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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

An experimental investigation of silicon wafer surface roughness and its effect on the pull-strength of plated metals

Plated silicon wafers with surface roughness ranging from 0.4 to 130 microinches, subjected to tensile pull-strength tests, were analyzed. Results show that the measured pull-strength of plated metals decrease with increasing silicon surface roughness, effecting a weakening of the cohesive strength of the wafer, possibly caused by microcracks or 'etch pits' in the silicon surface. The mean value of pull-strength for all wafers plated with the Ni-Cu-Cu sequence exceeded the required 450 g/0.02 sq cm, and at Ra = 0.4 microinches, the mean pull-strength for the Ni-Cu-Cu and Ni-Cu wafers were 2290 and 850 g/0.02 sq cm, respectively. The development of standardized methods for measuring contact pull-strength is suggested. These results may have some bearing on solar cell arrays problems.

Spiers, G. D.↗
NASA NTRS1985

Local heat-transfer measurements on a large, scale-model turbine blade airfoil using a composite of a heater element and liquid crystals

Local heat transfer coefficients were experimentally mapped along the midchord of a five-time-size turbine blade airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a mylar sheet with a layer of cholesteric liquid crystals, that change color with temperature, and a heater sheet made of a carbon-impregnated paper, that produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. The local heat transfer coefficients are presented for Reynolds numbers from 2.8 x 10 to the 5th power to 7.6 x 10 to the 5th power. Comparisons are made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code. Also, a leading edge separation bubble was revealed by thermal and flow visualization.

Hippensteele, S. A.↗
NASA NTRS1985

Local heat-transfer measurements on a large scale-model turbine blade airfoil using a composite of a heater element and liquid crystals

Local heat transfer coefficients were experimentally mapped along the midchord of a five-time-size turbine blade airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a mylar sheet with a layer of cholesteric liquid crystals, that change color with temperature, and a heater sheet made of a carbon-impregnated paper, that produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. The local heat transfer coefficients are presented for Reynolds numbers from 2.8 x 10 to the 5th power to 7.6 x 10 to the 5th power. Comparisons are made with analytical values of heat transfer coefficients obtained from the STANS boundary layer code. Also, a leading edge separation bubble was revealed by thermal and flow visualization.

Hippensteele, S. A.↗
NASA NTRS1996

A performance comparison of two small rocket nozzles

An experimental study was conducted on two small rockets (110 N thrust class) to directly compare a standard conical nozzle with a bell nozzle optimized for maximum thrust using the Rao method. In large rockets, with throat Reynolds numbers of greater than 1 x 10(exp 5), bell nozzles outperform conical nozzles. In rockets with throat Reynolds numbers below 1 x 10(exp 5), however, test results have been ambiguous. An experimental program was conducted to test two small nozzles at two different fuel film cooling percentages and three different chamber pressures. Test results showed that for the throat Reynolds number range from 2 x 10(exp 4) to 4 x 10(exp 4), the bell nozzle outperformed the conical nozzle. Thrust coefficients for the bell nozzle were approximately 4 to 12 percent higher than those obtained with the conical nozzle. As expected, testing showed that lowering the fuel film cooling increased performance for both nozzle types.

Arrington, Lynn A.↗
NASA NTRS1960

Investigation of Problems Associated with the Use of Alloyed Molybdenum Sheet in Structures at Elevated Temperatures

The results of an experimental study to explore the capabilities and limitations of thin Mo-0.5Ti molybdenum-alloy sheet for structural applications at high temperatures are presented. Evaluation tests at temperatures ranging from room temperature,to 3000 F were made on resistance-welded corrugated-core sandwiches that were coated with a commercially available oxidation resistant coating known as W-2 and on coated oxidation and tensile specimens. The performance of the corrugated-core sandwiches in compressive strength and static oxidation tests, tensile properties of the coated molybdenum sheet, and the life of the coated specimens in static oxidation tests are given. A description of the equipment and procedures utilized in performing the evaluation tests is included.

