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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Steady and Transient Performance Prediction of Gas Turbine Engines

This Lecture Series covers topics of aero-thermodynamic performance prediction methods for gas turbine engines with respect to steady and transient operation. This includes advanced cycle calculation methods, also taking into account variable cycle engine types. A very important objective is the consideration of installation effect, i.e., Reynolds number and inlet distortions, as well as advanced control concepts for increasing engine surge margins. In addition to these topics, individual papers include practical considerations in developing the engine cycle, dynamic simulation, inlet distortion effects in aircraft propulsion system integration, “smart” engines, performance and heal monitoring models. This Lecture Series, sponsored by the Propulsion and Energetics Panel of AGARD and the Consultant and Exchange Programme of AGARD presented on 27th -28th May 1992 in Cambridge, MA, United States, 9th-10th June 1992 in Neubiberg, Germany and 11th-12th June 1992 in Chàtillon/Bagneux (near Paris), France

Aircraft engines↗
NASA NTRS1992

Sixteenth International Laser Radar Conference, Part 1

This publication contains extended abstracts of papers presented at the 16th International Laser Radar Conference, held in Cambridge, Massachusetts, July 20-24, 1992. One hundred ninety-five papers were presented in both oral and poster sessions. The topics of the conference sessions were: 1. Mt. Pinatubo Volcanic Dust Layers Observations 2. Global Change/Ozone Measurements 3. GLOBE/LAWS/LITE 4. Mesopheric Measurements and Measurement Systems 5. Middle Atmosphere 6. Wid Measurements and Measurement Systems 7. Imaging and Ranging 8. Water Vapor Measurements 9. Systems and Facilities 10. Laser Devices and Technology This conference reflects the breadth of research activities being conducted in the lidar field. These abstracts address subjects from lidar-based atmospheric investigations relating to global change to the development of new lidar systems and technology

Lidar↗
NASA NTRS1992

Sixteenth International Laser Radar Conference, part 2

Given here are extended abstracts of papers presented at the 16th International Laser Radar Conference, held in Cambridge, Massachusetts, July 20-24, 1992. Topics discussed include the Mt. Pinatubo volcanic dust laser observations, global change, ozone measurements, Earth mesospheric measurements, wind measurements, imaging, ranging, water vapor measurements, and laser devices and technology.

Mccormick, M. Patrick↗
NASA NTRS1992

A simple, effective media access protocol system for integrated, high data rate networks

The operation and performance of a dual media access protocol for integrated, gigabit networks are described. Unlike other dual protocols, each protocol supports a different class of traffic. The Carrier Sensed Multiple Access-Ring Network (CSMA/RN) protocol and the Circulating Reservation Packet (CRP) protocol support asynchronous and synchronous traffic, respectively. The two protocols operate with minimal impact upon each other. Performance information demonstrates that they support a complete range of integrated traffic loads, do not require call setup/termination or a special node for synchronous traffic control, and provide effective pre-use and recovery. The CRP also provides guaranteed access and fairness control for the asynchronous system. The paper demonstrates that the CSMA-CRP system fulfills many of the requirements for gigabit LAN-MAN networks most effectively and simply. To accomplish this, CSMA-CRP features are compared against similar ring and bus systems, such as Cambridge Fast Ring, Metaring, Cyclic Reservation Multiple Access, and Distributed Dual Queue Data Bus (DQDB).

Foudriat, E. C.↗
NASA NTRS1993

DADiSP processing guide

A guide for DADiSP software, intended for use by the Lambda Point Experiment (LPE) Team during and after the United States Microgravity Payload (USMP)-1 mission, is presented. DADiSP is a Data Analysis and Display Software developed and marketed by DSP Development Corporation, Cambridge, Massachusetts. This guide is intended to be used in addition to the DADiSP Worksheet User Manual and Reference Manual which are supplied by the company with the software. Technical support for DADiSP is available from DSP at (617) 577-1133. Access to DADiSP on Acceleration Characterization and Analysis Project (ACAP) EGSE is being provided to the LPE team during USMP-1 for off-line processing of SAMS data.

Rogers, Melissa J. B.↗
NASA NTRS1993

Effect of sudden solar wind dynamic pressure changes at subauroral latitudes - Change in magnetic field

The observations obtained during the International Magnetospheric Study (IMS) from the magnetometers of the IGS network extending from Cambridge, England, to Tromso, Norway, are used to study the response of subauroral current systems to sudden changes in solar wind dynamic pressure. Observations show that the response is very strong at subauroral latitudes. The preliminary response in the H component is a brief, small increase in the dayside morning sector and a decrease in the aftenoon and night sectors. The main response in the horizontal field (the H and D components) is toward the pole except in the dayside morning sector. The inferred ionospheric current is mainly a circulatory system flowing counterclockwise when viewed from the north pole everywhere at subauroral latitudes except the dayside morning sector.

