTS-2 satellite which is a program conducted to develop technology and time standards for NAVSTAR Global Positioning System. Mission requirements for the thermal design of this frequency standard called for a low nominal temperature (15 C) and the removal of most of the heat generated by the standard from the spacecraft. The test program run to determine the thermal properties of the frequency standard is described. A simulator was constructed for these tests. Special mathematical analysis techniques were developed and were used to predict the thermal environment for different orbital conditions. Thermal vacuum tests of the flight frequency standard and the integrated spacecraft demonstrated the validity of this technique.
The basic concepts of influencing boundary layers are summarized, especially the prevention of flow detachment and the reduction of frictional resistance. A mathematical analysis of suction through a slit is presented with two parameters, for thickness and for shape of the boundary layer, being introduced to specify the flow's velocity profile behind the slit. An approximation of the shape parameter produces a useful formula, which can be used to determine the most favorable position of the slit. An aerodynamic example is given.
A mathematical analysis is performed to determine the relationship between the signal-to-noise ratio and the exposure time for an orbiting IR heterodyne spatial interferometer. The analysis includes consideration of the transformation of the interferogram to obtain the source angular intensity distribution so that the signal-to-noise ratio pertains to the angular distribution rather than to the interferogram. The analysis is applied to a number of known IR sources. The results presented show that an interferometer with a 30-m baseline using half-meter telescopes should be able to image a source such as IRC + 30219 with a signal-to-noise ratio of 10 in a total exposure time of less than an hour.
Report presents results of performance evaluation. Tests are part of continuing study of solar-heating systems and components for NASA and Department of Energy. Test data are presented as graphs and tables. Report also summarizes test procedures and mathematical analysis of results.
The paper discusses an SAR problem based on actual requirements set forth by NASA for a spaceborne application. The requirements for high resolution and high quality necessitate a data sampling rate of 7.5 MHz. For each data value 1,025 4-bit complex multiply + add operations are needed, which is equivalent to 7.7 GHz complex multiply + add operation rate. Since this rate is much too high for general purpose systems, a special-purpose device was sought. This paper discusses two architectures based on parallel operation of 1,025 identical cells, each of which is capable of performing arithmetic, storage, and several control operations. The operation rate in each device is only 7.5 MHz, which is quite manageable, especially with the help of a substantial degree of pipelining. A computational-mathematical analysis is used as a primary tool for evaluating the design and some of its tradeoffs. Two different approaches are discussed and compared; both are based on having 1,025 identical cells working in parallel, but differ in their dual approaches to the flow of data.
Current gathering rotating probe techniques were used to examine the envelope shape and power density profile of electron beams used in electron beam welding devices. The electron power density contours which determine the shape of the weld vapor cavity, penetration, and local heat distribution were considered. A mathematical analysis consistent with a rotating probe technique necessary to determine the current density distribution (assumed symmetrically radial) in a cross-section of the beam is provided. An explanation of the experimental technique for obtaining data, a BASIC language computer program to determine the current density from the data, and a study indicating the level of confidence to be associated with results obtained are also provided. An example of the application of the analysis to some experimental electron beam data is included.
The application of electrostatic technology to the protection of optical components in earth-mounted and satellite orbital systems has been investigated. Theory and experiment indicate it is quite practical to prevent dust deposition in an earth environment. A mathematical analysis indicates even better results should be obtained in an orbital vehicle.
Tetrahedral-lattice structure exhibits great complexity in mathematical analysis, and complexity quickly increases with number of elements. Solutions for static and dynamic behavior of structure obtained with model consisting of analogous structure with fewer repeating elements. Advantage of continuum models is analytic solutions can be obtained, either in closed form or in relatively-tractable Taylor series.
A mathematical analysis of a doubly-fed wound rotor machine used as a constant frequency generator is presented. The purpose of this analysis is to derive a consistent set of circuit equations which produce constant stator frequency and constant stator voltage. Starting with instantaneous circuit equations, the necessary rotor voltages and currents are derived. The model, thus obtained, is assumed to be valid, since the resulting relationships between mechanical power and active volt-amperes agrees with the results of others. In addition, the model allows for a new interpretation of the power flow in the doubly-fed generator.
A conceptual framework for the three-dimensional lee wave is given, and the severe limits of mathematical analysis as applied to the problem are described. It is shown that numerical simulation is the only feasible approach and some simulation results are displayed. These results are then compared with those from corresponding simulations of the much more familiar case of two-dimensional flow over a ridge. The problem of predicting in which portions of the lee wave clear air turbulence encounters are most probable is addressed. Here, idealized linear models are employed to establish a few tentative guidelines.
Mathematical analysis for digital data transmission calculates optimum number of binary error-correcting repeaters to install in given number of wideband channel links. Asymptotic results compared to computed numerical results.
A mathematical analysis of a doubly-fed wound rotor generator is presented. The constraints of constant stator voltage and frequency to the circuit equations were applied and expressions for the currents and voltages in the machine obtained. The derived variables are redefined as direct and quadrature components. In addition, the apparent (complex) power for both the rotor and the stator are derived in terms of these redefined components.
The wrinkling phenomenon in elasticity is mathematically defined and described as a special type of instability associated with the loss of hyperbolicity of the governing equations when some of the characteristic speeds of elastic wave propagation become imaginary. The developed criteria of wrinkling are applied to such structural elements as membranes, strings, soft shells, soft rods, and laminated material. The cause of wrinkling in these elements is due to compression in longitudinal directions that exceeds the through-the-thickness shear modulus. For elements with internal fluid flow the critical compression is reduced due to the destabilizing effect of the flow. The most effective mathematical analysis technique is a combination of tensor analysis and index notations.
Mathematical analysis of image sampling and interpolative reconstruction is summarized and extended to two dimensions for application to data acquired from satellite sensors such as the Thematic mapper and SPOT. It is shown that sample-scene phase influences the reconstruction of sampled images, adds a considerable blur to the average system point spread function, and decreases the average system modulation transfer function. It is also determined that the parametric bicubic interpolator with alpha = -0.5 is more radiometrically accurate than the conventional bicubic interpolator with alpha = -1, and this at no additional cost. Finally, the parametric bicubic interpolator is found to be suitable for adaptive implementation by relating the alpha parameter to the local frequency content of an image.
Report prepared for Marshall Space Flight Center summarizes recent advances in mathematical analysis of structural vibrations based on experimental data. Also includes summary of research by author as well as abstracts of technical reports and papers presented at meetings or otherwise published.
Comprehensive mathematical-analysis technique developed for array of solar-photovoltaic panels equipped with truncated-pyramid concentrators. Hollow pyramidal concentrator reflects Sunlight onto panel of photovoltaic cells. Comprehensive optical, thermal, and electrical analysis performed on array of units. Technique applicable, with modifications, to analysis and design of other multiple-cell reflecting photovoltaic systems.