Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “conclusions”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Gamma-Ray Observations of the Interstellar Clouds in Cepheus

During the last six months of the period of performance, the diffuse gamma-ray emission from the Monoceros region was reanalyzed and one of the important conclusions was revised as a result. The reanalysis incorporated newly-available data from recent EGRET viewing periods and revealed a previously-uncataloged gamma-ray point source near the plane in Monoceros. The effect of incorporating this source in the diffuse emission model was significant, as its flux was comparable to that from a large interstellar cloud complex in the Perseus arm. In the updated model, a greatly reduced gamma-ray emissivity was found in the Perseus arm. This finding alters the previous conclusion that we had found evidence for an enhanced emissivity in the arm, which had supported the hypothesis that cosmic rays are coupled to the interstellar medium on the scale of spiral arms. Our updated findings are consistent with our previous results for the emissivity toward the Cepheus region (Digel et al. 1996), where a monotonic gradient of emissivity in the outer Galaxy was found. The updated analysis of Monoceros was presented at the June, 1998 meeting of the American Astronomical Society, and a journal publication should be ready for submission soon.

Digel, S.↗
NASA NTRS1999

Step Bunching: Influence of Impurities and Solution Flow

Step bunching results in striations even at relatively early stages of its development and in inclusions of mother liquor at the later stages. Therefore, eliminating step bunching is crucial for high crystal perfection. At least 5 major effects causing and influencing step bunching are known: (1) Basic morphological instability of stepped interfaces. It is caused by concentration gradient in the solution normal to the face and by the redistribution of solute tangentially to the interface which redistribution enhances occasional perturbations in step density due to various types of noise; (2) Aggravation of the above basic instability by solution flowing tangentially to the face in the same directions as the steps or stabilization of equidistant step train if these flows are antiparallel; (3) Enhanced bunching at supersaturation where step velocity v increases with relative supersaturation s much faster than linear. This v(s) dependence is believed to be associated with impurities. The impurities of which adsorption time is comparable with the time needed to deposit one lattice layer may also be responsible for bunching; (4) Very intensive solution flow stabilizes growing interface even at parallel solution and step flows; (5) Macrosteps were observed to nucleate at crystal corners and edges. Numerical simulation, assuming step-step interactions via surface diffusion also show that step bunching may be induced by random step nucleation at the facet edge and by discontinuity in the step density (a ridge) somewhere in the middle of a face. The corresponding bunching patterns produce the ones observed in experiment. The nature of step bunching generated at the corners and edges and by dislocation step sources, as well as the also relative importance and interrelations between mechanisms 1-5 is not clear, both from experimental and theoretical standpoints. Furthermore, several laws controlling the evolution of existing step bunches have been suggested, though unambiguous conclusions are still missing. Addressing these issues is the major goal of the present project. The theory addressing the above problem, experimental methods, several figures which include: (1) the spatial wave numbers at which the system is neutrally stable as a function of growth velocity for linear kinetics and supersaturation for nonlinear kinetics; (2) a schematic of the experiment of lysozyme crystal growing under conditions of natural convection; (3) fluctuations in time, t, of the normal growth rate, R(t), vicinal slope, p(t) and Fourier Spectra of R(t), discussions and conclusions are presented.

Chernov, A. A.↗
NASA NTRS1998

Far-Infrared Heterodyne Spectrometer for SOFIA

This report summarizes work done under NASA Grant NAG2-1062 awarded to the University of Colorado. The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant (USRA 8500-98-010) to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

Betz, A. L.↗
NASA NTRS1999

Does Velocity Redistribution Really Enhance the HE 304 A Line to Observed Intensities?