Le, G.↗
NASA NTRS1994

Various Roentgen satellite (ROSAT) related studies

The first six months was spent obtaining ROSAT Survey data for as many Slew Survey sources as possible. ROSAT Survey (RASS) counterparts for 605 of the 819 Slew sources (or 75 percent). were found at MPE, providing RASS positions, fluxes, and hardness ratios. The positions were used immediately to confirm or reject proposed catalog identifications from SIMBAD and NED, and to begin a program of identifying new BL Lac objects with high efficiency. In the final six months of the award, extensive analysis were preformed on the RASS counterpart data at Cambridge screening Slew sources with multiple RASS counterparts (up to 23); extended sources and sources with large discrepancies between the RASS and Slew positions. The possibly highly absorbed sources were also studied. Finally, the RASS data has helped to identify optical counterparts to Slew Survey sources - BL Lacs stars, and 'blank fields'.

Stauffer, John R.↗
NASA NTRS1990

Are highly parallel systems ready for prime time?

This is the edited and abbreviated transcript of a panel discussion held on May 9, 1989, in Los Angeles, during the conference "Parallel Computational Fluid Dynamics-Implementations and Results Using MIMD Computers." The purpose of the conference was to discuss recent developments in the use of MIMD parallel computers in high-performance computational fluid dynamics. The intent of the panel discussion was to summarize the findings of the meeting, and to give a perspective on the state of the art in using parallel computers for solving large-scale engineering and scientific application problems. The panelists were Creon Levit (NAS Systems Division, NASA-Ames Research Center, Moffett Field, California), Kent Misegades (Cray Research, Inc., Mendota Heights, Minnesota), Gary Montry (Myrias Computer Corporation, Albuquerque, New Mexico), Ken Neves (Boeing Computer Services, Seattle, Washington), Anthony Patera (Massachusetts Institute of Technology, Cambridge, Massachusetts), and Justin Rattner (Intel Scientific Computers, Beaverton, Oregon).

Simon, Horst D.↗
NASA NTRS1993

Two new hot white dwarfs in a region of exceptionally low hi density

We report the discovery of two hot white dwarfs which have the lowest line-of-sight neutral hydrogen column densities yet measured. The stars were found independently by the ROSAT EUV, Montreal-Cambridge-Tololo, and Edinburgh-Cape surveys. Follow-up observations made using the Voyager 2 ultraviolet spectrometer reveal strong continua shortward of the 912A Lyman limit from which we deduce that the neutral hydrogen column densities are 1.3 x 10(exp 17) and 2.0 x 10(exp 17) atoms/sq cm.

Barstow, M. A.↗
NASA NTRS1996

IPS observations of heliospheric density structures associated with active regions

Interplanetary scintillation (IPS) measurements of the 'disturbance factor' g, obtained with the Cambridge (UK) array can be used to explore the heliospheric density structure. We have used these data to construct synoptic (Carrington) maps, representing the large-scale enhancements of the g-factor in the inner heliosphere. These maps emphasize the stable corotating, rather than the transient heliospheric density enhancements. We have compared these maps with Carrington maps of Fe XIV observations National Solar Observatory ((NSO), Sacramento Peak) and maps based on Yohkoh Soft X-Ray Telescope (SXT) X-ray observations. Our results indicate that the regions of enhanced g tend to map to active regions rather than the current sheet. The implication is that act ve regions are the dominant source of the small-scale (approximately equal 200 km) density variations present in the quiet solar wind.

Hick, P.↗
NASA NTRS1997

The First Multiple Layer Doppler Imaging of an Active Binary

Preliminary results were presented at the Cool Stars, Stellar Systems, and the Sun in Cambridge, MA in July 1997. A copy of the two published papers (in press) is attached. The project has met or exceeded our expectations. The rapid readout data have given us an excellent data set to model in detail the flare behavior. The large number of spectral features observed between the EUVE and HST data have allowed us to compute a mean model atmosphere and compare the results to another well studied system (HR 1099 - Cycle 3 HST observation previously published). I developed a model (anisotropic macroturbulence) that fits the CIV and MgII better than previously achieved. These results have been constrained by the EUVE data. In early studies, 2 gaussians were applied to the profile. The interpretation of these features was unclear. The anisotropic macroturbulence model fits the data better than previously possible and gives a physically reasonable interpretation: there appears to be an asymmetrical distribution between the radial and tangential velocity fields. This is similar to case of the Sun.

