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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Towards a heat- and mass-balanced kinetic model of TATB decomposition

We report TATB (1,3,5-triamino-2,4,6-trinitrobenzene) was thermally degraded by two small-scale analytical methods – simultaneous differential scanning calorimetry and thermogravimetric analysis (SDT) and a hot-stage microscope with Fourier Transform Infrared (FTIR) analysis capabilities. SDT used ramped heating, isothermal soaking, and thermal pretreatment at various conditions. The heat flow and mass loss were monitored during various treatment conditions to derive chemical decomposition kinetics and Arrhenius parameters. FTIR experiments used isothermal heating, and changes were monitored spectroscopically. Solid samples generated at specific conditions were collected from both methods and were analyzed by DMSO extraction followed by chemical speciation by optical and mass spectrometric methods. Characterization provided the following reaction insights: TATB decreases in a sigmoidal pattern in isothermally heated samples. Other soluble products gradually increase in concentration and then abruptly decline in concentration during the second exotherm, such as diamino-dinitro-benzofurazan and amino-nitro-benzodifurazan. FTIR showed gradual changes in the amino and nitro functionality, shifting positions and decreasing intensity for the first 40 min. Then the solid gradually appeared more like an amorphous C with N incorporated, similar to previous studies on thermally degraded TATB-type materials. Extracted residues (DMSO-soluble components removed) examined by FTIR showed an abrupt change in chemical composition between 40- and 45-min isothermal treatment, indicating early forming solids are different than later forming residues. A reliable mass- and energy-balanced global reaction network must include at least two autocatalytic reactions, either in parallel or series, and at least one must have an explicit initiation reaction having a low activation energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Two encounters with the flank low-latitude boundary layer - Further evidence for closed field topology and investigation of the internal structure

The structure of the flank low-latitude boundary layer (LLBL) is examined through differential energy spectra and particle angular anisotropies for traversals of the dawn flank (December 19, 1977) and dusk flank (July 7, 1978) during periods of predominantly northward magnetosheath field orientation. Spectra are presented that were obtained from combined ISEE 1 low-energy-proton and electron-differential-energy-analyzer and medium-energy-particle-instrument data extending over the 200-eV/q to 2-MeV energy range for the plasma sheet, stagnation region, outer LLBL, and magnetosheath regions. The stagnation region and the outer LLBL are each a mixture of plasma-sheet and magnetosheath populations, but the stagnation region contains a relatively higher fraction of plasma sheet particles, consistent with its placement earthward of the outer LLBL. Evidence for energization of thermal electrons appears during the dusk flank crossing. Bidirectional field-aligned ion distributions are observed with typically 5-to-1 enhancement of the flux along the magnetic field during certain portions of the dusk flank crossing.

Traver, D. P.↗
NASA NTRS2017

Mars Phoenix Scout Thermal Evolved Gas Analyzer (TEGA) Database: Thermal Database Development and Analysis

The Mars Phoenix Scout Lander mission in 2008 examined the history of water, searched for organics, and evaluated the potential for past/present microbial habitability in a martian arctic ice-rich soil [1]. The Thermal Evolved Gas Analyzer (TEGA) instrument measured the isotopic composition of atmospheric CO2 and detected volatile bearing mineralogy (perchlorate, carbonate, hydrated mineral phases) in the martian soil [2-7]. The TEGA data are archived at the Planetary Data System (PDS) Geosciences Node but are reported in forms that require further processing to be of use to the non-TEGA expert. The soil and blank TEGA thermal data are reported as duty cycle and must be converted to differential power (mW) to allow for enthalpy calculations of exothermic/endothermic transitions. The exothermic/endothermic temperatures are also used to determine what phases (inorganic/organic) are present in the sample. The objectives of this work are to: 1) Describe how interpretable thermal data can be created from TEGA data sets on the PDS and 2) Provide additional thermal data interpretation of two Phoenix soils (Baby Bear, Wicked Witch) and include interpretations from three unreported soils (Rosy Red 1, 2, and Burning Coals).

