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Theses and Dissertations

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Full-Text Articles in Aerospace Engineering

The Differential Vector Phase-Locked Loop For Global Navigation Satellite System Signal Tracking, James J. Brewer Jun 2014

The Differential Vector Phase-Locked Loop For Global Navigation Satellite System Signal Tracking, James J. Brewer

Theses and Dissertations

A novel differential vector phase-locked loop (DVPLL) is derived that takes GNSS code-phase and carrier-phase measurements from a base station and uses them to maintain an integer ambiguity resolved quality solution directly in the vector tracking loop of a rover receiver. The only state variables estimated and used to create the replica code and carrier signals from the base station measurements are three position and two clock states for a static test. Closing the individual loops solely through the navigation filter makes this a pure vector method. For short baselines, where differential atmospheric errors are small, the DVPLL can be …


The Prospect Of Responsive Spacecraft Using Aeroassisted, Trans-Atmospheric Maneuvers, Robert A. Bettinger Jun 2014

The Prospect Of Responsive Spacecraft Using Aeroassisted, Trans-Atmospheric Maneuvers, Robert A. Bettinger

Theses and Dissertations

Comprised of exo- and trans-atmospheric trajectory segments, atmospheric re-entry represents a complex dynamical event which traditionally signals the mission end-of-life for low-Earth orbit spacecraft. Transcending this paradigm, atmospheric re-entry can be employed as a means of operational maneuver whereby aerodynamic forces can be exploited to create an aeroassisted maneuver. Utilizing a notional trans-atmospheric, lifting re-entry vehicle with L/D =6, the first phase of research demonstrates the terrestrial reachability potential for skip entry aeroassisted maneuvers. By overflying a geographically diverse set of ground targets, comparative analysis indicates a significant savings in delta V expenditure for skip entry compared with exo-atmospheric maneuvers. …


Non-Linear Optimization Applied To Angle-Of-Arrival Satellite-Based Geolocation, Stephen D. Hartzell Jun 2014

Non-Linear Optimization Applied To Angle-Of-Arrival Satellite-Based Geolocation, Stephen D. Hartzell

Theses and Dissertations

Geolocation is a common application for satellite systems. This involves estimating an object's location (herein called the subject) based on noisy satellite data. Many geolocation methods exist; however, none are tailored specifically for the unique problems faced by satellite systems. Some satellites are so far from the subject being localized that by the time the satellite receives a signal from the subject it might have moved appreciably. Furthermore, some satellites or terrestrial sensors may be much closer to the subject than others. Therefore, sensors may need to be weighted based upon their distance to the subject being localized. In addition, …


Minimization Of The Effects Of Secondary Reactions On Turbine Film Cooling In A Fuel Rich Environment, Andrew T. Shewhart Jun 2014

Minimization Of The Effects Of Secondary Reactions On Turbine Film Cooling In A Fuel Rich Environment, Andrew T. Shewhart

Theses and Dissertations

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow and augmented heat transfer to the blade arises. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream …


Flexible Slosh Diaphragm Modeling And Simulation In Propellant Tanks, Darren Vaughn Levine May 2014

Flexible Slosh Diaphragm Modeling And Simulation In Propellant Tanks, Darren Vaughn Levine

Theses and Dissertations

iquid sloshing and propellant distribution is an important field of research for aerospace applications such as launch vehicles and spacecraft. The propellant mass behavior can greatly influence vehicle dynamics, altering trajectories and structural loading distributions. In order to combat these concerns some propellant tanks employ thin elastomeric diaphragms to separate the fuel from the gas volumes and restrict the fluid's motion. The diaphragm’s flexible behavior is generally highly nonlinear, and various propellant fill levels and acceleration conditions can cause large deflections resulting in complex buckling and folding patterns. When complex and non-uniform deformations occur, there is potential for diaphragm wear …


