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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Effects of thermal cycling on graphie-fiber-reinforced 6061 aluminum

Graphite-reinforced aluminum alloy metal-matrix composites are among materials being considered for structural components in dimensionally stable space structures. This application requires materials with low values of thermal expansions and high specific stiffnesses. They must remain stable during exposures to the space environment for periods extending to 20 years. The effects of thermal cycling on the thermal expansion behavior and mechanical properties of Thornel P100 graphite 6061 aluminum composites, as fabricated and after thermal processing to eliminate thermal strain hysteresis, have been investigated. Two groups of composites were studied: one was fabricated by hot roll bonding and the other by diffusion bonding. Processing significantly reduced strain hysteresis during thermal cycling in both groups and improved the ultimate tensile strength and modulus in the diffusion-bonded composites. Thermal cycling stabilized the as-fabricated composites by reducing the residual fabrication stress and increased the matrix strength by metallurgical aging. Thermal expansion behavior of both groups after processing was insensitive to thermal cycling. Data scatter was too large to determine effects of thermal cycling on the mechanical properties. The primary effects of processing and thermal cycling can be attributed to changes in the metallurgical condition and stress state of the matrix.

Dries, G. A.↗
NASA NTRS2016

Rheological Properties of Quasi-2D Fluids in Microgravity

Freely suspended smectic films of sub-micrometer thickness and lateral extensions of several millimeters are used to study thermally driven convection and diffusion in the film plane. The experiments were performed during a six minute microgravity phase of a TEXUS suborbital rocket flight (Texus 52, launched April 27, 2015). The project served as a preliminary test for a planned ISS Experiment with liquid crystal films (OASIS), and in addition it provided new experimental data on smectic films exposed to in-plane thermal gradients.We find an attraction of the smectic material towards the cold edge of the film in a temperature gradient, similar to a Soret effect. This process is reversed when this edge is heated up again. Thermal convection driven by two thermocontacts in the film is practically absent, even at temperature gradients up to 10 Kmm, thermally driven convection sets in when the hot post reaches the transition temperature to the nematic phase.An additional experiment was performed under microgravity conditions to test the stability of liquid crystal bridges in different smectic phases.

microgravity↗
NASA NTRS1998

Frequency-Domain Analysis of Diffusion-Cooled Hot-Electron Bolometer Mixers

A new theoretical model is introduced to describe heterodyne mixer conversion efficiency and noise (from thermal fluctuation effects) in diffusion-cooled superconducting hot-electron bolometers. The model takes into account the non-uniform internal electron temperature distribution generated by Wiedemann-Franz heat conduction, and accepts for input an arbitrary (analytical or experimental) superconducting resistance-versus- temperature curve. A non-linear large-signal solution is solved iteratively to calculate the temperature distribution, and a linear frequency-domain small-signal formulation is used to calculate conversion efficiency and noise. In the small-signal solution the device is discretized into segments, and matrix algebra is used to relate the heating modulation in the segments to temperature and resistance modulations. Matrix expressions are derived that allow single-sideband mixer conversion efficiency and coupled noise power to be directly calculated. The model accounts for self-heating and electrothermal feedback from the surrounding bias circuit.

Skalare, A.↗
NASA NTRS1983

Monte Carlo simulation of steady state shock structure including cosmic ray mediation and particle escape

Both hydrodynamic calculations (Drury and Volk, 1981, and Axford et al., 1982) and kinetic simulations imply the existence of thermal subshocks in high-Mach-number cosmic-ray-mediated shocks. The injection efficiency of particles from the thermal background into the diffusive shock-acceleration process is determined in part by the sharpness and compression ratio of these subshocks. Results are reported for a Monte Carlo simulation that includes both the back reaction of accelerated particles on the inflowing plasma, producing a smoothing of the shock transition, and the free escape of particles allowing arbitrarily large overall compression ratios in high-Mach-number steady-state shocks. Energy spectra and estimates of the proportion of thermal ions accelerated to high energy are obtained.

