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Full-Text Articles in Engineering

Airborne Wind Energy: Implementation And Design For The U.S. Air Force, Troy L. Cahoon Mar 2011

Airborne Wind Energy: Implementation And Design For The U.S. Air Force, Troy L. Cahoon

Theses and Dissertations

Excitement among researchers about Airborne Wind Energy (AWE) technology matches DoD aims to advance and employ renewable energy. AWE seeks to cost-effectively tap the vast supply of wind energy available at altitudes high above the reach of conventional, ground-based wind turbines (e.g. 500-12,000m). This paper explores viability and implementation of AWE technology for fulfilling USAF energy needs. Characteristics, potential, and developmental status of the AWE resource are presented. A design tool for a rotor-based AWE system is developed, facilitating the analysis of blade performance to simplify design and provide the best efficiencies for a range of conditions. USAF bases are …


An Investigation Of Cavity Resonance And Its Relationship To Store Force And Moment Loading, Christopher J. Coley Mar 2011

An Investigation Of Cavity Resonance And Its Relationship To Store Force And Moment Loading, Christopher J. Coley

Theses and Dissertations

A store which is released from an internal bay is subjected to a highly unsteady flowfield which influences the release characteristics for the store. Pressure transducer information is often used to estimate store loading, although no direct correlation between the observed frequencies from the pressure transducers and the store loading has been developed. The relationship between the acoustic modes present in the cavity and the force and moment loading on a store released from a bay are investigated through a CFD study using the OVERFLOW 2.1 solver. The acoustic modes of the cavity are calculated from the pressure fluctuation histories …


Repeatable Manufacture Of Wings For Flapping Wing Micro Air Vehicles Using Microelectromechanical System (Mems) Fabrication Techniques, David S. Dawson Mar 2011

Repeatable Manufacture Of Wings For Flapping Wing Micro Air Vehicles Using Microelectromechanical System (Mems) Fabrication Techniques, David S. Dawson

Theses and Dissertations

While there have been great advances in the area of Flapping Wing Micro Air Vehicles (FWMAV), prototype parts have been constructed with the objective of scientific discovery and basic research. There has been little effort to make parts that could be consistently and repeatedly manufactured. Until recently, there has been little, if any, focus on methods that could be used and verified by subsequent researchers. It is herein proposed that Microelectromechanical System fabrication methods will provide a fast, cheap, and highly repeatable manufacturing method for the FWMAV wings. The wings manufactured to demonstrate this process, bio-inspired by the Manduca Sexta, …


Performance Characterization Of A Novel Plasma Thruster To Provide A Revolutionary Operationally Responsive Space Capability With Micro- And Nano-Satellites, John-David C. De La Harpe Mar 2011

Performance Characterization Of A Novel Plasma Thruster To Provide A Revolutionary Operationally Responsive Space Capability With Micro- And Nano-Satellites, John-David C. De La Harpe

Theses and Dissertations

Few options currently exist to provide propulsion for extremely small satellites due to design constraints on power, volume, and weight. However, future operation will require a capability to conduct orbital maneuvers, momentum dumping, and precision pointing for these low cost satellites. The research presented here represents the first effort to operate and quantify the performance of a new micro plasma thruster design which provides a novel solution to these disparate competing constraints. The thruster in this study represents a deviation from traditional circular Hall thruster design practices, because it eschews a central magnetic circuit, which results in nearly parallel electric …


Ch-47d Rotating System Fault Sensing For Condition Based Maintenance, Stephen M. Dickerson Mar 2011

Ch-47d Rotating System Fault Sensing For Condition Based Maintenance, Stephen M. Dickerson

Theses and Dissertations

The Department of Defense (DoD) has mandated the use of maintenance practices based on component condition rather than component time in service or age. This new practice is known as Condition Based Maintenance, and it relies on accurate detection and identification of material deficiencies in system components. Rotor system components in rotary-wing aircraft can be difficult to monitor due to the rotational environment experienced by the sensors and the difficulty of signal transmission. Current methods are able to detect the existence of a fault in the rotor system but cannot link the vibrations experienced in the airframe to a specific …


