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Articles 331 - 360 of 1780
Full-Text Articles in Aerospace Engineering
Design And Test Of An Autonomy Monitoring Service To Detect Divergent Behaviors On Unmanned Aerial Systems, Loay Y. Almannaei
Design And Test Of An Autonomy Monitoring Service To Detect Divergent Behaviors On Unmanned Aerial Systems, Loay Y. Almannaei
Theses and Dissertations
Operation of Unmanned Aerial Vehicles (UAV) support many critical missions in the United State Air Force (USAF). Monitoring abnormal behavior is one of many responsibilities of the operator during a mission. Some behaviors are hard to be detect by an operator, especially when flying one or more autonomous vehicles; as such, detections require a high level of attention and focus to flight parameters. In this research, a monitoring system and its algorithm are designed and tested for a target fixed-wing UAV. The Autonomy Monitoring Service (AMS) compares the real vehicle or simulated Vehicle with a similar simulated vehicle using Software …
Use Of Garmin Autopilot Envelope Protection System For Simplified Vehicle Operations In General Aviation, Stephen Sullivan
Use Of Garmin Autopilot Envelope Protection System For Simplified Vehicle Operations In General Aviation, Stephen Sullivan
Theses and Dissertations
The general aviation industry suffers from high rates of fatalities and accidents occurring due to loss of control while in flight. This thesis research aims to implement a simple yet effective simplified vehicle operations (SVO) scheme that uses a Garmin autopilot system to create a pilot-on-the-loop controller to help prevent loss of control incidents from occurring. With this scheme, the pilot is controlling turns and climb rates instead of elevator and aileron deflections and is protected from the risk of under-speed and stall through the Garmin autopilots built-in limits. To interface with the autopilot system, a Raspberry Pi and Pythonbased …
Flight Path Control During Hypersonic Atmospheric Entry Using Active Magnetic Arrays, Matthew Tyler Austin
Flight Path Control During Hypersonic Atmospheric Entry Using Active Magnetic Arrays, Matthew Tyler Austin
Theses and Dissertations
The purpose of this thesis is to study the reaction to the Lorentz force induced during the hypersonic regime of flight by an active magnetic field. The effect that a magnetic array has on the flight characteristics of a blunt body during Earth atmospheric entry is characterized and isolated for independent analysis. This is done to show that mission-specific benefits to utilizing this method of entry control exist and therefore warrant further study. To conduct this analysis, a 1000 kg blunt body test case was used. This craft contains three separate magnets located behind the nose with two of them …
Flight Testing Of The Piper J4a Cub Coupe, Kenneth Burton Connick
Flight Testing Of The Piper J4a Cub Coupe, Kenneth Burton Connick
Theses and Dissertations
Flight testing is an important part of in the airplane design process. This testing is performed to ensure that the airplane complies with the established requirements and regulations for flight safety, as well as to ensure it meets its mission objectives. The Federal Aviation Administration (FAA) currently governs these requirements and regulations for civilian aircraft and provides airworthiness certifications. The FAA regulations were introduced in 1965. Prior to that, civilian aircraft were certified through the Civil Aeronautics Administration using Civil Air Regulations (CARs).
Automation Of Process Planning For Automated Fiber Placement, Joshua A. Halbritter
Automation Of Process Planning For Automated Fiber Placement, Joshua A. Halbritter
Theses and Dissertations
Process planning represents an essential stage of the Automated Fiber Placement (AFP) workflow. It develops useful and efficient machine processes based upon the working material, composite design, and manufacturing resources. The current state of process planning requires a high degree of interaction from the process planner and could greatly benefit from increased automation. Therefore, a list of key steps and functions are created to identify the more difficult and time-consuming phases of process planning. Additionally, a set of metrics must exist by which to evaluate the effectiveness of the manufactured laminate from the machine code created during the Process Planning …
Design And Control Of An Arrayed Infrared (Mat-Ir) Heater For Accurate Heating Control During Automated Fiber Placement, Benjamin L. C. Greenberg
Design And Control Of An Arrayed Infrared (Mat-Ir) Heater For Accurate Heating Control During Automated Fiber Placement, Benjamin L. C. Greenberg
Theses and Dissertations
