Aerospace Engineering Commons^™

High-Efficiency Thrust Vector Control Allocation, Jeb S. Orr, Nathan Slegers

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

A generalized approach to the allocation of redundant thrust vector slew commands for multi-actuated launch vehicles is presented, where deflection constraints are expressed as omniaxial or elliptical deflection limits in gimbal axes. More importantly than in the aircraft control allocation problem, linear allocators (pseudoinverses) are preferred for large booster applications to facilitate accurate prediction of the control-structure interaction resulting from thrust vectoring effects. However, strictly linear transformations for the allocation of redundant controls cannot, in general, access all of the attainable moments for which there is a set of control effector positions thatsatisfles the constraints. In this paper, the control …

Gust Mitigation Of Micro Air Vehicles Using Passive Articulated Wings, Adetunji Oduyela, Nathan Slegers

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Birds and insects naturally use passive flexing of their wings to augment their stability in uncertain aerodynamic environments. In a similar manner, micro air vehicle designers have been investigating using wing articulation to take advantage of this phenomenon. The result is a class of articulated micro air vehicles where artificial passive joints are designed into the lifting surfaces. In order to analyze how passive articulation affects performance of micro air vehicles in gusty environments, an efficient 8 degree-of-freedom model is developed. Experimental validation of the proposed mathematical model was accomplished using flight test data of an articulated micro air vehicle …

A Mobile Self-Leveling Landing Platform For Small-Scale Uavs, Stephen Austin Conyers

Electronic Theses and Dissertations

This thesis presents a semi-autonomous mobile self-leveling landing platform designed to launch, recover and re-launch VTOL UAVs without the need for human intervention. The landing platform is rugged, lightweight and inexpensive, making it ideal for civilian applications that require a base station from which a rotorcraft UAV can be launched and recovered on terrain that is normally unsuitable for UAV operations. This landing platform is capable of self-leveling on rough terrain and inclined slopes, and can autonomously operate in remote locations for extended periods of time using large onboard lithium batteries and wireless communication. This thesis discusses the unique design …

Aerodynamic Design And Development Of The Sunswift Iv Solar Racing Car, Graham Doig, Chris Beves

Aerospace Engineering

The aerodynamic design and development of the University of New South Wales' ultra-low-drag solar-electric Sunswitt IV car is described, detailing the student-led design process from initial concept sketches to the completed vehicle. The body shape was established and relined over a period of six months in 2008-2009, almost entirely using computational fluid dynamics. The guiding philosophy was that predictable handling and drag minimization in challenging, changing wind conditions of the type commonly seen during the World Solar Challenge across Australia was preferable to high performance only on 'perfect' days. The car won its class in the 2009 and 2011 World …

Implications Of Compressibility Effects For Reynolds-Scaled Testing Of An Inverted Wing In Ground Effect, G. Doig, Tracie J. Barber, Sammy Diasinos

Aerospace Engineering

The influence of compressibility around an isolated inverted wing at a fixed Reynolds number was examined as relevant to the issue of wind tunnel scaling effects. Three-dimensional simulations were conducted for low ground clearances, at: full scale and a Mach number of 0.088, at 50% scale at Mach 0.176, and at 25% scale at Mach 0.352. As the scale was reduced, the increasing peak local Mach number between the wing and the ground resulted in a higher propensity of the flow to separate towards the trailing edge, and for incompressible or full-scale CFD to underestimate the lift and drag coefficients …

A Mathematical Framework For Unmanned Aerial Vehicle Obstacle Avoidance, Sorathan Chaturapruek

HMC Senior Theses

The obstacle avoidance navigation problem for Unmanned Aerial Vehicles (UAVs) is a very challenging problem. It lies at the intersection of many fields such as probability, differential geometry, optimal control, and robotics. We build a mathematical framework to solve this problem for quadrotors using both a theoretical approach through a Hamiltonian system and a machine learning approach that learns from human sub-experts' multiple demonstrations in obstacle avoidance. Prior research on the machine learning approach uses an algorithm that does not incorporate geometry. We have developed tools to solve and test the obstacle avoidance problem through mathematics.

