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Air Force Institute of Technology

Theses and Dissertations

2005

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Articles 1 - 30 of 181

Full-Text Articles in Engineering

Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker Dec 2005

Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker

Theses and Dissertations

Limit-cycle oscillation, or LCO, is an aeroelastic phenomenon characterized by limited amplitude, self-sustaining oscillations produced by fluid-structure interactions. In order to study this phenomenon, code was developed to interface a modal structural model with a commercial computational fluid dynamics program. LCO was simulated for a rectangular wing, referred to as the Goland+ wing. It was determined that the aerodynamic nonlinearity responsible for LCO in the Goland+ wing was the combination of strong trailing-edge and lambda shocks which periodically appear and disappear. This mechanism limited the flow of energy into the structure which quenched the growth of the flutter, resulting …

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Multiple Channel Laser Beam Combination And Phasing Using Stimulated Brillouin Scattering In Optical Fibers, Brent W. Grime Dec 2005

Multiple Channel Laser Beam Combination And Phasing Using Stimulated Brillouin Scattering In Optical Fibers, Brent W. Grime

Theses and Dissertations

Brightness scaling lasers using stimulated Brillouin scattering (SBS) in optical fibers is explored. A multiple-channel amplifier approach is used to increase the total power of a laser system while avoiding a significant burden on a single channel. The work explores two approaches utilizing both SBS beam cleanup and SBS piston error conjugation. A unique beam combiner that takes advantage of the SBS beam cleanup properties of a long, gradient-index multimode fiber was designed and tested. The beam combiner was developed to combine multiple-channel laser beams simultaneously with high input and output coupling efficiency. The design for the SBS beam combiner …

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Modeling, Stability, And Control Of A Rotatable Tail On A Micro Air Vehicle, Travis J. Higgs Dec 2005

Modeling, Stability, And Control Of A Rotatable Tail On A Micro Air Vehicle, Travis J. Higgs

Theses and Dissertations

This research uses existing experimental wind tunnel data to develop a non-linear model that is used to characterize the stability of a flexible wing Micro Air Vehicle (MAV) with a rotatable tail. The experimental data are curve fit based on either angle of attack or angle of sideslip, and the coupled effect of tail rotation and tail deflection on the force and moment coefficients. Static optimization trims the input and state variables for Steady Level Unaccelerated Flight (SLUF). The resulting initial conditions are fed to an open loop non-linear Simulink/Matlab simulation. The study found that the bare MAV design is …

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Gaussian Mixture Reduction For Bayesian Target Tracking In Clutter, David J. Petrucci Dec 2005

Gaussian Mixture Reduction For Bayesian Target Tracking In Clutter, David J. Petrucci

Theses and Dissertations

The Bayesian solution for tracking a target in clutter results naturally in a target state Gaussian mixture probability density function (pdf) which is a sum of weighted Gaussian pdf's, or mixture components. As new tracking measurements are received, the number of mixture components increases without bound, and eventually a reduced-component approximation of the original Gaussian mixture pdf is necessary to evaluate the target state pdf efficiently while maintaining good tracking performance. Many approximation methods exist, but these methods are either ad hoc or use rather crude approximation techniques. Recent studies have shown that a measure-function-based mixture reduction algorithm (MRA) may …

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Performance Measurements Of Direct Air Injection In A Cavity-Based Flameholder For A Supersonic Combustor, Scott G. Edens Dec 2005

Performance Measurements Of Direct Air Injection In A Cavity-Based Flameholder For A Supersonic Combustor, Scott G. Edens

Theses and Dissertations

For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Recent investigations have focused on the use of direct air injection into a directly-fueled cavity-based flameholder. Direct air injection has been shown qualitatively to be a valuable tool for improving cavity combustion. Little quantitative data is available that characterizes the performance of cavity-based flameholders. The objective of this research was to quantitatively determine the specific advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream …

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Leveraging Itil To Govern Aoc Information Technology, Robert V. Weaver Iii Dec 2005