Sutter, B.↗
NASA NTRS2012

Processing and Damage Tolerance of Continuous Carbon Fiber Composites Containing Puncture Self-Healing Thermoplastic Matrix

Research at NASA Langley Research Center (NASA LaRC) has identified several commercially available thermoplastic polymers that self-heal after ballistic impact and through-penetration. One of these resins, polybutadiene graft copolymer (PB(sub g)), was processed with unsized IM7 carbon fibers to fabricate reinforced composite material for further evaluation. Temperature dependent characteristics, such as the degradation point, glass transition (T(sub g)), and viscosity of the PBg polymer were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic parallel plate rheology. The PBg resin was processed into approximately equal to 22.0 cm wide unidirectional prepreg tape in the NASA LaRC Advanced Composites Processing Research Laboratory. Data from polymer thermal characterization guided the determination of a processing cycle used to fabricate quasi-isotropic 32-ply laminate panels in various dimensions up to 30.5cm x 30.5cm in a vacuum press. The consolidation quality of these panels was analyzed by optical microscopy and acid digestion. The process cycle was further optimized based on these results and quasi-isotropic, [45/0/-45/90]4S, 15.24cm x 15.24cm laminate panels were fabricated for mechanical property characterization. The compression strength after impact (CAI) of the IM7/pBG composites was measured both before and after an elevated temperature and pressure healing cycle. The results of the processing development effort of this composite material as well as the results of the mechanical property characterization are presented in this paper.

Grimsley, Brian W.↗
NASA NTRS1982

The thermal structure of solar coronal loops and implications for physical models of coronae

EUV spectra of three active region loops observed above the solar limb with the SO55 spectrometer on Skylab are analyzed. It is noted that the lengths, peak temperatures, and pressures of the loops are typical of the X-ray coronal loops to which static models have been applied. It is found that the physical parameters of the coronal loop plasma derived from EUV spectra and raster pictures are not well represented by the static models. Although the loops also contain a significant quantity of cool plasma, no physical reason is found to differentiate them from other active region loops of similar length, pressure, and temperature. Several line ratios in the loop spectrum suggest departures from ionization equilibrium caused by rapid cooling. The source of this cooling material is discussed with reference to several models of loop dynamics.

Raymond, J. C.↗
NASA NTRS1996

Non-Isothermal Calorimetric Studies of the Crystallization of Lithium Disilicate Glass

The influence of preannealing treatments on the polymorphic crystallization of lithium disilicate glasses is examined. As expected, glasses heated at different rates through the temperature range where there is significant nucleation develop widely different numbers of nuclei. This can dramatically influence the stability and transformation characteristics of the annealed glass. Non-isothermal differential scanning calorimetry (DSC) and differential thermal analysis (DTA) measurements are demonstrated to be useful to probe the nucleation behavior. The first systematic investigations of particle size effects on the non-isothermal transformation behavior are presented and discussed. Based on DTA and microscopy experiments, we show that small particles of lithium disilicate glasses crystallize primarily by surface crystallization. The relative importance of surface versus volume crystallization is examined by varying particle size, by introducing nucleating agents and by exposing glasses to atmospheres of different water content. These data are analyzed quantitatively using a numerical model developed in a second paper following in this volume.

Ray, C. S.↗
NASA NTRS1974

Using the NASTRAN Thermal Analyzer to simulate a flight scientific instrument package

The NASTRAN Thermal Analyzer has proven to be a unique and useful tool for thermal analyses involving large and complex structures where small, thermally induced deformations are critical. Among its major advantages are direct grid point-to-grid point compatibility with large structural models; plots of the model that may be generated for both conduction and boundary elements; versatility of applying transient thermal loads especially to repeat orbital cycles; on-line printer plotting of temperatures and rate of temperature changes as a function of time; and direct matrix input to solve linear differential equations on-line. These features provide a flexibility far beyond that available in most finite-difference thermal analysis computer programs.

