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Theses and Dissertations

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Full-Text Articles in Aerospace Engineering

Error Characterization Of Flight Trajectories Reconstructed Using Structure From Motion, Daniel C. Alix Mar 2015

Error Characterization Of Flight Trajectories Reconstructed Using Structure From Motion, Daniel C. Alix

Theses and Dissertations

This research effort assessed the accuracy of Structure from Motion (SFM) algorithms in replicating aircraft fight trajectories. Structure from Motion techniques can be used to estimate aircraft trajectory by determining the position and pose of an aircraft mounted camera from a sequential series of images taken during flight. An algorithm is proposed and implemented that successfully reconstructed aircraft trajectory using only a known starting position and a sequential series of images. The error in and reliability of the algorithm was found to be a function of image resolution as well as the amount of overlap and angular separation between sequential …

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Navigation Constellation Design Using A Multi-Objective Genetic Algorithm, Heather C. Diniz Mar 2015

Navigation Constellation Design Using A Multi-Objective Genetic Algorithm, Heather C. Diniz

Theses and Dissertations

In satellite constellation design, performance and cost of the system drive the design process. The Global Positioning System (GPS) constellation is currently used to provide positioning and timing worldwide. As satellite technology has improved over the years, the cost to develop and maintain the satellites has increased. Using a constellation design tool, it is possible to analyze the tradeoffs of new navigation constellation designs (Pareto fronts) that illustrate the tradeoffs between position dilution of precision (PDOP) and system cost. This thesis utilized Satellite Tool Kit (STK) to calculate PDOP values of navigation constellations, and the Unmanned Spacecraft Cost Model (USCM) …

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Methods Of Measuring Stress Relaxation In Composite Tape Springs, Justin T. Heppe Mar 2015

Methods Of Measuring Stress Relaxation In Composite Tape Springs, Justin T. Heppe

Theses and Dissertations

Composite tape springs present an opportunity to use stored energy for the deployment of space structures. Concern has risen over the dissipation of strain energy during storage due to viscoelasticity inherent in polymeric materials commonly used as the composite matrix. Tests to measure the internal behavior of a composite tape spring over time are conducted along with methods of analyzing and fitting the resulting data. The three constant strain configurations tested were compression force of the cross section, a restraining force of a longitudinal fold, and the change in shape of a folded section. While the shape changing test did …

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Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just Mar 2015

Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just

Theses and Dissertations

The creation of a lighter than air vehicle using an inner vacuum instead of a lifting gas is considered. Specifically, the icosahedron shape is investigated as a design that will enable the structure to achieve positive buoyancy while resisting collapse from the atmospheric pressure applied. This research analyzes the dynamic response characteristics of the design, and examines the accuracy of the finite element model used in previous research by conducting experimental testing. The techniques incorporated in the finite element model are confirmed based on the experimental results using a modal analysis. The experimental setup designed will allow future research on …

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Optimized Flight Path For Localization Using Line Of Bearing, Namkyu Kim Mar 2015

Optimized Flight Path For Localization Using Line Of Bearing, Namkyu Kim

Theses and Dissertations

This research develops optimized flight paths for localization of a target using LOB measurements. The target area is expressed as an error ellipse using the measurement errors of the LOBs. The optimization approach is focused on minimizing the size of the error ellipse. The algorithm for the optimized path is generated and compared with typical flight paths. The optimization routine is based on the results revised from previous similar research in the literature. A geometrical method to estimate the error ellipse is combined with optimal control in this research. Each LOB gives a possible target area and this target area …

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Reflections Of A Wave: An Analysis Of Photonic Doppler Velocimetry Systems, Brian K. Lagrange Mar 2015

Reflections Of A Wave: An Analysis Of Photonic Doppler Velocimetry Systems, Brian K. Lagrange

Theses and Dissertations

Munitions are one of the Air Force's most effective weapons in eliminating targets, but also one of the most expensive. Due to the inherent high-cost in deploying munitions, munition shock wave detonation must be better observed and quantified for munitions to be more cost-efficient. PDV systems have the potential to achieve this quantification of shock wave properties on a molecular scale during solid-against-solid impacts. The overall goal of this research was to determine whether the current photonic Doppler velocimetry (PDV) system at Eglin Air Force Base is prepared for future explosive sensitivity testing. This determination was done through an uncertainty …

