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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Satellite networks for education

Satellite based educational networking is discussed with particular attention given to the potential uses of communications satellites to help meet educational needs in the United states. Four major subject areas were covered; (1) characteristics and structure of networks, (2) definition of pressures within educational establishment that provide motivation for various types of networks, (3) examination of current educational networking status for educational radio and television, instructional television fixed services, inter- and intra-state educational communication networks, computer networks, and cable television for education, and (4) identification of possible satellite based educational telecommunication services and three alternatives for implementing educational satellite systems.

Singh, J. P.↗
NASA NTRS1972

Application of space benefits to education

Information on the conducting of a teacher workshop is presented. This educational pilot project updated instruction material, used improved teaching techniques, and increased student motivation. The NASA/MSFC industrial facilities, and the displays at the Alabama Space and Rocket Center (ASRC) were key elements of the program, including a permanent exhibit, at the latter, on selected benefits accruing from the space program.

Dannenberg, K. K.↗
NASA NTRS1973

Finite deformation of elasto-plastic solids

A theoretical basis is established for analysis of finite deformation of metals. The observation that finite deformation of such elastoplastic materials may be viewed as a process rather than an event leads to derivation of a complete initial and boundary value problem distinguished by its quasilinear nature. This feature of the formulation motivates adoption of an incremental approach to numerical problem solving. Numerical solution capability is established for problems of plane stress and plane strain. The validity of the theory and numerical analysis is demonstrated by consideration of a number of problems of homogeneous finite deformation for which analytic solutions are available. Subsequently the analysis is employed for the investigation of necking in flat metal tensile bars. The results of this investigation provide the first full numerical solutions for tensile necking in plane stress and plane strain. In addition a basis is provided for assessment of the validity of stress-strain relations inferred from tensile test data.

Osias, J. R.↗
NASA NTRS1972

An investigation of the open-loop amplification of Reynolds number dependent processes by wave distortion

Analytical and experimental studies were initiated to determine if the response of a constant temperature hot wire anemometer to acoustic oscillations could serve as an analog to the response of the drop vaporization burning rate process to acoustic oscillations, and, perhaps, also as an analog to any Reynolds number dependent process. The motivation behind this study was a recent analytical study which showed that distorted acoustic oscillations could amplify the open-loop response of vaporization limited combustion. This type of amplification may be the cause of unstable combustion in liquid propellant rocket engines. The analytical results obtained for the constant temperature anemometer are similar in nature to those previously obtained for vaporization limited combustion and indicate that the response is dependent on the amount and type of distortion as well as other factors, such as sound pressure level, Mach number and hot wire temperature. Preliminary results indicate qualitative agreement between theory and experiment.

Purdy, K. R.↗
NASA NTRS1973

Study and development of a cryogenic heat exchanger for life support systems

A prototype cryogenic heat exchanger for removal of waste heat from a spacecraft environmental control life support system was developed. The heat exchanger uses the heat sink capabilities of the cryogenic propellants and, hence, can operate over all mission phases from prelaunch to orbit, to post landing, with quiescent periods during orbit. A survey of candidate warm fluids resulted in the selection of E-2, a fluorocarbon compound, because of its low freezing point and high boiling point. The final design and testing of the heat exchanger was carried out, however, using Freon-21, which is similar to E-2 except for its low boiling point. This change was motivated by the desire for cost effectiveness of the experimental program. The transient performance of the heat exchanger was demonstrated by an analog simulation of the heat sink system. Under the realistic transient heat load conditions (20 sec ramp from minimum to maximum Freon-21 inlet temperature), the control system was able to maintain the warm fluid outlet temperature within + or - 3 F. For a 20-sec ramp from 0 F to -400 F in the hydrogen inlet temperature, at maximum heat load, the warm fluid outlet temperature was maintained within + or - 7 F.

Soliman, M. M.↗
NASA NTRS1973

Differential Correction Schemes in Nonlinear Regression

Classical iterative methods in nonlinear regression are reviewed and improved upon. This is accomplished by discussion of the geometrical and theoretical motivation for introducing modifications using generalized matrix inversion. Examples having inherent pitfalls are presented and compared in terms of results obtained using classical and modified techniques. The modification is shown to be useful alone or in conjunction with other modifications appearing in the literature.

