Engineering Commons^™

State-Of-The-Art Of Thermal Control Solutions To Establish A Modular, Multi-Orbit Capable Spacecraft Thermal Management System Design Methodology, Robert C. Consolo Jr

Doctoral Dissertations and Master's Theses

Today, the exploration and exploitation of space continues to become a more common occurrence. All types of spacecraft (S/C) utilize various types of thermal management solutions to mitigate the effects of thermal loading from the unforgiving vacuum of space. Without an appropriately designed thermal system, components on-board the S/C can experience failure or malfunction due to fluctuations in temperatures either beyond the designed operational parameters or unstable oscillating temperatures. The purpose of this study is to perform a comprehensive review of technologies available today that are being used for thermal management onboard S/C in addition to investigating the means to …

Numerical Simulation Of A Cryogenic Spray, Neel Kishorkumar Shah

Doctoral Dissertations and Master's Theses

Cryogenic sprays have many applications in modern engineering. Cooling of electronic equipment subject to high heat flows, surgical ablation of gastrointestinal mucosae or orbital maneuvering are a few examples of their versatility. However, the atomization of a cryogenic liquid is a complex process. During such an event, aerodynamic effects associated with secondary atomization are further affected by thermodynamic flashing. A better understanding of the characteristics of cryogenic sprays is then necessary to allow for improved design and optimization in applications. The overarching objective of this study is to document such characteristics. The numerical simulation was performed over cryogenic nitrogen spray …

In-Situ Monitoring Of Additive Manufacturing Using Digital Image Correlation, Martina Jani

Doctoral Dissertations and Master's Theses

Advances in additive manufacturing over the past decade have led to applications in multiple fields. In particular, additive manufacturing answers the need for high flexibility in designing complex structures, however, the rapid thermal fluctuations during processing lead to numerous defects and processing-induced residual stresses. In this research, an in-situ approach using Digital Image Correlation (DIC) is developed to monitor the deformation during the processing, and thereby analyze the formation of defects and residual stresses. DIC is a visual technique that compares the changes in speckle pattern in consecutive images of a specimen to determine the displacements and strains. This research …

Kinematics Of Inter-Ply Interfaces In Composite Manufacturing, Sandeep Chava

Doctoral Dissertations and Master's Theses

The ubiquitous usage of polymer matrix composites in many applications demands a comprehensive understanding of composite interfaces and processing induced residual stresses, which critically affect both the manufacturing processes and the deformation mechanisms. Processing induced residual stresses are often responsible for causing warping, delamination, and dimensional instability in composite structures. This research includes new in-situ experimental approaches, cure cycle design, interface modification, and thermomechanical modeling for developing a fundamental understanding of the cure kinetics during composite manufacturing. Strains, ply-movement, and formation of defects are observed in-situ using digital image correlation (DIC) during the autoclave cure cycle for the first time. …

Fabrication & Mechanical Properties Of Hastelloy-X Matrix Ceramic Composite, Sultan Stewart

Doctoral Dissertations and Master's Theses

In the aerospace industry, there is a desire for increased thermal and mechanical properties of sealing materials. In this thesis, porous Hastelloy-X alloy scaffolds with 80% porosity, currently used for fabricating seals in turbine applications, were used as the base material. The microstructure of the porous Hastelloy-X scaffolds was infiltrated using a room temperature curing silicate colloid (trade name -Dichtol HTWG Hydro #2506) and a novel zirconia based colloid to fabricate the metal matrix composites. Various fabrication processes, some using vacuum and pressure to assist the flow were utilized to infiltrate the scaffolds. The green composites were then cured at …

Optimal Sizing And Control Of Hybrid Rocket Vehicles, Srija Ryakam

Doctoral Dissertations and Master's Theses

In the present work, a genetic algorithm is used to optimize a hybrid rocket engine in order to minimize the propellant required for a specific mission. In a hybrid rocket engine, the mass flow rate of the oxidizer can be throttled to enhance the performance of the rocket. First, an analysis of the internal ballistics and the ascent trajectory has been carried out for different mass flow rates of the oxidizer as a function of time, for a fixed amount of oxidizer, in order to study the effect of throttling. Two equivalent problems are considered: in the first problem the …

Trajectory Generation For A Multibody Robotic System: Modern Methods Based On Product Of Exponentials, Aryslan Malik

Doctoral Dissertations and Master's Theses

This work presents several trajectory generation algorithms for multibody robotic systems based on the Product of Exponentials (PoE) formulation, also known as screw theory. A PoE formulation is first developed to model the kinematics and dynamics of a multibody robotic manipulator (Sawyer Robot) with 7 revolute joints and an end-effector.