Lee, H.-P.↗
NASA NTRS1981

Modification of spacecraft potentials by thermal electron emission on ATS-5

Electron emission experiments on Applied Technology Satellite 5 using a thermal electron emitter are reported and analyzed. Operations in eclipse charging environments showed that electron emission could partially discharge a negatively charged satellite. Typical operations resulted in kilovolt potentials being reduced to hundreds of volts for a few tens of seconds, followed by a gradual recharging over a period of minutes. Equilibrium currents were modeled with a one-dimensional current balance model. Currents on the order of 1 microampere were found, significantly below emitter capabilities. Application of a three-dimensional, time-dependent computer model showed that differential charging on the solar arrays was limiting the emitted current, preventing the complete discharge of the satellite, and allowing it to recharge in spite of the electron emitter.

Olsen, R. C.↗
NASA NTRS1952

An empirically derived basis for calculating the area, rate, and distribution of water-drop impingement on airfoils

An empirically derived basis for predicting the area, rate, and distribution of water-drop impingement on airfoils of arbitrary section is presented. The concepts involved represent an initial step toward the development of a calculation technique which is generally applicable to the design of thermal ice-prevention equipment for airplane wing and tail surfaces. It is shown that sufficiently accurate estimates, for the purpose of heated-wing design, can be obtained by a few numerical computations once the velocity distribution over the airfoil has been determined. The calculation technique presented is based on results of extensive water-drop trajectory computations for five airfoil cases which consisted of 15-percent-thick airfoils encompassing a moderate lift-coefficient range. The differential equations pertaining to the paths of the drops were solved by a differential analyzer.

Bergrun, Norman R↗
NASA NTRS1986

Undercooled and rapidly quenched Ni-Mo alloys

Hypoeutectic, eutectic, and hypereutectic nickel-molybdenum alloys were rapidly solidified by both bulk undercooling and melt spinning techniques. Alloys were undercooled in both electromagnetic levitation and differential thermal analysis equipment. The rate of recalescence depended upon the degree of initial undercooling and the nature (faceted or nonfaceted) of the primary nucleating phase. Alloy melts were observed to undercool more in the presence of primary Beta (NiMo intermetallic) phase than in gamma (fcc solid solution) phase. Melt spinning resulted in an extension of molybdenum solid solubility in gamma nickel, from 28 to 37.5 at % Mo. Although the microstructures observed by undercooling and melt spinning were similar the microsegregation pattern across the gamma dendries was different. The range of microstructures evolved was analyzed in terms of the nature of the primary phase to nucleate, its subsequent dendritic growth, coarsening and fragmentation, and final solidification of interfenderitic liquid.

Tewari, S. N.↗
NASA NTRS1988

The crystallization of tough thermoplastic resins in the presence of carbon fibers

The presence of carbon fibers increased the crystallization rates of both PEEK and PPS thermoplastic polymers. The effect was most pronounced at higher crystallization temperatures. Isothermal crystallization rates were analyzed by applying classical phenomenological nucleation theory. Unusually high values of the so-called Avrami exponent were found for neat PEEK. Isothermal crystallization of PEEK and PPS polymers produced crystalline samples having a wide variety of melting temperatures. The melting as observed by differential scanning calorimetry occurred as dual endotherms which were called primary (higher temperature) and secondary melting peaks. Each primary peak accounted for most of the crystallinity present. The secondary peaks represented the melting of crystallites formed later than those attributable to the primary endotherms. The presence of carbon fibers increased the thermal stability of both PEEK and PPS crystallites as manifested by higher temperatures for the primary melting peaks. This may be attributable to increased crystallite size, greater crystallite perfection, and/or favorable modification of the crystallite interface. Over the range studied, crystallization temperature strongly influenced the positions of the secondary peaks but not the primary peaks.

