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Daniel Guggenheim School of Aerospace Engineering
Daniel Guggenheim School of Aerospace Engineering
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ItemDisruption and Vaporization of Simulated Fuel Droplets under Locally Supersonic Conditions(Georgia Institute of Technology, 2013-03-07) Hermanson, James C.The disruption of droplets under supersonic conditions was studied in a draw-down supersonic wind tunnel. The test liquids included 2-propanol, tetraethylene glycol dimethyl ether, and a hexanol-pentane 50/50 mixture by volume. The hexanol-pentane mixture has similar physical properties to 2-propanol, but a considerably higher vapor pressure. The droplets were accelerated in the supersonic flow, achieving supersonic velocities relative to the surrounding air. The droplets reached a relative Mach number of as high as 1.8 and Weber number of 320. The droplets were imaged by direct close-up single-and multiple-exposure imaging and by Laser-Induced Fluoresecence (LIF) imaging. The low static pressure in the supersonic stream had the potential to give rise to superheating of the droplet fluid as the local static pressure became significanlty lower than the vapor pressure of the droplet liquid, depending on the test liquid employed. Droplet lifetimes for the more volatile hexanol/pentane mixture appeared to be shorter due to accelerated vaporization consistent with superheating, though little impact was observed on the droplet velocity and relative Mach number. LIF imaging of the expelled vapor indicated that the more volatile liquid droplets had a higher vaporization rate than non-volatile droplets at all downstream locations, suggesting that droplet superheating does play some role in accelerating the vaporization of supersonic droplets under these conditions.
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ItemThe Manned UAV: Where is the Revolution Headed(Georgia Institute of Technology, 2012-11-30) Langford, John S.Where is the UAV revolution headed? One possibility is that it's not about manned versus unmanned, but about degrees of autonomy. Highly automated systems will put a wide range of new aircraft types into the National Airspace System, controlled by operators with a wide range of skills and experience. A step on this road is the "optionally piloted aircraft", some of which are flying today. This talk will review recent progress in unmanned air vehicles, examine some of the challenges of integrating robotic systems in the NAS, and explore the future potential of OPAs.
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ItemHandling Qualities Engineering(Georgia Institute of Technology, 2012-10-17) Padfield, Gareth D.This Nikolsky paper on rotorcraft handling qualities has been written under the enduring influence of a community of very dedicated engineers and pilots. The author looks back nearly 70 years and highlights particular events that reflect the continual growth of the handling qualities discipline and brought us to where we are in 2012. We at a point where designers have, within their grasp, the performance standards, criteria and test techniques, the understanding of rotorcraft aeromechanics and control and the design tools to ensure that handling deficiencies never again have to define the boundary of the operational flight envelope. The tension between flight performance and flight safety is properly managed by ensuring that Level 1 handling qualities are there for pilots throughout missions, including degraded environments and hazardous operations. This paper tells the story of how our industry has arrived at this point. Looking forward, we now need to strive for super-Level 1 handling quality, a state where pilot errors, in any shape or form attributable to deficient flight characteristics, are things of the past. The presentation takes the form of a narrative, describing the story of the idea that HQs can be quantified. During the first few years of the 20th century, the Wright brothers had carefully and thoroughly documented developments with their 1901-2 gliders to their 1903-5 powered aircraft. In contrast, no such recordings are available of the flight behavior of rotary wing aircraft in the 1920-30s. The story therefore begins with the post-war work in the UK and US research laboratories to understand better helicopter flight characteristics and the emergence of the first rotorcraft handling qualities requirements specification. The story then unfolds largely based on documents in the public domain written by engineers and pilots from European and North American industry, research laboratories and academia. This version of the story is also restricted to the single main rotor, “penny-farthing” configuration.
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ItemDamping Models for Shear Beams With Applications to Spacecraft Wiring Harnesses(Georgia Institute of Technology, 2012-09-20) Lesieutre, George A.Damping is an important aspect of aerospace sturctures designed to operate in dynamic environments. Wiring harnesses can significantly affect the dynamics of spacecraft structures. High-fidelity models of the coupled structure-cable dynamic system are needed to accurately predict launch loads and potential control system interactions. A beam model including first-order transverse shear can accurately capture the effects of cable mass and stiffness on dynamic response and provide insight into structural behavior. However, available time-domain damping models are inadequate for use in such a model- common proportional damping models predict modal damping that depends strongly and unrealistically on frequency. Inspired by a geometirc rotation-based viscous damping model that provides frequency-independent modal damping in an Euler-Bernoulli beam model, several time-domain viscous damping models are presented that exhibit weaker frequency dependence than proportional damping models. At low frequencies (bendingdominated modes), the models provide modal damping that is either directly or inversely proportional to the mode number. Model predictions compare favorably to available experimental data.
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ItemCuriosity’s Landing on Mars & the Future of Space Exploration(Georgia Institute of Technology, 2012-08-29) Elachi, CharlesOver the last 50 years, JPL spacecraft have visited every planet in our solar system and roved for more than 8 years on the surface of Mars. In addition, space borne telescopes have detected planets around neighboring systems, studied the composition and dynamic of galaxies across the Universe, and monitored changes in our planet’s surface and atmosphere. In this presentation, Dr. Charles Elachi will discuss the challenges of robotic space and Earth exploration, highlights of Curiosity’s recent landing on Mars, and present some of the engineering and technological challenges for future missions of exploration and discovery.