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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Qualification of Laser Diode Arrays for Mercury Laser Altimeter Mission

NASA's requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. The MESSENGER mission is flying the Mercury Laser Altimeter (MLA) which is a diode-pumped Nd:YAG laser instrument designed to map the topography of Mercury. The environment imposed on the instrument by the orbital dynamics places special requirements on the laser diode arrays. In order to limit the radiative heating of the satellite from the surface of Mercury, the satellite is designed to have a highly elliptical orbit. The satellite will heat near perigee and cool near apogee. The laser power is cycled during these orbits so that the laser is on for only 30 minutes (perigee) in a 12 hour orbit. The laser heats 10 C while powered up and cools while powered down. In order to simulate these operational conditions, we designed a test to measure the LDA performance while being temperature and power cycled. Though the mission requirements are specific to NASA and performance requirements are derived from unique operating conditions, the results are general and widely applicable. We present results on the performance of twelve LDAs operating for several hundred million pulses. The arrays are 100 watt, quasi-CW, conductively-cooled, 808 nm devices. Prior to testing, we fully characterize each device to establish a baseline for individual array performance and status. Details of this characterization can be found in reference. Arrays are divided into four groups and subjected to the temperature and power cycling matrix are shown.

Stephen, Mark↗
NASA NTRS1976

Laser engines operating by resonance absorption

Basic tutorial article on the thermodynamic feasibility of laser engines at the present state of the art. Three main options are considered: (1) laser power applied externally to a heat reservoir (boiler approach); (2) internal heating of working fluid by resonance absorption; and (3) direct conversion of selective excitation into work. Only (2) is considered practically feasible at present. Basic concepts and variants, efficiency relations, upper temperature limits of laser engines, selection of absorbing gases, engine walls, bleaching, thermodynamic cycles of optimized laser engines, laser-powered turbines, laser heat pumps are discussed. Photon engines and laser dissociation engines are also considered.

Garbuny, M.↗
NASA NTRSDate not supplied

Simultaneous Convective and Radiative Heating of Materials with the 200 kW Laser Enhanced Arc Jet Facility (LEAF)

Recent installation of the 200-kW Laser Enhanced Arc Jet Facility (LEAF) at the Interaction Heating Facility (IHF) arc jet at NASA Ames Research Center has enabled combined heating of material samples. The LEAF system is permanently located adjacent to IHF. During LEAF operation, IHF can convectively heat material samples with heat fluxes up to 0.16 kW/cm 2 using the 22.86-cm nozzle or up to 0.07 kW/cm 2 using the truncated semi-elliptic nozzle. LEAF can deliver radiant heating with various profiles and sizes to a material sample. In flat-top square configuration, irradiance levels of nearly 0.1 kW/cm 2 have been demonstrated over a 43.2 x 43.2 cm area, and irradiance levels up to 0.39 kW/cm 2 have been demonstrated over a 15.2 x 15.2 cm area. LEAF can also be configured to deliver a super-Gaussian profile over a variety of beam diameters (1.8 to 5.6 cm). This configuration has been demonstrated up to peak irradiance levels of 25.7 kW/cm 2 per laser at the smallest, 1.8 cm, diameter setting. The LEAF system is composed of four 50-kW lasers, so it can also be configured to simultaneously deliver two different beam shapes (e.g., one square beam and one super-Gaussian beam).

Megan MacDonald↗
NASA NTRS2011

Flow Property Measurement Using Laser-Induced Fluorescence in the NASA Ames Interaction Heating Facility

The spectroscopic diagnostic technique of two photon absorption laser-induced fluorescence (TALIF) of atomic species has been applied to single-point measurements of velocity and static temperature in the NASA Ames Interaction Heating Facility (IHF) arc jet. Excitation spectra of atomic oxygen and nitrogen were recorded while scanning a tunable dye laser over the absorption feature. Thirty excitation spectra were acquired during 8 arc jet runs at two facility operating conditions; the number of scans per run varied between 2 and 6. Curve fits to the spectra were analyzed to recover their Doppler shifts and widths, from which the flow velocities and static temperatures, respectively, were determined. An increase in the number of independent flow property pairs from each as-measured scan was obtained by extracting multiple lower-resolution scans. The larger population sample size enabled the mean property values and their uncertainties for each run to be characterized with greater confidence. The average plus or minus 2 sigma uncertainties in the mean velocities and temperatures for all 8 runs were plus or minus 1.4% and plus or minus 11%, respectively.

