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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 307 records · Page 17

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NASA NTRS1999

Aero-Structural Interaction, Analysis, and Shape Sensitivity

A multidisciplinary sensitivity analysis technique that has been shown to be independent of step-size selection is examined further. The accuracy of this step-size independent technique, which uses complex variables for determining sensitivity derivatives, has been previously established. The primary focus of this work is to validate the aero-structural analysis procedure currently being used. This validation consists of comparing computed and experimental data obtained for an Aeroelastic Research Wing (ARW-2). Since the aero-structural analysis procedure has the complex variable modifications already included into the software, sensitivity derivatives can automatically be computed. Other than for design purposes, sensitivity derivatives can be used for predicting the solution at nearby conditions. The use of sensitivity derivatives for predicting the aero-structural characteristics of this configuration is demonstrated.

Newman, James C., III↗

NASA NTRS2003

Deposition of Nanostructured Thin Film from Size-Classified Nanoparticles

Materials comprising nanometer-sized grains (approximately 1_50 nm) exhibit properties dramatically different from those of their homogeneous and uniform counterparts. These properties vary with size, shape, and composition of nanoscale grains. Thus, nanoparticles may be used as building blocks to engineer tailor-made artificial materials with desired properties, such as non-linear optical absorption, tunable light emission, charge-storage behavior, selective catalytic activity, and countless other characteristics. This bottom-up engineering approach requires exquisite control over nanoparticle size, shape, and composition. We describe the design and characterization of an aerosol system conceived for the deposition of size classified nanoparticles whose performance is consistent with these strict demands. A nanoparticle aerosol is generated by laser ablation and sorted according to size using a differential mobility analyzer. Nanoparticles within a chosen window of sizes (e.g., (8.0 plus or minus 0.6) nm) are deposited electrostatically on a surface forming a film of the desired material. The system allows the assembly and engineering of thin films using size-classified nanoparticles as building blocks.

Camata, Renato P.↗

NASA NTRS2000

Optical Pulse Synthesis Using Brillouin Selective Sideband Amplification

Optical pulse generation using Fourier synthesis is attractive for a number of applications, including photonic A/D conversion, electro-optic sampling, and time-resolved spectroscopy, because the bandwidth, shape, and repetition rate of the pulse can be easily controlled.

optical pulse brillouin selective sideband↗

NASA NTRS2022

2019 ARIA Proposal Final Report Public Abstract: What Happens to Life in an Ocean World Plume?

The NASA Cassini mission to Saturn discovered persistent jets of water being ejected into space from a subsurface ocean on the small moon Enceladus and evidence that this ocean is habitable for life. The ice resulting from these plumes forms the E Ring of Saturn. Missions are under study to fly through these plumes and collect and analyze samples to look for evidence of life. To support design and instrument selection for these missions, there is a critical need to understand what happens to microbial life adapted to a liquid environment when suddenly ejected into the vacuum of space. We experimentally determined the structural changes in microbial cells in liquid medium when ejected into vacuum. We first developed a vacuum chamber fitted with a feedthrough and nozzle allowing fluid to be injected into vacuum. The nozzle dispersed the fluid into micron-sized droplets. Fluid containing a population of E. Coli microbes was injected into the chamber and droplets were collected on microscope slides and small cups for imaging with a Scanning Electron Microscope (SEM). Epifluorescence microscopy, using a lipid stain, and SEM imaging were used to evaluate the cellular integrity of E. coli after injection through the pressurized nozzle into vacuum. The experimental samples showed a 94% decrease in visible intact E. coli cells as compared with control samples but showed a fluorescent residue in the shape of the sublimated droplets that indicated the presence of lipids. E. coli was selected for testing although other cell types could vary physiologically which could affect their response to a vacuum environment. More testing is needed to determine whether other types of microbial cells can survive the plume environment. However, these results suggest that lipids may be directly detectable evidence of life in icy world plumes, but organisms are unlikely to survive due to disruption of their cell walls.

C. R. Stoker↗

NASA NTRS1974

Variably positioned guide vanes for aerodynamic choking

A choking device to cause a sonic barrier to be formed which reduces the transmission of noise in a direction opposed to the direction of air flow in a compressor that may be part of an aircraft gas turbine engine is described. The noise reduction is accomplished by proper shaping and movement of inlet guide vanes, and an actuator is connected to selected guide vanes to effect movement by programmed amounts as required to choke or partially choke within the design range of the axial-flow-air compressor.

