Engineering Commons^™

Sun-Synchronous Orbit Slot Architecture Analysis And Development, Eric Watson

Master's Theses

Space debris growth and an influx in space traffic will create a need for increased space traffic management. Due to orbital population density and likely future growth, the implementation of a slot architecture to Sun-synchronous orbit is considered in order to mitigate conjunctions among active satellites. This paper furthers work done in Sun-synchronous orbit slot architecture design and focuses on two main aspects. First, an in-depth relative motion analysis of satellites with respect to their assigned slots is presented. Then, a method for developing a slot architecture from a specific set of user defined inputs is derived.

An Investigation Into Delta Wing Vortex Generators As A Means Of Increasing Algae Biofuel Raceway Vertical Mixing Including An Analysis Of The Resulting Turbulence Characteristics, Aaron H. Godfrey

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Current standards of living and future prosperity are closely tied to the availability of sufficient and inexpensive energy resources. Currently society is fueled primarily by some form of fossil fuel. By their very nature these fuel sources are non-renewable, thus our current energy habits are unsustainable. Among the various renewable energy technologies is the capability to produce diesel fuel by colonies of algae. While this technology has many positive features it remains too expensive to be a realistic fuel source. The current work performed analysis using computer simulation of an aquatic environment commonly used to grow algae for the purposes …

Spacecraft And Propulsion Technician Error, Daniel Clyde Schultz

Doctoral Dissertations and Master's Theses

Commercial aviation and commercial space similarly launch, fly, and land passenger vehicles. Unlike aviation, the U.S. government has not established maintenance policies for commercial space. This study conducted a mixed methods review of 610 U.S. space launches from 1984 through 2011, which included 31 failures. An analysis of the failure causal factors showed that human error accounted for 76% of those failures, which included workmanship error accounting for 29% of the failures. With the imminent future of commercial space travel, the increased potential for the loss of human life demands that changes be made to the standardized procedures, training, and …

Primary And Secondary Flow Interactions In The Mixing Duct Of A 2-D Planer Air Augmented Rocket, Martin Roy Popish

Master's Theses

Experiments were conducted on the Cal Poly air augmented rocket (AAR) in order to characterize two-dimensional flowfield phenomenon occurring in the mixing duct. The testing utilized a direct connect system where high pressure nitrogen is fed into the combustion chamber, to form a primary flow. The high pressure nitrogen is then expanded through a nozzle, with an area ratio of 22 and an exit area of 0.75 in², up to Mach 4.3. Secondary air is entrained from a plenum chamber which is used to create a lower stagnation pressure for the secondary flow. The two flows mix in …

An Inverse Design Method For Supersonic Airfoils, Steven Edward Skare

Master's Theses

Airfoil design is one of the most important aspects of aircraft design. Slight changes in airfoil geometry can lead to significant changes in a wide variety of aircraft performance metrics. Inverse design methods offer an efficient alternative to standard direct methods. The key to this design problem is to derive a direct relationship between changes in airfoil geometry and changes in pressure or velocity distributions. This relationship is then used to modify an initial airfoil and its pressure distribution to match a target pressure distribution, which is specified by design parameters. At this point, the engineer now has a final …

Heat, Mass And Force Flows In Supersonic Shockwave Interactions, John Michael Dixon

UNLV Theses, Dissertations, Professional Papers, and Capstones

There is no cost effective way to deliver a payload to space and, with rising fuel prices, currently the price to travel commercially is also becoming more prohibitive to the public. During supersonic flight, compressive shock waves form around the craft which could be harnessed to deliver an additional lift on the craft. Using a series of hanging plates below a lifting wing design, the total lift generated can be increased above conventional values, while still maintaining a similar lift-to-drag ratio. Here, we study some of the flows involved in supersonic shockwave interaction. This analysis uses ANSYS Fluent Computational Fluid …

Spacecraft Collision Probability Estimation For Rendezvous And Proximity Operations, Michael R. Phillips

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An increasing number of missions require spacecraft to fly in close proximity. Despite the technological advances that have made these types of missions increasingly possible there remains a limit to how accurately the trajectory of a spacecraft can be predicted. As such, one of the main risks to spacecraft in close proximity is the threat of a collision. Many methods exist for computing the probability of collision between spacecraft. These methods incorporate the uncertainty in predicting the spacecrafts motion when computing an estimate. The accuracy and required computation time of these methods very greatly. A poor estimate of collision risk …

Comm-Multiple Access - Slides, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs on "Comm-Multiple Access" from April 24, 2012.

