Engineering Commons^™

Multiple Discharges Before Leader Inception In Long Air Gaps Under Positive Switching Impulses, Xiangen Zhao, Juhyeong Lee, Gang Liu, Lei Jia, Yang Liu, Junjia He, Yaping Du

Mechanical and Aerospace Engineering Faculty Publications

There are multiple corona bursts before leader inception when the rising rate of the applied voltage or electric field is not sufficiently high enough in long positive sparks. In existing studies, no attention has been paid to whether these corona bursts occur in the same location, and they are mostly considered directly as belonging to the same discharge. However, this paper presents that in a typical rod-plate long air gap, the multiple corona bursts before leader inception are distributed in at least two different locations, and the highest probability of three discharges occurs. Also, the discharge occurs with the highest …

Design Of Composite Double-Slab Radar Absorbing Structures Using Forward, Inverse, And Tandem Neural Networks, Devin Nielsen, Juhyeong Lee, Young-Woo Nam

Mechanical and Aerospace Engineering Faculty Publications

The survivability and mission of a military aircraft is often designed with minimum radar cross section (RCS) to ensure its long-term operation and maintainability. To reduce aircraft’s RCS, a specially formulated Radar Absorbing Structures (RAS) is primarily applied to its external skins. A Ni-coated glass/epoxy composite is a recent RAS material system designed for decreasing the RCS for the X-band (8.2 – 12.4 GHz), while maintaining efficient and reliable structural performance to function as the skin of an aircraft. Experimentally measured and computationally predicted radar responses (i.e., return loss responses in specific frequency ranges) of multi-layered RASs are expensive and …

Hyper-Velocity Impact Performance Of Foldcore Sandwich Composites, Nathan Hoch, Chase Mortensen, Juhyeong Lee, Khari Harrison, Kalyan Raj Kota, Thomas Lacy

Mechanical and Aerospace Engineering Faculty Publications

A foldcore is a novel core made from a flat sheet of any material folded into a desired pattern. A foldcore sandwich composite (FSC) provides highly tailorable structural performance over conventional sandwich composites made with honeycomb or synthetic polymer foam cores. Foldcore design can be optimized to accommodate complex shapes and unit cell geometries suitable for protective shielding structures

This work aims to characterize hypervelocity impact (> 2000 m/s, HVI) response and corresponding damage morphologies of carbon fiber reinforced polymer (CFRP) FSCs. A series of normal (0° impact angle) and oblique (45° impact angle) HVI (~3km/s nominal projectile velocity) impact …

Predicting Stochastic Lightning Mechanical Damage Effects On Carbon Fiber Reinforced Polymer Matrix Composites, Juhyeong Lee, Syed Zulfiqar Hussain Shah

Mechanical and Aerospace Engineering Faculty Publications

Three stochastic air blast models are developed with spatially varying elastic properties and failure strengths for predicting lightning mechanical damage to AS4/3506 carbon/epoxy composites subjected to < 100 kA peak currents: (1) the conventional weapon effects program (CWP) model, (2) the coupled eulerianlagrangian (CEL) model, and (3) the smoothed-particle hydrodynamics (SPH) model. This work is an extension of our previous studies [1–4] that used deterministic air blast models for lightning mechanical damage prediction. Stochastic variations in composite material properties were generated using the Box-Muller transformation algorithm with the mean (i.e., room temperature experimental data) and their standard deviations (i.e., 10% of the mean herein as reference). The predicted dynamic responses and corresponding damage initiation prediction for composites under equivalent air blast loading were comparable for the deterministic and stochastic models. Overall, the domains with displacement, von-Mises stress, and damage initiation contours predicted in the stochastic models were somewhat sporadic and asymmetric along the fiber’s local orientation and varied intermittently. This suggests the significance of local property variations in lightning mechanical damage prediction. Thus, stochastic air blast models may provide a more accurate lightning mechanical damage approximation than traditional (deterministic) air blast models. All stochastic models proposed in this work demonstrated satisfactory accuracy compared to the baseline models, but required substantial computational time due to the random material model generation/assignment process, which needs to be optimized in future work.

Collaborative Research: Harnessing Mechanics For The Design Of All-Solid-State Lithium Batteries, Haoran Wang

Funded Research Records

No abstract provided.

