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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 91 records · Page 5
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NASA NTRS1973

Theory of a ring laser

Development of a systematic formulation of the theory of a ring laser which is based on first principles and uses a well-known model for laser operation. A simple physical derivation of the electromagnetic field equations for a noninertial reference frame in uniform rotation is presented, and an attempt is made to clarify the nature of the Fox-Li modes for an open polygonal resonator. The polarization of the active medium is obtained by using a Fourier-series method which permits the formulation of a strong-signal theory, and solutions are given in terms of continued fractions. It is shown that when such a continued fraction is expanded to third order in the fields, the familiar small-signal ring-laser theory is obtained.

Menegozzi, L. N.↗
NASA NTRS1974

A reevaluation of the interrupter technique for airway resistance measurement

An attempt was made to obtain a better insight into the actual transient response of airway opening pressure (Pao) following rapid occlusion. With this knowledge it was hoped to be able to clarify the reason for the overestimations found by other investigators, and possibly to obtain a more accurate method of estimating alveolar pressure just prior to interruption. This would result in an improved method for estimating airway resistance. Use of an extrapolation method was found to provide an improved correlation between resistances determined by the interruptor technique and those found by the plethysmograph in normal subjects.

Jackson, A. C.↗
NASA NTRS1973

Convection effects on Skylab experiments M551, M552, and M553, phase C report

This report described an analysis of Skylab Experiments M551 (Metals Melting), M552 (Exothermic Brazing), and M553 (Sphere Forming). The primary objective is the study of convection in the molten metals and their attendant solidification theory. Particular attention is given to clarifying the effects of reduced gravity on molten metal flow and solidification. Based on an analysis of physical forces and solidification theory expected for ground-based and Skylab processing, low-g variations were predicted for each experiment. A comparison was then made with the Skylab results available to date. Both metallurgical analyses of other investigators and movies of ground-based and Skylab samples were utilized. Several low-g variations in Skylab processed materials were successfully predicted based on expected variations in physical forces and fluid convection. The same analysis also successfully predicted several features in the Skylab-processed materials which were identical to terrestrially-processed materials. These results are summarized in the conclusion section for each experiment.

Bourgeois, S. V.↗
NASA NTRS1974

Acceleration processes in the quasi-steady magnetoplasmadynamic discharge

The flow field characteristics within the discharge chamber and exhaust of a quasi-steady magnetoplasmadynamic (MPD) arcjet were examined to clarify the nature of the plasma acceleration process. The observation of discharge characteristics unperturbed by insulator ablation and terminal voltage fluctuations, first requires the satisfaction of three criteria: the use of refractory insulator materials; a mass injection geometry tailored to provide propellant to both electrode regions of the discharge; and a cathode of sufficient surface area to permit nominal MPD arcjet operation for given combinations of arc current and total mass flow. The axial velocity profile and electromagnetic discharge structure were measured for an arcjet configuration which functions nominally at 15.3 kA and 6 g/sec argon mass flow. An empirical two-flow plasma acceleration model is advanced which delineates inner and outer flow regions and accounts for the observed velocity profile and calculated thrust of the accelerator.

Boyle, M. J.↗
NASA NTRS1975

Verbalization and imagery in the process of formation of operator labor skills

Sensorimotor control tests show that mastering operational skills occurs under conditions that stimulate the operator to independent active analysis and summarization of current information with the goal of clarifying the signs and the integral images that are a model of the situation. Goal directed determination of such an image requires inner and external speech, activates and improves the thinking of the operator, accelerates the training process, increases its effectiveness, and enables the formation of strategies in anticipating the course of events.

Mistyuk, V. V.↗
NASA NTRS1974

A constructive model potential method for atomic interactions

A model potential method is presented that can be applied to many electron single centre and two centre systems. The development leads to a Hamiltonian with terms arising from core polarization that depend parametrically upon the positions of the valence electrons. Some of the terms have been introduced empirically in previous studies. Their significance is clarified by an analysis of a similar model in classical electrostatics. The explicit forms of the expectation values of operators at large separations of two atoms given by the model potential method are shown to be equivalent to the exact forms when the assumption is made that the energy level differences of one atom are negligible compared to those of the other.