Grinstead, Jay Henderson↗
NASA NTRS2008

Four-Pass Coupler for Laser-Diode-Pumped Solid-State Laser

A four-pass optical coupler affords increased (in comparison with related prior two-pass optical couplers) utilization of light generated by a laser diode in side pumping of a solid-state laser slab. The original application for which this coupler was conceived involves a neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal slab, which, when pumped by a row of laser diodes at a wavelength of 809 nm, lases at a wavelength of 1,064 nm. Heretofore, typically, a thin laser slab has been pumped in two passes, the second pass occurring by virtue of reflection of pump light from a highly reflective thin film on the side opposite the side through which the pump light enters. In two-pass pumping, a Nd:YAG slab having a thickness of 2 mm (which is typical) absorbs about 84 percent of the 809-nm pump light power, leaving about 16 percent of the pump light power to travel back toward the laser diodes. This unused power can cause localized heating of the laser diodes, thereby reducing their lifetimes. Moreover, if the slab is thinner than 2 mm, then even more unused power travels back toward the laser diodes. The four-pass optical coupler captures most of this unused pump light and sends it back to the laser slab for two more passes. As a result, the slab absorbs more pump light, as though it were twice as thick. The gain and laser cavity beam quality of a smaller laser slab in conjunction with this optical coupler can thus be made comparable to those of a larger two-pass-pumped laser slab.

Coyle, Donald B.↗
NASA NTRS1990

Species and velocity visualization of unseeded heated air and combusting hydrogen jets using laser and flashlamp sources

Three techniques for the visualization of species and/or velocity in unseeded H2/air flames and heated air jets are described and preliminary image data are presented. The techniques described are: (1) simultaneous ArF laser imaging of H2, O2, and Rayleigh cross-section weighted density in an H2, O2, and Rayleigh cross-section weighted density in an H2/air flame; (2) ultraviolet flashlamp imaging of O2, OH, and Rayleigh cross-section weighted density in an H2/air flame; and (3) Raman Excitation plus Laser Induced Electronic Fluorescence velocimetry in heater air flows, up to static temperatures of 700 K. Application of these techniques, individually or in combination, should provide useful insight into mixing and reacting flows containing H2, O2, N2 and reaction intermediates such as OH.

Diskin, Glenn S.↗
NASA NTRS1997

Steady-State and Frequency Response of a Thin-Film Heat Flux Gauge

A new and simpler design of thin-film heat flux gauge has been developed for use In high-heat-flux environments. Heat flux gauges of the same design were fabricated on three different substrates and tested. The heat flux gauge comprises a thermopile and a thermocouple junction, which measures the surface temperature. The thermopile has 40 pairs of S-type thermocouples and is covered by two thermal resistance layers. Calibration and testing of these gauges were first carried out in an arc-lamp calibration facility. Sensitivity of the gauge was discussed in terms of the relative conductivity and surface temperature. The heat flux calculated from the gauge output was In good agreement with the precalibrated standard sensor. The steady-state and the transient response characteristics of the heat flux gauge were also investigated using a carbon dioxide pulse laser as a heat source. The dynamic frequency response was evaluated in terms of the nondimensional amplitude ratio with respect to the frequency spectrum of a chopped laser bcam. The frequency response of the gauge was determined to be about 3 kHz. The temperature profiles in the thin-film heat flux gauge were obtained numerically in steady-state conditions using FLUENT and compared with the experimental results.

Fralick, Gustave C.↗
NASA NTRS1993

Optical properties and spectral emissivities at 632.8 nm in the titanium-aluminum system

Optical properties (including spectral emissivity, refractive index, and extinction coefficient) of liquid Ti-Al alloys were measured as functions of temperature (including temperatures up to 350 K below the equilibrium liquidus temperatures), using laser ellipsometry at 632.8 nm. The experiments were conducted under containerless conditions, using electromagnetic levitation and heating supplemented by CO2 laser beam heating. It is shown that the emissivities of liquid Ti-Al alloy vary with temperature in a manner that can be understood by the same theories which are applicable to solid metals, for regions near to and above the liquidus temperature. At temperatures below the liquidus temperature, the optical properties of highly undercooled liquid Ti-Al alloys are not dependent on temperature.

