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Air Force Institute of Technology

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Articles 871 - 900 of 1674

Full-Text Articles in Aerospace Engineering

Vibration Analysis Of Commercial Thermal Barrier Coatings, Lindell E. Pearson Jun 2008

Vibration Analysis Of Commercial Thermal Barrier Coatings, Lindell E. Pearson

Theses and Dissertations

Thermal barrier coatings (TBCs) are currently used in turbine engine components to protect substrate material from being exposed to high temperatures and corrosion. These coatings also have the potential to reduce stress in critical engine parts which could increase the life cycle of these parts. The fact that these coatings are already qualified for use in turbine engines makes it worth investigating their damping properties. The problem with TBCs is that they are difficult to characterize as they display nonlinear properties. This research utilizes an experimental and finite element procedure to characterize these coatings. A scanning electron microscope (SEM) was …

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Evaluation Of Nanocomposites As Lightweight Electronic Enclosures For Satellites' Applications, Benjamin T. Harder Jun 2008

Evaluation Of Nanocomposites As Lightweight Electronic Enclosures For Satellites' Applications, Benjamin T. Harder

Theses and Dissertations

The United States military is exploring the use of nanocomposite materials for satellite structural applications. Current composite spacecraft structures are nonconductive and must have expensive shielding materials applied in order to protect the spacecraft from catastrophic damage that can be caused by electromagnetic interference (EMI) and/or electrostatic discharge (ESD) which are characteristics of the space environment. Conductive nanocomposites are being developed for spacecraft structures that will provide ESD and EMI shielding protection without the need for expensive secondary shielding materials. This thesis studied one such material consisting of M55J/RS-3 composite combined with nickel nanostrands™. Four different configurations were tested for …

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Operationally Responsive Space (Ors): An Architecture And Enterprise Model For Adaptive Integration, Test And Logistics, Jeff A. Alexander, Martha Charles-Vickers, Talbot L. Smith, Michael L. Vickers Jun 2008

Operationally Responsive Space (Ors): An Architecture And Enterprise Model For Adaptive Integration, Test And Logistics, Jeff A. Alexander, Martha Charles-Vickers, Talbot L. Smith, Michael L. Vickers

Theses and Dissertations

The capability to rapidly deploy tactical satellites to meet a Joint Force Commander's immediate battlespace requirements is a well-documented joint capability need. Key U.S. strategic documentation cites the need for the capability to maintain persistent surveillance or an "unblinking eye" over battlespace and to rapidly reconstitute critical space capabilities to preserve situational awareness. The warfighter requires a tactical space-based deployment capability which employs a request to launch and operational deployment window of 90 to 120 days. This master's thesis executed two (2) major areas of work: apply, and reinforce the Operationally Responsive Space (ORS) mission tasks using the Joint Capabilities …

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Tightly Integrating Optical And Inertial Sensors For Navigation Using The Ukf, Sedat Ebcin Mar 2008

Tightly Integrating Optical And Inertial Sensors For Navigation Using The Ukf, Sedat Ebcin

Theses and Dissertations

The motivation of this research is to address the benefits of tightly integrating optical and inertial sensors where GNSS signals are not available. The research begins with describing the navigation problem. Then, error and measurement models are presented. Given a set of features, a feature detection and projection algorithm is developed which utilizes inertial measurements to predict vectors in the feature space between images. The unscented Kalman filter is applied to the navigation system using the inertial measurements and feature matches to estimate the navigation trajectory. Finally, the image-aided navigation algorithm is tested using a simulation and an experiment. As …

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The Concept Design Of A Split Flow Liquid Hydrogen Turbopump, Michael A. Arguello Mar 2008

The Concept Design Of A Split Flow Liquid Hydrogen Turbopump, Michael A. Arguello