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Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Three Oxide/Oxide Ceramic Matrix Composites, Christopher J. Hull Mar 2015

Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Three Oxide/Oxide Ceramic Matrix Composites, Christopher J. Hull

Theses and Dissertations

Thermal stability of three oxide-oxide ceramic matrix composites was studied. The materials studied were NextelTM610/aluminosilicate (N610/AS), NextelTM720/aluminosilicate (N720/AS), and NextelTM720/Alumina (N720/A), commercially available oxide-oxide ceramic composites (COI Ceramics, San Diego, CA). The N610/AS composite consists of a porous aluminosilicate matrix reinforced with laminated woven alumina N610 fibers. The N720/AS and N720/A composites consist of a porous oxide matrix reinforced with laminated, woven mullite/alumina (NextelTM720) fibers. The matrix materials are aluminosilicate in N720/AS and alumina in N720/A. All three composites have no interface between the fibers and matrix, and rely on the porous …

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A Monocular Slam Method To Estimate Relative Pose During Satellite Proximity Operations, Scott J. Kelly Mar 2015

A Monocular Slam Method To Estimate Relative Pose During Satellite Proximity Operations, Scott J. Kelly

Theses and Dissertations

Automated satellite proximity operations is an increasingly relevant area of mission operations for the US Air Force with potential to significantly enhance space situational awareness (SSA). Simultaneous localization and mapping (SLAM) is a computer vision method of constructing and updating a 3D map while keeping track of the location and orientation of the imaging agent inside the map. The main objective of this research effort is to design a monocular SLAM method customized for the space environment. The method developed in this research will be implemented in an indoor proximity operations simulation laboratory. A run-time analysis is performed, showing near …

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A Cubesat Mission For Mapping Spot Beams Of Geostationary Communications Satellites, Jacob A. Lasarge Mar 2015

A Cubesat Mission For Mapping Spot Beams Of Geostationary Communications Satellites, Jacob A. Lasarge

Theses and Dissertations

As space-rated technologies become more compact and more readily available over time, the concept of accomplishing space missions with smaller nanosatellite-class spacecraft becomes increasingly feasible. This research focuses specifically on a CubeSat mission to assist with radio frequency (RF) domain verification; that of characterizing and mapping K-band spot beams from communications satellites in geostationary orbit. By flying a constellation of CubeSats through the edges of spot beams originating from geostationary communication satellites, the spot beam's coverage area will be characterized. This research conducts a mission feasibility assessment, identifies the principle mission requirements to complete a spot beam mapping CubeSat mission, …

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Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser Mar 2015

Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser

Theses and Dissertations

Tension-compression fatigue behavior of an oxide-oxide ceramic matrix composite was investigated at 1200°C in air and steam. The composite is comprised of an alumina matrix reinforced with Nextel 720 fibers woven in an eight harness satin weave. The composite relies on a porous matrix for damage tolerance. Compression and tension tests to failure were conducted to characterize basic mechanical properties. Tension-compression fatigue tests were performed at 1 Hz frequency with a ratio of minimum to maximum stress of -1. Maximum stresses ranged from 60-120 MPa. Fatigue run-out (defined as 105 cycles) was achieved in air at 80 MPa and in …

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Overall Effectiveness Measurement At Engine Temperatures With Reactive Film Cooling And Surface Curvature, Andrew J. Lynch Mar 2015

Overall Effectiveness Measurement At Engine Temperatures With Reactive Film Cooling And Surface Curvature, Andrew J. Lynch

Theses and Dissertations

The thesis presented here details the design, construction and initial testing of rig for use with high temperature film cooling testing. The film cooling rig was supplied with hot mainstream gas from a well-stirred reactor operating on a propane/air mixture capable of multiple equivalence ratios. The Hastelloy test plates contained an internal cooling channel to allow for overall effectiveness measurements. Thermocouples on both the freestream and internal surfaces of the test plate provided temperature differences for heat flux calculations. The test plates had a quarter circle leading edge with a tapered trailing edge to provide surface curvature for the film …

