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NASA NTRS1988

Noncontact true temperature measurement, 2

A laser pyrometer was developed for acquiring the true temperature of a levitated sample. The reflectivity is measured by first expanding the laser beam to cover the entire cross-sectional surface of the diffuse target. The reflectivity calibration of this system is determined from the surface emissivity of a target with a blackbody cavity. The emissivity of the real target can then be calculated. The overall system constant is obtained by passively measuring the radiance of the blackbody cavity (emissivity = 1.0) at a known, arbitrary temperature. Since the photosensor used is highly linear over the entire operating temperature range, the true temperature of the target can then be computed. The latest results available from this on-going research indicate that true temperatures thus obtained are in very good quantitative agreement with thermocouple measured temperatures.

Lee, Mark C.↗

NASA NTRS1985

Study of photon emission by electron capture during solar nuclei acceleration, 1: Temperature-dependent cross section for charge changing processes

The study of charge changing cross sections of fast ions colliding with matter provides the fundamental basis for the analysis of the charge states produced in such interactions. Given the high degree of complexity of the phenomena, there is no theoretical treatment able to give a comprehensive description. In fact, the involved processes are very dependent on the basic parameters of the projectile, such as velocity charge state, and atomic number, and on the target parameters, the physical state (molecular, atomic or ionized matter) and density. The target velocity, may have also incidence on the process, through the temperature of the traversed medium. In addition, multiple electron transfer in single collisions intrincates more the phenomena. Though, in simplified cases, such as protons moving through atomic hydrogen, considerable agreement has been obtained between theory and experiments However, in general the available theoretical approaches have only limited validity in restricted regions of the basic parameters. Since most measurements of charge changing cross sections are performed in atomic matter at ambient temperature, models are commonly based on the assumption of targets at rest, however at Astrophysical scales, temperature displays a wide range in atomic and ionized matter. Therefore, due to the lack of experimental data , an attempt is made here to quantify temperature dependent cross sections on basis to somewhat arbitrary, but physically reasonable assumptions.

Perez-Peraza, J.↗

NASA NTRSDate not supplied

Development of a Microlith® Catalytic Oxidizer for Exploration Trace Contaminant Control

The state-of-the-art in long mission duration spacecraft trace contaminant control processes rely on high-temperature catalytic oxidation for light contaminant removal. Target compounds for oxidation include metabolic methane, carbon monoxide, and low molecular weight volatile organics such as formaldehyde and methanol. Precision Combustion, Inc. and NASA Marshall Space Flight Center have been developing and testing prototype high temperature catalytic oxidizers based on PCI’s patented Microlith® technology to meet the requirements of future spaceflight exploration missions. To this end, our latest generation Microlith oxidizer, featuring an integrated heat recuperator, was subjected to endurance testing to simulate catalyst ageing over a Mars transit mission duration. Periodic reactor health testing indicates our approach results in a robust contaminant control solution for exploration missions beyond low earth orbit. Based on the demonstrated performance of this unit, a next-generation prototype was designed to meet exploration contaminant load control demands while upgrading the prototype form and fit to match flight-compatible interfaces. Prototype design considerations intended to reduce power consumption, impacting process thermal and hydraulic performance, are discussed herein.

Trace Contaminant Control↗

NASA NTRS1964

The X-Irradiation of Hydrazine and 1,1- Dimethylhydrazine

Hydrazine and 1,1-dimethylhydrazine were radiolyzed at room temperature by using about 1 gram of liquid or 1/2 to 2 liters of vapor at room-temperature vapor pressure. A tungsten-target X-ray source operating at 300 kilovolts and 6 to 8 milliamperes (0.1 to 1.0 A) was used at intensities of 1 times 10 (sup 2) to 1 times 10 (sup 3) roentgens per minute to give total doses of 4.1 rads to 2.3 times 10 (sup 6) rads. The amounts of decomposition were dependent on total dose and independent of dose rate. In the case of hydrazine vapor, the decomposition was also directly related to surface area. There was a lesser surface effect with liquid hydrazine, but this variable was not studied for 1,1-dimethylhydrazine. The order of decreasing sensitivity to X-radiation is as follows: hydrazine vapor, 1,1-dimethylhydrazine vapor, 1,1-dimethylhydrazine liquid, and hydrazine liquid. The decomposition products of hydrazine were nitrogen, hydrogen, ammonia, and unidentified products. The same products plus methylamine, dimethylamine, and hydrazine were found from the decomposition of 1,1-dimethylhydrazine. In addition, the 1,1-dimethylhydrazine underwent post-irradiation changes. Values for G (number of molecules of sample decomposed per 100 electronvolts of absorbed energy) of the order of 10 (sup 6) suggest that the vapor-phase decompositions are chain reactions.

