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Investigation Of The Effects Of Target Feature Variations On Ballistic Missile Rcs, Sang H. Lee
Investigation Of The Effects Of Target Feature Variations On Ballistic Missile Rcs, Sang H. Lee
Theses and Dissertations
Uncertainties about certain features of target geometries can result in a loss of confidence in target signature assessment. This thesis describes the development of a general "rule-of-thumb" to determine how the radar signature of a target varies as a function of the target's specific features. The targets of interest in this study are fictitious ballistic missiles. Four target features of these missiles are investigated: fin size, nose cone shape, panel riveting along the sides of the missile, and heat shielding on the nose cone. By varying these target features in different missile configurations, and comparing them to each other, a …
Active Optical Tracking With Spatial Light Modulators, Steven R. Mawhorter
Active Optical Tracking With Spatial Light Modulators, Steven R. Mawhorter
Theses and Dissertations
Two spatial light modulators are utilized for beam splitting, steering and tracking. Both linear and holographic phase screens are used in a demonstration of technology to allow real time tracking to communicate in a one-to-several type scenario. One SLM is used to apply a linear phase modulation to steer multiple beams onto a detector. The spots that are produced represent the targets as they move around the field of view of the central communication node. A Gerchberg-Saxton algorithm will subsequently use the detected spots as the desired pointing locations. Using this as input, the Gerchberg-Saxton algorithm yields a phase only …
Estimation And Mitigation Of Unmodeled Errors For A Pseudolite Based Reference System, Jeremiah A. Shockley
Estimation And Mitigation Of Unmodeled Errors For A Pseudolite Based Reference System, Jeremiah A. Shockley
Theses and Dissertations
Current flight reference systems rely heavily on the Global Positioning System (GPS), causing susceptibility to GPS jamming. Additionally, an increasing number of tests involve jamming the GPS signal. A need exists to develop a system capable of GPS-level accuracy during these outages. One promising solution is a ground-based pseudolite system capable of delivering sub-centimeter level accuracy, yet operating at non-GPS frequencies. This thesis attempts to determine the unknown errors in the Locata system, one such pseudolite-based system, to achieve the accuracy required. The development of a measurement simulation tool along with a Kalman filter algorithm provides confirmation of filter performance …
Characterization And Design Of High-Level Vhdl I/Q Frequency Downconverter Via Special Sampling Scheme, Jesse P. Somann
Characterization And Design Of High-Level Vhdl I/Q Frequency Downconverter Via Special Sampling Scheme, Jesse P. Somann
Theses and Dissertations
This study explores the characterization and implementation of a Special Sampling Scheme (SSS) for In-Phase and Quad-Phase (I/Q) down conversion utilizing top-level, portable design strategies. The SSS is an under-developed signal sampling methodology that can be used with military and industry receiver systems, specifically, United States Air Force (USAF) video receiver systems. The SSS processes a digital input signal-stream sampled at a specified sampling frequency, and down converts it into In-Phase (I) and Quad-Phase (Q) output signal-streams. Using the theory and application of the SSS, there are three main objectives that will be accomplished: characterization of the effects of input, …
Application Of Fuzzy State Aggregation And Policy Hill Climbing To Multi-Agent Systems In Stochastic Environments, Dean C. Wardell
Application Of Fuzzy State Aggregation And Policy Hill Climbing To Multi-Agent Systems In Stochastic Environments, Dean C. Wardell
Theses and Dissertations
Reinforcement learning is one of the more attractive machine learning technologies, due to its unsupervised learning structure and ability to continually even as the operating environment changes. Applying this learning to multiple cooperative software agents (a multi-agent system) not only allows each individual agent to learn from its own experience, but also opens up the opportunity for the individual agents to learn from the other agents in the system, thus accelerating the rate of learning. This research presents the novel use of fuzzy state aggregation, as the means of function approximation, combined with the policy hill climbing methods of Win …
Bio-Inspired, Odor-Based Navigation, Maynard John Porter Iii
Bio-Inspired, Odor-Based Navigation, Maynard John Porter Iii
Theses and Dissertations
The ability of moths to locate a member of the opposite sex, by tracking a wind-borne plume of odor molecules, is an amazing reality. Numerous scenarios exist where having this capability embedded into ground-based or aerial vehicles would be invaluable. The main crux of this thesis investigation is the development of a navigation algorithm which gives a UAV the ability to track a chemical plume to its source. Inspiration from the male moth's, in particular Manduca sexta, ability to successfully track a female's pheromone plume was used in the design of both 2-D and 3-D navigation algorithms. The algorithms were …
An Airborne Radar Model For Non-Uniformly Spaced Antenna Arrays, Matthew V. Young