Theses and Dissertations

An initial design of a split flow liquid hydrogen turbopump for the Dual Expander Aerospike Nozzle (DEAN) upper stage engine was completed. The engine nozzle is an annular aerospike. The engine cycle requires a combustion chamber pressure of 1,740 psia. The DEAN is designed to deliver 57,200 lbf of thrust and 472 seconds of Isp. The turbopump design was completed using a meanline software tool. The design consists of a single piece rotor, with a two-stage pump and radial inflow turbine. The turbopump flow rates are 15.1 and 7.55 lbm/s into the first and second stage, respectively. The first and …

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Analysis Of Multi-Layered Materials Under High Velocity Impact Using Cth, Jason K. Lee Mar 2008

Analysis Of Multi-Layered Materials Under High Velocity Impact Using Cth, Jason K. Lee

Theses and Dissertations

Multi-layer armor containing ceramic and metallic layers has become more common in the past two decades. Typically, ceramics have high compressive strength which combined with their low density make them highly desirable for armor applications. This research effort numerically simulates high velocity impact of cylindrical projectiles on multi-layer metallic and ceramic targets of finite thickness. The impact of the projectile occurs normal to the surface of the target. The projectiles used are made of either S7 tool steel or tungsten. The targets consist of either rolled homogeneous armor, 4340 steel and boron carbide ceramic or rolled homogeneous armor and boron …

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Computational Design Of Upperstage Chamber, Aerospike, & Cooling Jacket For Dual-Expander Rocket Engine, David F. Martin Ii Mar 2008

Computational Design Of Upperstage Chamber, Aerospike, & Cooling Jacket For Dual-Expander Rocket Engine, David F. Martin Ii

Theses and Dissertations

To increase the performance of the current US satellite launch capability, new rocket designs must be undertaken. One concept that has been around since the 50s but yet to be utilized on a launch platform is the aerospike, or plug nozzle. The aerospike nozzle concept demonstrates globally better performance compared to a conventional bell nozzle, since the expansion of the jet is not bounded by a wall and therefore can adjust to the environment by changing the outer jet boundary. A dual-expander aerospike nozzle (DEAN) rocket concept would exceed the Integrated High Payoff Rocket Propulsion Technology initiative (IHPRPT) phase three …

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On-Board Thermal Management Of Waste Heat From A High-Energy Device, Nathan D. Klatt Mar 2008

On-Board Thermal Management Of Waste Heat From A High-Energy Device, Nathan D. Klatt

Theses and Dissertations

The use of on-board high-energy devices such as megawatt lasers and microwave emitters requires aircraft system integration of thermal devices to either rid waste heat or utilize it in other areas of the aircraft. Non-chemical lasers are among the most challenging applications due to the low cooling temperature requirements (67 °F) and high waste heat generation times of order 20 s. (Microwave devices will be cooled at 157.7 °F.) One plan calls for the rapidly generated waste energy to be stored prior to peripheral utilization, with subsequent removal of the heat over a 5-10 minute span. A method is presented …

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Optimal Guidance Of A Relay Mav For Isr Support Beyond Line-Of-Sight, John H. Hansen Mar 2008

Optimal Guidance Of A Relay Mav For Isr Support Beyond Line-Of-Sight, John H. Hansen

Theses and Dissertations

This thesis developed guidance laws to optimally position a relay Micro-UAV (MAV) to provide an operator with real-time Intelligence, Surveillance, and Reconnaissance (ISR) by relaying communication and video signals when there is no line-of-sight between the operator at the base and the rover MAV performing the ISR mission. The ISR system consists of two MAVs, the Relay and the Rover, and a Base. The Relay strives to position itself to minimize the radio frequency (RF) power required for maintaining communications between the Rover and the Base, while the Rover performs the ISR mission, which may maximize the required RF power. …

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Finite Element Simulation Methods For Dry Sliding Wear, Aaron J. Chmiel Mar 2008

Finite Element Simulation Methods For Dry Sliding Wear, Aaron J. Chmiel

Theses and Dissertations

The Holloman High Speed Test Track is a rocket sled track for testing at hypersonic velocities. However, there are customers that desire to test at even greater velocities. In order to achieve higher velocities there are several phenomena that must be overcome. One important phenomenon is wear of the shoe that holds the sled on the rail. This research is a look at the feasibility of using finite element analysis to predict the wear of the shoe during a test run down the track. Two methods are investigated, one is a macro-scale, incremental method utilizing traditional wear equations from Archard, …

