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Air Force Institute of Technology

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Time Resolved Filtered Rayleigh Scattering Measurement Of A Centrifugally Loaded Buoyant Jet, Firas Benhassen Mar 2011

Time Resolved Filtered Rayleigh Scattering Measurement Of A Centrifugally Loaded Buoyant Jet, Firas Benhassen

Theses and Dissertations

The combustion process within the Ultra-Compact Combustor (UCC) occurs in the circumferential direction. The presence of variable flow density within the circumferential cavity introduces significant buoyancy issues. On the other hand, G-loading caused by the presence of centrifugal forces, ensures the circulation of the flow in the circumferential cavity and enhances the completion of the combustion process before allowing the exit of the hot gases to the main flow. The coupling between buoyancy and high G-loading is what predominately influences the behavior of the flow within the UCC. In order to better understand the combustion process within the UCC, three …

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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 …

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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 …

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Radial Distribution Of Absorption In A Cesium Heat Pipe With Axial Laser Heating, Charles D. Fox Mar 2011

Radial Distribution Of Absorption In A Cesium Heat Pipe With Axial Laser Heating, Charles D. Fox

Theses and Dissertations

Diode Pumped Alkali Lasers (DPAL) have been scaled to greater than 100 W and exhibit slope efficiencies exceeding 80%, offering application for tactical laser weapons. The hybrid DPAL system combines efficient diode pumping with the good beam quality and thermal characteristics of gas lasers. Thermal effects on alkali concentration have been observed to degrade performance, while low speed flowing systems are in development. However, spatial gradients in temperature and concentrations have not previously been observed. In the present work, a 0.8 W/cm2 pump laser at the D1 frequency heats the medium in a T=50-100 °C cesium heat pipe …

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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. …

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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 …

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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 …

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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, …

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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, …

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Optimization Of Hybrid-Electric Propulsion Systems For Small Remotely-Piloted Aircraft, Todd A. Rotramel Mar 2011

Optimization Of Hybrid-Electric Propulsion Systems For Small Remotely-Piloted Aircraft, Todd A. Rotramel

Theses and Dissertations

Small electric-powered remotely-piloted aircraft (RPA) used by today's warfighters for intelligence, surveillance, and reconnaissance (ISR) missions lack desired endurance and loiter times, while the acoustics and thermal signatures of those configured with internal combustion engines (ICE) may make them unpractical for ISR. Outfitting RPA with parallel hybrid-electric propulsion systems (H-EPS) would meet the military's needs by combining the advantages of both systems while reducing fuel consumption and environmental impacts. An analysis tool was created, using constrained static optimization, to size the H-EPS components. Based on the RPA's required power and velocity for the endurance phase, an electric motor (EM) can …

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Improved Collision Modeling For Direct Simulation Monte Carlo Methods, Sarah E. Summers Mar 2011

Improved Collision Modeling For Direct Simulation Monte Carlo Methods, Sarah E. Summers

Theses and Dissertations

In the Smoothed Accept/Reject (SAR) algorithm, the accept/reject criteria is altered from Direct Simulation Monte Carlo (DSMC): rather than a binary function of rejection or acceptance, collisions can be partially accepted with a linear weighting between zero and one. The partial acceptance is based on a band around the original accept/reject criteria defined as a percentage of the collision criteria, which is called ε. A relationship previously noted between Mach and ε is explored. Velocity distributions of the particles are examined for all algorithms and compared to experimental data to determine the effect of the SAR algorithm at a microscopic …

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Biological Investigation Of The Stimulated Flapping Motions Of The Moth, Manduca Sexta, Travis B. Tubbs Mar 2011

Biological Investigation Of The Stimulated Flapping Motions Of The Moth, Manduca Sexta, Travis B. Tubbs

Theses and Dissertations

No abstract provided.

