Induced-drag characteristics of crescent-moon-shaped wings
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Van Dam, C. P.↗
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Efficiency characteristics of crescent-shaped wings and caudal fins
Caudal (tail) fins of fish and aquatic mammals that cruise long distances, and wings of certain birds, often have the shape of a crescent moon. This study investigates how the crescent shape contributes to the traveling performance of these animals. A steady-flow theory (Maskew, 1982) that correctly models the trailing wake was used to analyze lifting surface efficiency, which is dependent on the level of induced (or vortex) drag for a given lift and span of the lifting surface. This analysis shows that backward curvature of a wing improves induced efficiency to a value greater than that of the flat untwisted wing of elliptical shape considered optimal in classical wing theory (Prandt, 1921 and Munk, 1921). This increase of induced efficiency results from the nonplanar trailing vortex sheet produced by the crescent-shaped wing at a given angle of attack.
Van Dam, C. P.↗
Length of the lunar crescent
Observations of the crescent moon are studied to determine why the illuminated portion does not extend to a 180-deg arc. The observations are discussed in terms of optical aids, seeing effects, and cusp brightness to examine possible explanations. Hapke's (1984) model is employed to measure lunar surface brightnesses for the present observations and those of Danjon (1932, 1936). The crescent tends to get narrower and dimmer as the moon gets closer to the sun; a model is proposed in which the visible arc length varies as a function of a particular sun-moon angle. Scatter is also predicted for the model which depends on the varying observer sensitivity and other effects. The predictions of the model are found to match all the observational data effectively. An important conclusion is that the crescent moon will be invisible when the moon is within 7 degrees of the sun.
Schaefer, Bradley E.↗
Spray formation mechanism of diverging-tapered-hole GDI injector and its potentials for GDI engine applications
The gasoline-direct-injection market recently, which has shown the improved spray atomization and lower engine particulate emissions compared to conventional straight-hole nozzles. However, the near-nozzle spray formation mechanism associated with this atomization potential of the diverging-he potentials of the diverging-tapered-hole nozzle for GDI engine applications. The analyses focus on the in- and near-nozzle flow structure, and flow dynamics and stability outside the nozzle. We find that the results showed that the diverging-tapered-hole nozzle coupled with proper hole length generated the radially expanding crescent-moon-like flow structure in the hole that promoted the spray atomization and dispersion outside the nozzle. The expansion of the hole cross-sectional area in the diverging-tapered-hole nozzle was appeared to attenuate the mutual interactions of fuel flows in the hole from various origins that formed rather stable sprays. These flow characteristics are discussed to be promising for the compact and robust spray generation for GDI engine applications.
42 ENGINEERING↗
Results of the July moonwatch
Results are presented from a study to determine the visibility of the crescent moon on July 14, 1988. About 2,000 observations from the U.S. and Canada are used to produce a visibility map. The factors affecting visibility are analyzed, including clouds, haze, and humidity.
Doggett, Leroy↗
STS-105 Mission Highlights Resource Tape: Flight Days 4-6
A continuation of 'STS-105 Mission Highlights Resource Tape: Flight Days 1-3' (internal ID 2002046550), this video shows footage from flight days four through six of the STS-105 mission. Commander Scott Horowitz helps Mission Specialist Pat Forrester maneuver the Space Shuttle's robotic arm as it grapples the Multipurpose Logistics Module (MPLM) from Discovery's payload bay to the International Space Station (ISS). The three crews, STS-105 (Commander Horowitz, Pilot Fred Sturckow, and Mission Specialists Dan Barry and Forrester), Expedition 2 (Commander Yuriy Usachev and Flight Engineers James Voss and Susan Helms), and Expedition 3 (Commander Frank Culbertson, Jr. and Flight Engineers Mikhail Turin and Vladimir Dezhurov), are seen during unloading operations as they transfer equipment from the MPLM to the ISS. Forrester and Barry check their equipment and suits for the next day's spacewalks. The E2 crew shows the E3 crew around ISS. The crescent moon and the end of a sunset are seen from space. For activities from flight days 7-13, see 'STS-105 Mission Highlights Resource Tape: Flight Days 7-9' (internal ID 2002046552) and 'STS-105 Mission Highlights Resource Tape: Flight Days 10-13' (internal ID 2002046551).