Krishnan, S.↗
NASA NTRS2008

Simultaneous Temperature and Velocity Measurements in a Large-Scale, Supersonic, Heated Jet

Two laser-based measurement techniques have been used to characterize an axisymmetric, combustion-heated supersonic jet issuing into static room air. The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) measurement technique measured temperature and concentration while the interferometric Rayleigh scattering (IRS) method simultaneously measured two components of velocity. This paper reports a preliminary analysis of CARS-IRS temperature and velocity measurements from selected measurement locations. The temperature measurements show that the temperature along the jet axis remains constant while dropping off radially. The velocity measurements show that the nozzle exit velocity fluctuations are about 3% of the maximum velocity in the flow.

Danehy, P. M.↗
NASA NTRS1985

Process research of non-Cz material

Efforts were aimed at achieving a simultaneous front and back junction. Lasers and other heat sources were tried. Successful results were gained by two different methods: laser and flash lamp. Polymer dopants were applied to both sides of dendritic web cells. Rapid heating and cooling avoided any cross contamination between two junctions after removal of the dendrites. Both methods required subsequent thermal annealing in an oven to produce maximum efficiency cells.

Campbell, R. B.↗
NASA NTRS2001

Geoscience Laser Altimeter System (GLAS) Instrument: Flight Loop Heat Pipe (LHP) Acceptance Thermal Vacuum Test

Two loop heat pipes (LHPs) are to be used for tight thermal control of the Geoscience Laser Altimeter System (GLAS) instrument, planned for flight in late 2001. The LHPs are charged with Propylene as a working fluid. One LHP will be used to transport 110 W from a laser to a radiator, the other will transport 160 W from electronic boxes to a separate radiator. The application includes a large amount of thermal mass in each LHP system and low initial startup powers. The initial design had some non-ideal flight design compromises, resulted in a less than ideal charge level for this design concept with a symmetrical secondary wick. This less than ideal charge was identified as the source of inadequate performance of the flight LHPs during the flight thermal vacuum test in October of 2000. We modified the compensation chamber design, re-built and charged the LHPs for a final LHP acceptance thermal vacuum test. This test performed March of 2001 was 100% successful. This is the last testing to be performed on the LHPs prior to instrument thermal vacuum test. This sensitivity to charge level was shown through varying the charge on a Development Model Loop Heat Pipe (DM LHP) and evaluating performance at various fill levels. At lower fills similar to the original charge in the flight units, the same poor performance was observed. When the flight units were re-designed and filled to the levels similar to the initial successful DM LHP test, the flight units also successfully fulfilled all requirements. This final flight Acceptance test assessed performance with respect to startup, low power operation, conductance, and control heater power, and steady state control. The results of the testing showed that both LHPs operated within specification. Startup on one of the LHPs was better than the other LHP because of the starter heater placement and a difference in evaporator design. These differences resulted in a variation in the achieved superheat prior to startup. The LHP with the lower superheat was sensitive to the thermal environment around the compensation chamber, while the LHP with the higher superheat (similar in design to DM LHP) was not. In response to the test results the placement of the starter heater will be optimized for the flight instrument testing for higher achieved superheat. This presentation discusses startup behavior, overall conductance of a radiator system, low power operation, high power operation, temperature control stability, and control heater power requirements as measured during this acceptance thermal vacuum test. A brief summary of 'lessons learned' will be included.

