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Articles 4921 - 4950 of 11138

Full-Text Articles in Engineering

Military Application Of Aerial Photogrammetry Mapping Assisted By Small Unmanned Air Vehicles, Kijun Lee Mar 2018

Military Application Of Aerial Photogrammetry Mapping Assisted By Small Unmanned Air Vehicles, Kijun Lee

Theses and Dissertations

This research investigated the practical military applications of the photogrammetric methods using remote sensing assisted by small unmanned aerial vehicles (SUAVs). The research explored the feasibility of UAV aerial mapping in terms of the specific military purposes, focusing on the geolocational and measurement accuracy of the digital models, and image processing time. The research method involved experimental flight tests using low-cost Commercial off-the-shelf (COTS) components, sensors and image processing tools to study key features of the method required in military like location accuracy, time estimation, and measurement capability. Based on the results of the data analysis, two military applications are …

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Design And Test Of A Uav Swarm Architecture Over A Mesh Ad-Hoc Network, Timothy J. Allen Mar 2018

Design And Test Of A Uav Swarm Architecture Over A Mesh Ad-Hoc Network, Timothy J. Allen

Theses and Dissertations

The purpose of this research was to develop a testable swarm architecture such that the swarm of UAVs collaborate as a team rather than acting as several independent vehicles. Commercial-off-the-shelf (COTS) components were used as they were low-cost, readily available, and previously proven to work with at least two networked UAVs. Initial testing was performed via software-in-the-loop (SITL) demonstrating swarming of three simulated multirotor aircraft, then transitioned to real hardware. The architecture was then tested in an outdoor nylon netting enclosure. Command and control (C2) was provided by software implementing an enhanced version of Reynolds’ flocking rules via an onboard …

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Optimal Trajectory Generation In A Dynamic Multi-Body Environment Using A Pseudospectral Method, Jacob A. Dahlke Mar 2018

Optimal Trajectory Generation In A Dynamic Multi-Body Environment Using A Pseudospectral Method, Jacob A. Dahlke

Theses and Dissertations

High-altitude parking orbits could provide resiliency to the military space infrastructure by providing redundancy in key assets, allowing for rapid reconstitution of underperforming satellites. When analyzing trajectories in a high-altitude regime, two-body models of Keplerian motion become less accurate since the gravitational effects of other bodies are no longer negligible. To provide a higher fidelity model of the dynamics in a high-altitude regime, a multiple-body model can be used. In the Earth-Moon system, a spacecraft operating in the high-altitude regime can be modeled with three-body dynamics. With certain simplifying assumptions, the model is called the circular-restricted three-body problem (CR3BP). The …

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Algorithms For Small Satellite Formation Flying, Robert B. Larue Mar 2018

Algorithms For Small Satellite Formation Flying, Robert B. Larue

Theses and Dissertations

This thesis presents algorithms for spacecraft formation flying using impulsive thrust and low-thrust methods. The general circular orbit formation initial conditions are derived in terms of equinoctial elements. Physical significance of the bounded relative motion parameters is presented for the case of general circular orbits. The developed algorithms are posed in terms of equinoctial elements for a singularity-free approach. The algorithms are assessed by numerical propagation of the inertial equations of motion with J2 and drag perturbations. Methods are presented for minimizing the ΔV required for formation initialization. An examination of the performance of open-loop and closed-loop control is provided …

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Scheduling Tool For The Nevada Test And Training Range, Miguel J. Macias Mar 2018

Scheduling Tool For The Nevada Test And Training Range, Miguel J. Macias

Theses and Dissertations

Presently, the 57th Wing Scheduler at Nellis AFB schedules daily mission requests to the Nevada Test and Training Range (NTTR) airspace manually. The process is time consuming and may lead to suboptimal range resource allocations. The goal of this study is to provide the scheduler with an automated scheduling approach that will improve range scheduling efficiency. The tool developed uses range request data from units at Nellis AFB to produce daily mission schedules for a month long scheduling horizon with Microsoft VBA code and a commercial Integer Program (IP) solver. Under our current understanding of scheduler priorities, we formulate the …