Leveraging Itil To Govern Aoc Information Technology, Robert V. Weaver Iii

Theses and Dissertations

The Air Operations Center (AOC) is a complex system of systems that is resistant to traditional engineering controls and management strategies. The US Air Force (USAF) seeks to transform its antiquated AOC Information Technology (IT) management function into an agile enterprise capable of leveraging cutting-edge technology by aligning the AOC's infrastructure with its organizational strategies and vision. The USAF calls this effort a transformation. Private industry calls it IT Governance. To achieve AOC IT Governance, the USAF must stop managing infrastructure components and start managing IT services. IT Service Management abstracts business processes from the technology supporting them by creating …

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Characterization Of Binary Offset Carrier (Boc) Systems Coexisting With Other Wideband Signals, John M. Hedenberg Dec 2005

Characterization Of Binary Offset Carrier (Boc) Systems Coexisting With Other Wideband Signals, John M. Hedenberg

Theses and Dissertations

Results for modeling, simulation, and analysis of interference effects that modern interfering signals have on the system performance of the Binary Offset Carrier (BOC) signals, such as the Global Positioning System (GPS) Military System (M-Code signal) are addressed in this work. Three signals are addressed as potential interferers. These include the current GPS clear/acquisition code (C/A-Code) signal, the current GPS precision code (P-Code) signal, and an Orthogonal Frequency Division Multiplexed (OFDM) signal. All of these potential interferers are modeled as coexisting within the same bandwidth as the M-Code signal. Interference effects are characterized by comparing the bit error performance of …

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Wind Tunnel Study Of Interference Effects Relating To Aft Supersonic Ejection Of A Store, Timothy P. Jung Dec 2005

Wind Tunnel Study Of Interference Effects Relating To Aft Supersonic Ejection Of A Store, Timothy P. Jung

Theses and Dissertations

An investigation into the issues surrounding the release of a store into a supersonic wake was conducted. A 10-degree half-angle cone was used to model the carrier vehicle as well as the store. The store was 42% than the vehicle. The experiments were conducted at a freestream Mach number of 2.93 and at zero degrees angle of attack. This study analyzed the effects of a support or strut mounted under the wind tunnel model. Research was conducted on the effects of a store at various positions in the wake, as well as the effects of a rear cavity in the …

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Effects Of Boundary Layer Flow Control Using Plasma Actuator Discharges, Jeffrey M. Newcamp Sep 2005

Effects Of Boundary Layer Flow Control Using Plasma Actuator Discharges, Jeffrey M. Newcamp

Theses and Dissertations

This study addresses the usage and effects of atmospheric plasma discharges on the near wall flow conditions for a Pak-B low-pressure turbine blade. A plasma actuator was built normal to the freestream flow in a low-speed wind tunnel. The test section of the wind tunnel had a contoured upper wall geometry designed to mimic the suction side of a Pak-B turbine blade. A high frequency ac voltage source supplied three voltages in the kilovolt range at four Reynolds numbers in the experiment, between 10,000 and 103,000. The effect of the plasma on the near-wall boundary layer conditions was evaluated at …

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Establishment Of A System Operating Characteristic For Autonomous Wide Area Search Vehicles, Brian A. Kish Sep 2005

Establishment Of A System Operating Characteristic For Autonomous Wide Area Search Vehicles, Brian A. Kish

Theses and Dissertations

The optimal employment of autonomous search and destroy vehicles is addressed. The results apply to air, land, or water vehicles with 1, k, or infinite warheads. The specific scenarios considered involve an air vehicle searching a battle space for stationary targets in the presence of false targets. Encounters are modeled with uniform, Poisson, and normal distributions. Linear and circular search patterns are examined. All relevant parameters are extracted from intelligence information, the sensor performance specification, and the air vehicle performance specification. Analytic system effectiveness measures are derived using applied probability theory. The effectiveness measures derived in this dissertation handle time-varying …

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Rate Dependence And Short Term Creep Behavior Of Pmr-15 Neat Resin At 23 And 288°C, Candice M. Westberry Sep 2005