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Filtered Rayleigh Scattering Measurements In A Buoyant Flow Field, Steven M. Meents Mar 2008

Filtered Rayleigh Scattering Measurements In A Buoyant Flow Field, Steven M. Meents

Theses and Dissertations

Filtered Rayleigh Scattering (FRS) is a non-intrusive, laser-based flow characterization technique that consists of a narrow linewidth laser, a molecular absorption filter, and a high resolution camera behind the filter to record images. Gases of different species have different molecular scattering cross-sections that become apparent as they pass through the interrogating laser light source, and this difference is used to discriminate between the different gaseous components. This study focuses on the behavior of a buoyant helium jet exiting horizontally into ambient air, and more specifically this jet’s tendency to form side lobes that are discharged from the core fluid under …

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A Static Aeroelastic Analysis Of A Flexible Wing Mini Unmanned Aerial Vehicle, Nathan A. Pitcher Mar 2008

A Static Aeroelastic Analysis Of A Flexible Wing Mini Unmanned Aerial Vehicle, Nathan A. Pitcher

Theses and Dissertations

The static aeroelastic behavior of the Nighthawk mini unmanned aerial vehicle is examined using a combined experimental and computational approach. Three wings are examined. In order of increasing stiffness they are: a flexible wing, a stiff wing, and a fictitious rigid wing with zero deflection. Photogrammetry is used during wind tunnel testing to measure the average deflected shape of the flexible and stiff wings during flight. The independent variables during wind tunnel tests are angle of attack (ranging from −5.1° through 13.4°) and velocity, which is 20 mph, 30 mph, and 40 mph. Roll angle and yaw angle are control …

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Biomimetic Micro Air Vehicle Testing Development And Small Scale Flapping-Wing Analysis, Craig E. Svanberg Mar 2008

Biomimetic Micro Air Vehicle Testing Development And Small Scale Flapping-Wing Analysis, Craig E. Svanberg

Theses and Dissertations

The purpose of this research was to develop testing methods capable of analyzing the performance of a miniature flapping-wing mechanism that can later be adapted to a biomimetic micro air vehicle (MAV). Three small scale flapping mechanisms capable of single plane flapping, flapping with active pitch control, and flapping/pitch with out-of-plane movement were designed using SolidWorks. The flapping-only model was fabricated on an Objet Eden 500V 3-dimensional printer. The flapping mechanism was mounted on an aluminum plate supported by air bearings, and thrust was measured for a variety of conditions. The testing was conducted using wings composed of carbon fiber …

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Analyzing Carbohydrate-Based Regenerative Fuel Cells As A Power Source For Unmanned Aerial Vehicles, Olek Wojnar Mar 2008

Analyzing Carbohydrate-Based Regenerative Fuel Cells As A Power Source For Unmanned Aerial Vehicles, Olek Wojnar

Theses and Dissertations

Based on current capabilities, we examine the feasibility of creating a carbohydrate-based regenerative fuel cell (CRFC) as the primary power source for unmanned aerial vehicles (UAV) for long endurance missions where station keeping is required. A CRFC power system is based on a closed-loop construct where carbohydrates are generated from zooxanthellae, algae that create excess carbohydrates during photosynthesis. The carbohydrates are then fed to a carbohydrate fuel cell where electric power is generated for the UAV’s propulsion, flight control, payload, and accessory systems. The waste products from the fuel cell are used by the zooxanthellae to create more carbohydrates, therefore …

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Minimizing Secular J2 Perturbation Effects On Satellite Formations, Jonathan W. Wright Mar 2008

Minimizing Secular J2 Perturbation Effects On Satellite Formations, Jonathan W. Wright