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Characterization And Modeling Of A Control Moment Gyroscope, Dylan R. Penn Mar 2015

Characterization And Modeling Of A Control Moment Gyroscope, Dylan R. Penn

Theses and Dissertations

The Air Force Research Laboratory (AFRL) is developing a spacecraft simulator that uses Control Moment Gyroscopes (CMGs). Prior to the research herein, the Air Force Institute of Technology (AFIT) designed and built six laboratory-rated CMGs for use on the AFRL spacecraft simulator. The main contributions of this research are in the testing and modeling of a single CMG. Designing, building, and operating spacecraft simulators is time consuming and expensive, but less so than tests with on-orbit spacecraft. Reductions in cost and schedule can be realized by investing in modeling the spacecraft simulator and payload before testing. A model of the …

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Characterization Of A Robotic Manipulator For Dynamic Wind Tunnel Applications, James C. Lancaster Mar 2015

Characterization Of A Robotic Manipulator For Dynamic Wind Tunnel Applications, James C. Lancaster

Theses and Dissertations

The newly acquired 6-DOF Motion Test Apparatus (MTA) was installed to perform dynamic wind tunnel testing in the AFIT Low Speed Wind Tunnel. Several complex motions revealed that the overall performance of the test rig needed improvement especially during small motions. The motions exposed that further enhancements would need to be performed individually for each joint. This research effort focused on the improvement of the MTA wrist roll motor and controller using a pitch oscillation. The controller software was improved using position feedback because the MTA wrist roll motor and controller exhibited reduced signal bias and amplitude attenuation. The enhanced …

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Computer Modeling Of A Rotating Detonation Engine In A Rocket Configuration, Nihar Shah Mar 2015

Computer Modeling Of A Rotating Detonation Engine In A Rocket Configuration, Nihar Shah

Theses and Dissertations

Detonation-based combustors leverage the higher thermodynamic efficiency of the Atkinson cycle compared to the traditional deflagration-based combustion of the Brayton cycle. The rotating detonation engine (RDE) has one or more shock waves rotating around an annulus. The RDE can theoretically be 20% more thermally efficient than a traditional deflagration-based cycle. A RDE was modeled in Numerical Propulsion System Simulation (NPSS) based on a model developed in Microsoft Excel. The thermodynamic analysis of the RDE in these models is broken into four streams. Empirical models were used to find the percentage of the total flow in each stream. The pre-detonation pressure …

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Optimal Recovery Trajectories For Automatic Ground Collision Avoidance Systems (Auto Gcas), Angela W. Suplisson Mar 2015

Optimal Recovery Trajectories For Automatic Ground Collision Avoidance Systems (Auto Gcas), Angela W. Suplisson

Theses and Dissertations

The USAF's F-16 Automatic Ground Collision Avoidance System (Auto GCAS) uses a single pre-planned roll to wings- level and 5-g pull-up to meet the operational requirements of being both aggressive and timely, meaning that extremely agile avoidance maneuvers will be executed at the last second to avoid the ground. There currently exists no similar Auto GCAS for manned military heavy' aircraft with lower climb performance such as transport, tanker, or bomber aircraft. This research proposes a new optimal control approach to the ground collision avoidance problem for heavy aircraft by mapping the aggressive and timely requirements of the automatic recovery …

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Design And Test Of An Attitude Determination And Control System For A 6u Cubesat Using Afit's Cubesat Testbed, Michael L. Tibbs Mar 2015

Design And Test Of An Attitude Determination And Control System For A 6u Cubesat Using Afit's Cubesat Testbed, Michael L. Tibbs