Previous work by this group has demonstrated that small-scale nonthermal velocities probably play a significant role in enhancing the intensity of the He II 304 A line above values predicted by the static atmosphere NLTE theories, and more in conformity with Skylab and SOHO observations. This presentation briefly summarizes the evidence for this conclusion, emphasizing SOHO and correlated groundbased observations, of which examples are presented. However, in contrast to the previous studies, the tact taken here is more critical, asking the question "Can velocity redistribution fully explain the observations of the 304 A line, and what counter-indications and problems remain?" The conclusion reached is that, while velocity redistribution plays a significant role in the intensity enhancement, it may not be the whole story. Some other mechanism, associated with velocity filtration, may be at work.

Jordan, Stuart↗
NASA NTRS1998

Far-Infrared Heterodyne Spectrometer for Sofia

The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

Betz, A. L.↗
NASA NTRS1999

Strategies and Technologies for In Situ Mineralogical Investigations on Mars

Surface landers on Mars (Viking and Pathfinder) have not revealed satisfying answers to the mineralogy and lithology of the planet's surface. In part, this results from their prime directives: Viking focused on exobiology, Pathfinder focused on technology demonstration. The analytical instruments on board the landers made admirable attempts to extract the mineralogy and geology of Mars, as did countless modeling efforts after the missions. Here we suggest a framework for elucidating martian, or any other planetary geology, through an approach that defines (a) type of information required, (b) explorational strategy harmonious with acquisition of these data, (c) interpretation approach to the data, (d) compatible mission architecture, (e) instrumentation for interrogating rocks and soil. (a) Data required: The composition of a planet is ordered at scales ranging from molecules to minerals to rocks, and from geological units to provinces to planetary-scale systems. The largest ordering that in situ compositional instruments can attempt to interrogate is rock type "aggregate" information. This is what the geologist attempts to identify first. From this, mineralogy can be either directly seen or inferred. From mineralogy can be determined elemental abundances and perhaps the state of the compounds as being crystalline or amorphous. Knowledge of rock type and mineralogy is critical for elucidating geologic process. Mars landers acquired extremely valuable elemental data, but attempted to move from elements to aggregates, but this can only be done by making many assumptions and sometimes giant leaps of faith. Data we believe essential are elements, minerals, degree of ordering of compounds, and the aggregate or rock type that these materials compose. (b) Explorational strategy: A lander should function as a surrogate geologist. Of the total landscape, a geologist sees much, but gives detailed attention to an infinitesimally small amount of what is seen. To acquire samples worth detailed scrutiny, as many samples as possible need examining at a cursory or reconnaissance level. A representative, statistically-meaningful sample number cannot be overemphasized. This maxim still applies to geological exploration of our own planet of which we have abundant knowledge. Analysis of many samples mandates low-power consumption per sample. (c) Data interpretation: No single instrument can analyze the full spectrum of the x-axis. An instrument is optimized for detecting certain material characteristics and must therefore affix itself to some point on the x-axis. Any conclusions drawn about data to the left or right of the instrument's position on this axis must necessarily be derived by inference. Hence, it seems logical to include on a mission, instruments that are not closely spaced in their x-axis-position, and if only two analytical methods are used, as shown, they should start at opposite ends of the axis and work towards the center. As examples, we depict a high-resolution camera to evaluate rock type ("aggregate" state) and mineralogy, and an x-ray diffractometer-fluorescence spectrometer (XRD-XRF) to determine elements, minerals, and the degree of order of materials. (d) Mission architecture: No instrument or suite of instruments can be relied upon to always give truly unequivocal analyses. The suite of instruments should therefore permit conclusions of one instrument to be checked against those of another through closed analytical loops. These "loops" can be structured by a combination of orbital imagery, descent imagery, broad-band site viewing/analysis, and data that cover both x and y axes. For example, the detection of a basaltic-looking rock with a microscope should be checked against the elements detected, the appearance of the rock as a lava flow from descent imagery, and so forth. (e) Instrumentation: To satisfy the above criteria, it is necessary to: (i) See the rock or soil with high resolution + magnification, (ii) Examine many samples, (iii) Consume little power per analysis, (iv) Determine elemental species, (v) Determine mineralogy directly (not inferentially) and the degree of ordering of compounds, (vi) Start analyzing from both ends of the x-axis. Every geologist wants to see the hand sample first, and apply a hand lens to its surface. This has not been the starting point for missions to Mars. Thus, our technology satisfies all these criteria . This XRD-XRF-Optical instrument currently being developed, analyses rock or soil surfaces without the need for sample acquisition or preparation; this satisfies the power criterion, and enables many analyses. The device acquires direct mineralogy and determines elemental species. The embedded endoscopic camera satisfies the critical criterion of close inspection of samples; the fiber optic cable can also be used for IR, LTV, or laser sample analysis. Additional information is contained in the original (Figures).

