Engineering Commons^™

Optimal Re-Entry Trajectory Terminal State Due To Variations In Waypoint Locations., William J. Karasz

Theses and Dissertations

The Air Force's Prompt Global Reach concept describes the desire to have a capability to reach any target within a 9000 nautical mile radius within two hours of launch. To meet this objective, much effort is being devoted to hypersonics and re-entry vehicles. Given the limited maneuverability of hypersonic vehicles, computational modeling is used to generate trajectories before launch to strike intended targets. In addition to endpoint (target) constraints, additional waypoints may constrain the trajectory. This research finds the optimal trajectory which satisfies the endpoint and waypoint constraints, and then investigates where else the vehicle can go while still meeting …

Dynamic Supersonic Base Store Ejection Simulation Using Beggar, Michael D. Johnson

Theses and Dissertations

Static and dynamic conditions throughout various aft supersonic store separation events are examined using the Beggar Computational Fluid Dynamics (CFD) code from Air Force SEEK Eagle Office at Eglin Air Force Base, FL. An 8.9 deg half angle sphere cone is used for the carrier vehicle with an identically shaped store stowed within a hollow compartment in the aft section of the carrier body. Dynamic store separation simulations are implemented at a free-stream Mach of 2.9 with a Reynolds number of Re = 6.9 x 10⁶/m referenced against carrier base diameter. Analysis covers multiple dynamic separation events along …

Flexible Twist For Pitch Control In A High Altitude Long Endurance Aircraft With Nonlinear Response, Vanessa L. Bond

Theses and Dissertations

Information dominance is the key motivator for employing high-altitude long-endurance (HALE) aircraft to provide continuous coverage in the theaters of operation. A joined-wing configuration of such a craft gives the advantage of a platform for higher resolution sensors. Design challenges emerge with structural flexibility that arise from a long-endurance aircraft design. The goal was to demonstrate that scaling the nonlinear response of a full-scale finite element model of a high-altitude long-endurance (HALE) aircraft was possible if the model was aeroelastically and "nonlinearly" scaled. A straight-forward method of scaling the first three natural vibration frequencies and mode shapes, and the first …

Modular Multi-Stage Axial Compressor Design, Christopher S. Hemerly

Master's Theses - Daytona Beach

Increasingly, companies are becoming more interested in reducing cost. Recent studies indicate that up to 80% of the Lifecycle costs (LCC) has been embedded in the engine's DNA at the end of the development and design phase. One concept to aid in the cost reduction is the modular design of expensive and development-intensive components, such as multi-stage axial compressors. It is the objective of this approach to utilize a "core" module in all the compressors, thus maximizing commonality and minimizing all relevant development, design, manufacture, procurement, and service costs; these reductions in cost are projected to increase affordability by five-fold. …

Global Skin Friction Diagnostics In Complex Separated Flows, Sudesh A. Woodiga

Masters Theses

This work describes the application of a global luminescent oil film skin friction meter to quantitative global skin friction diagnostics in complex separated flows. The development of this technique is based on the relationship between the oil film thickness and luminescent intensity of an oil film mixed with a luminescent dye. The projected thin oil film equation is given to relate the normalized luminescent intensity with skin friction. The basis for this technique is the variational solution for the thin oil film equation on the image plane. The variational formulation with a smoothness constraint on skin friction is proposed to …

Analysis Of Cavity Flow And The Effects Of A Rod In Crossflow, Richard David Loewen

Masters Theses

Subsonic cavity flow tests of an L/D = 3.5 cavity, with three different diameter rods in crossflow, 1/8", 3/16", and 1/4", were conducted using the High Speed Wind Tunnel in the University of Tennessee Space Institute’s Gas Dynamic Laboratory. The average Mach number flow over the duration of the four phase testing sequence was 0.52, with a unit Reynolds number of 13.8 x 106. With the use of a dynamic pressure transducer and a laser PIV system, Spectral and Flow Visualization data was collected with aim of investigating the effect of the rods in crossflow on cavity flow. However, for …

Determination Of Vibrational Energy Levels And Transition Dipole Moments Of Co2 Molecules By Density Functional Theory, Zhi Liang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An Efficient Method is Presented to Calculate the Intra-Molecular Potential Energies and Electrical Dipole Moments of CO2 Molecules at the Electronic Ground State by Solving the Kohn-Sham (KS) Equation for a Total of 101 992 Nuclear Configurations. the Projector-Augmented Wave (PAW) Exchange-Correlation Potential Functionals and Plane Wave (PW) Basis Functions Were Used in Solving the KS Equation. the Calculated Intra-Molecular Potential Function Was Then Included in the Pure Vibrational Schrödinger Equation to Determine the Vibrational Energy Eigen Values and Eigen Functions. the Vibrational Wave Functions Combined with the Calculated Dipole Moment Function Were Used to Determine the Transition Dipole Moments. …