Ec 723 Satellite Communication Systems, Mohammed Khedr

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Mohammed Khdr titled "EC 723 Satellite Communication Systems" from April 10, 2012.

Space Science And Astrophysics Programs, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint presentation created by Professor Bob Twiggs titled "Space Science and Astrophysics Programs" from April 9, 2012.

Asteroid Retrieval Feasibility Study, John Brophy, Fred Culick, Louis Friedman, Pedro Llanos, Et Al.

Publications

This report describes the results of a study sponsored by the Keck Institute for Space Studies (KISS) to investigate the feasibility of identifying, robotically capturing, and returning an entire Near-Earth Asteroid (NEA) to the vicinity of the Earth by the middle of the next decade. The KISS study was performed by people from Ames Research Center, Glenn Research Center, Goddard Space Flight Center, Jet Propulsion Laboratory, Johnson Space Center, Langley Research Center, the California Institute of Technology, Carnegie Mellon, Harvard University, the Naval Postgraduate School, University of California at Los Angeles, University of California at Santa Cruz, University of Southern …

Aerodynamics Of An Aerofoil In Transonic Ground Effect: Numerical Study At Full-Scale Reynolds Numbers, G. Doig, T. J. Barber, A. J. Neely, D. D. Myre

Aerospace Engineering

The potential positive effects of ground proximity on the aerodynamic performance of a wing or aerofoil have long been established, but at transonic speeds the formation of shock waves between the body and the ground plane would have significant consequences. A numerical study of the aerodynamics of an RAE2822 aerofoil section in ground effect flight was conducted at freestream Mach numbers from 0·5 to 0·9, at a range of ground clearances and angles of incidence. It was found that in general the aerofoil's lifting capability was still improved with decreasing ground clearance up until the point at which a lower …

Section Abstracts: Aeronautical And Aerospace Sciences

Virginia Journal of Science

Abstracts of the Aeronautical and Aerospace Sciences Section for the 90th Annual Meeting of the Virginia Academy of Science, May 23-25, 2015. Norfolk State University, Norfolk, Virginia.

A Nanoporous Silicon Nitride Membrane Using A Two-Step Lift-Off Pattern Transfer With Thermal Nanoimprint Lithography, Bhargav P. Nabar, Zeynep Çelik-Butler, Brian H. Dennis, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Nanoimprint lithography is emerging as a viable contender for fabrication of large-scale arrays of 5500 nm features. A fabrication process for the realization of thin nanoporous membranes using thermal nanoimprint lithography is presented. Suspended silicon nitride membranes were fabricated by low-pressure chemical vapor deposition (LPCVD) in conjunction with a potassium hydroxide-based bulk micromachining process. Nanoscale features were imprinted into a commercially available thermoplastic polymer resist using a prefabricated silicon mold. The pattern was reversed and transferred to a thin aluminum oxide layer by means of a novel two-stage lift-off technique. The patterned aluminum oxide was used as an etch mask …

Engineering Innovation And Design For Stem Teachers And The Stem Quality Framework, James Rowley, Sandi Preiss, Margaret Pinnell, Suzanne Franco

Mechanical and Aerospace Engineering Faculty Publications

The backbone of economic growth in the United States relies on engineering innovation. However, engineering innovation cannot occur without engineers and scientists. Unfortunately however, many K-12 students do not have a good understanding of the engineering design process or the vast field of engineering. As a result, many students lose interest in math and science and do not pursue Science, Technology, Engineering and Math (STEM) fields. This paper will describe a unique partnership among the Teacher Education Program and School of Engineering at the University of Dayton (UD) and the Dayton Regional STEM Center (DRSC). This partnership initiated with the …

Peridynamic Model For Dynamic Fracture In Unidirectional Fiber-Reinforced Composites, Wenke Hu, Youn Doh Ha, Florin Bobaru

Department of Mechanical and Materials Engineering: Faculty Publications

We propose a computational method for a homogenized peridynamics description of fiber-reinforced composites and we use it to simulate dynamic brittle fracture and damage in these materials. With this model we analyze the dynamic effects induced by different types of dynamic loading on the fracture and damage behavior of unidirectional fiber-reinforced composites. In contrast to the results expected from quasi-static loading, the simulations show that dynamic conditions can lead to co-existence of and transitions between fracture modes; matrix shattering can happen before a splitting crack propagates. We observe matrix–fiber splitting fracture, matrix cracking, and crack migration in the matrix, including …

High-Fidelity Modeling Of Airfoil Interaction With Upstream Turbulence, Jacob Brodnick