Mathauser, Eldon E.↗
NASA NTRS1959

Water-Landing Characteristics of a Reentry Capsule

Experimental and theoretical investigations have been made to determine the water-landing characteristics of a conical-shaped reentry capsule having a segment of a sphere as the bottom. For the experimental portion of the investigation, a 1/12-scale model capsule and a full-scale capsule were tested for nominal flight paths of 65 deg and 90 deg (vertical), a range of contact attitudes from -30 deg to 30 deg, and a full-scale vertical velocity of 30 feet per second at contact. Accelerations were measured by accelerometers installed at the centers of gravity of the model and full-scale capsules. For the model test the accelerations were measured along the X-axis (roll) and Z-axis (yaw) and for the full-scale test they were measured along the X-axis (roll), Y-axis (pitch), and Z-axis (yaw). Motions and displacements of the capsules that occurred after contact were determined from high-speed motion pictures. The theoretical investigation was conducted to determine the accelerations that might occur along the X-axis when the capsule contacted the water from a 90 deg flight path at a 0 deg attitude. Assuming a rigid body, computations were made from equations obtained by utilizing the principle of the conservation of momentum. The agreement among data obtained from the model test, the full-scale test, and the theory was very good. The accelerations along the X-axis, for a vertical flight path and 0 deg attitude, were in the order of 40g. For a 65 deg flight path and 0 deg attitude, the accelerations along the X-axis were in the order of 50g. Changes in contact attitude, in either the positive or negative direction from 0 deg attitude, considerably reduced the magnitude of the accelerations measured along the X-axis. Accelerations measured along the Y- and Z-axes were relatively small at all test conditions.

John R McGehee↗
NASA NTRS1958

Effect of Target Thickness on Cratering and Penetration of Projectiles Impacting at Velocities to 13,000 Feet Per Second

In order to determine the effects of target thickness on the penetration and cratering of a target resulting from impacts by high-velocity projectiles, a series of experimental tests have been run. The projectile-target material combinations investigated were aluminum projectiles impacting aluminum targets and steel projectiles impacting aluminum and copper targets. The velocity spectrum ranged from 4,000 ft/sec to 13,000 ft/sec. It has been found that the penetration is a function of target thickness provided that the penetration is greater than 20 percent of the target thickness. Targets of a thickness such that the penetration amounts to less than 20 percent of the thickness may be regarded as quasi-infinite. An empirical formula has been established relating the penetration to the target thickness and to the penetration of a projectile of the same mass, configuration, and velocity into a quasi- infinite target. In particular, it has been found that a projectile can completely penetrate a target whose thickness is approximately one and one-half times as great as the penetration of a similar projectile into a quasi-infinite target. The diameter of a crater has also been found to be a function of the target thickness provided that the target thickness is not greater than the projectile length in the case of cylindrical projectiles and not greater than two to three times the projectile diameter in the case of spherical projectiles.

Kinard, William H.↗
NASA NTRS1999

Configuration Aerodynamics: Past - Present - Future

The Configuration Aerodynamics (CA) element of the High Speed Research (HSR) program is managed by a joint NASA and Industry team, referred to as the Technology Integration Development (ITD) team. This team is responsible for the development of a broad range of technologies for improved aerodynamic performance and stability and control characteristics at subsonic to supersonic flight conditions. These objectives are pursued through the aggressive use of advanced experimental test techniques and state of the art computational methods. As the HSR program matures and transitions into the next phase the objectives of the Configuration Aerodynamics ITD are being refined to address the drag reduction needs and stability and control requirements of High Speed Civil Transport (HSCT) aircraft. In addition, the experimental and computational tools are being refined and improved to meet these challenges. The presentation will review the work performed within the Configuration Aerodynamics element in 1994 and 1995 and then discuss the plans for the 1996-1998 time period. The final portion of the presentation will review several observations of the HSR program and the design activity within Configuration Aerodynamics.

