Engineering Commons^™

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 …

Algorithm For Geodetic Positioning Based On Angle-Of-Arrival Of Automatic Dependent Surveillance-Broadcasts, Richard Allen Gross

Masters Theses

This paper develops a non-precision, three-dimensional, geodetic positioning algorithm for airborne vehicles. The algorithm leverages the proliferation of Automatic Dependent Surveillance – Broadcast (ADS-B) equipped aircraft, utilizing them as airborne navigation aids to generate an RF Angle-of-Arrival (AOA) and Angle-of-Elevation (AOE) based geodetic position. The resulting geodetic position can serve as a redundant navigation system for use during locally limited Global Navigation Satellite System (GNSS) availability, be used to validate on-board satellite navigation systems in an effort to detect local spoofing attempts, and be used to validate ADS-B position reports.

The navigation algorithm is an implementation of an Extended Kalman …

Control Law Synthesis For Lockheed Martin’S Innovative Control Effectors Aircraft Concept, Cameron James Segard

Masters Theses

This thesis documents a conventional and modern flight control system design process carried out on a tailless aircraft Simulink model with innovative control effectors provided by Lockheed Martin. To set scope and design requirements a performance analysis was carried out to categorize the aircraft. Evaluation of open-loop dynamics reveled modal instabilities as well as state and control coupling. Flight condition dependent pole migration mapping reveled large changes in the aircraft’s static stability. Leading to the development of a four channel proportional-integral- derivative (PID) stability and control augmentation system (SCAS) controlling pitch-rate, roll-rate, side-slip angle, and airspeed states. PID gains are …

Model Predictive Control Synthesis For The Innovative Control Effector Tailless Fighter Aircraft, Christopher Proctor

Masters Theses

A nonlinear model predictive control law was developed for the Lockheed Martin Innovative Control Effector tailless fighter aircraft to track way points. In general, aircraft are described by nonlinear dynamics that are dependent on the regime of flight. Additionally strict requirements on state and actuator constraints are common to all aircraft. Tailless aircraft are usually overdetermined systems, meaning solutions to control problems are not unique, and the system is non-affine. The proposed nonlinear control law considers those constraints during run-time, and solves the nonlinear control problem for a range of points within different flight regimes. The control law was developed …

Insar Simulations For Swot And Dual Frequency Processing For Topographic Measurements, Gerard Masalias Huguet

Masters Theses

In Earth remote sensing precise characterization of the backscatter coefficient is important to extract valuable information about the observed target. A system that eliminates platform motion during near-nadir airborne observations is presented in this thesis, showing an improvement on the accuracy of measurements for a Ka- band scatterometer previously developed at Microwave Remote Sensing Laboratory (MIRSL). These very same results are used to simulate the reflectivity of such targets as seen from a spaceborne radar and estimate height errors based on mission-specific geometry. Finally, data collected from a dual-frequency airborne interferometer com- prised by the Ka-band system and an S-band …

Laser Machining Countersinks In Carbon Fiber Reinforced Polymer, Leon James Neely Hill

Masters Theses

“Laser machining countersinks with a frequency doubled Q-switched diode pumped Nd:YAG laser is demonstrated. Tests were conducted in 0.100" thick IM7 prepreg CFRP with [0,90]3S orientation. The HAZ is minimized to avoid stress concentrations in the epoxy matrix. A chamber and filtration system was designed and built to contain the byproducts produced in the machining process. The variables investigated are the number of repetitions in the offset path, the plunge rate, and the line energy. The research was performed over one baseline study, one parameter space exercise, two full factorial experiments, and one repeatability study. Assessment was done under an …

Effects Of Uncertainty Refinement On Satellite Collision Probability, Bruce Thomas Morrison

Masters Theses

"Due to the drastic increase in orbital debris about the Earth, the likelihood for new and current mission satellites to collide with other objects grows. When a mission satellite is placed in a highly populated orbit in the vicinity of other satellites or debris, it is necessary to consider the probability of collision to assess any possible conjunctions. The computation of the collision probability is heavily dependent on the relative position and velocity of the objects during conjunction, as well as the combined covariance. There are two main types of analytic collision probability computations; the first assumes that the objects …

Program Management For Concurrent University Satellite Programs, Including Propellant Feed System Design Elements, Shannah Withrow-Maser

Masters Theses

"Propulsion options for CubeSats are limited but are necessary for the CubeSat industry to continue future growth. Challenges to CubeSat propulsion include volume/mass constraints, availability of sufficiently small and certified hardware, secondary payload status, and power requirements. A multi-mode (chemical and electric) thruster was developed by at the Missouri University of Science and Technology to enable CubeSat propulsion missions. Two satellite buses, a 3U and 6U, are under development to demonstrate the multi-mode thruster's capabilities. Two key challenges related to these missions are the development of the feed system to support the thruster and management of the two bus programs' …

Analyzing The Effects Of Attitude Errors When Quantifying The On-Orbit Performance Of A Cubesat Micropropulsion System, Andrew Orion Watson

Masters Theses

"CubeSats and small satellites have become popular methods of performing space research. Accordingly, interest has also grown in designing micropropulsion systems to increase the lifespan of these satellites. This work describes the framework for analyzing the effects of imperfect attitude determination and control when quantifying the on-orbit performance of a micropropulsion system. The Gauss variation of parameters equations were implemented to model the orbital mechanics, with perturbing models for the zonal harmonics, atmospheric drag, and solar radiation pressure included. Two common sources for imperfections in a spacecraft's attitude were considered. The first was to consider the effect of the spacecraft …

Propagation Of Uncertainty Through Coning, Sculling, And Scrolling Corrections For Inertial Navigation, James Daniel Alan Brouk

Masters Theses

"This thesis investigates the propagation of estimation errors through generalized coning, sculling, and scrolling algorithms used in modern day inertial navigation systems, in order to accurately quantify the uncertainty in the estimation of position, velocity, and attitude. The corrections for coning, sculling, and scrolling algorithms have an often unaccounted for effect on documented and empirically derived error statistics for measurements used to predict the uncertainty in a vehicle's position, velocity, and attitude estimates. Through the development of an error analysis for these generalized algorithms, mappings of the measurement and estimation errors through the correction termare generated. Using the developed mappings, …

Small Satellite Earth-To-Moon Direct Transfer Trajectories Using The Cr3bp, Garrett Levi Mcmillan

Masters Theses

"The CubeSat/small satellite field is one of the fastest growing means of space exploration, with applications continuing to expand for component development, communication, and scientific research. This thesis study focuses on establishing suitable small satellite Earth-to-Moon direct-transfer trajectories, providing a baseline understanding of their propulsive demands, determining currently available off-the-shelf propulsive technology capable of meeting these demands, as well as demonstrating the effectiveness of the Circular Restricted Three Body Problem (CR3BP) for preliminary mission design. Using the CR3BP and derived requirements from NASA's Cube Quest Challenge, five different trajectory scenarios were analyzed for their propulsive requirements. Results indicate that the …