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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 3, 4, 1986

Advances in optical technology for remote sensing are discussed in reviews and reports of recent experimental investigations. Topics examined include industrial applications, laser diagnostics for combustion research, laser remote sensing for ranging and altimetry, and imaging systems for terrestrial remote sensing from space. Consideration is given to LIF in forensic diagnostics, time-resolved laser-induced-breakdown spectrometry for rapid analysis of alloys, CARS in practical combustion environments, airborne inertial surveying using laser tracking and profiling techniques, earth-resources instrumentation for the EOS polar platform of the Space Station, and the SAR for EOS.

Menzies, Robert T.↗
NASA NTRS1991

A comparison of laser based ranging systems for AR/C category 1: Hardware

This paper will present some aspects of the effect of inherent laser effects on the performance of CW-Tone modulated and FM-CW laser ranging techniques. It will be shown that performance of these techniques is affected in different ways by inherent laser characteristics and previous comparisons of the techniques should be modified to reflect more realistic conditions. An overall survey of laser ranging will be given to place the CW and FM-CW techniques in perspective. It will be seen that the newly introduced FM-CW laser radar has potentially far superior performance to CW-Tone modulated systems now proposed for use in space rendezvous and capture systems.

Katzberg, Stephen J.↗
NASA NTRS1980

Solar-pumped gas laser development

A survey of gas properties through detailed kinetic models led to the identification of critical gas parameters for use in choosing appropriate gas combinations for solar pumped lasers. Broadband photoabsorption in the visible or near UV range is required to excite large volumes of gas and to insure good solar absorption efficiency. The photoexcitation density is independent of the absorption bandwidth. The state excited must be a metastable state which is not quenched by the parent gas. The emission bandwidth must be less than 10 A to insure lasing threshold over reasonable gain lengths. The system should show a high degree of chemical reversibility and an insensitivity to increasing temperature. Other properties such as good quantum efficiency and kinetic efficiency are also implied. Although photoexcitation of electronic vibrational transitions is considered as a possible system if the emission bands sufficiently narrow, it appears that photodissociation into atomic metastables is more likely to result in a successful solar pumped laser system.

Wilson, J. W.↗
NASA NTRS1987

Experimental study of the velocity field on a delta wing

An experimental study of the leading edge vortices on delta wings at large angles of incidence is presented. A combination of flow visualization, seven-hole pressure probe surveys and laser velocimeter measurements were used to study the leading edge vortex formation and breakdown for a set of delta wings. The delta wing models were thin flat plates with sharp leading edges having sweep angles of 70, 75, 80, and 85 degrees. The flow structure was examined for angles of incidence from 10 to 40 degrees and chord Reynolds numbers from 85,000 to 640,000. Vortex breakdown was observed on all the wings tested. Both bubble and spiral modes of breakdown were observed. The visualization and wake survey data shows that when vortex breakdown occurs the core flow transforms abruptly from a jet-like flow to a wake-like flow. The result also revealed that probe induced vortex breakdown was more steady than the natural breakdown.

Payne, F. M.↗
NASA NTRS2013

The Effect of Bypass Nozzle Exit Area on Fan Aerodynamic Performance and Noise in a Model Turbofan Simulator

The design of effective new technologies to reduce aircraft propulsion noise is dependent on identifying and understanding the noise sources and noise generation mechanisms in the modern turbofan engine, as well as determining their contribution to the overall aircraft noise signature. Therefore, a comprehensive aeroacoustic wind tunnel test program was conducted called the Fan Broadband Source Diagnostic Test as part of the NASA Quiet Aircraft Technology program. The test was performed in the anechoic NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel using a 1/5 scale model turbofan simulator which represented a current generation, medium pressure ratio, high bypass turbofan aircraft engine. The investigation focused on simulating in model scale only the bypass section of the turbofan engine. The test objectives were to: identify the noise sources within the model and determine their noise level; investigate several component design technologies by determining their impact on the aerodynamic and acoustic performance of the fan stage; and conduct detailed flow diagnostics within the fan flow field to characterize the physics of the noise generation mechanisms in a turbofan model. This report discusses results obtained for one aspect of the Source Diagnostic Test that investigated the effect of the bypass or fan nozzle exit area on the bypass stage aerodynamic performance, specifically the fan and outlet guide vanes or stators, as well as the farfield acoustic noise level. The aerodynamic performance, farfield acoustics, and Laser Doppler Velocimeter flow diagnostic results are presented for the fan and four different fixed-area bypass nozzle configurations. The nozzles simulated fixed engine operating lines and encompassed the fan stage operating envelope from near stall to cruise. One nozzle was selected as a baseline reference, representing the nozzle area which would achieve the design point operating conditions and fan stage performance. The total area change from the smallest to the largest nozzle was 12.9 percent of the baseline nozzle area. The results will show that there are significant changes in aerodynamic performance and farfield acoustics as the fan nozzle area is increased. The weight flow through the fan model increased between 7 and 9 percent, the fan and stage pressure dropped between 8 and 10 percent, and the adiabatic efficiency increased between 2 and 3 percent--the magnitude of the change dependent on the fan speed. Results from force balance measurements of fan and outlet guide vane thrust will show that as the nozzle exit area is increased the combined thrust of the fan and outlet guide vanes together also increases, between 2 and 3.5 percent, mainly due to the increase in lift from the outlet guide vanes. In terms of farfield acoustics, the overall sound power level produced by the fan stage dropped nearly linearly between 1 dB at takeoff condition and 3.5 dB at approach condition, mainly due to a decrease in the broadband noise levels. Finally, fan swirl angle survey and Laser Doppler Velocimeter mean velocity and turbulence data obtained in the fan wake will show that the swirl angles and turbulence levels within the wake decrease as the fan nozzle area increases, which helps to explain the drop in the fan broadband noise at all fan speeds.

