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At least 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Integrated Plastic Substrates for OLED Lighting

OLED lighting has immense potential as aesthetically pleasing, energy-efficient general illumination. Unlike other light sources, such as incandescents, fluorescents, and inorganic LEDs, OLEDs naturally emit over a large-area surface. They are glare free, do not need to be shaded, and are cool to the touch, requiring no heatsink. The best efficiencies and lifetimes reported are on par with or better than current forms of illumination. However, the cost for OLED lighting remains high – so much so that these products are not market competitive and there is very low consumer demand. We believe that flexible, plastic-based devices will highlight the advantages of aesthetically-pleasing OLED lighting systems while paving the way for lowering both materials and manufacturing costs. These flexible devices require new development in substrate and support technology, which was the focus of the work reported here. The project team, led by Sinovia Technologies, has developed integrated plastic substrates to serve as supports for flexible OLED lighting. The substrates created in this project would enable large-area, flexible devices and are specified to perform three functions. They include a barrier to protect the OLED from moisture and oxygen-related degradation, a smooth, highly conductive transparent electrode to enable large-area device operation, and a light scattering layer to improve emission efficiency. Through the course of this project, integrated substrates were fabricated, characterized, evaluated for manufacturing feasibility and cost, and used in white OLED demonstrations to test their impact on flexible OLED lighting. Our integrated substrates meet or exceed the DOE specifications for barrier performance in water vapor and oxygen transport rates, as well as the transparency and conductivity of the anode film. We find that these integrated substrates can be manufactured in a completely roll-to-roll, high throughput process and have developed and demonstrated manufacturing methods that can produce thousands of feet of material without defects. We have evaluated the materials and manufacturing costs of these films at scale and find that they meet the current and future cost targets for bringing down the cost of OLED lighting while enabling future roll-to-roll manufacturing of the complete device. And finally, we have demonstrated that the inherent light-scattering properties of our films enhance white OLED emission efficiency from 20% to 50% depending on the metric. This work has shown that these substrates can be created, manufactured, and will perform as needed to enable flexible OLED lighting to enter the marketplace.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Nanostructured Composite Alloys for Extreme Environments

Accumulative Roll Bonding was used to process nanolayered Cu/Nb and Zr/Nb composites with varying individual layer thickness. Mechanical tests show remarkable strength as the average layer thickness decreases. Relatively high strength is preserved even at elevated temperatures. Despite differences in texture between rolling paths (longitudinally rolled-RL and cross rolled-CR) Cu/Nb, flow stresses between the resultant materials were similar. In addition, thermal conductivity does not change significantly as the interface density increases. The alloys show remarkable resistance to irradiation damage at very high doses due to stability of the interfaces. The results on Zr/Nb indicate that liquid phase chemistry resulting from thermal spikes play an important role and should be taken into account when designing alloys for extreme environments.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Multilayer Electrodes with Metalized Polymer Current Collector for High-Energy Lithium-Ion Batteries with Extreme-Fast-Charging Capability

The pursuit of batteries capable of extreme fast charging (XFC), that also satisfy high energy and safety criteria, poses a significant challenge to current lithium-ion battery technologies. Additionally, the increasing demand for aluminum (Al) and copper (Cu) in electrification, and vehicle light weighting is driving these metals towards near-critical status in the medium term. This study introduced metalized polymer films by depositing an Al or Cu thin layer onto two sides of a polyethylene terephthalate (PET) film – named mPET/Al and mPET/Cu, as lightweight, cost-effective alternatives to traditional metal current collectors in LIBs. We have utilized current collectors that significantly reduce weight (by 73%), thickness (by 33%), and cost (by 85%) compared to traditional metal foil counterparts. We conducted an extensive evaluation of their mechanical and electrical properties, including in-plane and through-plane resistivities, affirming their suitability for the roll-to-roll battery manufacturing process. Additionally, a novel XFC testing protocol was employed to thoroughly assess the cells' (both half and full-cell) performance across various C-rates and under long-term tests. These advancements have the potential to enhance energy density to 280 Wh/kg at the electrode level under 10-minute charging at 6C. Through testing, including a novel XFC protocol across various C-rates and long-term cycling (up to 1000 cycles) in different cell configurations, we have demonstrated the superior performance of these metalized polymer films. Notably, mPET/Cu and mPET/Al foils exhibited comparable capacities to conventional cells under XFC, with the mPET cells showing a 27% improvement in energy density at 6C and maintaining significant energy density after 1000 cycles. This study underscored the potential of mPET foils to revolutionize the roll-to-roll battery manufacturing process and significantly advance the performance metrics of LIBs in EV applications. Moreover, our results suggest that there is potential to enhance the performance of mPET foils, especially mPET/Al, by optimizing the manufacturing process to achieve higher conductivity.

