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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Test apparatus for locating shorts during assembly of electrical buses

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.

Deboo, G. J.↗
NASA NTRS1982

Optimum damping locations for structural vibration control

A technique for determining the optimum damper locations and damping rates for a flexible structure has been developed. Using a nonlinear-mathematical-programming algorithm, a diagonal damping matrix is determined such that specified modes have a prescribed modal damping ratio. The design objective is to minimize the total damping effort while constraining the modal damping ratio to be equal or greater than the prescribed amount. Additional constraints require the diagonal elements of the damping matrix to be positive which guarantees that all modes of the damped system will be stable. Results are shown for a uniform free-free beam.

Horner, G. C.↗
NASA NTRS1980

A study of optimum cowl shapes and flow port locations for minimum drag with effective engine cooling, volume 2

The listings, user's instructions, sample inputs, and sample outputs of two computer programs which are especially useful in obtaining an approximate solution of the viscous flow over an arbitrary nonlifting three dimensional body are provided. The first program performs a potential flow solution by a well known panel method and readjusts this initial solution to account for the effects of the boundary layer displacement thickness, a nonuniform but unidirectional onset flow field, and the presence of air intakes and exhausts. The second program is effectually a geometry package which allows the user to change or refine the shape of a body to satisfy particular needs without a significant amount of human intervention. An effort to reduce the cruise drag of light aircraft through an analytical study of the contributions to the drag arising from the engine cowl shape and the foward fuselage area and also that resulting from the cooling air mass flowing through intake and exhaust sites on the nacelle is presented. The programs may be effectively used to determine the appropriate body modifications or flow port locations to reduce the cruise drag as well as to provide sufficient air flow for cooling the engine.

Fox, S. R.↗
NASA NTRS1982

Utilization of LANDSAT multispectral data in geobotanical investigations: The location of ironstone gravel in the Sam Houston National Forest

Practical techniques were developed and evaluated for deriving geobotanical information from LANDSAT MSS data acquired for a test site in the Sam Houston National Forest near Cleveland, Texas where gravel deposits exist in sufficient quantity that economical extraction would be feasible. A correlation was shown between a single spectral class and the presence of ironstone gravel. Field data indicates that this class relates to upland pine which was probably under stress as the result of a prolonged drought which was in progress at the time of data acquisition. It is suggested that the subsurface gravel produces a soil which has less field capacity for water retention, causing early appearance of water stress in the surface vegetation over these soils. In all areas within the QMC formation where this class occurred, gravel was located when borings were made.

Cibula, W. G.↗
NASA NTRS1982

Feature Identification and Location Experiment

The Feature Identification and Location Experiment (FILE), which was flown on the second Space Shuttle flight to test a technique for real-time, autonomous classification of water, vegetation and bare land as well as clouds, snow and ice, senses earth radiation in spectral bands centered at 0.65 and 0.85 microns. The radiance ratio classification algorithm has successfully made automatic data selection decisions. A classification image obtained on the mission is providing data needed to evaluate the FILE algorithm and overall system performance.

Sivertson, W. E., Jr.↗
NASA NTRS1983

Flight test derived heating math models for critical locations on the orbiter during reentry

An analysis technique was developed for expanding the aerothermodynamic envelope of the Space Shuttle without subjecting the vehicle to sustained flight at more stressing heating conditions. A transient analysis program was developed to take advantage of the transient maneuvers that were flown as part of this analysis technique. Heat rates were derived from flight test data for various locations on the orbiter. The flight derived heat rates were used to update heating models based on predicted data. Future missions were then analyzed based on these flight adjusted models. A technique for comparing flight and predicted heating rate data and the extrapolation of the data to predict the aerothermodynamic environment of future missions is presented.

Hertzler, E. K.↗
NASA NTRS1983

A review of underwater acoustic systems and methods for locating objects lost at sea

Information related to the location of objects lost at sea is presented. Acoustic devices attached to an object prior to being transported is recommended as a homing beacon. Minimum requirements and some environmental constraints are defined. Methods and procedures for search and recovery are also discussed. Both an interim system and a more advanced system are outlined. Controlled acoustic emission to enhance security is the theme followed.