Vibration Interaction In A Multiple Flywheel System, Jordan A. Firth Mar 2011

Vibration Interaction In A Multiple Flywheel System, Jordan A. Firth

Theses and Dissertations

This study uses a linear model of an Integrated Power and Attitude Control System (IPACS) to investigate the vibration interaction between multiple flywheels. An easily extendable Matlab® script is created for the analysis of flywheel vibrations. This script is used to build a vibration model consisting of two active magnetic bearing flywheels mounted on a support structure. The flywheels are rotated at varying speeds, with an imbalance-induced centripetal force in one or both wheels causing vibrations in both wheels. Flywheel and system responses are examined for low frequency vibrations which would cause undesirable excitation to a satellite using IPACS, with …


An Experimental Characterization Of Damping Properties Of Thermal Barrier Coatings At Elevated Temperatures, Oliver T. Easterday Mar 2011

An Experimental Characterization Of Damping Properties Of Thermal Barrier Coatings At Elevated Temperatures, Oliver T. Easterday

Theses and Dissertations

This research program developed the apparatus and associated techniques to mechanically characterize the complex modulus of hard coatings across a temperature range from about 70 deg F to 900 deg F. Major effort in designing, analyzing, and experimentally validating the chamber were performed to establish that it isothermally heated a beam specimen, accomplished modal detuning, and achieved a near free-free boundary condition, and that the chamber was characterized for its forcing excitation. Novel aspects of the chamber include non-contact for the excitation, nearly non-contacted boundary conditions, and measurement of the field variables within the specimen using a hybrid experimental-numerical approach. …


Kam Torus Frequency Generation From Two-Line Element Sets, Gregory R. Frey Mar 2011

Kam Torus Frequency Generation From Two-Line Element Sets, Gregory R. Frey

Theses and Dissertations

The Kolmogorov Arnold and Moser (KAM) theorem states that a lightly perturbed Hamiltonian system will have solutions which lie on a torus. Earlier work by the second author has shown that most Earth satellite orbits perturbed by the geopotential lie on KAM tori. The problem then arises as to how to convert the current satellite tracking orbits to KAM tori. A KAM torus is characterized by three frequencies and three phase angles. The frequencies are essentially the rates of change of the mean anomaly, the longitude of the ascending node, and the argument of perigee. In this paper we explore …


Implementation Of A Rule-Based Open-Loop Control Strategy For A Hybrid-Electric Propulsions System On A Small Rpa, Collin Greiser Mar 2011

Implementation Of A Rule-Based Open-Loop Control Strategy For A Hybrid-Electric Propulsions System On A Small Rpa, Collin Greiser

Theses and Dissertations

Currently fielded electric-powered small remotely-piloted aircraft (RPA) lack endurance desired by warfighters, and internal combustion engine (ICE) RPAs generate undesirable acoustic and thermal signatures. Hybrid-electric (HE) propulsion systems would combine both electric power for endurance and ICE power for cruise and climb modes. Use of HE systems would eliminate undesirable signatures in addition to providing considerable fuel savings over time. Five components were used in this HE system: the ICE, electric motor (EM), electromagnetic clutch, battery pack, and a propeller. Control of such a system in a small RPA has never been attempted before. A rulebased controller was developed to …


Effects Of Air Drag And Lunar Third-Body Perturbations On Motion Near A Reference Kam Torus, Luke J. Hagen Mar 2011

Effects Of Air Drag And Lunar Third-Body Perturbations On Motion Near A Reference Kam Torus, Luke J. Hagen

Theses and Dissertations

The KAM Theory was developed in the 1960s but only in the last decade has it been applied to Earth orbiting satellites. Physical state variables of position and velocity are transformed into KAM Torus variables. The KAM Torus is a geometrical structure similar to that of a multi-dimensional donut. The Earth satellite's motion can be described as traversing the surface of this donut. There are two primary advantages of this transformation: (1) The new generalized coordinates which are analogous with mean anomaly, right ascension of the ascending node, and argument of perigee, increment linearly with time, and (2) Perturbations due …


Osculating Relative Orbit Elements Resulting From Chief Eccentricity And J2 Perturbing Forces, Joshuah A. Hess Mar 2011

Osculating Relative Orbit Elements Resulting From Chief Eccentricity And J2 Perturbing Forces, Joshuah A. Hess