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS1962

NASA Scout ST-1 Flight-Test Results and Analyses, Launch Operations, and Test Vehicle Description

The first of a series of flight tests for the development of the four-stage, solid-propellant Scout vehicle was conducted at the NASA Wallops Station under the direction of the Langley Research Center. Vehicle designation for the test was NASA Scout ST-1. Performance characteristics of the vehicle and components were recorded during a high-altitude probe mission. Flight-simulation studies are presented and show that the accuracy of the guidance system during the flight was within control-system design specifications. The control system functioned normally during the flight with the exception of an overpowering of the reaction-control roll jets near burnout of the third-stage rocket motor. The resulting roll displacement of the vehicle is shown to have caused the monitor tracking radar which had been erroneously tracking a radar beacon in the vehicle on a side lobe to reorient to the major lobe of the receiving antenna. This tracking switch falsely indicated a violent turning maneuver on the monitor plot board and resulted in a hold-fire decision for the fourth-stage rocket motor. Although data for the final thrusting and coast phase of the flight were not obtained, the majority of the test objectives were achieved. In-flight thrust misalignment angles for the second- and third-stage rocket motors derived from control-system error data and for the first-stage motor determined from flight-simulation studies are presented. All rocket-motor thrust misalignment angles were well within the tolerances used for control-system design. Rocket-motor flight performance is presented, and velocity increments attained from the first three stages substantiated the predicted nominal performance. Operation of the rocket motors was satisfactory with the exception of high-level vibrations which were encountered during third-stage motor burning. Rolling moments which overpowered the reaction-control jets are also attributed to the burning characteristics of the third-stage motor. A discussion of the premature loss of the third-stage heat shield is given and shows that the heat-shield latching mechanism failed from pressure loads as the vehicle entered the transonic speed range. Although venting was provided to relieve the high negative pressures known to exist on the heat shield at these speeds, a field modification of the wiring tunnel had the same effect as opening the inside of the heat shield to ambient pressures. Consequently, the latching mechanism failed from pressure loads which were of about the same magnitude as the latching-mechanism yield loads. Skin temperatures were recorded at several locations on the vehicle and were generally in good agreement with theoretical values. Aerodynamic heating presented no problem during the flight since the maximum temperatures recorded during the flight were only about half the design values because of the high-launch-angle trajectory. Environmental vibrations recorded in the vicinity of the guidance package showed that no significant continuous amplitude levels above the general instrumentation noise level were present during first- and second-stage burning. Large vibration amplitudes were recorded during third-stage burning which coincided with the large roll disturbance experienced by the vehicle near burnout of the third-stage motor.