Hughes, Christopher E.↗
NASA NTRS1989

Laser anemometer measurements in a transonic axial-flow fan rotor

Laser anemometer surveys were made of the 3-D flow field in NASA rotor 67, a low aspect ratio transonic axial-flow fan rotor. The test rotor has a tip relative Mach number of 1.38. The flowfield was surveyed at design speed at near peak efficiency and near stall operating conditions. Data is presented in the form of relative Mach number and relative flow angle distributions on surfaces of revolution at nine spanwise locations evenly spaced from hub to tip. At each spanwise location, data was acquired upstream, within, and downstream of the rotor. Aerodynamic performance measurements and detailed rotor blade and annulus geometry are also presented so that the experimental results can be used as a test case for 3-D turbomachinery flow analysis codes.

Strazisar, Anthony J.↗
NASA NTRS1987

CFD validation experiments at the Lockheed-Georgia Company

Information is given in viewgraph form on computational fluid dynamics (CFD) validation experiments at the Lockheed-Georgia Company. Topics covered include validation experiments on a generic fighter configuration, a transport configuration, and a generic hypersonic vehicle configuration; computational procedures; surface and pressure measurements on wings; laser velocimeter measurements of a multi-element airfoil system; the flowfield around a stiffened airfoil; laser velocimeter surveys of a circulation control wing; circulation control for high lift; and high angle of attack aerodynamic evaluations.

Malone, John B.↗
NASA NTRS1998

Velocity Estimates of Fast-Moving Outlet Glaciers on the Greenland Ice Sheet

In recent years, airborne laser altimetry has been used with great success to investigate the mass balance characteristics of the Greenland ice sheet. One spinoff of this activity has been the application of these measurements to the study of surface velocities in some of Greenland's fast-moving drainage glaciers. This is accomplished by tracking the motion of elevation features, primarily crevasses, in pairs of aircraft laser altimetry surveys. Detailed elevation measurements are made along or across glaciers of interest with a scanning swath of 150 to 200 meters, and the surveys are repeated several days later, typically to within better than 50 meters of the previous flight line. Surface elevation features are identified in each image, and their offsets are compared yielding detailed velocities over narrow regions. During the 1998 field season, repeat flights were made over three glaciers for the purpose of estimating their surface velocities. These were the Kangerdlugssuaq and Helheim glaciers on the east coast and the Jakobshavn Isbrae on the west coast. Each flows at such high speeds (on the order of a few kilometers per year) that their flow rates are difficult to assess by means of radar interferometry. The flexibility of the aircraft platform, however, allows for detailed measurements of the elevation and flow of these drainage areas, which are responsible for a significant portion of the ice discharge from the Greenland ice sheet. Velocity estimates for transects that span these glaciers will be presented, and where the ice thickness values are available (provided by researchers from the University of Kansas) the fluxes will be calculated.

Abdalati, Waleed↗
NASA NTRS1973

LEAPS (Laser electro-optical alignment pole for surveying)

Azimuthal bearing between two obscured points is measured by placing laser beam at one of the points. Beam is directed straight up into the air so that some part of it may be detected from any position a reasonable distance away.