In the first method, an Inverse Kinematics (IK) algorithm based on the Newton-Raphson iterative method is applied to generate constrained joint-space trajectories corresponding to straight-line and curvilinear motions of the end effector in Cartesian space with finite jerk. The second approach describes Constant Screw Axis (CSA) trajectories which are generated …

Airspace Integration Of New Entrants And Safety Risk Management Models, Fadjimata Issoufou Anaroua

Doctoral Dissertations and Master's Theses

In recent years, the demand for airspace access of Unmanned Aerial Systems (UAS) increased significantly and is continuously increasing for different altitude-types UAS. A similar evolution is expected from Commercial Space Operations (CSO) in the next years. These aviation/aerospace systems will need to be seamlessly integrated into the National Airspace System (NAS), at their operational altitude levels, and accounted for from all perspectives, including proactively addressing their safety hazards. This thesis captures the requirements for the new entrants’ integration, and then identifies and analyzes the safety risks added to the NAS operations by its new entrants, the future omnipresent UAS …

The Effect Of Part Curvature On The Formation Of Residual Stresses In Carbon Fiber Prepreg Laminates, Bradley Rogan

Doctoral Dissertations and Master's Theses

The formation of residual stresses during the processing of composite parts can lead to undesired defects such as delamination which can reduce the overall strength of a completed component. Furthermore, the addition of curvature to the part geometry tends to result in wrinkle formation which leads to stress concentrations developing throughout the curing process in the areas near these wrinkles. In this work, Digital Image Correlation (DIC) will be used to monitor the development of stresses throughout the cure cycle of carbon fiber prepreg in several different lay-ups and across tool plates with varying curvatures to determine what effect the …

High Fidelity Studies In Closed-Loop Control Of Unsteady Aerodynamics, Miriam Theobald-Deschine

Doctoral Dissertations and Master's Theses

We implement and explore the success of a nonlinear, closed loop flow control strategy based on POD-ROM focusing on boundary-layer transitional flow in high-fidelity computational studies involving FDL3DI ILES code. Controlling the boundary-layer transition from laminar to turbulent allows the laminar boundary-layer to be lengthened, decreasing skin-friction drag on an airfoil. Analyses are conducted on a flat plate with an elliptical leading edge, later to be implemented in future studies with real airfoil geometry. The feedback control design employs strategically placed synthetic-jet micro actuators and pressure sensors. The efficiency of the closed-loop flow control strategies is examined in comparison with …

Satellite Deceleration Using Gravity Assist From Asteroid, Nicolas M. Prulhiere

Doctoral Dissertations and Master's Theses

Satellites have used gravity assists to increase their speed when exploring the solar system. This same maneuver can be done but with the objective to slow down the satellites. This has been theorized to slow down asteroids using the moon to capture them in earth’s orbit. My goal is to determine if asteroids can be used to provide a change in speed great enough to the point that after multiple of these maneuvers the satellite can come to a stop. By being able to slow down and stop a satellite without having to use thrusters will allow the mass allocated …

Design, Analysis And Experimental Evaluation Of 3d Printed Variable Stiffness Structures, Rossana R. Fernandes

Doctoral Dissertations and Master's Theses

The rapid progress of additive manufacturing (AM) introduces new opportunities but also new challenges for design and optimization to ensure manufacturability, testability and accurate representation/prediction of the models. The present dissertation builds a bridge between design, optimization, AM, testing and simulation of advanced optimized variable-stiffness structures. The first part offers an insight on the mechanical, viscoelastic and failure characteristics of AM continuous fiber composites. This understanding was used in the second part to investigate the feasibility of different topology and fiber-orientation optimization methods and the manufacturability of the resulting models. The study also assesses the effects of the manufacturing constraints …