Rate Dependence And Short Term Creep Behavior Of Pmr-15 Neat Resin At 23 And 288°C, Candice M. Westberry

Theses and Dissertations

This research focuses on experimental investigation of rate-dependent behavior and short-term creep of PMR-15 neat resin at 23 and 288°C. Effect of loading rate on monotonic stress-strain behavior was explored in monotonic tests at constant stress rates of 0.75, 0.075, and 0.0075 MPa/s at 23 and 288°C. In addition, effect of prior stress rate on creep behavior was explored in creep tests preceded by uninterrupted loading to a target stress. At each temperature three creep tests were conducted for a given stress level, where loading rate was changed from test to test. Creep stress levels were 30 and 25 MPa …

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Nonlinear Regression Methods For Estimation, Eric B. Nelson Sep 2005

Nonlinear Regression Methods For Estimation, Eric B. Nelson

Theses and Dissertations

Regression techniques are developed for batch estimation and applied to three specific areas, namely, ballistic trajectory launch point estimation, adaptive flight control, and radio-frequency target triangulation. Specifically, linear regression with an intercept is considered in detail. An augmentation formulation is developed. Extensions of theory are applied to nonlinear regression as well. The intercept parameter estimate within the linear regression is used to identify the effects of trim change that are associated with the occurrence of a control surface failure. These estimates are used to adjust the inner loop control gains via a feed-forward command, hence providing an automatic reconfigurable retrim …

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Operator State Estimation For Adaptive Aiding In Uninhabited Combat Air Vehicles, Christopher A. Russell Sep 2005

Operator State Estimation For Adaptive Aiding In Uninhabited Combat Air Vehicles, Christopher A. Russell

Theses and Dissertations

This research demonstrated the first closed-loop implementation of adaptive automation using operator functional state in an operationally relevant environment. In the Uninhabited Combat Air Vehicle (UCAV) environment, operators can become cognitively overloaded and their performance may decrease during mission critical events. This research demonstrates an unprecedented closed-loop system, one that adaptively aids UCAV operators based on their cognitive functional state A series of experiments were conducted to 1) determine the best classifiers for estimating operator functional state, 2) determine if physiological measures can be used to develop multiple cognitive models based on information processing demands and task type, 3) determine …

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A Prediction Code For The Thrust Performance Of Two-Dimensional, Non-Axisynnetric, Converging Diverging Nozzles, Angela M. Geatz Sep 2005

A Prediction Code For The Thrust Performance Of Two-Dimensional, Non-Axisynnetric, Converging Diverging Nozzles, Angela M. Geatz

Theses and Dissertations

The objective of this research is to develop a prediction code for the Air Force Research Laboratory Propulsion Directorate that can accurately determine the gross thrust coefficient for a user defined nonaxisymmetric two-dimensional converging diverging nozzle. The code includes the effects of friction, angularity, and expansion losses on nozzle efficiency. To demonstrate the prediction method, the generated computational results were compared to experimental data, as well as computational results from other existing nozzle performance codes, for a number of different nozzle geometries. The nozzle internal performance prediction code showed excellent agreement with experimental data in predicting the gross thrust performance …

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Combat Identification With Sequential Observations, Rejection Option, And Out-Of-Library Targets, Timothy W. Albrecht Sep 2005

Combat Identification With Sequential Observations, Rejection Option, And Out-Of-Library Targets, Timothy W. Albrecht

Theses and Dissertations

This research extends a mathematical framework to select the optimal sensor ensemble and fusion method across multiple decision thresholds subject to warfighter constraints for a combat identification (CID) system. The formulation includes treatment of exemplars from target classes on which the CID system classifiers are not trained (out-of-library classes) and enables the warfighter to optimize a CID system without explicit enumeration of classifier error costs. A time-series classifier design methodology is developed and applied, yielding a multi-variate Gaussian hidden Markov model (HMM). The extended CID framework is used to compete the HMM-based CID system against a template-based CID system. The …