Gps Multipath Reduction With Correlator Beamforming, Jason M. Barhorst Mar 2014

Gps Multipath Reduction With Correlator Beamforming, Jason M. Barhorst

Theses and Dissertations

This research effort investigates the feasibility of beamforming using a single Global Positioning System (GPS) front end. Traditional methods of beamforming use multiple front ends, typically one per antenna element. By enabling a receiver to sample a switched antenna array, the hardware cost of implementing a GPS antenna array can be significantly reduced. Similar techniques of reducing the number of receivers have been used by Locata Corporation in the design of their non-GPS positioning systems. However, Locata Corporation's local transmitters provide a signal strength much higher than GPS's signal strength. For this reason, the inclusion of low-noise amplifiers into the …


Radio Frequency Emitter Geolocation Using Cubesats, Andrew J. Small Mar 2014

Radio Frequency Emitter Geolocation Using Cubesats, Andrew J. Small

Theses and Dissertations

The ability to locate an RF transmitter is a topic of growing interest for civilian and military users alike. Geolocation can provide critical information for the intelligence community, search and rescue operators, and the warfighter. The technology required for geolocation has steadily improved over the past several decades, allowing better performance at longer baseline distances between transmitter and receiver. The expansion of geolocation missions from aircraft to spacecraft has necessitated research into how emerging geolocation methods perform as baseline distances are increased beyond what was previously considered. The CubeSat architecture is a relatively new satellite form which could enable small-scale, …


Image-Aided Navigation Using Cooperative Binocular Stereopsis, Justin T. Soeder Mar 2014

Image-Aided Navigation Using Cooperative Binocular Stereopsis, Justin T. Soeder

Theses and Dissertations

This thesis proposes a novel method for cooperatively estimating the positions of two vehicles in a global reference frame based on synchronized image and inertial information. The proposed technique - cooperative binocular stereopsis - leverages the ability of one vehicle to reliably localize itself relative to the other vehicle using image data which enables motion estimation from tracking the three dimensional positions of common features. Unlike popular simultaneous localization and mapping (SLAM) techniques, the method proposed in this work does not require that the positions of features be carried forward in memory. Instead, the optimal vehicle motion over a single …


Investigation Of The Potential For Ftir As A Nondestructive Inspection Technique For Aircraft Coating Degradation, Hans G. Korth Mar 2014

Investigation Of The Potential For Ftir As A Nondestructive Inspection Technique For Aircraft Coating Degradation, Hans G. Korth

Theses and Dissertations

Polyurethane-based aircraft coating degradation was examined using Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTs). Two sample sets were aged in an autoclave; each containing four samples. Sample set A contained two as-cured samples and two samples treated to a level of visual degradation. Sample set B contained one sample left as-cured and three samples of differing degradation. DRIFTs spectra were collected on sample set B and singular value decomposition (SVD) was used to reveal trends between the degradation levels. Linear discriminant analysis (LDA) was then applied to the SVD coefficients to determine the most accurate spectral band for classification of …


Ceramic Matrix Characterization Under A Gas Turbine Combustion And Loading Environment, Dustin J. Bertrand Mar 2014

Ceramic Matrix Characterization Under A Gas Turbine Combustion And Loading Environment, Dustin J. Bertrand

Theses and Dissertations

The fatigue behavior of Hyper-Therm High Temperature Composites (HTC) Sylramic-iBN/BN/CVI SiC material was investigated while being subjected to a unique high temperature environment. The specimens used in this research were subjected to a high temperature combustion environment intended to simulate the conditions this material would see in turbine engine applications. Results show that the effects of the combustion environment on the materials fatigue behavior are significant with increasing temperature.


Operational Characteristics Of An Ultra Compact Combustor, Christopher J. Damele Mar 2014

Operational Characteristics Of An Ultra Compact Combustor, Christopher J. Damele

Theses and Dissertations

Ultra Compact Combustors offer unique solutions to minimize engine size and weight. They accomplish this by reducing the number of components in the engine core and perform the combustion in a circumferential cavity that encircles the core flow. Within this cavity, the fuel is injected rich. Burning continues to occur in the vane passage beneath the circumferential cavity which must be completed in a controlled manner prior to the inlet plane of the turbine rotor. Furthermore, the temperature distribution at the exit of the vane passage must be controlled to generate high work extraction from the turbine. The primary metrics …


