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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 1,207 records · Page 67

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NASA NTRS1975

Optimizing airport runway improvement program - A dynamic programming approach

In order to reduce the air traffic delay in the terminal area, an immediate remedy is to increase airport capacity by an expansion of the existing runway system. The runway expansion program is often limited by budgetary constraints; the expensive facilities for a long-term improvement cannot be built at once. When a runway improvement strategy is being considered for a longer planning horizon, the investiment decision depends upon the interrelations of its composite periods. The problem, therefore, is to determine how time factor and investment decisions interact to yield an optimal improvement scheme that meets demand at a minimum cost. With this objective in mind, a dynamic programming methodology is employed to determine the optimal planning scheme. Also, an example runway improvement problem is tested to illustrate how a dynamic programming model is practical in actual application.

Yu, J. C.↗

NASA NTRS1977

Some comments on series solutions

The use of power series and truncated power series in the MACSYMA system for algebraic manipulation is illustrated. Algebraic and differential equations are solved using Taylor series or asymptotic series. Deficiencies of the current scheme are noted, and remedies suggested.

Fateman, R. J.↗

NASA NTRS1977

Institutional and environmental aspects of geothermal energy development

Until recently, the majority of work in geothermal energy development has been devoted to technical considerations of resource identification and extraction technologies. The increasing interest in exploiting the variety of geothermal resources has prompted an examination of the institutional barriers to their introduction for commercial use. A significant effort was undertaken by the Jet Propulsion Laboratory as a part of a national study to identify existing constraints to geothermal development and possible remedial actions. These aspects included legislative and legal parameters plus environmental, social, and economic considerations.

Citron, O. R.↗

NASA NTRS1977

Present-day plate motions

A data set comprising 110 spreading rates, 78 transform fault azimuths and 142 earthquake slip vectors was inverted to yield a new instantaneous plate motion model, designated RM2. The mean averaging interval for the relative motion data was reduced to less than 3 My. A detailed comparison of RM2 with angular velocity vectors which best fit the data along individual plate boundaries indicates that RM2 performs close to optimally in most regions, with several notable exceptions. On the other hand, a previous estimate (RM1) failed to satisfy an extensive set of new data collected in the South Atlantic Ocean. It is shown that RM1 incorrectly predicts the plate kinematics in the South Atlantic because the presently available data are inconsistent with the plate geometry assumed in deriving RM1. It is demonstrated that this inconsistency can be remedied by postulating the existence of internal deformation with the Indian plate, although alternate explanations are possible.

Minster, J. B.↗

NASA NTRS1979

Observations on streamwise vortices in laminar and turbulent boundary layers

The frequent but often unsuspected presence of streamwise vortices in nominally two dimensional laminar and turbulent boundary layers and some of their consequences are described. Since there is no body of systematic information on streamwise vortices imbedded in boundary layers, a number of issues concerning their occurrence and behavior are discussed in the form of a set of succinct observations. Desirable experimental and numerical research to remedy the current lack of knowledge is recommended.

Morkovin, M. V.↗

NASA NTRS1979

Anisotropies in the fluxes of Pioneer 10 protons

One-hour-averaged fluxes of 1.8- to 2.15-MeV protons observed by the LET2 detector on Pioneer 10 on the inbound trajectory showed anisotropies attributable to corotation of Jupiter's magnetodisc only when Pioneer was near the dipole equator. Most of the time the anisotropy greatly exceeded the value expected from corotation. Gradients in the distribution function can be used to account for this excess anisotropy, but the amount of gradient required is unacceptably large by 1-2 orders of magnitude. If they were taken as real, these gradients would predict almost complete disappearance of these protons from Jupiter's magnetosphere in a matter of hours. The remedy is to introduce into the model of the distribution function proton flow along field lines away from the equator into both the southern and the northern hemisphere. The parallel flux at the southernmost latitudes reached by Pioneer can reach 25% of the product of proton density and velocity, i.e., 25% of the maximum possible.

Northrop, T. G.↗

NASA NTRS1980

Scheduling Algorithm for Mission Planning and Logistics Evaluation (SAMPLE). Volume 1: User's guide

An interactive computer program for automatically generating traffic models for the Space Transportation System (STS) is presented. Information concerning run stream construction, input data, and output data is provided. The flow of the interactive data stream is described. Error messages are specified, along with suggestions for remedial action. In addition, formats and parameter definitions for the payload data set (payload model), feasible combination file, and traffic model are documented.

Dupnick, E.↗

NASA NTRS1980

Rotordynamic Instability Problems in High-Performance Turbomachinery

Diagnostic and remedial methods concerning rotordynamic instability problems in high performance turbomachinery are discussed. Instabilities due to seal forces and work-fluid forces are identified along with those induced by rotor bearing systems. Several methods of rotordynamic control are described including active feedback methods, the use of elastometric elements, and the use of hydrodynamic journal bearings and supports.

Source record↗

NASA NTRS1980

Field experiences with rotordynamic instability in high-performance turbomachinery

Two field situations illustrate the consequences of rotordynamic instability in centrifugal compressors. One involves the reinjection of produced gas into a North Sea oil formation for the temporary extraction of crude. The other describes on-shore compressors used to deliver natural gas from off-shore wells. The problems which developed and the remedies attempted in each case are discussed. Instability problems resulted in lost production, extended construction periods and costs, and heavy maintenance expenditures. The need for effective methods to properly identify the problem in the field and in the compressor design stage is emphasized.