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The Effect Of Aerodynamic Surfaces Versus Thrust Maneuvers On Reentry Vehicles, Meredith M. Albrecht Sep 2005

The Effect Of Aerodynamic Surfaces Versus Thrust Maneuvers On Reentry Vehicles, Meredith M. Albrecht

Theses and Dissertations

This research effort analyzes the effect of aerodynamic surfaces versus thrust maneuvers on a reentry vehicle. At high altitudes the effect of aerodynamic surfaces on the reentry vehicle is small due to low atmospheric density; however as the vehicle reaches lower altitudes a lift maneuver is very successful in deflecting the vehicle and creating a large impact footprint. When a continuous thrust maneuver is input in the place of a lift maneuver the results are very similar at the highest maneuver altitudes, although the impact footprint shrinks rapidly as the maneuver altitude decreases. Additionally, when the thrust maneuver is along …

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Characterization Of The Global Hawk Low Pressure Turbine First Rotor, Timothy L. Garmoe Sep 2005

Characterization Of The Global Hawk Low Pressure Turbine First Rotor, Timothy L. Garmoe

Theses and Dissertations

The Air Force Research Laboratory, Propulsion Directorate at Wright Patterson Air Force Base has studied the performance of turbine blade geometries utilizing a large scale, low speed, drawdown wind tunnel in an effort to better understand gas turbine blade aerodynamics. Currently, the Air Force's Unmanned Aerial Vehicle (UAV) Global Hawk has been operated primarily at flight conditions other than the design point of its Allison AE3007H turbofan engine. This off design condition decreased the Reynolds number at the low pressure turbine causing losses in efficiency and loading. Two different blades were studied to maximize performance of the Global Hawk turbine. …

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Experimental Investigation Of A Lift Augmented Ground Effect Platform, Roberto T. Igue Sep 2005

Experimental Investigation Of A Lift Augmented Ground Effect Platform, Roberto T. Igue

Theses and Dissertations

This experimental study investigated the feasibility of applying the concept of a skirtless hovercraft into the production of an operational vehicle. A 0.255 m diameter prototype was designed, built and tested. An air bearing table was used as a testing platform, virtually eliminating the influence of friction and providing one degree of freedom for the experiments. Static tests were performed at various heights and craft configurations, providing a wide range of data for comparison. Lift, torque and efficiency were measured and calculated for each setting. Pressure and velocity information was also collected at specific points around the craft when operating …

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Investigation Of The Performance Characteristics Of Re-Entry Vehicles, Charles A. Bilbey Jr. Sep 2005

Investigation Of The Performance Characteristics Of Re-Entry Vehicles, Charles A. Bilbey Jr.

Theses and Dissertations

When a non-US spacecraft reenters the Earth's atmosphere, having the ability to accurately determine its performance characteristics is a primary concern. This study investigated the atmospheric re-entry profiles of a maneuverable re-entry vehicle. The re-entry vehicle was modeled as a point mass with aerodynamic properties. Equations of motion were numerically integrated, giving the time histories of position, velocity and flight path angle. The algorithm is able to generate a complete and feasible entry trajectory of a approximately 25-minute flight time in about 5 to 10 seconds on a desktop computer, given the entry conditions and values of constraint parameters. This …

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Modeling Adaptive Middleware And Its Applications To Military Tactical Datalinks, Jason T. Lawson Sep 2005

Modeling Adaptive Middleware And Its Applications To Military Tactical Datalinks, Jason T. Lawson

Theses and Dissertations

Open systems solutions and techniques have become the de facto standard for achieving interoperability between disparate, large-scale, legacy software systems. A key technology among open systems solutions and techniques is middleware. Middleware, in general, is used to isolate applications from dependencies introduced by hardware, operating systems, and other low-level aspects of system architectures. While middleware approaches are or will be integrated into operational military systems, many open questions exist about the appropriate areas to applying middleware. Adaptive middleware is middleware that provides an application with a run-time adaptation strategy, based upon system-level interfaces and properties. Adaptive middleware is an example …