Preliminary Design, Flight Simulation, And Task Evaluation Of A Mars Airplane, Dodi Deanne Walker

Masters Theses

A limited aerodynamic, stability and control, and task evaluation of a new rocket-powered Mars airplane design was conducted. The Mars airplane design, designated the Argo VII, was patterned after the NASA ARES-2 design. The aerodynamic and stability and control parameters of the Argo VII were determined using analytical and computational techniques and were comparable to those of the ARES-2. The Argo VII was predicted to be statically stable and damped in all axes on Earth and Mars. A series of flight tests were performed using a MATLAB Simulink-based flight simulation program to assess the performance, longitudinal flying qualities, and mission …

Atomistic-Based Finite Element Simulation Of Carbon Nanotubes, Yang Yang

Dissertations

Since first found in the form of multi-walled carbon nanotubes (MWNTs) by Iijima(1991), carbon nanotube (CNT) for its outstanding and unique properties have gained overwhelming attentions from across the spectrum of the science and engineering fields. CNTs are structurally perfect, small size, low density, high stiffness, high strength (Qian et al., 2002), and their electronic properties depend on the particular distortion as well as the initial tube diameter and chirality, ranging from narrow-gap or moderate-gap semiconducting to metallic (Pantano et al., 2004b), which can be utilized in nanoscale sensors and devices. These appealing characteristics provide strong drives for the possible …

When Go-Around Is Impossible - Defining The Point Of No Return, Nihad E. Daidzic,, Thomas Peterson

Aviation Department Publications

No abstract provided.

Biogeography-Based Optimization, Daniel J. Simon

Electrical and Computer Engineering Faculty Publications

Biogeography is the study of the geographical distribution of biological organisms. Mathematical equations that govern the distribution of organisms were first discovered and developed during the 1960s. The mindset of the engineer is that we can learn from nature. This motivates the application of biogeography to optimization problems. Just as the mathematics of biological genetics inspired the development of genetic algorithms (GAs), and the mathematics of biological neurons inspired the development of artificial neural networks, this paper considers the mathematics of biogeography as the basis for the development of a new field: biogeography-based optimization (BBO). We discuss natural biogeography and …

Modeling, Designing, Fabricating, And Testing Of Channel Panel Flat Plate Heat Pipes, James R. Harris

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Flat plate heat pipes are very efficient passive two-phase heat transport devices. Their high efficiency and low mass are desirable in the aerospace and electronics industries. The highly competitive nature of the thermal management industry results in little awareness of the capabilities of at plate heat pipes, which has resulted in only a few applications of the technology. In the year 2000 a research and development project sponsored by Space Dynamics Laboratory was launched to investigate building carbon-based at heat pipes. The flat configuration is desireable to incorporate many components onto one thermal management system. Development led to the adoption …

Angles-Only Navigation For Autonomous Orbital Rendezvous, David Charles Woffinden

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The proposed thesis of this dissertation has both a practical element and theoretical component which aim to answer key questions related to the use of angles-only navigation for autonomous orbital rendezvous. The first and fundamental principle to this work argues that an angles-only navigation filter can determine the relative position and orientation (pose) between two spacecraft to perform the necessary maneuvers and close proximity operations for autonomous orbital rendezvous. Second, the implementation of angles-only navigation for on-orbit applications is looked upon with skeptical eyes because of its perceived limitation of determining the relative range between two vehicles. This assumed, yet …

Development Of Modular Thermal Control Architecture For Modular Satellites, Quinn Eric Young

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Research has been completed to determine the most effective thermal control architecture for modular satellites. This research investigated principles of modularity, modular spacecraft examples, thermal control methods, and advanced thermal control technologies. A modular spacecraft was designed as a case study to determine key influences and issues. A number of thermal control architectures were developed. Each was evaluated for compatibility with modularity principles, thermal control performance, and a realizable implementation. Thermal control performance was determined by simulating on-orbit conditions for a number of design reference missions, including traditional thermal control architecture used for comparison. An effective thermal control architecture was …

Application Of Parent-Child Uav Tasking For Wildfire Detection And Response, Stephen T. Kubik

