Aerospace Engineering Commons^™

Space Image Processing And Orbit Estimation Using Small Aperture Optical Systems, David Zuehlke

Doctoral Dissertations and Master's Theses

Angles-only initial orbit determination (AIOD) methods have been used to find the orbit of satellites since the beginning of the Space Race. Given the ever increasing number of objects in orbit today, the need for accurate space situational awareness (SSA) data has never been greater. Small aperture (< 0:5m) optical systems, increasingly popular in both amateur and professional circles, provide an inexpensive source of such data. However, utilizing these types of systems requires understanding their limits. This research uses a combination of image processing techniques and orbit estimation algorithms to evaluate the limits and improve the resulting orbit solution obtained using small aperture systems. Characterization of noise from physical, electronic, and digital sources leads to a better understanding of reducing noise in the images used to provide the best solution possible. Given multiple measurements, choosing the best images for use is a non-trivial process and often results in trying all combinations. In an effort to help autonomize the process, a novel “observability metric” using only information from the captured images was shown empirically as a method of choosing the best observations. A method of identifying resident space objects (RSOs) in a single image using a gradient based search algorithm was developed and tested on actual space imagery captured with a small aperture optical system. The algorithm was shown to correctly identify candidate RSOs in a variety of observational scenarios.

Uncover The Power Of Multipath : Detecting Nlos Drones Using Low-Cost Wifi Devices, Ashok Vardhan Raja

Doctoral Dissertations and Master's Theses

In recent years, consumer UAV technology has seen considerable advances. Consumer UAVs have become an ideal vector for privacy invasions due to their affordability, size, maneuverability, and their ability to stream live high-quality video. There is considerable proliferation of drones in both civil and military domains. Hence it is critical to detect invading unmanned aerial vehicles (UAVs) or drones in a timely manner for both security and safeguarding privacy. Currently available solutions like active radar, video or acoustic sensors are very expensive (especially for individuals) and have considerable constraints (e.g., requiring visual line of sight).

Recent research on drone detection …

Geometric Effects Of Thermal Barrier Coating Damage On Turbine Blade Temperatures, Shane Colon

Doctoral Dissertations and Master's Theses

Thermal barrier coatings (TBC) found on turbine blades are a key element in the performance and reliability of modern gas turbines. During the life of the turbine components, the TBC surface may be damaged due to manufacturing imperfections, handling damage, service spalling, or service impact damage, producing chips in the coating. While a chip in the TBC coating is expected to cause an increase in airfoil temperature, it is unknown to what degree the blade will be affected and what parameters of the chip shape affect this result. The goal of this preliminary study is to identify the major driving …

Non-Linear Bending Analysis Of Functionally Graded Beams With Spring Constraints And Thermal Effects, Swetha Suresh

Doctoral Dissertations and Master's Theses

No abstract provided.

Scale Interactions Within A Perturbed Plane Wall Jet, Shibani Bhatt

Doctoral Dissertations and Master's Theses

The current work focuses on exploiting this behavior to manipulate wall turbulence by targeting the large-scales of the flow. In wall turbulence the large-scales of the flow interact with the smaller scales in a non-linear manner including through a process of amplitude and frequency modulation. A plane wall jet (PWJ) is chosen as the model flow field for this work as its unique geometry allows for the controlled introduction of large-scale perturbations through acoustic forcing. The corresponding interactions because of forcing are characterized using single hot-wire measurements. The nearwall response of the PWJ over a range of large-scale forcing showed …

Shape-Stabilization Of Pcm/Hdpe Composites With 3d-Printing Applications For Battery Thermal Management, Thomas Benjamin Freeman

Doctoral Dissertations and Master's Theses

Phase-change materials (PCMs) are a useful alternative to more traditional methods of thermal management of Li-ion batteries in electric or hybrid-electric vehicles. PCMs are materials which absorb large amounts of latent heat and undergo solid-to-liquid phase change at near-constant temperature. The goal of this thesis is to experimentally investigate the thermal properties of a novel shape-stabilized PCM/HDPE composite extruded filament. The extruded filament can then be used in a 3D printer for custom PCM/HDPE shapes. These custom PCM/HDPE shapes can be used to help reduce weight, energy consumption, and complexity of the thermal management of the ESS. The PCM used …

