Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “deviated”

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.

At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

The improvement of star positions by photographic methods

A brief description is given of the new astrometric camera and of the program on which it is being employed. This is the photography of the southern sky so that each star appears on at least four overlapping plates. Sets of star coordinates measured on each plate are combined with a limited set of provisional meridian places to give an accurate set of relative star positions which are independent of the meridian system together with a set of residuals for each plate-star. The technique is based on a simple geometrical model of image formation on photographic plates. Current investigations are concerned with the elimination of sources of systematic deviation from this model.

Clube, S. V. M.↗
NASA NTRS1971

The problem of uniqueness in thermosphere dynamics

The unique solution of tidal wave propagation within the thermosphere depends on the boundary conditions of the model. It is shown that the radiation condition leads to such a unique solution. Any other boundary values give rise to deviations from the physical solution with unrealistic physical parameters in the environment of the boundaries. The thickness of these boundary layers with unrealistic solutions is a few scale heights below the upper boundary of the model and a few tens of scale heights above the lower boundary of the model.

Volland, H.↗
NASA NTRS1972

Effect of Reynolds number on overall performance of a 3.7-inch-diameter six-stage axial-flow compressor

A 9.4-centimeter (3.7-in.) diameter six-stage axial-flow compressor was tested in argon over a range of inlet pressures corresponding to a Reynolds number range of 30,600 to 160,000. The effect of Reynolds number on efficiency, pressure ratio, work input, maximum flow, and surge is shown. The Reynolds number effects are discussed in terms of changes in boundary-layer thickness, losses, and the resulting changes in throughflow velocity. Significant deviation was noted from the 0.2 power relation often used to express the variation of loss with Reynolds number.

Heidelberg, L. J.↗
NASA NTRS1972

Radiofrequency-sputtered coatings for lubrication system components and other complex surfaces

Irregularly shaped surfaces, such as lubrication system components (ball bearings, seals, gears, etc.), can be coated on all surfaces, including irregular shapes, when radiofrequency sputtering is used. When the specimen is properly located with respect to the sputtering target, the sputtered material covers the entire surface of the object irrespective of its geometrical configuration. An adherent, dense film is formed. The film thickness varies from 20 to 50 percent on, for example, a hearing cage or race depending on its geometry. When sputtered solid film lubricants such as molybdenum disulfide are used, a film thickness only of the order of 10 to the minus 7th power m (thousands of angstroms) is required at the contacting areas. It is only essential to determine the required film thickness at the critical areas in need of lubrication. The sections outside the areas to be lubricated fall within the thickness deviation range of 20 to 50 percent, which still constitutes a negligible change respect to tolerance requirements.

Spalvins, T.↗
NASA NTRS1972

Carpet plot data format

Analysis and interpretation of data is the crucial phase of the decision making process. The interplay between variables must be considered as to their relative significance upon the final result, and sometimes time-sensitive decisions must be made when actual events deviate from predicted information, such as Apollo 13. As the number of variables increases past say four, the traditional method of cross-plotting tends to break down, and digital/analog results cannot present a sharply defined method of analysis. A graphical system, the carpet plot, is presented in which an unlimited number of complicated relationships of variables can be evaluated.

Byrne, J. M.↗
NASA NTRS1972

Monte Carlo analysis of lobular gas-surface scattering in tubes applied to thermal transpiration

A model of rarefied gas flow in tubes was developed which combines a lobular distribution with diffuse reflection at the wall. The model with Monte Carlo techniques was used to explain previously observed deviations in the free molecular thermal transpiration ratio which suggest molecules can have a greater tube transmission probability in a hot-to-cold direction than in a cold-to-hot direction. The model yields correct magnitudes of transmission probability ratios for helium in Pyrex tubing (1.09 to 1.14), and some effects of wall-temperature distribution, tube surface roughness, tube dimensions, gas temperature, and gas molecular mass.

Smith, J. D.↗
NASA NTRS1970

Severe storms

The role of jet streams in the development of severe storms was analyzed. Local variations of flow resulting from rapid changes of geostrophic velocity along the air trajectory or inertial instability can produce cold advection. An analysis of meso-network data for 1968 and 1969 was performed. Although inertial instability was present in the network, local deviations in wind direction and cold advection were not detected.