Control Mapping Methodology For Tailless Morphing-Wing Aircraft, Zachary S. Montgomery

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Advanced aircraft designs tend to have several control surfaces or devices that affect the flight of the aircraft. It is difficult or even impossible for a pilot to directly control each of these devices and fly the aircraft well. Therefore, a control mapping logic is needed to take typical pilot commands and map them to what the control devices should do to achieve the pilot’s commands. This work presents a methodology for determining this control mapping logic using two different approaches. The first uses a theoretical approach based on lifting-line theory, while the second leverages computational methods. The methodology consists …

Fabrication And Testing Of Catalyst-Infused Filament For 3d Printing Of Ignition-Augmented Hybrid Rocket Fuels, Kurt C. Olsen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis describes and addresses the need for reliable ignition in small satellite hybrid propulsion systems using higher density oxidizers. It describes methods of creating custom 3D printing ABS plastic based filaments that contain small amounts of catalysts. These catalysts lead to a more reliable and energy-efficient ignition of a hybrid rocked propulsion system using catalyst-infused ABS and nitrous oxide and oxygen blend called Nytrox, commonly known as ”laughing gas.” The ”laughing gas” has a higher density and can therefore provide more ”miles per gallon” in a hybrid propulsion system on a small satellite when compared to gaseous oxygen (GOX). …

Schlieren Techniques For Observations Of Long Positive Sparks: Review And Application, Junjia He, Xiankang Wang, Xiangen Zhao, Juhyeong Lee, Yaping Du, Xiaopeng Liu, Quan Gan, Yang Liu, Yuqin Liao

Mechanical and Aerospace Engineering Faculty Publications

Understanding the mechanism of positive leader discharge is important in lightning protection engineering and the external insulation design in high voltage power transmission systems. During the propagation of a positive leader, some processes without light-emitting, for example, the insulation recovery process after the breakdown, cannot be observed by optical photography techniques. With the combination of the digital high-speed imaging system, the conventional Schlieren techniques offer new vistas in the long air gap discharge observation. The important features of high spatial resolution, high sensitivity, and easy arrangement make Schlieren techniques powerful and effective tools for characterising the discharge processes without light-emitting. …

Optimal Relative Path Planning For Constrained Stochastic Space Systems, Nathan Bohus Stastny

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Rendezvous and proximity operations for automated spacecraft systems requires advanced path planning techniques that are capable of generating optimal paths. Real-world constraints, such as sensor noise and actuator errors, complicate the planning process. Operations also require flight safety considerations in order to prevent the spacecraft from potentially colliding with the associated companion spacecraft. This work proposes a new, ground-based trajectory planning approach that seeks an optimal trajectory while meeting all mission constraints and accounting for vehicle performance and safety requirements. This approach uses a closed-loop linear covariance simulation of the relative trajectory coupled with a genetic algorithm to determine fuel …

A Study Of Wings With Constant And Variable Sweep For Aerodynamic Efficiency In Inviscid Flow, Bruno Moorthamers

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Wing sweep has been studied by industry and academia since the pioneering days of aviation for both high-speed and low-speed applications. In transonic and supersonic flight regimes it serves to delay the onset of compressibility effects and decrease wave drag. In subsonic conditions, flying wing designs sweep back the main lifting surface in such a way that it can be used for longitudinal stability and control, to allow for the elimination of a traditional empenage. This is desirable because it can decrease the aerodynamic drag. Sweep can also be seen in nature in the wings of birds and fins of …

A Review Of Avian-Inspired Morphing For Uav Flight Control, Christina Harvey, Lawren L. Gamble, Christian R. Bolander, Douglas F. Hunsaker, James J. Joo, Daniel J. Inman

Mechanical and Aerospace Engineering Faculty Publications

The impressive maneuverability demonstrated by birds has so far eluded comparably sized uncrewed aerial vehicles (UAVs). Modern studies have shown that birds’ ability to change the shape of their wings and tail in flight, known as morphing, allows birds to actively control their longitudinal and lateral flight characteristics. These advances in our understanding of avian flight paired with advances in UAV manufacturing capabilities and applications has, in part, led to a growing field of researchers studying and developing avian-inspired morphing aircraft. Because avian-inspired morphing bridges at least two distinct fields (biology and engineering), it becomes challenging to compare and contrast …