Design And Implementation Of Intelligent Guidance Algorithms For Uav Mission Protection, Karina Rivera

Doctoral Dissertations and Master's Theses

In recent years, the interest of investigating intelligent systems for Unmanned Aerial Vehicles (UAVs) have increased in popularity due to their large range of capabilities such as on-line obstacle avoidance, autonomy, search and rescue, fast prototyping and integration in the National Air Space (NAS). Many research efforts currently focus on system robustness against uncertainties but do not consider the probability of readjusting tasks based on the remaining resources to successfully complete the mission. In this thesis, an intelligent algorithm approach is proposed along with decision-making capabilities to enhance UAVs post-failure performance. This intelligent algorithm integrates a set of path planning …

Control Driven Scaling Effects Of Motor And Rotors For Urban Air Mobility Design, Agustin A. Giovagnoli

Doctoral Dissertations and Master's Theses

Through this thesis research the problem of controllability and propulsion associated with scaling-up consumer drones to vehicles that may carry significantly larger payloads, including passenger will be analyzed and tested. Controllability is mainly compromised due to the increasing response time of a larger rpm controlled rotor. This requires a more powerful motor, which translates into heavier and larger devices compromising the thrust-to-weight ratio. Collective pitch control at constant rpm is proposed as a first approach to mitigate the controllability problem, and it is tested in a MATLAB Simulink environment. This solution, linked to a Non-linear Dynamic Inversion controller, is simulated …

Design Of An Attitude Control System For A Spacecraft With Propellant Slosh Dynamics, Nolan Coulter

Doctoral Dissertations and Master's Theses

The presence of propellant slosh dynamics in a spacecraft system during a maneuver leads to attitude control system (ACS) performance degradation resulting in attitude tracking errors and instability. As spacecraft missions become more complex and involve longer durations, a substantial propellant mass is required to achieve the mission objectives and perform orbital maneuvers. When the propellant tanks are only partially filled, the liquid fuel moves inside the tanks with translational and rotational accelerations generating the slosh dynamics. This research effort performs a comparative study with different optimal control techniques and a novel application of a model reference artificial immune system …

Variable Fidelity Studies In Wake Vortex Evolution, Safety, And Control, Petr Kazarin

Doctoral Dissertations and Master's Theses

The purpose of this research is to develop a variable-fidelity approach for addressing the safety of unmanned aerial system (UAS) operations in the national aerospace system (NAS). This task is implemented on the basis of safety investigation toolkit for analysis and reporting wake vortex safety system (SITAR WVSS) code, which is a dynamic low-fidelity model addressing generation, evolution, and interaction of the leader-aircraft wake vortex with the follower-aircraft lifting surfaces.

The first part of the dissertation deals with the generation, evolution, and interaction of the wake vortices produced by an aircraft. In particular, it presents the results of the vortex …

Direct Adaptive Control For A Trajectory Tracking Uav, Nirmit Prabhakar

Doctoral Dissertations and Master's Theses

This research focuses on the theoretical development and analysis of a direct adaptive control algorithm to enable a fixed-wing UAV to track reference trajectories while in the presence of persistent external disturbances. A typical application of this work is autonomous flight through urban environments, where reference trajectories would be provided by a path planning algorithm and the vehicle would be subjected to significant wind gust disturbances. Full 6-DOF nonlinear and linear UAV simulation models are developed and used to study the performance of the direct adaptive control system for various scenarios. A stability proof is developed to prove convergence of …

A Numerical And Experimental Evaluation Of The Turbulent Heat Flux In A Heated Jet In Crossflow, Michael R. Borghi Jr.