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Control, Characterization, And Cooling Of An Ultra-Compact Combustor, Kevin J. Demarco Mar 2018

Control, Characterization, And Cooling Of An Ultra-Compact Combustor, Kevin J. Demarco

Theses and Dissertations

An Ultra-Compact Combustor (UCC) is novel alternative to axial flow combustors commonly used in gas turbine engines. The UCC offers multiple benefits to engine design. First, the UCC aims to increase the thrust-to-weight ratio of an aircraft gas turbine engine by decreasing the size, and thus weight, of the engine's combustor. This is done by utilizing a Circumferential Cavity (CC) wrapped around the main core flow which hosts the combustion event, allowing a shortened combustor length. Second, within the CC, the combusting mixture is subjected to a high centrifugal loading which aids combustion by improving both flame propagation and residence …

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Analytical Determination Of A Helicopter Height Velocity Diagram, Michael J. Harris Mar 2018

Analytical Determination Of A Helicopter Height Velocity Diagram, Michael J. Harris

Theses and Dissertations

A helicopter height velocity (HV) diagram was analytically constructed using optimal control techniques. A three degree of freedom, point-mass, dynamic model was developed and validated with flight test data. An induced velocity calculation was incorporated which addressed the effects of vortex ring state. The problem was posed as an open final time, constrained initial state, constrained final state problem, with the objective function as a weighted sum of the initial altitude and quadratic controls. This formulation was solved using direct pseudo-spectral collocation and adaptive mesh refinement as implemented by the GPOPS-II® software suite. Proper adjustment of path constraints was crucial …

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Influence Of Coolant Flow Rate Parameters In Scaling Gas Turbine Cooling Effectiveness On A Flat Plate, Jacob P. Fischer Mar 2018

Influence Of Coolant Flow Rate Parameters In Scaling Gas Turbine Cooling Effectiveness On A Flat Plate, Jacob P. Fischer

Theses and Dissertations

Effective film cooling relies on the performance of the selected cooling hole shape and placement of the holes on the surface of the blade. To test each holes effectiveness, large scale, low-temperature testing has been used to reduce cost and complexity. The resulting quantity from this testing is called the adiabatic effectiveness (n). The adiabatic effectiveness can then scaled up to engine operating conditions to predict how the selected film cooling hole will perform. This process is complicated by the nonlinear variation of gas properties between coolant and freestream conditions as well as between the experimental and engine conditions. In …

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An Efficient Euler Method To Predict Shock Migration On A Straked Delta Wing Design, Dylan N. Hope Mar 2018

An Efficient Euler Method To Predict Shock Migration On A Straked Delta Wing Design, Dylan N. Hope

Theses and Dissertations

In support of the Air Force Office of Scientific Research, this project sought to identify the significance of nonlinear aerodynamic phenomena in regards to LCO of a straked delta wing design. Previous works include unsteady Navier-Stokes aeroelastic analysis of various wing designs and flight test of F-16 transonic LCO with interest focused on oscillatory SITES behavior. The research presented within this investigation further expanded the understanding of unsteady aerodynamics by performing aeroelastic analysis of a wing oscillated in pitch with an Euler-based, boundary layer coupled numerical method (ZEUS). The wing was tested for a multitude of LCO parameters such as …

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Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1000°C In Air And In Silicic Acid-Saturated Steam, Brian G. Kroeger Mar 2018

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1000°C In Air And In Silicic Acid-Saturated Steam, Brian G. Kroeger

Theses and Dissertations

Advanced SiC/SiC ceramic matrix composites (CMCs) are being considered for a variety of applications. Of interest is their ability to withstand exposure to high temperature in an aggressive oxidizing environment. The presence of steam creates such an environment. As steam traverses across a SiC/SiC composite and through cracks in the SiC matrix, it becomes saturated with silicic acid, Si(OH)4. It is essential to understand the long-term impacts and durability of SiC/SiC CMCs that have been exposed to such a demanding environment. The present research investigated creep of Hi-Nicalon™ S SiC fibers at 1000°C in air and in silicic …