Scout Launch Vehicle↗
NASA NTRS1974

Preliminary results of flight tests of vortex attenuating splines

Flight tests have been conducted to evaluate the effectiveness of a wingtip vortex attenuating device, referred to as a spline. Vortex penetrations were made with a PA-28 behind a C-54 aircraft with and without wingtip splines attached and the resultant rolling acceleration was measured and related to the roll acceleration capability of the PA-28. Tests were conducted over a range of separation distances from about 5 nautical miles (n. mi.) to less than 1 n. mi. Preliminary results indicate that, with the splines installed, there was a significant reduction in the vortex induced roll acceleration experienced by the PA-28 probe aircraft, and the distance at which the PA-28 roll control became ineffective was reduced from 2.5 n. mi. to 0.6 n. mi., or less. There was a slight increase in approach noise (approximately 4 db) with the splines installed due primarily to the higher engine power used during approach. Although splines significantly reduced the C-54 rate of climb, the rates available with four engines were acceptable for this test program. Splines did not introduce any noticeable change in the handling qualities of the C-54.

Hastings, E. C., Jr.↗
NASA NTRS1974

Rotating raster generator

A rotating raster generator is provided which enables display of a television raster at any arbitrary roll angle. The generator includes four integrator circuits each of which receives a first voltage input corresponding to the sine or cosine of the desired roll angle and a second input comprising conventional horizontal or vertical sync pulses. The integrator circuits each comprise an operational amplifier and a capacitor connected for producing a ramp output having a rate of change proportional to the roll angle input, an electronic switch responsive to the sync input for resetting the integrator, and a summer that adds the ramp output of the integrator to the roll angle input so as to provide a zero-centered deflection control voltage.

Wagner, C. A.↗
NASA NTRS1974

Traction and film thickness measurements under starved elastohydrodynamic conditions

Traction measurements under starved elastohydrodynamic conditions were obtained for a point contact geometry. Simultaneous measurements of the film thickness and the locations of the inlet lubricant boundary were made optically. The thickness of a starved film for combination rolling and sliding conditions varies with the location of the inlet boundary in the same way found previously for pure rolling. A starved film was observed to possess greater traction than a flooded film for the same slide roll ratio. For a given slide roll ratio a starved film simply increases the shear rate in the Hertz region. The maximum shear rate depends on the degree of starvation and has no theoretical limit. Traction measurements under starved conditions were compared with flooded conditions under equivalent shear rates in the Hertz region. When the shear rates in the Hertz region were low and the film severely starved, the measured tractions were found to be much lower than expected.

Wedeven, L. D.↗
NASA NTRS1974

Stability and control characteristics at Mach numbers from 0.20 to 4.63 of a cruciform air-to-air missile with triangular canard controls and a trapezoidal wing

Investigations have been conducted in the Langley 8-foot transonic pressure tunnel and the Langley Unitary Plan wind tunnel at Mach numbers from 0.20 to 4.63 to determine the stability and control characteristics of a cruciform air-to-air missile with triangular canard controls and a trapezoidal wing. The results indicate that canards are effective in producing pitching moment throughout most of the test angle-of-attack and Mach number range and that the variations of pitching moment with lift for trim conditions are relatively linear. There is a decrease in canard effectiveness with an increase in angle of attack up to about Mach 2.50 as evidenced by the beginning of coalescence of the pitching-moment curves. At a Mach number above 2.50, there is an increase in effectiveness at moderate to high angles of attack. Simulated launch straps have little effect on the lift and pitch characteristics but do cause an increase in drag, and this increase in drag induces a rolling moment at a zero roll attitude where the straps cause an asymmetric geometric shape. The canards are not suitable devices for roll control and, at some Mach numbers and roll attitudes, are not effective in producing pure yawing moments.

Graves, E. B.↗
NASA NTRS1974

Results of full-scale vortex attenuation flight experiments

Flight tests have been conducted to evaluate the effectiveness of a wing-tip vortex attenuating device, referred to as a spline. Vortex penetrations were made with a PA-28 behind a C-54 aircraft with and without wing-tip splines attached, and the resultant rolling acceleration was measured and related to the roll acceleration capability of the PA-28. Tests were conducted over a range of separation distances from about 5 n mi to less than 1 n mi. Preliminary results indicate that, with the splines installed, there was a significant reduction in the vortex-induced roll acceleration experienced by the PA-28 probe aircraft, and the distance at which the PA-28 roll control became ineffective was reduced from 2.5 n mi to less than 1 n mi. Although splines significantly reduced the C-54 rate of climb, the rates available with four engines were acceptable for this test program.