Goldstein, M. G.↗
NASA NTRS1972

A Monte Carlo error analysis program for near-Mars, finite-burn, orbital transfer maneuvers

A computer program was developed which performs an error analysis of a minimum-fuel, finite-thrust, transfer maneuver between two Keplerian orbits in the vicinity of Mars. The method of analysis is the Monte Carlo approach where each off-nominal initial orbit is targeted to the desired final orbit. The errors in the initial orbit are described by two covariance matrices of state deviations and tracking errors. The function of the program is to relate these errors to the resulting errors in the final orbit. The equations of motion for the transfer trajectory are those of a spacecraft maneuvering with constant thrust and mass-flow rate in the neighborhood of a single body. The thrust vector is allowed to rotate in a plane with a constant pitch rate. The transfer trajectory is characterized by six control parameters and the final orbit is defined, or partially defined, by the desired target parameters. The program is applicable to the deboost maneuver (hyperbola to ellipse), orbital trim maneuver (ellipse to ellipse), fly-by maneuver (hyperbola to hyperbola), escape maneuvers (ellipse to hyperbola), and deorbit maneuver.

Green, R. N.↗
NASA NTRS1972

Aerodynamic parameters of the Navion airplane extracted from flight

An iterative method, which is characterized as a maximum-likelihood minimum-variance technique, was used to extract the aerodynamic parameters of a Navion airplane from flight data. The purposes were to compare the results with parameters obtained from wind-tunnel tests and with results obtained by analog matching the same data, and to develop techniques for application of the parameter extraction program. Results from the study showed that the parameter-extraction program can produce aerodynamic parameters which will permit close estimation of the aircraft time histories used in the extraction process. The program determined an estimate of the standard deviations of the states and parameters. These estimates were used to indicate how well the calculated states fit the flight data and the confidence in the values of the estimated parameters. The study also showed that the values of the parameters were affected by the data and mathematical model used during the extraction process. Because of the lack of confidence in the parameters extracted by use of some of the sets of data, several parameters were estimated by other methods. By using a combination of methods, a set of parameters which gave a fit to the data was obtained.

Suit, W. T.↗
NASA NTRS1972

Ocean color determination through a scattering atmosphere

Measurements made of the surface level albedo for ocean water containing various concentrations of phytoplankton indicate a strong correlation between wavelength dependent albedo ratios and phytoplankton chlorophyll concentration. To sense surface level albedo ratios from space platforms it is necessary to correct for the scattering and absorption properties of the atmosphere for the wavelengths in question. Atmospheric scattering models were constructed to calculate corrections at two wavelengths, 0.46 and 0.54 millimicrons. Assuming a natural background uncertainty in the aerosol optical depth of 0.1, it is found that the chlorophyll concentration may be determined to within one standard deviation of from 0.5 to 2.5 milligrams per cubic meter. By remotely sensing the aerosol optical depth to a greater accuracy it appears feasible to detect chlorophyll concentrations to uncertainty approaching 0.1 milligram per cubic meter.

Curran, R. J.↗
NASA NTRS1972

Planetary observations at millimeter wavelengths

Observations of the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn were made at 3.1 mm and 8.6 mm wavelengths with a 16-foot radio telescope between March and August, 1971. Absolute brightness temperature data are given. All errors are one standard deviation and include uncertainties in antenna gain calibration. The solar and lunar temperatures are in excellent agreement with published observations. The planetary measurements at 3.1 mm are consistently higher than previous results. The implications of higher temperatures with respect to existing atmospheric and surface models are discussed.

Ulich, B. L.↗
NASA NTRS1972

Space Shuttle Atmospheric ascent flight dynamics

The atmospheric ascent flight phase of the mated composite booster and orbiter is discussed. The composite recoverable space shuttle booster and orbiter exhibits unique flight control characteristics. This uniqueness results from large lifting surfaces and aerodynamic and structural assymetrics. An effective load relief technique reduces aerodynamic loads on both the booster and the orbiter. Reducing aerodynamic loads permits decreasing the structural weight of the lifting and stabilizing surfaces. An orbiter payload penalty is caused by trajectory deviations resulting from load relief. However, the net effect of an effective load relief technique is an increase in payload capability. Atmospheric launch dynamics investigations have been carried out for different configuration types, which include expendable, straight wing, delta wing, and ballistic recoverable boosters.

Patha, J. T.↗
NASA NTRS1972

Fault determinations in electroexplosive devices by nondestructive techniques

Several nondestructive test techniques were developed for electroexplosive devices. The bridgewire responds, when pulsed with a safe level current, by generating a characteristic heating curve. The response is indicative of the electrothermal behavior of the bridgewire-explosive interface. Bridgewires which deviate from the characteristic heating curve were dissected and examined to determine the cause of the abnormality. Deliberate faults were fabricated into squibs. The relationship of the specific abnormality and the fault associated with it is demonstrated.