Doctoral Dissertations and Master's Theses

To supplement past research on low speed unsteady airfoil responses to upstream disturbances, this work proposes and investigates a method to generate a turbulent momentum source to be convected downstream and interact with an SD7003 airfoil in a high-fidelity numerical simulation. A perturbation velocity field is generated from a summation of Fourier harmonics and applied to the forcing function in the momentum terms of the Navier Stokes Equations. The result is a three-dimensional, divergence-free, convected turbulent gust with applied statistical parameters. A parametric study has been done in 2D and 3D comparing the resultant flow fields and airfoil interactions for …

The Development Of A Force Balance For Testing Micro Aerial Vehicles, Michael Christopher King

Doctoral Dissertations and Master's Theses

The purpose of this work was to create a six degree of freedom balance that could produce meaningful data for micro aerial vehicles. Research was conducted to investigate the common balance configurations, and the strengths and weaknesses of each configuration were used to select the most appropriate design. The limitations of available fabrication facilities, the desired level of performance and the end user of the balance were all considered to finalize the design. The balance and data acquisition system were fabricated over a period of several months, and unforeseen design issues were handled forthwith. Rigorous calibration and testing processes were …

Design And Optimization Of A Deflagration To Detonation Transition (Ddt) Section, Francisco X. Romo

Doctoral Dissertations and Master's Theses

Throughout the previous century, hydrocarbon-fueled engines have used and optimized the `traditional' combustion process called deflagration (subsonic combustion). An alternative form of combustion, detonation (supersonic combustion), can increase the thermal efficiency of the process by anywhere from 20 - 50%. Even though several authors have studied detonation waves since the 1890's and a plethora of papers and books have been published, it was not until 2008 that the first detonation-powered flight took place. It lasted for 10 seconds at 100 ft. altitude. Achieving detonation presents its own challenges: some fuels are not prone to detonate, severe vibrations caused by the …

Numerical Study Of The Performance Of A Model Scramjet Engine, Ayad Alhumadi

Mechanical & Aerospace Engineering Theses & Dissertations

A computational parametric investigation was conducted to study the effect of variations to several geometric parameters on the performance of a two-dimensional model scramjet engine (square cross section area for 3-D model). Geometric parameters included backstep location, height, and angle and fuel injector angle, diameter, and location. Two- and three-dimensional geometries have been studied, using a finite-volume computational fluid dynamics (CFD) code (FLUENT) with structured grids with sizes between 50,000 and 90,000 cells for the two-dimensional geometry and with structured hexahedral grid sizes between 650,000 and 949,725 cells for the three-dimensional geometry. Otherwise, identical values of program inputs were utilized …

Earth Observation Time Estimates Using Curve Fitted Perturbed Orbit Tracks, Taner Gundogdu

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, time to observation for a generic perturbed low Earth orbit satellite, which is tasked, for reconnaissance of a given surface target is investigated. A curve fitting concept applied to past orbital track data is used to estimate and predict the overflight observation time. The least squares method is selected for the curve fitting process and used for both linear and non-linear aspects. Since orbital track data for actual spacecraft are not widely available, numerical integration of the governing motion equations is used as an alternate data source. One of the numerical integration methods, fourth-order Runge-Kutta, is used …

Effect Of Emergent Technologies On Aircraft Fuel Burn By Seat Class, Lee Matthew Watkins

Mechanical & Aerospace Engineering Theses & Dissertations

In this research, a set of advanced technologies collectively referred to as N+2 technologies, are applied to representative aircraft for seven different seat classes. This study will give a better understanding of which technologies will benefit aircraft of differing sizes compared to current studies which have focused on the fuel efficiency benefits of the N+1 technologies for one size of aircraft. Technologies applied consist of hybrid wing body (HWB) platforms, boundary layer ingestion (BLI) engines, weight reducing technologies, hybrid laminar flow control (HLFC) and advanced engine technologies. The aircraft are modeled in Flight Optimization System (FLOPS), a program developed at …

Dynamics And Control Of Satellite Relative Motion In Proximity Operations, Mohamed Elsayed Aly Abd Elaziz Okasha

Mechanical & Aerospace Engineering Theses & Dissertations

In this dissertation, the development of relative navigation, guidance, and control algorithms of an autonomous space rendezvous and docking system are presented. These algorithms are based on innovative formulations of the relative motion equations that are completely explicit in time. The navigation system uses an extended Kalman filter based on these formulations to estimate the relative position and velocity of the chaser vehicle with respect to the target vehicle and the chaser attitude and gyro biases. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system, along with the star …

Evaluating Network Analysis And Agent Based Modeling For Investigating The Stability Of Commercial Air Carrier Schedules, Sheila Ruth Conway

Engineering Management & Systems Engineering Theses & Dissertations

For a number of years, the United States Federal Government has been formulating the Next Generation Air Transportation System plans for National Airspace System improvement. These improvements attempt to address air transportation holistically, but often address individual improvements in one arena such as ground or in-flight equipment.