Automated Fiber Placement (AFP) is the primary method for manufacturing of large and complex primary composite structures in the aerospace industry. Predominantly, AFP use infrared heaters to ensure appropriate tackiness between the different composite layers. The task of accurately detecting and obtaining a set uniform temperature, across the nip point/line, has proven to be difficult. Traditional AFP heat processes are mostly open-loop controlled, which can lead to issues with ensuring accurate and uniform heat distributions. The latter need to be obtained to allow for proper material consolidation to occur. Uneven heating could cause degradation at the center or at the …
Object Detection With Deep Learning To Accelerate Pose Estimation For Automated Aerial Refueling, Andrew T. Lee
Object Detection With Deep Learning To Accelerate Pose Estimation For Automated Aerial Refueling, Andrew T. Lee
Theses and Dissertations
Remotely piloted aircraft (RPAs) cannot currently refuel during flight because the latency between the pilot and the aircraft is too great to safely perform aerial refueling maneuvers. However, an AAR system removes this limitation by allowing the tanker to directly control the RP A. The tanker quickly finding the relative position and orientation (pose) of the approaching aircraft is the first step to create an AAR system. Previous work at AFIT demonstrates that stereo camera systems provide robust pose estimation capability. This thesis first extends that work by examining the effects of the cameras' resolution on the quality of pose …
Relational Database Design And Multi-Objective Database Queries For Position Navigation And Timing Data, Sean A. Mochocki
Relational Database Design And Multi-Objective Database Queries For Position Navigation And Timing Data, Sean A. Mochocki
Theses and Dissertations
Performing flight tests is a natural part of researching cutting edge sensors and filters for sensor integration. Unfortunately, tests are expensive, and typically take many months of planning. A sensible goal would be to make previously collected data readily available to researchers for future development. The Air Force Institute of Technology (AFIT) has hundreds of data logs potentially available to aid in facilitating further research in the area of navigation. A database would provide a common location where older and newer data sets are available. Such a database must be able to store the sensor data, metadata about the sensors, …
Alternate Materials For High-Speed Projectile Casing, Andrew W. Beard
Alternate Materials For High-Speed Projectile Casing, Andrew W. Beard
Theses and Dissertations
A high-speed projectile impact is a highly complex dynamic problem that can be simplified with the use of finite element analysis solvers. Abaqus/Explicit was used to evaluate the impact of various projectiles using a plane strain setup. Using a baseline stainless steel projectile, the proposed sandwich construction design was analyzed and compared to the baseline projectile. The overall goal was to see if a new composite casing could perform similarly to the simple baseline projectile. The sandwich construction used stainless steel, tungsten, and silicon-carbide reinforce aluminum as outer and inner shell materials. The core material was created using additive manufacturing …
Investigation Of Ultem 9085 For Use In Printed Orbital Structures, William R. Gallagher
Investigation Of Ultem 9085 For Use In Printed Orbital Structures, William R. Gallagher
Theses and Dissertations
Additive manufacturing is revolutionizing industries ranging from medicine to space. However, the structural characteristics of plastic parts created by these methods are not as well understood as their more established counterparts. This research explored two relevant areas: how the structural characteristics of ULTEM 9085 plastic behaved after exposure to orbital conditions and the design of the cross-sectional area of a beam to be 3-D printed in microgravity based on the expected loads from the printer. To study orbital effects, ULTEM 9085 was printed into 1/4th scale ASTM D638- 14 dogbones using a Stratasys 450mc printer. These dogbones were placed in …
Timely Near-Optimal Path Generation For An Unmanned Aerial System In A Highly Constrained Environment, Kyle J. Matissek
Timely Near-Optimal Path Generation For An Unmanned Aerial System In A Highly Constrained Environment, Kyle J. Matissek
Theses and Dissertations
A current challenge in path planning is the ability to efficiently calculate a near-optimum path solution through a highly-constrained environment in near-real time. In addition, computing performance on a small unmanned aerial vehicle is typically limited due to size and weight restrictions. The proposed method determines a solution quickly by first mapping a highly constrained three-dimensional environment to a two-dimensional weighted node surface in which the weighting accounts for both the terrain gradient and the vehicle's performance. The 2D surface is then discretized into triangles which are sized based upon the vehicle maneuverability and terrain gradient. The shortest feasible path …