Menichelli, V. J.↗
NASA NTRS1971

Analysis of ATS photographs using a specially designed electronic console

Measurements of cloud motion, cloud size, and growth rate were made on four days in the vicinity of rawin stations in the BOMEX network. These measurements were compared with the rawins and levels of best fit ranging from 980 to 250 mb were found. No correlation was found between cloud size and level of best fit. The magnitude of the vector difference between the cloud motion and wind at the level of best fit was as high as 15 knots for clouds with levels of best fit below the 500-mb level and 8 knots for clouds with levels of best fit above the 500-mb level. When cloud motion vectors with levels of best fit at or above the 500-mb level were compared with winds at the 300-mb level, the vector difference increased to as much as 16 knots or double the greatest minimum vector difference. A comparison between cloud motions and winds at the level of best fit showed that the clouds tended to move slightly faster than the observed winds and to move slightly to the left of the wind direction. Rate of growth appeared to influence whether clouds moved faster or slower than the wind. No relationship between cloud size and amount of deviation from the wind direction was observed.

Blackmer, R. H., Jr.↗
NASA NTRS1972

Comparison of Predicted and Experimental Heat-Transfer and Pressure-Drop Results for an Air-Cooled Plug Nozzle and Supporting Struts

A calculational procedure is presented to analyze the heat-transfer and fluid-flow characteristics of a convectively air -cooled plug-nozzle operating on an afterburning turbojet engine. Anderson's method was used to predict hot-gas static pressures in the supersonic stream with fully expanded flow (high nozzle-pressure ratios); the results were excellent. For low nozzle-pressure ratios, the flow was assumed to expand one-dimensionally and isentropically to the plug back pressure. Wall temperatures predicted using this latter pressure distribution agreed well with the wall temperatures predicted using the measured hot-gas pressures (maximum deviation was about 30 K (54 deg R)). Either an in tegral boundary-layer technique or a simple pipe-flow equation may be used to calculate convective heat transfer from the hot gas to the wall. The simple pipeflow equation results in the prediction of slightly higher wall temperatures than does the integral technique. Experimental wall temperatures were generally in good agreement with the two predicted wall temperature distributions. Excellent agreement was noted b etween measured and predicted coolant static-pressure distributions. The plug-coolant temperature rise was generally overpredicted by about 22.2 K (40 deg R); possible explanations are offered. Although an an alysis of the struts, which support the plug, was purposely kept simple, reasonable results were obtained. Potential flow over an ellipse was used to calculate hot-gas static pressure; the results were satisfactory.

Graber, E. J., Jr.↗
NASA NTRS1972

Pilot/vehicle control optimization using averaged operational mode and subsystem relative performance index sensitivities

A method is presented for designing optimal feedback controllers for systems having subsystem sensitivity constraints. Such constraints reflect the presence of subsystem performance indices which are in conflict with the performance index of the overall system. The key to the approach is the use of relative performance index sensitivity (a measure of the deviation of a performance index from its optimum value). The weighted sum of subsystem and/or operational mode relative performance index sensitivies is defined as an overall performance index. A method is developed to handle linear systems with quadratic performance indices and either full or partial state feedback. The usefulness of this method is demonstrated by applying it to the design of a stability augmentation system (SAS) for a VTOL aircraft. A desirable VTOL SAS design is one that produces good VTOL transient response both with and without active pilot control. The system designed using this method is shown to effect a satisfactory compromise solution to this problem.

Leininger, G. G.↗
NASA NTRS1972

Effects of interplanetary magnetic field azimuth on auroral zone and polar cap magnetic activity

During relatively quiet times in the period 1964-1968, AE is found to be greater when the interplanetary magnetic field (b sub IMF) is directed toward the sun in Jan., Feb., and Apr., and when B sub IMF is directed away from the sun in Oct. to Dec. Using Murmansk hourly H values and the AE components, AU and AL, it is shown that this sector dependence is present only in the negative H deviations. This observation supports the idea that negative bay magnitudes are determined chiefly by particle-produced ionization, while positive bay magnitudes are rather insensitive to increases in particle precipitation. The ratio of DP2-type magnetic activity in the southern polar cap to that in the northern polar cap is found to be greater by a factor of about 1.75 for B sub IMF toward the sun.

Burch, J. L.↗
NASA NTRS1972

Analysis of fatigue crack propagation

The correlation between fatigue crack propagation and stress intensity factor is analyzed. When determining fatigue crack propagation rate, a crack increment, delta a, and its corresponding increment in load cycles, delta N, are measured. Fatigue crack propagation must be caused by a shear and/or a normal separation mode. Both of these two processes are discrete if one looks at the atomic level. If the average deformation and fracture properties over the crack increments, delta a, can be considered as homogeneous, if the characteristic discrete lengths of sigma a, if the plastic zone size is small, and if a plate is thick enough to insure a plane strain case, da/dN is proportional to delta K squared. Any deviation of empirical data from this relation must be caused by the fact that one or more of these conditions are not satisfied. The effects of plate thickness and material inhomogeneity are discussed in detail. A shear separation mode of fatigue crack propagation is described and is used to illustrate the effects of material inhomogeneity.

Liu, H. W.↗