Theses and Dissertations

Relative orbit elements (ROEs) based on a circular chief satellite orbit are erroneous when applied to a perturbed,non-circular reference orbit. In those situations, the ROEs will encounter geometric instability and drift. To counter this, a set of time-variant ROEs have been derived to describe the relative orbit for both the unperturbed, elliptical chief, and the perturbed, circular chief. A highly coupled relationship is found that describes the relative trajectory to higher accuracy when compared to numerical integration. To show the applicability of the ROEs to formation design, methods to initialize a stationary relative orbit are detailed and an algorithm for …


Characterization Of Horizontally-Issuing Reacting Buoyant Jets, Joshua J. Heffernen Mar 2011

Characterization Of Horizontally-Issuing Reacting Buoyant Jets, Joshua J. Heffernen

Theses and Dissertations

This research studied the mixing and combustion behavior of low Reynolds number, horizontally-issuing gaseous fuel jets with ambient air. The study focused on the mixing characteristics of propane and ethylene. These fuels are, respectively, heavy and neutral with respect to air, and were tested at various Froude numbers and laminar tube Reynolds numbers. Using low Froude and Reynolds number flows allowed for isolation of the buoyant jet effects. The process was characterized through the use of a non-invasive, OH Planar Laser-Induced Fluorescence (PLIF) technique, and supplemented with filtered (CH*) and unfiltered high speed imaging. The resulting cross sectional PLIF images …


Optimized Dual Expander Aerospike Rocket, Joshua N. Hall Mar 2011

Optimized Dual Expander Aerospike Rocket, Joshua N. Hall

Theses and Dissertations

Research at the Air Force Institute of Technology (AFIT) focused on designing a cryogenic dual-expander aerospike nozzle (DEAN) upper stage rocket engine to produce 50,000 pounds-force (222.4 kilo-Newtons) vacuum thrust, 464 seconds of vacuum specific impulse and a thrust-to-weight ratio of 106.5. The use of dual expander cycles improves engine reliability, maximizes efficiency, and eliminates some catastrophic failure modes. An upper stage engine with an aerospike nozzle is shorter and lighter than an equivalent performing conventional bell nozzle upper stage engine. Previous research focused on first developing a feasible closed DEAN design model and secondly expanding the model to support …


Revolutionizing Space Propulsion Through The Characterization Of Iodine As Fuel For Hall-Effect Thrusters, Adam C. Hillier Mar 2011

Revolutionizing Space Propulsion Through The Characterization Of Iodine As Fuel For Hall-Effect Thrusters, Adam C. Hillier

Theses and Dissertations

The demand for increased performance in space propulsion systems is higher than ever as missions are becoming more advanced. As the global supply of xenon depletes, missions demanding high thrust will require alternatives. The research presented here examines iodine as an alternate propellant. The propellant was successfully operated through a BHT-200 thruster in the T6 vacuum facility at Busek Co. Inc. A feed system for the iodine was developed for controlled thruster operation at varying conditions. An inverted pendulum was used to take thrust measurements. Thrust to power ratio, anode efficiency, and specific impulse were calculated. Iodine performance is compared …


Fixed-Wing Aircraft Combat Survivability Analysis For Operation Enduring Freedom And Operation Iraqi Freedom, Christopher L. Jerome Mar 2011

Fixed-Wing Aircraft Combat Survivability Analysis For Operation Enduring Freedom And Operation Iraqi Freedom, Christopher L. Jerome

Theses and Dissertations

The primary tenet of the aircraft survivability discipline is threat definition. In order to deliver relevant capabilities and protection to the warfighter it is imperative; therefore, to provide timely, accurate, and actionable threat data to the survivability community. In an attempt to identify the evolution of aircraft threats in today's combat environment, an analysis of fixed-wing aircraft battle damage was conducted. This analysis reports battle damage incidents from OPERATIONS ENDURING FREEDOM (OEF) and IRAQI FREEDOM(OIF). Additionally, reported damage incidents were then validated by crosschecking aircraft maintenance records from this period to eliminate non-hostile fire data points. This revolutionary approach uncovered …


Tension-Compression Fatigue Of Hi-Nicalon/Sic Ceramic Matrix Composite At 1200°C In Air And Steam, Tyler P. Jones Mar 2011

Tension-Compression Fatigue Of Hi-Nicalon/Sic Ceramic Matrix Composite At 1200°C In Air And Steam, Tyler P. Jones