Doyle, H. E.↗

NASA NTRS1979

Space applications of superconductivity - High field magnets

The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

Fickett, F. R.↗

NASA NTRS1978

Analysis of long-term ionizing radiation effects in bipolar transistors

The ionizing radiation effects of electrons on bipolar transistors have been analyzed using the data base from the Voyager project. The data were subjected to statistical analysis, leading to a quantitative characterization of the product and to data on confidence limits which will be useful for circuit design purposes. These newly-developed methods may form the basis for a radiation hardness assurance system. In addition, an attempt was made to identify the causes of the large variations in the sensitivity observed on different product lines. This included a limited construction analysis and a determination of significant design and processes variables, as well as suggested remedies for improving the tolerance of the devices to radiation.

Stanley, A. G.↗

NASA NTRS1979

Field studies of the electrification of thunderstorms

Many theories have been advanced to explain the development of electric fields in thunderstorms, culminating in lightning, but thorough appraisal of these has been hampered by the lack of reliable and comprehensive observational data on the electrical characteristics, microphysical properties and dynamical behavior of the storms. A major field experiment (the Thunderstorm Research International Project) has been in progress for three years, in an effort to remedy this deficiency, and this paper describes some of this work and the results emanating from it. Major tools in this investigation are: an instrumented aircraft capable of penetrating the clouds; dual-Doppler and fast scanning radars; field-change and precipitation-recording networks; and an acoustic system for reconstructing the location of points on the lightning channels. The early results indicate a strong correlation between updraughts, precipitation and high fields. Circumstantial evidence points towards the presence of ice as being crucial to rapid field growth.

Christian, H.↗

NASA NTRS1980

Space motion sickness - Skylab revisited

Biomedical findings in the area of space motion sickness of the Skylab missions are reviewed and compared with the results of laboratory simulations. The motion sickness experiences of the three Skylab crews are related, and it is pointed out that of the nine astronauts, four were not sick at all, and of the five who were sick, only two vomited. In addition, it is noted that soon after recovery all five were immune in a provocative test based on the generation of cross-coupled angular accelerations while they executed head movements during rotation, in which they had manifested symptoms before the flight. Is is concluded that the findings indicate that susceptibility to motion sickness on earth is not a reliable predictor of susceptibility to motion sickness in orbit, and that free fall is a partial motion environment. Difficulties in dealing with motion sickness under operational conditions and the limitations of antimotion sickness remedies are noted.

Graybiel, A.↗

NASA NTRS1980

On deadlock detection in distributed systems

A hierarchically organized and a distributed protocol for deadlock detection in distributed databases are presented in a previous study Menasce and Muntz (1979). In this paper, it is shown that the distributed protocol is incorrect, and possible remedies are presented. However, the distributed protocol remains impractical because 'condensations' of 'transaction-wait-for' graphs make graph updates difficult to perform. Delayed graph updates cause the occurrence of false deadlocks in this as well as in some other deadlock detection protocols for distributed systems. The performance degradation that results from false deadlocks depends on the characteristics of each protocol.

Gligor, V. D.↗

NASA NTRS1980

RFI prevention for colocated antennas

Potential radio frequency interference problems related to the colocation of antennas for the Mark 4-A Deep Space network are analyzed. Cases discussed include effects of S-band uplinks on X-band downlinks and S-band downlinks, planetary radar at Goldstone, future X-band uplink, radiometer measurements, Search for Extraterrestrial Intelligence instrument, and radio astronomy projects. Remedial actions are suggested.

Peng, T. K.↗

NASA NTRS1981

Algorithm for rapid integration of turbulence model equations on parabolic regions

While developing a three-dimensional boundary layer program using a standard parabolic matching scheme, the author has found computing time with the Wilcox-Rubesin (1979) two-equation turbulence model to be very lengthy. The long computing time occurs because converged solutions are possible only when very small streamwise steps are taken. The proposed remedy reduces computing time by increasing the maximum permissible step size.

Wilcox, D. C.↗

NASA NTRS1981

Flight performance of SEASAT-1 attitude control system

The paper describes the attitude control flight performance of SEASAT-A, (launched in June 1978), until failure of the power subsystem terminated the mission in Oct. 1978. Information provided by the satellite pertained to surface winds and coastal storm activity, currents and wave heights, ocean topography and temperature. The ACS used three-axis momentum exchange and magnetic momentum containment and was set in a nose-down configuration. Attitude control sensing was via horizon sensors and attitude anomalies, resulting from solar interference with the sensors, is covered in detail. Remedial action was taken by reconfiguring the IR scanners, but failure resulted nevertheless. Recommendations for similar future missions include consideration of the effect of light sources and circuit time constants and scan rates. A block diagram of the ACS is included.

Beach, S. W.↗

NASA NTRS1981

Comments on the Leimanis solution of self-excited rigid body

An attempt is made to apply the solutions contained in a book by Leimanis (1965), which includes the Bodewadt solution, to the performance assessment of the Galileo spacecraft during spin up and spin down maneuvers. Because the Galileo is not precisely symmetric, however, the Bodewadt solution fails to achieve the desired accuracy for useful analysis. It is noted that in the case of the Leimanis solution, the analytic results are incorrect for theoretical reasons. In order to remedy this situation, analytic solutions are developed which satisfy the criterion of high accuracy and provide a useful analytic tool for the performance assessment and maneuver analysis of the Galileo spacecraft and many similar near symmetric spinning spacecraft. Simulation results suggest the relative accuracies of the Bodewadt solution and the author's solution, while the restricted regions of validity of the Leimanis solution are clearly indicated.

Longuski, J. M.↗