Chestnutt, D.↗

NASA NTRS1983

Aeroelastic loads prediction for an arrow wing. Task 2: Evaluation of semi-empirical methods

The development and evaluation of a semi empirical method to predict pressure distributions on a deformed wing by using an experimental data base in addition to a linear potential flow solution is described. The experimental data accounts for the effects of aeroelasticity by relating the pressures to a parameter which is influenced by the deflected shape. Several parameters were examined before the net leading edge suction coefficient was selected as the best.

Wery, A. C.↗

NASA NTRS1983

The electronic switching spherical array antenna for the Earth Radiation Budget Spacecraft

The ESSA is a microprocessor-controlled antenna for low orbiting spacecraft for telemetry and command relay through the Tracking and Data Relay Satellite System (TDRSS). The array is a hemispherical shape covered with disk radiating elements. A group of radiating elements are continuously selected by the microprocessor controller to form a beam in the direction of a TDRS. A radial switching power divider uses PIN diodes to select the desired radiating elements. The antenna gain is a function of the size of the hemispherical dome. A 30-inch diameter dome is presently being built for the Earth Radiation Budget Spacecraft (ERBS). Gain of this antenna over a hemisphere is 14 dBi and polarization is lefthand circular. There are 145 radiating elements with 12 being used at one time to form a beam. The ESSA subsystem weights 74 pounds and power consumption is 20 watts. RF power handling capability is 30 watts. The S-Band radiating elements have a 10 percent bandwidth that allows simultaneous transmission and reception.

Kudrna, K.↗

NASA NTRS1987

The determination of exhaust cloud dimensions from films of space shuttle launches

Principles of photogrammetry are used to calculate the dimension of ground clouds produced from the Space Shuttle launch system. For each of three launches (Missions 41C, 41D, and 51A), a 16 mm camera recorded the ground cloud from three different locations. Measurements were made from outlines of the cloud and other features of interest which were traced onto paper at one-minute intervals using a 16 mm stop-action projector. Cloud characteristics such as top, max width at top, average width, and base are presented as a function of time. A temperature inversion was present each launch day and the cloud responded by first rising into the inversion and then descending to about the inversion height. Max tops were achieved in about three to five minutes and ranged from 2200 m for Mission 41C to 3500 m for Mission 41D. Cloud bases rose steadily to between 700 and 1000 m after 10 minutes. Average widths ranged from 500 to 1700 m depending on mission and camera. Photographs of digitizations of selected film frames are included in the report to show the irregular cloud shapes. Error sources for this analysis are also discussed.

Zak, R. A.↗

NASA NTRS1994

Holographic testing of composite propfans for a cruise missile wind tunnel model

Each of the approximately 90 composite propfan blades constructed for a 55 percent scale cruise missile wind tunnel model were holographically tested to obtain natural frequencies and mode shapes. These data were used not only for quality assurance, but also to select sets of similar blades for each blade row. Presented along with the natural frequency data is a description of a computer-based image processing system developed to supplement the photographic based system for holographic image analysis and storage. The new system is quicker and cheaper, the holograms are indexed better, and several engineers can access the data simultaneously. The only negative effect is a slight reduction in image resolution, which does not influence the end use.

Miller, Christopher J.↗

NASA NTRS1994

Interactive shape metamorphosis

A technique for controlled metamorphosis between surfaces in 3-space is described. Well-understood techniques to produce shape metamorphosis between models in a 2D parametric space is applied. The user selects morphable features interactively, and the morphing process executes in real time on a high-performance graphics multicomputer.

Chen, David T.↗

NASA NTRS2002

A study of hear sink performance in air and soil for use in a thermoelectric energy harvesting device

A suggested application of a thermoelectric generator is to exploit the natural temperature difference between the air and the soil to generate small amounts of electrical energy. Since the conversion efficiency of even the best thermoelectric generators available is very low, the performance of the heat sinks providing the heat flow is critical. By providing a constant heat input to various heat sinks, field tests of their thermal conductances in soil and in air were performed. Aprototype device without a thermoelectric generator was constructed, buried, and monitored to experimentally measure the heat flow achievable in such a system. Theoretical considerations for design and selection of improved heat sinks are also presented. In particular, the method of shape factoranalysis is used to give rough estimates and upper bounds for the thermal conductance of a passive heat sink buried in soil.