Marshall, J. R.↗
NASA NTRS1997

New Potential Sources for Black Onaping Carbon

One intriguing and important issue of the Sudbury Structure concerns the source of the relatively large amount of C in the Onaping Formation Black member. This dilemma was recently addressed, and the conclusion was reached that an impactor could not have delivered all of the requisite C. Becker et al. have suggested that much of the C came from the impactor and reported the presence of interstellar He "caged" inside some fullerenes that may have survived the impact. So, conceivably, the C inventory in the Sudbury Structure comes from both target and impactor materials, although the known target rocks have little C. We discuss here the possibility of two terrestrial sources for at least some of the C: (1) impact evaporation/dissociation of C from carbonate target rocks and (2) the presence of heretofore-unrecognized C-rich (up to 26 wt%) siliceous "shale," fragments, which are found in the upper, reworked Black member. Experimental: Hypervelocity impact of a 0.635-diameter Al projectile into dolomite at 5.03 km/s (performed at the Ames Research Center vertical gun range) produced a thin, black layer (= 0.05 mm thick) that partially lined the crater and coated impactor remnants. Scanning electronic microscope (SEM) imagery shows this layer to be spongelike on a submicron scale and Auger spectroscopic analyses yield: 33% C, 22% Mg, 19% 0, and 9% Al (from the projectile). Elemental mapping shows that all of the available 0 is combined with Ca and Mg, Al is not oxidized, and C is in elemental form. Dissociation efficiency of C from CO2 is estimated to be <10% of crater volume. Raman spectroscopy indicates that the C is highly disorganized graphite. Another impact experiment [4] also produced highly disordered graphite from a limestone target (reducing collector), in addition to small amounts of diamond/lonsdaleite/chaoite (oxidizing collector). These experiments confirm the reduction of C from carbonates in impact vapor plumes. Observational: SEM observations and microprobe analyses of small, black shalelike inclusions in the upper Black Onaping indicate high C contents (7-26 wt% avg. = 16%). They contain mostly quartz and carbonaceous matter with small amounts of altered K-feldspar, clays, Fe oxide, and a sulfide. No evidence of shock is seen in quartz, and overall characteristics indicate a natural, lightly metamorphosed carbonaceous shale or mudstone that probably existed as a preimpact rock in the target region and distal fragments washed in during early crater filling. Fragments range in size from tens of microns to cm and increase in abundance in the upper Black toward the Onwatin contact, although their distribution is highly irregular. This increase corresponds to an increase in "organic" C with increasingly negative delta-13 C values and S, together with a decrease in fullerene abundance. In addition, we have found soot in acid-demineralized residues of the Onwatin but not in the Onaping samples. These data could be consistent with impact plume and atmospheric chemical processes, with possible diageneric ovedays. We are analyzing carbonaceous fractions of the Onaping and Onwatin to determine diagnostic C isotopic signatures Analyses by Whitehead et al. on bulk samples revealed no definitive source or processes, although delta-13 C values for "organic" C overlapped those for some meteorites. Discussion: If impact evaporation of Sudbury target carbonates did occur, then where are the carbonates? Distal carbonate (limestone/dolostone) exposures of the Espanola Formation (Huronian Supergroup) are generally thin-bedded, although remnants that partially encompass the Sudbury Crater are variable in thickness and may locally reach 250 m . If a carbonate thickness of 100-200 in existed at the target site, then copious amounts of C could have been reduced by impact processing of carbonates and also C-shale, depending on the efficiency of the processing and the amount of postimpact oxidation. Conclusion: The Sudbury crater offers a unique opportunity to study preserved characteristics of immediate carbonaceous fallback matter and particles of short-term residency in the impact plume as well as dust/aerosols from postimpact atmospheric processing.