Impact Of Covid-19 On Aviation-Wildlife Strikes Across Europe, Isabel C. Metz, Marta Giordano, Dionysios Ntampakis, Marianna Moira, Anneke Hamann, Rosanne Blijleven, Jürgen J. Ebert, Alessandro Montemaggiori

Human–Wildlife Interactions

Collisions between aircraft and wildlife (i.e., wildlife strikes) pose a serious threat toward the safety of aircraft, its crew, and passengers. The effects of COVID-19 related travel restrictions on wildlife strikes are unknown. With this study, we aim to address this information gap by assessing the changes of wildlife hazard management performance across European airports during the lockdown period (e.g., period of reduced operations and borders closure in spring 2020). We also sought to raise awareness of the importance of wildlife strike prevention in times of reduced operations. The objective of our study was to compare wildlife strike data before …

Attainable Moment Set And Actuation Time Of A Bio-Inspired Rotating Empennage, Christian R. Bolander, Douglas F. Hunsaker, David Myszka, James J. Joo

Mechanical and Aerospace Engineering Faculty Publications

Future tactical aircraft will likely demonstrate improvements in efficiency, weight, and control by implementing bio-inspired control systems. This work analyzes a novel control system for a fighter aircraft inspired by the function of – and the degrees of freedom available in – a bird’s tail. The control system is introduced to an existing fighter aircraft design by removing the vertical tail and allowing the horizontal tail surfaces to rotate about the roll axis. Using a low-fidelity aerodynamic model, an analysis on the available controlling moments and actuation speeds of the baseline aircraft is compared to that of the bio-inspired rotating …

Airframe And Systems Design, Analysis, And Testing Of The Horizon Morphing-Wing Aircraft, Sabrina A. Snow

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Morphing trailing edge technology can provide the ability to dynamically alter the twist distribution, and therefore lift distribution, of an aircraft during flight. There are certain optimal lift distributions which can be chosen to create proverse yawing effects and eliminate the need for vertical control surfaces. The purpose of this project is to support the design and testing of a morphing, crescent flying wing airframe which will be used to evaluate yaw control in an aircraft without vertical control surfaces. There are three main objectives of this project, which are to perform static and dynamic analysis on the crescent wing …

Thermal Barrier Coating For Carbon Fiber-Reinforced Composite Materials, Heejin Kim, Jungwon Kim, Juhyeong Lee, Min Wook Lee

Mechanical and Aerospace Engineering Faculty Publications

Carbon fiber-reinforced plastic (CFRP) composites are widely employed in lightweight and high performance applications including supercars, aero-vehicles, and space components. However, although carbon fibers are thermally stable, the low thermal endurance of the matrix materials remains a critical problem in terms of the performance of the material. In this study, we proposed a new, Al₂O₃-based thermal barrier coating (TBC) for the CFRP composites. The TBC comprised α-phase Al₂O₃ particles with a mean diameter of 9.27 μm. The strong adhesion between the TBC and the CFRP substrate was evaluated using a three point bending …

Comparison Of Theoretical And Multi-Fidelity Optimum Aerostructural Solutions For Wing Design, Jeffrey D. Taylor, Douglas F. Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

As contemporary aerostructural research for aircraft design trends toward high-fidelity computational methods, aerostructural solutions based on theory are often neglected or forgotten. In fact, in many modern aerostructural wing optimization studies, the elliptic lift distribution is used as a benchmark in place of theoretical aerostructural solutions with more appropriate constraints. In this paper, we review several theoretical aerostructural solutions that could be used as benchmark cases for wing design studies, and we compare them to high-fidelity solutions with similar constraints. Solutions are presented for studies with 1) constraints related to the wing integrated bending moment, 2) constraints related to the …

Lightning Arc Channel Effects On Surface Damage Development On A Prseus Composite Panel: An Experimental Study, Dounia Boushab, Pedram Gharghabi, Juhyeong Lee, Thomas E. Lacy Jr., Charles U. Pittman Jr., Michael S. Mazzola, Alexander Velicki

