Aerospace Engineering Commons^™

Damage Control Measures In Composites: Focus On Damage Tolerance Of Aerospace Structures, Kais Jribi

Doctoral Dissertations and Master's Theses

Barely Visible Impact Damage (BVID) in composite materials presents a stealthy yet significant risk to structural integrity, particularly challenging due to its elusive nature. The approach adopted here diverges from traditional methodologies, focusing on the novel application of Digital Image Correlation (DIC) to map surface area changes during in-situ Compression After Impact (CAI) tests. This technique allows for an in-depth analysis of planar strains along the x and y axes, shedding light on the material's behavior under stress.

A pivotal advancement lies in developing a method for precisely identifying when BVID-induced delamination recommences. By meticulously analyzing strain pattern deviations along …

Stochastic Point Process Modeling For Engineering Applications, Samarth Motagi

Doctoral Dissertations and Master's Theses

Hawkes model or self-exciting point process model is a branching point process model. The model classifies the dataset of discrete events to background and offspring events. It has been used to study interconnected events in many fields, but relatively little work exists in applying these concepts to engineering problems. In our research, we use a self-exciting point process model for two engineering applications: (a) To identify secondary crashes from a given traffic data and (b) To quantify the agglomeration state and size of nanoparticles from computationally generated carbon nanotube microstructure using stochastic percolation model and experimentally generated titanium nanoparticle microstructures. …

Deep-Learning Based Multiple-Model Bayesian Architecture For Spacecraft Fault Estimation, Rocio Jado Puente

Doctoral Dissertations and Master's Theses

This thesis presents recent findings regarding the performance of an intelligent architecture designed for spacecraft fault estimation. The approach incorporates a collection of systematically organized autoencoders within a Bayesian framework, enabling early detection and classification of various spacecraft faults such as reaction-wheel damage, sensor faults, and power system degradation.

To assess the effectiveness of this architecture, a range of performance metrics is employed. Through extensive numerical simulations and in-lab experimental testing utilizing a dedicated spacecraft testbed, the capabilities and accuracy of the proposed intelligent architecture are analyzed. These evaluations provide valuable insights into the architecture's ability to detect and classify …

Verification And Validation Of Robot Manipulator Adaptive Control With Actuator Deficiency, Sebastian Comeaux

Doctoral Dissertations and Master's Theses

This work addresses the joint tracking problem of robotic manipulators with uncertain dynamical parameters and actuator deficiencies, in the form of an uncertain control effectiveness matrix, through adaptive control design, simulation, and experimentation. Specifically, two novel adaptive controller formulations are implemented and tested via simulation and experimentation. The proposed adaptive control formulations are designed to compensate for uncertainties in the dynamical system parameters as well as uncertainties in the control effectiveness matrix that pre-multiplies the control input. The uncertainty compensation of the dynamical parameters is achieved via the use of the desired model compensation–based adaptation, while the uncertainties related to …

Artificial Intelligence-Assisted Inertial Geomagnetic Passive Navigation, Andrei Cuenca

Doctoral Dissertations and Master's Theses

In recent years, the integration of machine learning techniques into navigation systems has garnered significant interest due to their potential to improve estimation accuracy and system robustness. This doctoral dissertation investigates the use of Deep Learning combined with a Rao-Blackwellized Particle Filter for enhancing geomagnetic navigation in airborne simulated missions.

A simulation framework is developed to facilitate the evaluation of the proposed navigation system. This framework includes a detailed aircraft model, a mathematical representation of the Earth's magnetic field, and the incorporation of real-world magnetic field data obtained from online databases. The setup allows an accurate assessment of the performance …

Comparative Evaluation Of Propulsive Power Transmission Technologies For High-Speed Vertical Takeoff And Landing (Hsvtol) Cargo Aircraft, Xinyu Yang

Doctoral Dissertations and Master's Theses

Designing High-Speed Vertical Takeoff and Landing (HSVTOL) cargo aircraft capable of both low downwash velocity hovering and high subsonic speed cruising presents a significant engineering challenge. This challenge, stemming from conflicting design requirements, has been substantially influenced by recent technological advancements, which have offered greater flexibility in rotor placement. Consequently, this has led to the emergence of innovative mission-specific designs that hold the potential to outperform traditional concepts. The central objective of this study is to evaluate the benefits of modern technologies for VTOL cargo aircraft and assess their performance relative to baseline VTOL aircraft. The results of this comparative …