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The Study And Application Of Carbon Nanotube Film Heaters For Space Applications, Christopher C. Rocker Mar 2018

The Study And Application Of Carbon Nanotube Film Heaters For Space Applications, Christopher C. Rocker

Theses and Dissertations

The purpose of this research was to examine the feasibility of using Carbon Nanotube (CNT) sheets as thin film heaters for space applications. The ability to maintain the temperature of space components has a direct impact on a space vehicle's operation and longevity. Currently etched foil heaters are used to heat satellite batteries. Battery heaters are the focus of this research. However, as this study will show, they have limitations and are susceptible to failure. CNT sheets have many beneficial properties and show potential in replacing the etched foil design. In this study test specimens were created by forming laminate …

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Comparison Of Traditional Versus Cubesat Remote Sensing: A Model-Based Systems Engineering Approach, Daniel L. Cipera Mar 2018

Comparison Of Traditional Versus Cubesat Remote Sensing: A Model-Based Systems Engineering Approach, Daniel L. Cipera

Theses and Dissertations

This thesis compares the ability of both traditional and CubeSat remote sensing architectures to fulfill a set of mission requirements for a remote sensing scenario. Mission requirements originating from a hurricane disaster response scenario are developed to derive a set of system requirements. Using a Model-based Systems Engineering approach, these system requirements are used to develop notional traditional and CubeSat architecture models. The technical performance of these architectures is analyzed using Systems Toolkit (STK); the results are compared against Measures of Effectiveness (MOEs) derived from the disaster response scenario. Additionally, systems engineering cost estimates are obtained for each satellite architecture …

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The Subject Librarian Newsletter, Engineering And Computer Science, Spring 2018, Buenaventura "Ven" Basco Mar 2018

The Subject Librarian Newsletter, Engineering And Computer Science, Spring 2018, Buenaventura "Ven" Basco

Libraries' Newsletters

No abstract provided.

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Nonlinear Control Of Underactuated And Constrained Systems, Derek Hoffman Mar 2018

Nonlinear Control Of Underactuated And Constrained Systems, Derek Hoffman

Doctoral Dissertations and Master's Theses

It is the purpose of this document to elaborate on the control of systems that are underactuated or otherwise constrained. To do so, local- and global-coordinate formulations are implemented to generate well-defined system dynamics for a multitude of scenarios. These dynamics are shown to lie on manifolds defined by mathematical restrictions, allowing for singularity-free modeling for global considerations. Feed-back controllers by extension share these benefits, facilitating singularity-free control algorithms as a result. Further, unactuated degrees of freedom can be treated as additional constraints, resulting in an embedded manifold upon the original dynamics. A transformation between a provided set of dynamical …

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Estimation Of 3d Orientation From Inertial Sensors With Different/Nonuniform Sampling, Soulaimane Berkane Mar 2018

Estimation Of 3d Orientation From Inertial Sensors With Different/Nonuniform Sampling, Soulaimane Berkane

Western Research Forum

No abstract provided.

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A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello Mar 2018

A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello

Theses and Dissertations

The research this paper focuses on is comparing the structural differences between the icosahedron and hexakis icosahedron frame and skin for use as a vacuum lighter than air vehicle (VLTAV), analyzing the stress concentrations in the hexakis icosahedron both with and without the skin, and finding the optimal location and size of the air evacuation method for creating the internal vacuum. Previous research to date has identified dynamic loading on the structure and optimization of the structure, but this will be the first research to analyze the manufacturing of the structure through the development of the air evacuation design. Findings …

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Developing Motion Platform Dynamics For Studying Biomechanical Responses During Exercise For Human Spaceflight Applications, Kaitlin Lostroscio Mar 2018