Theses and Dissertations

The purpose of this thesis is to examine the secular effects of the J2 oblateness perturbation on close proximity satellites. The main objective is to analyze the deputy’s position and velocity with respect to the chief and adjust the initial conditions of the deputy in an attempt to minimize the secular effects of J2 perturbations. Previous work has provided a method of obtaining a closed form solution for J2 invariance with co-planar orbits. Therefore, this work will primarily consider deputy orbits that experience motion outside of the chief’s orbital plane. Upon determining the required initial conditions, the …

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Modeling Gps Satellite Orbits Using Kam Tori, Rachel M. Derbis Mar 2008

Modeling Gps Satellite Orbits Using Kam Tori, Rachel M. Derbis

Theses and Dissertations

Global Positioning System (GPS) satellite orbits are modeled using Kolmogorov, Arnold, Moser (KAM) tori. Precise Global Positioning System satellite locations are analyzed using Fourier transforms to identify the three basis frequencies in an Earth Centered, Earth Fixed (ECEF) rotating reference frame. The three fundamental frequencies are 1) the anomalistic frequency, 2) a combination of earth’s rotational frequency and the nodal regression rate, and 3) the apsidial regression rate. A KAM tori model fit to the satellite data could be used to predict future satellite locations. This model would allow rapid determination with fewer computational requirements than the typical method of …

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Thermal Characterization Of A Hall Effect Thruster, Alex M. Bohnert Mar 2008

Thermal Characterization Of A Hall Effect Thruster, Alex M. Bohnert

Theses and Dissertations

The thermal characteristics of a Hall thruster directly influence thruster and spacecraft design. High temperatures affect the magnetic coil capabilities and cause higher insulator erosion rates, influencing both thruster performance and lifetime. The Hall thruster transfers heat through both radiation and conduction, and the spacecraft must handle this additional thermal energy. An infrared camera provides a non-intrusive method to analyze the thermal characteristics of an operational Hall thruster. This thesis contains the thermal analysis of a Busek Co. Inc. 200 W Hall thruster, using a FLIR ThermaCAM SC640 infrared camera. The Space Propulsion Analysis and System Simulator Laboratory at the …

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Crew Exploration Vehicle (Cev) Skip Entry Trajectory, Emre Kaya Mar 2008

Crew Exploration Vehicle (Cev) Skip Entry Trajectory, Emre Kaya

Theses and Dissertations

This research effort develops a program using MATLAB® to solve the equations of motion for the atmospheric reentry of the Crew Exploration Vehicle (CEV) which is assumed to be in the phase of a lunar return trajectory that could be initiated any time during the mission. The essential reason for this research is to find a solution for the problem of an unplanned lunar return in addition to the normal procedures. Unlike Apollo type missions, the CEV would still be able to land on any preplanned available landing sites without any additional delay. In Apollo type missions, the return phase …

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Determination Of Static And Dynamic Stability Derivatives Using Beggar, Michael E. Bartowitz Mar 2008

Determination Of Static And Dynamic Stability Derivatives Using Beggar, Michael E. Bartowitz

Theses and Dissertations

The static and dynamic pitch and roll stability derivatives of a finned, axisymmetric missile known as the Basic Finner were examined using a Computational Fluid Dynamics (CFD) approach. Stability derivatives are used to characterize vehicle motion, and knowledge of them is critical to the design of stable uncontrolled vehicles and control systems for controlled vehicles. Using CFD to characterize the motion of new munition designs has the potential to improve overall performance and reduce research and testing costs. The present analysis simulated forced oscillation and free oscillation of the Basic Finner model using the Air Force SEEK EAGLE Office's Beggar …

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A Comparison Of Moiré Interferometry And Digital Image Correlation, Ryan J. Davidson Mar 2008

A Comparison Of Moiré Interferometry And Digital Image Correlation, Ryan J. Davidson

Theses and Dissertations

This research effort studied the effect of subset size and step size on the spatial resolution and accuracy of Digital Image Correlation (DIC). In addition, DIC was compared with moiré interferometry in an attempt to give future researchers guidance on which method would be appropriate for their research. Strains fields were calculated from displacement fields measured by each method. The strain fields were then compared. The main findings of the research were that: increased subset sizes caused a smoothing of data; increased step sizes reduced the resolution of the data; DIC is an accurate displacement measurement technique; the spatial resolution …

