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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Depth/diameter relationships of fresh craters within Hesperia Planum, Mars

Meteorite impact craters represent important geological features for revealing the near-surface layers of a planetary surface. In the case of Mars, this characteristic was proposed as a useful method to study spatial variations of such attributes as the distribution of sub-surface volatiles, and heat flow. Using the Planetary Image Cartography System (PICS) software, a quantitative analysis was completed of the geometry of fresh impact craters in the Hesperia Planum region of Mars, where an uniform target material and optimum viewing geometry make possible an analysis of target effects over a large geographic region. Because of the morphologic similarity to the lunar maria, it is likely that Hesperia Planum comprises a series of flood lavas that partially infilled topographic depressions within the Martian highlands. Measurements of partially buried crater rims suggest that the lava flows within Hesperia Planum are between 200-400 m thick.

Mouginis-Mark, P. J.↗
NASA NTRS1990

Time dependency of temperature of a laser-irradiated infrared target pixel as a low-pass filter

The thermal response of a surface layer of a pixel on an infrared target simulator is discussed. This pixel is maintained at a constant temperature by a rapidly scanning laser beam. An analytical model has been developed to describe the exact temperature dependence of a pixel as a function of time for different pixel refresh rates. The top layer of the pixel surface that generates the gray-body radiation shows the temperature dependence on time that is characteristic of a low-pass filter. The experimental results agree with the analytical predictions. The application of a pulsed laser beam to a noncontact, nondestructive diagnostic technique of surface characterization for the presence of microdefects is discussed.

Scholl, Marija S.↗
NASA NTRS1994

Electrically Conductive Polyimide Films Containing Gold Surface

Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

Caplan, Maggie L.↗
NASA NTRSDate not supplied

A Procedure for Obtaining Forecast Turbulence Parameters in the Atmospheric Boundary Layer for Acoustic Propagation

Propagation through turbulence causes a mean reduction in loudness of sonic booms and in some cases can cause significant fluctuations in loudness about that mean. Understanding these effects is important for accurately planning loudness levels during upcoming community noise tests with the X-59 aircraft as well as mitigating the risk for excessive loudness due to turbulence. Current methods for modeling acoustic propagation through turbulence require several atmospheric parameters including the atmospheric boundary layer (ABL) height, friction velocity, mixed-layer velocity scale, surface-layer temperature scale, as well as ambient pressure, temperature, and humidity within the ABL. Accurate forecasts of these parameters are needed for X-59 flight planning and may also be useful for planning future supersonic aircraft certification flight tests. This presentation showcases one method for obtaining the forecast turbulence and ambient atmospheric parameters from freely available Climate Forecast System Version 2 data. Forecast parameters are compared to measurements to assess accuracy and utility.

sonic boom↗
DOE OSTI2026

Enhancing fatigue life of aluminum alloy castings through cavitation water jet peening: Experiments and simulations

This study presents an investigation into the enhancement of the fatigue life of aluminum castings through the application of cavitation water-jet peening (CWJP). CWJP harnesses the impacts of water cavitation to induce surface compressive residual stress within metallic materials. In this work, CWJP was applied to a high pressure die-cast (HPDC) Al–Si alloy A380 with three different water-jet traverse velocities. The fatigue-life improvement, evaluated in a 4-point bending configuration (stress ratio R = 0.1), was found to vary with applied stress level and ranges from 1.6 to 10 times that of the parent alloy. The data also shows that decreasing the traverse velocity results in greater compressive residual stresses within the surface layer and a concurrent increase in surface roughness. This residual stress layer extends to a depth of 400 μm below the surface, as confirmed by through-thickness residual stress and microhardness measurements. CWJP treatment effectively slows down fatigue crack propagation, as evidenced by microstructural observations of narrower striation spacing. Simulations reveal that compressive residual stresses, in addition to surface hardening during CWJP, are key to improving fatigue life. A 20% increase in surface hardness and 150 MPa compressive residual stress imposed by CWJP process provides an average 5-fold enhancement of fatigue life across different stress levels. This study demonstrates the potential of CWJP as an effective surface treatment to enhance the fatigue life of aluminum castings, such as HPDC components for automotive applications.

Al casting↗
NASA NTRS1993

A lag model for turbulent boundary layers developing over rough bleed surfaces

Boundary layer mass removal (bleed) through spanwise bands of holes on a surface is used to prevent or control separation and to stabilize the normal shock in supersonic inlets. The addition of a transport equation lag relationship for eddy viscosity to the rough wall algebraic turbulence model of Cebeci and Chang was found to improve agreement between predicted and measured mean velocity distributions downstream of a bleed band. The model was demonstrated for a range of bleed configurations, bleed rates, and local free stream Mach numbers. In addition, the model was applied to the boundary layer development over acoustic lining materials for the inlets and nozzles of commercial aircraft. The model was found to yield accurate results for integral boundary layer properties unless there was a strong adverse pressure gradient.

Lee, J.↗
DOE OSTI2023

In-situ transmission electron microscopy investigation on surface oxides thermal stability of niobium

Niobium is commonly used for superconducting quantum systems as readout resonators, capacitors, and interconnects. Structural defects at the Nb/Si and air/Nb interface may be a major source of two-level systems (TLS), which are detrimental to the device's coherence time. Thus, identifying and understanding the microscopic origin of possible TLS in Nb-based devices and their relationship to processing is key to superconducting qubit performance improvement. Here this work studied the structure and thermal stability of surface oxide on physical vapor deposited Nb films on Si wafers, using aberration-corrected (scanning) transmission electron microscopy and spectroscopy. Here, all Nb films exhibit columnar growth with strong [110] textures. After in-situ heating of the heterostructure at 360 °C inside the microscope, the initial amorphous niobium surface oxides decompose into face-centered cubic Nb nanograins in the amorphous Nb-O matrix, which may reduce microwave dissipation. Despite changes in the microstructure and chemistry of the niobium oxide surface layer due to heat treatment, the interface between the Nb and the surface oxide layer remains almost unchanged. Our comprehensive study of the Nb surface oxide decomposition mechanism may guide future superconducting qubit device optimization through interfacial scattering center and TLS minimization.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2006

Volume Ice Radiolysis in the Outer Solar System

The primary energy flux of charged particle components of the heliospheric and magnetospheric environments of the solar system is primarily carried by highly penetrating energetic particles. Although laboratory experiments on production of organics and oxidants typically only address effects on very thin surface layers, energy deposition occurs on surfaces of icy bodies of the outer solar system to meters in depth. Time scales for significant radiolytic deposition vary from thousands of years at millimeter depths on Europa to billions of years in the meters-deep regolith of Kuiper Belt Objects. Radioisotope decay (e.g., K-40) also contributes to volume radiolysis as the only energy source at much greater depths. Radiolytic oxygen is a potential resource for life within Europa and a partial source of oxygen for Saturn's magnetosphere and Titan's upper atmosphere. Interactions of very high energy cosmic rays with ices at Titan's surface may provide one of the few sources of oxidants in that highly reducing environment. The red colors of low-inclination classical Kuiper Belt Objects at 40-50 AU, and Centaur objects originating from this same population, may arise from volume radiolysis of deep ice layers below more refractory radiation crusts eroded away by surface sputtering and micrometeoroid impacts. A variety of techniques are potentially available to measure volume radiolysis products and have been proposed for study as part of the new Space Physics of Life initiative at NASA Goddard Space Flight Center. The technique of Electron Paramagnetic Resonance (EPR) has been used in medical studies to measure oxidant production in irradiated human tissue for cancer treatment. Other potential techniques include optical absorption spectroscopy and standard wet chemical analysis. These and other potential techniques are briefly reviewed for applicability to problems in solar system ice radiolysis and astrobiology.

Cooper, John F.↗