Flight Characteristic Verification Of The Variable Camber Compliant Wing, Sharee B. Acosta
Flight Characteristic Verification Of The Variable Camber Compliant Wing, Sharee B. Acosta
Theses and Dissertations
Morphing wing technology gives aircraft the ability to change wing shape to control the aircraft and flight performance characteristics. AFIT, AFRL and USU Aero Lab have collaborated to design and test a variable camber compliant wing (VCCW) on a small unmanned aerial vehicle (UAV). Flight tests demonstrated the wing performance and provided data to refine a VCCW flight simulator. Work was completed with the USU AeroLab-generated MachUp and the actual flight data to improve the simulator to provide results close to those of the actual flight test. The research provides a tool to reduce time and cost for future flight …
Signal Quality Monitoring Of Gnss Signals Using A Chip Shape Deformation Metric, Nicholas C. Echeverry
Signal Quality Monitoring Of Gnss Signals Using A Chip Shape Deformation Metric, Nicholas C. Echeverry
Theses and Dissertations
The Global Navigation Satellite System continues to become deeply em-bedded within modern civilization, and is depended on for confident, accurate navigation information. High precision position and timing accuracy is typically achieved using differential processing, however these systems provide limited compensation for distortions caused by multi-path or faulty satellite hardware. Signal Quality Monitoring (SQM) aims to provide confidence in a receivers Position, Navigation, and Timing solution and to offer timely warnings in the event that signal conditions degrade to unsafe levels. The methods presented in this document focus on implementing effective SQM using low-cost Commercial Off-the-Shelf equipment, a Software Defined Radio, …
Structural Dynamic And Inherent Damping Characterization Of Additively Manufactured Airfoil Components, Andrew W. Goldin
Structural Dynamic And Inherent Damping Characterization Of Additively Manufactured Airfoil Components, Andrew W. Goldin
Theses and Dissertations
The push for low cost and higher performance/efficient turbine engines have introduced a new demand for novel technologies to improve robustness to vibrations resulting in High Cycle Fatigue (HCF). There have been many proposed solutions to this, some passive and some active. With the advent of Additive Manufacturing (AM), new damping techniques can now be incorporated directly into the design and manufacture process to suppress the vibrations that create HCF. In this study, this novel unfused pocket damping technology is applied to a blade structure and the resulting damping effectiveness is quantified. The application of this technology to complex geometries …
Improved Ground-Based Monocular Visual Odometry Estimation Using Inertially-Aided Convolutional Neural Networks, Josiah D. Watson
Improved Ground-Based Monocular Visual Odometry Estimation Using Inertially-Aided Convolutional Neural Networks, Josiah D. Watson
Theses and Dissertations
While Convolutional Neural Networks (CNNs) can estimate frame-to-frame (F2F) motion even with monocular images, additional inputs can improve Visual Odometry (VO) predictions. In this thesis, a FlowNetS-based [1] CNN architecture estimates VO using sequential images from the KITTI Odometry dataset [2]. For each of three output types (full six degrees of freedom (6-DoF), Cartesian translation, and transitional scale), a baseline network with only image pair input is compared with a nearly identical architecture that is also given an additional rotation estimate such as from an Inertial Navigation System (INS). The inertially-aided networks show an order of magnitude improvement over the …
Microturbine Turbojets: Experimental Evaluation Of Commercially Available Engines, Richard A. Depaola Iii
Microturbine Turbojets: Experimental Evaluation Of Commercially Available Engines, Richard A. Depaola Iii
Theses and Dissertations
This research assessed the performance of commercial microturbine turbojets and was the first industry-wide investigation into this class of engine by AFRL's SERL. Four commercial engines of the same thrust class were evaluated for overall and component-level performance. In addition to providing an evaluation of existing systems, the maximum performance for a commercial turbojet was predicted based on component evaluations. This analysis indicated that a commercial turbojet could have comparable thrust performance to a similarly sized military-grade engine, but it is unlikely that commercial engines can achieve the SFC of military engines without upgrading the compressors found in commercial microturbines.
Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen
Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen
Theses and Dissertations
Laser shock peening (LSP) is a form of work hardening by means of laser induced pressure impulse. LSP imparts compressive residual stresses which can improve fatigue life of metallic alloys for structural use. The finite element modeling (FEM) of LSP is typically done by applying an assumed pressure impulse, as useful experimental measurement of this pressure impulse has not been adequately accomplished. This shortfall in the field is a current limitation to the accuracy of FE modeling, and was addressed in the current work. A novel method was tested to determine the pressure impulse shape in time and space by …
Design, Development, And Testing Of A Low Cost, Additively-Manufactured, Centrifugal Compressor, Aaron P. Bauer
Design, Development, And Testing Of A Low Cost, Additively-Manufactured, Centrifugal Compressor, Aaron P. Bauer
Theses and Dissertations
The three objectives of this research were to: 1.) design, build, and test AM compressors to substitute into COTS micro-gas turbine engines, 2.) provide initial correlations between FEA and compressor failure speed, and 3.) characterize the effects of AM on compressor performance. These goals improved the design cycle cost and the design-validation time cycle. ULTEM 9085, 300-AMB, and Onyx-Kevlar temperature-dependent tensile properties were measured. FEA-predicted failure speeds of stock compressor designs led design improvements, potentially fulfilling the original compressor requirements. Physical testing of the stock and ULTEM 9085 compressors occurred. Comparing these compressors' performances demonstrated that low cost, AM materials …
Solution Anneal Heat Treatments To Enhance Mechanical Performance Of Additively Manufactured Inconel 718, David J. Newell
Solution Anneal Heat Treatments To Enhance Mechanical Performance Of Additively Manufactured Inconel 718, David J. Newell
Theses and Dissertations
The nickel-based superalloy Inconel 718 (IN718) is an excellent candidate among aerospace alloys for laser powder-bed fusion (LPBF) manufacturing. As-built LPBF IN718 has a vertically aligned columnar (001) microstructure which translates into orthotropic mechanical behavior. The post-process heat treatments for IN718 were developed 60 years ago for wrought and cast processes and do not mitigate the columnar microstructure of the LPBF process. Recrystallization is required to remove the columnar microstructure, which would allow for parts to be fabricated on different machines or in different orientations but still achieve the same properties. This research investigated the microstructure of LPBF IN718 as …
Development Of A Small Scale Rotating Detonation Engine, Joseph R. Dechert
Development Of A Small Scale Rotating Detonation Engine, Joseph R. Dechert
Theses and Dissertations
The Rotating Detonation Engine (RDE) has been researched extensively in recent years, but the minimum size limits of an RDE have not been well investigated. The goal of this research was to build an RDE small enough to produce a detonation frequency above 20 kHz with a single detonation wave while also reducing the engine's mass ow rate. An engine with these design characteristics would reduce hazards associated with previous RDE testing. This research objective resulted in the design of an RDE with an outer diameter sized at 28 mm using ethylene and nitrous oxide as a fuel and oxidizer. …
The Effect Of Passive And Active Boundary-Layer Fences On Delta Wing Performance At Low Reynolds Number, Anna C. Demoret
The Effect Of Passive And Active Boundary-Layer Fences On Delta Wing Performance At Low Reynolds Number, Anna C. Demoret
Theses and Dissertations
The effect of passive and active boundary-layer fences (BLFs) on performance is evaluated on a NACA 0012 delta wing (croot = 14in, ctip = 2.8in, Λ = 45°, b = 23.5in) at a Reynolds number (Re) of 5.0 x 105 based on the root chord. The performance improvements of a passive BLF are replicated and improved upon using an active flow control (AFC) fluidic fence created by a wall-normal steady-blowing jet from a slot. The application of a passive BLF at a spanwise location of 70% z/b resulted in an 8.7% increase in CLmax compared to …
Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi, Daniel Holobeny
Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi, Daniel Holobeny
Theses and Dissertations
Ultra Compact Combustors are a novel approach to modern gas turbine combustor designs that look to reduce the overall combustor length and weight. A previous study integrated an Ultra Compact Combustor into a JetCat P90 RXi turbine engine and achieved self-sustained operation with a length savings of 33% relative to the stock combustor. However, that combustor could not operate across the full stock engine performance range due to flameout at increased mass ow rates as reactions were pushed out of the primary zone. To ensure reactions stayed in the primary zone, a new design with a larger combustor volume was …
Detonation Confinement In A Radial Rotating Detonation Engine, Kavi Muraleetharan
Detonation Confinement In A Radial Rotating Detonation Engine, Kavi Muraleetharan
Theses and Dissertations
Radial Rotating Detonation Engines (RRDE) have provided an opportunity for use of a pressure-gain combustor in a more compact form compared to an axial RDE. A successfully tested RRDE has operated over a wide range of test conditions and produced detonation modes with one, two, and three waves. The presence of multiple waves located the detonation waves to the outer radius, while one wave modes operated closer to the inner radius. Locating the detonation wave closer to the inner diameter resulted in less time for combustion prior to the radial turbine. Subsequently, this tended to decrease efficiency. To attempt to …
Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion, Candice R. Roberts
Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion, Candice R. Roberts
Theses and Dissertations
Hybrid composites require further study and testing for future use in various fields. This study focuses on simulating a Hybrid Composite using IM7-977-3 laminae with steel foils in Abaqus under bolt loading by using Hashin and Tsai-Wu failure criterion. Initial simulations contain only the IM7-977-3 composite with cohesive layers. Foil samples were then tested for accurate material properties from which the simulations were then updated to include steel foils. The two models show that Tsai-Wu failure criterion, while great for anisotropic material in tension, does not prove accuracy around the hole of the composite material which is in compression. Hashin …
Space-Based Localization Of Radio Frequency Transmitters Utilizing Macaulay Resultant And Heuristic Optimization Methods, Jessica M. Wightman
Space-Based Localization Of Radio Frequency Transmitters Utilizing Macaulay Resultant And Heuristic Optimization Methods, Jessica M. Wightman
Theses and Dissertations
This research focuses on radio frequency geolocation of space objects utilizing space-based platforms. Geolocation has long been the solution for locating objects. In particular, this study examines the scenario of two cooperative receivers geolocating a transmitter in close proximity. An algorithm is developed to calculate the initial estimated transmitter location and projected orbital trajectory. The algorithm uses the Macaulay method of solving a system of polynomials as well as heuristic optimization techniques to locate a transmitter with respect to receivers at different time intervals. For the scenarios investigated, both Macaulay and heuristic optimization methods achieve initial relative orbit determination.