Theses and Dissertations

The primary tenet of the aircraft survivability discipline is threat definition. In order to deliver relevant capabilities and protection to the warfighter it is imperative; therefore, to provide timely, accurate, and actionable threat data to the survivability community. In an attempt to identify the evolution of aircraft threats in today's combat environment, an analysis of fixed-wing aircraft battle damage was conducted. This analysis reports battle damage incidents from OPERATIONS ENDURING FREEDOM (OEF) and IRAQI FREEDOM(OIF). Additionally, reported damage incidents were then validated by crosschecking aircraft maintenance records from this period to eliminate non-hostile fire data points. This revolutionary approach uncovered …


Notch Sensitivity Of Fatigue Behavior Of A Hi-Nicalon/Sic Ceramic Composite With An Oxidation Inhibited Matrix At 1200°C In Air And In Steam, Garrett M. Kurtz Mar 2011

Notch Sensitivity Of Fatigue Behavior Of A Hi-Nicalon/Sic Ceramic Composite With An Oxidation Inhibited Matrix At 1200°C In Air And In Steam, Garrett M. Kurtz

Theses and Dissertations

The effects of holes on the fatigue behavior of an advanced Silicon Carbide/Silicon Carbide (SiC/SiC) ceramic matrix composite (CMC) was investigated at 1200°C in laboratory air and in steam environment. The composite consisted of an oxidation inhibited HyprSiC matrix reinforced with laminated Hi-Nicalon fibers woven in an eight-harness-satin weave (8HSW). Fiber preforms were coated with pyrolytic carbon (PyC) fiber coating with boron carbide overlay and were then densified with HyprSiC matrix via chemical vapor infiltration (CVI). Effects if center hole on tensile stress-strain behavior and tensile properties were evaluated at 1200°C. To assess the effect of holes on fatigue performance, …


Small Internal Combustion Engine Testing For A Hybrid-Electric Remotely-Piloted Aircraft, Isseyas H. Mengistu Mar 2011

Small Internal Combustion Engine Testing For A Hybrid-Electric Remotely-Piloted Aircraft, Isseyas H. Mengistu

Theses and Dissertations

Efficient operation of a hybrid-electric propulsion system (HEPS) powering a small remotely-piloted aircraft (RPA) requires that a controller have accurate and detailed engine and electric motor performance data. Many small internal combustion engines (ICEs) currently used on various small RPA were designed for use by the recreational hobbyist radio-control (R/C) aircraft market. Often, the manufacturers of these engines do not make accurate and reliable detailed engine performance data available for their engines. A dynamometer testing stand was assembled to test various small ICEs. These engines were tested with automotive unleaded gasoline (the manufacturer's recommended fuel) using the dynamometer setup. Torque, …


Detonation Propagation Through Ducts In A Pulsed Detonation Engine, Jeffrey M. Nielsen Mar 2011

Detonation Propagation Through Ducts In A Pulsed Detonation Engine, Jeffrey M. Nielsen

Theses and Dissertations

Development of a continuously operating pulsed detonation engine (PDE) without a high energy ignition system or a deflagration-to- detonation transition (DDT) device will increase engine efficiency, reduce cost, improve performance, and reduce weight. This report is a study of configurations that allow a consistent and predictable transition of a detonation from one detonation tube to second tube. The intent was, via visualization of detonation propagation through a cross-over tube, to develop a cross-over passage leading to minimization of energy losses and effective and repeatable tube-to-tube initiation. Detonation tube cross-over width, cross-over geometry and fuels were varied to determine their effect …


Design Of Attitude Control Actuators For A Simulated Spacecraft, Christopher G. Mcchesney Mar 2011

Design Of Attitude Control Actuators For A Simulated Spacecraft, Christopher G. Mcchesney

Theses and Dissertations

The Air Force Institute of Technology's attitude dynamics simulator, SimSat, is used for hardware-in-the-loop validation of new satellite control algorithms. To provide the capability to test algorithms for control moment gyroscopes, SimSat needed a control moment gyroscope array. The goal of this research was to design, construct, test, and validate a control moment gyroscope array for SimSat. The array was required to interface with SimSat's existing structure, power supply, and electronics. The array was also required to meet maneuver specifications and disturbance rejection specifications. First, the array was designed with initial sizing estimates based on requirements and vehicle size. Next, …