Lovelady, R. W.↗
NASA NTRS1984

Performance of alkaline battery cells used in emergency locator transmitters

The characteristics of battery power supplies for emergency locator transmitters (ELT's) were investigated by testing alkaline zinc/manganese dioxide cells of the type typically used in ELT's. Cells from four manufacturers were tested. The cells were subjected to simulated environmental and load conditions representative of those required for survival and operation. Battery cell characteristics that may contribute to ELT malfunctions and limitations were evaluated. Experimental results from the battery cell study are discussed, and an evaluation of ELT performance while operating under a representative worst-case environmental condition is presented.

Haynes, G. A.↗
NASA NTRS1983

Solar photovoltaic powered refrigerators/freezers for medical use in remote geographic locations

One of the obstacles preventing widespread immunication against disease is the virtual absence of reliable, low maintenance refrigeration systems for storage of vaccines in remote geographic locations. A system which consists of a solar photovoltaic cell array and an integrated refrigerator/freezer-energy storage unit is discussed herein. The array converts solar radiation into direct current (DC) electricity with no moving parts and no intermediate steps. A detailed description of the refrigeration system, its design and an analysis thereof, performance test procedures, and test results are presented. A system schematic is also provided.

Darkazalli, G.↗
NASA NTRS1984

Selection of actuator locations for static shape control of large space structures by heuristic integer programing

Orbiting spacecraft such as large space antennas have to maintain a highly accurate space to operate satisfactorily. Such structures require active and passive controls to mantain an accurate shape under a variety of disturbances. Methods for the optimum placement of control actuators for correcting static deformations are described. In particular, attention is focused on the case were control locations have to be selected from a large set of available sites, so that integer programing methods are called for. The effectiveness of three heuristic techniques for obtaining a near-optimal site selection is compared. In addition, efficient reanalysis techniques for the rapid assessment of control effectiveness are presented. Two examples are used to demonstrate the methods: a simple beam structure and a 55m space-truss-parabolic antenna.

Haftka, R. T.↗
NASA NTRS1984

Multipath induced errors in meteorological Doppler/interferometer location systems

One application of an RF interferometer aboard a low-orbiting spacecraft to determine the location of ground-based transmitters is in tracking high-altitude balloons for meteorological studies. A source of error in this application is reflection of the signal from the sea surface. Through propagating and signal analysis, the magnitude of the reflection-induced error in both Doppler frequency measurements and interferometer phase measurements was estimated. The theory of diffuse scattering from random surfaces was applied to obtain the power spectral density of the reflected signal. The processing of the combined direct and reflected signals was then analyzed to find the statistics of the measurement error. It was found that the error varies greatly during the satellite overpass and attains its maximum value at closest approach. The maximum values of interferometer phase error and Doppler frequency error found for the system configuration considered were comparable to thermal noise-induced error.

Wallace, R. G.↗
NASA NTRS1984

Pulmonary artery location during microgravity activity: Potential impact for chest-mounted Doppler during space travel

Doppler, or ultrasonic, monitoring for pain manifestations of decompression sickness (the bends) is accomplished by placing a sensor on the chest over the pulmonary artery and listening for bubbles. Difficulties have arisen because the technician notes that the pulmonary artery seems to move with subject movement in a one-g field and because the sensor output is influenced by only slight degrees of sensor movement. This study used two subjects and mapped the position of the pulmonary artery in one-g, microgravity, and two-g environments using ultrasound. The results showed that the pulmonary artery is fixed in location in microgravity and not affected by subject position change. The optimal position corresponded to where the Doppler signal is best heard with the subject in a supine position in a one-g environment. The impact of this result is that a proposed multiple sensor array on the chest proposed for microgravity use may not be necessary to monitor an astronaut during extravehicular activities. Instead, a single sensor of approximately 1 inch diameter and mounted in the position described above may suffice.