Master's Theses

In recent years, unmanned aerial vehicles (UAVs) have become a dominant force in the aerospace industry. Recent technological developments have moved these aircraft from remote operation roles to more active response missions. Of particular interest is the possibility of applying UAVs toward solving complex problems in long-endurance missions. Under that belief, the feasibility of utilizing UAVs for wildfire detection and response was investigated in a partnership that included NASA’s Aeronautics Research Mission Directorate and Science Mission Directorate, and the United States Forest Service. Under NASA’s Intelligent Mission Management (IMM) project, research was conducted to develop a mission architecture that would …

Optimizing The Use Of The United States Army Oh-58d Helicopter Simulator And Aircraft For Full-Authority Digital Electronic Control Manual Throttle Training, Conrad Rodgers

Masters Theses

Over the past decade the United States Army has used a Full-Authority Digital Electronic Control (FADEC) system to control fuel flow to the engine of the OH-58D helicopter. Currently, part of the training is primarily conducted for the scenario of a FADEC system failure in the aircraft. Because of the complexity of this task, a number of accidents have occurred resulting in minor to severe damage to the aircraft. The United States Army has recently fielded two OH-58D Operational Flight Training Simulators in an effort to increase training efficiency and effectiveness. It is anticipated that the simulators will provide a …

Wire-Braced Semirigid Elevated Rotor System Concept For A Human-Powered Helicopter, Jonathan Richard Silvester

Theses and Dissertations

In order for a human-powered helicopter (HPH) to fly, lifting the weight of its human pilot-engine and the weight of its own structure, the rotary wings need to be extremely large and exceptionally lightweight. Through centuries of dreaming and decades of modern attempts, no design so far has been able to obtain the combination of an adequately large rotor size, sufficiently lightweight structure, and an inherently stable aircraft. This thesis describes a concept of a wire-braced semi-rigid elevated rotor system for a proposed HPH. Then, using scale models and quantitative analysis, tests a series of supporting hypotheses in order to …

A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

It remains a big challenge to theoretically predict the material removal mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of nonmetals have been based on the free electron density distribution without the actual consideration of the phase change mechanism. However, this widely used key assumption needs further theoretical and experimental confirmation. by combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through nonthermal processes (the Coulomb explosion and electrostatic ablation). The predicted …

Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as …

Control And Sensor Development On A Four-Wheel Pyramidal Reaction Wheel Platform, Jeffery Jay Logan

Master's Theses

The Pyramidal Reaction Wheel Platform, or PRWP, is used to simulate three-axis controls in a torque free space-like environment. The primary purpose of the system will be to evaluate the effects of conjoining sensors to maximize pointing accuracy. Furthermore, the system will incorporate a star tracker in conjunction with a Simulated Star Field (SSF) to better estimate the PRWP orientation. For the sake of this document, however, the goal is to implement a gyroscope, wheel rate sensors, and a make-shift accelerometer—to the PRWP—and integrate a controls algorithm such that three-axis controls are achieved for the PRWP. Three sensors were either …

Extension Of Viscoplasticity Based On Overstress To Capture The Effects Of Prior Aging On The Time Dependent Deformation Behavior Of A High-Temperature Polymer: Experiments And Modeling, Amber J. W. Mcclung

Theses and Dissertations

The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at 288 degrees C. The experimental program was designed to explore the influence of strain rate on tensile loading, unloading, and strain recovery behaviors. In addition, the effect of the prior strain rate on the relaxation response of the material, as well as on the creep behavior following strain controlled loading were examined. The experimental data were modeled with the Viscoplasticity Based on Overstress (VBO) theory. A systematic procedure for determining model parameters was developed and the model was employed to predict the response of the …

Flightlines, Vol. 16, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Numerical Simulation Of Uva Ramjet/Scramjet Hypersonic Engine With Hydrogen-Air Combustion Using Wind-Us, Vishal Anand Bhagwandin

Master's Theses - Daytona Beach

The internal flowpath of University of Virginia's Mach 5, direct-connect, dual-mode scramjet engine was simulated using Wind-US, a density-based Reynolds-Averaged Navier-Stokes flow solver. Detailed flowfield simulation results are directly compared to experimental data to evaluate the accuracy of the numerical model and to provide insight into the flowfield behavior. Four hydrogen-air reaction mechanisms were initially assessed using the Burrows-Kurkov case. An Evans-Schexnayder, 7-specie, 8-reaction set with third body efficiencies was then selected for the scramjet simulations. The scramjet simulations included one fuel-off case and two reacting cases with different equivalence ratios, all with clean, non-vitiated air supply. The strong sensitivity …

Study Of The Influence Of Nacelle And Pylon On Aerodynamics Of A New Vu Design, Romain Larose

Master's Theses - Daytona Beach

The purpose of this thesis was to illustrate the influence of the nacelle and pylon on aerodynamics of a new Very Light Jet design, using Computational Fluid Dynamics.