Thermoelectric power generation↗

NASA NTRS1996

Plasma spray nozzle with low overspray and collimated flow

An improved nozzle for reducing overspray in high temperature supersonic plasma spray devices comprises a body defining an internal passageway having an upstream end and a downstream end through which a selected plasma gas is directed. The nozzle passageway has a generally converging/diverging Laval shape with its upstream end converging to a throat section and its downstream end diverging from the throat section. The upstream end of the passageway is configured to accommodate a high current cathode for producing an electrical arc in the passageway to heat and ionize the gas flow to plasma form as it moves along the passageway. The downstream end of the nozzle is uniquely configured through the methodology of this invention to have a contoured bell-shape that diverges from the throat to the exit of the nozzle. Coating material in powder form is injected into the plasma flow in the region of the bell-shaped downstream end of the nozzle and the powder particles become entrained in the flow. The unique bell shape of the nozzle downstream end produces a plasma spray that is ideally expanded at the nozzle exit and thus virtually free of shock phenomena, and that is highly collimated so as to exhibit significantly reduced fanning and diffusion between the nozzle and the target. The overall result is a significant reduction in the amount of material escaping from the plasma stream in the form of overspray and a corresponding improvement in the cost of the coating operation and in the quality and integrity of the coating itself.

Beason, Jr., George P.↗

NASA NTRS2004

Antenna Linear-Quadratic-Gaussian (LQG) Controllers: Properties, Limits of Performance, and Tuning Procedure

Wind gusts are the main disturbances that depreciate tracking precision of microwave antennas and radiotelescopes. The linear-quadratic-Gaussian (LQG) controllers - as compared with the proportional-and-integral (PI) controllers significantly improve the tracking precision in wind disturbances. However, their properties have not been satisfactorily understood; consequently, their tuning is a trial-and-error process. A control engineer has two tools to tune an LQG controller: the choice of coordinate system of the controller model and the selection of weights of the LQG performance index. This article analyzes properties of an open- and closed-loop antenna. It shows that the proper choice of coordinates of the open-loop model simplifies the shaping of the closed-loop performance. The closed-loop properties are influenced by the LQG weights. The article shows the impact of the weights on the antenna closed-loop bandwidth, disturbance rejection properties, and antenna acceleration. The bandwidth and the disturbance rejection characterize the antenna performance, while the acceleration represents the performance limit set by the antenna hardware (motors). The article presents the controller tuning procedure, based on the coordinate selection and the weight properties. The procedure rationally shapes the closed-loop performance, as an alternative to the trial-and-error approach.

Gawronski, W.↗

NASA NTRS2001

Suppression of Soot Formation and Shapes of Laminar Jet Diffusion Flames

Laminar nonpremixed (diffusion) flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than practical turbulent flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Finally, laminar diffusion flame shapes have been of interest since the classical study of Burke and Schumann because they involve a simple nonintrusive measurement that is convenient for evaluating flame shape predictions. Motivated by these observations, the shapes of round hydrocarbon-fueled laminar jet diffusion flames were considered, emphasizing conditions where effects of buoyancy are small because most practical flames are not buoyant. Earlier studies of shapes of hydrocarbon-fueled nonbuoyant laminar jet diffusion flames considered combustion in still air and have shown that flames at the laminar smoke point are roughly twice as long as corresponding soot-free (blue) flames and have developed simple ways to estimate their shapes. Corresponding studies of hydrocarbon-fueled weakly-buoyant laminar jet diffusion flames in coflowing air have also been reported. These studies were limited to soot-containing flames at laminar smoke point conditions and also developed simple ways to estimate their shapes but the behavior of corresponding soot-free flames has not been addressed. This is unfortunate because ways of selecting flame flow properties to reduce soot concentrations are of great interest; in addition, soot-free flames are fundamentally important because they are much more computationally tractable than corresponding soot-containing flames. Thus, the objectives of the present investigation were to observe the shapes of weakly-buoyant laminar jet diffusion flames at both soot-free and smoke point conditions and to use the results to evaluate simplified flame shape models. The present discussion is brief.