Ellison, D. C.↗
NASA NTRS1977

Induced gyroresonant emission of extraordinary mode radiation

Induced amplification of extraordinary-mode electromagnetic waves in a magnetized plasma is investigated. The analysis is performed for a plasma which consists of two components: a relatively dense species of thermal plasma and a diffuse population of suprathermal electrons characterized by a loss cone-type distribution. The excitation mechanism is primarily due to the interaction of the electromagnetic waves with the energetic electrons via the relativistic cyclotron resonance which arises because of the momentum dependence of the gyrofrequency. The present study is particularly concerned with waves propagating perpendicularly and nearly perpendicularly with respect to the external magnetic field, since it is expected that for these cases the cyclotron damping due to thermal electrons is vanishingly small and the growth rates are maximum. The results indicate that excitation occurs primarily for frequencies near the first two gyroharmonics.

Freund, H. P.↗
NASA NTRS1980

The correlation of the cosmic X-ray background with the light of galaxies

Models for the origin of the cosmic X-ray background (CXB) radiation attribute it to numerous weak, unresolved discrete sources (e.g., active galactic nuclei), to some diffuse emission mechanism (e.g., thermal bremmstrahlung from a hot intergalactic plasma), or to an unresolved population of discrete sources which evolve substantially with redshift (e.g., quasars). It is shown that the comparison of the CXB flux variations with flux variations in the light from galaxies can measure the relative contribution of these possible sources of the CXB. Applying the technique to available Uhuru data, it is found that the absence of correlation between the optical flux variations and the X-ray flux variations sets an upper limit of approximately 50% on the fraction of the CXB originating with any classes of X-ray sources substantially represented among bright (apparent photographic magnitude less than or equal to 15.5) galaxies. The data are consistent with nearly all of the CXB being due to diffuse emission or to a class of sources whose density increases rapidly with redshift.

Turner, E. L.↗
NASA NTRSDate not supplied

Ice Growth Model for Polar Water Capture Systems

In-situ resource utilization (ISRU) is essential to NASA’s goal of sustainable and cost-effective missions to the Moon and beyond. Water has become a particular source of interest since its discovery in the permanently shadowed regions (PSRs) of the Moon. This water exists as ice bound within the regolith, so one mode of capture is heating to sublimation temperatures and capturing at very low pressure. It then can be stored in ice form and transported out of the PSR and to a sunlit ridge, where processes such as electrolysis can be performed[2]. An understanding of frost growth dynamics under rarefied conditions is necessary for successful water capture and storage due to transient thermal properties of frost. A Diffusion-Limited Aggregation (DLA) approach was taken to analytically model bulk thermal conductivity changes of the growing frost layer under varying wall temperatures and frost layer porosities. The model utilizes well-known correlations for effective thermal conductivity and records the values as the frost layer thickness increases. This thermal conductivity can be applied to a known temperature change and be used to evaluate heat flux through the combined frost layer and tank wall for either a flat plate or cylindrical geometry. An experiment is described that will evaluate this model using one-dimensional frost growth on a horizontal, flat plate under low-pressure. The ice growth will be measured using a millimeter-scale photogrammetry camera system and a load cell measured transient mass growth.