X-RAY IRRADIATION↗

NASA NTRS1981

Geological and geothermal investigations for HCMM-derived data

An attempt was made to match HCMM- and U2HCMR-derived temperature data over two test sites of very local size to similar data collected in the field at nearly the same times. Results indicate that HCMM investigations using resolutions cells of 500 m or so are best conducted with areally-extensive sites, rather than point observations. The excellent quality day-VIS imagery is particularly useful for lineament studies, as is the DELTA-T imagery. Attempts to register the ground observed temperatures (even for 0.5 sq mile targets) were unsuccessful due to excessive pixel-to-pixel noise on the HCMM data. Several computer models were explored and related to thermal parameter value changes with observed data. Unless quite complex models, with many parameters which can be observed (perhaps not even measured (perhaps not even measured) only under remote sensing conditions (e.g., roughness, wind shear, etc) are used, the model outputs do not match the observed data. Empirical relationship may be most readily studied.

Lyon, R. J. P.↗

NASA NTRS1993

A conceptual design study for a two-dimensional, electronically scanned thinned array radiometer

A conceptual design for the Two-Dimensional, Electronically Steered Thinned Array Radiometer (ESTAR) is described. This instrument is a synthetic aperture microwave radiometer that operates in the L-band frequency range for the measurement of soil moisture and ocean salinity. Two auxiliary instruments, an 8-12 micron, scanning infrared radiometer and a 0.4-1.0 micron, charge coupled device (CCD) video camera, are included to provided data for sea surface temperature measurements and spatial registration of targets respectively. The science requirements were defined by Goddard Space Flight Center. Instrument and the spacecraft configurations are described for missions using the Pegasus and Taurus launch vehicles. The analyses and design trades described include: estimations of size, mass and power, instrument viewing coverage, mechanical design trades, structural and thermal analyses, data and communications performance assessments, and cost estimation.

Mutton, Philip↗

NASA NTRS2000

Chandra and the Emission Line Project

Calibration data obtained for the Chandra High Energy Transmission Grating and the Low Energy Transmission Grating Spectrometers are allowing us to test plasma spectral models against bright coronal sources with a range of electron temperatures. The three Emission Line Project targets - Capella, Procyon, and HR 1099 - are bright, well-studied X-ray and EUV emitters. The goals of the Emission Line Project are to determine and verify accurate and robust diagnostics; to identify and prioritize problems in fundamental spectroscopy; and to accelerate the improvement of the atomic database needed for modeling.

Brickhouse, N. S.↗

NASA NTRS2001

Flame Synthesis Used to Create Metal-Catalyzed Carbon Nanotubes

Metal-catalyzed carbon nanotubes are highly ordered carbon structures of nanoscale dimensions. They may be thought of as hollow cylinders whose walls are formed by single atomic layers of graphite. Such cylinders may be composed of many nested, concentric atomic layers of carbon or only a single layer, the latter forming a single-walled carbon nanotube. This article reports unique results using a flame for their synthesis. Only recently were carbon nanotubes discovered within an arc discharge and recognized as fullerene derivatives. Today metal-catalyzed carbon nanotubes are of great interest for many reasons. They can be used as supports for the metal catalysts like those found in catalytic converters. Open-ended nanotubes are highly desirable because they can be filled by other elements, metals or gases, for battery and fuel cell applications. Because of their highly crystalline structure, they are significantly stronger than the commercial carbon fibers that are currently available (10 times as strong as steel but possessing one-sixth of the weight). This property makes them highly desirable for strengthening polymer and ceramic composite materials. Current methods of synthesizing carbon nanotubes include thermal pyrolysis of organometallics, laser ablation of metal targets within hydrocarbon atmospheres at high temperatures, and arc discharges. Each of these methods is costly, and it is unclear if they can be scaled for the commercial synthesis of carbon nanotubes. In contrast, flame synthesis is an economical means of bulk synthesis of a variety of aerosol materials such as carbon black. Flame synthesis of carbon nanotubes could potentially realize an economy of scale that would enable their use in common structural materials such as car-body panels. The top figure is a transmission electron micrograph of a multiwalled carbon nanotube. The image shows a cross section of the atomic structure of the nanotube. The dark lines are individual atomic layer planes of carbon, seen here in cross section. They form a nested series of concentric cylinders, much like the growth rings on a tree. This sample was obtained by the supported catalyst method, whereby the nanoscale catalysts are dispersed on a substrate providing their support. The substrate with catalyst particles was immersed within an acetylene diffusion flame to which nitrogen had been added to eliminate soot formation. Upon removal from the flame, the nanotubes were dispersed on a holder suitable for electron microscopy. Although not seen in the figure, the tube diameter reflects that of the catalyst particle.