Development Of A Constellation Simulator For A 5g/Iot Mission Planning System, Franco Criscola

Doctoral Dissertations and Master's Theses

The advancement of 5G and Internet-of-Things technologies has presented new challenges for telecommunications providers. One of the challenges is integrating these technologies with present networks. A solution has been found in low-Earth orbit satellite constellations. On one hand, this method increases coverage and reduces costs, but on the other it raises new problems like how to efficiently manage large constellations of spacecraft. This thesis introduces the Constellation Management System, developed in collaboration with i2Cat foundation. This novel tool is composed of two modules: the simulator and the scheduler. The former propagates satellite motion and computes visibility events to various targets …

Interfacial Thermomechanical Behavior Of Hybrid Carbon Fibers, Sriraj Srihari

Doctoral Dissertations and Master's Theses

The carbon fiber/epoxy interface is of great importance in composite design due to its load transfer mechanisms from the weak epoxy to the stronger fiber. Improving the strength of the interface reduces the risk of failure at the interface and improves the load transfer to the fiber. In this study, two types of nano-species ZnO nanowires and nickel-based metal organic frameworks were grown on carbon fibers to improve the interfaces. The interfacial mechanics of the enhanced fibers are evaluated using nanoindentation studies. Composite samples with Aeropoxy matrix and vertically aligned fibers are fabricated for this purpose. A Bruker TI-980 TriboIndenter …

Online Aircraft System Identification Using A Novel Parameter Informed Reinforcement Learning Method, Nathan Schaff

Doctoral Dissertations and Master's Theses

This thesis presents the development and analysis of a novel method for training reinforcement learning neural networks for online aircraft system identification of multiple similar linear systems, such as all fixed wing aircraft. This approach, termed Parameter Informed Reinforcement Learning (PIRL), dictates that reinforcement learning neural networks should be trained using input and output trajectory/history data as is convention; however, the PIRL method also includes any known and relevant aircraft parameters, such as airspeed, altitude, center of gravity location and/or others. Through this, the PIRL Agent is better suited to identify novel/test-set aircraft.

First, the PIRL method is applied to …

Rigid Body Constrained Motion Optimization And Control On Lie Groups And Their Tangent Bundles, Brennan S. Mccann

Doctoral Dissertations and Master's Theses

Rigid body motion requires formulations where rotational and translational motion are accounted for appropriately. Two Lie groups, the special orthogonal group SO(3) and the space of quaternions H, are commonly used to represent attitude. When considering rigid body pose, that is spacecraft position and attitude, the special Euclidean group SE(3) and the space of dual quaternions DH are frequently utilized. All these groups are Lie groups and Riemannian manifolds, and these identifications have profound implications for dynamics and controls. The trajectory optimization and optimal control problem on Riemannian manifolds presents significant opportunities for theoretical development. Riemannian optimization is an attractive …

The Influence Of Mixing Duct Length And Phase Of Flight On Wall Temperatures Of A Rocket Based Combined Cycle Engine In Ejector And Air-Augmented Modes, Jonathan Grow

Doctoral Dissertations and Master's Theses

Rocket Based Combined Cycle (RBCC) engines have been theorized as a possible means of powering launch vehicles and high-speed atmospheric vehicles. By incorporating aspects of both air-breathing and rocket propulsion, RBCC engines promise up to a 230 % increase in specific impulse over traditional chemical rocket propulsion by entraining a secondary flow of atmospheric air and mixing it with the exhaust of a rocket motor. Students within the Embry-Riddle Future Space Explorers and Developers Society (ERFSEDS) identified a
problem of excessive heating and structural failure of the mixing duct during launch and transonic flight of a student-built flight test vehicle. …

Neural Network Models For Generating Synthetic Flight Data, Nathaniel Sisson

Doctoral Dissertations and Master's Theses

Flight test data is a valuable resource used in many aerospace applications. However, procuring a sufficiently large database of flight test data poses several challenges. Nominal flight tests can be expensive and time-consuming and require much post-processing depending on the availability of sensors and the quality of the sensor output. Flight test performed outside of nominal flight conditions, or flight tests in which failures are introduced, add to the inherent risk and danger associated with flight tests. The most popular alternative to flight test, numerical simulations, may fail to fully capture all non-linear behavior. While flight tests will always be …