In situ Resource Utilization↗
NASA NTRSDate not supplied

Ice Growth Model for Polar Water Capture Systems

In-situ resource utilization (ISRU) is essential to NASA’s goal of sustainable and cost-effective missions to the Moon and beyond. Water has become a particular source of interest since its discovery in the permanently shadowed regions (PSRs) of the Moon. This water exists as ice bound within the regolith, so one mode of capture is heating to sublimation temperatures and capturing at very low pressure. It then can be stored in ice form and transported out of the PSR and to a sunlit ridge, where processes such as electrolysis can be performed[2]. An understanding of frost growth dynamics under rarefied conditions is necessary for successful water capture and storage due to transient thermal properties of frost. A Diffusion-Limited Aggregation (DLA) approach was taken to analytically model bulk thermal conductivity changes of the growing frost layer under varying wall temperatures and frost layer porosities. The model utilizes well-known correlations for effective thermal conductivity and records the values as the frost layer thickness increases. This thermal conductivity can be applied to a known temperature change and be used to evaluate heat flux through the combined frost layer and tank wall for either a flat plate or cylindrical geometry. An experiment is described that will evaluate this model using one-dimensional frost growth on a horizontal, flat plate under low-pressure. The ice growth will be measured using a millimeter-scale photogrammetry camera system and a load cell measured transient mass growth.

ice growth↗
NASA NTRS2022

A Record of Low-Temperature Asteroidal Processes of Amoeboid Olivine Aggregates from the Kainsaz Co3.2 Chondrite

Amoeboid olivine aggregates (AOAs) from the Kainsaz CO3.2 chondrite were analyzed using transmission electron microscopy in order to gain a more complete understanding of thermal metamorphism on the parent body and the role of fluids during metamorphic heating. The Kainsaz AOAs are dominated by strongly zoned, fine-grained, olivine grains (Fa2-31) with heterogeneous Fe enrichments along the grain boundaries, which are interpreted as the result of 26Fe2+-Mg2+ interdiffusion with the matrix during thermal metamorphism. However, our diffusion calculations show that such AOA olivine zoning and compositions cannot be produced by a simple diffusional exchange during metamorphic heating, unlike chondrule olivine zoning and compositions. In addition, fine-grained ferroan olivine overgrowths occur heterogeneously in crystallographic continuity with olivines on the AOA exteriors. The overgrowths (Fa33-36) are compositionally distinct from the underlying AOA olivines and are not fully equilibrated with the matrix olivines (Fa~20-55).The ferroan olivine overgrowths likely formed by precipitation from fluids in an epitaxial relationship with forsteritic olivine on the edges of AOAs. Texturally and compositionally diverse chromite grains are also observed along olivine grain boundaries, in olivine grains, and in pore spaces between olivine grains. They share a similar crystallographic orientation relationships with adjacent olivine, suggestive of their formation by exsolution and/or epitaxial growth. Collectively, these observations provide evidence for the mobilization of Fe, Mg, Si, Cr, and Al in the presence of fluids along olivine grain boundaries and into olivine grains during thermal metamorphism. We conclude that in Kainsaz AOAs, the strong zonation development in individual olivine grains and the formation of ferroan olivine overgrowths and chromite grains were a fluid-driven process that occurred at relatively low temperatures (<500°C), during the cooling history of the CO3 chondrite parent body, following the peak of thermal metamorphism.

Amoeboid olivine aggregates↗
NASA NTRS1994

LH2 fuel tank design for SSTO

This report will discuss the design of a liquid hydrogen fuel tank constructed from composite materials. The focus of this report is to recommend a design for a fuel tank which will be able to withstand all static and dynamic forces during manned flight. Areas of study for the design include material selection, material structural analysis, heat transfer, thermal expansion, and liquid hydrogen diffusion. A structural analysis FORTRAN program was developed for analyzing the buckling and yield characteristics of the tank. A thermal analysis Excel spreadsheet was created to determine a specific material thickness which will minimize heat transfer through the wall of the tank. The total mass of the tank was determined by the combination of both structural and thermal analyses. The report concludes with the recommendation of a layered material tank construction. The designed system will include exterior insulation, combination of metal and organize composite matrices and honeycomb.

