Engineering Commons^™

Performance Modeling Of Supercritical Carbon Dioxide Zigzag-Channel Printed Circuit Heat Exchangers, Katrine Birgitte Bennett

UNLV Theses, Dissertations, Professional Papers, and Capstones

Supercritical carbon dioxide (sCO2) is currently being studied as the working fluid in power producing Brayton cycles due to its excellent physical and thermodynamic properties, especially near the critical point. Printed circuit heat exchangers (PCHEs) are being considered for use as condensers and recuperators for this purpose due to their high strength and compact designs. Many experimental and numerical studies are being conducted to characterize and optimize sCO2 PCHE operation and develop correlations to describe their thermal-hydraulic performance. Additionally, a few experimental and numerical structural assessments of these PCHEs have been conducted, but all have been somewhat limited due to …

The Investigation Of Noise, Vibrations And Emissions Of Aero-Gas Turbine Combustion With Synthetic Kerosene Fuels, Margaret Kilpatrick

Honors College Theses

Climatic changes from aviation emissions are complex and include effects of greenhouse gases such as: CO2, NOx, and aerosols. For that reason, the objectives of this study were to investigate the noise, vibrations and emissions characteristics of synthetic kerosene combustion in an aerospace gas turbine to reduce the engine’s environmental impact. Sustainably produced synthetic kerosene is known for having low soot emissions due to little to no aromatics (compounds that create particle pollutants), and for being a sustainable alternative fuel source to imported oil. The noise and sound levels were collected using Bruel & Kjaer microphones to measure various mid …

Methodology Of Topology Optimization, Naziha Khandoker

Honors Theses

The need for lighter products is becoming increasingly essential as it cuts material cost and significant amount of weight, which is a key factor in the automotive and aerospace industries. Topology optimization allows us to achieve that by applying the concept to different structures with the goal of optimal distribution of material within finite volume design domain. Its algorithms selectively remove and relocate elements to achieve the optimum performance. This project performs a study on the effect of each design parameter over mechanical performance using Finite Element Analysis and applies it to set of wing attachment brackets. The optimized brackets …

Tumble Bot, Alena Beyer, Blake Gonzales, Jensen Severance, Liam Chaffey

Mechanical Engineering

Passive locomotion is the ability for an object to move from one place to another by the means of the environment. In nature species such as tumbleweed, fox tails, plankton, and man o’ war jellyfish rely on passive modes of transportation for survival and are able to cross vast distances with little to no expenditure of their own energy. This document seeks to explore the feasibility of building a machine relies on the energy of Mars’ environment to explore the Martian surface.

The “Tensegrity Tumbleweed Locomotion” (nicknamed Tumble Bot) senior project was sponsored by NASA Jet Propulsion Laboratory (JPL). The …

Wall-Jet Turbulence And Mixing Control By Way Of A Pulsed Inlet Velocity, Cristale D. Garnica Vallejo

Doctoral Dissertations and Master's Theses

Understanding wall-jet-induced turbulence and mixing is an important challenge in modern engineering, as drag reduction and mixing enhancement are attainable by modifying the flow development. Simulations are performed to investigate the effect on skin friction and flow mixing due to introducing controlled perturbations, at the initial shear layer of a planar wall-jet using jet inlet cyclic pulsing. The billow production by the Kelvin-Helmholtz instability, the instability that drives turbulence in a wall-jet, is modified by the excitation of the inlet velocity profile by a sine wave perturbation. Two types of wall-jet simulations are carried out, a two-dimensional compressible case at …

A Reinforcement Learning Approach To Spacecraft Trajectory Optimization, Daniel S. Kolosa

Dissertations

This dissertation explores a novel method of solving low-thrust spacecraft targeting problems using reinforcement learning. A reinforcement learning algorithm based on Deep Deterministic Policy Gradients was developed to solve low-thrust trajectory optimization problems. The algorithm consists of two neural networks, an actor network and a critic network. The actor approximates a thrust magnitude given the current spacecraft state expressed as a set of orbital elements. The critic network evaluates the action taken by the actor based on the state and action taken. Three different types of trajectory problems were solved, a generalized orbit change maneuver, a semimajor axis change maneuver, …

Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. Mcdermott

Electronic Theses and Dissertations

Composite materials have been adopted into primary aircraft structures by virtue of their great strength-to-weight and stiffness-to-weight ratios, fatigue insensitivity, and corrosion resistance. These characteristics are leveraged by aircraft designers to deliver improved fuel effciency and reduced scheduled maintenance burdens for their customers. These benefits have been impressively realized in the Boeing 787 and Airbus A350 XWB, with airframes utilizing about 50% composites by weight. Tempering these successes, however, are the inherent vulnerabilities of carbon-fiber reinforced composites. When compared to conventional metallic structure, composite laminates are more sensitive to stress concentrations at mechanical fastenings and damage due to low-velocity impact. …

Development Of A Research Spacecraft Test-Bed With Implementation Of Control Laws To Compensate Undesired Dynamics, Yomary Angélica Betancur Vesga

Doctoral Dissertations and Master's Theses

The development of research spacecraft systems has a significant impact on the preparation and simulation of future space missions. Hardware, software and operation procedures can be adequately tested, validated and verified before they are deployed for the actual mission. In this thesis, a spacecraft vehicle test-bed named Extreme Access System (EASY) was developed. EASY aims at supporting validation and verification of guidance, navigation and control algorithms. Description of EASY spacecraft systems, sub-systems and integration is presented in this thesis along with an analysis of results from numerical simulation and actual implementation of control laws. An attitude control architecture based on …

The Effectiveness Of Augmented Reality For Astronauts On Lunar Missions: An Analog Study, Godfrey Valencio D’Souza

Doctoral Dissertations and Master's Theses

The uses of augmented reality and head-up displays are becoming more prominent in industries such as aviation, automotive, and medicine. An augmented reality device such as the Microsoft HoloLens can project holograms onto the user’s natural field of view to assist with completion of a variety of tasks. Unfortunately, only a little research and development has begun in the space sector for astronauts using these head-up displays. Future lunar missions could incorporate augmented reality for astronauts to ease task load and improve accuracy. This study evaluated the usability, subjective workload, and task performance of 22 participants using the Microsoft HoloLens …

Numerical Treatment Of Schrödinger’S Equation For One-Particle And Two-Particle Systems Using Matrix Method, Spatika Dasharati Iyengar

Doctoral Dissertations and Master's Theses

With an increased interest in accurately predicting aerothermal environments for planetary entry, recent researches have concentrated on developing high fidelity computational models using quantum-mechanical first principles. These calculations are dependent on solving the Schrödinger equation using molecular orbital theory techniques. They are either approximate solutions to actual equations or exact solutions to approximate equations. Exact solutions have not found favor due to the computational expense of the problem. Hence, a novel numerical approach is developed and tested here using linear algebraic matrix methods to enable precise solutions.

The finite-difference technique is used to cast the Time-Independent Schrödinger equation (TISE) in …

In-Situ Measurement Of Resin Shrinkage For Aerospace Components, Samarth Motagi

Doctoral Dissertations and Master's Theses

Resin shrinkage due to chemical changes and thermal gradients plays an important role in the residual stress evolution during composite manufacturing. In this thesis, we develop a new in-situ experimental approach for measuring resin shrinkage during curing with the help of digital image correlation (DIC) instrumented on a specially designed autoclave with borosilicate viewports. The images of the resin sample are captured at regular intervals with the help of DIC to measure the displacement and strains during the curing process. We utilize this method for a comparative analysis of resin shrinkage in two common aerospace epoxies, Epoxy 105 and EPON …

Adaptive Learning Terrain Estimation For Unmanned Aerial Vehicle Applications, Pedro L. Vergara Garcia