Cubesat Packaged Electrospray Thruster Evaluation For Enhanced Operationally Responsive Space Capabilities, Scott T. Ober Mar 2011

Cubesat Packaged Electrospray Thruster Evaluation For Enhanced Operationally Responsive Space Capabilities, Scott T. Ober

Theses and Dissertations

A new specialized electrospray thruster with a potential to be used with a 3-U CubeSat was operated. The key difference in this thruster from traditional colloid thrusters is the porous stainless steel surface used for the emission sites. With this porous surface the actual location and number of the Taylor cones formations vary with changing fuel flow. The understanding of these formations is discussed with low, moderate, and high flow rates. The limitations of the experiment and observed system response are discussed. Due to these limitations, the colloid thruster was only able to operate in the low mass flow rate …


Experimental Measurements Of Store Separation Using Dry Ice Models In A Subsonic Flow, Michael C. Paul Mar 2011

Experimental Measurements Of Store Separation Using Dry Ice Models In A Subsonic Flow, Michael C. Paul

Theses and Dissertations

Testing free-drop store separation from a cavity in wind tunnels proves a difficult task because the models are typically destroyed during the test. Furthermore, there is potential for damage to wind tunnel components. Prior work has shown that small dry ice models released within the test section do not cause damage to the AFIT pressure-vacuum wind tunnel components or vacuum chamber. Rather, the dry ice models break apart and sublimate harmlessly into gaseous carbon dioxide. Therefore, this study was undertaken to determine whether dry ice models might prove useful in free-drop store separation testing. A generic aircraft cavity was constructed …


Conceptual Design Tool To Analyze Electrochemically-Powered Micro Air Vehicles, Douglas J. Pederson Mar 2011

Conceptual Design Tool To Analyze Electrochemically-Powered Micro Air Vehicles, Douglas J. Pederson

Theses and Dissertations

A multi-fidelity conceptual design tool was developed to assess electrochemically-powered micro air vehicles(MAVs). The tool utilizes four areas of contributing analyses (CAs): aerodynamics, propulsion, power management, and power sources to determine the endurance duration of a given mission. The low-fidelity aerodynamic CA consisted of drag polar calculations and the high-level CA used a vortex theory code called Athena Vortex Lattice (AVL). The propulsion CA employed QPROP and a MATLAB code that used experimental propeller data and motor constants to predict propeller-motor combination performance for the low- and high-fidelity tracks, respectively. The power management CA determined the percentage of required power …


Sizing Analysis For Aircraft Utilizing Hybrid-Electronic Propulsion Systems, Matthew D. Rippl Mar 2011

Sizing Analysis For Aircraft Utilizing Hybrid-Electronic Propulsion Systems, Matthew D. Rippl

Theses and Dissertations

A submerged inlet investigation, using flow control in the form of discrete blowing, examined proximity and jet directionality to improve compressor face uniformity. The flow control locations were at the head of the ramp and part way down the ramp, providing four configurations under examination. Laser Doppler velocimetry (LDV)measurements at the throat determined the effect of the flow control based on the statistical velocity measurements. Blowing at closer proximity to the throat and targeting the largest velocity deficit region provided the best results. The airspeed and inlet velocity simulated takeoff and landing conditions; velocities ranged from Mach 0.1-0.3 at the …


Effect Of Atmospheric Pressure And Temperature On A Small Spark Ignition Internal Combustion Engine's Performance, Peter J. Schmick Mar 2011

Effect Of Atmospheric Pressure And Temperature On A Small Spark Ignition Internal Combustion Engine's Performance, Peter J. Schmick

Theses and Dissertations

The ever increasing use of man portable unmanned aerial vehicles, UAV, by the US military in a wide array of environmental conditions calls for the investigation of engine performance under these conditions. Previous research has focused on individual changes in pressure or temperature conditions of the air stream entering the engine. The need was seen for a facility capable of providing an environment representative of various simulated altitude conditions. A mobile test facility was developed to test small internal combustion engines with peak powers less than 10 hp. A representative engine was tested over a range of speeds from 2000 …


Flapping Wing Micro Air Vehicle Wing Manufacture And Force Testing, Nathanael J. Sladek Mar 2011