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Perimeter Security And Intruder Detection Using Gravity Gradiometry: A Feasibility Study, Jared D. Tuinstra Mar 2011

Perimeter Security And Intruder Detection Using Gravity Gradiometry: A Feasibility Study, Jared D. Tuinstra

Theses and Dissertations

Changes in the mass distribution around some point on the Earth’s surface induce corresponding changes to the magnitude and direction of the gravity vector at that location. The nine-tensor derivative of the gravity vector, or gravity gradient, is sensitive to very small changes in the gravity vector. With some assumptions, continuous measurement of the gravity gradient using a gravity gradiometer (GGI) is used to determine the location of a mass change in the local area near the instrument. This investigation sought to determine the effectiveness, operating characteristics, and limitations of a physical perimeter security system that uses an array of …

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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 …

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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 …

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Software And Critical Technology Protection Against Side Channel Analysis Through Dynamic Hardware Obfuscation, John R. Bochert Mar 2011

Software And Critical Technology Protection Against Side Channel Analysis Through Dynamic Hardware Obfuscation, John R. Bochert

Theses and Dissertations

Side Channel Analysis (SCA) is a method by which an adversary can gather information about a processor by examining the activity being done on a microchip though the environment surrounding the chip. Side Channel Analysis attacks use SCA to attack a microcontroller when it is processing cryptographic code, and can allow an attacker to gain secret information, like a crypto-algorithm's key. The purpose of this thesis is to test proposed dynamic hardware methods to increase the hardware security of a microprocessor such that the software code being run on the microprocessor can be made more secure without having to change …

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Direction Finding With Mutually Orthogonal Antennas, David F. Chick Mar 2011

Direction Finding With Mutually Orthogonal Antennas, David F. Chick

Theses and Dissertations

Estimating the direction-of-arrival of incident electromagnetic plane waves (a.k.a. direction finding or DF) has typically been accomplished in the past using arrays of spatially separated antennas. The spatial separation produces a delay in each antenna's measured voltage due to the finite propagation time as the wave strikes each antenna in succession. In this thesis, we approach the problem differently by using three antennas that have been oriented in orthogonal directions but are co-located at the origin of a coordinate system. Being co-located, this mutually orthogonal arrangement of antennas cannot detect the propagation phase delay and must rely solely on the …

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Overcoming Pose Limitations Of A Skin-Cued Histograms Of Oriented Gradients Dismount Detector Through Contextual Use Of Skin Islands And Multiple Support Vector Machines, Jonathon R. Climer Mar 2011

Overcoming Pose Limitations Of A Skin-Cued Histograms Of Oriented Gradients Dismount Detector Through Contextual Use Of Skin Islands And Multiple Support Vector Machines, Jonathon R. Climer

Theses and Dissertations

This thesis provides a novel visualization method to analyze the impact that articulations in dismount pose and camera aspect angle have on histograms of oriented gradients (HOG) features and eventual detections. Insights from these relationships are used to identify limitations in a state of the art skin cued HOG dismount detector's ability to detect poses not in a standard upright stances. Improvements to detector performance are made by further leveraging available skin information, reducing false detections by an additional order of magnitude. In addition, a method is outlined for training supplemental support vector machines (SVMs) from computer generated data, for …

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Development Of An Interference Lithography Capability Using A Helium Cadmium Ultraviolet Multimode Laser For The Fabrication Of Sub-Micron-Structured Optical Materials, Stanley D. Crozier Mar 2011

Development Of An Interference Lithography Capability Using A Helium Cadmium Ultraviolet Multimode Laser For The Fabrication Of Sub-Micron-Structured Optical Materials, Stanley D. Crozier

Theses and Dissertations

The goal of this work is to develop unique holograms on a semiconductor-metal thin films to characterize as potential metamaterials. This is achievable by developing a fabrication recipe to include exposure methods, exposure dosages, and material development. This study developed an interference lithography capability at AFIT for the first time with period resolution below 230nm. It also identified initial acceptable photoresist materials and exposure dosages, and a path to follow to optimize this process. The potential impact of this is to make IL a standard in optical meta-material fabrication, which decreases manufacturing time and allows for less error in production. …

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Simulating The Effects Of An Extended Source On The Shack-Hartmann Wavefront Sensor Through Turbulence, Jeffery S. Dennison Mar 2011