Design And Analysis Of An Attitude Determination And Control Subsystem (Adcs) For Afit's 6u Standard Bus, Erin R. Dannemeyer Mar 2014

Design And Analysis Of An Attitude Determination And Control Subsystem (Adcs) For Afit's 6u Standard Bus, Erin R. Dannemeyer

Theses and Dissertations

The design and testing of AFIT's 6U Attitude Determination and Control Subsystem (ADCS) are explored to establish 3-axis attitude control. The development of AFIT's 6U CubeSat standard bus is an on-going research effort designed to create in-house CubeSat bus components and software. The 6U chassis measures approximately 11 x 24 x 37 cm3 and can have a mass up to 12 kg. The larger bus size (as compared to the more common 3U CubeSat) allows for increased power capabilities and potential to host multiple or larger payloads. Individual ADCS hardware components were either commercially purchased or built in-house and …


Thermal Characterization Of The Air Force Institute Of Technology Solar Simulation Thermal Vacuum Chamber, Daniel M. Hatzung Mar 2014

Thermal Characterization Of The Air Force Institute Of Technology Solar Simulation Thermal Vacuum Chamber, Daniel M. Hatzung

Theses and Dissertations

Although predictive thermal modeling on CubeSats has previously been accomplished, a method to validate these predictive models with terrestrial experiments is essential for developing confidence in the model. As a part of this effort, AFIT has acquired a new Solar Simulation Thermal Vacuum Chamber. This research analyzed the thermal environment to which a test article is exposed within the AFIT Solar Simulation Thermal Vacuum Chamber. A computational model of the thermal environment in the chamber was created and then validated using an experimental buildup approach through thermal balance testing of the empty chamber and an aluminum plate. First, the modeled …


Feasibilty Of Very Large Sparse Aperture Depolyable Antennas, Jason C. Heller Mar 2014

Feasibilty Of Very Large Sparse Aperture Depolyable Antennas, Jason C. Heller

Theses and Dissertations

The objective of this research is to explore the technical soundness of a very large, cross-shaped, parabolic, sparse aperture antenna extending 75 m from the bus. Specifically, describing the environment of the satellite, the effect of fabrication error on the structure and the remaining error budget for the system. The methodology involves creation of an ideal truss structure, to which all others are compared. A uniform distribution of proportional errors up to 1e-5 is introduced into the truss members' lengths and the models are subjected to a static Finite Element Analysis. A solution for the surface normal error is addressed …


Optimal Uav Path Planning For Tracking A Moving Ground Vehicle With A Gimbaled Camera, Riley A. Livermore Mar 2014

Optimal Uav Path Planning For Tracking A Moving Ground Vehicle With A Gimbaled Camera, Riley A. Livermore

Theses and Dissertations

This research develops a path planning algorithm that autonomously controls a UAV to provide convoy overwatch. The optimization algorithm determines the best path to y through developing a cost function that minimizes the control effort of the UAV and the deviation from a desired slant range. A heuristic-based algorithm was developed and implemented on the autopilot to approximate the optimal solution. In flight test, the UAV successfully tracked a moving ground vehicle by continually placing the UAV's loiter point directly above the ground vehicle's current location. This method was called the \follow-me mode and provided the baseline for real-world UAV …


Influence Of Mach Number And Dynamic Pressure On Cavity Tones And Freedrop Trajectories, Justin D. Merrick Mar 2014

Influence Of Mach Number And Dynamic Pressure On Cavity Tones And Freedrop Trajectories, Justin D. Merrick

Theses and Dissertations

Weapons release at supersonic speeds from an internal weapons bay is a highly desirable capability. To ensure a successful release at multiple Mach numbers, the aerodynamic environment must be well-understood and repeatable, with a robust system for safe testing of store separation. For this reason, experimental methods were used to investigate the characteristics of a scaled WICS bay with a length-to-depth ratio of 4.5 at multiple Mach numbers and stagnation pressures. Three new nozzles were designed, manufactured, and characterized for the AFIT small supersonic tunnel, yielding freestream Mach numbers of 2.22, 1.84, and 1.43. In addition, a control valve was …