An Airborne Radar Model For Non-Uniformly Spaced Antenna Arrays, Matthew V. Young
Theses and Dissertations
This thesis presents an airborne radar model for non-uniformly spaced antenna arrays. Non-uniform arrays potentially possess advantages unobtainable by uniformly spaced arrays. An element position matrix is defined to accommodate arbitrary element locations. The new element position matrix affects the time/phase delay to each element, spatial frequencies, steering vectors, space-time snapshots, and covariance matrices. The joint domain localized and factored time-space-time adaptive processing algorithms are also updated so they are compatible with the new model. The non-uniformly spaced array radar model is verified with previous models presented by Jaffer, Ward, and Hale. The model for non-uniform arrays is used to …
Verification Of A Decision Level Fusion Algorithm Using A Proven Atr System And Measured Sar Data, James Douglas Thompson
Verification Of A Decision Level Fusion Algorithm Using A Proven Atr System And Measured Sar Data, James Douglas Thompson
Theses and Dissertations
Decision level fusion (DLF) algorithms combine outputs of multiple single sensors to make one confident declaration of a target. This research compares performance results of a DLF algorithm using measured data and a proven ATR system with results from simulated data and a modeled ATR system. This comparison indicates that DLF offers significant performance improvements over single sensor looks. However, results based on simulated data and a modeled ATR are slightly optimistic and overestimate results from measured data and a proven ATR system by nearly 10% over all targets tested.
Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland
Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland
Theses and Dissertations
Dynamic stability and stall during steady level turns were examined for VA-1, a joined-wing flight demonstrator aircraft. Configurations with a lower vertical tail and fairings over the main landing gear were compared with a recommendation on the combination had the best drag and dynamic stability characteristics. The dynamic stability analysis was broken into four key parts: a twist test experimentally measured mass moments of inertia, a panel method was used to find non-dimensional stability derivatives, lateral and longitudinal state space models estimated dynamic stability characteristics and handling quality levels were evaluated using a Cooper-Harper based rating system. VA-1 was found …
The Effects Of Using Solar Radiation Pressure To Alleviate Fuel Requirements For Orbit Changing And Maintenance Of The Dscs Ii F-13 Satellite, Jody A. Paris
Theses and Dissertations
Orbit disposal and maintenance of aging satellites has become a significant concern over the past few years, as the increasing number of orbiting objects threatens to limit the launching of future satellites. Many of the satellites currently in orbit, however, were not built with disposal considerations. The DSCS II series was launched into orbit beginning in the 1970s, and many satellites are now without the fuel required to conventionally transition to a sanctioned disposal orbit. In GEO orbit the largest non-gravitational perturbation is solar radiation pressure. By adjusting the attitude of a satellite with a controller to maximize the perturbing …
A Systems Engineering Approach To Integrated Structural Health Monitoring For Aging Aircraft, Alan P. Albert, Efstathios Antoniou, Stephen D. Leggiero, Kimberly A. Tooman, Ramon L. Veglio
A Systems Engineering Approach To Integrated Structural Health Monitoring For Aging Aircraft, Alan P. Albert, Efstathios Antoniou, Stephen D. Leggiero, Kimberly A. Tooman, Ramon L. Veglio
Theses and Dissertations
The United States Air Force and many of its Coalition partners have extended the original service life of some of their aging aircraft due to fiscal constraints. This life extension often requires increased periodic and in-depth inspections; increasing maintenance costs and resulting in longer periods of aircraft downtime. A structural health monitoring system for aging aircraft could reduce the current inspection burden, and thus decrease costs and system downtime. This presentation describes a baseline systems engineering methodology for system definition of an aging aircraft structural health monitoring system. Analysis was performed to quantify the potential benefit a structural health monitoring …
Cost Comparison Of Expendable, Hybrid And Reusable Launch Vehicles, Greg J. Gstattenbauer
Cost Comparison Of Expendable, Hybrid And Reusable Launch Vehicles, Greg J. Gstattenbauer
Theses and Dissertations
This study compares the developmental, production, and maintenance costs (DPM) of twostage- to-orbit (TSTO) expendable (ELV), hybrid (HLV), and reusable (RLV) launch systems. This comparison was accomplished using top level mass and cost estimating relations (MERs, CERs). Mass estimating relationships were correlated to existing launch system data and ongoing launch system studies. Cost estimating relations were derived from Dr. Dietrich Koelle's 'Handbook of Cost Engineering for Space Transportation Systems'. Hybrid launch vehicles appear to be preferable if current or modest increases in launch rates are projected while reusable launch vehicles appear preferable for large projected increases in launch rates.