Developing Motion Platform Dynamics For Studying Biomechanical Responses During Exercise For Human Spaceflight Applications, Kaitlin Lostroscio

USF Tampa Graduate Theses and Dissertations

In future human spaceflight missions, with prolonged exposure to microgravity, resistive and aerobic exercises will be countermeasures for bone loss, muscle loss, and decreased aerobic capacity. Two of the exercises of interest are squats and rowing. The cyclic forces produced during these exercises are at relatively low frequencies which are likely to excite structural resonances of space vehicles. Vibration Isolation Systems (VIS) are being designed to be paired with future exploration exercise devices in order to prevent these cyclic exercise forces from impacting the space vehicle. The VIS may be configured such that a platform supports the human and exercise …

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Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack, Matthew J. Satchell, Jeffrey M. Layng, Robert B. Greendyke Mar 2018

Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack, Matthew J. Satchell, Jeffrey M. Layng, Robert B. Greendyke

Faculty Publications

The effect of thermal and chemical boundary conditions on the structure and chemical composition of the wake behind a 3D Mach 7 sphere-cone at an angle of attack of 5 degrees and an altitude of roughly 30,000 m is explored. A special emphasis is placed on determining the number density of chemical species which might lead to detection via the electromagnetic spectrum. The use of non-ablating cold-wall, adiabatic, and radiative equilibrium wall boundary conditions are used to simulate extremes in potential thermal protection system designs. Non-ablating, as well as an ablating boundary condition using the “steady-state ablation” assumption to compute …

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2018 Oklahoma Research Day Guide Book, Southwestern Oklahoma State University Mar 2018

2018 Oklahoma Research Day Guide Book, Southwestern Oklahoma State University

Oklahoma Research Day Abstracts

This is the 2018 Oklahoma Research Day Guide Book. This book does not contain abstracts.

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Classical Molecular Dynamics Study For Defect Sink Behavior In Oxide Dispersed Strengthened Alloys, M. Mustafa Azeem, Zhongyu Li, Qingyu Wang, Qazi Muhammad Nouman Amjad, Muhammad Zubair, O. M.H. Ahmed Mar 2018

Classical Molecular Dynamics Study For Defect Sink Behavior In Oxide Dispersed Strengthened Alloys, M. Mustafa Azeem, Zhongyu Li, Qingyu Wang, Qazi Muhammad Nouman Amjad, Muhammad Zubair, O. M.H. Ahmed

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Oxide Dispersed Strengthened (ODS) alloys are considered as a potential candidate for future generation reactors and can even be graded as better radiation resistant materials than the ones already in use. Molecular dynamics (MD) simulation study for defect sinks properties of ODS alloys have been investigated at 700K using LAMMPS (Atomic/Molecular massively parallel simulator software. SRIM (stopping range of ions in matter) code was used to see the approximate range of the ions and damage cascade profile. It has been observed that the oxide particle attracts vacancies/interstitials produced in the base matrix near the interface. The modeled structure looked amorphous …

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Study Of Abnormal Grain Growth In Beta Annealed Ti-6al-4v Forgings, Lee R. Morris Mar 2018

Study Of Abnormal Grain Growth In Beta Annealed Ti-6al-4v Forgings, Lee R. Morris

Theses and Dissertations

Beta annealed Ti-6Al-4V has been used extensively in current aerospace platforms due to properties such as high strength to weight ratio. Recent inspections during aircraft production have revealed regions of excessive grain sizes, resulting in quarantined parts and excessive time spent on root cause analysis and risk mitigation efforts. Uncertainty surrounding these parts has led to increased costs and may cause future aircraft production delays. Part manufacturers have intermittently reported problems with abnormal grain growth in these alloys for years, but to date no supplier has been able to determine the source of this microstructural phenomenon. Leveraging common Finite Element …

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Analysis Of Additively Manufactured Injectors For Rotating Detonation Engines, Michael C. Waters Mar 2018

