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Articles 1 - 30 of 99
Full-Text Articles in Aerospace Engineering
Accelerating Machine Learning Inference For Satellite Component Feature Extraction Using Fpgas., Andrew Ekblad
Accelerating Machine Learning Inference For Satellite Component Feature Extraction Using Fpgas., Andrew Ekblad
Theses and Dissertations
Running computer vision algorithms requires complex devices with lots of computing power, these types of devices are not well suited for space deployment. The harsh radiation environment and limited power budgets have hindered the ability of running advanced computer vision algorithms in space. This problem makes running an on-orbit servicing detection algorithm very difficult. This work proposes using a low powered FPGA to accelerate the computer vision algorithms that enable satellite component feature extraction. This work uses AMD/Xilinx’s Zynq SoC and DPU IP to run model inference. Experiments in this work centered around improving model post processing by creating implementations …
A Machine Learning Framework For Automatic Speech Recognition In Air Traffic Control Using Word Level Binary Classification And Transcription, Fowad Shahid Sohail
A Machine Learning Framework For Automatic Speech Recognition In Air Traffic Control Using Word Level Binary Classification And Transcription, Fowad Shahid Sohail
Theses and Dissertations
Advances in Artificial Intelligence and Machine learning have enabled a variety of new technologies. One such technology is Automatic Speech Recognition (ASR), where a machine is given audio and transcribes the words that were spoken. ASR can be applied in a variety of domains to improve general usability and safety. One such domain is Air Traffic Control (ATC). ASR in ATC promises to improve safety in a mission critical environment. ASR models have historically required a large amount of clean training data. ATC environments are noisy and acquiring labeled data is a difficult, expertise dependent task. This thesis attempts to …
Direct Simulation And Reduced-Order Modeling Of Premixed Flame Response To Acoustic Modulation, Zheng Qiao
Direct Simulation And Reduced-Order Modeling Of Premixed Flame Response To Acoustic Modulation, Zheng Qiao
Theses and Dissertations
This dissertation introduces a general, predictive and cost-efficient reduced-order modeling (ROM) technique for characterization of flame response under acoustic modulation. The model is built upon the kinematic flame model–G-equation to describe the flame topology and dynamics, and the novelties of the ROM lie in i) a procedure to create the compatible base flow that can reproduce the correct flame geometry and ii) the use of a physically-consistent acoustic modulation field for the characterization of flame response. This ROM addresses the significant limitations of the classical kinematic model, which is only applicable to simple flame configurations and relies on ad-hoc models …
Double Cone Flow Field Reconstruction Between Mach 4 And 12 Using Machine Learning Techniques, Trevor A. Toros
Double Cone Flow Field Reconstruction Between Mach 4 And 12 Using Machine Learning Techniques, Trevor A. Toros
Theses and Dissertations
No abstract provided.
One Dimensional Study Of Magnetoplasmadynamic Thrusters For A Potential New Class Of Heavy Ion Drivers For Plasma Jet Driven Magnetoinertial Fusion, Patrick M. Brown
One Dimensional Study Of Magnetoplasmadynamic Thrusters For A Potential New Class Of Heavy Ion Drivers For Plasma Jet Driven Magnetoinertial Fusion, Patrick M. Brown
Theses and Dissertations
Plasma Jet Driven Magnetoinertial Fusion (PJMIF) requires high velocity heavy ion drivers in order to compress a magnetized target to fusion conditions. Previous work with heavy ion drivers has revealed sub-par accelerations due to plasma instabilities; thus, it is necessary to investigate new methods of heavy ion plasma acceleration. One such method is Magnetoplasmadynamic (MPD) thrusters. Past studies of these thrusters have been conducted at an initial temperature at or below the energy of full ionization. Here MPD thrusters are investigated using a Godunov type MHD solver with a Harten-Lax van Leer-D (HLLD) flux solving scheme assuming the plasma is …
Impendance Probe Payload Development For Space-Based Joint Service Collaboration, Brian T. Kay