Covariance Estimation And Autocorrelation Of Norad Two-Line Element Sets, Victor P. Osweiler
Covariance Estimation And Autocorrelation Of Norad Two-Line Element Sets, Victor P. Osweiler
Theses and Dissertations
This thesis investigates NORAD two-line element sets (TLE) containing satellite mean orbital elements for the purpose of estimating a covariance matrix and formulating an autocorrelation relationship. Orbit propagation is performed using Simplified General Perturbations Number 4 (SGP4) analytical model as implemented within Satellite Took Kit. For a given satellite, TLEs from a span of two weeks are used to calculate position and velocity differences of estimated state vectors in order to characterize their variance behavior and compute a covariance matrix for the most recent TLE. Six satellites and eight time spans are investigated, with all state vector differences evaluated in …
Control Demonstration Of A Thin Deformable In-Plane Actuated Mirror, Gina A. Peterson
Control Demonstration Of A Thin Deformable In-Plane Actuated Mirror, Gina A. Peterson
Theses and Dissertations
Current imaging satellites are limited in resolution and coverage area by the aperture size of their primary optical mirror. To get a large optical mirror into space, current launch weight and size restrictions must be overcome. Membrane-like optical mirrors can overcome these restrictions with their very lightweight and flexible properties. However, thin, deformable membrane mirrors are very susceptible to the space environment and require active control for surface stabilization and shaping. The primary goal of this research is to demonstrate that an in-plane actuated membrane-like deformable optical mirror can be controlled to optical wavelength tolerances in a closed-loop system. Fabrication …
Characterizing And Controlling The Effects Of Differential Drag On Satellite Formations, James T. Wedekind
Characterizing And Controlling The Effects Of Differential Drag On Satellite Formations, James T. Wedekind
Theses and Dissertations
The ability to fly satellites in close formations represents a capability that could revolutionize the way satellite missions are designed in the future. This study examines three of the primary formation flying designs and characterizes the effects that an anomalous satellite with a slightly different cross-sectional area would have on the stability of the formation. Following the characterization of these effects, a controller is implemented to mitigate the cross-sectional area differences between the satellites. The results show that, with the addition of a straightforward controller, small cross-sectional area differences can be mitigated and corrected such that the satellites will remain …
Aerodynamic Loss And Mixing Over A Cavity Flame Holder Located Downstream Of Pylon-Aided Fuel Injection, Lane C. Haubelt
Aerodynamic Loss And Mixing Over A Cavity Flame Holder Located Downstream Of Pylon-Aided Fuel Injection, Lane C. Haubelt
Theses and Dissertations
Cavity-based fuel injection and flame holding found in hydrocarbon-fueled scramjet applications are of interest. The Air Force Research Lab (AFRL) and the Air Force Institute of Technology (AFIT) at Wright-Patterson Air Force Base in Ohio are investigating the enhancement of fuel-air mixing with small pylons that project into the supersonic flow upstream of a flame holder cavity. This follows previous qualitative (Mie scattering and NO-PLIF visualizations) results which suggested that injection behind pylons, may improve fuel-air mixing. Three pylons geometries (medium, tall, and wide) shaped as thin triangular wedges with a 30o inclination angle were tested and compared to baseline …
Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson
Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson
Theses and Dissertations
Often turbomachinery airfoils are designed with aerodynamic performance foremost in mind rather than component durability. However, future aircraft systems require ever increasing levels of gas-turbine inlet temperature causing the durability and reliability of turbine components to be an ever more important design concern. As a result, the need to provide improved heat transfer prediction and optimization methods presents itself. Here, an effort to design an airfoil with minimized heat load is reported. First, a Reynolds-Averaged Navier-Stokes (RANS) flow solver was validated over different flow regimes as well as varying boundary conditions against extensive data available in literature published by the …
Structural Design Of Wing Twist For Pitch Control Of Joined Wing Sensor Craft, Fred A. Kimler Iii
Structural Design Of Wing Twist For Pitch Control Of Joined Wing Sensor Craft, Fred A. Kimler Iii
Theses and Dissertations
This research investigated two aspects of the aft wing structure of a joined wing SensorCraft. First, the efficacy of a novel approach for incorporating wing twist for pitch control was analyzed. This design involved adding a spanwise sliding joint into the wing structure at the lower aft spar of the vehicle's aft wing. Second, the joint section where the forward and aft wings connect and form the outboard wing was redesigned and analyzed to improve the load transmission between the wing spars. Using MSC.NASTRAN, linear and non-linear static analyses were performed to examine the efficiency of the wing twist sliding …