Doctoral Dissertations and Master's Theses

The injection of fully-developed turbulent heated air from a tube into a cooler turbulent duct flow is examined, as an analogy to film cooled turbine blades. Scale Resolving Simulations (SRS) are used to examine the flow numerically. A Detached Eddy Simulation (DES) methodology is examined but found to be ineffective at correctly capturing the physics of the flow. A Large Eddy Simulation (LES) numerical model is developed and applied in which tube and duct turbulence inflow effects are emulated using a divergence-free synthetic eddy method (SEM). The LES sensitivity to the synthetic inflow turbulence is examined with a series of …

Topology Optimization Using Load Path And Homogenization, Kaveh Gharibi

Doctoral Dissertations and Master's Theses

In this work, the connection between topology optimization and load transfer has been established. New methods for determining load paths in two dimensional structures, plates and shells are introduced. In the two-dimensional space, there are two load paths with their total derivative equal to the transferred load, their partial derivatives related to stress tensor, and satisfying equilibrium. In the presence of a body load the stress tensor can be decomposed into solenoidal and irrotational fields using Gurtin or Helmholtz decomposition. The load path is calculated using the solenoidal field. A novel method for topology optimization using load paths and total …

Parametric Study Of Aerodynamic Performance Of An Airfoil With Active Circulation Control Using Leading Edge Embedded Cross-Flow Fan, M.A. Qayyum Mazumder

Doctoral Dissertations and Master's Theses

A concept of a cross-flow fan (CFF) embedded near the leading edge of an airfoil to actively control the boundary layer for lift and thrust enhancement has been proposed. The design places a cross-flow fan near the leading edge of an airfoil and flow is drawn in from the pressure side of the airfoil, energized and expelled out to the suction side near the leading edge. This CFF system simulates the active boundary layer control by blowing commercial computational fluid dynamics (CFD) code ANSYS Fluent is employed to perform 2-D calculations based on various parameters of the CFF and compared …

Development To A Flexible Surface Acoustic Wave Sensor For Strain Sensing, Neha Vedavathi Ramachandran

Doctoral Dissertations and Master's Theses

Surface acoustic wave (SAW) sensors have increasing demand in structural health monitoring due to their passive, variable bandwidth, reliable life-cycle, high accuracy, small size, and light nature. SAW sensors can not only provide the static states of the structural system, such as temperature and pressure but also enable continuous real-time monitoring of dynamic states including strains. SAW sensors are generally fabricated with a rigid piezoceramic substrate, incapable of adapting to highly curved surfaces or flexible objects. The ongoing demands of sensor adaptability with flexible substrates, which is also capable of wireless monitoring, is the basis of the research that can …

Biofidelic Piezoresistive Sandwich Composites, Nengda Jiang

Doctoral Dissertations and Master's Theses

Silicone based biofidelic surrogates are being used in many biomedical applications; e.g. to understand the body injury mechanisms, evaluate protective equipment like helmets and armors. Apart from matching the mechanical behavior of bodily tissues, there is an increasing requirement for these materials to be electrically conductive and piezoresistive to facilitate direct instrumentation. Carbon nanotubes (CNTs) are a possible filler to impart electrical conductivity and piezoresistivity to silicone biofidelic materials. A sandwich structure of silicone and CNT sheet, comprising two dielectric facesheets and a highly conductive core layer has added advantages of raising the dielectric permittivity and suppressing dielectric loss.

In …

A Computational Fluid Dynamics Study On The Aerodynamic Performance Of Ram-Air Parachutes, Angelo A. Fonseca Pazmiño

Doctoral Dissertations and Master's Theses

The modeling of a ram-air parachute presents challenges in the prediction of the inflight geometry, as there is a strong interaction between the flow field and parachute structure. This thesis presents the development of a CAD design and CFD methodology to the simulation of ram-air parachutes in steady-state conditions. Starting from a 2D rib drawing, methods were developed to approximate the 3D geometry and efficiently model the parachute as a rigid and impermeable body. The use of distortions was implemented on a 2D, pseudo-2D, and 3D model to enhance their behavior during a real flight. The SST turbulence model was …

A Computational Analysis Of The Aerodynamics And Aeroacoustics Of Jets With Fluid Injection, Marco Coderoni

Doctoral Dissertations and Master's Theses

A detailed numerical analysis of fluidic injection as a tool to reduce noise emission is presented here. The noise reduction strategy, developed at the Pennsylvania State University, is based on injectors that blow air into the diverging section of the nozzle to emulate the effect of interior corrugation on the jet plume. The advantage is that the injection can be activated during takeoff and turned o_ during other phases of flight so that performance is not affected. Numerical simulations are performed on a military-style nozzle based on the GE F400-series engines, with a design Mach number of 1:65, for over-expanded …