Bunch, T. E.↗
NASA NTRS2000

On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Experimental Study - Part 1

An extensive study to improve flow uniformity and periodicity in the NASA Transonic Flutter Cascade is presented here. The results are reported in two independent parts dealing with the experimental approach and the analytical approach. The first part, the Experimental Study, focuses first on the data sets acquired in this facility in the past and explains several discrepancies, particularly the questions of actual flow incidence and cascade back pressure levels. Next, available means for control and modifications of the cascade flowfield, boundary layer bleed and tailboard settings are presented in detail. This is followed by experimental data sets acquired in modified test facility configurations that were based on analytical predictions of the cascade flowfield. Finally, several important conclusions about improving the cascade flowfield uniformity and blade load periodicity are summarized. The important conclusions are: (1) boundary layer bleed does not improve the cascade flow periodicity; (2) tunnel wall contours must be carefully matched to the expected shape of cascade streamlines; (3) actual flow incidence for each cascade configuration rather must be measured instead of relying on the tunnel geometry; and (4) the current cascade configuration exhibits a very high blade load uniformity over six blades from blade #2 to blade #7, and the facility is now ready for unsteady pressure data acquisition.

Lepicovsky, J.↗
NASA NTRS2000

Iron Meteorites from Antarctica: More Specimens, Still 40% Ungrouped

Clarke (1986) was the first to recognize that ungrouped irons are more common in Antarctica than in the regions where most irons have been collected; his conclusion was based on the first 21 irons collected in Antarctica. Wasson et al. (1989) reported compositional data for 24 Antarctic irons and reported that 8 were ungrouped; the ungrouped fraction of 0.33 was found to be about twice that (0.153) observed in irons from the remainder of the world. Wasson (1990) reported data for 7 additional Antarctic irons, and reported that 12 of 31 were ungrouped, a fraction of 0.39. In Table 1 I summarize the data obtained to date on independent Antarctic iron meteorites by our UCLA neutron-activation laboratory. With about 5 exceptions, the listed values are the means of duplicate determinations. We have now analyzed 40 independent iron meteorites; in Table 2 I list 8 other irons that proved to be paired with meteorites listed in Table 1. Because of the close relationship between pallasites and iron meteorites, in Table 3 I also list our data for two Antarctic pallasites that were studied at UCLA. Our new results confirm the previously reached conclusion about the abundance of ungrouped irons. In fact, the ungrouped fraction has increased slightly; of the 40 irons 16 are ungrouped, a fraction of 0.40. The two meteorites with pallasite structures are both small (approx. equals 50 g); one is ungrouped, the other a high-Ir anomalous member of the main-group pallasites (PMG).

Wasson, J. T.↗
NASA NTRS2000

Airborne Laser Altimetry Mapping of the Greenland Ice Sheet: Application to Mass Balance Assessment

In 1998 and '99, the Arctic Ice Mapping (AIM) program completed resurveys of lines occupied 5 years earlier revealing elevation changes of the Greenland ice sheet and identifying areas of significant thinning, thickening and balance. In planning these surveys, consideration had to be given to the spatial constraints associated with aircraft operation, the spatial nature of ice sheet behavior, and limited resources, as well as temporal issues, such as seasonal and interannual variability in the context of measurement accuracy. This paper examines the extent to which the sampling and survey strategy is valid for drawing conclusions on the current state of balance of the Greenland ice sheet. The surveys covered the entire ice sheet with an average distance of 21.4 km between each location on the ice sheet and the nearest flight line. For most of the ice sheet, the elevation changes show relatively little spatial variability, and their magnitudes are significantly smaller than the observed elevation change signal. As a result, we conclude that the density of the sampling and the accuracy of the measurements are sufficient to draw meaningful conclusions on the state of balance of the entire ice sheet over the five-year survey period. Outlet glaciers, however, show far more spatial and temporal variability, and each of the major ones is likely to require individual surveys in order to determine its balance.