Theses and Dissertations

The design and test of a 6U CubeSat Attitude Determination and Control System (ADCS) are explored to establish single-axis control using AFIT's CubeSat testbed consisting of a Helmholtz cage and hemi-spherical air bearing. The Helmholtz cage produces a near-uniform magnetic field inside the cage while the air bearing provides a near-frictionless surface for ADCS testing. The ADCS testbed includes a four wheel pyramid reaction wheel array (RWA) for actuation and an inertial measurement unit (IMU) for attitude determination. Along with the ADCS hardware, the ADCS testbed also includes an Electrical Power System (EPS) and Command and Data Handling (CDH) for …

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Simulation Of Locking Space Truss Deployments For A Large Deployable Sparse Aperture Reflector, Dylan M. Van Dyne Mar 2015

Simulation Of Locking Space Truss Deployments For A Large Deployable Sparse Aperture Reflector, Dylan M. Van Dyne

Theses and Dissertations

Large deployable space structures require an inordinate amount of effort to fully design and test on Earth. To aid in the determination of the feasibility of the reflector, a method to simulate the structure's deployment was developed using COMSOL. The simulation model is comprised of a locking hinge truss that constitutes the partial reflector structure. To meet computational and temporal restrictions, the structure is simplified to use simple beams with square cross sections and is meshed to a sufficient accuracy with second order elements. The geometry is modeled in the truss's stowed configuration, with the connecting hinges and applied forces …

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Advancements Of In-Flight Mass Moment Of Inertia And Structural Deflection Algorithms For Satellite Attitude Simulators, Jonathan W. Wright Mar 2015

Advancements Of In-Flight Mass Moment Of Inertia And Structural Deflection Algorithms For Satellite Attitude Simulators, Jonathan W. Wright

Theses and Dissertations

Experimental satellite attitude simulators have been used to test and analyze control algorithms; driving down risk before implementation on operational satellites. Ideally, the dynamic response of a terrestrial-based experimental satellite attitude simulator matches that of an on-orbit satellite. Unfortunately, gravitational disturbance torques and poorly characterized moments of inertia introduce uncertainty into the system dynamics leading to questionable experimental results. This research consists of three distinct, but related contributions to the field of developing robust satellite attitude simulators. First, existing approaches to estimate mass moments and products of inertia are evaluated followed by a proposition and evaluation of a new approach …

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Mechanical Testing Of Ultra-High Temperature Ceramics At 1500°C In Air -Development Of An Experimental Facility And Test Method, Sheena L. Winder Mar 2015

Mechanical Testing Of Ultra-High Temperature Ceramics At 1500°C In Air -Development Of An Experimental Facility And Test Method, Sheena L. Winder

Theses and Dissertations

With a melting point in excess of 3000°C and a high density, ultra-high temperature ceramics (UHTCs) are a candidate material for hypersonic flight vehicles, atmospheric re-entry vehicles, and rocket propulsion systems. When ceramics are under consideration as a structural material, creep is an important design criterion and a life-limiting condition. However, the characterization of mechanical behavior at temperatures in excess of 1300°C has many challenges to overcome. Of utmost importance is the selection of materials for test fixtures. Materials selected must maintain their structural integrity, not cause chemical degradation of the test material, and not interfere with the acquisition of …

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Terrain Referenced Navigation Using Sift Features In Lidar Range-Based Data, Matthew T. Leines Dec 2014

Terrain Referenced Navigation Using Sift Features In Lidar Range-Based Data, Matthew T. Leines

Theses and Dissertations

The use of GNSS in aiding navigation has become widespread in aircraft. The long term accuracy of INS are enhanced by frequent updates of the highly precise position estimations GNSS provide. Unfortunately, operational environments exist where constant signal or the requisite number of satellites are unavailable, significantly degraded, or intentionally denied. This thesis describes a novel algorithm that uses scanning LiDAR range data, computer vision features, and a reference database to generate aircraft position estimations to update drifting INS estimates. The algorithm uses a single calibrated scanning LiDAR to sample the range and angle to the ground as an aircraft …

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Cloud-Induced Uncertainty For Visual Navigation, Alyssa N. Gutierrez Dec 2014