Parametrization Of Triple Screw Pumps For Aerospace Applications, Allison Putira

Doctoral Dissertations and Master's Theses

Triple Screw Pumps, a form of positive displacement pump, offer steady, high-pressure flow. In very small launch vehicles or upper stages turbopumps are not practical. This paper examines the performance of triple screw pumps to determine if they may serve as an alternative to turbopumps for use in small launch vehicles or upper stages. To this end, the geometry of the screws is first determined from the relative sizes of the screws and tooth height. From this — along with the screw angle and screw clearance — the performance parameters of flow rate, output pressure, and efficiency can be computed. …

A Novel Magnetorheological Fluid Damper For A Small Spacecraft With Flexible Appendages, Robert Waelchli

Doctoral Dissertations and Master's Theses

Small satellites have become increasingly popular over the past thirty years, particularly since the adoption of the common CubeSat architecture early this century. Because of their restricted volume and electrical budgets however, there are practical limits to the missions that small satellites may adopt. One potential near-term solution to the problem of limited electrical power may be the adoption of larger, flexible solar arrays. However, spacecraft with flexible appendages have historically presented attitude control challenges relating to platform stability given the dynamic response of the flexible components to applied torques. These challenges may be particularly disruptive to a small spacecraft …

Propulsive Battery Packs Sizing For Aviation Applications, Tianyuan Zhao

Doctoral Dissertations and Master's Theses

This thesis derives analytical methods for sizing the propulsive battery packs for designing an electric-driven aircraft. Lithium-Ion (Li-Ion) battery is the primary choice of battery cell chemistry in this thesis research due to its superior specific energy and market availability. The characteristics of Lithium-Ion battery cells are first determined and studied using experimental test results and manufacturers published data. Based on the design requirement to the battery system, the battery sizing will fall into one of the two sizing categories. The first category is power sizing, which requires the battery’s ability to deliver full power demanded by the electric motor. …

Development Of A Small Unmanned Aerial Vehicle Longitudinal Model For Future Flutter Testing, Said S. Hamada

Doctoral Dissertations and Master's Theses

This thesis presents the system identification of the longitudinal motion of a small unmanned aerial vehicle with flexible characteristics. The unmanned aerial vehicle of study is an off-the-shelf aircraft with limited knowledge about the dynamic model. The first task in obtaining a model for flutter testing is determining the rigid body model. Specifically, this thesis will focus in the development of the aircraft and obtaining the longitudinal rigid body model. This involves the assembly and configuration of the avionics and sensors, performing experiments to determine mass and inertia properties and using software tools for aerodynamic analysis to get preliminary values …

Vision-Aided Navigation Using Tracked Landmarks, Nicodemus Myhre

Doctoral Dissertations and Master's Theses

This thesis presents vision-based state estimation algorithms for autonomous vehicles to navigate within GPS-denied environments. To accomplish this objective, an approach is developed that utilizes a priori information about the environment. In particular, the algorithm leverages recognizable ‘landmarks’ in the environment, the positions of which are known in advance, to stabilize the state estimate. Measurements of the position of one or more landmarks in the image plane of a monocular camera are then filtered using an extended Kalman filter (EKF) with data from a traditional inertial measurement unit (IMU) consisting of accelerometers and rate gyros to produce the state estimate. …

Homography-Based State Estimation For Autonomous Exploration In Unknown Environments, Andres S. Chavez Armijos

Doctoral Dissertations and Master's Theses

This thesis presents the development of vision-based state estimation algorithms to enable a quadcopter UAV to navigate and explore a previously unknown GPS denied environment. These state estimation algorithms are based on tracked Speeded-Up Robust Features (SURF) points and the homography relationship that relates the camera motion to the locations of tracked planar feature points in the image plane. An extended Kalman filter implementation is developed to perform sensor fusion using measurements from an onboard inertial measurement unit (accelerometers and rate gyros) with vision-based measurements derived from the homography relationship. Therefore, the measurement update in the filter requires the processing …

Experimental Investigation Of Enhanced Damage Resistant Fiber Metal Laminates, Cannelle Metang Tefoung