Simulating The Effects Of An Extended Source On The Shack-Hartmann Wavefront Sensor Through Turbulence, Jeffery S. Dennison

Theses and Dissertations

Perspective elongation in Shack-Hartmann wavefront sensor (SHWFS) spots is a phenomenon caused by an extended three-dimensional scattering beacon in the mesosphere (80-100km). Elongated spots cause errors in wavefront sensor measurements, which leads to poor turbulence compensation and decreased image resolution of the optical system. In order to compensate for elongated spots, a proper beacon model must be developed to simulate the error. In this paper, a documented theory for modeling an elongated sodium beacon and elongated SHWFS spots using sodium layer slices was tested. It was found that nine evenly-spaced slices were adequate to model the elongated beacon in the …

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Shack-Hartmann And Interferometric Hybrid Wavefront Sensor, Troy R. Ellis Mar 2011

Shack-Hartmann And Interferometric Hybrid Wavefront Sensor, Troy R. Ellis

Theses and Dissertations

This document reports results of wave-optics simulations used to test the performance of a hybrid wavefront sensor designed to combine the self-referencing interferometer and Shack-Hartmann wavefront sensors in an optimal way. Optimal hybrid-wavefront sensor design required a thorough analysis of the noise characteristics of each wavefront sensor to produce noise models that assist in the design of an optimal phase-estimation algorithm. Feasible architectures and algorithms for combining wavefront sensors were chosen, and the noise models of the individual wavefront sensors were combined to form a model for the noise-induced error of the resulting hybrid sensor. The hybrid wavefront sensor and …

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Three Channel Polarimetric Based Data Deconvolution, Kurtis G. Engelson Mar 2011

Three Channel Polarimetric Based Data Deconvolution, Kurtis G. Engelson

Theses and Dissertations

A three channel polarimetric deconvolution algorithm was developed to mitigate the degrading effects of atmospheric turbulence in astronomical imagery. Tests were executed using both simulation and laboratory data. The resulting efficacy of the three channel algorithm was compared to a recently developed two channel approach under identical conditions ensuring a fair comparison amongst both algorithms. Two types of simulations were performed. The first was a binary star simulation to compare resulting resolutions between the three and two channel algorithms. The second simulation measured how effective both algorithms could deconvolve a blurred satellite image. The simulation environment assumed the key parameters …

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Dynamic Polymorphic Reconfiguration To Effectively “Cloak” A Circuit’S Function, Jeffrey L. Falkinburg Mar 2011

Dynamic Polymorphic Reconfiguration To Effectively “Cloak” A Circuit’S Function, Jeffrey L. Falkinburg

Theses and Dissertations

Today's society has become more dependent on the integrity and protection of digital information used in daily transactions resulting in an ever increasing need for information security. Additionally, the need for faster and more secure cryptographic algorithms to provide this information security has become paramount. Hardware implementations of cryptographic algorithms provide the necessary increase in throughput, but at a cost of leaking critical information. Side Channel Analysis (SCA) attacks allow an attacker to exploit the regular and predictable power signatures leaked by cryptographic functions used in algorithms such as RSA. In this research the focus on a means to counteract …

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A Statistical Approach To Fusing 2-D And 3-D Ladar Systems, Paul F. Dolce Mar 2011

A Statistical Approach To Fusing 2-D And 3-D Ladar Systems, Paul F. Dolce

Theses and Dissertations

LADAR (LAser Detection and Ranging) systems can be used to provide 2-D and 3-D images of scenes. Generally, 2-D images possess superior spatial resolution but without range data due to the density of their focal plane arrays. A 3-D LADAR system can produce range to target data at each pixel, but lacks the 2-D system's superior spatial resolution. The 3-D system is limited by its hardware, specifically its imaging array. Currently developers are investigating ways to change the pixel size in the 3-D LADAR imaging array, but the costs of this research is quite expensive and technically robust. It is …

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Evaluation Of The Single Keybit Template Attack, Eric W. Garcia Mar 2011