Cloud-Induced Uncertainty For Visual Navigation, Alyssa N. Gutierrez

Theses and Dissertations

This research addresses the numerical distortion of features due to the presence of clouds in an image. The research aims to quantify the probability of a mismatch between two features in a single image, which will describe the likelihood that a visual navigation system incorrectly tracks a feature throughout an image sequence, leading to position miscalculations. First, an algorithm is developed for calculating transparency of clouds in images at the pixel level. The algorithm determines transparency based on the distance between each pixel color and the average pixel color of the clouds. The algorithm is used to create a dataset …

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Multi-Objective Trajectory Optimization Of A Hypersonic Reconnaissance Vehicle With Temperature Constraints, Tadeusz J. Masternak Dec 2014

Multi-Objective Trajectory Optimization Of A Hypersonic Reconnaissance Vehicle With Temperature Constraints, Tadeusz J. Masternak

Theses and Dissertations

Temperature-constrained optimal trajectories for a scramjet-based hypersonic reconnaissance vehicle were generated by developing an optimal control formulation and solving it using a variable order Gauss-Radau quadrature collocation method. The vehicle was assumed to be an air-breathing reconnaissance aircraft that has specified takeoff/landing locations, airborne refueling constraints, specified no-fly zones, and specified targets for sensor data collections. The aircraft model included fight dynamics, aerodynamics, and thermal constraints. This model was incorporated into an optimal control formulation that includes constraints on both the vehicle as well as mission parameters, such as avoidance of no-fly zones and coverage of high-value targets. Optimal trajectories …

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Hot Streak Characterization In Serpentine Exhaust Nozzles, Darrell S. Crowe Dec 2014

Hot Streak Characterization In Serpentine Exhaust Nozzles, Darrell S. Crowe

Theses and Dissertations

Modern aircraft of the United States Air Force face increasingly demanding cost, weight, and survivability requirements. Serpentine exhaust nozzles within an embedded engine allow a weapon system to fulfill mission survivability requirements by providing denial of direct line-of-sight into the high-temperature components of the engine. Recently, aircraft have experienced material degradation and failure along the aft deck due to extreme thermal loading. Failure has occurred in specific regions along the aft deck where concentrations of hot gas have come in contact with the surface causing hot streaks. The prevention of these failures will be aided by the accurate prediction of …

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Optimal Collision Avoidance Trajectories For Unmanned/Remotely Piloted Aircraft, Nathan E. Smith Dec 2014

Optimal Collision Avoidance Trajectories For Unmanned/Remotely Piloted Aircraft, Nathan E. Smith

Theses and Dissertations

The post-911 environment has punctuated the force-multiplying capabilities that Remotely Piloted Aircraft (RPA) provides combatant commanders at all echelons on the battlefield. Not only have unmanned aircraft systems made near-revolutionary impacts on the battlefield, their utility and proliferation in law enforcement, homeland security, humanitarian operations, and commercial applications have likewise increased at a rapid rate. As such, under the Federal Aviation Administration (FAA) Modernization and Reform Act of 2012, the United States Congress tasked the FAA to provide for the safe integration of civil unmanned aircraft systems into the national airspace system (NAS) as soon as practicable, but not later …

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Experimental Uncertainty Associated With Traveling Wave Excitation, Geofrey S. Cox Sep 2014

Experimental Uncertainty Associated With Traveling Wave Excitation, Geofrey S. Cox

Theses and Dissertations

This dissertation research produces the experimental techniques required to evaluate mistuning in any rotor. Within operation, a rotor is subjected to a unique pattern of frequencies acting to excite the rotor. Utilizing traveling wave excitation, a rotor's critical frequencies and the respective excitation pattern are reproduced. Individual rotor blade frequency response functions are evaluated and statistically analyzed. The experimental results serve to not only verify the degree to which a rotor is mistuned, but also to provide an indication of the forced response amplification the mistuning induces. Within the experiment, definitive specifications were developed to ensure peak rotor responses. Numerical …

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Convective Heat Transfer With And Without Film Cooling In High Temperature, Fuel Rich And Lean Environments, Nathan J. Greiner Sep 2014

Convective Heat Transfer With And Without Film Cooling In High Temperature, Fuel Rich And Lean Environments, Nathan J. Greiner