In-Situ Thermal And Deformation Characterization Of Additive Manufacturing Processes, Nicholas Phillips

Doctoral Dissertations and Master's Theses

Additive manufacturing (AM) is a rapidly growing industry with numerous applications in the aerospace industry such as aircraft parts and emergency tools on the International Space Station. Defects in additively manufactured structures, however, can waste a lot of time and money. Being able to monitor the manufacturing process for defects is one of the first steps which can be taken to mitigate these losses. This study focuses on the use of thermography in conjunction with deep learning to identify flaws during 3D printing of composite structures made using Onyx, a mixture of chopped carbon fiber and nylon, composite prints. In …

Modeling, Control, And Hardware Development Of A Thrust-Vector Coaxial Uav, Andrew North

Doctoral Dissertations and Master's Theses

This thesis introduces a unique thrust vector coaxial unmanned aerial vehicle (UAV) configuration and presents a comprehensive investigation encompassing dynamics modeling, hardware design, and controller development. Using the Newton-Euler method, a dynamic model for the UAV is derived to gain in-depth insights into its fundamental flight characteristics. A simple thrust model is formulated and modified by comparing it with data obtained from vehicle testing. The feasibility of manufacturing such a vehicle is assessed through the development of a hardware prototype. Finally, a linear state feedback controller is designed and evaluated using the non-linear dynamics model. The results demonstrate successful validation …

An Online Adaptive Machine Learning Framework For Autonomous Fault Detection, Nolan Coulter

Doctoral Dissertations and Master's Theses

The increasing complexity and autonomy of modern systems, particularly in the aerospace industry, demand robust and adaptive fault detection and health management solutions. The development of a data-driven fault detection system that can adapt to varying conditions and system changes is critical to the performance, safety, and reliability of these systems. This dissertation presents a novel fault detection approach based on the integration of the artificial immune system (AIS) paradigm and Online Support Vector Machines (OSVM). Together, these algorithms create the Artificial Immune System augemented Online Support Vector Machine (AISOSVM).

The AISOSVM framework combines the strengths of the AIS and …

Online Estimation Of Unknown Parameters For Flexible Spacecraft, Nicolo Woodward

Doctoral Dissertations and Master's Theses

Attitude controls methods of highly flexible spacecraft have seen increased interest over the last decades thanks to the technological development of flexible solar panels and deploy-ables, which improves the capabilities of small satellites. However, a high-fidelity model of the flexible mode dynamics is hard to obtain in on-ground testing because not all modes of frequencies can be observed, complicating the controller design. Furthermore, plastic deformations due to long periods of storage of stowed flexible components could result in exciting frequencies outside of the designed controller’s bandwidth, leading to an uncontrollable system. This thesis proposes a method to develop a high-fidelity …

Solar Sailing Adaptive Control Using Integral Concurrent Learning For Solar Flux Estimation, Luis Mendoza Zambrano

Doctoral Dissertations and Master's Theses

In the interest of exploiting natural forces for propellant-less spacecraft missions, this thesis proposes an adaptive control strategy to account for unknown parameters in the dynamic modeling of a reflectivity-controlled solar sail spacecraft. A Lyapunov-based control law along with integral concurrent learning is suggested to accomplish and prove global exponential tracking of the estimated parameters and states of interest, without satisfying the common persistence of excitation condition, which in most nonlinear systems cannot be guaranteed a priori. This involves estimating the solar flux or irradiance from the Sun to account for uncertainty and variation over time in this value. To …

Characterization Of Bistability Behavior In Unsymmetric Cfrp Laminates, Evan Medora

Doctoral Dissertations and Master's Theses

Composite laminates of unsymmetric layup families often exhibit twin stable shapes at room temperature, a phenomenon known as bistability. Unsymmetric bistable composite laminates have often been suggested for applications in aerospace morphing structures, damping, and energy storage, because of their ability to easily change their shape while being homogenized with the rest of the composite structure.