Wood, Richard M.↗
NASA NTRS1995

Recent Developments in the Use of Liquid Crystal Coatings for Full-Surface Shear Stress Vector Measurements

Under normal white-light illumination and oblique observation, liquid crystal coating (LCC) color-change response to shear depends on both shear stress magnitude as well as the direction of the applied shear relative to the observer's line of sight. These color-change responses were quantified by subjecting a LCC to a wall-jet shear flow and measuring scattered-light spectra using a fiber optic probe and spectrophotometer. At any fixed shear stress magnitude, the maximum color change was measured when the shear vector was aligned with and directed away from the observer; changes in the relative in-plane view angle to either side of this vector/observer aligned position resulted in symmetric Gaussian reductions in measured color change. For this vector/observer aligned orientation, color change was found to scale linearly with increasing shear stress magnitude over an eight-fold range. Based on these results, a surface shear stress vector measurement methodology, involving multiple oblique-view observations of the test surface, was formulated. In the present paper, the experimental approach and data analysis procedure required to extend this vector measurement methodology to full-surface applications will be outlined and progress towards demonstrating this areal capability will be reviewed.

Reda, D. C.↗
NASA NTRS1996

Clusters of DNA damage induced by ionizing radiation: formation of short DNA fragments. II. Experimental detection

The basic 30-nm chromatin fiber in the mammalian cell consists of an unknown (possibly helical) arrangement of nucleosomes, with about 1.2 kb of DNA per 10-nm length of fiber. Track-structure considerations suggest that interactions of single delta rays or high-LET particles with the chromatin fiber might result in the formation of multiple lesions spread over a few kilobases of DNA (see the accompanying paper: W.R. Holley and A. Chatterjee, Radiat. Res. 145, 188-199, 1996). In particular, multiple DNA double-strand breaks and single-strand breaks may form. To test this experimentally, primary human fibroblasts were labeled with [3H]thymidine and exposed at 0 degrees C to X rays or accelerated nitrogen or iron ions in the LET range of 97-440 keV/microns. DNA was isolated inside agarose plugs and subjected to agarose gel electrophoresis under conditions that allowed good separation of 0.1-2 kb size DNA. The bulk of DNA remained in the well or migrated only a small distance into the gel. It was found that DNA fragments in the expected size range were formed linearly with dose with an efficiency that increased with LET. A comparison of the yield of such fragments with the yield of total DNA double-strand breaks suggests that for the high-LET ions a substantial proportion (20-90%) of DNA double-strand breaks are accompanied within 0.1-2 kb by at least one additional DNA double-strand break. It is shown that these results are in good agreement with theoretical calculations based on treating the 30-nm chromatin fiber as the target for ionizing particles. Theoretical considerations also predict that the clusters will contain numerous single-strand breaks and base damages. It is proposed that such clusters be designated "regionally multiply damaged sites." Postirradiation incubation at 37 degrees C resulted in a decline in the number of short DNA fragments, suggesting a repair activity. The biological significance of regionally multiply damaged sites is presently unknown.