The objective of the first phase was to repair the existing CATIA model in order to facilitate the meshing process.

The second and third phase was to create two meshes: a mesh for the complete model (aircraft with nacelle and pylon), and a second for the aircraft alone.

The two problems have been solved at cruise conditions using Navier-Stokes equations with a second order accuracy.

The model complying with theory, the results …

Design And Numerical Evaluation Of A Counter- Rotating Compressor In The Absence Of Boundary Layer Control: Part I, Naiara Petralanda

Master's Theses - Daytona Beach

The purpose of this thesis was to design and evaluate a three stage counter-rotating compressor that employed well established design principles and technologies using a phased approach. The objective of the first phase was to generate the preliminary annulus shape and estimate the major parameters by modeling the flow as inviscid and time independent. The second and third phases refined the design approximating the flow using Euler's equations and the Navier-Stokes equations respectively.

The performance predictions decreased as the design move forward and more accurate flow and loss models were used. The final three dimensional analysis, which was limited to …

High Bandwidth Control Of Precision Motion Instrumentation, Douglas A. Bristow, Jingyan Dong, Andrew G. Alleyne, Srinivasa M. Salapaka, Placid M. Ferreira

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This article presents a high-bandwidth control design suitable for precision motion instrumentation. Iterative learning control (ILC), a feedforward technique that uses previous iterations of the desired trajectory, is used to leverage the repetition that occurs in many tasks, such as raster scanning in microscopy. Two ILC designs are presented. The first design uses the motion system dynamic model to maximize bandwidth. The second design uses a time-varying bandwidth that is particularly useful for nonsmooth trajectories such as raster scanning. Both designs are applied to a multiaxis piezoelectric-actuated flexure system and evaluated on a nonsmooth trajectory. The ILC designs demonstrate significant …

Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing process that extrudes high solids loading aqueous ceramic pastes in a layer-by-layer fashion below the paste freezing temperature for component fabrication. Due to effects such as the air bubble release, agglomerate breakdown, change in paste properties during extrusion as a result of liquid phase migration, etc., the extrusion force is difficult to control. In this paper, an adaptive controller is proposed to regulate the extrusion force. Recursive Least Squares is used to estimate extrusion force model parameters during fabrication and a low-order control scheme capable of tracking general reference trajectories is designed …

Pylon Effects On A Scramjet Cavity Flameholder Flowfield, Andrew B. Freeborn

Theses and Dissertations

Cavity flameholders in supersonic combustion ramjet (scramjet) combustors, while effective, fail to take advantage of the full combustor volume. Adding a pylon to the leading edge of a cavity flameholder generates a flowfield increasing mass exchange between the cavity and main combustor flow, increasing the mixing interface between flameholder products and main combustor flow, and exhibiting minimal Reynolds number effects. To demonstrate this modified flowfield driven by supersonic expansion behind the pylon, pylon-cavity flameholder flowfield data were obtained through a combination of wind tunnel experimentation and steady-state computational fluid dynamics (CFD). Flowfield effects of the pylon-cavity were examined at a …

Hypermixer Pylon Fuel Injection For Scramjet Combustors, Jason C. Doster

Theses and Dissertations

Fueling the core airflow of a circular or elliptical scramjet combustor cross-section often requires intrusive geometries. Intrusive geometries can distribute the fuel evenly across the combustor cross-section and act as a flameholder for the fuel/air mixture. Compared to conventional transverse or angled wall injection, intrusive geometries allow easier penetration into the core combustor airflow and reduced fuel injection pressures. The design and testing of an intrusive pylon geometry for scramjet combustor fueling is the subject of this research. Three pylon configurations are compared: a basic pylon, a ramp pylon, and an alternating wedge pylon. All three pylon configurations exhibit the …

Modeling And Parameter Estimation Of Spacecraft Lateral Fuel Slosh, Yadira Rodriguez Chatman

Master's Theses - Daytona Beach

Predicting the effect of fuel slosh on spacecraft and launch vehicle attitude control systems has been a very important and challenging task and has been the subject of considerable research over the past years. Analytic determination of the slosh analog parameters has been met with mixed success and is made more difficult by the introduction of propellant management devices such as elastomeric diaphragms. The experimental set-up in this research incorporates a diaphragm in a simulated spacecraft fuel tank subjected to lateral slosh behavior. This research focuses on the parameter estimation of a SimMechanics model of the simulated spacecraft propellant tank …