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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1933

Comparison of Three Methods for Calculating the Compressive Strength of Flat and Slightly Curved Sheet and Stiffener Combinations

This report gives a comparison of the accuracy of the three methods for calculating the compressive strength of flat sheet and stiffener combinations such as occur in stressed-skin or monocoque structures for aircraft. Of the three methods based upon various assumptions with regard to the interaction of sheet and stiffener, the method based upon mutual action of the stiffener and an effective width as a column gave the best agreement with the results of the tests. An investigation of the effect of small curvature resulted in the conclusion that the compressive strength of the curved panels is, for all practical purposes, equal to the strength of flat panels except for thick sheet where non-uniform curvature throughout the length may cause the strength of the curved panel to be 10 to 15 percent less than that of a corresponding flat panel.

STRESSED SKIN↗
NASA NTRS1969

Determination of the absolute contours of optical flats

Emersons procedure is used to determine true absolute contours of optical flats. Absolute contours of standard flats are determined and a comparison is then made between standard and unknown flats. Contour differences are determined by deviation of Fizeau fringe.

Primak, W.↗
NASA NTRS1972

Low-cost fabrication and direct bond installation of flat, single-curvature and compound-curvature ablative heat shield panels

Procedures for low cost fabrication and direct bond installation of flat, single curved, and compound curvature ablative heat shields on a DC-3 aircraft are discussed. The panel sizes and attachment locations are identified. In addition to the bonding of the four contoured panels, two flat panels were bonded to the nearly flat, lower surface of the center wing section. The detailed requirements and objectives of the investigation are described.

Norwood, L. B.↗
NASA NTRS1972

Investigation of forming curved ablative panels from flat panels for space shuttle

The purpose of this study was to determine the feasibility of reforming flat ablative panels to a curved configuration. The study indicated that if the panels could be shaped to a radius of 2.54 m (100 in.) then 88.7% of the surface area of the orbiter could be covered, and that if they could be shaped to a radius of 3.81 m (150 in.) then 77.2% of the surface could be covered. Two basic approaches were followed to determine the best method for forming the flat panels to a curved shape. The first was to determine if partially cured panels could be formed, allowing the forming heat cycle to complete the curing of the ablator. The second method was to form fully cured flat panels into the desired curvature through a secondary heat cycle. Measurements made on the panels during storage indicated that they continued to straighten out over time. This was attributed to residual stresses locked into the panels that had not been fully relaxed by the heat cycle.

Chandler, H. H.↗
NASA NTRS1973

Loading and heating of a large flat plate at Mach 7 in the Langley 8-foot high-temperature structures tunnel

Surface pressure and cold-wall heating rate distributions (wall-temperature to total-temperature ratio approximately 0.2) were obtained on a large, flat calibration panel at a nominal Mach number of 7 in an 8-foot high-temperature structures tunnel. Panel dimensions were 42.5 by 60.0 in. Test objectives were: (1) to map available flat-plate loading and heating provided by the facility and (2) to determine effectiveness of leading-edge bluntness, boundary-layer trips, and aerodynamic fences in generating a uniform, streamwise turbulent flow field over the test surface of a flat-sided panel holder.

Deveikis, W. D.↗
NASA NTRS1973

Laminar film boiling on inclined isothermal flat plates.

Laminar film boiling from an inclined flat plate has been investigated analytically. Using the singular perturbation scheme, the complete set of Navier-Stokes equations is solved. The zeroth-order perturbation coinciding with the boundary-layer equations for vertical flat plates governs the problem. The higher-order perturbations become important near the leading edge and for large values of the inclination angle from the vertical. The assumption of zero interfacial velocity shows that, except for fluids having large (rho x mu) ratios, the results can be predicted using the vertical flat plate results by defining a modified Grashof parameter containing a cos phi term. When the interfacial shear is considered, the solutions indicate that for fluids having large (rho x mu) ratios, the heat transfer rates will be larger (approximately 15% maximum) than those predicted by the simplified model using zero interfacial velocity. In general, the inclination decreases the rate of heat transfer as well as the rate of evaporation.