Abdalati, W.↗
NASA NTRS2001

Flight Test Analysis of the Forces and Moments Imparted on a B737-100 Airplane During Wake Vortex Encounters

Aircraft travel has become a major form of transportation. Several of our major airports are operating near their capacity limit, increasing congestion and delays for travelers. As a result, the National Aeronautics and Space Administration (NASA) has been working in conjunction with the Federal Aviation Administration (FAA), airline operators, and the airline industry to increase airport capacity without sacrificing public safety. One solution to the problem is to increase the number of airports and build new. runways; yet, this solution is becoming increasingly difficult due to limited space. A better solution is to increase the production per runway. This solution increases the possibility that one aircraft will encounter the trailing wake of another aircraft. Hazardous wake vortex encounters occur when an aircraft encounters the wake produced by a heavier aircraft. This heavy-load aircraft produces high-intensity wake turbulence that redistributes the aerodynamic loads of trailing smaller aircraft. This situation is particularly hazardous for smaller aircraft during takeoffs and landings. In order to gain a better understanding of the wake-vortex/aircraft encounter phenomena, NASA Langley Research Center conducted a series of flight tests from 1995 through 1997. These tests were designed to gather data for the development a wake encounter and wake-measurement data set with the accompanying atmospheric state information. This data set is being compiled into a database that can be used by wake vortex researchers to compare with experimental and computational results. The purpose of this research is to derive and implement a procedure for calculating the wake-vortex/aircraft interaction portion of that database by using the data recorded during those flight tests. There were three objectives to this research. Initially, the wake-induced forces and moments from each flight were analyzed based on varying flap deflection angles. The flap setting alternated between 15 and 30 degrees while the separation distance remained constant. This examination was performed to determine if increases in flap deflection would increase or decrease the effects of the wake-induced forces and moments. Next, the wake-induced forces and moments from each flight were analyzed based on separation distances of 1-3 nautical miles. In this comparison, flap deflection was held constant at 30 degrees. The purpose of this study was to determine if increased separation distances reduced the effects of the wake vortex on the aircraft. The last objective compared the wake-induced forces and moments of each flight as it executed a series of maneuvers through the wake-vortex. This analysis was conducted to examine the impact of the wake on the B737 as it traversed the wake horizontally and vertically. Results from the first analysis indicated that there was no difference in wake effect at flap deflections of 15 and 30 degrees. This conclusion is evidenced in the cases of the wake-induced sideforce, rolling moment, and yawing moment. The wake-induced lift, drag, and pitching moment cases yielded less conclusive results. The second analysis compared the wake-induced forces and moments at separation distances of 1-3 nautical miles. Results indicated that there was no significant difference in the wake-induced lift, drag, sideforce, or yawing moment coefficients. The analysis compared the wake-induced forces and moments based on different flight maneuvers. It was found that the wake-induced forces and moments had the greatest impact on out-to-in and in-to-out maneuvers.