Source record↗
An analysis of the moon's surface using reflected illumination from the earth during a waning crescent lunar phase
There have been many articles written concerning the lunar after-glow, the spectacular reflection from the moon's surface, and the possible observation of luminescence on the dark side of the moon. The researcher, using a 600 mm cassegrain telescope lense and Kodak 400 ASA T-Max film, photographed the crescent moon whose dark side was clearly visible by the reflected light from earth. The film was digitized to a Perkin-Elmer 1010M microdensitometer for enhancement and enlargement. The resulting pictures indicate a completely different land pattern formation than observed during a full moon. An attempt is made to analyze the observed structures and to compare them to the pictures observed during the normal full moon. There are boundaries on the digitized dark section of the moon that can be identified with structures seen during the normal full moon. But, these variations do change considerably under enhancement.
Hammond, Ernest C., Jr.↗
Advanced C Features
A scientific presentation on function pointers and a dynamic character array.
AGE↗
First Earthshine photography from lunar orbit
During Apollo 15, fifteen photographs of the moon were taken under Earthshine illumination. These were the first Earthshine photographs taken from lunar orbit. The photographs are of photometric interest, particularly as they involve double reflection of sunlight: by the earth, then the moon, prior to photographic exposure. Certain published data on the mean illumination of the moon by the crescent earth predicted lower exposure values than obtained for each measured area. The apparent albedo values obtained for the floor of the crater Aristarchus were anomalously higher than those obtained for the surrounding maria.
Lloyd, D. D.↗
A soft X-ray image of the moon
A soft X-ray image of the moon obtained by the Roentgen Observatory Satellite ROSAT clearly shows a sunlit crescent, demonstrating that the moon's X-ray luminosity arises from backscattering of solar X-rays. The moon's optically dark side is also X-ray dark, and casts a distinct shadow on the diffuse cosmic X-ray background. Unexpectedly, the dark side seems to emit X-rays at a level about one percent of that of the bright side; this emission very probably results from energetic solar-wind electrons striking the moon's surface.
Schmitt, J. H. M. M.↗
Moonwatch - July 14, 1988
The Moonwatch program using amateur astronomers to obtain a wide range of naked-eye sightings of the new moon to test a mathematical model for predicting first visibilty of the new moon is discussed. The algorithm takes physical effects such as brightness of the twilight sky, clarity of the atmosphere at the observing site, and the physiology of the human eye into account. A 1987 test of visibility prediction obtained poor results due to weather conditions. Observers across North and Central America, the Caribbean, and northern South America are asked to record information about the time and location where they first see the crescent of the new moon appear on the horizon.
Doggett, Leroy E.↗
Visibility of the lunar crescent
A model designed to predict whether or not the moon will be visible under any set of observing conditions is presented. It explicitly includes atmospheric clarity, which is calculated from the site's altitude, latitude, temperature, relative humidity, aerosol content, and time of the year. This mathematical model is combined with a lunar and solar ephemeris to yield a computer program which will predict the date of the first crescent sighting from any location. A list of 201 observations of lunar visibility was collected to test this model and other models. It is found that criteria involving the moonset lagtime and the moon's age have zones of uncertainty which typically cover the entire earth.
Schaefer, Bradley E.↗
Lunar crescent visibility
We report the results of five Moonwatches, in which more than 2000 observers throughout North America attempted to sight the thin lunar crescent. For each Moonwatch we were able to determine the position of the Lunar Date Line (LDL), the line along which a normal observer has a 50% probability of spotting the Moon. The observational LDLs were then compared with predicted LDLs derived from crescent visibility prediction algorithms. We find that ancient and medieval rules are higly unreliable. More recent empirical criteria, based on the relative altitude and azimuth of the Moon at the time of sunset, have a reasonable accuracy, with the best specific formulation being due to Yallop. The modern theoretical model by Schaefer (based on the physiology of the human eye and the local observing conditions) is found to have the least systematic error, the least average error, and the least maximum error of all models tested. Analysis of the observations also provided information about atmospheric, optical and human factors that affect the observations. We show that observational lunar calendars have a natural bias to begin early.