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Effects Of Environment On Creep Behavior Of Nextel 720/Alumina-Mullite Ceramic Composite At 1200°C, Christopher L. Genelin Mar 2008

Effects Of Environment On Creep Behavior Of Nextel 720/Alumina-Mullite Ceramic Composite At 1200°C, Christopher L. Genelin

Theses and Dissertations

The creep behavior of an oxide-oxide ceramic matrix composite (CMC) was investigated at 1200°C in laboratory air, in steam and in argon. The composite consisted of a porous alumina-mullite matrix reinforced with laminated, woven mullite/alumina (Nextel/720) fibers. The composite had no fiber coating and relied on its porous alumina/mullite matrix for flaw tolerance. Tensile stress-strain behavior was investigated and the tensile properties were measured at 1200°C in laboratory air. Tensile creep behavior of the CMC was examined for creep stress levels of 73, 91, 114 and 136 MPa. Creep run-out, set to 100 h, was achieved for stress levels ≤ …

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Characterization And Control Of Carbon Dioxide Seed Particle Image Velocimetry, Bartt G. Greene Mar 2008

Characterization And Control Of Carbon Dioxide Seed Particle Image Velocimetry, Bartt G. Greene

Theses and Dissertations

Particle Image Velocimetry (PIV) data was acquired in two separate supersonic wind tunnels with carbon dioxide (CO2) particles utilized as the seed material. Previous work in clean seeding showed CO2 could be used as seed material to produce velocity maps. This research provides the first quantitative assessment of particle response, particle size control via purge gas, and scalability using CO2 particles. A variety of feed tube and shroud configurations, in combination with varying volumetric flow rates of purge air were measured using a laser diffraction device. The CO2 particles were injected into the stilling chamber …

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Demonstrative Maneuvers For Aircraft Agility Predictions, David M. Hall Mar 2008

Demonstrative Maneuvers For Aircraft Agility Predictions, David M. Hall

Theses and Dissertations

This study was motivated by a need to develop a reliable method of predicting the agility characteristics of various aircraft. To fully investigate the agility of an aircraft, maneuvers which push the limits of an aircraft’s maneuvering capabilities must be simulated. In these cases, classic trajectory optimization techniques either require too many assumptions for a realistic solution or require a good guess of the final solution before the problem is even attempted. This study investigated both the utility of pseudospectral optimization methods for robust trajectory optimization as well as the potential for demonstrating differences in aircraft agility characteristics of several …

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Direct Initiation Through Detonation Branching In A Pulsed Detonation Engine, Alexander R. Hausman Mar 2008

Direct Initiation Through Detonation Branching In A Pulsed Detonation Engine, Alexander R. Hausman

Theses and Dissertations

Pulsed Detonation Engines are currently limited in operating frequency to the order of 40 Hz due to lengthy ignition and deflagration to detonation transition (DDT) times. An experimental study is conducted to determine the requirements necessary to eliminate these constraints through the concept of direct initiation. A branched detonation crossover setup is constructed and the operational requirements are determined. This research demonstrates the ability to directly initiate a detonation in a vacant tube from a detonation obtained through detonation branching. Using a hydrogen-air mixture, a tail-to-head detonation branching is achieved in which a detonation is seen to propagate from a …

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Uncorrelated Track Avoidance, Darrell L. Grob Mar 2008

Uncorrelated Track Avoidance, Darrell L. Grob

Theses and Dissertations

The purpose of this thesis is to examine what data requirements are necessary to avoid continual series of uncorrelated tracks when gathering observations. The constants of the motion for simple two-body motion for a satellite orbiting the Earth, known as the classical orbital elements or COEs, do not remain constant due to zonal and sectoral harmonic variations in the Earth’s gravitational field. There are other elements of the motion that should be considered and this paper discusses the constancy of three elements: the Hamiltonian (H) of the Earth-Centered Rotating System, Ẑ-component of inertial angular momentum (Hk), …