Roberts, Chistopher L.↗
NASA NTRS1999

Iron Meteorites from Antarctica: More Specimens, Still 40% Ungrouped

Clarke was the first to recognize that ungrouped irons are more common in Antarctica than in the regions where most irons have been collected; his conclusion was based on the first 21 irons collected in Antarctica. Wasson et al. reported compositional data for 24 Antarctic irons and reported that eight were ungrouped; the ungrouped fraction of 0.33 was found to be about twice that (0.153) observed in irons from the remainder of the world. Wasson reported data for seven additional Antarctic irons, and reported that 12 of 31 were ungrouped, a fraction of 0.39. I summarize the data obtained to date on independent Antarctic iron meteorites by our UCLA neutron-activation laboratory. With about five exceptions, the listed values are the means of duplicate determinations. We have now analyzed 40 independent iron meteorites; I list eight other irons that proved to be paired with meteorites listed. Because of the close relationship between pallasites and iron meteorites, I also list our data for two Antarctic pallasites that were studied at UCLA. Our new results confirm the previously reached conclusion about the abundance of ungrouped irons. In fact, the ungrouped fraction has increased slightly; of the 40 irons 16 are ungrouped, a fraction of 0.40. The two meteorites with pallasite structures are both small (= 50 g); one is ungrouped, the other a high-Ir anomalous member of the main-group pallasites (PMG).

Wasson, J. T.↗
NASA NTRS2000

General Aviation in Nebraska: Nebraska SATS Project Background Paper No. 1

The Nebraska SATS project is a state-level component of NASA's Small Aircraft Transportation System (SATS). During the next several years the project will examine several different factors affecting SATS implementation in Nebraska. These include economic and taxation issues, public policy issues, airport planning processes, information dissemination strategies, and systemic change factors. This background paper profiles the general aviation system in Nebraska. It is written to provide information about the "context" within which SATS will be pursued. The primary focus is thus on describing and providing background information about the current situation. A secondary focus is on drawing general conclusions about the ability of the current system to incorporate the types of changes implied by SATS. First, some brief information on the U.S. aviation system is provided. The next two sections profile the current general aviation aircraft and pilot base. Nebraska's system of general aviation airports is then described. Within this section of the paper, information is provided on the different types of general aviation airports in Nebraska, airport activity levels and current infrastructure. The fourth major section of the background paper looks at Nebraska's local airport authorities. These special purpose local governments oversee the majority of the general aviation airports in the state. Among the items examined are total expenditures, capital expenditures and planning activities. Next, the paper provides background information on the Nebraska Department of Aeronautics (NDA) and recent Federal funding for general aviation in Nebraska. The final section presents summary conclusions.

Smith, Russell↗
NASA NTRS2001

Response to Comment on "Does the Earth Have an Adaptive Infrared IRIS?"

Harrison's (2001) Comment on the Methodology in Lindzen et al (2001) has prompted re-examination of several aspects of study. Probably the most significant disagreement in our conclusions is due to our different approaches to minimizing the influence of long-time-scale variations in the variables A and T on the results. Given the strength of the annual cycle and the 20-month period covered by the data, we believe that removing monthly means is a better approach to minimizing the long-time-scale behavior of the data than removal of the linear trend, which might actually add spurious long- time- scale variability into the modified data. We have also indicated how our statistical methods of establishing statistical significance differ. More definitive conclusions may only possible after more data have been analyzed, but we feel that our results are robust enough to encourage further study of this phenomenon.

Bell, Thomas L.↗
NASA NTRS2002

Electro-Optic Modulator Based on Organic Planar Waveguide Integrated with Prism Coupler

The objectives of the project, as they were formulated in the proposal, are the following: (1) Design and development of novel electro-optic modulator using single crystalline film of highly efficient electro-optic organic material integrated with prism coupler; (2) Experimental characterization of the figures-of-merit of the modulator. It is expected to perform with an extinction ratio of 10 dB at a driving signal of 5 V; (3) Conclusions on feasibility of the modulator as an element of data communication systems of future generations. The accomplishments of the project are the following: (1) The design of the electro-optic modulator based on a single crystalline film of organic material NPP has been explored; (2) The evaluation of the figures-of-merit of the electro-optic modulator has been performed; (3) Based on the results of characterization of the figures-of-merit, the conclusion was made that the modulator based on a thin film of NPP is feasible and has a great potential of being used in optic communication with a modulation bandwidth of up to 100 GHz and a driving voltage of the order of 3 to 5 V.