This study analyzes the mechanisms responsible for bistability in unsymmetrical [0/0/90/90] laminates through a combination of experiments and modeling. Several unsymmetrical laminates with different aspect ratios were fabricated using autoclave processing. Digital image correlation (DIC) is used to monitor laminate strains in situ during …

Autonomous Space Surveillance For Arbitrary Domains, David Zuehlke

Doctoral Dissertations and Master's Theses

Space is becoming increasingly congested every day and the task of accurately tracking satellites is paramount for the continued safe operation of both manned and unmanned space missions. In addition to new spacecraft launches, satellite break-up events and collisions generate large amounts of orbital debris dramatically increasing the number of orbiting objects with each such event. In order to prevent collisions and protect both life and property in orbit, accurate knowledge of the position of orbiting objects is necessary. Space Domain Awareness (SDA) used interchangeably with Space Situational Awareness (SSA), are the names given to the daunting task of tracking …

Small Unmanned Aircraft Systems: Operator Workload And Situation Awareness Utilizing First Person View Techniques, Ross Lucas Stephenson Jr

Doctoral Dissertations and Master's Theses

The small, unmanned aircraft systems (sUAS) sector within the aviation industry is experiencing unprecedented growth. However, the regulatory guidance for the safe integration of sUAS into the National Airspace System (NAS) has not kept pace with this technological growth within the market. Current regulatory limitations of line-of-sight operations may have an impact on the establishment of an equivalent level of safety for sUAS operations as maintained by manned aircraft. The focal point of the discussion of line-of-sight operations has been the ability of the sUAS pilot to see and avoid all obstacles and other aircraft in a safe and timely …

Impact Resistance Of Hybrid Metal-Organic Frameworks/Carbon Fibers Composites, Derek Isaac Espinosa Ramirez

Doctoral Dissertations and Master's Theses

The increase in the use of carbon fiber-reinforced polymers (CFRPs) composites in the aerospace industry generated the need of improving the properties and capabilities of these composites by adding nano-reinforcements to the carbon fibers, also called hybrid fiber reinforced polymer composites. In this study, the energy absorption due to impact at low speed will be tested and simulated in four configurations of CFRPs utilizing the same [0/90]_S layout throughout them.

The carbon fiber configurations used during this study are de-sized, acid-activated, metal-organic frameworks (MOF), and carbon nanotubes (CNTs). Nickel (II) Nitrate, Methylimidazole, and Methanol were used to grow the …

The Role Of Slip System Activation On Ni-Based Superalloy High Temperature Fatigue, Alexandru Lopazan

Doctoral Dissertations and Master's Theses

Nickel-based superalloys are used extensively in the aviation industry, particularly in aircraft engine components. These materials are desirable due to their high strength, resistance to creep, corrosive environment, and high temperature. It has been well documented that material fatigue is characterized by material microstructure, type of loading, and other parameters. Currently, research into the effects of fatigue on complex materials like nickel-based superalloys is being pursued. Previous research has found that preconditioning of Inconel 718 samples at 700 ℃ with 1.0% strain led to an improved fatigue life. It has been suggested that this could be caused by the activation …

Nonlinear Dynamics Analysis And Control Of Space Vehicles With Flexible Structures, Marco Fagetti

Doctoral Dissertations and Master's Theses

Space vehicles that implement hardware such as antennas, solar panels, and other extended appendages necessary for their respective missions must consider the nonlinear rotational and vibrational dynamics of these flexible structures. Formulation and analysis of these flexible structures must account for the rigid-flexible coupling present in the system dynamics for stability analysis and control design. The system model is represented by a flexible appendage attached to a central rigid body, where the flexible appendage is modeled as a cantilevered Euler-Bernoulli beam. Discretization techniques, such as the assumed modes method and the finite element method, are used to model the coupled …

Numerical Modeling Of Synthetic Vortical Disturbance Interactions Using Openfoam, Ahmed Bilal

Doctoral Dissertations and Master's Theses

Nowadays, the number of Advance Air Mobility (AAM) Electic Vertical Take-off and Landing (eVTOL) concepts is rapidly increasing due to their capability of vertical take-off and landing at vertiports located on rooftops of tall urban buildings, which does not require using the ground space in a condensed urban environment. Such flight operations, however, will be greatly affected by the vertiport’s highly unsteady, turbulent flow environment. The goal of this study is to model the turbulent wind interaction with a building to understand the unsteady flow characteristics around vertiports and match the induced unsteady disturbance field to the canonical disturbance forms, …