Decell, H. P., Jr.↗
NASA NTRS1972

Boiling from small cylinders.

Heat transfer is observed as a function of temperature on small horizontal wires in water and four organic liquids. When the wire radius is sufficiently small, the hydrodynamic transitions in the boiling curve disappear and the curve becomes monotonic. Three modes of heat removal are identified for the monotonic curve and described analytically: a natural convection mode, a mixed film boiling and natural convection mode, and a pure film boiling mode. Nucleate boiling does not occur on the small wires. The study was motivated by an interest in predicting the behavior of large heaters at low gravity. The application of the present results to such circumstances is therefore discussed. It is proposed that the peak and minimum heat fluxes will vanish at low gravity as well as on small wires.

Bakhru, N.↗
NASA NTRS1972

Satellite networks for education.

Consideration of satellite-based educational networking. The characteristics and structure of networks are reviewed, and pressures within the educational establishment that are providing motivation for various types of networks are discussed. A number of studies are cited in which networking needs for educational sectors and services are defined. The current status of educational networking for educational radio and television, instructional television fixed services, inter- and intrastate educational communication networks, computer networks, cable television for education, and continuing and proposed educational experiments using NASA's Applications Technology Satellites is reviewed. Possible satellite-based educational telecommunication services and three alternatives for implementing educational satellite systems are described. Some remarks are made concerning public policy aspects of future educational satellite system development.

Singh, J. P.↗
NASA NTRS1973

Coordinated adaptive filters for motion simulators.

A new approach to providing motion drive signals to a flight simulator utilizing coordinated adaptive filters is presented. Some motivation for the use of coordinated washout is discussed, along with conditions that determine the burden of coordination. The coordinated adaptive filters are derived, based on continuous steepest descent, and the application of the filters to simulated flight data is demonstrated.

Parrish, R. V.↗
NASA NTRS1973

Recursive ideal observer detection of known M-ary signals in multiplicative and additive Gaussian noise.

This paper presents the derivation of the recursive algorithms necessary for real-time digital detection of M-ary known signals that are subject to independent multiplicative and additive Gaussian noises. The motivating application is minimum probability of error detection of digital data-link messages aboard civil aircraft in the earth reflection multipath environment. For each known signal, the detector contains one Kalman filter and one probability computer. The filters estimate the multipath disturbance. The estimates and the received signal drive the probability computers. Outputs of all the computers are compared in amplitude to give the signal decision. The practicality and usefulness of the detector are extensively discussed.

Painter, J. H.↗
NASA NTRS1973

A hex on MPASK.

A class of multiple-phase amplitude-shift-keying (MPASK) signal sets based upon a hexagonal design is presented. The sets give slightly improved error probability performance over any other MPASK set thus far reported in the literature. The hexagonal signal set designs presented are motivated by a sphere-packing argument. Gray codes for binary data are considered, giving attention to questions regarding the 'best' impure Gray code that can be constructed for hexagonal signal sets.

Simon, M. K.↗
NASA NTRS1973

Assuring reliability program effectiveness.

An attempt is made to provide simple identification and description of techniques that have proved to be most useful either in developing a new product or in improving reliability of an established product. The first reliability task is obtaining and organizing parts failure rate data. Other tasks are parts screening, tabulation of general failure rates, preventive maintenance, prediction of new product reliability, and statistical demonstration of achieved reliability. Five principal tasks for improving reliability involve the physics of failure research, derating of internal stresses, control of external stresses, functional redundancy, and failure effects control. A final task is the training and motivation of reliability specialist engineers.

Ball, L. W.↗
NASA NTRS1974

Perturbation theory of structure in classical liquid mixtures: Application to metallic systems near phase separation

The partial structure factors of classical simple liquid mixtures near phase separation are dicussed. The theory is developed for particles interacting through pair potentials, and is thus appropriate both to insulating fluids, and also to metallic systems if these may be described by an effective ion-ion pair interaction. The motivation arose from consideration of metallic liquid mixtures, in which resistive anomalies have been observed near phase separation. A mean field theory correction appropriate to 3 pair potential for the effects of correlated motions in the reference fluid is studied. The work is cast in terms of functions which are closely related to the direct correlation functions of Ornstein and Zernike. The results are qualitatively in accord with physical expectations. Quantitative agreement with experiment seems to turn on the selection of the hard core reference potential in terms of the metallic effective pair potential. It is suggested that the present effective pair potentials are perhaps not properly used to calculate the metallic structure factors at long wavelength.