Investigation On The Interaction Of An Impinging Jet With Cylinder Wakes, Karthik Krishna

Doctoral Dissertations and Master's Theses

Jet impingement cooling is a widely used cooling method due to the high heat transfer rates associated with it. Research for improving heat transfer rates for this cooling is still being carried out due to its broad application in various fields like gas turbine blade cooling, electronic component cooling, and paper drying. The unsteady jet oscillation effectively enhances the stagnation region and the time-averaged heat transfer rates. It is shown that a novel passive jet oscillation technique can be achieved using the vortices periodically shed from a cylinder placed upstream in a channel with an initial crossflow. Preliminary CFD results …

Durability And Damage Analysis Of Hybrid Multiscale Composites, Suma Ayyagari

Doctoral Dissertations and Master's Theses

In this dissertation, an effort was carried out to enhance the mechanical performance of fiber reinforced composites (FRPs) by modification of the fibers’ surface morphologies. The effects of various surface alterations of a plain-woven carbon fiber fabric surface, on the fiber/epoxy interface were investigated. The alterations were mostly achieved by growing different nanofillers like zinc oxide nanorods (ZnO NR), carbon nanotubes (CNTs), and metal organic frameworks (MOFs) on the fiber surface. While the growth techniques for ZnO NR and CNTs place restrictions on the size of the fabricated composites, MOFs route is uniform, affordable, and can be readily scaled up …

Shape Optimization Of A Sandwich Composite Plate With Low-Velocity Impact Loading And Effect Of Finite Difference Sensitivity Analysis, Utsav Shah

Doctoral Dissertations and Master's Theses

The structural design of spacesuits is essential in an advancing future of both Lunar and Martian space exploration. A typical spacesuit is made of sandwich composite material and designed to withstand various pressure and loading conditions while also considering the safety and comfort of the astronauts. One of the critical load cases in spacesuit design is a low-velocity impact (LVI) which may occur due to tool drop and other similar scenarios. The objectives of this work were (a) to create a finite element (FE) model of a component of a spacesuit, (b) validation of the FE model through experiments, (c) …

Active Control Of Coherent Structures In An Axisymmetric Jet, Michael Marques Goncalves

Doctoral Dissertations and Master's Theses

The primary objective of this work is to develop high-fidelity simulation model for jet noise control predictions and quantify the sound reduction when an external source frequency mode excitation is imposed on the jet flow. Whereas passive approaches using mixing devices, such as chevrons, have been shown to reduce low-frequency noise in jet engines, such approaches incur a performance penalty since they result in a reduced thrust. To avoid a performance penalty in reducing jet noise, the current work investigates a open-loop active noise control (ANC) system that utilizes a unsteady microjet actuator on the nozzle lip in the downstream …

Background Flow Influence On Impulsive Jet-Driven Micro Droplet Dispersal, Vaishak Thiruvenkitam

Doctoral Dissertations and Master's Theses

Accurately predicting the airborne spread of infectious diseases is crucial in controlling the COVID­19 pandemic today. Studies have shown the spread of expiratory droplets depends on ambient thermodynamic conditions and flow properties of the jet emitted by the activity. However, the droplet spread in conditions of background flow is not yet comprehensively understood. This study uses the Eulerian­-Lagrangian model with k−ω turbulence modelling to simulate spread of particles and study the factors affecting it in a closed environment with a background flow. Respiratory activities are modeled as a non-­isothermal jet of air with droplets suspended in them in a predetermined …

Envelope Analysis Of Speed-Controlled Evtol Urban Air Mobility Vehicles, David Thompson

Doctoral Dissertations and Master's Theses

There are many vehicles being developed which rely on electrically driven propellers/rotors for both control and propulsion. Based on these vehicles, it is hypothesized that there exists a size limit for speed-controlled propellers/rotors in terms of propeller/rotor diameter. To investigate this, a scaling method was created to allow for a vehicle to be created without being based on a specific mission or passenger/cargo requirement. Relationships were developed to size both the physical vehicle and the weight of the vehicle based on the propeller/rotor diameter. A simulation of a quadcopter was created for the vehicle and scaled with both propeller/rotor diameter …

A Reduced-Order Model Bi-Modal Excitation Of A Supersonic Planar Jet, Benjamin Malczewski