Caudill, L.↗
NASA NTRS1988

Detailed flowfield measurements over a 75 deg swept delta wing for code validation

Selected results from an experimental investigation documenting the flowfield over 75 deg swept delta wing at an angle-of-attack of 20.5 deg are presented. Results obtained in the investigation include surface flow visualization, off-body flow visualization, and detailed flowfield surveys for various Reynolds numbers. Flowfield surveys at Reynolds numbers of 0.5, 1.0 and 1.5 million were conducted with both a pitot pressure probe and a 5-hole pressure probe; and 3-component laser Doppler velocimeter surveys were conducted at a Reynolds number of 1.0 million. The pitot pressure surveys were obtained at 5 longitudinal stations, the 5-hole probe surveys were obtained at 3 longitudinal stations and the laser Doppler velocimeter surveys were obtained at one station. The accuracy of each instrumentation system is discussed, as well as, discrepancies in the calculation of vorticity using various algorithms.

Kjelgaard, Scott O.↗
NASA NTRS1988

A survey of beam-combining technologies for laser space power transmission

The combination of laser beams holds much promise for obtaining powerful beams. Methods are surveyed for beam combination (coherent and incoherent) and two of them are identified as the most effective means for achieving high power transmission in space. The two methods as applied to laser diode arrays are analyzed, and potentially productive work areas for the advancement of technology are delineated.

Kwon, J. H.↗
NASA NTRS1999

Laser Velocimeter Measurements of the Flow Within a Vane-Island Diffuser

A series of detailed non-intrusive laser velocimeter flow field surveys were performed to validate computational fluid dynamic (CFD) codes for rotating pump components. Three component laser-2-focus (L2F) laser velocimetry was used to acquire data within a flow passage of a diffuser at design flow conditions. The thirteen vane-island type diffuser was designed to allow diffusion in the axial direction. Multiple laser velocimeter surveys were performed throughout several diffuser passages and at multiple diffuser depths (hub to shroud). The axial (3D) component of the velocity at all locations was small. The radial and meridional velocity components nearest the diffuser hub increased in magnitude relative to the flow nearest the shroud as the flow progressed through the diffuser. A continuity check across the diffuser throat and based on the meridional velocity component yielded a match with a facility flow meter of 98.0%.

Ferguson, Thomas V.↗
NASA NTRS1978

Status and summary of laser energy conversion

This paper presents a survey of the status of laser energy converters. Since the inception of these devices in the early 1970's, significant advances have been made in understanding the basic conversion processes. Numerous theoretical and experimental studies have indicated that laser energy can be converted at wavelengths from the ultraviolet to the far-infrared. These converters can be classified into five general categories: photovoltaics, heat engines, thermoelectronic, optical diode, and photochemical. The conversion can be directly into electricity (such as the photovoltaic, thermoelectronic, and optical diode) or it can go through an intermediate stage of conversion to mechanical energy, as in the heat engines. The photochemical converters result in storable energy such as hydrogen. Projected conversion efficiencies range from about 30% for the photochemical to nearly 75% for the heat engines.

Lee, G.↗
NASA NTRS2017

Molecular Analyzer for Complex Refractory Organic-Rich Surfaces (MACROS)

The Molecular Analyzer for Complex Refractory Organic-rich Surfaces, MACROS, is a novel instrument package being developed at NASA Goddard Space Flight Center. MACROS enables the in situ characterization of a sample's composition by coupling two powerful techniques into one compact instrument package: (1) laser desorption/ionization time-of-flight mass spectrometry (LDMS) for broad detection of inorganic mineral composition and non-volatile organics, and (2) liquid-phase extraction methods to gently isolate the soluble organic and inorganic fraction of a planetary powder for enrichment and detailed analysis by liquid chromatographic separation coupled to LDMS. The LDMS is capable of positive and negative ion detection, precision mass selection, and fragment analysis. Two modes are included for LDMS: single laser LDMS as the broad survey mode and two step laser mass spectrometry (L2MS). The liquid-phase extraction will be done in a newly designed extraction module (EM) prototype, providing selectivity in the analysis of a complex sample. For the sample collection, a diamond drill front end will be used to collect rock/icy powder. With all these components and capabilities together, MACROS offers a versatile analytical instrument for a mission targeting an icy moon, carbonaceous asteroid, or comet, to fully characterize the surface composition and advance our understanding of the chemical inventory present on that body.

Getty, Stephanie A.↗
NASA NTRS1981

Remote Raman measurement techniques

The use of laser Raman measurement techniques in remote sensing applications is surveyed. A feasibility index is defined as a means to characterize the practicality of a given remote Raman measurement application. Specific applications of Raman scattering to the measurement of atmospheric water vapor profiles, methane plumes from liquid natural gas spills, and subsurface ocean temperature profiles are described. This paper will survey the use of laser Raman measurement techniques in remote sensing applications using as examples specific systems that the Computer Genetics Corporation (CGC) group has developed and engineered.

Leonard, D. A.↗