Doctoral Dissertations and Master's Theses

For the past decade, terrain mapping research has focused on ground robots using occupancy grids and tree-like data structures, like Octomap and Quadtrees. Since flight vehicles have different constraints, ground-based terrain mapping research may not be directly applicable to the aerospace industry. To address this issue, Adaptive Learning Terrain Estimation algorithms have been developed with an aim towards aerospace applications. This thesis develops and tests Adaptive Learning Terrain Estimation algorithms using a custom test benchmark on representative aerospace cases: autonomous UAV landing and UAV flight through 3D urban environments. The fundamental objective of this thesis is to investigate the use …

Numerical Investigation Of Scaling Effects Of A Ramjet-Powered Projectile, Arjun Jaishankar Vedam

Doctoral Dissertations and Master's Theses

Ramjet flowpath miniaturization is a potentially useful technology for integration into munitions to increase range, accuracy, and lethality. The emphasis of this effort is to numerically characterize the performance of a miniature hydrogen-fueled and ethylene-fueled ramjet flowpath during Mach 3 and Mach 3.5 sea-level flight. The effect of geometric scale on ramjet performance is evaluated using high-fidelity RANS CFD models. Sensitivity to nonequilibrium laminar and turbulence-limited chemistry, and transitional turbulence treatments are evaluated. The physical sources of small scale performance limitations are identified for both fuel types. Finally, flowpath integration for small-scale applications is briefly addressed.

Fuel Efficient Control Design And Constrained Motion Analysis For Spacecraft Coulomb Formation In Elliptic Chief Orbits, Muhammad Wasif Memon

Doctoral Dissertations and Master's Theses

The use of Coulomb force has been analyzed in recent years to provide propulsion in space for various applications. Coulomb formation can also be utilized to make close formation spacecraft missions fuel efficient. In this study, the Coulomb formation of two craft is studied in elliptic chief orbits for two formation geometries. The first formation requires both spacecraft to be aligned along the nadir (radial) direction and the second formation requires both spacecraft to maintain a constant separation distance relative to each other while each spacecraft rotates freely on the surface of a sphere with the ratio of the radii …

Autonomous Autorotation Of A Tilt-Rotor Aircraft Using Model Predictive Control, Elias Wilson

Doctoral Dissertations and Master's Theses

Tilt rotor vehicles are governed by FAA laws also used for conventional helicopters, which require autorotational maneuvering and landing given a total power failure. With low inertia rotors and high disk loading of tilt rotor vehicles, this already difficult task becomes significantly more challenging. In this work, a model predictive controller is developed to autonomously maneuver and land a tilt rotor given complete power loss. A high fidelity model of a tilt rotor vehicle is created and used to simulate the vehicle dynamics and response to control inputs. A reduced order dynamic model is used within a model predictive control …

Remote Sensing, Modeling, And Spectroscopic Studies Of Gigantic Jets And Lightning Leaders, Levi Boggs

Theses and Dissertations

This dissertation focuses on four interrelated investigations with the ultimate goal of better understanding electrical phenomena in the lower and upper atmosphere. The four investigations utilized observations and data analysis for electrical discharges occurring in the troposphere, such as cloud-to-ground and intracloud discharges, and discharges occurring in the stratosphere/lower ionosphere, known as gigantic jets. The observations are from ground-based high-speed cameras and lightning locating systems, space-borne lightning imagers, and remote and in-situ meteorological instrumentation. Numerical modeling was also performed to study the lightning associated with gigantic jets by using a stochastic lighting propagation model. Finally, this dissertation focuses on the …

Investigating The Effects Of Altitude And Flap Setting On The Specific Excess Power Of A Pa-28-161 Piper Warrior, Tjimon Meric Louisy

Theses and Dissertations

The high number of General Aviation (GA) accidents attributed to Loss of Control suggests that GA pilots are lacking low speed awareness and are unable to appropriately recognize when the aircraft is in a low energy state. There is, therefore, an urgent need for the development of an energy management system which is applicable to GA aircraft that can alert the pilot in situations of low energy conditions and recommends to the pilot the appropriate corrective action to restore conditions to a safe energy state. This will require the development of an algorithm that governs this energy management system that …