Hastings, E. C., Jr.↗
NASA NTRS1972

Film handling procedures for Skylab S-056 experiment

In a simulation conducted August 28, 1972, two rolls of Type SO-212 film were rewound in the sensitometer darkroom preparatory to processing. The first roll contained approximately 500 feet of film exposed to a resolution target and was unloaded from a can. The second roll of 1000 feet, with about 600 feet advanced to the takeup side, was in a flight magazine. The downloading and rewinding of this second roll of film is described in detail.

Maas, K. A.↗
NASA NTRS1974

Static aeroelasticity and the flying wing, revisited

The roll dynamic behavior of some wing configurations is examined. Analysis shows that the static divergence instability which occurs for symmetrical or clamped sweptforward wings is modified by roll freedom. The instability found in the present highly idealized analysis is still of an aperiodic nature, but at a speed above the conventional divergence speed. The magnitude of this difference is seen to be a function of the ratio of the wing roll mass moment of inertia to the mass moment of inertia of the wing about the roll axis, and this difference may be quite significant.

Weisshaar, T. A.↗
NASA NTRS1974

The influence of wind shear on aerodynamic coefficients

The purpose of this study is to investigate the influence of wind shear on the lift, drag, roll and yaw moments of a wing in a horizontal wind gradient at various elevations and roll angles. The models of wind shear considered are those proposed by Leurs (1973) for atmospheric flow over horizontally homogeneous and uniform terrain. A general series solution for the distribution of lift along the wing span following the method of Houghton and Brock (1970) is employed to compute the loads and moments on the airfoil. Results of the computations indicate that wind shear can have a significant effect on the rolling and yawing moments of the wing of an aircraft flying with one wing low in the atmospheric boundary layer. These moments are directly influenced by the magnitude of the wind gradient in the neutral atmosphere reflected by the magnitude of the friction velocity. The effect of wind shear on lift and drag is negligible. Stability of the atmosphere tends to increase the magnitude of the rolling moment while decreasing its variation with elevation.

Frost, W.↗
NASA NTRS1972

Dynamic stability test results on an 0.024 scale B-1 air vehicle

Dynamic longitudinal and lateral-directional stability characteristics of the B-1 air vehicle were investigated in three wind tunnels at the Langley Research Center. The main rotary derivatives were obtained for an angle of attack range of -3 degrees to +16 degrees for a Mach number range of 0.2 to 2.16. Damping in roll data could not be obtained at the supersonic Mach numbers. The Langley 7 x 10 foot high speed tunnel, the 8 foot transonic pressure tunnel, and the 4 foot Unitary Plan wind tunnel were the test sites. An 0.024 scale light-weight model was used on a forced oscillation type balance. Test Reynolds number varied from 474,000/ft to 1,550,000/ft. through the Mach number range tested. The results showed that the dynamic stability characteristics of the model in pitch and roll were generally satisfactory up to an angle attack of about +6 degrees. In the wing sweep range from 15 to 25 degrees the positive damping levels in roll deteriorated rapidly above +2 degrees angle of attack. This reduction in roll damping is believed to be due to the onset of separation over the wing as stall is approached.

Beeman, R. R.↗
NASA NTRS1977

All sky pointing attitude control system

In a strapped-down gyroscope space vehicle attitude control system, a method and apparatus are provided for gyro drift and input axis misalignment error compensation employing a sun and a star tracker and preselected vehicle calibration maneuvers. The outputs of two-axis strapped-down gyroscopes nominally aligned with the optical axis of the sun and star trackers are measured to provide gyro drift calibration, roll, pitch and yaw axis scale factors and values corresponding to the degree of nonorthogonality between the roll axis and the pitch and yaw gyro input axes and the nonorthogonality of the roll and pitch axes relative to the yaw axis. The vehicle is then rolled and yawed through precomputed angles as modified by the calibrated data stored in a digital computer, and acquires a target without recourse to external references.