Bottcher, C.↗
NASA NTRS1974

Stability analysis and compensation of a boost regulator with two-loop control

A useful stability measure has been demonstrated by Wester (1973) for switching regulators with a single feedback loop by applying the Nyquist criterion to the approximate loop gain determined by a time-averaging technique. This approach is extended and applied to the characterization, stability analysis, and compensation design of a switching regulator with two-loop control. The role and relative significance of each control loop is clarified on the basis of a description of circuit operation, and the major and minor loops are identified. In view of the inapplicability of linear feedback theory, describing functions of the feedback loops and power stage are derived, using small-signal analysis. Several phenomena revealed from an analysis of the major loop gain are discussed.

Wester, G. W.↗
NASA NTRS1974

Nuclear weapons tests and short-term effects on atmospheric ozone

Observations made when Nimbus 4 passed over a nuclear cloud about three hours after the bomb exploded are presented. Infrared and BUV measurements indicated that the atmospheric ozone level in the area of cloud was significantly less than in areas directly north and south of the cloud. It is noted, however, that it is not possible to state definitively that the ozone depletion was caused by nitrogen oxides released in the nuclear weapons test, and that further observations must be made to clarify the situation.

Miller, A. J.↗
NASA NTRS1975

Gamma ray astronomy

A survey of the instruments developed for gamma ray astronomy is given together with a brief summary of the current status of the observational results. These include the studies of galactic gamma ray emission, the diffuse, presumably extragalactic, gamma radiation, and localized gamma ray sources. The study of the spatial distribution of galactic gamma radiation is beginning to provide a new means for the study of galactic structure and dynamics. The diffuse emission may provide evidence of gamma ray emission in the cosmological past, although improved observations must be obtained before the picture can be clarified. The study of localized sources has shown NP0532, the Crab radio pulsar, to be a gamma ray pulsar also and strong emission from Vela may be due to supernova produced cosmic rays interacting with the remnant gas.

Kniffen, D.↗
NASA NTRS1974

Post-earthquake dilatancy recovery

Geodetic measurements of the 1964 Niigata, Japan earthquake and of three other examples are briefly examined. They show exponentially decaying subsidence for a year after the quakes. The observations confirm the dilatancy-fluid diffusion model of earthquake precursors and clarify the extent and properties of the dilatant zone. An analysis using one-dimensional consolidation theory is included which agrees well with this interpretation.

Scholz, C. H.↗
NASA NTRS1975

Theoretical models of magnetic field line merging. I

A review is presented of the models of magnetic field line merging defined as the process whereby plasma flows across a surface which separates regions including topologically different magnetic field lines. The models examined are characterized by uniform and antiparallel external magnetic fields. An attempt is made to simplify the presentation of the models, to clarify some doubtful mathematical points, or to extend the results to a different range of physical parameters. The models are described from a hydromagnetic point of view, with the configuration in any given case being determined by the boundary conditions. It is shown that the models developed by Sweet (1958), Parker (1957, 1963), Petschek (1964), Sonnerup (1970), and by Yeh and Axford (1970) are basically consistent, describing different aspects of the same problem; however, there is not a single model that would account for all the cases considered. The singular models and the compressible similarity models are physically not feasible.

Vasyliunas, V. M.↗
NASA NTRS1974

Microcircuit failure analysis using the SEM

The scanning electron microscope adds a new dimension to the knowledge that can be obtained from a failed microcircuit. When used with conventional techniques, SEM assists and clarifies the analysis, but it does not replace light microscopy. The most advantageous features for microcircuit analysis are long working distances and great depth of field. Manufacturer related failure modes of microcircuits are metallization defects, poor bonding, surface and particle contamination, and design and fabrication faults. User related failure modes are caused by abuse, such as overstress. The Physics of Failure Procedure followed by the Astrionics Laboratory in failure analysis is described, which is designed to obtain maximum information available from each step.