The Use Of An Ultra-Compact Combustor As An Inter-Turbine Burner For Improved Engine Performance, Jose L. Miranda Mar 2014

The Use Of An Ultra-Compact Combustor As An Inter-Turbine Burner For Improved Engine Performance, Jose L. Miranda

Theses and Dissertations

An Inter-Turbine Burner (ITB) represents a novel mechanism for generating additional work from a gas turbine engine in applications where an afterburner would typically be used. An ITB can achieve higher thermal efficiencies over a typical afterburner while also generating shaft work versus only additional thrust. In an effort to investigate the potential applications for the ITB, a numerical engine cycle comparison was made between the ITB cycle and a conventional afterburning cycle using the Numerical Propulsion System Simulation (NPSS). In the case of thrust augmentation, the ITB model outperformed the afterburning model when Thrust Specific Fuel Consumption (TSFC) is …


Thermal Loss Determination For A Small Internal Combustion Engine, Joshua A. Rittenhouse Mar 2014

Thermal Loss Determination For A Small Internal Combustion Engine, Joshua A. Rittenhouse

Theses and Dissertations

Three analysis techniques were used to measure the heat rejection of a 55 cc air-cooled two-stroke engine. This study was performed as part of a larger effort aimed at extending range and endurance limitations of Group 1 & 2 Remotely Piloted Aircraft (RPA). The engine selected for the study was a 55 cc gasoline-fueled, carbureted, spark-ignition engine made by 3W-Modellmotoren and is representative of RPA engines in these groups. With a surface area to volume ratio of 1.48 1/cm, the engine is in a size region where thermal losses begin to dominate engine efficiency and thermal efficiencies …


A Low Cost Implementation Of Autonomous Takeoff And Landing For A Fixed Wing Uav, Thomas Carnes Jan 2014

A Low Cost Implementation Of Autonomous Takeoff And Landing For A Fixed Wing Uav, Thomas Carnes

Theses and Dissertations

The take-off and landing of an Unmanned Aerial Vehicle (UAV) is often the most critical and accident prone portion of its mission. This potential hazard coupled with the time and resources necessary to train a remote UAV pilot makes it desirable to have autonomous take-off and landing capabilities for UAVs. However, a robust, reliable, and accurate autonomous takeoff and landing capability for fixed-wing aircraft is not an available feature in many low-cost UAV flight control systems. This thesis describes the design of an autonomous take-off and landing algorithm implemented on an existing low-cost flight control system for a small fixed …


Aerodynamic Performance And Particle Image Velocimetery Of Piezo Actuated Biomimetic Manduca Sexta Engineered Wings Towards The Design And Application Of A Flapping Wing Flight Vehicle, Anthony M. Deluca Dec 2013

Aerodynamic Performance And Particle Image Velocimetery Of Piezo Actuated Biomimetic Manduca Sexta Engineered Wings Towards The Design And Application Of A Flapping Wing Flight Vehicle, Anthony M. Deluca

Theses and Dissertations

Considerable research and investigation has been conducted on the aerodynamic performance, and the predominate flow physics of the Manduca sexta size of biomimetically designed and fabricated wings as part of the AFIT FWMAV design project. Despite a burgeoning interest and research into the diverse field of flapping wing flight and biomimicry, the aerodynamics of flapping wing flight remains a nebulous field of science with considerable variance into the theoretical abstractions surrounding aerodynamic mechanisms responsible for aerial performance. Traditional FWMAV flight models assume a form of a quasi-steady approximation of wing aerodynamics based on an infinite wing element model (BEM). An …


Scattering, Adsorption, And Langmuir-Hinshelwood Desorption Models For Physisorptive And Chemisorptive Gas-Surface Systems, Brook I. Bentley Sep 2013

Scattering, Adsorption, And Langmuir-Hinshelwood Desorption Models For Physisorptive And Chemisorptive Gas-Surface Systems, Brook I. Bentley