Earth – Mars Cycler Vehicle Conceptual Design, Bhumika Patel

Theses and Dissertations

This thesis summarizes a conceptual design for an Earth – Mars Cycler vehicle designed to transfer astronauts between Earth and Mars. The primary objective of the design study is to accommodate the crews’ needs and to estimate the overall mass and power required during Earth – Mars transfer. The study defines a concept of operations and system functional requirements and discusses the systems breakdown and subsystems design analysis. Systems developed for the cycler vehicle is designed primarily for the S1L1 cycler trajectory. The initial sizing of cycler subsystems is based on reference data from historical human spaceflight. The study performed …

Dynamics Considerations Dedicated To Study Bodies In High-Altitude Free Fall, Michelle Carolina Rodriguez

Theses and Dissertations

The objective of this thesis is to develop a simulation model to study the dynamics of a rigid body in free fall. A set of 6 degrees of freedom (DOF) equations is developed to reflect the dynamic and trajectory characteristics over time. The simulation models a body dropped at different altitudes ranging from 30,480 – 39,624 m (100,000 – 130,000 ft). The trajectory of the body is analyzed using a mathematical nonlinear dynamics model. The mathematical model was developed in MATLAB and Simulink which can be modified for different geometries and conditions. The model was validated by testing that the …

Navigational Feasibility Of Flyby / Impact Missions To Interstellar Objects, Declan Moore Mages

Master's Theses

In October 2017, the first interstellar object, designated 1I/2017 U1 and more commonly referred to as Oumuamua, was detected passing through our solar system by the Pan-STARRS telescope, followed recently by the detection of 2I/Borisov in August 2019. These detections came much sooner than thought possible, and have redefined our understanding of the population of interstellar objects. With the construction of the next generation of powerful observatories, future detections are estimated to occur as frequently as two per year, and while there is significant scientific understanding to be gained from observing these objects remotely, a spacecraft sent to intercept one …

Revolution In Autonomous Orbital Navigation (Raon), Rachit Bhatia

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Spacecraft navigation is a critical component of any space mission. Space navigation uses on-board sensors and other techniques to determine the spacecraft’s current position and velocity, with permissible accuracy. It also provides requisite information to navigate to a desired position, while following the desired trajectory. Developments in technology have resulted in new techniques of space navigation. However, inertial navigation systems have consistently been the bedrock for space navigation.

Recently, the successful space mission GOCE used on-board gravity gradiometer for mapping Earth’s gravitational field. This has motivated the development of new techniques like cold atom accelerometers, to create ultra-sensitive gravity gradiometers, …

Performance Enhancement And Characterization Of An Electromagnetic Railgun, Paul M. Gilles

Master's Theses

Collision with orbital debris poses a serious threat to spacecraft and astronauts. Hypervelocity impacts resulting from collisions mean that objects with a mass less than 1g can cause mission-ending damage to spacecraft. A means of shielding spacecraft against collisions is necessary. A means of testing candidate shielding methods for their efficacy in mitigating hypervelocity impacts is therefore also necessary. Cal Poly’s Electromagnetic Railgun was designed with the goal of creating a laboratory system capable of simulating hypervelocity (≥ 3 km/s) impacts. Due to several factors, the system was not previously capable of high-velocity (≥ 1 km/s) tests. A deficient projectile …

Dynamic Pressure Sensing For The Flight Test Data System, Marc Y. Goupil

Master's Theses

This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation …

Development Of An Analysis Tool And Weight Estimation Method For Aircraft Wing Structures, Kevin M. Barton

Master's Theses

The goal of this effort was to build an analysis tool for aircraft wings and incorporate it into a program that optimizes the wing structure for the lowest weight for the conceptual design phase. The analysis tool calculates the internal stresses in primary load carrying members using established analysis methods for semimonocoque beams. Via a Graphical User Interface (GUI) built in MATLAB, the user can define the structural layout and material properties of the load carrying members. The program requires a degenerate geometry model built with Vehicle Sketch Pad (OpenVSP) to define the outer mold line (OML) of the wing, …

Development And Testing Of A Hydrogen Peroxide Injected Thrust Augmenting Nozzle For A Hybrid Rocket, Mark C. Heiner