Dempsey, Robert C.↗
NASA NTRS1996

Process Model for Friction Stir Welding

Friction stir welding (FSW) is a relatively new process being applied for joining of metal alloys. The process was initially developed by The Welding Institute (TWI) in Cambridge, UK. The FSW process is being investigated at NASA/MSEC as a repair/initial weld procedure for fabrication of the super-light-weight aluminum-lithium shuttle external tank. The FSW investigations at MSFC were conducted on a horizontal mill to produce butt welds of flat plate material. The weldment plates are butted together and fixed to a backing plate on the mill bed. A pin tool is placed into the tool holder of the mill spindle and rotated at approximately 400 rpm. The pin tool is then plunged into the plates such that the center of the probe lies at, one end of the line of contact, between the plates and the shoulder of the pin tool penetrates the top surface of the weldment. The weld is produced by traversing the tool along the line of contact between the plates. A lead angle allows the leading edge of the shoulder to remain above the top surface of the plate. The work presented here is the first attempt at modeling a complex phenomenon. The mechanical aspects of conducting the weld process are easily defined and the process itself is controlled by relatively few input parameters. However, in the region of the weld, plasticizing and forging of the parent material occurs. These are difficult processes to model. The model presented here addresses only variations in the radial dimension outward from the pin tool axis. Examinations of the grain structure of the weld reveal that a considerable amount of material deformation also occurs in the direction parallel to the pin tool axis of rotation, through the material thickness. In addition, measurements of the axial load on the pin tool demonstrate that the forging affect of the pin tool shoulder is an important process phenomenon. Therefore, the model needs to be expanded to account for the deformations through the material thickness and the forging affect of the shoulder. The energy balance at the boundary of the plastic region with the environment required that energy flow away from the boundary in both radial directions. One resolution to this problem may be to introduce a time dependency into the process model, allowing the energy flow to oscillate across this boundary. Finally, experimental measurements are needed to verify the concepts used here and to aid in improving the model.

Adams, Glynn↗
NASA NTRS1998

AXAF: Current Developments and Future Plans for the Scientific Data Analysis

AXAF, the Advanced X-ray Astrophysics Facility, is one of NASA's great observatories scheduled for launch in January of 1999 by a Space Shuttle. This facility will be available to scientists in the United States and to the international astronomical community over an anticipated mission lifetime of at least 5 years. The objective of AXAF is to make astrophysical observations in the 0.09 to 10.0 keV energy range with two imaging detectors, and two sets of transmission gratings giving high spatial (0.5 arcsec) and spectral (E/(Delta)E=100-2000) resolution. The AXAF Science Center (ASC) in Cambridge, MA, USA is responsible for obtaining and reviewing observation proposals submitted by users, providing long range science planning and performing all science data calibration, data analysis, science instrument trend analysis, and science data archiving. The ASC will distribute science data products to the users. We will review here the current developments and future plans for the AXAF scientific data analysis system, its infrastructure and new key features, including the global modelling and fitting environment, integrated data analysis GUIs and new analysis tools.

Fruscione, Antonella↗
NASA NTRS1999

Nondestructive Evaluation of the Friction Weld Process on 2195/2219 Grade Aluminum

In 1996, NASA's Marshall Space Flight Center began an ambitious program designed to find alternative methods of repairing conventional TIG (Tungsten Inert Gas) welds and VPPA (Variable Polarity Plasma Arc) welds on the Space Shuttle External Tank without producing additional heat-related anomalies or conditions. Therefore, a relatively new method, invented by The Welding Institute (TWI) in Cambridge, England, called Friction Stir Welding (FSW), was investigated for use in this application, as well as being used potentially as an initial weld process. As with the conventional repair welding processes, nondestructive evaluation (NDE) plays a crucial role in the verification of these repairs. Since it was feared that conventional NDE might have trouble with this type of weld structure (due to shape of nugget, grain structure, etc.) it was imperative that a complete study be performed to address the adequacy of the NDE process. This paper summarizes that process.

Suits, Michael W.↗
NASA NTRS1999

Mission Planning for the CHANDRA X-Ray Observatory

The CHANDRA x-ray observatory started life as the Advanced X-ray Facility (AXAF) but was renamed Chandra in December of 1998 at the of a nationwide contest by NASA to name the new observatory. The honors the Nobel Prize winning astrophysicist S. Chandrasekar who astrophysics at the University of Chicago for more than 50 years, following graduate studies at Cambridge University in England. The observatory has been under construction for a decade under the management of the Observatory observatory, Projects office at the Marshall Space Flight Center; the same office that oversaw the construction of the Hubble Space Telescope and the Compton Gamma Ray Observatory. This observatory is a member of NASA's great observatory series of missions of which Hubble and Compton are members. This paper describes the mission planning that was conducted at MSFC to design the orbit and launch window that would permit the new observatory to function properly.