In fact, air transportation system designers have had only limited success using traditional Operations Research and parametric modeling approaches in their analyses of innovative operations. They need a systemic methodology for modeling of safety-critical infrastructure that is comprehensive, objective, and sufficiently concrete, yet simple enough to be deployed with reasonable investment. The methodology …

Molecular Dynamics Studies On Nanoscale Gas Transport, Murat Barisik

Mechanical & Aerospace Engineering Theses & Dissertations

Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress …

De-Centralized And Centralized Control For Realistic Ems Maglev Systems, Mohamed M. Aly M. Moawad

Mechanical & Aerospace Engineering Theses & Dissertations

A comparative study of de-centralized and centralized controllers when used with real EMS Maglev Systems is introduced. This comparison is divided into two parts. Part I is concerned with numerical simulation and experimental testing on a two ton six-magnet EMS Maglev vehicle. Levitation and lateral control with these controllers individually and when including flux feedback control in combination with these controllers to enhance stability are introduced. The centralized controller is better than the de-centralized one when the system is exposed to a lateral disturbing force such as wind gusts. The flux feedback control when combined with de-centralized or centralized controllers …

Near Earth Asteroid Mission Design For 2000 Sg344, Gökhan Çahşkan

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, methodologies and capabilities for mission trajectory design to asteroid 2000 SG344 are investigated. Design of orbital trajectories for interplanetary space flight requires application of principles from orbital mechanics including three dimensional orbital element description, orbit propagation, asteroid ephemerides, targeting logic, relative motion dynamics, and numerical algorithm implementation. The thesis research will attempt to assemble and integrate these various topics to achieve a general capability to conduct asteroid mission trajectory design. Further, appropriate methodology including selection of assumptions and models, computation process and flow, and design metrics and trades to achieve a practical and effective trajectory design process …

Increasing Reliability Of A Small 2-Stroke Internal Combustion Engine For Dynamically Changing Attitudes, Steven C. Crosbie

Theses and Dissertations

Remotely Piloted Aircraft (RPA) typically utilize commercial internal combustion engines (ICE) as their power sources. These engines are designed to run at sea level, but these aircraft are often pressed into service at higher altitudes where the performance characteristics deteriorate. A Brison 95cc two-stroke engine's performance characteristics at altitude are investigated using a test facility that can measure these characteristics over a range of pressures and temperatures. With its stock carburetor at sea level static (SLS) conditions, the engine makes 5.5 peak horsepower (hp) and brake specific fuel consumption (BSFC) ranged from 1.2-4.0 lb/(hp-hr). At 10,000 feet conditions, the peak …

Evaluation Of The Thorax Of Manduca Sexta For Flapping-Wing Micro Air Vehicle Applications, Alex C. Hollenbeck

Theses and Dissertations

The tobacco hornworm hawkmoth (Manduca sexta) provides an excellent model from which to garner knowledge pertaining to the development of a Flapping Wing Micro Air Vehicle (FWMAV). Insect-sized FWMAVs will be used by the future warfighter for reconnaissance, nuclear/chemical/biological hazard sensing, and targeting. One of the major challenges facing FWMAV developers is the energetically demanding nature of low Reynolds flapping flight. Investigating the Manduca sexta thorax/wing flapping mechanism as a mechanical system will provide insight into its inherent efficiency. This thesis examined the energetics of the thorax under static loading and dynamic loading using an innovative load-application technique. It was …

Modeling, Simulation, And Flight Test For Automatic Flight Control Of The Condor Hybrid-Electric Remote Piloted Aircraft, Christopher Giacomo

Theses and Dissertations

This thesis describes the modeling and verification process for the stability and control analysis of the Condor hybrid-electric Remote-Piloted Aircraft (HE-RPA). Due to the high-aspect ratio, sailplane-like geometry of the aircraft, both longitudinal and lateral/directional aerodynamic moments and effects are investigated. The aircraft is modeled using both digital DATCOM as well as the JET5 Excel-based design tool. Static model data is used to create a detailed assessment of predictive flight characteristics and PID autopilot gains that are verified with autonomous flight test. PID gain values were determined using a six degree of freedom linear simulation with the Matlab/SIMULINK software. Flight …