Analysis Of Additively Manufactured Injectors For Rotating Detonation Engines, Michael C. Waters

Theses and Dissertations

This research represents an experimental and computational analysis of additively manufactured injectors for Rotating Detonation Engines (RDEs) for use in rocket propulsion. This research was based on the manufacture and testing of existing injector element designs using additive techniques. The designs were modeled from geometries gathered from Sutton and Biblarz Elements of Rocket Propulsion [23]. The goal of this research was to characterize the viscous losses of each design based on the discharge coefficient. The designs were computationally simulated to gain insight to the flow characteristics using multiple sets of conditions for surface roughness and inlet pressure. The results were …

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Numerical Study Of Lateral Migration Of Elliptical Magnetic Microparticles In Microchannels In Uniform Magnetic Fields, Jie Zhang, Cheng Wang Mar 2018

Numerical Study Of Lateral Migration Of Elliptical Magnetic Microparticles In Microchannels In Uniform Magnetic Fields, Jie Zhang, Cheng Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This work reports numerical investigation of lateral migration of a paramagnetic microparticle of an elliptic shape in a plane Poiseuille flow of a Newtonian fluid under a uniform magnetic field by direct numerical simulation (DNS). A finite element method (FEM) based on the arbitrary Lagrangian–Eulerian (ALE) approach is used to study the effects of strength and direction of the magnetic field, particle–wall separation distance and particle shape on the lateral migration. The particle is shown to exhibit negligible lateral migration in the absence of a magnetic field. When the magnetic field is applied, the particle migrates laterally. The migration direction …

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Les Taux De Rupture De Conduites D’Eau Aux États-Unis Et Au Canada : Une Étude Complète, Steven Folkman Mar 2018

Les Taux De Rupture De Conduites D’Eau Aux États-Unis Et Au Canada : Une Étude Complète, Steven Folkman

Mechanical and Aerospace Engineering Faculty Publications

La prospérité économique des villes modernes est basée sur un réseau d’infrastructures complexe à la fois en surface et sous la terre. Un élément essentiel pour la santé publique et le bien-être économique est notre eau potable, qui est acheminée jusqu’à notre robinet à travers un réseau complexe de conduites de distribution d’eau souterraines. Étant donné que la plus grande partie de cette infrastructure se trouve sous terre, elle est hors de vue et souvent négligée. Disposer de données empiriques sur des ruptures de conduites d’eau aide les services publics avec leurs processus de prises de décision quant aux réparations …

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Effects Of Position Uncertainty On Passive Multistatic Sar Resolution Measures, Duy K. Nguyen Mar 2018

Effects Of Position Uncertainty On Passive Multistatic Sar Resolution Measures, Duy K. Nguyen

Theses and Dissertations

Given numerous exciting potentials including substantial cost savings, passive multistatic synthetic aperture radar (PMSAR) has been gaining more attention in the radar community. However, PMSAR research efforts such as emitters of opportunity selection thus far have not considered radar position uncertainty. Seeking to fill this knowledge gap, we run Monte Carlo trials to simulate transmitter position uncertainty and examine the effects on the multistatic resolution of radar sets of different geometries, center frequencies and bandwidths. By monitoring the 3dB contour of the multistatic point spread function, we find that the multistatic resolution worsens on average and the data spread grows …

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Ultra-Broadband Infrared Absorption By Tapered Hyperbolic Multilayer Waveguides, Huixu Deng, Cherian J. Mathai, Shubhra Gangopadhyay, Jie Gao, Xiaodong Yang Mar 2018

Ultra-Broadband Infrared Absorption By Tapered Hyperbolic Multilayer Waveguides, Huixu Deng, Cherian J. Mathai, Shubhra Gangopadhyay, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ultra-broadband strong absorption over 92% covering the infrared wavelength range of 1 ~ 6μm is demonstrated by using the tapered hyperbolic Au-SiO2 multilayer waveguides on glass substrates. Such broadband absorption is formed by the stop-light modes at various wavelengths located at different waveguide widths. A planar hyperbolic waveguide model is built to determine the stop-light modes by considering both forward and backward guided modes. The stop-light modes located inside the Au-SiO2 multilayer waveguide are simulated at the absorption peaks by reducing the Au loss. Tapered multilayer waveguides with varying top widths are further simulated, fabricated and measured, indicating …