Theil, Michael H.↗
NASA NTRS1987

Undercooled and rapidly quenched Ni-Mo alloys

Hypoeutectic, eutectic, and hypereutectic nickel-molybdenum alloys were rapidly solidified by both bulk undercooling and melt spinning techniques. Alloys were undercooled in both electromagnetic levitation and differential thermal analysis equipment. The rate of recalescence depended upon the degree of initial undercooling and the nature (faceted or nonfaceted) of the primary nucleating phase. Alloy melts were observed to undercool more in the presence of primary Beta (NiMo intermetallic) phase than in gamma (fcc solid solution) phase. Melt spinning resulted in an extension of molybdenum solid solubility in gamma nickel, from 28 to 37.5 at. pct Mo. Although the microstructures observed by undercooling and melt spinning were similar, the microsegregation pattern across the gamma dendries was different. The range of microstructures evolved was analyzed in terms of the nature of the primary phase to nucleate, its subsequent dendritic growth, coarsening and fragmentation, and final solidification of interfenderitic liquid.

Tewari, S. N.↗
NASA NTRS1951

An Empirical Method Permitting Rapid Determination of the Area, Rate and Distribution of Water-Drop Impingement on an Airfoil of Arbitrary Section at Subsonic Speeds

An empirical method for the determination of the area, rate, and distribution of water-drop impingement on airfoils of arbitrary section is presented. The procedure represents an initial step toward the development of a method which is generally applicable in the design of thermal ice-prevention equipment for airplane wing and tail surfaces. Results given by the proposed empirical method are expected to be sufficiently accurate for the purpose of heated-wing design, and can be obtained from a few numerical computations once the velocity distribution over the airfoil has been determined. The empirical method presented for incompressible flow is based on results of extensive water-drop. trajectory computations for five airfoil cases which consisted of 15-percent-thick airfoils encompassing a moderate lift-coefficient range. The differential equations pertaining to the paths of the drops were solved by a differential analyzer. The method developed for incompressible flow is extended to the calculation of area and rate of impingement on straight wings in subsonic compressible flow to indicate the probable effects of compressibility for airfoils at low subsonic Mach numbers.

Bergrun, N. R.↗
NASA NTRS2005

Development of Particulates and Aerosols Research

During the past year several accomplishments were made for both the Particulate Matter Characterization and Measurement System, (PMCMS) and PAGEMS projects. The PAGEMS focus is to measure particulate emissions as a function of combustor parameters such as inlet temperature, inlet pressure and fuel air ratio. These measurements are used to evaluate combustor performance in hopes of correlating particulate emissions with engine conditions. These measurements have taken place at in-house NASA combustor facilities and off-site facilities. Ths work is unique because particulate measurements at high- pressure conditions are not commonly made. Some calibration of the PAGEMS instrumentation was done as well as minor modifications to the PAGEMS plumbing setup. These led to measurement improvements. The instrumentation and measurement process for PAGEMS was assessed and new instruments such as a thermodenuder, thermal mass flow meters and a cyclone separator were purchased to improve the PAGEMS instrumentation and measurement process. A worksheet was created to simulate varying inlet conditions to the DMA. This worksheet allows the user to assess the error in the measurements when certain conditions exist. Two technical papers were written with the PAGEMS team for the EXCAVATE field project. A paper was also reviewed for an in house publication. Also data was processed and analyzed for another field project (PAX) and will be part of a third PAGEMS paper. Accomplishments were also made with the PMCMS project. The calibration of the radial differential mobility analyzer, (RDMA) in the particle sizing system in the PMCMS was completed and provided satisfactory results. The voltages used for the RDMA depending on the particle of interest were corrected. The measurement capability of the PMCMS was increased by replacing the MetOne CPC with a TSI CPC. Lastly, assistance was provided to three college summer students with calibration of their particulate equipment and Monica Rivera shared her understanding of the aerosol technology with them. She also provided input for their end of the summer presentations. And attended the Aviation and Particle Emissions workshop. This workshop brought together experts in the aircraft particulate emissions field. As a result Ms. Rivera made two significant contacts with academia (UMR) and government (WPAFB) which could lead to future collaboration. She also attended the Aerosol and Particle Measurement Class held at the University of Minnesota. This class refreshed her particulate knowledge and introduced her to new aerosol applications and technology. Furthermore at the class contacts were made with private industry (TSI) and government (WPAFB). Ms. Rivera also enhanced her education by taking an in-house class on aircraft design and operation.