Sarkisov, Sergey S.↗
NASA NTRS2002

Origin, Structure, and Evolution of Grooved Terrain on Ganymede and Comparison to Europa

'Ridge and trough terrain' (RTT) is a generic term for sets of subparallel ridges and troughs observed on several icy outer planet satellites. Ganymede's grooved terrain is the best studied example of ridge and trough terrain. However, the >500 a resolution of Voyager images limited the conclusions that could be drawn regarding its detailed morphology and deformational style, as well as the relationship of bright grooved terrain to dark terrain on Ganymede. The goal of this study was to utilize Galileo high resolution images to examine and categorize the detailed local-scale morphology of ridge and trough terrains on Ganymede, in order to determine the morphological variety and deformational styles of the terrain, and its evolutionary sequence. This included comparison of the ridges and troughs that occur within dark terrain to those within bright terrain. This study addressed implications for the satellite's local-scale stress history, its lithospheric character, and its broader-scale geological history. Conclusions from the Ganymede were applied to gain insight into the origin of ridge and trough terrains on Europa. Attached are the abstracts of the seven papers and list of one popular press article and 13 abstracts which resulted from this study. No subject inventions are associated with this work.

Pappalardo, Robert T.↗
NASA NTRS2002

Enhancing Science Teacher Training Using Water Resources and GLOBE

Heritage College, located on the Yakama Indian Reservation in south central Washington state, serves a multicultural, underserved, rural population and trains teachers to staff the disadvantaged school districts on and surrounding the reservation. In-service teachers and pre-service teachers in the area show strength in biology but have weak backgrounds in chemistry and mathematics. We are addressing this problem by providing a 2-year core of courses for 3 groups of 25 students (15 pre-service and 10 in-service teachers) using GLOBE to teach integrated physical science and mathematics. At the conclusion of the program, the students will qualify for science certification by Washington State. Water resources are the focal point of the curriculum because it is central to life in our desert area. The lack or excess of water, its uses, quality and distribution is being studied by using GIS, remote sensing and historical records. Students are learning the methodology to incorporate scientific protocols and data into all aspects of their future teaching curriculum. In addition, in each of the three years of the project, pre-service teachers attended a seminar series during the fall semester with presentations by collaborators from industry, agriculture, education and government agencies. Students used NASA educational materials in the presentations that they gave at the conclusion of the seminar series. All pre- and in-service teachers continue to have support via a local web site for Heritage College GLOBE participants.

Falco, James W.↗
NASA NTRS1998

The Generation of Lighting in the Solar Nebula

The process that melted and formed the chondrules, mm-sized glassy beads within meteorites, has not been conclusively identified. Origin by lightning in the solar nebula is consistent with many features of chondrules, but no viable model of lightning has yet been advanced. We present a model demonstrating how lightning could be generated in the solar nebula which differs from previous models in three important aspects. First, we identify a new', powerful charging mechanism that is based on the differences in contact potentials between particles of different composition, a form of triboelectric charging. In the presence of fine silicate grains and fine iron metal grains, large silicate particles (the chondrules) can acquire charges of +10(exp 5) e. Second, we assume that the chondrule precursor particles are selectively concentrated in clumps 1 - 100 km in size by the turbulent concentration mechanism described by Cuzzi et al. (1996). The concentration of these highly charged particles into clumps, in a background of negatively charged metal grains, is what generates the strong electric fields. Third, we make refinements in the estimates of the breakdown electric field and the ionization rate. We calculate that electric fields large enough to trigger breakdown easily could have existed over regions large enough (approx. 100km) to generate very large discharges of electrical energy (approx. 10(exp 16)erg). The discharges would have been sufficiently energetic and frequent to have formed the chondrules. We place constraints on the generation of lightning and conclude that it could not be generated if the abundance of Al-26 in chondrules was as high as the level in the CAls. This conclusion is consistent with isotopic analyses of chondrules. This possibly implies that Al-26 was non-uniformly distributed in the solar nebula or that the chondrules formed several Myr after the CAIs.

Cuzzi, Jeffrey↗