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Results for “refinement”

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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Improvements of magnetic heads through the use of new and refined core materials

A process for making ferromagnetic films with high permeability and development of the technology for fabricating a magnetic head using these films are reported. An interim head was successfully built, tested, and delivered for evaluation and a process for sputtering high permeability films has been developed. Two heads with deposited pole tips have been tested and delivered. One had a 0.0001 inch gap and the other a 0.0003 inch gap. Both heads were boned with epoxy but served to test the geometry of the head design.

Source record↗
NASA NTRS1974

Grain refinement control in gas-shielded arc welding of aluminum tubing

When sections are being welded, operator varies pulse rate of power supply and simultaneously monitors signal on oscilloscope until rate is found which produces maximum arc gas voltage. Remainder of welding is performed with power supply set at this pulse rate, producing desired maximum weld puddle agitation and fine uniform weld of grain structure.

Iceland, W. F.↗
NASA NTRS1972

Refinement of the gravity field by satellite-to-satellite Doppler tracking.

The question of what resolution of the gravity field can be obtained from satellite-to-satellite Doppler tracking was investigated by performing least-squares adjustments of simulated Doppler data, solving for parameters describing the anomalous gravity field in various sized blocks. By examining the correlation between the adjusted parameters describing neighboring blocks, it was possible to judge whether a given set of data was capable of resolving blocks of a given size. Two concepts of satellite-to-satellite tracking are considered: the first involves two satellites near together in very low orbits, while the second uses geostationary satellites to track a single very low satellite. In either case, blocks 500 km on a side can be satisfactorily resolved from an orbital altitude of 700 km. From an altitude of 200 km, blocks 200 km on a side can be resolved. Because of the lower limit on altitude imposed by the presence of the earth's atmosphere, it does not appear that satellite-to-satellite Doppler tracking will be able to resolve features smaller than 200 km on a side.

Schwarz, C. R.↗
NASA NTRS1973

A refined analysis of composite laminates

The purpose of this paper is to develop a sufficiently accurate analysis, which is much simpler than exact three-dimensional analysis, for statics and dynamics of composite laminates. The governing differential equations and boundary conditions are derived by following a variational approach. The displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and rotary inertia are included. A procedure for obtaining the general solution of the above governing differential equations in the form of hyperbolic-trigonometric series is given. The accuracy of the present theory is assessed by obtaining results for free vibrations and flexure of simply supported rectangular laminates and comparing them with results from exact three-dimensional analysis.

Srinivas, S.↗
NASA NTRS1974

Sequential filter design for precision orbit determination and physical constant refinement

Earth-based spacecraft tracking data have historically been processed with classical least squares filtering techniques both for navigation purposes and for physical constant determination. The small, stochastic nongravitational forces acting on the spacecraft are described to motivate the use of sequential estimation as an alternative to the least squares fitting procedures. The stochastic forces are investigated both in terms of their effect on the tracking data and their influence on estimation accuracy. A flexible sequential filter design which leaves the existing trajectory, variational equations, data observable and partial computations undisturbed is described. A detailed filter design is presented that meets the precision demands and flexibility requirements of deep space navigation and of scientific problems.

Curkendall, D. W.↗
NASA NTRS1974

Refinement of the Goloseyev catalog point coordinates in the limb zone and determination of point coordinates on the back side of the moon

Lunar photography from Zond 6 showed half the side of the moon which is not visible from the earth, and this made it possible to construct a photogrammetric grid encompassing the entire Western Hemisphere and referenced to points of the visible side, whose coordinates were taken from the Goloseyev catalog. The problem was solved using two pictures taken from approximately 9000 km above the lunar surface. The photogrammetric grid was constructed by joint statistical analysis of the measurements of both pictures and the selenographic coordinates of the catalog points. A special algorithm was developed and a program compiled realizing the maximum likelihood method which permitted working with up to 120 catalog points simultaneously.

Krasikov, V. A.↗
NASA NTRS1974

Refinement in black chrome for use as a solar selective coating

Black chrome is significant as a solar selective coating because the current extensive use of black chrome in the electroplating industry as a durable decorative finish makes black chrome widely available on a commercial scale and potentially low in cost as a solar selective coating. Black-chrome deposits were modified by underplating with dull nickel or by being plated on rough surfaces. Both of these procedures increased the visible absorptance. There was no change in the infrared reflectance for the dull-nickel - black-chrome combination from that reported for the bright-nickel - black-chrome combination. However, the bright-nickel - black-chrome coating plated on rough surfaces indicated a slight decrease in infrared reflectance. As integrated over the solar spectrum for air mass 2, the reflectance of the dull-nickel - black-chrome coating was 0.077, of the bright-nickel - black-chrome coating plated on a 0.75-micron (30-microinch) surface was 0.070, of the bright-nickel - black-chrome coating plated on a 2.5 micron (100-microinch) surface was 0.064. The corresponding values for the bright-nickel - black-chrome coating on a 0.0125-micron (0.5-microinch) surface, two samples of black nickel, and two samples of Nextrel black paint were 0.132, 0.123, 0.133, and 0.033, respectively.

Mcdonald, G. E.↗