Wright, Geoff↗
NASA NTRS1978

Rocket exhaust plume impingement on the Voyager spacecraft

In connection with the conduction of the long-duration Voyager missions to the outer planets and the sophisticated propulsion systems required, it was necessary to carry out an investigation to avoid exhaust plume impingement problems. The rarefied gas dynamics literature indicates that, for most engineering surfaces, the assumption of diffuse reemission and complete thermal accommodation is warranted in the free molecular flow regime. This assumption was applied to an analysis of a spacecraft plume impingement problem in the near-free molecular flow regime and yielded results to within a few percent of flight data. The importance of a correct treatment of the surface temperature was also demonstrated. Specular reflection, on the other hand, was shown to yield results which may be unconservative by a factor of 2 or 3. It is pointed out that one of the most difficult portions of an exhaust plume impingement analysis is the simulation of the impinged hardware. The geometry involved must be described as accurately and completely as possible.

Baerwald, R. K.↗
NASA NTRS1981

Transport properties for a mixture of the ablation products C, C2, and C3

The ablation of carbon-phenolic heat shields upon entry into the atmosphere of one of the outer planets leads to the injection of large amounts of C, C2, and C3 into the shock layer. These species must be included in the calculation of transport properties in the shock layer. The kinetic theory of gases has been used to obtain accurate results for the transport properties of monatomic carbon. The Hulburt-Hirschelder potential, the most accurate general purpose atom-atom potential for states with an attractive minimum, was used to represent such states and repulsive states were represented by fitting quantum mechanical potential energy curves with the exponential repulsive potential. These results were orientation averaged according to the peripheral force model to obtain transport collision integrals for the C-C2 and C2-C2 interaction. Results for C3 were obtained by ignoring the presence of the central carbon atom. The thermal conductivity, viscosity, and diffusion coefficients for pure C, C2, and C3, and for mixtures of these gases, were then calculated from 1000 K - 25,000 K.

Biolsi, L.↗
NASA NTRS1984

Spectral observations of the soft X-ray background with solid-state detectors - Evidence for line emissions

The soft X-ray radiation from several regions of the sky was observed with solid-state detectors Si(Li) between 0.3 and 1.2 keV during two rocket flights. The thermal nature of the diffuse emission coming from the hot bubble surrounding the solar system is confirmed by the observation of C V-C VI and O VII lines which are typical of a temperature of about 10 to the 6th K. Evidence for the existence of a weak component at a higher temperature is given. This component, well visible in the high latitude spectra, could be produced by a hot galactic halo. In the direction of the enhancement region centered on the North Polar Spur, the radiation excess spectra are well represented by a two-temperature plasma model with rather standard abundances. The two components have temperatures of 10 to the 6th and 4.7 x 10 to the 6th K.

Rocchia, R.↗
NASA NTRS1985

The equilibrium structure of thin magnetic flux tubes. I

A model atmosphere within a thin magnetic flux tube that is embedded in an arbitrarily stratified medium is presently constructed by solving the radiative transfer equation in the two-stream approximation for gray opacity, under the assumption that the magnetic field is sufficiently strong to warrant the neglect of both thermal conduction and convective diffusion; energy inside the flux tube therefore being transported solely by radiation. The structure of the internal atmosphere is determined on the basis of the hydrostatic and radiative equilibrium conditions of the tube embedded in an external atmosphere. The gas temperature along the axis of the tube is computed, and the geometry of the flux tube is determined on the basis of magnetic flux conservation and total pressure equilibrium.

Ferrari, A.↗
NASA NTRS1986

Direct simulation of typical AOTV entry flows

The direct simulation Monte Carlo method is applied to two flows that are relevant to the projected aeroassisted orbital transfer vehicle. The first is the axially symmetric flow about a 70 degree blunted cone shield with a cylindrical afterbody, and the second is the one-dimensional flow along the stagnation streamline of the first flow. The shock standoff distance for the stagnation streamline study is obtained from the full axially symmetric calculation. Advantage is then taken of the speed of the one-dimensional calculation to study the sensitivity of the stagnation point heat transfer to a number of physical variables. These include the chemical reaction rate coefficients, the surface catalycity, the electric field associated with ambipolar diffusion, and the nonequilibrium thermal radiation from the shock front.

Bird, G. A.↗