Baker, Charles↗
NASA NTRS2017

Molecular Composition Analysis of Distant Targets

This document is the Final Report for NASA Innovative Advanced Concepts (NIAC) Phase I Grant 15-NIAC16A-0145, titled Molecular Composition Analysis of Distant Targets. The research was focused on developing a system concept for probing the molecular composition of cold solar system targets, such as Asteroids, Comets, Planets and Moons from a distant vantage, for example from a spacecraft that is orbiting the target (Hughes et al., 2015). The orbiting spacecraft is equipped with a high-power laser, which is run by electricity from photovoltaic panels. The laser is directed at a spot on the target. Materials on the surface of the target are heated by the laser beam, and begin to melt and then evaporate, forming a plume of asteroid molecules in front of the heated spot. The heated spot glows, producing blackbody illumination that is visible from the spacecraft, via a path through the evaporated plume. As the blackbody radiation from the heated spot passes through the plume of evaporated material, molecules in the plume absorb radiation in a manner that is specific to the rotational and vibrational characteristics of the specific molecules. A spectrometer aboard the spacecraft is used to observe absorption lines in the blackbody signal. The pattern of absorption can be used to estimate the molecular composition of materials in the plume, which originated on the target. Focusing on a single spot produces a borehole, and shallow subsurface profiling of the targets bulk composition is possible. At the beginning of the Phase I research, the estimated Technology Readiness Level (TRL) of the system was TRL-1. During the Phase I research, an end-to-end theoretical model of the sensor system was developed from first principles. The model includes laser energy and optical propagation, target heating, melting and evaporation of target material, plume density, thermal radiation from the heated spot, molecular cross section of likely asteroid materials, and estimation of the absorption profile at a distant spectrometer. Results obtained by executing simulations based on the model provide compelling evidence that the concept of remote laser evaporative molecular absorption spectroscopy is feasible. In this document, technical details of the model are presented, and results of simulations are described that indicate the utility of the proposed sensor system. Additionally, an asteroid rendezvous mission is analyzed, with a survey of system requirements to accomplish molecular composition analysis of the asteroid. Based on positive theoretical results obtained during Phase I, the estimated TRL of the system is now TRL-2. This document also describes potential future research and experimentation that could push the system to TRL-4 within 2 years. Steps required for construction of a laboratory prototype are described. An experiment to test predictions of the theory is described, based on the laboratory prototype setup.

asteroid↗
NASA NTRS1985

Modelling of Laser-Enhanced Chemical Vapor Deposition

Research is directed at development of a detailed model of mass and heat transfer and chemical reaction in the pyrolysis of silane for the growth of thin amorphous silicon substrates incorporating laser heating of the gas phase above the film. The model will be the basis for evaluation of the relative importances of the decomposition of SiH4 in the vapor phase, mass transfer of the intermediate species, e.g., SiH2, and the evolution of hydrogen gas. Plans are also underway for developing a model for homogeneous nucleation of Si in the vapor phase to model the rate limitations observed at high gas-phase temperatures and high partial pressures of silane. Work was concentrated on an almost one-dimensional model for the coupling of the CO2 laser beam for heat transfer of the vapor phase with simple kinetic models for SiH4 decomposition and subsequent absorption of Si vapor on the substrate. Mass transfer in the vapor phase is assumed to be solely by diffusion. The role of convection in the vapor phase caused by the large changes in density in and around the center of the laser beam will be analyzed to evaluate the potential of microgravity experiments for increasing the uniformity of the film and the deposition rate.

Brown, R. A.↗
NASA NTRS2013

Monitoring Temperature in High Enthalpy Arc-heated Plasma Flows using Tunable Diode Laser Absorption Spectroscopy

A tunable diode laser sensor was designed for in situ monitoring of temperature in the arc heater of the NASA Ames IHF arcjet facility (60 MW). An external cavity diode laser was used to generate light at 777.2 nm and laser absorption used to monitor the population of electronically excited oxygen atoms in an air plasma flow. Under the assumption of thermochemical equilibrium, time-resolved temperature measurements were obtained on four lines-of-sight, which enabled evaluation of the temperature uniformity in the plasma column for different arcjet operating conditions.

Martin, Marcel Nations↗
NASA NTRS1990

Diode laser satellite systems for beamed power transmission

A power system composed of an orbiting laser satellite and a surface-based receiver/converter is described. Power is transmitted from the satellite to the receiver/converter by laser beam. The satellite components are: (1) solar collector; (2) blackbody; (3) photovoltaic cells; (4) heat radiators; (5) laser system; and (6) transmission optics. The receiver/converter components are: receiver dish; lenticular lens; photocells; and heat radiator. Although the system can be adapted to missions at many locations in the solar system, only two are examined here: powering a lunar habitat; and powering a lunar rover. Power system components are described and their masses, dimensions, operating powers, and temperatures, are estimated using known or feasible component capabilities. The critical technologies involved are discussed and other potential missions are mentioned.