Theses and Dissertations

Surface effects limit the performance of hypersonic vehicles, micro-electro-mechanical devices, and directed energy systems. This research develops methods to predict adsorption, scattering, and thermal desorption of molecules on a surface. These methods apply to physisorptive (adsorption and scattering) and chemisorptive (thermal desorption) gas-surface systems, and are developed under the Direct Simulation Monte Carlo construct. The novel adsorption and scattering contribution, the Modified Kisliuk with Scattering method, predicts angular and energy distributions, and adsorption probabilities. These results agree more closely with experiment than the state-of-the-art Cercignani-Lampis-Lord scattering kernel. Super-elastic scattering is predicted. Gas-adlayer interactions are included for the first time. The …


Trajectory Optimization For Spacecraft Collision Avoidance, James W. Sales Jr. Sep 2013

Trajectory Optimization For Spacecraft Collision Avoidance, James W. Sales Jr.

Theses and Dissertations

The last several decades have resulted in an unfortunate byproduct of space exploration and development: orbital debris. Satellites in Low Earth Orbit have been required to make an ever increasing number of course corrections in order to avoid collisions. Despite efforts to the contrary, collisions continue to occur, each time creating additional debris and increasing the requirement for the remaining satellites to maneuver. Every required maneuver decreases a satellite's service life. The purpose of this study is to develop a minimum thrust profile to maneuver an orbiting satellite out of its projected error ellipse before a collision occurs. For comparison, …


Characterizing G-Loading, Swirl Direction And Rayleigh Losses In An Ultra Compact Combustor, Jacob D. Wilson Sep 2013

Characterizing G-Loading, Swirl Direction And Rayleigh Losses In An Ultra Compact Combustor, Jacob D. Wilson

Theses and Dissertations

Previous research has been conducted showing significant benefits on combustion efficiency and stability by creating high centripetally accelerated, also known as g-loaded, combustion environments. Ultra Compact Combustor systems decrease size and weight of the overall engine by burning in a circumferential direction around a hybrid vane row where the high equivalence ratio cavity flow is quick quenched to lean by the core flow. The hybrid vane row integrates the compressor, combustor, and turbine for further length reduction and weight savings. Fuel and air are brought into the cavity and combusted in a high g-loaded environment driven by air injection at …


Architecting Integrated System Health Management For Airworthiness, Kerwin C. Teong Sep 2013

Architecting Integrated System Health Management For Airworthiness, Kerwin C. Teong

Theses and Dissertations

Integrated System Health Management (ISHM) for Unmanned Aerial Systems (UAS) has been a new area of research - seeking to provide situational awareness to mission and maintenance operations, and for improved decision-making with increased self-autonomy. This research effort developed an analytic architecture and an associated discrete-event simulation using Arena® to investigate the potential benefits of ISHM implementation onboard an UAS. The objective of this research is two-fold: firstly, to achieve continued airworthiness by investigating the potential extension of UAS expected lifetime through ISHM implementation, and secondly, to reduce life cycle costs by implementing a Condition-Based Maintenance (CBM) policy with better …


Crack Initiation And Growth Behavior At Corrosion Pit In 7075-T6 High Strength Aluminum Alloy, Eric M. Hunt Jun 2013

Crack Initiation And Growth Behavior At Corrosion Pit In 7075-T6 High Strength Aluminum Alloy, Eric M. Hunt

Theses and Dissertations

Research on fatigue crack formation from two types corrosion pits tangent to a circular hole in a 7075-T6 aluminum alloy subjected to uni-axial loads (R = 0.5, lambda = 0) in both an air and saltwater environment provides a method for exploring crack initiation and initial growth rates. This work focuses on a fracture mechanics approach to explore the transition from corrosion pit to crack growth. Specimens with a cylinder shaped through-pit tangent to a circular hole have a closed form solution to predict this delta K that closely resembles the finite element solutions. Specimens with a semi-circular corner-pit tangent …


Design Of A Lighter Than Air Vehicle That Achieves Positive Buoyancy In Air Using A Vacuum, Trent T. Metlen Jun 2013