Flapping Wing Micro Air Vehicle Wing Manufacture And Force Testing, Nathanael J. Sladek

Theses and Dissertations

Numerous wing manufacturing techniques have been developed by various universities for research on Flapping Wing Micro Air Vehicles. Minimal attention though is given to repeatability of wing aerodynamics and dynamic response, which is crucial to avoid asymmetric flapping. Thus the focus of this research becomes twofold. First, repeatable wing manufacturing techniques are developed to ensure flapping wings have similar aerodynamic and dynamic characteristics. For this purpose, four wing designs were selected to not only test the aerodynamics of the different designs, but to also validate manufacturing techniques. The various wing designs are assessed using two methods: dynamic and aerodynamic data. …


Using A Gatling-Gun Configured Micro Pulsed Plasma Thruster As A Means To Control Micro Satellites With Extreme Precision, Lee I. Watson Mar 2011

Using A Gatling-Gun Configured Micro Pulsed Plasma Thruster As A Means To Control Micro Satellites With Extreme Precision, Lee I. Watson

Theses and Dissertations

Micro-Pulsed Plasma Thrusters (µPPT) are becoming increasingly attractive for their low power consumption and moderately high specific impulse in the range of 800-1200s. The Gatling Gun micro-Pulsed Plasma Thruster (GG-µPPT) is a new device offering reduced mass and higher thrust than single µPPTs and solid application in precise pointing and orbit maintenance applications. The performance of µPPTs depends on frequency and applied voltage/power levels. Variation of these input parameters and effects on operation and performance of this thruster system were the focus of this research. Contamination aspects were also considered and discussed, since the buildup of carbon results in decreased …


Stochastic Orbit Prediction Using Kam Tori, Max W. Yates Mar 2011

Stochastic Orbit Prediction Using Kam Tori, Max W. Yates

Theses and Dissertations

Kolmogorov-Arnold-Moser (KAM) Theory states that a lightly perturbed, conservative, dynamical system will exhibit lasting quasi-periodic motion on an invariant torus. Its application to purely deterministic orbits has revealed exquisite accuracy limited only by machine precision. The theory is extended with new mathematical techniques for determining and predicting stochastic orbits for Earth satellite systems. The linearized equations of motion are developed and a least squares estimating environment is pioneered to fit observation data from the International Space Station to a phase space trajectory that exhibits drifting toroidal motion over a dense continuum of adjacent tori. The dynamics near the reference torus …


Vision-Aided Autonomous Precision Weapon Terminal Guidance Using A Tightly-Coupled Ins And Predictive Rendering Techniques, Jonathan W. Beich Mar 2011

Vision-Aided Autonomous Precision Weapon Terminal Guidance Using A Tightly-Coupled Ins And Predictive Rendering Techniques, Jonathan W. Beich

Theses and Dissertations

This thesis documents the development of the Vision-Aided Navigation using Statistical Predictive Rendering (VANSPR) algorithm which seeks to enhance the endgame navigation solution possible by inertial measurements alone. The eventual goal is a precision weapon that does not rely on GPS, functions autonomously, thrives in complex 3-D environments, and is impervious to jamming. The predictive rendering is performed by viewpoint manipulation of computer-generated of target objects. A navigation solution is determined by an Unscented Kalman Filter (UKF) which corrects positional errors by comparing camera images with a collection of statistically significant virtual images. Results indicate that the test algorithm is …


Two Dimensional Positioning And Heading Solution For Flying Vehicles Using A Line-Scanning Laser Radar (Ladar), Brady T. Christel Mar 2011

Two Dimensional Positioning And Heading Solution For Flying Vehicles Using A Line-Scanning Laser Radar (Ladar), Brady T. Christel

Theses and Dissertations

Emerging technology in small autonomous flying vehicles requires the systems to have a precise navigation solution in order to perform tasks. In many critical environments, such as indoors, GPS is unavailable necessitating the development of supplemental aiding sensors to determine precise position. This research investigates the use of a line scanning laser radar (LADAR) as a standalone two dimensional position and heading navigation solution and sets up the device for augmentation into existing navigation systems. A fast histogram correlation method is developed to operate in real-time on board the vehicle providing position and heading updates at a rate of 10 …