Mechanical and Aerospace Engineering Faculty Publications

Composite aircraft structures are vulnerable to lightning strike damage due to their relatively low electrical and thermal conductivities. A preceding work has investigated the lightning damage resistance of a carbon-epoxy Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panel. The damage includes intense local damage (i.e., matrix decomposition/sublimation, fiber rupture, delamination) accompanied by widespread surface damage (i.e., distributed fiber rupture and tow splitting) further from the lightning attachment point. This study focuses on investigating the cause of the widespread surface damage. Two possible driving mechanisms are explored: i) magnetically-induced currents and ii) lightning arc-root/channel expansion. …

Navigation Performance Of Line/Plane Intersection Lidar Model In Conjunction With Opportunistic Feature Tracker, Michael R. Hansen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

With NASA awarding numerous contracts to build commercial lunar payload spacecraft and human lunar landers, the need for high precision navigation has increased. Traditional inertial navigation alone is not sufficient to autonomously land a vehicle on hazardous lunar terrain. Terrain relative navigation (TRN) systems have been explored in previous research that exploit camera observations of known landmarks. Such approaches require the flight electronics to correctly match features of the observed landmarks to an onboard database, in the drastically varying lighting conditions of moon. This paper explores the performance of a TRN system that does not rely on apriori landmark identification, …

Exact And Approximate Relaxation Techniques For Computational Guidance, Sheril Avikkal Kunhippurayil

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The focus of this dissertation is in the development and application of relaxation techniques that enable efficient and real-time solution of complex computational guidance problems. Relaxations transform a non-convex constraint into a convex constraint and provides proof that the optimal solutions to the relaxed problem are optimal for the original problem. Unique contributions of this work include: 1) a relaxation technique for solving fixed final time problems between fixed points, 2) a performance analysis on the application of computational guidance for the Mars Ascent Vehicle, and 3) establishment of sufficient conditions for non-singularity of optimal control for problems on a …

3d-Printed Morphing Wings For Controlling Yaw On Flying-Wing Aircraft, Benjamin C. Moulton

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The flaps on an airplane wing are used to control the aircraft during flight. These flaps traditionally have at most three articulation or hinge points. Recent studies have shown improved flap efficiency using a conformal flap, which deforms following a curved shape. Much of aircraft improvement comes through increasing its efficiency during flight. This efficiency is generally improved by decreasing the drag force on the aircraft. A potential solution to decrease drag is to remove additional lifting surfaces, such as the horizontal and vertical stabilizer ubiquitous on general aviation aircraft. These additional lifting surfaces are used to trim and control …

Passive Cavity Deflation After Water Entry Facilitated By A Vented Tube, Emma R. Fraley

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

When an object enters water, a crater, or air cavity, can form around the object and remain attached as the object travels underwater. Cavities can be beneficial and reduce drag force but there may be times when the cavity needs to be removed. This research proposes a method to remove air cavities by letting air leave the cavity, deflating the cavity similar to how a balloon is deflated. To provide air a path to leave the cavity, a tube with vent holes is attached to the object. The vent holes are located near the object, where the air cavity forms, …

Attitude And Reflection Parameter Estimation Of Resident Space Objects Using Ground-Based Photometry, Arun J. Bernard

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

There are currently thousands of objects orbiting Earth, and this number is only going to increase. Larger number of satellites will require that operators have a greater knowledge of the state their assets. Electro-optical telescopes are currently being used to observe and track many of these objects. When using these telescopes to take images of satellites, they often appear as dots in the image. Depending on the surface properties of the satellite, and its orientation at a given time, the dots in the image can appear brighter or dimmer. Photometry measurements are a quantification of how bright the object appears. …

Development Of An Anisotropic Thermal Stress Model For A Low-Erosion Hybrid Rocket Nozzle System, Judson C. Stephens

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Hybrid rockets are rockets which employ a solid fuel grain with a liquid oxidizer. Hybrids have many promising potential applications, however they also have a few drawbacks. Of interest to this research is the increased rate of nozzle erosion inherent to hybrid rockets. In order to address this issue, a low-erosion nozzle is proposed and evaluated.