Impendance Probe Payload Development For Space-Based Joint Service Collaboration, Brian T. Kay
Theses and Dissertations
Collaborations utilizing small spacecraft in near earth orbit between the U. S. Coast Guard Academy (CGA), Naval Research Lab (NRL), the U. S. Naval Academy (USNA), and the Air Force Institute of Technology (AFIT) have initiated scientific and engineering space-based experiments. Sourced opportunities like the VaSpace ThinSat missions have provided a platform for payload, sensor, and experiment development that would have otherwise been resource prohibitive. We have constructed an impedance probe payload derived from the existing ‘Space PlasmA Diagnostic suitE’ (SPADE) mission operating from NASA’s International Space Station. Currently both space and laboratory plasmas are investigated with AC impedance measurements …
A Cyber Threat Taxonomy And A Viability Analysis For False Injections In The Tcas, John W. Hannah
A Cyber Threat Taxonomy And A Viability Analysis For False Injections In The Tcas, John W. Hannah
Theses and Dissertations
This thesis provided background information on the Traffic Collision Avoidance System (TCAS). Additionally, the thesis developed a threat taxonomy for TCAS, resulting in the determination that a false injection attack presents the most comprehensive risk. Moreover, the thesis presents the development of a program to determine what ranges, altitudes, and relative bearings are most vulnerable to a false injection attack. The program includes test for all requirements of a successful false injection. Furthermore, the thesis presents an analysis of results and creates threat maps as situational awareness tools. Lastly, the thesis discusses potential solutions to the false injection attack, covers …
A Framework For Autonomous Cooperative Optimal Assignment And Control Of Satellite Formations, Devin E. Saunders
A Framework For Autonomous Cooperative Optimal Assignment And Control Of Satellite Formations, Devin E. Saunders
Theses and Dissertations
A decentralized, cooperative multi-agent optimal control framework is presented to offer a solution to the assignment and control problems associated with performing multi-agent tasks in a proximity operations environment. However, the framework developed may be applied to a variety domains such as air, space, and sea. The solution presented takes advantage of a second price auction assignment algorithm to optimally task each satellite, while model predictive control is implemented to control the agents optimally while adhering to safety and mission constraints. The solution is compared to a pseudospectral collocation method, and a study on tuning parameters is included.
Neuromorphic Vision Sensors For Space-Based Applications, Jessica L. Horn
Neuromorphic Vision Sensors For Space-Based Applications, Jessica L. Horn
Theses and Dissertations
This research examines the viability of event-based vision (neuromorphic) sensors for future use on satellites. Outputting single pixel events only when a change in intensity is detected, event-based vision sensors offer a potential low power, low latency, high temporal resolution, and high dynamic range solution as compared to traditional CCD or CMOS camera technology. The commercial off-the-shelf DVS240C sensor, is analyzed to determine if operability is affected by launch conditions and the low Earth space environment through vacuum, thermal vacuum, and vibration tests. No appreciable changes in sensor operation was observed throughout testing. Additionally, the sensor was able to detect …
Delayed Authentication System For Civilian Satellite, Sean M. Feschak
Delayed Authentication System For Civilian Satellite, Sean M. Feschak
Theses and Dissertations
This thesis presents the feasibility of a Delayed Authentication System (DAS) for civilian satellite navigation (satnav) receivers. In satnav systems, encrypted signal components are transmitted synchronously with civilian components. Hence, the civilian signals can be authenticated by detecting the presence of encrypted signal components within the received signal. To authenticate, a reference station transmits estimated encrypted signal spreading code symbols processed using a high gain antenna. In this thesis, it is shown that a 1-meter diameter dish antenna is adequate to provide a high probability of successful authentication, thereby reducing overall system complexity and cost.