Xu, F.↗

NASA NTRS1992

Design of a radiator shade for testing in a simulated lunar environment

The National Aeronautics and Space Administration (NASA) and The Universities Space Research Association (USRA) have chosen the parabolic/catenary concept from their sponsored Fall 1991 lunar radiation shade project for further testing and development. NASA asked the design team to build a shading device and support structure for testing in a vacuum chamber. Besides the support structure for the catenary shading device, the design team was asked to develop a system for varying the shade shape so that the device can be tested at different focal lengths. The design team developed concept variants and combined the concept variants to form overall designs. Using a decision matrix, an overall design was selected by the team from several overall design alternatives. Concept variants were developed for three primary functions. The three functions were structural support, shape adjustments, and end shielding. The shade adjustment function was divided into two sub-functions, arc length adjustment, and width adjustment.

Huff, Jaimi↗

NASA NTRS1993

Metallographic cooling rates of L-group ordinary chondrites

Shock metamorphism appears to be a ubiquitous feature in L-group ordinary chondrites. Brecciation and heterogeneous melting obscure much of the early history of this meteorite group and have caused confusion as to whether L chondrites have undergone thermal metamorphism within onion-shell or rubble-pile parent bodies. Employing the most recent shock criteria, we have examined 55 Antarctic and 24 non-Antarctic L chondrites in order to identify those which have been least affected by post-accretional shock. Six low-shock samples (those with shock grade less than S4) of petrographic types L3-L5 were selected from both populations and metallographic cooling rates were obtained following the technique of Willis and Goldstein. All non-Antarctic L6 chondrites inspected were too heavily shocked to be included in this group. However, 4 shocked L6 chondrites were analyzed in order to determine what effects shock may impose on metallographic cooling rates. Metallographic cooling rates were derived by analyzing the cores of taenite grains and then measuring the distance to the nearest grain edge. Taenites were identified using backscatter imaging on a Cameca SX-50 electron microprobe. Using backscatter we were able to locate homogeneous, rust-free, nearly spherical grains. M-shaped profiles taken from grain traverses were also used to help locate the central portions of selected grains. All points which contained phosphorus above detection limits were discarded. Plots of cooling-rate data are summarized and data from the high-shock samples are presented. The lack of coherency of cooling rates for individual samples is indicative of heterogeneous cooling following shock. The data confirms the statement expressed by numerous workers that extreme care must be taken when selecting samples of L chondrites for cooling-rate studies. Data for the 6 non-Antarctic low-shock samples are also presented. The samples display a general trend in cooling rates. The lowest metamorphic grade yielded the slowest cooling rates and an increase in grade follows an increase in cooling rate. This is the opposite relationship to that predicted by the onion-shell model.

Bennett, Marvin E.↗

NASA NTRS1982

Selection of USSR foreign similarity regions

The similarity regions in the United States and Canada were selected to parallel the conditions that affect labeling and classification accuracies in the U.S.S.R. indicator regions. In addition to climate, a significant condition that affects labeling and classification accuracies in the U.S.S.R. is the proportion of barley and wheat grown in a given region (based on sown areas). The following regions in the United States and Canada were determined to be similar to the U.S.S.R. indicator regions: (1) Montana agrophysical unit (APU) 104 corresponds to the Belorussia high barley region; (2) North Dakota and Minnesota APU 20 and secondary region southern Manitoba and Saskatchewan correspond to the Ural RSFSR barley and spring wheat region; (3) Montana APU 23 corresponds to he North Caucasus barley and winter wheat region. Selection criteria included climates, crop type, crop distribution, growth cycles, field sizes, and field shapes.

Disler, J. M.↗

NASA NTRS1985

Computer studies of hybrid slotted working sections with minimum steady interference at subsonic speeds

Currently there is renewed interest in the evaluation and reduction of steady wind tunnel wall interference, especially for large models. Evaluation of previous predictions for perforated and slotted tunnels suggests that a hybrid slotted tunnel (i.e., a slotted tunnel with closed slats and perforated slots) should offer minimum corrections for upwash, flow curvature and solid blockage. This suggestion is confirmed by the present computer studies of a range of rectangular hybrid slotted tunnels. The computer studies are for tunnel working section height to breadth ratios of 0.835 and 0.600 over the Mach number range from 0 to 0.85. Wings swept at 28 deg and 50 deg, with ratios of model span to tunnel breadth varying from 0 to 0.7, are considered. An idealized fuselage shape is used to predict solid and wake blockage corrections for the wall configurations selected on the basis of minimum upwash and curvature interference.

Mabey, D. G.↗