Nagendra, H. R.↗
NASA NTRS1973

An experimental investigation of a highly underexpanded sonic jet ejecting from a flat plate into a subsonic crossflow

The induced static pressures due to a highly underexpanded sonic jet ejecting normally from a flat plate into a subsonic crosswind have been investigated. These pressure data have been recorded on the flat plate for a range of nominal jet-to-free-stream dynamic-pressure ratios from 0 to 1000 at free-stream Mach numbers of 0.1, 0.2, 0.4, and 0.6. The static pressure data measured on the flat plate are presented and correlated based upon the Riemann shock geometry in the jet plume. This data correlation improves with increasing free-stream Mach number.

Shaw, C. S.↗
NASA NTRS1974

Design, development, fabrication and testing of high temperature Flat Conductor Cable (FCC)

The results are presented of a development program for a flat, 25-conductor signal cable and a flat, 3-conductor power cable. Flat cables employ conductors made of strips or flattened round copper conductors insulated with polyimide films. It is shown that conductor thickness ranges from 0.003 to 0.010 inch, and begins to soften and loose mechanical strength at temperatures above 200 C.

Rigling, W. S.↗
NASA NTRS1977

Flat-plate heat pipe

Flat plate (vapor chamber) heat pipes were made by enclosing metal wicking between two capillary grooved flat panels. These heat pipes provide a unique configuration and have good capacity and conductance capabilities in zero gravity. When these flat plate vapor chamber heat pipes are heated or cooled, the surfaces are essentially isothermal, varying only 3 to 5 C over the panel surface.

Marcus, B. D.↗
NASA NTRS1977

Reliability evaluation of hermetic dual in-line flat microcircuit packages

The relative strengths and weaknesses of 35 commonly used hermetic flat and dual in-line packages were determined and used to rank each of the packages according to a numerical weighting scheme for package attributes. The list of attributes included desirable features in five major areas: lead and lead seal, body construction, body materials, lid and lid seal, and marking. The metal flat pack and multilayer integral ceramic flat pack and DIP received the highest rankings, and the soft glass Cerdip and Cerpak types received the lowest rankings. Loss of package hermeticity due to lead and lid seal problems was found to be the predominant failure mode from the literature/data search. However, environmental test results showed that lead and lid seal failures due to thermal stressing was only a problem with the hard glass (Ceramic) body DIP utilizing a metal lid and/or bottom. Insufficient failure data were generated for the other package types tested to correlate test results with the package ranking.

Johnson, G. M.↗
NASA NTRS1977

Cratering motions and structural deformation in the rim of the Prairie Flat multiring explosion crater

Cratering motions and structural deformation are described for the rim of the Prairie Flat multiring crater, 85.5 m across and 5.3 m deep, which was formed by the detonation of a 500-ton TNT surface-tangent sphere. The terminal displacement and motion data are derived from marker cans and velocity gages emplaced in drill holes in a three-dimensional matrix radial to the crater. The integration of this data with a detailed geologic cross section, mapped from deep trench excavations through the rim, provides a composite view of the general sequence of motions that formed a transiently uplifted rim, overturned flap, inverted stratigraphy, downfolded rim, and deformed strata in the crater walls. Preliminary comparisons with laboratory experimental cratering and with numerical simulations indicate that explosion craters of the Prairie Flat-type generated by surface and near-surface energy sources tend to follow predictable motion sequences and produce comparable structural deformation. More specifically, central uplift and multiring impact craters with morphologies and structures comparable to Prairie Flat are inferred to have experienced similar deformational histories of the rim, such as uplift, overturning, terracing, and downfolding.

Roddy, D. J.↗
NASA NTRS1979

LDEF transverse flat plate heat pipe experiment /S1005/

The paper describes the Transverse Flat Plate Heat Pipe Experiment. A transverse flat plate heat pipe is a thermal control device that serves the dual function of temperature control and mounting base for electronic equipment. In its ultimate application, the pipe would be a lightweight structure member that could be configured in a platform or enclosure and provide temperature control for large space structures, flight experiments, equipment, etc. The objective of the LDEF flight experiment is to evaluate the zero-g performance of a number of transverse flat plate heat pipe modules. Performance will include: (1) the pipes transport capability, (2) temperature drop, and (3) ability to maintain temperature over varying duty cycles and environments. Performance degradation, if any, will be monitored over the length of the LDEF mission. This information is necessary if heat pipes are to be considered for system designs where they offer benefits not available with other thermal control techniques, such as minimum weight penalty, long-life heat pipe/structural members.