Optimizing A Bank Of Kalman Filters For Navigation Integrity, Luis E. Sepulveda
Optimizing A Bank Of Kalman Filters For Navigation Integrity, Luis E. Sepulveda
Theses and Dissertations
Alternative navigation is an area of research which employs a variety of sensor technologies to provide a navigation solution in Global Navigation Satellite System degraded or denied environments. The Autonomy and Navigation Technology Center at the Air Force Institute of Technology has recently developed the Autonomous and Resilient Management of All-source Sensors (ARMAS) navigation framework which utilizes an array of Kalman Filters to provide a navigation solution resilient to sensor failures. The Kalman Filter array size increases exponentially as system sensors and detectable faults are scaled up, which in turn increases the computational power required to run ARMAS in areal-world …
Low-Cost Terrestrial Demonstration Of Autonomous Satellite Proximity Operations, Zackary R. Hewitt
Low-Cost Terrestrial Demonstration Of Autonomous Satellite Proximity Operations, Zackary R. Hewitt
Theses and Dissertations
The lack of satellite servicing capabilities significantly impacts the development and operation of current orbital assets. With autonomous solutions under consideration for servicing, the purpose of this research is to build and validate a low-cost hardware platform to expedite the development of autonomous satellite proximity operations. This research aims to bridge the gap between simulation and existing higher fidelity hardware testing with an affordable alternative. An omnidirectional variant of the commercially available TurtleBot3 mobile robot is presented as a 3-DOF testbed that demonstrates a satellite servicing inspection scenario. Reference trajectories for the scenario are generated via optimal control using the …
Nebulizer-Based Systems To Improve Pharmaceutical Aerosol Delivery To The Lungs, Benjamin M. Spence
Nebulizer-Based Systems To Improve Pharmaceutical Aerosol Delivery To The Lungs, Benjamin M. Spence
Theses and Dissertations
Combining vibrating mesh nebulizers with additional new technologies leads to substantial improvements in pharmaceutical aerosol delivery to the lungs across therapeutic administration methods. In this dissertation, streamlined components, aerosol administration synchronization, and/or Excipient Enhanced Growth (EEG) technologies were utilized to develop and test several novel devices and aerosol delivery systems. The first focus of this work was to improve the poor delivery efficiency, e.g., 3.6% of nominal dose (Dugernier et al. 2017), of aerosolized medication administration to adult human subjects concurrent with high flow nasal cannula (HFNC) therapy, a form of continuous-flow non-invasive ventilation (NIV). The developed Low-Volume Mixer-Heater (LVMH) …
Electro-Optic Satellite Constellation Design Using Multi-Objective Genetic Algorithm, Yasin Tamer
Electro-Optic Satellite Constellation Design Using Multi-Objective Genetic Algorithm, Yasin Tamer
Theses and Dissertations
Satellite constellation design is a complex, highly constrained, and multidisciplinary problem. Unless optimization tools are used, tradeoffs must be conducted at the subsystem level resulting in feasible, but not necessarily optimal, system designs. As satellite technology advances, new methods to optimize the system objectives are developed. This study is based on the development of a representative regional remote sensing constellation design. This thesis analyses the design process of an electrooptic satellite constellation with regional coverage considerations using system-level optimization tools. A multi objective genetic algorithm method is used to optimize the constellation design by utilizing MATLAB and STK integration. Cost, …
Chronos Spacecraft With Chiron Probe: Exploration Of The Hydrosphere, Principle Satellites, Atmosphere, And Rings Of Uranus, Payton E. Pearson
Chronos Spacecraft With Chiron Probe: Exploration Of The Hydrosphere, Principle Satellites, Atmosphere, And Rings Of Uranus, Payton E. Pearson
Theses and Dissertations
A design reference mission using more modern technological innovations has been developed for exploration of the outer reaches of our Solar System, specifically Uranus and its system of satellites. This mission will utilize theoretical technologies mostly without regard to their current technological readiness level (TRL), though most systems have a TRL of at least 5. The primary innovations explored in this thesis are the new launch systems that provide far greater payload capacity potentially sent to anywhere in the Solar System, new Stirling-engine radioisotope thermoelectric generators (SRTGs), vastly improved data storage technologies, optimized satellite antenna relay of data using much …
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 …
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, …
Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit
Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit
Theses and Dissertations
The commercial-off-the-shelf small Unmanned Aerial Vehicle (UAV) market is expanding rapidly in response to interest from hobbyists, commercial businesses, and military operators. The core commercial mission set directly relates to many current military requirements and strategies, with a priority on short range, low cost, real time aerial imaging, and limited modular payloads. These small vehicles present small radar cross sections, low heat signatures, and carry a variety of sensors and payloads. As with many new technologies, security seems secondary to the goal of reaching the market as soon as innovation is viable. Research indicates a growth in exploits and vulnerabilities …
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 …
The Impact Of Changing The Size Of Aircraft Radar Displays On Visual Search In The Cockpit, Justin R. Marsh
The Impact Of Changing The Size Of Aircraft Radar Displays On Visual Search In The Cockpit, Justin R. Marsh
Theses and Dissertations
Advances in sensor technology have enabled our fighter aircraft to find, fix, track, target, engage (F2T2E) at greater distances, providing the operator with more data within the battlefield. Modern aircraft are designed with larger displays while our legacy aircraft are being retrofitted with larger cockpit displays to enable display of the increased data. While this modification has been shown to enable improvements in human performance of many cockpit tasks, this effect is often not measured nor fully understood at a more generalizable level. This research outlines an approach to comparing human performance across two display sizes in future F-16 cockpits. …
Performance Analysis Of Angle Of Arrival Algorithms Applied To Radiofrequency Interference Direction Finding, Taylor S. Barber
Performance Analysis Of Angle Of Arrival Algorithms Applied To Radiofrequency Interference Direction Finding, Taylor S. Barber
Theses and Dissertations
Radiofrequency (RF) interference threatens the functionality of systems that increasingly underpin the daily function of modern society. In recent years there have been multiple incidents of intentional RF spectrum denial using terrestrial interference sources. Because RF based systems are used in safety-of-life applications in both military and civilian contexts, there is need for systems that can quickly locate these interference sources. In order to meet this need, the Air Force Research Laboratory Weapons Directorate is sponsoring the following research to support systems that will be able to quickly geolocate RF interferers using passive angle-of-arrival estimation to triangulate interference sources. This …
Piezoelectric Sensor Crack Detection On Airframe Systems, Kevin J. Lin
Piezoelectric Sensor Crack Detection On Airframe Systems, Kevin J. Lin
Theses and Dissertations
In 2008, the Department of Defense published a guidebook for a methodology named Condition-Based Maintenance Plus (CBM+) which capabilities include improving productivity, shortening maintenance cycles, lowering costs, and increasing availability and reliability. This push replaces existing inspection criteria, often conducted as non-destructive testing (NDT), with structural health monitoring (SHM) systems. The SHM system addressed utilizes guided Lamb waves generated by piezoelectric wafer active sensors (PWAS) to detect the existence, size, and location of damage from through-thickness cracks around a rivet hole. The SHM field lacks an experiment testing how small changes in receiver sensor distances affect damage detection. In addition, …
Cyber-Attack Drone Payload Development And Geolocation Via Directional Antennae, Clint M. Bramlette
Cyber-Attack Drone Payload Development And Geolocation Via Directional Antennae, Clint M. Bramlette
Theses and Dissertations
The increasing capabilities of commercial drones have led to blossoming drone usage in private sector industries ranging from agriculture to mining to cinema. Commercial drones have made amazing improvements in flight time, flight distance, and payload weight. These same features also offer a unique and unprecedented commodity for wireless hackers -- the ability to gain ‘physical’ proximity to a target without personally having to be anywhere near it. This capability is called Remote Physical Proximity (RPP). By their nature, wireless devices are largely susceptible to sniffing and injection attacks, but only if the attacker can interact with the device via …
Investigation Of Endwall Vortex Manipulation In High Lift Turbines Caused By Active Endwall Forcing, Horatio J. Babcock
Investigation Of Endwall Vortex Manipulation In High Lift Turbines Caused By Active Endwall Forcing, Horatio J. Babcock
Theses and Dissertations