Design Of A Lighter Than Air Vehicle That Achieves Positive Buoyancy In Air Using A Vacuum, Trent T. Metlen

Theses and Dissertations

Three designs for a Lighter Than Air (LTA) structure that achieve positive buoyancy using a vacuum in place of a lifting gas were proposed and evaluated. The ratio of structure weight to the weight of displaced air was termed Weight/Buoyant Force (W/B) where a W/B1 corresponds to positive buoyancy. Two methods of geometrically stiffening a sphere were investigated and their W/B evaluated. A thin shelled sphere of beryllium stiffened with an isogrid of blade type stiffeners using Ultra High Modulus (UHM) carbon epoxy was predicted to give a W/B= 0.79. A geodesic sphere composed of a frame of cylindrical, UHM, …


Evaluation Of The Thorax Of Manduca Sexta For Flapping Wing Micro Air Vehicle Applications, Brian C. Cranston Mar 2013

Evaluation Of The Thorax Of Manduca Sexta For Flapping Wing Micro Air Vehicle Applications, Brian C. Cranston

Theses and Dissertations

The tobacco hornworm hawkmoth (Manduca sexta) provides an excellent model from which to gather knowledge pertaining to the development of a Flapping Wing Micro Air Vehicle (FWMAV). One of the major challenges in design of a FWMAV is the energy demanding nature of low Reynolds number flapping flight. Therefore, an understanding of the power required by the flight muscles to actuate the wings is essential for the design of a FWMAV. The M.sexta wing/thorax mechanism was evaluated as a mechanical system in order to gain insight to the mechanical power required to produce the full natural wing stroke. A unique …


Power Requirements For Bi-Harmonic Amplitude And Bias Modulation Control Of A Flapping Wing Micro Air Vehicle, Justin R. Carl Mar 2013

Power Requirements For Bi-Harmonic Amplitude And Bias Modulation Control Of A Flapping Wing Micro Air Vehicle, Justin R. Carl

Theses and Dissertations

Flapping wing micro air vehicles (FWMAV) have been a growing field in the research of micro air vehicles, but little emphasis has been placed on control theory. Research is ongoing on how to power FWMAVs where mass is a major area of concern. However, there is little research on the power requirements for the controllers to manipulate the wings of a FWMAV. A novel control theory, BABM, allows two actuators to produce forces and moments in five of the FWMAV's six DOF. Several FWMAV prototypes were constructed and tested on a six-component balance. Data was collected for varying control parameters …


Opto-Mechanical Design Of A Chromotomographic Imager Direct-Vision Prism Element, Timothy E. Coon Mar 2013

Opto-Mechanical Design Of A Chromotomographic Imager Direct-Vision Prism Element, Timothy E. Coon

Theses and Dissertations

Chromotomographic Imaging (CTI) offers advantages in remote sensing by resolving intensity distribution spatially, spectrally, and temporally. The Chromotomography Experiment (CTEx) at the Air Force Institute of Technology (AFIT) explores the application of CTI as a space-based observer. Previous work in instrument development has revealed many of the intricacies of component fabrication and how they impact the resolving of image data. The proposed CTEx instrument has as its chromatic dispersion element a direct-vision prism (DVP) that is made to rotate in order to achieve multiple projection angles. Analysis of previous research established the need for a more accurate characterization of the …


Characterization Of Rotating Detonation Engine Exhaust Through Nozzle Guide Vanes, Nick D. Debarmore Mar 2013

Characterization Of Rotating Detonation Engine Exhaust Through Nozzle Guide Vanes, Nick D. Debarmore

Theses and Dissertations

A RDE has higher thermal efficiencies in comparison to its traditional gas turbine counterparts. Thus, as budgets decrease and fuel costs increase, RDEs have become a research focus for the United States Air Force. An integration assembly for attaching the first NGV section from a T63 gas turbine engine to a 6 inch diameter RDE was designed and built for this study. Pressure, temperature, and unsteadiness measurements were completed in this study to characterize the exhaust flow of the RDE through the NGVs. The experiment found that stagnation pressure dropped an average of 4% through the NGVs, and that unsteadiness …