1,185 research outputs found
Solar cell angular position transducer
An angular position transducer utilizing photocells and a light source is disclosed. The device uses a fully rotatable baffle which is connected via an actuator shaft to the body whose rotational displacement is to be measured. The baffle blocks the light path between the light source and the photocells so that a constant semicircular beam of light reaches the photocells. The current produced by the photocells is fed through a resistor, a differential amplifier measures the voltage drop across the resistor which indicates the angular position of the actuator shaft and hence of the object
Experimental parametric studies of transonic T-tail flutter
Wind-tunnel tests of the T-tail of a wide-body jet airplane were made at Mach numbers up to 1.02. The model consisted of a 1/13-size scaled version of the T-tail, fuselage, and inboard wing of the airplane. Two interchangeable T-tails were tested, one with design stiffness for flutter-clearance studies and one with reduced stiffness for flutter-trend studies. Transonic antisymmetric-flutter boundaries were determined for the models with variations in: (1) fin-spar stiffness, (2) stabilizer dihedral angle (-5 deg and 0 deg), (3) wing and forward-fuselage shape, and (4) nose shape of the fin-stabilizer juncture. A transonic symmetric-flutter boundary and flutter trends were established for variations in stabilizer pitch stiffness. Photographs of the test configurations are shown
Transonic flutter study of a 50.5 deg cropped-delta wing with two rearward-mounted nacelles
Transonic flutter characteristics of three geometrically similar delta-wing models were experimentally determined in the Langley transonic dynamics tunnel at Mach numbers from about 0.6 to 1.2. The models were designed to be simplified versions of an early supersonic transport wing design. The model was an aspect-ratio-1.28 cropped-delta wing with a leadingedge sweep of 50.5 deg. The flutter characteristics obtained for this wing configuration indicated a minimum flutter-speed index near a Mach number of 0.92 and a transonic compressibility dip amounting to about a 27-percent decrease in the flutter-speed index relative to the value at a Mach number of 0.6. Analytical studies were performed for one wing model at Mach numbers of 0.6, 0.7, 0.8, and 0.9 by using both doublet-lattice and lifting-surface (kernel-function) unsteady aerodynamic theory. A comparison of the analytical and experimental flutter results showed good agreement at all Mach numbers investigated
Development and demonstration of a flutter-suppression system using active controls
The application of active control technology to suppress flutter was demonstrated successfully in the transonic dynamics tunnel with a delta-wing model. The model was a simplified version of a proposed supersonic transport wing design. An active flutter suppression method based on an aerodynamic energy criterion was verified by using three different control laws. The first two control laws utilized both leading-edge and trailing-edge active control surfaces, whereas the third control law required only a single trailing-edge active control surface. At a Mach number of 0.9 the experimental results demonstrated increases in the flutter dynamic pressure from 12.5 percent to 30 percent with active controls. Analytical methods were developed to predict both open-loop and closed-loop stability, and the results agreed reasonably well with the experimental results
Methanol in the sky with diamonds
The present of gas phase methanol in dense interstellar molecular clouds was established by radio detection of its rotational emission lines. However, the position, width, and profile of a absorption band near 1470 cm(exp -1) in the IR spectra of many dense molecular clouds strongly suggests that solid methanol is an important component of interstellar ices. In an attempt to better constrain the identification of 1470 cm(exp -1) feature, we began a program to search for other characteristic absorption bands of solid state methanol in the spectra of objects known to produce this band. One such feature is now identified in the spectra of several dense molecular clouds and its position, width, and profile fit well with those of laboratory H2O:CH3OH ices. Thus, the presence of methanol-bearing ices in space is confirmed
A Transiting Jupiter Analog
Decadal-long radial velocity surveys have recently started to discover
analogs to the most influential planet of our solar system, Jupiter. Detecting
and characterizing these worlds is expected to shape our understanding of our
uniqueness in the cosmos. Despite the great successes of recent transit
surveys, Jupiter analogs represent a terra incognita, owing to the strong
intrinsic bias of this method against long orbital periods. We here report on
the first validated transiting Jupiter analog, Kepler-167e (KOI-490.02),
discovered using Kepler archival photometry orbiting the K4-dwarf KIC-3239945.
With a radius of , a low orbital eccentricity
() and an equilibrium temperature of K,
Kepler-167e bears many of the basic hallmarks of Jupiter. Kepler-167e is
accompanied by three Super-Earths on compact orbits, which we also validate,
leaving a large cavity of transiting worlds around the habitable-zone. With two
transits and continuous photometric coverage, we are able to uniquely and
precisely measure the orbital period of this post snow-line planet
( d), paving the way for follow-up of this mag
target.Comment: 14 pages, 10 figures. Accepted to ApJ. Posteriors available at
https://github.com/CoolWorlds/Kepler-167-Posterior
Comparison of the Organic Composition of Cometary Samples with Residues Formed from the UV Irradiation of Astrophysical Ice Analogs
The NASA Stardust mission successfully collected material from Comet 81P/Wild 2 [1], including authentic cometary grains [2]. X-ray absorption near-edge structure (XANES) spectroscopy analysis of these samples indicates the presence of oxygen-rich and nitrogen-rich organic materials, which contain a broad variety of functional groups (carbonyls, C=C bonds, aliphatic chains, amines, arnides, etc.) [3]. One component of these organics appears to contain very little aromatic carbon and bears some similarity to the organic residues produced by the irradiation of ices of interstellar/cometary composition, Stardust samples were also recently shown to contain glycine, the smallest biological amino acid [4]. Organic residues produced froth the UV irradiation of astrophysical ice analogs are already known to contain a large suite of organic molecules including amino acids [5-7], amphiphilic compounds (fatty acids) [8], and other complex species. This work presents a comparison between XANES spectra measured from organic residues formed in the laboratory with similar data of cometary samples collected by the Stardust missio
Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) Mission Concept
The AstroBiology Explorer (ABE) mission concept consists of a dedicated space observatory having a 60 cm class primary mirror cooled to T 2000 of about 1500 objects including galaxies, stars, planetary nebulae, young stellar objects, and solar system objects. Keywords: Astrobiology, infrared, Explorers, interstellar organics, telescope, spectrometer, space, infrared detector
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The Stardust – a successful encounter with the remarkable comet Wild 2
On January 2, 2004 the Stardust spacecraft completed a close flyby of comet Wild2 (P81). Flying at a relative speed of 6.1 km/s within 237km of the 5 km nucleus, the spacecraft took 72 close-in images, measured the flux of impacting particles and did TOF mass spectrometry
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