With the increased demand for lighter, more fuel efficient and smaller gas turbine engines, the impetus to reduce the weight and size of the turbine has become apparent. One approach to reduce this weight is to reduce the number of blades in the turbine. However, to maintain power output, each blade must be capable of supporting a greater amount of lift. While several high-lift turbine profiles have been detailed in literature, most of these profiles have increased endwall losses, despite their desirable mid-span characteristics. To mitigate this endwall loss, a number of active and passive flow approaches have been studied …
Initial Stage Of Fluid-Structure Interaction Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Dustin P. Graves
Initial Stage Of Fluid-Structure Interaction Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Dustin P. Graves
Theses and Dissertations
The analysis of a celestial icosahedron geometry is considered as a potential design for a Vacuum Lighter than Air Vehicle (VLTAV). The goal of the analysis is ultimately to understand the initial fluid-structure interaction of the VLTAV and the surrounding airflow. Up to this point, previous research analyzed the celestial icosahedron VLTAV in relation to withstanding a symmetric sea-level pressure applied to the membrane of the structure. This scenario simulates an internal vacuum being applied in the worst-case atmospheric environmental condition. The next step in analysis is to determine the aerodynamic effects of the geometry. The experimental setup for obtaining …
Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco
Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco
Theses and Dissertations
Computational aerothermodynamic analysis is presented for a spacecraft in low Earth orbit performing an atmospheric skip entry maneuver. Typically, atmospheric reentry is a terminal operation signaling mission end-of-life and, in some instances, executed for spacecraft disposal. A variation on reentry – skip entry – is an aeroassisted trans-atmospheric maneuver in which a spacecraft utilizes the effects of aerodynamic drag in order to reduce energy prior to a terminal entry, pinpoint a targeted entry, or change orbital elements such as inclination. Spacecraft performing a skip entry enable new modes of maneuver to enhance operations in nominal or possibly contested mission environments. …
Direct Numerical Simulation Of Roughness Induced Hypersonic Boundary Layer Transition On A 7° Half-Angle Cone, Tara E. Crouch
Direct Numerical Simulation Of Roughness Induced Hypersonic Boundary Layer Transition On A 7° Half-Angle Cone, Tara E. Crouch
Theses and Dissertations
Direct numerical simulation (DNS) computational fluid dynamic (CFD) calculations were performed on a 30° slice of 7° half-angle cones with increasing nose radii bluntness at Mach 10 while simulating a distributed roughness pattern on the cone surface. These DNS computations were designed to determine if the non-modal transition behavior observed in testing performed at the Arnold Engineering Development Center (AEDC) Hypervelocity Wind Tunnel 9 was induced via distributed surface roughness. When boundary layer transition is dominated by second mode instabilities, an increase in nose radius delays the transition location downstream. However, blunt nose experiments indicated that as the nose radius …
Control Strategies For Multi-Evaporator Vapor Compression Cycles, Sunderlin D. Jackson
Control Strategies For Multi-Evaporator Vapor Compression Cycles, Sunderlin D. Jackson
Theses and Dissertations
Next-generation military aircraft must be able to handle highly transient thermal loads that exceed the ability of current aircraft thermal subsystems. Vapor compression cycle systems are a particular refrigeration technology that is an attractive solution for dealing with this challenge, due primarily to their high efficiency. However, there are several barriers to realizing the benefits of vapor cycles systems for controlling thermal loads in military aircraft. This thesis focuses on addressing the challenge of controlling vapor cycles in the presence of highly transient evaporator heat loads. Specifically, a linear quadratic regulator (LQR) is designed for a simple vapor cycle system, …
Schlieren Imaging And Flow Analysis On A Cone/Flare Model In The Afrl Mach 6 Ludwieg Tube Facility, David A. Labuda
Schlieren Imaging And Flow Analysis On A Cone/Flare Model In The Afrl Mach 6 Ludwieg Tube Facility, David A. Labuda
Theses and Dissertations
High-speed Schlieren photography was utilized to visualize flow in the Air Force Research Laboratory Mach 6 Ludwieg tube facility. A 7° half-angle cone/flare model with variable nosetip radius and flare angle options was used in the study. Testing was performed at two driver tube pressures, generating freestream Reynolds numbers of 10.0x106 and 19.8x106 per meter. The variable-angle flare portion of the model provided a method for adjusting the intensity of the adverse pressure gradient at the cone/flare junction. As expected from existing literature, boundary layer separation along the cone frustum occurred further upstream as the magnitude of the …