Sonic Boom Loudness Reduction Through Localized Supersonic Aircraft Equivalent-Area Changes, Troy A. Abraham

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The NASA University Leadership Initiative (ULI) titled “Adaptive Aerostructures for Revolutionary Civil Supersonic Transportation” looks to study the feasibility of distributed structural adaptivity on a supersonic aircraft for maintaining acceptable en-route sonic boom loudness during overland flight. The ULI includes a team of industry and university partners that are working together to develop and implement the systems necessary to accomplish this goal.

The Utah State University Aerolab is a member of this ULI team and has been tasked with developing and using low-fidelity supersonic aerodynamic and sonic boom predictions tools to rapidly study the effects of localized geometry changes on …

Sensitivity And Estimation Of Aerodynamic, Propulsion, And Inertial Parameters For Rudderless Aircraft Using Simulation, Jaden W. Thurgood

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A technique known as system identification is often used in aircraft design and testing to understand and validate the mathematical parameters that describe the aircrafts stability and handling characteristics. System identification can be thought of as the inverse of simulation. In the world of system identification, we have a physical system that we seek to understand in more detail by monitoring the system with an array of sensors. In short, we conduct tests of an aircraft while recording the inputs and response outputs. Then we take the input and output data and run it through an algorithm that seeks to …

Computational Fluid Dynamics Benchmark Validation Experiment Of Plenum-To-Plenum Flow Through Vertical Heated Parallel Channels, Austin W. Parker

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The next generation of nuclear power plants will have higher efficiency and improved safety, among other benefits; one attractive option is the high temperature gas reactor. An ability to predict the physics that occur within the reactor under normal conditions and accident scenarios is necessary before it receives regulatory licensing for use. The flow through a high temperature gas reactor involves complex interactions of heat transfer, fluids, and solids.

One method for simulating complex fluid dynamics is called Computational Fluid Dynamics. These simulations have already been used to predict the complex fluid flows found in high temperature gas reactors. Predicting …

Low-Fidelity Method For Rapid Aerostructural Optimisation And Design-Space Exploration Of Planar Wings, Jeffrey D. Taylor, Doug F. Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

During early phases of wing design, analytic and low-fidelity methods are often used to identify promising design concepts. In many cases, solutions obtained using these methods provide intuition about the design space that is not easily obtained using higher-fidelity methods. This is especially true for aerostructural design. However, many analytic and low-fidelity aerostructural solutions are limited in application to wings with specific planforms and weight distributions. Here, a numerical method for minimising induced drag with structural constraints is presented that uses approximations that apply to unswept planar wings with arbitrary planforms and weight distributions. The method is applied to the …

Aircraft Input Files For Pylot And Machupx, Jaden Thurgood

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This data was used in an attempt at system identification for rudderless aircraft using simulation.

Characterization Of The Common Research Model Wing For Low-Fidelity Aerostructural Analysis, Jeffrey D. Taylor, Douglas F. Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

A characterization of the Common Research Model (CRM) wing for low-fidelity aerostructural optimization is presented. The geometric and structural properties are based on the CAD geometries and finite-element models for the CRM wing and the undeflected Common Research Model Wing (uCRM). Three approximations are presented for the elastic axis from previously-published studies on wing boxes similar to the uCRM, and approximations of the flexural and torsional rigidity are presented from a previously-published study using the uCRM wing. The characterization presented in this paper is intended to be used within low-fidelity aerostructural analysis tools to facilitate rapid design optimization and exploratory …

Sensitivity And Estimation Of Flying-Wing Aerodynamic, Propulsion, And Inertial Parameters Using Simulation, Jaden Thurgood, Douglas F. Hunsaker

Mechanical and Aerospace Engineering Student Publications and Presentations

This paper explores the difficulties of aircraft system identification, specifically parameter estimation, for a rudderless aircraft. A white box method is used in conjunction with a nonlinear six degree-of-freedom aerodynamic model for the equations of motion in order to estimate 33 parameters that govern the aerodynamic, inertial, and propulsion forces within the mathematical model. The analysis is conducted in the time-domain of system identification. Additionally, all the parameters are estimated using a single flight rather than a series of shorter flights dedicated to estimating specific sets of parameters as is typically done. A final flight plan is developed with a …