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

During a rocket launch, the point at which the most thrust is needed is at lift-off where the rocket is the heaviest since it is full of propellant. Unfortunately, this is also the point at which rocket engines perform the most poorly due to the relatively high atmospheric pressure at sea level. The Thrust Augmenting Nozzle (TAN) investigated in this paper provides a solution to this dilemma. By injecting extra propellant into the nozzle but downstream of the throat, the internal nozzle pressure is raised and the thrust is increased, and the nozzle efficiency, or specific impulse is potentially improved …

Axial Compressor Based On Plastic Additive Manufacturing, Chris Phu

Mechanical Engineering Undergraduate Honors Theses

Turbomolecular pumps designed to function in very low pressures tend to be too prohibitively expensive for student researchers. On the other hand, while conventional pumps are affordable, they can’t function in extreme low pressures. An additively manufactured axial compressor however is inexpensive to manufacturer and only needs to be build up enough pressure for a conventional pump to function. After many design iterations, a final iteration that is near vacuum chamber ready has been 3D printed and tested for spin functionally. The designed axial compressor is easy to assemble and very modular. Conclusions from each of the design iterations is …

Fuel Shortages During Hurricanes: Epidemiological Modeling And Optimal Control, Sabique Ul Islam

Doctoral Dissertations and Master's Theses

Hurricanes are powerful agents of destruction with significant socioeconomic impacts. A persistent problem due to the large-scale evacuations during hurricanes in the southeastern United States is the fuel shortages during the evacuation. Fuel shortages often lead to stranded vehicles and exacerbate the evacuation efforts. Computational models can aid in emergency preparedness and help mitigate the impacts of hurricanes. In this thesis, the hurricane fuel shortages are modeled using the Susceptible-Infected-Recovered (SIR) epidemic model. Crowd-sourced data corresponding to Hurricane Irma and Florence are utilized to parametrize the model. An estimation technique based on Unscented Kalman filter (UKF) is employed to evaluate …

Estimation Of The Fatigue Life Of Additively Manufactured Metallic Components Using Modified Strain Life Parameters Based On Surface Roughness, Peter Grohs

Masters Theses

In this study, a method is developed to estimate the effects of surface roughness on the fatigue life of additively manufactured titanium Ti6Al4V, aluminum 7075–T6, and steel 4340 alloys through modified strain life parameters using finite element analysis (FEA). This method is highly beneficial to the fatigue analysis of as-built additively manufactured metal components, which possess rough surfaces that reduce fatigue life significantly but are challenging to analyze directly using finite element simulation because of complex geometries, i.e., modeling an exact surface profile is arduous.

An effective stress concentration factor, incorporating roughness data, is defined to quantify their effects on …

Diseño De Un Sistema De Captación Y Recuperación De Aguas De Fertirriego, Natalia Pulgarin Arandia, Stefany Alejandra Rodríguez Chirivi

Ingeniería en Automatización

En el presente trabajo de grado se diseñó una alternativa de solución para un factor que impacta significativamente, el ciclo de productividad de los cultivos y el recurso hídrico como es el de los lixiviados. Estos son los residuos líquidos producidos después del proceso de fertirriego en plantas. Por ello se realiza el diseño de un sistema de captación y recuperación de manera cíclica de lixiviados en un sistema de fertirriego con el objeto de hacer uso adecuado y una filtración parcial de los mismos, es decir, que el agua una vez usada en el cultivo pasa por un proceso …

An Investigation Of High-Speed Consolidation And Repair Of Carbon Fiber - Epoxy Composites Through Ultrasonic Welding, David A. Hoskins

LSU Master's Theses

Adhesive repair of carbon fiber composite structures is commonly done on damaged structures to extend the service life. This method requires careful preparation of the damaged surface with intricate steps to ensure good bonding between the repair patch and the parent structure by means of an adhesive film. As with many forms of composite manufacturing, it is required to perform vacuum bagging, debulking, and a heated cure depending on the resin. All these steps make the repair process costly and time consuming.

In this present work, an alternative method of repair is investigated which explores the experimental feasibility of using …