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Initial Determination Of Low Earth Orbits Using Commercial Telescopes, Matthew M. Schmunk Mar 2008

Initial Determination Of Low Earth Orbits Using Commercial Telescopes, Matthew M. Schmunk

Theses and Dissertations

Within the last decade, many new technologies have significantly changed the face of private astronomy. Developments such as inexpensive but high-quality sensors, rapid personal computing, and easy networking inspire a reexamination of an old problem: how practical is it to develop initial orbit estimates for Low Earth Orbiting (LEO) satellites using optical tracking? This paper documents the design and implementation of a commercial telescope system used to answer precisely that question. This analysis deter- mined there are some challenging barriers to successful single-site orbit determination, but it is possible given the right conditions. Considering the low cost and small sup- …

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Determining The Capability Requirements For A Space Based Optical Sensor To Determine The Trajectory Of An Incoming Antisatellite Weapon, Mesut Gulmus Mar 2008

Determining The Capability Requirements For A Space Based Optical Sensor To Determine The Trajectory Of An Incoming Antisatellite Weapon, Mesut Gulmus

Theses and Dissertations

The goal of this research is to build up a logic to catch and track incoming ASAT weapons by using space-based onboard optical sensors. The satellite orbit and ASAT trajectory of the Chinese test were generated to relate the research to the real world application. These position and velocity values are used to generate simulated observation data for a hypothetical sensor on the targeted satellite. These observation values are assumed to be true, and some representative amounts of error was added to these data. Only two body dynamics are considered; drag effect and other perturbations are neglected. The modern orbit …

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Piv-Based Examination Of Deep Stall On An Oscillating Air Foil, Daniel E. Fredberg Mar 2008

Piv-Based Examination Of Deep Stall On An Oscillating Air Foil, Daniel E. Fredberg

Theses and Dissertations

A number of studies suggest that the deep stall flow fields produced by a pure-pitch and a pure-plunge oscillating airfoil are equivalent, when effective angles of attack are matched. This assumption is examined using particle image velocimetry (PIV). Sinusoidal oscillations of a pure-plunge and pure-pitch airfoil with matched reduced frequency k = 3.93 and with kinematically equivalent amplitudes of effective angle of attack are comparatively examined using results of PIV in a free surface water tunnel at AFRL/RB, Wright Patterson AFB. Experiments were conducted at Re = 10,000 and Re = 40,000, based on free stream velocity and airfoil chord, …

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Contamination Study Of Micro Pulsed Plasma Thrusters, Ceylan Kesenek Mar 2008

Contamination Study Of Micro Pulsed Plasma Thrusters, Ceylan Kesenek

Theses and Dissertations

Satellite designing trend is progressing towards building smaller satellites. Small satellites require micro propulsion devices for accurate control by the propulsion system. Micro-Pulsed Plasma Thrusters (μPPTs) are highly reliable and simple micro propulsion systems that will offer attitude control, station keeping, constellation flying, and drag compensation for such satellites. As an unfortunate side effect, the plume induces contamination on spacecraft surfaces and may lead to significant problems with sensors and power generation. Solid particulates in the exhaust plume may deposit on spacecraft instrument and the solar array surfaces limiting or reducing the mission capability as well as the lifetime of …

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Extending Cfd Modeling To Near-Continuum Flows Using Enhanced Thermophysical Modeling, Abram E. Claycomb Mar 2008

Extending Cfd Modeling To Near-Continuum Flows Using Enhanced Thermophysical Modeling, Abram E. Claycomb

Theses and Dissertations

The constitutive relations found in traditional Navier-Stokes-based computational fluid dynamics solvers are known to be limited in altitude. The presence of nonequilibrium phenomena beyond what these methods are able to predict becomes more prevalent at higher altitudes, or increasing Knudsen number. The bulk viscosity, normally assumed to be zero in most computational fluid dynamics applications, is examined as a means of increasing the range of applicability of computational fluid dynamics. The bulk viscosity model used was from recent calculations available in the literature, from a new anisotropic potential energy surface, and is restricted to temperatures below 2000 K. The normal …

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