DeWitt, Kenneth↗
NASA NTRS1991

Analysis of the fluid flow and heat transfer in a thin liquid film in the presence and absence of gravity

The hydrodynamic and thermal behavior of a thin liquid film flowing over a solid horizontal surface is analyzed for both plane and radially spreading flows. The situations where the gravitational force is completely absent and where it is significant are analyzed separately and their practical relevance to a micro-gravity environment is discussed. In the presence of gravity, in addition to Reynolds number, the Froude number of the film is found to be an important parameter that determines the supercritical and subcritical flow regimes and any associated hydraulic jump. A closed-form solution is possible under some flow situations, whereas others require numerical integration of ordinary differential equations. The approximate analytical results are found to compare well with the available two-dimensional numerical solutions.

Rahman, M. M.↗
NASA NTRS2008

Controlling Charging and Arcing on a Solar Powered Auroral Orbiting Spacecraft

The Global Precipitation Measurement satellite (GPM) will be launched into a high inclination (65 degree) orbit to monitor rainfall on a global scale. Satellites in high inclination orbits have been shown to charge to high negative potentials, with the possibility of arcing on the solar arrays, when three conditions are met: a drop in plasma density below approximately 10,000 cm(exp -3), an injection of energetic electrons of energy more that 7-10 keV, and passage through darkness. Since all of these conditions are expected to obtain for some of the GPM orbits, charging calculations were done using first the Space Environment and Effects (SEE) Program Interactive Spacecraft Charging Handbook, and secondly the NASA Air-force Spacecraft Charging Analyzer Program (NASCAP-2k). The object of the calculations was to determine if charging was likely for the GPM configuration and materials, and specifically to see if choosing a particular type of thermal white paint would help minimize charging. A detailed NASCAP-2k geometrical model of the GPM spacecraft was built, with such a large number of nodes that it challenged the capability of NASCAP-2k to do the calculations. The results of the calculations were that for worst-case auroral charging conditions, charging to levels on the order of -120 to -230 volts could occur on GPM during night-time, with differential voltages on the solar arrays that might lead to solar array arcing. In sunlit conditions, charging did not exceed -20 V under any conditions. The night-time results were sensitive to the spacecraft surface materials chosen. For non-conducting white paints, the charging was severe, and could continue unabated throughout the passage of GPM through the auroral zone. Somewhat conductive (dissipative) white paints minimized the night-time charging to levels of -120 V or less, and thus were recommended for GPM thermal control. It is shown that the choice of thermal control paints is important to prevent arcing on high inclination orbiting spacecraft solar arrays as well as for GEO satellites, even for solar array designs chosen to minimize arcing.

Ferguson, Dale C.↗
NASA NTRS1987

Ram ion scattering caused by Space Shuttle v x B induced differential charging

Observations of secondary, high-inclination ions streams have been reported in the literature. The authors of these previous papers attributed the source of the secondary ions to a disturbed region in the plasma about 10 m from the Space Shuttle Orbiter. A new theory has been developed which shows how v x B induced differential charging on the plasma diagnostics package (PDP) can scatter the ram ion flux. Some of these ions are reflected back to the PDP and may be the sorce of the observed ion distributions. The effect is unique to large spacecraft; it occurs only when the magnitude of the induced v x B potentials are much larger than the electron thermal energy and of the order of the ion ram energy. That the ion streams observed at large angles must have been reflected from the PDP surface is demonstrated with three-dimensional sheath and particle trajectory calculations using the low earth orbit version of the NASA Charging Analyzer Program (NASCAP/LEO).

Katz, I.↗