Nonlinear Dynamics And Anisotropic Structure Of Rotating Sheared Turbulence, Abdelaziz Salhi, Frank G. Jacobitz, Kai Schneider, Claude Cambon

School of Engineering: Faculty Scholarship

Homogeneous turbulence in rotating shear flows is studied by means of pseudospectral direct numerical simulation and analytical spectral linear theory (SLT). The ratio of the Coriolis parameter to shear rate is varied over a wide range by changing the rotation strength, while a constant moderate shear rate is used to enable significant contributions to the nonlinear interscale energy transfer and to the nonlinear intercomponental redistribution terms. In the destabilized and neutral cases, in the sense of kinetic energy evolution, nonlinearity cannot saturate the growth of the largest scales. It permits the smallest scale to stabilize by a scale-by-scale quasibalance between …

Design And Evaluation Of A Propulsion System For Small, Compact, Low-Speed Maneuvering Underwater Vehicles, Florence M. Mbithi

Electronic Theses and Dissertations

Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed …

A Decision Making Framework With Modflow-Fmp2 Via Optimization: Determining Trade-Offs In Crop Selection, K R. Fowler, E W. Jenkins, C Ostrove, J C. Chispell, M W. Farthing, M Parno

United States Army Corps of Engineers, Omaha District

Farmers in regions experiencing water stress or drought conditions can struggle to balance their crop portfolios. Periods of low precipitation often lead to increased, unsustainable reliance on groundwatersupplied irrigation. As a result, regional water management agencies place limits on the amount of water which can be obtained from groundwater, requiring farmers to reduce acreage for more water-intensive crops or remove them from the portfolio entirely. Real-time decisions must be made by the farmer to ensure viability of their farming operation and reduce the impacts associated with limited water resources. Evolutionary algorithms, coupled with accurate, flexible, realistic simulation tools, are ideal …

Sweeping Langmuir Probe (Slp) Of The Storms Sounding Rocket Mission, Padmashri Suresh, Charles Swenson

Browse all Datasets

On October 30, 2007 NASA launched rocket 36.218 carrying the mission: “Investigation of Mid Latitude Ionospheric Irregularities Associated with Terrestrial Weather Systems” also known as the STORMS Mission. The rocket was launched from Wallops Island, Virginia (37.95◦ N, 284.53◦ E, 67.5◦ dip angle) at twelve minutes past local midnight. It flew along an azimuth of 114◦ and reached apogee near 394 km. The rocket payload had a suite of instruments from Utah State University/Space Dynamic Lab (USU/SDL) and University of Texas, Dallas (UTD), for making in-situ electron density, wind and electric field measurements.

The Sweeping Langmuir Probe or SLP was …

Airmen With Mild Traumatic Brain Injury (Mtbi) At Increased Risk For Subsequent Mishaps, Casserly R. Whitehead, Timothy S. Webb, Timothy S. Wells, Kari L. Hunter

United States Air Force: Publications

Background: Little is known regarding long-term performance decrements associated with mild Traumatic Brain Injury (mTBI). The goal of this study was to determine if individuals with an mTBI may be at increased risk for subsequent mishaps. Methods: Cox proportional hazards modeling was utilized to calculate hazard ratios for 518,958 active duty U.S. Air Force service members (Airmen) while controlling for varying lengths of followup and potentially confounding variables. Two non-mTBI comparison groups were used; the second being a subset of the original, both without head injuries two years prior to study entrance. Results: Hazard ratios indicate that the causes of …

Autonomous Capabilities For Small Unmanned Aerial Systems Conducting Radiological Response: Findings From A High-Fidelity Discovery Experiment, Brittany Duncan, Robin Murphy

School of Computing: Faculty Publications

This article presents a preliminary work domain theory and identifies autonomous vehicle, navigational, and mission capabilities and challenges for small unmanned aerial systems (SUASs) responding to a radiological disaster. Radiological events are representative of applications that involve flying at low altitudes and close proximities to structures. To more formally understand the guidance and control demands, the environment in which the SUAS has to function, and the expected missions, tasks, and strategies to respond to an incident, a discovery experiment was performed in 2013. The experiment placed a radiological source emitting at 10 times background radiation in the simulated collapse of …

Thermal Conduction And Heat Generation Phenomena In Li-Ion Cells, Stephen Drake

Mechanical and Aerospace Engineering Dissertations - Archive

Cylindrical lithium ion (Li-ion) cells have demonstrated high power density and energy capacity among other energy storage devices. Despite their already widespread use, the thermal transport properties of cylindrical Li-ion batteries are not well documented and understood, while a sizable amount of work has been carried out for electrical, electrochemical, and materials optimization of Li-ion cells. These thermal phenomena are particularly important for high discharge rate batteries. With this uncertainty, if thermophysical properties are not accounted for in thermal models, the result may be a significant under-prediction or over-prediction of the temperature field in a Li-ion cell.Experimental techniques are described …

Unsteady Thrust Measurement Techniques For Pulse Detonation Engines, Dibesh Dhoj Joshi

