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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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Technique employs computer-controlled light-emitting diode (LED), precision machined mask, and analog-to-digital coverter (ADC). Computer turns on LED which floods masked face of tube. Intensity pattern, generated as tube is electromagnetically swept, is fed to ADC which controls tube calibration.
Circuit incorporates three-terminal current limiter (78M24) to increase overall reliability and to eliminate transistor burnouts resulting from shorted interconnection lines and other overloads. Fact-acting light emitting diodes across the limiters show status of transistor output circuits.
A display employing light emitting diodes (LED's) was developed to demonstrate the feasibility of such displays for presenting landing and navigation information to reduce the workload of general aviation pilots during IFR flight. The display consists of a paper tape reader, digital memory, control electronics, digital latches, and LED alphanumeric displays. A presentable digital countdown clock-timer is included as part of the system to provide a convenient means of monitoring time intervals for precise flight navigation. The system is a limited capability prototype assembled to test pilot reaction to such a device under simulated IFR operation. Pilot opinion indicates that the display is helpful in reducing the IFR pilots workload when used with a runway approach plate. However, the development of a compact, low power second generation display was recommended which could present several instructions simultaneously and provide information update capability. A microprocessor-based display could fulfill these requirements.
Conceptual optical sensor configurations for measuring the surface deformations of large, deployable space antennas are described. These antennas include precision deployable reflectors up to 30 meters diameter and 1000 GHz frequency and mesh deployable reflectors up to 100 meters diameter and 30 GHz frequency. For each representative antenna configuration, the surface deformation sensor provides continuous, real-time measurements at a sufficient number of sample points to be compatible with active surface control. Moreover, the sensor system does not interfere with the mechanical or microwave characteristics of either the antenna surface or the feed. For the applications considered, the sensor system consists of a central receiver ring containing six to ten long focal length, angle measuring instruments, each viewing a dedicated set of bright point targets at the antenna. The targets, either light emitting diodes or illuminated retroreflectors, are modulated to eliminate errors from spurious backgrounds. Very preliminary performance estimates indicate that the sensor system, using commerical grade components, can produce a 20th to a 30th wavelength accuracy (3 sigma).
The burn and burn/explode effects on aircraft structures were examined in a series of fifteen outdoor tests conducted to verify the results obtained in previous burn and explode tests of carbon/graphite composite samples conducted in a closed chamber, and to simulate aircraft accident scenarios in which carbon/graphite fibers would be released. The primary effects that were to be investigaged in these tests were the amount and size distribution of the conductive fibers released from the composite structures, and how these various sizes of fibers transported downwind. The structures included plates, barrels, aircraft spoilers and a cockpit. The heat sources included a propane gas burner and 20 ft by 20 ft and 40 ft by 60 ft JP-5 pool fires. The larger pool fire was selected to simulate an aircraft accident incident. The passive instrumentation included sticky paper and sticky bridal veil over an area 6000 ft downwind and 3000 ft crosswind. The active instrumentation included instrumented meteorological towers, movies, infrared imaging cameras, LADAR, high voltage ball gages, light emitting diode gages, microwave gages and flame velocimeter.
Carbon fiber sampling instruments were developed: passive collectors made of sticky bridal veil mesh, and active instruments using a light emitting diode (LED) source. These instruments measured the number or number rate of carbon fibers released from carbon/graphite composite material when the material was burned in a 10.7 m (35 ft) dia JP-4 pool fire for approximately 20 minutes. The instruments were placed in an array suspended from a 305 m by 305 m (1000 ft by 1000 ft) Jacob's Ladder net held vertically aloft by balloons and oriented crosswind approximately 140 meters downwind of the pool fire. Three tests were conducted during which released carbon fiber data were acquired. These data were reduced and analyzed to obtain the characteristics of the released fibers including their spatial and size distributions and estimates of the number and total mass of fibers released. The results of the data analyses showed that 2.5 to 3.5 x 10 to the 8th power single carbon fibers were released during the 20 minute burn of 30 to 50 kg mass of initial, unburned carbon fiber material. The mass released as single carbon fibers was estimated to be between 0.1 and 0.2% of the initial, unburned fiber mass.
Conventional pressure switch, fabricated by printed-circuit manufacturing techniques, can indicate when charge on battery departs from preset level. Membrane on switch is exposed to internal pressure of battery, which varies according to stored charge. When pressure varies from preset level, switch can turn on a light-emitting diode or similar indicator to warn user that battery is low.