Doggett, Leroy E.↗
Evidence for a Stratified Upper Mantle Preserved within the South Pole - Aitken Basin
The evolution and compositional structure of the lunar mantle has been extensively modeled but insufficiently constrained by observations. Here, we identify and characterize mantle materials exposed by the Moon's largest impact basin to better understand the composition, stratigraphy, and evolution of the upper mantle. The vast South Pole-Aitken Basin (SPA) exhibits a broad, crescent-shaped thorium and potassium distribution. These incompatible elements are predicted to be concentrated in the dregs of the lunar magma ocean during end-stage crystallization. Through consideration of basin formation models convolved with subsequent geologic evolution, we demonstrate that the distribution and implied stratigraphy of Th- and K-bearing materials across SPA are consistent with an upper mantle ejecta origin. The most pristine exposures of these materials are confined to northwest SPA and also exhibit elevated Ti and Fe (relative to the farside highlands) in association with a gabbronoritic mineralogy. This is consistent with latestage magma ocean assemblages predicted by petrologic models. In contrast, SPA impact melt derived from greater depths is associated with a low-Ca pyroxene-dominated assemblage. Together, these compositional patterns are evidence for a stratified ancient upper mantle. Importantly, the incompatible-element-enriched, ilmenite-bearing ferroan gabbronoritic cumulates evidently had not participated in gravitational overturn at the time of SPA formation. Contrary to recent hypotheses invoking nearside sequestration of incompatible elements to explain hemispherical differences in crustal building and volcanic resurfacing, it follows that incompatible elements were globally distributed in the magma ocean at the time of SPA formation.
Lunar dichotomy↗
MODELING THE INFRARED SPECTRUM OF THE EARTH-MOON SYSTEM: IMPLICATIONS FOR THE DETECTION AND CHARACTERIZATION OF EARTHLIKE EXTRASOLAR PLANETS AND THEIR MOONLIKE COMPANIONS
The Moon maintains large surface temperatures on its illuminated hemisphere and can contribute significant amounts of flux to spatially unresolved thermal infrared (IR) observations of the Earth-Moon system, especially at wavelengths where Earth's atmosphere is absorbing. In this paper we investigate the effects of an unresolved companion on IR observations of Earthlike exoplanets. For an extrasolar twin Earth-Moon system observed at full phase at IR wavelengths, the Moon consistently comprises about 20% of the total signal, approaches 30% of the signal in the 9.6 {mu}m ozone band and the 15 {mu}m carbon dioxide band, makes up as much as 80% of the signal in the 6.3 {mu}m water band, and more than 90% of the signal in the 4.3 {mu}m carbon dioxide band. These excesses translate to inferred brightness temperatures for Earth that are too large by 20-40 K and demonstrate that the presence of undetected satellites can have significant impacts on the spectroscopic characterization of exoplanets. The thermal flux contribution from an airless companion depends strongly on phase, implying that observations of exoplanets should be taken when the star-planet-observer angle (i.e., phase angle) is as large as feasibly possible if contributions from companions are to be minimized. We show that, by differencing IR observations of an Earth twin with a companion taken at both gibbous and crescent phases, Moonlike satellites may be detectable by future exoplanet characterization missions for a wide range of system inclinations.