Theses and Dissertations

Modern turbine engines require high turbine inlet temperatures and pressures to maximize thermal efficiency. Increasing the turbine inlet temperature drives higher heat loads on the turbine surfaces. In addition, increasing pressure ratio increases the turbine coolant temperature such that the ability to remove heat decreases. As a result, highly effective external film cooling is required to reduce the heat transfer to turbine surfaces. Testing of film cooling on engine hardware at engine temperatures and pressures can be exceedingly difficult and expensive. Thus, modern studies of film cooling are often performed at near ambient conditions. However, these studies are missing an …

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A Comparison Of Afghanistan, Yuma, Az, And Manufactured Sands Melted On Eb-Pvd Thermal Barrier Coatings, Nathaniel P. Opie Sep 2014

A Comparison Of Afghanistan, Yuma, Az, And Manufactured Sands Melted On Eb-Pvd Thermal Barrier Coatings, Nathaniel P. Opie

Theses and Dissertations

Sand ingestion into military aircraft turbine engines from desert environments have tested the performance and life of the engine. In particular, turbine section blades and nozzles are coated with a molten glass when the sand is heated to melting temperatures. This molten glass attacks protective coatings on the surface of these parts. Further research is needed to understand the sands behavior on thermal barrier coatings (TBC) when heated to melting temperatures. Also, further research is needed with manufactured sand used in current engine testing to understand the sand ingestion discrepancies between test engines and operational engines. In this study natural …

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Optimal Control Of Fully Routed Air Traffic In The Presence Of Uncertainty And Kinodynamic Constraints, Christopher D. Arendt Sep 2014

Optimal Control Of Fully Routed Air Traffic In The Presence Of Uncertainty And Kinodynamic Constraints, Christopher D. Arendt

Theses and Dissertations

A method is presented to extend current graph-based Air Traffic Management optimization frameworks. In general, Air Traffic Management is the process of guiding a finite set of aircraft, each along its pre-determined path within some local airspace, subject to various physical, policy, procedural and operational restrictions. This research addresses several limitations of current graph-based Air Traffic Management optimization methods by incorporating techniques to account for stochastic effects, physical inertia and variable arrival sequencing. In addition, this research provides insight into the performance of multiple methods for approximating non-differentiable air traffic constraints, and incorporates these methods into a generalized weighted-sum representation …

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Design And Evaluation Of Dual-Expander Aerospike Nozzle Upper Stage Engine, Joseph R. Simmons Iii Sep 2014

Design And Evaluation Of Dual-Expander Aerospike Nozzle Upper Stage Engine, Joseph R. Simmons Iii

Theses and Dissertations

The goal of the Dual-Expander Aerospike Nozzle, a modification to traditional engine architectures, is to find those missions and designs for which it has a competitive advantage over traditional upper stage engines such as the RL10. Previous work focused on developing an initial design to demonstrate the feasibility of the Dual-Expander Aerospike Nozzle. This research expanded the original cycle model in preparation for optimizing the engine's specific impulse and thrust-to-weight ratio. The changes to the model allowed automated parametric and optimization studies. Preliminary parametric studies varying oxidizer-to-fuel ratio, total mass flow, and chamber length showed significant improvements. Drawing on modeling …

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Characterization Of Sinusoidal Vibration Induced Fluid Motion In Spherical Elastomeric Diaphragm Tanks, Cody Ambrose Harris Jul 2014

Characterization Of Sinusoidal Vibration Induced Fluid Motion In Spherical Elastomeric Diaphragm Tanks, Cody Ambrose Harris

Theses and Dissertations

Elastomeric diaphragm tanks are commonly used in spacecraft applications to incite positive expulsion of hydrazine monopropellant. The diaphragm exhibits low flexural rigidity, causing it to easily fold under its own weight at low fill levels. If the tank is sinusoidally oscillated under standard gravity, such as during ground transportation or launch pad winding, these folds will result in rubbing, eventually wearing down the thin material to the point of failure. The ability to accurately predict the presence of folds, rubs, and center of gravity shifts for a given tank design and frequency excitation is thus of critical importance to mission …

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