Mullins, Larry D.↗
NASA NTRS1999

A New Scientific use of Total Eclipses of the Moon: Studies of the Generation and Loss of Atmospheres of Primitives Bodies

This grant supported observational campaigns to record the size and brightness of the lunar atmosphere as seen in sodium gas (Na) emissions during the totality phase of lunar eclipses. Three eclipse events were attempted, two from the Mc Donald Observatory in Fort Davis Texas, and one from the site of Italy's Galileo National Telescope (GNT) in La Palma, in the Canary Islands. In all three cases, clear skies prevailed and excellent datasets were obtained. Following the observational component of the grant, a period of detailed processing and analysis began. Eclipse events were chosen for study because when the moon is in full phase it has been within the terrestrial magnetosphere for a few days, thereby shielded from solar wind impact upon its surface. Since sputtering of Na from the lunar regolith by solar wind particles had been proposed as a source of the Moon's atmosphere, this was a test of the mechanism. If the lunar Na appeared to be diminished in comparison to abundances seen at other phases (e.g., at quarter phase when the moon is directly in the solar wind), the solar wind sputtering would indeed be a major source of lunar Na. These experiments could not be conducted during any full moon night because scattering of bright moonlight is so strong that low-light-level imaging of the lunar atmosphere could not be achieved. Hence, the use of eclipses. The final result of these experiments was, for once, clear and unambiguous. The robust size and Na brightness levels measured during all of the eclipses showed that solar wind sputtering could not be a major source of the lunar atmosphere. A major paper on this conclusion was published in ICARUS, and an oral presentation of partial results given at the The Three Galileos conference in Padova (Italy) in January 1997 and at the DPS meeting in Cambridge, MA, in July 1997.

Mendillo, Michael↗
NASA NTRS1998

BioSIGHT: Interactive Visualization Modules for Science Education

Redefining science education to harness emerging integrated media technologies with innovative pedagogical goals represents a unique challenge. The Integrated Media Systems Center (IMSC) is the only engineering research center in the area of multimedia and creative technologies sponsored by the National Science Foundation. The research program at IMSC is focused on developing advanced technologies that address human-computer interfaces, database management, and high- speed network capabilities. The BioSIGHT project at IMSC is a demonstration technology project in the area of education that seeks to address how such emerging multimedia technologies can make an impact on science education. The scope of this project will help solidify NASA's commitment for the development of innovative educational resources that promotes science literacy for our students and the general population as well. These issues must be addressed as NASA marches towards the goal of enabling human space exploration that requires an understanding of life sciences in space. The IMSC BioSIGHT lab was established with the purpose of developing a novel methodology that will map a high school biology curriculum into a series of interactive visualization modules that can be easily incorporated into a space biology curriculum. Fundamental concepts in general biology must be mastered in order to allow a better understanding and application for space biology. Interactive visualization is a powerful component that can capture the students' imagination, facilitate their assimilation of complex ideas, and help them develop integrated views of biology. These modules will augment the role of the teacher and will establish the value of student-centered interactivity, both in an individual setting as well as in a collaborative learning environment. Students will be able to interact with the content material, explore new challenges, and perform virtual laboratory simulations. The BioSIGHT effort is truly cross-disciplinary in nature and requires expertise from many areas including Biology, Computer Science, Electrical Engineering, Education, and the Cognitive Sciences. The BioSIGHT team includes a scientific illustrator, educational software designer, computer programmers as well as IMSC graduate and undergraduate students. Our collaborators include TERC, a research and education organization with extensive k-12 math and science curricula development from Cambridge, MA.; SRI International of Menlo Park, CA.; teachers and students from local area high schools (Newbury Park High School, USC's Family of Five schools, Chadwick School, and Pasadena Polytechnic High School).

Wong, Wee Ling↗
NASA NTRS1999

Molecular Modeling and Experimental Investigations of Nonlinear Optical Compounds Monosubstituted Derivatives of Dicyanovinylbenzene

A search for potential nonlinear optical compounds was performed using the Cambridge Structure Database and molecular modeling. We investigated a series of monosubstituted derivatives of dicyanovinylbenzene, since the nonlinear optical (NLO) properties of such derivatives (o-methoxy-dicyanovinylbenzene, DIVA) were studied earlier. The molecular geometry of these compounds was investigated with x-ray analysis and discussed along with the results of molecular mechanics and ab initio quantum chemical calculations. The influence of crystal packing on the planarity of the molecules of this series has been revealed. Two new compounds from the series studied, ortho-F and para-Cl-dicyanovinylbenzene, according to powder measurements, were found to be NLO compounds in the crystal state about 10 times more active than urea. The peculiarities of crystal structure formation in the framework of balance between van der Waals and electrostatic interactions have been discussed. The crystal shape of DIVA and two new NLO compounds have been calculated on the basis of the known crystal structure.

Timofeeva, Tatiana V.↗