Robinson, G. A., Jr.↗
NASA NTRS1979

Experiment on the turbulent boundary layer over convex walls and its recovery to flat-wall conditions

The experiments were performed at a ratio of the thickness at which velocity is 99% of the potential flow velocity to the surface radius of curvature of about 0.09 on a convex wall, where the curvature effects are strong. The data show that a flat-wall boundary layer is strongly affected by curvature only a few boundary layer thicknesses downstream of the start of convex curvature. On the other hand, in flow over a flat surface downstream of convex curvature, the effects of curvature persist downstream for ten or more boundary layer thicknesses. It appears that the boundary layer over a convex wall may have a multilayer character which is slow to return to normal, flat-plate equilibrium.

Gillis, J. C.↗
NASA NTRS1981

Suspension system for a wheel rolling on a flat track

An improved suspension system for an uncrowned wheel rolling on a flat track is presented. It is characterized by a wheel frame assembly including a wheel frame and at least one uncrowned wheel connected in supporting relation with the frame. It is adapted to be seated in rolling engagement with a flat track, a load supporting bed, and a plurality of flexural struts interconnecting the bed in supported relation with the frame. Each of said struts is disposed in a plane passing through the center of the uncrowned wheel surface along a line substantially bisecting the line of contact established between the wheel surface and the flat surface of the truck and characterized by a modulus of elasticity sufficient for maintaining the axis of rotation for the wheel in substantial parallelism with the line of contact established between the surfaces of the wheel and track.

Mcginness, H. D.↗
NASA NTRS1982

Confirmation of a conspiracy - Dual-band VLBI maps of the flat-spectrum radio source 2021 + 614

VLBI observations at 3.6 and 13 cm wavelengths of the flat-spectrum radio source 2021 + 614 reveal two components, separated by about 6.5 + or - 0.6 milli-arcseconds along a position angle of 36 deg + or - 6 deg. The dual-band observations show that the two components have spectral indices of opposite signs, indicating that, as for 0735 + 178 (Cotton et al. 1980), the flat spectrum of 2021 + 614 is a result of the superposition of spectra from individual components, each having a peaked spectrum, presumably due to incoherent electron synchrotron radiation. If this situation is typical, then there is too large a percentage of flat-spectrum sources for the individual components in each to have independent characteristics.

Wittels, J. J.↗
NASA NTRS1983

Turbulent boundary-layer flow and structure on a convex wall and its redeveloment on a flat wall

Although the number of data sets which show the effects of convex curvature on turbulence has increased in the last 10 years, the development of really good calculational models is being held back by a lack of reliable data. The pesent investigation is concerned with a set of experiments which provide a litle more information regarding the response of a boundary-layer flow to convex curvature. Careful measurements were conducted to show the response of the boudnary layer to a sudden change from flat wall to curvature, and from curvature to flat wall. It was found that curvature effects were clearly apparent one or two boundary-layer thicknesses downstream of the start of curvature, while the disappearance of the curvature effects on a flat wall was an extremely slow process.

Gillis, J. C.↗
NASA NTRS1985

A comparative study of spherical and flat-Earth geopotential modeling at satellite elevations

Flat-Earth and spherical-Earth geopotential modeling of crustal anomaly sources at satellite elevations are compared by computing gravity and scalar magnetic anomalies perpendicular to the strike of variably dimensioned rectangular prisms at altitudes of 150, 300, and 450 km. Results indicate that the error caused by the flat-Earth approximation is less than 10% in most geometric conditions. Generally, error increase with larger and wider anomaly sources at higher altitudes. For most crustal source modeling applications at conventional satellite altitudes, flat-Earth modeling can be justified and is numerically efficient.

Parrott, M. H.↗
NASA NTRS1985

Application of the finite element method in the calculation of transmission loss of flat and curved panels

This investigation represents an extension of a study of Roussos (1985) who considered the noise transmission loss of a rectangular plate in an infinite baffle. Roussos, who employed an analytical formulation, considered an unstiffened plate. While it is difficult to consider stiffeners by means of analytical methods, the difficulties can be avoided by employing a finite element procedure. For this reason, the present study is concerned with the implementation of a finite element method. The representation of the panel transmission loss is discussed, and the determination of the panel motion by means of the finite element technique is described, taking into account an isotropic flat panel, the exciting force, an eigenvalue problem, the radiation pressure, a plate element, and a cylindrical shell element. Numerical results are considered for a flat panel, a curved panel, and a stiffened flat panel.

Koval, L. R.↗