VanderWal, Randy L.↗

NASA NTRS2005

EOS Aura MLS, first year post-launch engineering assessment

This paper discusses the current status of the MLS instrument which now continuously provides data to produce global maps of targeted chemical species as well as temperature, cloud ice, and gravity wave activity. Performance trends are assessed with respect to characterization during initial on-orbit activiation of the instrument, and with data from ground test verification prior to launch.

Microwave Limb Sounder (MLS)↗

NASA NTRS2007

Functionalization of carbon nanotubes

Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H.sub.2 or F.sub.2 or C.sub.nH.sub.m) is irradiated to provide a cold plasma of selected target particles, such as atomic H or F, in a first chamber. The target particles are directed toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec.

Khare, Bishun N.↗

NASA NTRS2007

Functionalization of Carbon Nanotubes

Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H2, or F2, or CnHm) is irradiated to provide a cold plasma of selected target particles, such as atomic H or F, in a first chamber. The target particles are directed toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec.

Khare, Bishun N.↗

NASA NTRS2010

Selective functionalization of carbon nanotubes based upon distance traveled

Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H.sub.2 or NH.sub.3 or NF.sub.3 or F.sub.2 or CF.sub.4 or C.sub.nH.sub.m) is irradiated to provide a cold plasma of selected target particles, such as atomic H or F, in a first chamber. The target particles are directed toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec. The predominant species that are deposited on the CNT array vary with the distance d measured along a path from the precursor gas to the CNT array; two or three different predominant species can be deposited on a CNT array for distances d=d1 and d=d2>d1 and d=d3>d2.

Khare, Bishun N.↗

NASA NTRS2013

The Use of the Deep Convective Cloud Technique (DCCT) to Monitor On-Orbit Performance of the Geostationary Lightning Mapper (GLM): Use of Lightning Imaging Sensor (LIS) Data as Proxy

The Geostationary Lightning Mapper (GLM) on the next generation Geostationary Operational Environmental Satellite-R (GOES-R) will not have onboard calibration capability to monitor its performance. The Lightning Imaging Sensor (LIS) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite has been providing observations of total lightning over the Earth's Tropics since 1997. The GLM design is based on LIS heritage, making it a good proxy dataset. This study examines the performance of LIS throughout its time in orbit. This was accomplished through application of the Deep Convective Cloud Technique (DCCT) (Doelling et al., 2004) to LIS background pixel radiance data. The DCCT identifies deep convective clouds by their cold Infrared (IR) brightness temperatures and using them as invariant targets in the solar reflective portion of the solar spectrum. The GLM and LIS operate in the near-IR at a wavelength of 777.4 nm. In the present study the IR data is obtained from the Visible Infrared Sensor (VIRS) which is collocated with LIS onboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The DCCT is applied to LIS observations for July and August of each year from 1998-2010. The resulting distributions of LIS background DCC pixel radiance for each July August are very similar, indicating stable performance. The mean radiance of the DCCT analysis does not show a long term trend and the maximum deviation of the July August mean radiance for each year is within 0.7% of the overall mean. These results demonstrate that there has been no discernible change in LIS performance throughout its lifetime. A similar approach will used for monitoring the performance of GLM, with cold clouds identified using IR data from the Advanced Baseline Imager (ABI) which will also be located on GOES-R. Since GLM is based on LIS design heritage, the LIS results indicate that GLM should also experience stable performance over its lifetime.