Non-NASA Center↗
NASA NTRS1958

Water Landing Characteristics of a Reentry Capsule

Experimental and theoretical investigations have been made to determine the water-landing characteristics of a conical-shaped reentry capsule having a segment of a sphere as the bottom. For the experimental portion of the investigation, a 1/12-scale model capsule and a full-scale capsule were tested for nominal flight paths of 65 deg and 90 deg (vertical), a range of contact attitudes from -30 deg to 30 deg, and a full-scale vertical velocity of 30 feet per second at contact. Accelerations were measured by accelerometers installed at the centers of gravity of the model and full-scale capsules. For the model test the accelerations were measured along the X-axis (roll) and Z-axis (yaw) and for the full-scale test they were measured along the X-axis (roll), Y-axis (pitch), and Z-axis (yaw). Motions and displacements of the capsules that occurred after contact were determined from high-speed motion pictures. The theoretical investigation was conducted to determine the accelerations that might occur along the X-axis when the capsule contacted the water from a 90 deg flight path at a 0 deg attitude. Assuming a rigid body, computations were made from equations obtained by utilizing the principle of the conservation of momentum. The agreement among data obtained from the model test, the full-scale test, and the theory was very good. The accelerations along the X-axis, for a vertical flight path and 0 deg attitude, were in the order of 40g. For a 65 deg flight path and 0 deg attitude, the accelerations along the X-axis were in the order of 50g. Changes in contact attitude, in either the positive or negative direction from 0 deg attitude, considerably reduced the magnitude of the accelerations measured along the X-axis. Accelerations measured along the Y- and Z-axes were relatively small at all test conditions.

John R McGehee↗
NASA NTRS2012

Aerodynamic Effects of Simulated Ice Accretion on a Generic Transport Model

An experimental research effort was begun to develop a database of airplane aerodynamic characteristics with simulated ice accretion over a large range of incidence and sideslip angles. Wind-tunnel testing was performed at the NASA Langley 12-ft Low-Speed Wind Tunnel using a 3.5 percent scale model of the NASA Langley Generic Transport Model. Aerodynamic data were acquired from a six-component force and moment balance in static-model sweeps from alpha = -5deg to 85deg and beta = -45 deg to 45 deg at a Reynolds number of 0.24 x10(exp 6) and Mach number of 0.06. The 3.5 percent scale GTM was tested in both the clean configuration and with full-span artificial ice shapes attached to the leading edges of the wing, horizontal and vertical tail. Aerodynamic results for the clean airplane configuration compared favorably with similar experiments carried out on a 5.5 percent scale GTM. The addition of the large, glaze-horn type ice shapes did result in an increase in airplane drag coefficient but had little effect on the lift and pitching moment. The lateral-directional characteristics showed mixed results with a small effect of the ice shapes observed in some cases. The flow visualization images revealed the presence and evolution of a spanwise-running vortex on the wing that was the dominant feature of the flowfield for both clean and iced configurations. The lack of ice-induced performance and flowfield effects observed in this effort was likely due to Reynolds number effects for the clean configuration. Estimates of full-scale baseline performance were included in this analysis to illustrate the potential icing effects.

Broeren, Andy P.↗
NASA NTRS2011

Report on Recent Upgrades to the Curved Duct Test Rig at NASA Langley Research Center

The Curved Duct Test Rig (CDTR) is an experimental facility that is designed to assess the acoustic and aerodynamic performance of aircraft engine nacelle liners in close to full scale. The test section is between 25% and 100% of the scale of aft bypass ducts of aircraft engines ranging in size from business jet to large commercial passenger jet. The CDTR has been relocated and now shares space with the Grazing Flow Impedance Tube in the Liner Technology Facility at NASA Langley Research Center. As a result of the relocation, research air is supplied to the CDTR from a 50,000 cfm centrifugal fan. This new air supply enables testing of acoustic liner samples at up to Mach 0.500. This paper documents experiments and analysis on a baseline liner sample, which the authors had analyzed and reported on prior to the move to the new facility. In the present paper, the experimental results are compared to those obtained previously in order to ensure continuity of the experimental capability. Experiments that take advantage of the facility s expanded capabilities are also reported. Data analysis features that enhance understanding of the physical properties of liner performance are introduced. The liner attenuation is shown to depend on the mode that is incident on the liner test section. The relevant parameter is the mode cut-on ratio, which determines the angle at which the sound wave is incident on the liner surface. The scattering of energy from the incident mode into higher order, less attenuated modes is demonstrated. The configuration of the acoustic treatment, in this case lined on one surface and hard wall on the opposite surface, is shown to affect the mode energy redistribution.