The Linearized Euler Equations For Predicting Supersonic Jet Noise Of A Rectangular Jet Using Openfoam, Patrick Good

Doctoral Dissertations and Master's Theses

This thesis presents a Linearized Euler Equation (LEE) solver that was developed for OpenFOAM. OpenFOAM is an open-source Computational Fluid Dynamics (CFD) package that is widely used by industry and academia. The LEE’s are a set of equations used in Computational Aeroacoustics (CAA). The LEE’s can solve for the acoustic solution directly and quickly. The solver developed, named leeFoam, was tested against analytical solutions to verify accuracy and then was utilized to predict the acoustics of a heated supersonic rectangular jet. The rectangular jet (RJET) results were compared against experimental data.

The results from this work show that OpenFOAM can …

Optical Orbit Tracking And Estimation, Matthew Gillette

Doctoral Dissertations and Master's Theses

Angles-only initial orbit determination methods are currently limited in their use as they require some prior knowledge of where the observed object will be and when it will be there. This research aims to produce a viable method to automate this process so that objects whose trajectories are not saved in a user’s catalog can be observed. A method is devised using a novel approach to satellite recognition in an image. This method is used in addition to Astrometry to determine the right ascension and declination of the object. This information is then used to either obtain the initial conditions …

A Simulation Of The Impacts Of Climate Change On Civil Aircraft Takeoff Performance, Thomas D. Pellegrin

Doctoral Dissertations and Master's Theses

Climate change affects the near-surface environmental conditions that prevail at airports worldwide. Among these, air density and headwind speed are major determinants of takeoff performance, and their sensitivity to global warming carries potential operational and economic implications for the commercial air transport industry. Previous archival and prospective research observed a weakening in headwind strength and predicted an increase in near-surface temperatures, respectively, resulting in an increase in takeoff distances and weight restrictions. The main purpose of the present study was to update and generalize the extant prospective research using a more representative sample of worldwide airports, a wider range of …

Loss Of Control In-Flight (Loc-I): A Mixed Methods Study Of Voluntary Versus Mandatory Reports From The United States Of America, Roger Lee

Doctoral Dissertations and Master's Theses

Loss of control in flight (LOC-I) is one of modern aviation’s three most prominent fatal accidents. In the United States, air accidents are mandatorily reported to and investigated by the National Transportation Safety Board (NTSB). Established in 1976, the Air Safety Reporting System (ASRS) is a voluntary safety reporting (VSR) system administered by the National Aeronautics and Space Administration (NASA). Over 1.7 million ASRS reports have been processed to date. While the NTSB system handles LOC-I accidents, less severe incidents may have been reported voluntarily through the ASRS.

Safety reporting has been deemed the most valuable activity and the centerpiece …

Prediction & Active Control Of Multi-Rotor Noise, Samuel O. Afari

Doctoral Dissertations and Master's Theses

Significant developments have been made in designing and implementation of Advanced Air Mobility Vehicles (AAMV). However, wider applications in urban areas require addressing several challenges, such as safety and quietness. These vehicles differ from conventional helicopter in that they operate at a relatively lower Reynolds number. More chiefly, they operate with multiples of rotors, which may pose some issues aerodynamically, as well as acoustically. The aim of this research is to first investigate the various noise sources in multi-rotor systems. High-fidelity simulations of two in-line counter-rotating propellers in hover, and in forward flight conditions are performed. Near field flow and …

Health Management And Adaptive Control Of Distributed Spacecraft Systems, Tatiana Alejandra Gutierrez Martinez

Doctoral Dissertations and Master's Theses

As the development of challenging missions like on-orbit construction and collaborative inspection that involve multi-spacecraft systems increases, the requirements needed to improve post-failure safety to maintain the mission performance also increases, especially when operating under uncertain conditions. In particular, space missions that involve Distributed Spacecraft Systems (e.g, inspection, repairing, assembling, or deployment of space assets) are susceptible to failures and threats that are detrimental to the overall mission performance. This research applies a distributed Health Management System that uses a bio-inspired mechanism based on the Artificial Immune System coupled with a Support Vector Machine to obtain an optimized health monitoring …