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Protein Impregnated Polymer (Pip) Film Infrared Sensor Using Suspended Microelectromechanical Systems (Mems) Pixels, Tetsuo Kaieda Sep 2005

Protein Impregnated Polymer (Pip) Film Infrared Sensor Using Suspended Microelectromechanical Systems (Mems) Pixels, Tetsuo Kaieda

Theses and Dissertations

The Air Force Research Laboratory Materials and Manufacturing Directorate have developed a novel protein impregnated polymer (PIP) suspension that changes resistivity as a function of absorbed infrared radiation. Due to this property, the PIP is a potential material for use as an uncooled bolometer, or thermal sensor. In this research, a thermally-isolated pixel design, sensor characterization methods, and sensor fabrication and processing steps were developed. To create a microbolometer, the PIP was applied to two prototype micro-electro-mechanical systems (MEMS) surface micro-machined structures. The first is a raised cantilever pixel array that uses residual stress polysilicon and metal film arms to …

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A Flash Vaporization System For Detonation Of Hydrocarbon Fuels In A Pulse Detonation Engine, Kelly C. Tucker Jun 2005

A Flash Vaporization System For Detonation Of Hydrocarbon Fuels In A Pulse Detonation Engine, Kelly C. Tucker

Theses and Dissertations

Current research by the US Air Force and Navy is concentrating on obtaining detonations in a pulse detonation engine (PDE) with low vapor pressure, kerosene based jet fuels. These fuels have a low vapor pressure and the performance of a liquid hydrocarbon fueled PDE is significantly hindered by the presence of fuel droplets. A high pressure, fuel flash vaporization system (FVS) has been designed and built to reduce and eliminate the time required to evaporate the fuel droplets. Four fuels are tested: n-heptane, isooctane, aviation gasoline, and JP-8. The fuels vary in volatility and octane number and present a clear …

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Predicting The Cost Per Flying Hour For The F-16 Using Programmatic And Operational Variables, Eric M. Hawkes Jun 2005

Predicting The Cost Per Flying Hour For The F-16 Using Programmatic And Operational Variables, Eric M. Hawkes

Theses and Dissertations

This research analyzes operational and programmatic data from all Air National Guard and 13 of 14 active duty F-16C/D Fighter Wings (FW) from 1998 to 2004 in search of explanatory variables that influence a wing's Cost Per Flying Hour (CPFH). Using data from both the Air Force Total Ownership Cost database and from the Air Force Knowledge Systems database, this research evaluates the predictive ability of the following nine explanatory variables: aircraft age, average sortie duration, MajCOM, base location, utilization rate, percent engine type, percent block, percent deployed, and previous year's CPFH, the last four of which were previously untested. …

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An Investigation Of Starting Techniques For Inward Turning Inlets At Flight Speeds Below The On-Design Mach Number, John D. Mack Jun 2005

An Investigation Of Starting Techniques For Inward Turning Inlets At Flight Speeds Below The On-Design Mach Number, John D. Mack

Theses and Dissertations

The purpose of this study was to create and investigate starting techniques aimed at allowing complex, three-dimensional, inward-turning inlets to start by swallowing the shock wave associated with unstarted inlets. The techniques are rooted in supersonic diffuser theory and the Kantrowitz limit; they attempt to alleviate the over contraction that occurs in inward-turning inlets at flight speeds below the on-design Mach number. Five cases, three geometries at two flow conditions and the base non-modified inlet at the two flow conditions, were generated, and all were numerically simulated using a commercially produced numerical solver: CFD++. The simulations were computed using the …

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Categorizing High Energy Laser Effects For The Joint Munitions Effectiveness Manual, James A. Markham Jun 2005

Categorizing High Energy Laser Effects For The Joint Munitions Effectiveness Manual, James A. Markham