Doctoral Dissertations and Master's Theses

Fiber metal laminates (FMLs) are hybrid composite structures made from fiber reinforced polymeric materials sandwiched between layers of thin metal alloy sheets. FMLs combine the advantages of metallic materials and fiber reinforced matrix systems. Some of these advantages include: lighter weight, enhanced impact tolerance, improved corrosion resistance, better fire resistance, longer fatigue life, greater tensile strength, easier repair ability and maintainability, etc. The most well-known commercially available FML is GLARE (Glass Laminate Aluminum Reinforced Epoxy), however there are ongoing issues, which include a very high fabrication cost compared to many competing material systems and substantial delamination upon impact and failure. …

An Underwater Vehicle Navigation System Using Acoustic And Inertial Sensors, Khalid M. Alzahrani

Doctoral Dissertations and Master's Theses

Unmanned Underwater Vehicles (UUVs) have become an essential tool for different underwater tasks. Compared with other unmanned systems, the navigation and localization for UUVs are particularly challenging due to the unavailability of Global Positioning System (GPS) signals underwater and the complexity of the unstable environment. Alternative methods such as acoustic positioning systems, Inertial Navigation Systems (INS), and the geophysical navigation approach are used for UUV navigation. Acoustic positioning systems utilize the characteristics of acoustic signals that have a lower absorption rate and a more extended propagation distance than electromagnetic signals underwater. The significant disadvantage of the INS is the “drift,” …

Numerical Simulation Of Shock Wave Propagation In Ducts With Grooves, Seyed Mehdi Mortazawy

Doctoral Dissertations and Master's Theses

The pressure attenuation of moving shocks when they propagate in ducts, is of great importance in a wide variety of applications, such as health, safety, and transportation. The objective of this research is to simulate the propagation of shock waves in ducts with roughness. The roughness is added in the form of grooves as in an existing experiment. Different shapes are considered in order to better understand the physics behind the evolution of the complex shock patterns resulting from diffraction, reflection and refraction of the primary moving shock. The contribution of grooves and duct shape on these phenomena and pressure …

Feasibility Study Of A Multi-Purpose Aircraft Concept With A Leading-Edge Cross-Flow Fan, Stanislav Karpuk

Doctoral Dissertations and Master's Theses

A wing-embedded Cross-Flow Fan (CFF) was first proposed as an active flow control (AFC) device nearly 40 years ago. The CFF can be employed as a propulsion device as well as a high-lift system. This thesis research focuses on investigating the use of CFF as a high-lift device for an Extremely Short Take-off and Landing (ESTOL) aircraft. The wing-embedded CFF performance analysis is mostly addressed from an aerodynamic perspective and focuses on using such AFC technology in the conceptual aircraft design process. In particular, the design trade study of an aircraft featuring CFF as a high-lift device applied to a …

Nonlinear Control Of Underactuated And Constrained Systems, Derek Hoffman

Doctoral Dissertations and Master's Theses

It is the purpose of this document to elaborate on the control of systems that are underactuated or otherwise constrained. To do so, local- and global-coordinate formulations are implemented to generate well-defined system dynamics for a multitude of scenarios. These dynamics are shown to lie on manifolds defined by mathematical restrictions, allowing for singularity-free modeling for global considerations. Feed-back controllers by extension share these benefits, facilitating singularity-free control algorithms as a result. Further, unactuated degrees of freedom can be treated as additional constraints, resulting in an embedded manifold upon the original dynamics. A transformation between a provided set of dynamical …

The Effect Of Task Load, Automation Reliability, And Environment Complexity On Uav Supervisory Control Performance, Sarah M. Sherwood

Doctoral Dissertations and Master's Theses

Over the last decade, military unmanned aerial vehicles (UAVs) have experienced exponential growth and now comprise over 40% of military aircraft. However, since most military UAVs require multiple operators (usually an air vehicle operator, payload operator, and mission commander), the proliferation of UAVs has created a manpower burden within the U.S. military. Fortunately, simultaneous advances in UAV automation have enabled a switch from direct control to supervisory control; future UAV operators will no longer directly control a single UAV subsystem but, rather, will control multiple advanced, highly autonomous UAVs. However, research is needed to better understand operator performance in a …