Design And Analysis Of A Disk-Oriented Engine Combustor, Bennett M. Staton
Design And Analysis Of A Disk-Oriented Engine Combustor, Bennett M. Staton
Theses and Dissertations
In a novel approach to gas-turbine power production, an engine was designed and analyzed to use both a single-stage centrifugal compressor and single-stage radial in- ow turbine configured back-to-back. This air path reduced the axial length of the engine up to 60%, providing additional modularity in a gas-turbine engine that could be used to improve mobility of ground-based power units or increase the survivability of aircraft through the use of distributive propulsion. This increased modularity was made possible by the use of a circumferential ow combustor that substantially decreased the axial length of the burner and negated the need to …
Spacecraft Position Estimation And Attitude Determination Using Terrestrial Illumination Matching, Liberty M. Shockley
Spacecraft Position Estimation And Attitude Determination Using Terrestrial Illumination Matching, Liberty M. Shockley
Theses and Dissertations
An algorithm to conduct spacecraft position estimation and attitude determination via terrestrial illumination matching (TIM) is presented consisting of a novel method that uses terrestrial lights as a surrogate for star fields. Although star sensors represent a highly accurate means of attitude determination with considerable spaceflight heritage, with Global Positioning System (GPS) providing position, TIM provides a potentially viable alternative in the event of star sensor or GPS malfunction or performance degradation. The research defines a catalog of terrestrial light constellations, which are then implemented within the TIM algorithm for position acquisition of a generic spacecraft bus. With the algorithm …
Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams
Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams
Theses and Dissertations
Advanced aerospace applications such as aircraft turbine engine components, hypersonic flight vehicles, and spacecraft reentry thermal protection systems require structural materials that have superior long-term mechanical properties under high temperature, high pressure, and varying environmental factors, such as moisture. Because of their low density, high strength and fracture toughness at high temperatures SiC fiber-reinforced SiC matrix composites are being evaluated for aircraft engine hot-section components. In these applications the composites will be subjected to various types of mechanical loadings at elevated temperatures in oxidizing environments. Because their constituents are intrinsically oxidation-prone, the most significant problem hindering SiC/SiC composites is oxidation …
A Reference Architecture For Cubesat Development, Luke J. Farrell
A Reference Architecture For Cubesat Development, Luke J. Farrell
Theses and Dissertations
Developing a space vehicle is a complex and detailed process, and while CubeSats are smaller and more accessible than traditional satellites the design process is relatively unchanged. Creating a viable space vehicle design requires detailed analysis of a set of mission needs in order to define the mission, with this need set used to then create the specific mission requirements. These requirements are used to formulate a concept of operations, and then move into developing a physical system for executing the mission. The successful production of CubeSats within an organization is contingent upon the accurate execution of the general CubeSat …
Evaluation Framework For Cislunar Space Domain Awareness (Sda) Systems, Simon R. Knister
Evaluation Framework For Cislunar Space Domain Awareness (Sda) Systems, Simon R. Knister
Theses and Dissertations
Modern space missions are increasingly transiting cislunar space, requiring expansion of existing Space Traffic Management (STM) functions. Legacy Space Domain Awareness (SDA) systems were not purpose-built to detect and track cislunar objects, which could require acquisition of a new system of systems. There are numerous parameters that could be varied for each system, as well as the type and location of systems across the architecture. This research attempts to solve this problem by applying a model-based systems engineering (MBSE) approach to assess the performance and financial burden of a given system of systems. Fitness metrics are developed based upon the …