Henderson, R. L.↗
NASA NTRS1974

An investigation of the open-loop amplification of a Reynolds number dependent process by wave distortion

The response of a constant-temperature hot-wire anemometer to sinusoidal and distorted sinusoidal acoustic oscillations is examined. The output of the anemometer is dependent upon the Reynolds number of the flow over the wire. The response is a measure of the interaction between the anemometer output and the acoustic pressure in the neighborhood of the wire. It is an open-loop prediction of the characteristics of actual closed-loop operation of a system. If the open-loop response is large enough, unstable closed-loop operation is predicted. The study was motivated by a need to investigate the stability limits of liquid-propellant rockets when perturbed by pressure oscillations. The sinusoidal and distorted sinusoidal acoustic oscillations used for this study are the same as those characteristic of unstable rocket combustion. Qualitatively, the results are similar--the response of the system to pure sinusoidal acoustic vibration of the fluid surrounding the wire is small, even when the magnitude of the acoustic pressure is quite large; but the response can be increased by as much as an order of magnitude with respect to the sinusoidal case by the addition of distortion. The amplitude and phase of the distortion component, relative to the fundamental component, are the dominant factors in the increase in the response.

Ventrice, M. B.↗
NASA NTRS1974

Develop minimum thrustor control laws and select orbits for a geodesy drag-free satellite

The original motivation for studying control laws for pulse plasma systems was based on the improved life characteristics possible with pulse plasma jets. These pulse plasma units are relatively massive compared with cold gas thrustors. As a result, therefore, significant mass savings can be achieved by minimizing the the number of thrustors. The control laws, therefore, were developed for thrust available from two thrustors only. In a spinning satellite, these thrustors are sufficient to completely control the vehicle as long as the spin rate is sufficiently high for a given level of external disturbance. The thrustors are canted so that a component of each is along the plus and minus spin axis. The other component of each thrustor acts in the radial direction. It is sufficient to analyze the behavior in the plane of spin assuming a single thrustor.

Breakwell, J. V.↗
NASA NTRS1974

Enhancing simulation of efficiency with analytical tools

Some means of combining both computer simulation and anlytical techniques are indicated in order to mutually enhance their efficiency as design tools and to motivate those involved in engineering design to consider using such combinations. While the idea is not new, heavy reliance on computers often seems to overshadow the potential utility of analytical tools. Although the example used is drawn from the area of dynamics and control, the principles espoused are applicable to other fields. In the example the parameter plane stability analysis technique is described briefly and extended beyond that reported in the literature to increase its utility (through a simple set of recursive formulas) and its applicability (through the portrayal of the effect of varying the sampling period of the computer). The numerical values that were rapidly selected by analysis were found to be correct for the hybrid computer simulation for which they were needed. This obviated the need for cut-and-try methods to choose the numerical values, thereby saving both time and computer utilization.

Seltzer, S. M.↗
NASA NTRS1973

The growing importance of costs and ways to maintain cost control on a large program in today's competitive environment

Discussion of management techniques that make it possible to overcome inflationary and developmental cost rises while holding schedule and performance fixed in scientific space programs. The techniques reviewed pertain to high personnel motivation, continual review of contract rigidity for de facto modification by senior judgment, standardization vs design innovation, cooperative customer/contractor goal orientation vs task orientation, and deep real-time management visibility.

Newman, J. J.↗
NASA NTRS1973

Semiprecision calculations of electron-hydrogen resonances

Results of a calculation of the lowest (1 S) resonance below the first excitation threshold in electron-hydrogen scattering. This calculation is based on a precision Hylleraas calculation of the resonant wave function, combined with various reasonable physically motivated approximations for the nonresonant continuum. These approximations are basically the exchange- and polarized-orbital approximations. The values obtained, together with previous results obtained for the two higher (3 P and 1 D) resonances, are compared with the previous most accurate calculations, and some differences are noted.

Bhatia, A. K.↗