Gerhold, Carl H.↗
NASA NTRS1975

The application of 'strain range partitioning method' to torsional creep-fatigue interaction

The method of strain range partitioning was applied to a series of torsional fatigue tests conducted on tubular 304 stainless steel specimens at 1200 F (649 C). Creep strain was superimposed on cycling strain, and the resulting strain range was partitioned into four components; completely reversed plastic shear strain followed by creep strain, creep strain followed by plastic strain and completely reversed creep strain. Each strain component was related to the cyclic life of the material. The paper describes the experimental procedure used to achieve strain partitioning and the torsional test results are compared to those obtained from axial tests. The damaging effects of the individual strain components were expressed by a linear life fraction rule. The shear strain plastic component showed the least detrimental factor when compared to creep strain reversal by plastic strain. In the latter case, a reduction of torsional fatigue life in the order of magnitude of 1.5 was observed.

Zamrik, S. Y.↗
NASA NTRS1993

Experimental and analytical investigation of dynamic characteristics of extension-twist-coupled composite tubular spars

The results from a study aimed at improving the dynamic and aerodynamic characteristics of composite rotor blades through the use of extension-twist coupling are presented. A set of extension-twist-coupled composite spars was manufactured with four plies of graphite-epoxy cloth prepreg. These spars were noncircular in cross-section design and were therefore subject to warping deformations. Three different cross-sectional geometries were developed: D-shape, square, and flattened ellipse. Three spars of each type were fabricated to assess the degree of repeatability in the manufacturing process of extension-twist-coupled structures. Results from free-free vibration tests of the spars were compared with results from normal modes and frequency analyses of companion shell-finite-element models. Five global modes were identified within the frequency range from 0 to 2000 Hz for each spar. The experimental results for only one D-shape spar could be determined, however, and agreed within 13.8 percent of the analytical results. Frequencies corresponding to the five global modes for the three square spars agreed within 9.5, 11.6, and 8.5 percent of the respective analytical results and for the three elliptical spars agreed within 4.9, 7.7, and 9.6 percent of the respective analytical results.

Lake, Renee C.↗
NASA NTRS1975

Flexible rotor balancing by the influence coefficient method: Multiple critical speeds with rigid or flexible supports

Experimental tests were conducted to demonstrate the ability of the influence coefficient method to achieve precise balance of flexible rotors of virtually any design for operation through virtually any speed range. Various practical aspects of flexible-rotor balancing were investigated. Tests were made on a laboratory quality machine having a 122 cm (48 in.) long rotor weighing 50 kg (110 lb) and covering a speed range up to 18000 rpm. The balancing method was in every instance effective, practical, and economical and permitted safe rotor operation over the full speed range covering four rotor bending critical speeds. Improved correction weight removal methods for rotor balancing were investigated. Material removal from a rotating disk was demonstrated through application of a commercially available laser.

Tessarzik, J. M.↗
NASA NTRS1983

A class of nonideal solutions. 2: Application to experimental data

Functions for the representation of the thermodynamic properties of nonideal solutions were applied to the experimental data for several highly nonideal solutions. The test solutions were selected to cover both electrolyte behavior. The results imply that the functions are fully capable of representing the experimental data within their accuracy over the whole composition range and demonstrate that many nonideal solutions can be regarded as members of the defined class of nonideal solutions.

Zeleznik, F. J.↗
NASA NTRS1982

Calibration of solar cells by the reference cell method - The spectral mismatch problem

The calibration of solar cells by means of solar simulators and calibrated reference cells has always been faced with the problem of errors due to source spectral irradiance mismatch and cell spectral response mismatch. A general expression is derived in this paper to enable calculation of mismatch error. The information required to make this calculation is the relative spectra responses of the test and reference cells, and the relative spectral irradiance of the simulator (over the spectral range defined by cell response). The spectral irradiance of the solar standard is assumed given. Experimental results are presented.

Seaman, C. H.↗