Buechler, Dennis E.↗

NASA NTRS2014

Collisional Effects on Magnesium-rich Minerals found in Comets and Asteroids

While generally touted to be the least-altered bodies remaining from the age of the solar system's formation, comets and asteroids have undergone evolutionary processing throughout the 4.5-billion-year lifetime of the solar system. They have suffered the effects of collisions by impactors ranging in size from micrometeoroids to other comets and asteroids. As such, we must ask ourselves: can we detect these evolutionary effects remotely through telescopic observations? With this in mind, a suite of experiments were conducted, impacting magnesium-rich minerals as analogues to those that have been detected in the spectra of both asteroid surfaces and in the dust of cometary comae, including forsterite (Mg2SiO4, olivine), orthoenstatite (Mg2SiO3, pyroxene), diopside (MgCaSi2O6, monoclinic pyroxene), and magnesite (MgCO3, carbonate). These minerals were impacted at velocities ranging from 2.0 km/s to 2.8 km/s using the vertical gun in the Experimental Impact Laboratory (EIL) at NASA Johnson Space Center. These speeds mimic typical velocities of impacts occurring in the Kuiper belt [1]. Two classes of projectile were used: spherical alumina ceramic, whose density mimics that of rock, and cylinders made from the same material that they impacted (e.g., forsterite impactors for forsterite targets, etc.). The peak shock pressure varies significantly, depending on the target and impactor materials and the velocity; thus, shock effects differed in targets impacted at the same velocity but with compositionally different projectiles. The results indicate both: (a) how varying the impactor-density might change the outcome from a scientific viewpoint, as well as (b) possible contamination effects of the ceramic projectile in the resultant spectra of the target minerals from an experimental perspective. Temperature effects were also investigated by impacting samples at both 25 deg. and -25 deg. to: (a) probe whether the varying temperatures experienced by small bodies plays a role in the resultant spectra, and (b) constrain necessary experimental parameters. Analysis of Fourier Transform Infrared (FTIR) spectra obtained from the experimentally shocked materials shows clear indications of spectral shifts in wavelength, as well as a change in relative peak strengths of the spectral signatures at one wavelength compared with another, in all minerals except magnesite. Samples of the forsterite and orthoenstatite that displayed the spectral changes were examined with a transmission electron microscope, which revealed evidence of planar dislocations. The density of the dislocations in the experimentally shocked minerals mimicked the dislocation densities measured in both forsterite and enstatite grains recovered from Comet Wild 2 by the Stardust mission [2, 3, 4]. Further discussion on analyses of peak shock pressure and temperature-dependent effects can be found in Jensen et al., this meeting

Lederer, S.↗

NASA NTRS2019

Computational Materials Techniques for Thermal Protection Solutions: Materials and Process Design

Integrated computational materials techniques that span the atomistic and continuum scales have the potential to aid the design and manufacturing of thermal protection materials. Two cases demonstrating the practical application of these methods are discussed. Case one examines the selection of a high temperature coating for carbon/carbon, with the target application being a solar thermal propulsion heat exchanger. The performance of various refractory metal and metal-carbide coatings is characterized considering extreme thermal (3500 K) and chemical (hydrogen flows) conditions. The recession rate, hydrogen leakage, and likelihood of mechanical failure are characterized and provide directions for further experimental investigation. Case two examines the process optimization of a heat shield material composed of a woven silica fiber preform and cyanate ester resin. Frequently, internal voids were found to be present in this composite after the resin infusion and curing stages of manufacturing. Using the manufacturing conditions, computations indicate that both water adsorption and resin cure shrinkage are contributing factors to void formation. The results suggest an alternative process configuration for curing that would mitigate voids.

thermal protection↗

NASA NTRS2019

Computational Materials Techniques for Thermal Protection Solutions: Materials and Process Design

Integrated computational materials techniques that span the atomistic and continuum scales have the potential to aid the design and manufacturing of thermal protection materials. Two cases demonstrating the practical application of these methods are discussed. Case one examines the selection of a high temperature coating for carbon/carbon, with the target application being a solar thermal propulsion heat exchanger. The performance of various refractory metal and metal-carbide coatings is characterized considering extreme thermal (3500 degrees Kelvin) and chemical (hydrogen flows) conditions. The recession rate, hydrogen leakage, and likelihood of mechanical failure are characterized and provide directions for further experimental investigation. Case two examines the process optimization of a heat shield material composed of a woven silica fiber preform and cyanate ester resin. Frequently, internal voids were found to be present in this composite after the resin infusion and curing stages of manufacturing. Using the manufacturing conditions, computations indicate that both water adsorption and resin cure shrinkage are contributing factors to void formation. The results suggest an alternative process configuration for curing that would mitigate voids.

Thermal Protection↗

NASA NTRS2018

Computational Materials Techniques for Thermal Protection Solutions: Materials and Process Design

Haskins, Justin↗

NASA NTRSDate not supplied

Combined Analysis of NASA's High Efficiency Megawatt Motor and Its Converter

NASA’s High Efficiency Megawatt Motor (HEMM) is being developed to achieve the performance needed by single aisle class electrified aircraft. It is a 1.4 MW electric machine designed as a generator for NASA’s STARC-ABL concept vehicle. It has performance objectives of greater than 16 kW/kg electromagnetic specific power and efficiency of greater than 98%. The key enabling technology for HEMM’s high performance metrics is a superconducting rotor cooled by an integrated cryocooler. HEMM’s integrated cryocooler is being designed to only lift 50 W of heat at its target 50 K cold tip operating temperature. HEMM’s superconducting rotor therefore needs to have essentially zero electromagnetic losses in order to stay below the 50 W heat rejection limit of the cryocooler. This paper presents the combined analysis of HEMM and a preliminarily designed HEMM converter to analyze the rotor loss impact of several potential converter filter topologies. The analysis results point to interleaving and series inductance filters not being sufficient to suppress switching harmonic caused rotor loss. Paths forward to develop a converter to eliminate rotor loss are discussed.

Matthew Granger↗