Theses and Dissertations

With the high risk and cost in fielding High Energy Laser (HEL) weapon systems, the development process must include computer simulation models of weapon system performance from the engineering level up to predicting the military worth of employing specific systems in a combat scenario. This research effort focuses on defining how to measure lethality for HEL weapons in an Advanced Tactical Laser (ATL) scenario. In order to create an effective measure for direct comparison between the emerging laser weapon system and existing conventionally delivered weapons, lase time in seconds is presented as a measure comparable to rounds required to cause …

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Boundary Layer Control Of A Circular Cylinder Using A Synthetic Jet, Christopher K. Smith Jun 2005

Boundary Layer Control Of A Circular Cylinder Using A Synthetic Jet, Christopher K. Smith

Theses and Dissertations

Active control of flow around a circular cylinder at a sub-critical Reynolds number was studied experimentally. The flow was controlled by using a synthetic jet which ran span wise along the cylinder and emanated radially from the cylinder. The experiments were conducted over a two dimensional cylinder in a water tunnel at a Reynolds number of approximately 5800. Seven different jet locations and seven different jet oscillation frequencies were examined. Particle image velocimetry (PIV) was used for flow visualization. The synthetic jet proved to delay flow separation at a wide range of locations and oscillation frequencies. The greatest positive effect …

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Cost Comparison Of Existing Coatings For A Hypervelocity Test Rail, Mark A. Blomer Jun 2005

Cost Comparison Of Existing Coatings For A Hypervelocity Test Rail, Mark A. Blomer

Theses and Dissertations

This study compared the relative costs, to the Department of Defense, of two different coatings used to protect a high speed test rail. Each coating was compared to the case of an uncoated rail with test conditions that caused catastrophic failure just after the test sled reached its maximum velocity. The total cost was finalized on a per test basis in order to sum cost of various expenditures that may only happen once every few tests. To compare the protective properties of each coating, various coated and uncoated samples were tested via a cylinder specimen Taylor Impact Test. Each coating's …

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Drag Estimates For The Joined-Wing Sensor Craft, Ryan L. Craft Jun 2005

Drag Estimates For The Joined-Wing Sensor Craft, Ryan L. Craft

Theses and Dissertations

This research studied the drag effects of the joined-wing sensor craft technology demonstrator being developed at the Air Force Research Laboratory (AFRL). Although many performance parameters have been studied and evaluated for this vehicle, to date no detailed drag estimates have been conducted for the AFRL configuration. Previous performance parameters of the aircraft have been estimated based solely on a constant lift-to-drag ratio assumption. Using the Air Vehicles Technology Integration Environment created by Dr. Maxwell Blair, and supplemented by MATLAB code, this study explored three different drag prediction methods to determine accurate estimates of both parasite and induced drag. The …

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Mechanical Behavior Of Cracked Panels Repaired With Bonded Composite Patch, Michael A. Hansen Jun 2005

Mechanical Behavior Of Cracked Panels Repaired With Bonded Composite Patch, Michael A. Hansen

Theses and Dissertations

This research focuses on investigating the mechanical behavior of cracked aluminum panels repaired with bonded boron/epoxy composite patches. The effects of crack initiation and growth on the residual strength of the repaired panels are characterized. This research establishes a correlation between damage modes, residual strength and evolution of strain within as well as outside the patch. Monotonic tensile tests on specimens with a perfectly bonded patch were used to determine the base line strength. Likewise, fatigue tests on specimens with a perfectly bonded patch served to establish baseline fatigue life. In addition, several specimens with a perfectly bonded patch were …

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Study Of Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Erik K. Ross Jun 2005

Study Of Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Erik K. Ross

Theses and Dissertations

The research project studied the benefits of Magnetogasdynamic (MGD) acceleration on a scramjet nozzle. MGD is a technology that relies on electromagnetic fields to extract and/or add energy to flow fields. The scramjet engine in the "AJAX" concept proposed by D.I. Brichkii et al. (2001) of St. Petersburg, Russia would utilize an MGD power generator in the diffuser user which could potentially provide electrical power for the aircraft support systems and an MGD accelerator in the nozzle of the engine. Using an AFRL/VAAC CFD code that was modified for MGD computations, this project investigated the effect conductivity and load factor …

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