79 ASTRONOMY AND ASTROPHYSICS↗
Preliminary report of lunar observations by the Near-Infrared Mapping Spectrometer (NIMS) during the second Galileo Earth-Moon encounter
The Galileo encounter with the Earth-Moon system on 8 Dec. 1992, provided a unique opportunity to observe the Moon. Galileo's closest approach to the Moon was at an altitude of about 110,000 km above an area at about latitude 60N, longitude 60E. During the 12 hours surrounding the time of lunar closest approach, 12 observational sequences were executed by the near-infrared mapping spectrometer (NIMS), many in coordination with other Galileo instruments. These NIMS observations provided nearly complete coverage of the illuminated crescent from phase angles of 123 deg to 14 deg. This phase-angle coverage with nearly constant illumination is not possible from Earth; it is expected to provide substantial new information on the nature of the lunar photometric function over wavelength. As of Jan. 1993, most of the analysis has focused on the highest resolution data (55 km/pixel).
Carlson, R. W.↗
Structural Inventory of Great Basin Geothermal Systems and Definition of Favorable Structural Settings
Structural controls of 426 geothermal systems in the Great Basin region including western Nevada, central Nevada, northwestern Nevada, northeastern Nevada, east-central Nevada, eastern California, southern Oregon, and western Utah were analyzed with literature research, air photos, Google Earth imagery, and/or field reviews. Of the systems analyzed, we were able to determine the structural settings of more than 240 sites. The structural catalogue is stored in a master spreadsheet included in this submission. Data components include structural setting, primary fault orientation, presence or absence of Quaternary faulting, reservoir lithology, geothermometry, presence or absence of recent magmatism, and distinguishing blind systems from those that have surface expressions. Systems were cataloged into the following eight major groups, based on the dominant pattern of faulting: - Major normal fault segments (i.e., near displacement maxima). - Fault bends. - Fault terminations or tips. - Step-overs or relay ramps in normal faults. - Fault intersections. - Accommodation zones (i.e., belts of intermeshing oppositely dipping normal faults), - Displacement transfer zones whereby strike-slip faults terminate in arrays of normal faults. - Transtensional pull-aparts. These settings form a hierarchal pattern with respect to fault complexity. - Major normal faults and fault bends are the simplest. - Fault terminations are typically more complex than mid-segments, as faults commonly break up into multiple strands or horsetail near their ends. - A fault intersection is generally more complex, as it generally contains both multiple fault strands and can include discrete dilational quadrants. - A step-over consists of two overlapping fault terminations and thus involves additional complexity, especially where the relay ramp is breached by multiple fault splays between the main overlapping faults and thus contains multiple fault intersections. - Accommodation zones involve further complexity, as they contain multiple fault terminations and fault intersections.
15 GEOTHERMAL ENERGY↗
Detection of ocean glint and ozone absorption using LCROSS Earth observations
The Lunar CRater Observation and Sensing Satellite (LCROSS) observed the distant Earth on three occasions in 2009. These data span a range of phase angles, including a rare crescent phase view. For each epoch, the satellite acquired near-infrared and mid-infrared full-disk images, and partial-disk spectra at 0.26-0.65 μm (λ/Δλ ∼ 500) and 1.17-2.48 μm (λ/Δλ ∼ 50). Spectra show strong absorption features due to water vapor and ozone, which is a biosignature gas. We perform a significant recalibration of the UV-visible spectra and provide the first comparison of high-resolution visible Earth spectra to the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional spectral Earth model. We find good agreement with the observations, reproducing the absolute brightness and dynamic range at all wavelengths for all observation epochs, thus validating the model to within the ∼10% data calibration uncertainty. Data-model comparisons reveal a strong ocean glint signature in the crescent phase data set, which is well matched by our model predictions throughout the observed wavelength range. This provides the first observational test of a technique that could be used to determine exoplanet habitability from disk-integrated observations at visible and near-infrared wavelengths, where the glint signal is strongest. We examine the detection of the ozone 255 nm Hartley and 400-700 nm Chappuis bands. While the Hartley band is the strongest ozone feature in Earth's spectrum, false positives for its detection could exist. Finally, we discuss the implications of these findings for future exoplanet characterization missions.
79 ASTRONOMY AND ASTROPHYSICS↗