Hadley, A. T., III↗
NASA NTRS1984

Growth rate of loudness, annoyance, and noisiness as a function of tone location within the noise spectrum

Absolute magnitude estimation methods were used to investigate the relation between the overall perceived magnitude of noise tone complexes and the location of the tone within the spectrum. In contrast to 'noisiness', loudness and annoyance growth behavior depends on the relationship of the single tones added to low- and high-pass noises in these tests, and to the spectral shape of the noise. Tones centered in noise produce nonmonotonic loudness and annoyance growth functions, while those added to the noise skirt produce power functions. Although a tone correction for annoyance is warranted for certain noise-tone configurations, none of the calculation procedures proposed can take all of the variables relevant to the perceived annoyance of tonal components into account. Complex auditory interactions generated by the simultaneous presentation of noise and tone can substantially account for the effects observed.

Hellman, R. P.↗
NASA NTRS1984

Effect of location in an array on heat transfer to a short cylinder in crossflow

An experiment was conducted to measure the heat transfer from a heated cylinder in crossflow in an array of circular cylinders. All cylinders had a length-to-diameter ratio of 3.0. Both in-line and staggered array patterns were studied. The cylinders were spaced 2.67 diameters apart center-to-center in both the axial and transverse directions to the flow. The row containing the heated cylinder remained in a fixed position in the channel and the relative location of this row within the array was changed by adding up to five upstream rows. The working fluid was nitrogen gas at pressures from 100 to 600 kPa. The Reynolds number range based on cylinder diameter and average unobstructed channel velocity was from 5,000 to 125,000. Turbulence intensity profiles were measured for each case at a point one half space upstream of the row containing the heated cylinder. The basis of comparison for all the heat transfer data was the single row with the heated cylinder. For the in-line cases the addition of a single row of cylinders upstream of the row containing the heated cylinder increased the heat transfer by an average of 50 percent above the base case. Adding up to five more rows caused no increase or decrease in heat transfer. Adding rows in the staggered array cases resulted in average increases in heat transfer of 21, 64, 58, 46, and 46 percent for one to five upstream rows, respectively. Previously announced in STAR as N82-19493

Simoneau, R. J.↗
NASA NTRS1984

A buckling analysis for rectangular orthotropic plates with centrally located cutouts

An analysis to obtain the buckling loads of a rectangular orthotropic plate with a centrally located cutout is described. Cutout shapes can be elliptical, circular, rectangular, or square. The boundary conditions considered in the analysis are simply supported unloaded edges and either clamped or simply supported loaded edges. The plate is loaded in uniaxial compression by either uniform edge displacement or uniform edge stress. A computer program that implements this analysis is described, and the program use is demonstrated by sample problems.

Michael P. Nemeth↗
NASA NTRS1985

Investigation on experimental techniques to detect, locate and quantify gear noise in helicopter transmissions

A robotic system to automate the detection, location, and quantification of gear noise using acoustic intensity measurement techniques has been successfully developed. Major system components fabricated under this grant include an instrumentation robot arm, a robot digital control unit and system software. A commercial, desktop computer, spectrum analyzer and two microphone probe complete the equipment required for the Robotic Acoustic Intensity Measurement System (RAIMS). Large-scale acoustic studies of gear noise in helicopter transmissions cannot be performed accurately and reliably using presently available instrumentation and techniques. Operator safety is a major concern in certain gear noise studies due to the operating environment. The man-hours needed to document a noise field in situ is another shortcoming of present techniques. RAIMS was designed to reduce the labor and hazard in collecting data and to improve the accuracy and repeatability of characterizing the acoustic field by automating the measurement process. Using RAIMS a system operator can remotely control the instrumentation robot to scan surface areas and volumes generating acoustic intensity information using the two microphone technique. Acoustic intensity studies requiring hours of scan time can be performed automatically without operator assistance. During a scan sequence, the acoustic intensity probe is positioned by the robot and acoustic intensity data is collected, processed, and stored.

Flanagan, P. M.↗