Monitoring circuit responds to changes in resistance as little as 0.1 ohm. Has been used to detect defective wire-wrap connections during thermal and vibration tests. Defect is indicated to operator by light-emitting diode and by increase in count on a two-digit display.
A test apparatus is described for locating electrical shorts that is especially suited for use while an electrical circuit is being fabricated or assembled. A ring counter derives input pulses from a square wave oscillator. The outputs of the counter are fed through transistors to an array of light emitting diodes. Each diode is connected to an electrical conductor, such as a bus bar, that is to be tested. In the absence of a short between the electrical conductors the diodes are sequentially illuminated. When a short occurs, a comparator/multivibrator circuit triggers an alarm and stops the oscillator and the sequential energization of the diodes. The two diodes that remain illuminated identify the electrical conductors that are shorted.
An instrumentation system to provide a noncontact method for measurement of target positions was evaluated. The system employs two electro-optic camera units which give stereo information for use in determining three dimensional target locations. Specially developed, infrared sensitive photodetectors are used in the cameras to sense radiation from light emitting diode targets. Up to 30 of these targets can be monitored with a sampling rate of 312 Hz per target. An important part of the system is a minicomputer which is used to collect the camera data, sort it, make corrections for distortions in the electro-optic system, and perform the necesssary coordinate transformations. If target motions are restricted to locations in a plane which is perpendicular to a camera's optical axis, the system can be used with just one camera. Calibrations performed in this mode characterize accuracies in single camera operation. This information is also useful in determination of single camera contributions to total system errors. For this reason the system was tested in both the single camera and two camera (stereo) modes of operation.
Circuit identified malfunctioning photovoltaic array. Cell-failure detection circuit compares output of photovoltaic array to control cell. If any module fails, activates light-emitting diode. Circuit could also sound alarm.
Central array of light-emitting diodes displays status of 30 video cassette recorders (VCR's) monitoring integrated testing of Space Shuttle. Remote status panel linked to VCR's by one 37-conductor cable. Transistor/ transistor logic chips in interface circuit allow LED array to function without drawing power from VCR control circuits.
The minority carrier diffusion length Ln in the base or substrate region is an important parameter which governs a solar cell's performance. The present investigation is concerned with the development of a multiwavelength analyzer (MWA) technique for the nondestructive spatial testing of polycrystalline solar cells. The MWA method is based on the utilization of the short-circuit current generated by two or more light-emitting diodes (LEDs) operating at different wavelengths and modulated 180 deg out-of-phase. For a determination of Ln by the MWA technique, it is necessary to know the value of the absorption coefficient.
Images of retinas examined for characteristic patterns. Color photographs of retinas taken. Proper alinement of eye obtained by asking subject to gaze at light-emitting diode. "Red-eye" patterns in resulting color photographs examined by trained observers for signs of ocular defects. System used to check power of contact lenses and eyeglasses by taking photographs with these items in place.
Power-supply voltages quickly monitored by circuit equipped with light-emitting-diode (LED) display. Operator looking at display quickly spots whether power output voltage is above, below, or within acceptable limits. Tricolor LED displays high, low, and intermediate output voltages.
The SETS is a remote, non-contacting, high-accuracy tracking system for the measurement of deflection of models in the National Transonic Facility at Langley Research Center. The system consists of four electronically scanned image dissector trackers which locate the position of Light Emitting Diodes embedded in the wing or body of aircraft models. Target location data is recorded on magnetic tape for later 3-D processing. Up to 63 targets per model may be tracked at typical rates of 1280 targets per second and to precision of 0.02mm at the target under the cold (-193 C) environment of the NTF tunnel.
An optical proximity sensor for optically detecting an object within a predetermined detection volume is described. More specifically, an optical proximity sensor is disclosed having an illuminator assembly including lens and a plurality of light-emitting diodes located at first predetermined positions along the focal plane of the illuminator lens. A detector assembly including a detector lens and a plurality of photodiodes located at second predetermined positions along the focal plane of the detector lens is also provided. The two lenses are spaced apart a predetermined distance in order to define a predetermined detection volume. Additionally, a combination of optical proximity sensors, according to the invention, is disclosed wherein the sensors can be used in conjunction with a vehicle to provide a safety system for warning an operator when an object is within a volume defined by the proximity sensor combination.
GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency.