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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Deconvoluting the Friction Stir Weld Process for Optimizing Welds

In the friction stir welding process, the rotating surfaces of the pin and shoulder contact the weld metal and force a rotational flow within the weld metal. Heat, generated by the metal deformation as well as frictional slippage with the contact surface, softens the metal and makes it easier to deform. As in any thermo-mechanical processing of metal, the flow conditions are critical to the quality of the weld. For example, extrusion of metal from under the shoulder of an excessively hot weld may relax local pressure and result in wormhole defects. The trace of the weld joint in the wake of the weld may vary geometrically depending upon the flow streamlines around the tool with some geometry more vulnerable to loss of strength from joint contamination than others. The material flow path around the tool cannot be seen in real time during the weld. By using analytical "tools" based upon the principles of mathematics and physics, a weld model can be created to compute features that can be observed. By comparing the computed observations with actual data, the weld model can be validated or adjusted to get better agreement. Inputs to the model to predict weld structures and properties include: hot working properties ofthe metal, pin tool geometry, travel rate, rotation and plunge force. Since metals record their prior hot working history, the hot working conditions imparted during FSW can be quantified by interpreting the final microstructure. Variations in texture and grain size result from variations in the strain accommodated at a given strain rate and temperature. Microstructural data from a variety of FSWs has been correlated with prior marker studies to contribute to our understanding of the FSW process. Once this stage is reached, the weld modeling process can save significant development costs by reducing costly trial-and-error approaches to obtaining quality welds.

Schneider, Judy↗
NASA NTRS1972

Evaluation of thermal network correction program using test temperature data

An evaluation process to determine the accuracy of a computer program for thermal network correction is discussed. The evaluation is required since factors such as inaccuracies of temperatures, insufficient number of temperature points over a specified time period, lack of one-to-one correlation between temperature sensor and nodal locations, and incomplete temperature measurements are not present in the computer-generated information. The mathematical models used in the evaluation are those that describe a physical system composed of both a conventional and a heat pipe platform. A description of the models used, the results of the evaluation of the thermal network correction, and input instructions for the thermal network correction program are presented.

Ishimoto, T.↗
NASA NTRS1992

An investigation of the role of current and future remote sensing data systems in numerical meteorology

A flexible system for performing observing system simulation experiments which made contributions to meteorology across all elements of the observing system simulation experiment (OSSE) components was developed. Future work will seek better understanding of the links between satellite-measured radiation and radiative transfer in the clear, cloudy and precipitating atmosphere and investigate how that understanding might be applied to improve the depiction of the initial state and the treatment of physical processes in forecast models of the atmosphere.

Diak, George R.↗
NASA NTRS1972

Space shuttle orbiter heat pipe applications. Volume 1: Synopsis

An investigation was made to formulate and evaluate heat pipe applications for the space shuttle orbiter. Of the twenty-seven specific applications which were identified, a joint evaluation resulted in the selection of five of the most promising ones for prototype development. The formulation process is described, along with the applications which evolved. The bulk of the discussion deals with the top five applications: (1) heat pipe augmented cold rail; (2) avionics heat pipe circuit; (3) heat pipe/phase change material modular sink; (4) air-to-heat-pipe heat exchanger; and (5) heat pipe radiator for compartment temperature control. The philosophy, physical design details, and performance data are presented for each concept along with a comparison to the baseline design where applicable. A sixth application, heat pipe space radiator for waste heat rejection, was also recommended for prototype development.

Alario, J. P.↗
NASA NTRS1973

The application of VLB interferometry to earth measurements

Results of a four-phase development of capability in very long-baseline interferometry (VLBI) at the Smithsonian Astrophysical Observatory (SAO) are summarized. The objectives of the VLBI program at SAO are to: (1) develop the capability to collect, process, and analyze VLBI data; (2) determine experimentally the accuracy now attainable with VLBI and, within the constraints imposed by this accuracy, initiate a program of VLBI observations for geophysical applications; (3) identify all significant error sources and devise means for eliminating or correcting these errors; and (4) develop a long range plan for applying VLBI techniques to a program of earth physics measurements.

Michelini, R. D.↗
NASA NTRS1975

Assessment of practicality of remote sensing techniques for a study of the effects of strip mining in Alabama

Because of the volume of coal produced by strip mining, the proximity of mining operations, and the diversity of mining methods (e.g. contour stripping, area stripping, multiple seam stripping, and augering, as well as underground mining), the Warrior Coal Basin seemed best suited for initial studies on the physical impact of strip mining in Alabama. Two test sites, (Cordova and Searles) representative of the various strip mining techniques and environmental problems, were chosen for intensive studies of the correlation between remote sensing and ground truth data. Efforts were eventually concentrated in the Searles Area, since it is more accessible and offers a better opportunity for study of erosional and depositional processes than the Cordova Area.

Hughes, T. H.↗
NASA NTRS1988

Physical processes in the growth of the continental crust

Major mechanisms of crustal addition are volcanism and plutonism at plate boundaries and within plate interiors. One approach to deciding if island arc magmatism dominated ancient crustal growth is to assess the rate at which the process has operated in the recent past. The localized addition rates were found to be comparable to present day global rates. One physical observable that was used to constrain models of crustal growth is sea level. A simple physical model was developed to explore the consequences of constant freeboard (the height of the continents above sea level). Global geoid and sea floor topography data were used to identify and study oceanic plateaus and swells that have either continental crustal roots or anomalously thick ocean crusts.

Schubert, G.↗
NASA NTRS1991

Energy transfer processes between Tm(3+) and Ho(3+) in LiYF4

The spectroscopic properties of the crystal LiYF4 doped with Thulium (Tm) and Holmium (Ho) ions are studied. The basic processes are discussed that regulate the transfer of energy between these two ions in this crystal. In this system Tm is considered the donor ion and the Ho the acceptor ion. Spectral data were obtained on three samples available: LiYF4:Tm(3+) (0.5 percent), LiYF4:Ho(3+) (1 percent), and LiYF4:Tm(3+) (5 percent), Ho(3+) (0.2 percent). Spectral data, which include absorption, luminescence, excitation, and the response to pulsed excitation in a wide range of temperatures, allowed to look at the energy transfer processes by considering the kinetic evolution of the emission of the two ions (donor and acceptor) involved in the process and the basic spectroscopic properties related to them. This inclusive approach has led to the validation of the physical model.

Oezen, Goenuel↗
NASA NTRS1997

Cassini/Huygens Science Instruments, Spacecraft, and Mission

The Cassini spacecraft will take 18 scientific instruments to Saturn. After launch and a seven-year cruise, Cassini will arrive at Saturn and separate into a Saturn orbiter and an atmospheric probe, called Huygens, which will descend to the surface of Titan. The orbiter will orbit the planet for four years, making close flybys of five satellites, including multiple flybys of Titan. Communication with Earth is at X-band; the maximum downlink rate from Saturn is 166 x 10(exp 3) bps. Orbiter instruments are body mounted; the spacecraft must be turned to point some of them toward objects of interest. The orbiter carries 12 instruments. Optical instruments provide imagery and spectrometry. Radar supplies imaging, altimetry, and radiometry. Radio links contribute information about intervening material and gravity fields. Other instruments measure electromagnetic fields and the properties of plasma, energetic particles, and dust particles. The probe is spin stabilized. It returns data via an S-band link to the orbiter. The probe's six instruments include sensors to determine atmospheric physical properties and composition. Radiometric and optical sensors will produce data on thermal balance and obtain images of Titan's atmosphere and surface. Doppler measurements between probe and orbiter will provide wind profiles. Surface sensors will measure impact acceleration, thermal and electrical properties, and, if the surface is liquid, density and refractive index. This design will enable Cassini to determine the composition; the physical, morphological, and geological nature; and the physical and chemical processes of the atmospheres, surfaces, and magnetosphere of the Saturnian system. This paper briefly describes the Cassini mission and spacecraft and, in somewhat more detail, the scientific instruments.

Jaffe, Leonard D.↗
NASA NTRS2000

Dusty Plasma Experiments Using an Electrodynamic Balance

Knowledge of the formation, distribution, physical, chemical and optical characteristics of interstellar, interplanetary, and planetary dust grains provide valuable information about many issues dealing with the origin and formation of the solar system bodies, interplanetary and interstellar environments as well as various industrial processes. Understanding the microphysics of individual grains and their interaction with the surrounding environment is key to properly model various conditions and interpret existing data. The theory and models of individual dust grains are well developed for environments that vary from dense planetary atmospheres to dusty plasmas to diffuse environments such is interplanetary space. However, experimental investigations of individual dust grains in equilibrium are less common, perhaps due to the difficult of these experiments. Laboratory measurements of dust grains have primarily measured ensemble properties or transient properties of single grains. A technique developed in the 1950's for ion spectroscopy, known as a quadrupole trap or 'Paul Trap', has recently been used to investigate single micron-sized dust grains. This scaled ion trap called an electrodynamic balance has been used for atmospheric aerosol research. A description of this technique is provided. Recent results from experiments to investigate the equilibrium potential of dust grains exposed to far ultraviolet light or to -,in electron or ion beam are presented. This laboratory technique ]ends itself to many applications that relate to planetary atmospheres, heliospheric environments, pre-stellar and pre-planetary conditions, and industrial settings. Several planned experimental approaches are presented. Potential experiments to investigate the interaction of multiple dust grains using an electrodynamic balance are proposed.

Spann, J. F.↗
NASA NTRS2014

Alteration of Lunar Rock Surfaces through Interaction with the Space Environment

Space weathering occurs on all ex-posed surfaces of lunar rocks, as well as on the surfaces of smaller grains in the lunar regolith. Space weather-ing alters these exposed surfaces primarily through the action of solar wind ions and micrometeorite impact processes. On lunar rocks specifically, the alteration products produced by space weathering form surface coatings known as patina. Patinas can have spectral reflectance properties different than the underlying rock. An understanding of patina composition and thickness is therefore important for interpreting re-motely sensed data from airless solar system bodies. The purpose of this study is to try to understand the physical and chemical properties of patina by expanding the number of patinas known and characterized in the lunar rock sample collection.

Frushour, A. M.↗
NASA NTRS1988

Physical processes in comets

When this program began in 1975 only limited photometry had been carried out on comets at any wavelength. Program goals were to observe many comets, including faint periodic comets, at a range of heliocentric distances in order to begin to understand the range of behavior among comets and in a given comet during its approach and departure from the sun. Then a study of the continuum of scattered light from dust was added. More recently the value of joint team observations in visible and infrared light has been recognized and utilized as often as possible. All 1978 to 1982 data was reanalyzed and 1983 to 1986 data analyzed in the framwork of the post-Halley paradigm, covering 25 comets in all. Four observing runs (June, July, Sept., and Jan.) with Hanner produced excellent results on Wilson, Bradfield, P/Klemola, and P/Borrelly and lesser data on other objects, including the last reported IR photometry of P/Halley. The Wilson and Halley data have been reduced.

Newburn, Ray L., Jr.↗
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 NTRS1983

Ice-rich moons and the physical properties of ice

Many of the moons of the outer planets in the solar system consist to a substantial degree of water and other ices. Such ices are thought to make up at least half, by mass, of all condensed material in the outer solar system. The surfaces and interiors of these icy satellites have undergone considerable geologic evolution, and in some cases may still be active today. So that these processes can be understood, certain critical data on the behavior of water and other ices at low (ca. 100 K) temperatures and high (ca. 10 kbar) pressures are needed. Given such data, various techniques for modeling planetary interiors can be tested to see which models best describe the conditions observed on these bodies; such models may then be used to study larger, terrestrial planets.