Nicolas, D. P.↗
NASA NTRS1975

Anomalous volume change of gramicidin A in ethanol solutions

Results of studies aimed at clarifying the failure of gramicidin A (GA) to sediment in early experiments are analyzed. In the present work, no sedimentation was observed in pure pentanol or ethanol, while normal sedimentation was observed in ethanol-water mixtures. It is concluded that GA exists in two conformations that differ in volume. Since the apparent specific volume in absolute ethanol sinks to its lowest values on increasing concentration, the GA molecule probably unfolds completely in conditions favorable for dimerization.

Derechin, M.↗
NASA NTRS1975

A General Simulator Using State Estimation for a Space Tug Navigation System

A general simulation program is presented (GSP) involving nonlinear state estimation for space vehicle flight navigation systems. A complete explanation of the iterative guidance mode guidance law, derivation of the dynamics, coordinate frames, and state estimation routines are given so as to fully clarify the assumptions and approximations involved so that simulation results can be placed in their proper perspective. A complete set of computer acronyms and their definitions as well as explanations of the subroutines used in the GSP simulator are included. To facilitate input/output, a complete set of compatable numbers, with units, are included to aid in data development. Format specifications, output data phrase meanings and purposes, and computer card data input are clearly spelled out. A large number of simulation and analytical studies were used to determine the validity of the simulator itself as well as various data runs.

Boland, J. S., III↗
NASA NTRS1975

Electrification: Mid-term (1985 - 2000)

Electrification, intended to provide a basis for the mid term period of the energy conservation program, was defined as a set of actions and/or policies that leads to an increasing proportion of total energy used in the form of electricity. The important actions within electrification are those with the greatest impacts (coal and nuclear), the greatest technological requirements (peak shaving and transmission) and the greatest response from the decision makers (economic health and growth of utilities in an era of increasing energy costs). The following areas were discussed: increased power generation from coal action, increased use of nuclear power action, improved operation of public utilities action, actions to be taken in industry, transportation and residential/commercial areas. The various ways in which electrification leads to energy conservation were clarified, and a number of specific recommendations relative to electrification were suggested.

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NASA NTRS1975

Waves in the vicinity of the magnetopause

Magnetic field data from the IMP 6 spacecraft are used in an attempt to clarify the magnetic field microstructure of the magnetopause. After discussing the problems in identifying the magnetopause, and the difficulties in determining normal components, the presence of waves in the vicinity of the magnetopause is discussed. The downstream magnetopause is considered and the presence of surface waves on the tail boundary is demonstrated.

Fairfield, D. H.↗
NASA NTRS1975

A spectral solar/climatic model

A summary is presented of pertinent research on solar activity variations and climate variations, together with the presentation of an empirical solar/climatic model that attempts to clarify the nature of the relationships.

Sleeper, H. P., Jr.↗
NASA NTRS1976

JPL Activated Carbon Treatment System (ACTS) for sewage

An Activated Carbon Treatment System (ACTS) was developed for sewage treatment and is being applied to a one-million gallon per day sewage treatment pilot plant in Orange County California. Activities reported include pyrolysis and activation of carbon-sewage sludge, and activated carbon treatment of sewage to meet ocean discharge standards. The ACTS Sewage treatment operations include carbon-sewage treatment, primary and secondary clarifiers, gravity (multi-media) filter, filter press dewatering, flash drying of carbon-sewage filter cake, and sludge pyrolysis and activation. Tests were conducted on a laboratory scale, 10,000 gallon per day demonstration plant and pilot test equipment. Preliminary economic studies are favorable to the ACTS process relative to activated sludge treatment for a 175,000,000 gallon per day sewage treatment plant.

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