A Comparison Of Main Rotor Smoothing Adjustments Using Linear And Neural Network Algorithms, Nathan A. Miller
A Comparison Of Main Rotor Smoothing Adjustments Using Linear And Neural Network Algorithms, Nathan A. Miller
Theses and Dissertations
Helicopter main rotor smoothing is a maintenance procedure that is routinely performed to minimize airframe vibrations induced by non-uniform mass and/or aerodynamic distributions in the main rotor system. This important task is both time consuming and expensive, so improvements to the process have long been sought. Traditionally, vibrations have been minimized by calculating adjustments based on an assumed linear relationship between adjustments and vibration response. In recent years, artificial neural networks have been trained to recognize non-linear mappings between adjustments and vibration response. This research was conducted in order observe the character of the adjustment mapping of the Vibration Management …
Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern
Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern
Theses and Dissertations
Buffet-induced vibration has been problematic for aircraft structures for many years. The F-16 ventral fin, while prone to these effects, lends itself well to the evaluation of modern active structural and flow control technologies. The objective of this research was to determine the most critical natural modes of vibration for the F-16 ventral fin and design piezoelectric actuators capable of reducing buffet-induced ventral fin vibration. A finite element model (FEM) for the fin was developed, tuned and optimized to closely match published modal frequencies. Piezoelectric actuator patches were designed using the strain characteristics of the FEM and integrated into the …
Validation Of A Scaled Plane Strain Hypervelocity Gouging Model, Ronald J. Pendleton
Validation Of A Scaled Plane Strain Hypervelocity Gouging Model, Ronald J. Pendleton
Theses and Dissertations
The phenomenon of high speed impact is of great interest to the Air Force of Scientific Research and the Air Force Research Laboratory's Holloman High Speed test track. Rocket sled tests at the facility frequently are limited to velocities lower than actually attainable due to damage to the rail in the form of gouges. Direct observation of the gouging phenomenon is not currently possible. This leaves computational modeling as the only means to study the phenomenon. A computer model has previously been used to model the development of gouging at the Holloman High Speed Test Track. However, this model has …
Store Separations From A Supersonic Cone, Richard J. Simko
Store Separations From A Supersonic Cone, Richard J. Simko
Theses and Dissertations
The purpose of this research was to analyze the environment a store would travel through if ejected from a supersonic cone. This was done using the Beggar Computational Fluid Dynamics (CFD) code from the Air Force SEEK Eagle Office at Eglin Air Force Base, FL. CFD simulations were compared to experimental results from a previous AFIT thesis and conclusions were drawn based on whether or not the current wind tunnel setup at AFIT is capable of performing analyses of supersonic store separations. Also included in this research is a study of supersonic base pressure profiles, near-wake velocity profiles, wind tunnel …
Comparison Of Variance-To-Mean Ratio Methods For Repairables Inventory Management, Lisa J. Mahon
Comparison Of Variance-To-Mean Ratio Methods For Repairables Inventory Management, Lisa J. Mahon
Theses and Dissertations
In an effort to improve aircraft availability, this research compared the efficiency of ten methods of determining variance-to-mean ratios (VTMRs, VMRs, V/Ms) for repairable, spare aircraft parts known as repairables. These methods are base pipeline quantity, Hill-Stevens (220 LRUs), a variation of Hill-Stevens (10 1s), Hill-Stevens (230 LRUs), the Sherbrooke, a variation of Sherbrooke (10 1s), historical data, a new regression function, variance-to-mean ratio equals 1.00 or variance-to-mean ratio equals 1.01. Using VTMRs derived from quarterly organizational intermediate maintenance (OIM) demands for line-replaceable units (LRUs) from the D200A Secondary Item Requirement System (SIRS) databases in aircraft sustainability model scenarios and …
Comparison Of Ray Tracing Through Ionospheric Models, Shayne C. Aune
Comparison Of Ray Tracing Through Ionospheric Models, Shayne C. Aune
Theses and Dissertations
A comparison of ray tracing predictions for transionospheric electromagnetic wave refraction and group delays through ionospheric models is presented. Impacted applications include over-the-horizon RADAR, high frequency communications, direction finding, and satellite communications. The ionospheric models used are version 2.1 of Utah State University's Global Assimilation of Ionospheric Measurements (USU GAIM) model and the 2001 version of the International Reference Ionosphere (IRI) model. In order to provide ray tracing results applicable to satellite communications for satellites at geosynchronous orbit (GEO), a third ionospheric model is used to extend the sub-2000-km USU GAIM and IRI ionospheric specifications to 36540 km in altitude. …
Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt
Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt
Theses and Dissertations
There are many situations in which GPS is either unable to provide the desired level of accuracy or is unavailable. Use of a pseudolite-based reference system for navigation can be a means for positioning during these times. While there are advantages in using a pseudolite-based reference system, there are still implementation issues and deficiencies that must be addressed. In many cases, a pseudolite system with ground-based transmitters has difficulty determining the height of the receiver accurately. This is due to the poor vertical observability inherent in the geometry of the system. A common approach in naval applications for solving the …
Free Flight Store Simulation Using Beggar, Judson T. Babcock
Free Flight Store Simulation Using Beggar, Judson T. Babcock
Theses and Dissertations
The complete numerical solution of the airflow around a store in extended free flight is of particular importance to the United States Air Force. Beggar is the primary Computational Fluid Dynamics (CFD) program used by the USAF to obtain solutions for store separations. However, Beggar's ability to simulate a store in free flight is limited because the store must fall through a static background mesh, eventually reaching a point where the solution will fail. The length of any free flight simulation is consequently limited by the height of the background mesh. Code modifications are made to Beggar to remove this …
The Simulation Of Off-Axis Laser Propagation Using Heleeos, Scott L. Belton
The Simulation Of Off-Axis Laser Propagation Using Heleeos, Scott L. Belton
Theses and Dissertations
Emerging technology high energy laser (HEL) weapon systems create a myriad of new threats to safety as well as security. One of the primary causes of these concerns is off-axis laser propagation caused by ever-present particulate and molecular scattering medium in the atmosphere. The scatter from these aerosols and molecules can redirect some of the HEL's concentrated energy towards unintended targets such as the eyes of pilots, friendly fighters on the surface, or innocent bystanders. Of particular interest to the laser intelligence (LASINT) community is the possibility that off-axis irradiance from HEL weapon systems could be covertly measured with enough …
Some Aspects Of The Mechanical Response Of Bmi 5250-4 Neat Resin At 191°C: Experiment And Modeling, John G. Balaconis
Some Aspects Of The Mechanical Response Of Bmi 5250-4 Neat Resin At 191°C: Experiment And Modeling, John G. Balaconis
Theses and Dissertations
The mechanical response of BMI 5250-4 neat resin at 191 degrees C was studied using both creep and recovery tests where several variables were allowed to change. In these tests, the effect of stress rate, prior history, and panel variability were all taken into account. During the creep test, the material showed both primary and secondary creep over 20 h. The recovery tests showed full recovery after it was subjected to 80% UTS. The higher stress rate caused a much greater response in both creep and recovery tests. The prior history was studied by allowing the specimens to go through …
An Epidemiological Approach To Terrorism, Kjirstin A. Bentson
An Epidemiological Approach To Terrorism, Kjirstin A. Bentson
Theses and Dissertations
There are many types of models for counterterrorism, explaining different problems that the military faces in the fight against terrorism. This thesis proposes that one of the fundamental assumptions underlying existing models of counterterrorism is that the struggle with terrorists can be understood as a war in the traditional sense of the term. We propose to rethink the struggle against terrorism as a fight against an infection. The epidemic of terrorist ideology within part of the world is a result, from this perspective, of the infectiousness of that ideology. Using the insights of the field of the epidemiology of ideas, …
Optimal Periodic Inspection Of A Stochastically Degrading System, Timothy B. Booher
Optimal Periodic Inspection Of A Stochastically Degrading System, Timothy B. Booher
Theses and Dissertations
This thesis develops and analyzes a procedure to determine the optimal inspection interval that maximizes the limiting average availability of a stochastically degrading component operating in a randomly evolving environment. The component is inspected periodically, and if the total observed cumulative degradation exceeds a fixed threshold value, the component is instantly replaced with a new, statistically identical component. Degradation is due to a combination of continuous wear caused by the component's random operating environment, as well as damage due to randomly occurring shocks of random magnitude. In order to compute an optimal inspection interval and corresponding limiting average availability, a …