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Wavelength-Selective Mid-Infrared Metamaterial Absorbers With Multiple Tungsten Cross Resonators, Zhigang Li, Liliana Stan, David A. Czaplewski, Xiaodong Yang, Jie Gao Mar 2018

Wavelength-Selective Mid-Infrared Metamaterial Absorbers With Multiple Tungsten Cross Resonators, Zhigang Li, Liliana Stan, David A. Czaplewski, Xiaodong Yang, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Wavelength-selective metamaterial absorbers in the mid-infrared range are demonstrated by using multiple tungsten cross resonators. By adjusting the geometrical parameters of cross resonators in single-sized unit cells, near-perfect absorption with single absorption peak tunable from 3.5 µm to 5.5 µm is realized. The combination of two, three, or four cross resonators of different sizes in one unit cell enables broadband near-perfect absorption at mid-infrared range. The obtained absorption spectra exhibit omnidirectionality and weak dependence on incident polarization. The underlying mechanism of near-perfect absorption with cross resonators is further explained by the optical mode analysis, dispersion relation and equivalent RLC circuit …

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Computational Investigation Using Bleed As A Method Of Shock Stabilization, Dayle L. Chang Mar 2018

Computational Investigation Using Bleed As A Method Of Shock Stabilization, Dayle L. Chang

Theses and Dissertations

Shock-wave/boundary layer interactions (SWBLI) produce undesirable dynamic loads and separated unsteady flows, adversely impacting the performance and structural integrity of supersonic vehicles. Computational fluid dynamics (CFD) is a successful tool in experimental planning and shows promise as a critical tool in understanding and mitigating negative effects of SWBLI. The goal of this research is to demonstrate the effect of bleed holes on shock stability using the OVERFLOW CFD solver to inform the planning of an Air Force Research Laboratory (AFRL) SWBLI wind tunnel experiment. First, a two-dimensional, flat plate, single-hole configuration was developed. Massflow discrepancies of 14.8% were initially observed …

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Space-Based Maneuver Detection And Characterization Using Multiple Model Adaptive Estimation, Justin D. Katzovitz Mar 2018

Space-Based Maneuver Detection And Characterization Using Multiple Model Adaptive Estimation, Justin D. Katzovitz

Theses and Dissertations

An increasingly congested space environment requires real-time and dynamic space situational awareness (SSA) on both domestic and foreign space objects in Earth orbits. Current statistical orbit determination (SOD) techniques are able to estimate and track trajectories for cooperative spacecraft. However, a non-cooperative spacecraft performing unknown maneuvers at unknown times can lead to unexpected changes in the underlying dynamics of classical filtering techniques. Adaptive estimation techniques can be utilized to build a bank of recursive estimators with different hypotheses on a system's dynamics. The current study assesses the use of a multiple model adaptive estimation (MMAE) technique for detecting and characterizing …

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Quasi-Static Nonlinear Analysis Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Kyle D. Moore Mar 2018

Quasi-Static Nonlinear Analysis Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Kyle D. Moore

Theses and Dissertations

Due to the many drawbacks associated with a traditional lighter than air vehicle (LTAV), there is a desire for a LTAV which generates lift from an internal vacuum. To date, two feasible designs (the icosahedron and the hexakis icosahedron) for this so called vacuum lighter than air vehicle (VLTAV) have been studied at the Air Force Institute of Technology (AFIT). This research looks to show the feasibility of a new design for a VLTAV, the celestial icosahedron. This research includes a boundary condition study which proves the symmetric nature of the celestial icosahedron's frame with laterally constrained and unconstrained vertices. …

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