Doctoral Dissertations and Master's Theses

This work analytically and numerically examines the effects of bi-modal excitation on a Mach 1.5 heated planar jet. Starting with the Navier-Stokes equations, triple decomposition is applied to the flow components. A reduced order model is derived, turning the Navier-Stokes partial differential equations into a set of coupled ordinary differential equations, relating the momentum thickness and amplitudes of a fundamental and subharmonic mode to the streamwise location along the jet. Computational fluid dynamics data from the minor plane of a Mach 1.5 heated rectangular jet is used to verify a hyperbolic tangent profile for the mean flow at various streamwise …

On The Local Heat Transfer Behavior Or Supercritical Carbon Dioxide, Neil Sullivan

Doctoral Dissertations and Master's Theses

A detailed study of the local heat transfer behavior of supercritical carbon dioxide (sCO2) is performed. Flows relevant to heat transfer devices, such as sCO2 heaters, recuperators, and internally cooled turbine blades are studied, with particular attention paid to data reduction methodology, and the use of appropriate reference quantities, nondimensionalizations, and correlations. Additionally, a semi-intrusive temperature measurement technique capable of obtaining highly spatially resolved temperature distributions is adapted for use in the challenging conditions of supercritical (SC) flow. SC fluids have proven difficult to study both experimentally and numerically due to dramatically changing thermodynamic and transport properties near the critical …

Additively Manufactured Dielectric Elastomer Actuators: Development And Performance Enhancement, Stanislav Sikulskyi

Doctoral Dissertations and Master's Theses

The recently emerging and actively growing areas of soft robotics and morphing structures promise endless opportunities in a wide range of engineering fields, including biomedical, industrial, and aerospace. Soft actuators and sensors are essential components of any soft robot or morphing structure. Among the utilized materials, dielectric elastomers (DEs) are intrinsically compliant, high energy density polymers with fast and reversible electromechanical response. Additionally, the electrically driven work principle allows DEs to be distributed in a desired fashion and function locally with minimum interference. Thus, a great effort is being made towards utilizing additive manufacturing (AM) technologies to fully realize the …

Design And Flight-Path Simulation Of A Dynamic-Soaring Uav, Gladston Joseph

Doctoral Dissertations and Master's Theses

We address the development of a dynamic-soaring capable unmanned aerial vehicle (UAV) optimized for long-duration flight with no on-board power consumption. The UAV’s aerodynamic properties are captured with the integration of variable fidelity aerodynamic analyses. In addition to this, a 6 degree-of-freedom flight simulation environment is designed to include the effects of atmospheric wind conditions. A simple flight control system aids in the development of the dynamic soaring maneuver. A modular design paradigm is adopted for the aircraft dynamics model, which makes it conducive to use the same environment to simulate other aircraft models. Multiple wind-shear models are synthesized to …

Fault Tolerant Deep Reinforcement Learning For Aerospace Applications, Christoph Elias Aoun

Doctoral Dissertations and Master's Theses

With the growing use of Unmanned Aerial Systems, a new need has risen for intelligent algorithms that not only stabilize or control the system, but rather would also include various factors such as optimality, robustness, adaptability, tracking, decision making, and many more. In this thesis, a deep-learning-based control system is designed with fault-tolerant and disturbance rejection capabilities and applied to a high-order nonlinear dynamic system. The approach uses a Reinforcement Learning architecture that combines concepts from optimal control, robust control, and game theory to create an optimally adaptive control for disturbance rejection. Additionally, a cascaded Observer-based Kalman Filter is formulated …

Modeling Of A Hybrid-Electric System And Design Of Control Laws For Hybrid-Electric Urban Air Mobility Power Plants, Sohail Bin Salam Lahaji

Doctoral Dissertations and Master's Theses

Advanced Air Mobility (AAM) is an emerging market and technology in the aerospace industry. These systems are being developed to overcome traffic congestion. The current designs make use of Distributed Electric Propulsion (DEP): either fully electric or hybrid electric. The hybrid engine system consists of two power sources: prime movers, such as turbine engines, and batteries. The hybrid systems offer higher range and endurance compared with the existing fully electric systems. Hybrid-electric power generation systems for AAM have different mission requirements when compared to systems used in automobiles. Therefore, there is a particular need to model hybrid-electric systems and the …