Consolmagno, G. J.↗
NASA NTRS2012

Inter-Disciplinary Validation of Pre Earthquake Signals. Case Study for Major Earthquakes in Asia (2004-2010) and for 2011 Tohoku Earthquake

We carried out multi-sensors observations in our investigation of phenomena preceding major earthquakes. Our approach is based on a systematic analysis of several physical and environmental parameters, which we found, associated with the earthquake processes: thermal infrared radiation, temperature and concentration of electrons in the ionosphere, radon/ion activities, and air temperature/humidity in the atmosphere. We used satellite and ground observations and interpreted them with the Lithosphere-Atmosphere- Ionosphere Coupling (LAIC) model, one of possible paradigms we study and support. We made two independent continues hind-cast investigations in Taiwan and Japan for total of 102 earthquakes (M>6) occurring from 2004-2011. We analyzed: (1) ionospheric electromagnetic radiation, plasma and energetic electron measurements from DEMETER (2) emitted long-wavelength radiation (OLR) from NOAA/AVHRR and NASA/EOS; (3) radon/ion variations (in situ data); and 4) GPS Total Electron Content (TEC) measurements collected from space and ground based observations. This joint analysis of ground and satellite data has shown that one to six (or more) days prior to the largest earthquakes there were anomalies in all of the analyzed physical observations. For the latest March 11 , 2011 Tohoku earthquake, our analysis shows again the same relationship between several independent observations characterizing the lithosphere /atmosphere coupling. On March 7th we found a rapid increase of emitted infrared radiation observed from satellite data and subsequently an anomaly developed near the epicenter. The GPS/TEC data indicated an increase and variation in electron density reaching a maximum value on March 8. Beginning from this day we confirmed an abnormal TEC variation over the epicenter in the lower ionosphere. These findings revealed the existence of atmospheric and ionospheric phenomena occurring prior to the 2011 Tohoku earthquake, which indicated new evidence of a distinct coupling between the lithosphere and atmosphere/ionosphere.

Ouzounov, D.↗
NASA NTRS1975

Apollo Telescope Mount experiments technology

The Skylab Apollo Telescope Mount (ATM) experiments, consisting of a white light coronagraph, four ultraviolet instruments, two X-ray telescopes and two hydrogen-alpha telescopes, observed the sun daily for nine solar rotations. The results have only begun to be evaluated, but is is already apparent that many theories of solar physics will undergo significant revisions as results are further developed. The ATM instruments were individually larger, more complex, and provided better spatial resolution than previous solar satellite instruments. An additional major advantage of the telescope complex was its ability to simultaneously collect multispectral data for specific experiments. A description of the Skylab, the ATM and the ATM experiments will be given. The daily process of flight planning and execution will be described. Examples of scientific data and some preliminary findings will be presented.

Keathley, W. C.↗
NASA NTRS1979

Non-flammable polyimide materials for aircraft and spacecraft applications

Recent developments in polyimide chemistry show promise for producing materials with very low flammability and a wide range of mechanical properties. Polyimide foams can be synthesized to provide fire safety without detectable formation of smoke or toxic byproducts below 204 C (400 F), thus avoiding an environment which is lethal to human habitation. This work has been and is currently being performed under development programs, the objective of which is to provide cost effective processes for producing thermally stable, polyimide flexible resilient foams, thermal-acoustical insulating materials, rigid low density foam panels, and high strength foam structures. The chemical and physical properties demonstrated by these materials represent a technological advancement in the art of thermally stable polyimide polymers which are expected to insure fire protection of structures and components used in air transportation and space exploration. Data compiled to date on thermal, physical and functional properties of these materials are presented.

Gagliani, J.↗
NASA NTRS1990

CFD validation for aerodynamic flows - Challenge for the '90's

The process of computational fluid dynamics (CFD) validation is described from two perspectives, numerical error validation and physical model validation. Errors associated with time and space discretization, grid refinement, numerical dissipation, and level of solution convergence, are all possible sources of numerical error. The second aspect of CFD code validation is associated with the governing equations and the physical models, e.g., chemistry and turbulence models. This type of validation requires comparisons with carefully conducted experiments and is the primary aspect of the validation process discussed in this paper. Examples of validation are shown for selected Reynolds-averaged Navier-Stokes codes for conditions from transonic through hypersonic. Since code applications are becoming more complex, it no longer suffices to use data from surface or integral quantities alone to provide the required validation. Flow field surveys and experimental boundary condition measurements are emerging as critical data that must be obtained for CFD code validation. Progress in the overall level of validation is shown to be improving. However, future challenges remain, some of which are enumerated.

Marvin, Joseph G.↗