Mechanical and Aerospace Engineering Dissertations - Archive

Thrust is a critical performance parameter and its correct determination is necessary to characterize an engine. Many conventional thrust measurement techniques prevail. However, further developments are required for correct measurement of thrust in the case of a pulse detonation engine (PDE), since the entire thrust generation process is intermittent. The significant effect of system dynamics in the form of inertial forces, stress wave propagation and reflections initiated in the structure due to detonations and pulse-to-pulse interaction in a fast operating PDE further complicate the thrust measurement process. These complications call for a further, detailed study of the unsteady thrust characteristics. …

Experimental Investigation Of Nucleate Boiling And Thin-Film Evaporation On Enhanced Silicon Surfaces, Shailesh Malla

Mechanical and Aerospace Engineering Dissertations - Archive

The present work consists of two major studies. The first study investigates the effects of surface energy or wettability on nucleate pool boiling and the second study investigates the thin-film evaporative cooling for near junction thermal management. For the first study, effects of surface energy or wettability on critical heat flux (CHF) and boiling heat transfer (BHT) of smooth heated surfaces was studied in saturated pool boiling of water at 1 atm. For this purpose hydrophilic and hydrophobic surfaces were created on one side of 1cm x 1cm double-side polished silicon substrates. A resistive heating layer was applied on the …

Degradation Mechanics Of Bone And Bone Like Materials Via Multiscale Analysis, Md Farzad Sarker

Mechanical and Aerospace Engineering Dissertations - Archive

Bone fracture is a common health risk for older people suffering from bone disease like osteoporosis. The more severe the osteoporosis is the more structural degradation in bones occurs, which eventually makes bones more fracture prone. The mechanical behavior of bone depends on the structural response of bone constituents over a broad range of length scales spanning from the nanoscale collagen fibril level to the macroscale trabeculae level. As such, in order to understand bone fracture, it is important to know the structure-property relations of bone material over the entire length of scale. Surprisingly, a quantitative understanding of bone fracture …

Wind Field Estimation And Its Utilization In Trajectory And Input Prediction, Jane-Wit Kampoon

Mechanical and Aerospace Engineering Dissertations - Archive

This dissertation work develops a method for onboard estimation of wind field with spatial and temporal variation based on local wind vector estimation and/or measurements from multiple aircraft flying in the same airspace. Aircraft flying in the same airspace of operation are considered airborne wind sensors scattered over the airspace because of the fact that aircraft carry along with them wind information inherent in their dynamics and kinematics. The onboard wind field estimation is formulated in the framework of parameter estimation based on various wind field models, which are different function of position and time. The online wind field estimation …

Electrowetting On Dielectric Digital Microfluidics For 3-Dimensional Cell Culture And Chemical Screening, Subin Mac George

Mechanical and Aerospace Engineering Dissertations - Archive

Microfluidic devices have allowed improved cell culture studies to be carried out by allowing greater spatiotemporal control over the cell environment while at the same time providing greater throughput, increased automation capabilities and reagent savings. To improve the relevancy of such studies, 3-dimensional (3D) cell culture has been attempted in microfluidic devices. 3D cell culture is known to better mimic and recreate the environment that cells in the body experience as compared to conventional 2-dimensional cell culture. However, incorporating 3D cell culture into conventional channel based microfluidic devices have proven to be challenging. Hydrogels which provide the 3D environment in …

Modeling, Estimation, And Analysis Of Unresolved Space Object Tracking And Identification, Laura Suarez Henderson

Mechanical and Aerospace Engineering Dissertations - Archive

The problem of orbit determination along with shape determination is significant. The orbit determination problem has been tackled for centuries by some of the greatest mathematicians and physicists. The issue of shape determination of space objects, although more recent, has also been addressed quite extensively. Nevertheless, these problems remain of great interest in the scientific and engineering community, and are addressed in this work. The greatest motivation for the tracking and identification of Earth orbiting objects is the ever-increasing population of space assets and man-made debris. It is of interest to implement new and better techniques to track and identify …

Investigation Of Wetting States On Microstructures After Liquid Drops Contact Groove Base, Mingming Xiang

Mechanical and Aerospace Engineering Dissertations - Archive

Wetting properties of roughness surfaces have attracted a considerable attention because of both the scientific insight and the practical applications. One of the most intriguing topics of wetting is the so-called Cassie-Baxter and Wenzel transition. Recently, theoretical and experimental works have been done to explore this transition on microstructure-formed surfaces. One of the criteria that most commonly used to judge such transition is whether a liquid drop contacts the base of a roughness groove. It is expected that, after the contact, liquid immediately fills the roughness groove, and subsequently the wetting state is changed from Cassie-Baxter state to that of …