Williams, M. D.↗
NASA NTRS1990

High temperature acoustic and hybrid microwave/acoustic levitators for materials processing

The physical acoustics group at the Jet Propulsion Laboratory developed a single mode acoustic levitator technique for advanced containerless materials processing. The technique was successfully demonstrated in ground based studies to temperatures of about 1000 C in a uniform temperature furnace environment and to temperatures of about 1500 C using laser beams to locally heat the sample. Researchers are evaluating microwaves as a more efficient means than lasers for locally heating a positioned sample. Recent tests of a prototype single mode hybrid microwave/acoustic levitator successfully demonstrated the feasibility of using microwave power as a heating source. The potential advantages of combining acoustic positioning forces and microwave heating for containerless processing investigations are presented in outline form.

Barmatz, Martin↗
NASA NTRS2018

New Technologies Advancing Thermophysics

Researchers at NASA Ames in California have built a new facility that uses multiple 50-kW continuous wave lasers to add the capability for simulating radiative heating on thermal protection materials. The new facility, the Laser Enhanced Arc-jet Facility (LEAF-Lite), was added to NASA Ames’s Interaction Heating Facility arc-jet and now allows for test articles to be heated by both convective and radiative heat flux, making the facility more like flight. Using this new system, researchers can now simulate radiant heating with the laser and convective heating with the arc-jet simultaneously on a single test article. During its initial test in October 2017, the lasers radiatively heated a 6” x 6” Avcoat wedge sample to 405 W/sq.cm while the arc-jet simultaneously provided 160 W/sq.cm of convective heat, resulting in a total heat flux of 565 W/sq.cm. Radiative heating is more prevalent in missions with higher atmospheric entry speeds like the Orion space capsule or interplanetary scientific probes. Later this year, scientists will expand the spot size to cover 17” x 17” to test an Orion TPS panel.

Brandis, Aaron↗
NASA NTRS1997

Laser-Induced Incandescence in Microgravity

Knowledge of soot concentration is important due to its presence and impact upon a wide range of combustion processes ranging from diffusion to premixed flames, laminar to turbulent processes and homogeneous to heterogeneous combustion. Measurement of soot volume fraction (f(sub v)) is essential to discerning its formation and growth. The presence of soot also affects other physical and chemical properties of combustion thereby affecting studies not directly concerned with either its formation or growth, such as radiative heat transfer, CO oxidation and fuel vaporization or pyrolysis rates. Microgravity offers unique opportunities for studying both soot growth and the effect of soot radiation upon flame structure and spread. Spatial scales and residence time scales are greatly extended in 0-g facilitating soot growth studies. With the varied geometries, short duration microgravity test times and time-varying processes there is a demand for measurement of f(sub v) with high spatial and temporal resolution. Laser-induced incandescence (LII) has advanced f(sub v) measurements in many 1-g combustion processes. To create laser-induced incandescence, a pulsed high intensity laser heats soot to incandescence temperatures. Using appropriate spectral and temporal detection conditions, the resulting incandescence can be selectively detected apart from the non-laser-heated soot and flame gases. Theoretical modelling and experiments have shown that the resulting incandescence is representative of f(sub v). Using an intensified array camera and a laser sheet for excitation, one- and two-dimensionally resolved LII images of f(sub v) have been obtained in 1-g. LII has been characterized and developed at NASA-Lewis for soot volume fraction determination in a wide range of 1-g combustion applications. Broadly grouped, the characterization work has included studies of excitation intensity, excitation wavelength and the optimum temporal and spectral detection conditions to enable an accurate representation of soot volume fraction by LII. Tests for special requirements imposed by different combustion processes have been performed in laminar and turbulent diffusion flames, rich sooting premixed flames, single droplet combustion, and other heterogeneous combustion. These studies demonstrated LII's high sensitivity, temporal and spatial capabilities and its geometric versatility. In contrast to the advantages offered to combustion studies by a microgravity environment, advanced diagnostics, specifically those requiring pulsed laser diagnostics have been limited due to the size, weight and power limitations in a low-gravity environment. Reported here are the first demonstrations of LII performed in a microgravity environment. Examples are shown for laminar and turbulent gas-jet diffusion flames in 0-g.

VanderWal, Randy L.↗