Lorell, K. R.↗
NASA NTRS1978

Characterization of the non axial thrust generated by large solid propellant rocket motors in three axis stabilized ascent

Nonaxial thrusts produced by solid rocket motors during three-axis stabilized attitude control have been determined from ascent experience on twenty three Burner II, Burner IIA and Block 5D-1 upper stage vehicles. A data base representing four different rocket motor designs (three spherical and one extended spherical) totaling twenty five three-axis stabilized firings is generated. Solid rocket motor time-varying resultant and lateral side force vector magnitudes, directions and total impulses, and roll torque couple magnitudes, directions, and total impulses are tabulated in the appendix. Population means and three sigma deviations are plotted. Existing applicable ground test side force and roll torque magnitudes and total impulses are evaluated and compared to the above experience data base. Within the spherical motor population, the selected AEDC ground test data consistently underestimated experienced motor side forces, roll torques and total impulses. Within the extended spherical motor population, the selected AEDC test data predicted experienced motor side forces, roll torques, and total impulses, with surprising accuracy considering the very small size of the test and experience populations.

Kosmann, W. J.↗
NASA NTRS1978

Entry dynamics performance predictions for Pioneer Venus probes

The scientific experiments planned for the Pioneer Venus entry probes require that the probes provide a stable platform at a controlled roll rate throughout the atmospheric phase of the mission. The 45-degree half-cone forebody common to both the small and large probe configurations provides a design which meets all stability and attitude requirements. The uncertainty in the dynamic stability parameter coupled with the possible variability of roll rate due to ablation induced roll torques could, however, result in slight angle of attack divergence in the transonic flight regime. Minimum roll rate requirements on the small probe are passively achieved by a vane mounted on the pressure-temperature sensing arm. The vane was sized to provide minimum dynamic disturbance.

Mccloy, R. D.↗
NASA NTRS1980

Kinematic correction for roller skewing

A theory of kinematic stabilization of rolling cylinders is developed for high-speed cylindrical roller bearings. This stabilization requires race and roller crowning to product changes in the rolling geometry as the roller shifts axially. These changes put a reverse skew in the rolling elements by changing the rolling taper. Twelve basic possible bearing modifications are identified in this paper. Four have single transverse convex curvature in the rollers while eight have rollers with compound transverse curvature composed of a central cylindrical band of constant radius surrounded by symmetric bands with both slope and transverse curvature.

Savage, M.↗
NASA NTRS1981

Dynamics of solid dispersions in oil during the lubrication of point contacts. Part 1: Graphite

A Hertzian contact was lubricated with dispersed graphite in mineral oils under boundary lubrication conditions. The contact was optically observed under pure rolling, combined rolling and sliding, and pure sliding conditions. The contact was formed with a steel ball on the flat surface of a glass disk. Photomicrographs are presented which show the distribution of the graphite in and around the contact. Friction and surface damage are also shown for conditions when the base oils are used alone and when graphite is added to the base oils. Under pure rolling and combined rolling and sliding conditions, it is found that, for low speeds, a graphite film can form which will separate the contacting surfaces. Under pure sliding conditions, graphite accumulates at the inlet and sweeps around the contact, but very little of the graphite passes through the contact. The accumulated graphite appears to act as a barrier which reduces the supply of oil available to the contact for boundary lubrication. Friction data show no clear short term beneficial or detrimental effect caused by addition of graphite to the base oil. However, during pure sliding, more abrasion occurs on the polished balls lubricated with the dispersion than on those lubricated with the base oil alone. All observations were for the special case of a highly-polished ball on a glass surface and may not be applicable to other geometries and materials, or to rougher surfaces.

Cusano, C.↗