Evaluation Of The Single Keybit Template Attack, Eric W. Garcia

Theses and Dissertations

Side Channel leakage is a serious threat to secure devices. Cryptographic information extraction is possible after examining any one of the various side channels, including electromagnetic. This work contributes a new method to achieve such a purpose. The Single Keybit Template Attack (SKTA) is introduced as a means to extract encryption keys from embedded processors and other integrated circuit devices performing DES encryptions by passively monitoring and exploiting unintentional RF emissions. Key extraction is accomplished by creating two templates for each bit value of the key based on instantaneous amplitude responses as a device executes DES operations. The resultant templates …

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A Multi Agent System For Flow-Based Intrusion Detection Using Reputation And Evolutionary Computation, David Hancock Mar 2011

A Multi Agent System For Flow-Based Intrusion Detection Using Reputation And Evolutionary Computation, David Hancock

Theses and Dissertations

The rising sophistication of cyber threats as well as the improvement of physical computer network properties present increasing challenges to contemporary Intrusion Detection (ID) techniques. To respond to these challenges, a multi agent system (MAS) coupled with flow-based ID techniques may effectively complement traditional ID systems. This paper develops: 1) a scalable software architecture for a new, self-organized, multi agent, flow-based ID system; and 2) a network simulation environment suitable for evaluating implementations of this MAS architecture and for other research purposes. Self-organization is achieved via 1) a reputation system that influences agent mobility in the search for effective vantage …

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Adaptive Quality Of Service Engine With Dynamic Queue Control, James D. Haught Mar 2011

Adaptive Quality Of Service Engine With Dynamic Queue Control, James D. Haught

Theses and Dissertations

While the current routing and congestion control algorithms in use today are often sufficient for networks with relatively static topology, these algorithms may not be sufficient for military networks where a certain level of quality of service (QoS) needs to be achieved to complete a mission. Current networking technology limits a network's ability to adapt to changes and interactions in the network, often resulting in sub-optimal performance. This research investigates the use of queue size predictions to create a network controller to optimize computer networks. These queue size predictions are made possible through the use of Kalman filters to detect …

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Malicious And Malfunctioning Node Detection Via Observed Physical Layer Data, Tyler J. Hardy Mar 2011

Malicious And Malfunctioning Node Detection Via Observed Physical Layer Data, Tyler J. Hardy

Theses and Dissertations

There are many mechanisms that can cause inadequate or unreliable information in sensor networks. A user of the network might be interested in detecting and classifying specific sensors nodes causing these problems. Several network layer based trust methods have been developed in previous research to assess these issues; in contrast this work develops a trust protocol based on observations of physical layer data collected by the sensors. Observations of physical layer data are used for decisions and calculations, and are based on just the measurements collected by the sensors. Although this information is packaged and distributed on the network layer, …

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Image Dependent Relative Formation Navigation For Autonomous Aerial Refueling, James M. Howard Mar 2011

Image Dependent Relative Formation Navigation For Autonomous Aerial Refueling, James M. Howard

Theses and Dissertations

This research tests the feasibility, accuracy, and reliability of a predictive rendering and holistic comparison algorithm with use of an optical sensor to provide relative distance and position behind a lead or tanker aircraft. Using an accurate model of a tanker, an algorithm renders image(s) for comparison with actual collected images by a camera installed on the receiver aircraft. Based on this comparison, information used to create the rendered image(s) is used to provide the relative navigation solution required for autonomous air refueling. Given enough predicted images and processing time, this approach should reliably find an accurate solution. Building on …

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Holistic Network Defense: Fusing Host And Network Features For Attack Classification, Jenny W. Ji Mar 2011

Holistic Network Defense: Fusing Host And Network Features For Attack Classification, Jenny W. Ji

Theses and Dissertations

This work presents a hybrid network-host monitoring strategy, which fuses data from both the network and the host to recognize malware infections. This work focuses on three categories: Normal, Scanning, and Infected. The network-host sensor fusion is accomplished by extracting 248 features from network traffic using the Fullstats Network Feature generator and from the host using text mining, looking at the frequency of the 500 most common strings and analyzing them as word vectors. Improvements to detection performance are made by synergistically fusing network features obtained from IP packet flows and host features, obtained from text mining port, processor, logon …

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