Adaptive-Optimal Control Of Spacecraft Near Asteroids, Madhur Tiwari

Doctoral Dissertations and Master's Theses

Spacecraft dynamics and control in the vicinity of an asteroid is a challenging and exciting problem. Currently, trajectory tracking near asteroid requires extensive knowledge about the asteroid and constant human intervention to successfully plan and execute proximity operation. This work aims to reduce human dependency of these missions from a guidance and controls perspective. In this work, adaptive control and model predictive control are implemented to generating and tracking obstacle avoidance trajectories in asteroid’s vicinity.

Specifically, direct adaptive control derived from simple adaptive control is designed with e modification to track user-generated trajectories in the presence of unknown system and …

Effect Of Galvanic Corrosion On Crack Propagation Of Cold Expanded Holes In Aa2024-T3, Ken Shishino

Doctoral Dissertations and Master's Theses

A search for the balance between weight reduction and durability of a structure has always been a popular topic within the aerospace industry. Among numerous researches to improve a structure’s fatigue life, processes on mechanically fastened joints have been a topic of focus as it is naturally a discontinuity in the material leading to a local stress concentration under loading. Cold expansion is a well-known technique with a wide range of applications in both new and repaired structures. The benefits include the extension of fatigue life and a delay in crack growth without addition of weight. However, localized galvanic corrosion …

Adaptive Control For Nonlinear, Time Varying Systems, John Zelina

Doctoral Dissertations and Master's Theses

It is common for aerospace systems to exhibit nonlinear, time varying dynamics. This thesis investigates the development of adaptive control laws to stabilize and control a class of nonlinear, time varying systems. Direct adaptive control architectures are implemented in order to compensate for time varying dynamics that could, for example, be caused by varying inertia resulting from fuel slosh or settling in a tank. The direct adaptive controller can also respond to external disturbances and unmodeled or nonlinear dynamics. Simulation results are presented for a prototype system that consists of two rotating tanks with time varying inertia due to the …

Investigation Of Bio-Inspired Pin Geometries For Heat Transfer Applications, Anish Prasad

Doctoral Dissertations and Master's Theses

Array of circular cylindrical pins or tubes are one of the most widely used type of convection cooling systems, profoundly used in the internal cooling of gas turbine blades. They promote heat transfer due to flow acceleration, secondary flows and wake shedding, at the expense of large pressure loss and unsteadiness in the flow. The need to reduce pressure loss and maintain the heat transfer rates are a much needed requirement for a variety of industries to improve the cooling efficiency. One such prominent line of research is conducted on optimizing the design of the circular cylindrical pins to increase …

Data-Driven Architecture To Increase Resilience In Multi-Agent Coordinated Missions, D. F.

Doctoral Dissertations and Master's Theses

The rise in the use of Multi-Agent Systems (MASs) in unpredictable and changing environments has created the need for intelligent algorithms to increase their autonomy, safety and performance in the event of disturbances and threats. MASs are attractive for their flexibility, which also makes them prone to threats that may result from hardware failures (actuators, sensors, onboard computer, power source) and operational abnormal conditions (weather, GPS denied location, cyber-attacks). This dissertation presents research on a bio-inspired approach for resilience augmentation in MASs in the presence of disturbances and threats such as communication link and stealthy zero-dynamics attacks. An adaptive bio-inspired …

Computational Investigation Of Perforated Plate Film Cooling Utilizing Conjugate Heat Transfer, Jonathan Sippel

Doctoral Dissertations and Master's Theses

The accuracy of modern state-of-practice computational fluid dynamics approaches in predicting the cooling effectiveness of a perforated plate film-cooling arrangement is evaluated in ANSYS Fluent. A numerical investigation is performed using the Reynolds Averaged Navier Stokes equations and compared to NASA Glenn’s available Turbulent Heat Flux 4 experimental measurements collected as a part of the Transformational Tools and Technologies Project. A multiphysics approach to model heat conduction through the solid geometry is shown to offer significant improvements in wall temperature and film effectiveness prediction accuracy over the standard adiabatic wall approach. Additionally, localized gradient-based grid adaption is analyzed using the …