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Articles 1 - 30 of 50
Full-Text Articles in Engineering
Radar Based Navigation In Unknown Terrain, Kyle J. Kauffman
Radar Based Navigation In Unknown Terrain, Kyle J. Kauffman
Theses and Dissertations
There is a great need to develop non-GPS based methods for positioning and navigation in situations where GPS is not available. This research focuses on the development of an Ultra-Wideband Orthogonal Frequency Division Multiplexed (UWB-OFDM) radar as a navigation sensor in GPS-denied environments. A side-looking vehicle-fixed UWB-OFDM radar is mounted to a ground or aerial vehicle continuously collecting data. A set of signal processing algorithms and methods are developed which use the raw radar data to aide in calculating the vehicle position and velocity via a simultaneous localization and mapping (SLAM) approach. The radar processing algorithms detect strong, persistent, and …
The Effects Of Observations And Maneuvers On Orbit Solutions, Christine M. Schudrowitz
The Effects Of Observations And Maneuvers On Orbit Solutions, Christine M. Schudrowitz
Theses and Dissertations
The purpose of this research is to characterize the performance of the optimal sequential filter used in ODTK with a maneuvering satellite. Specifically, this thesis sought to characterize the performance using two scenarios: performance with a maneuver in between passes and performance with a limited number of measurements. The performance of the filter is evaluated by analyzing the covariance values generated during the orbit estimation process. Larger covariance values signify reduced performance of the filter. Several variables for the maneuvering satellite are used, including the maneuver direction and the maneuver magnitude. The time of the maneuver is also varied, which …
Predicting The Wear Of High Speed Rocket Sleds, Lauren B. Wuertemberger
Predicting The Wear Of High Speed Rocket Sleds, Lauren B. Wuertemberger
Theses and Dissertations
Holloman Air Force Base houses the 10 mile long Holloman High Speed Test Track (HHSTT) in New Mexico and can run hypersonic experiments at speeds up to 10,000m/s. Tested objects are loaded onto sleds, which are connected to the track by slippers that slide along the rails. The payload sled is propelled down the track by a series of rocket sleds. The ability to predict the wear that will occur on the slippers during these experiments is important for slipper design and preventing catastrophic failure. However, high speeds complicate wear prediction as there additional contributing factors, including inconsistent surface contact, …
Effect Of Accessory Power Take-Off Variation On A Turbofan Engine Performance, Anis Faidi
Effect Of Accessory Power Take-Off Variation On A Turbofan Engine Performance, Anis Faidi
Theses and Dissertations
Engine fuel efficiency of aerospace vehicles can be reached by different techniques. One way to do that is to reduce aircraft subsystems power supply effects on the engine performance. Previous research work has showed that extracting bleed air from the high pressure compressor exit is more efficient than extracting the equivalent amount of energy from the low pressure spool shaft. A high bypass turbofan engine was modeled using the Numerical Propulsion System Simulation (NPSS). The baseline engine performance was evaluated at different flight conditions of Mach number and altitude. To better understand the effect of air bleed take-off and shaft …
Scaling Study Of Wave Rotor Turbo-Normalization Of A Small Internal Combustion Engine, Brandon D. Smith
Scaling Study Of Wave Rotor Turbo-Normalization Of A Small Internal Combustion Engine, Brandon D. Smith
Theses and Dissertations
One issue facing small Remotely Piloted Aircraft engines is their ability to maintain performance at altitude. Since many of these aircraft use commercial off the shelf engines originally designed for radio controlled aircraft and lawn care implements, the reduced pressure environment significantly degrades the operability of the engine as the altitude increases. An option to overcome this difficulty is to supercharge the system; however most superchargers are designed for larger, typically automotive, engines. As a supercharger's size is decreased, there are large efficiency losses. Therefore, there is a need to accomplish this function on a smaller scale without. One option …
Investigation Into Suitability Of Geopolymers (Illite & Metakaolin) For The Space Environment, Brandon T. Cesul
Investigation Into Suitability Of Geopolymers (Illite & Metakaolin) For The Space Environment, Brandon T. Cesul
Theses and Dissertations
Suitability of non-organic polymers for space application is studied. Materials included are illite and metakaolin. Bulk material suitability was investigated for exposure to ultraviolet radiation, atomic oxygen, and high energy charged particles. Outgassing phenomenon of the materials was studied. Curing shrinkage reduction techniques were identified as well.
Operationally Responsive Spacecraft Using Electric Propulsion, Thomas C. Co
Operationally Responsive Spacecraft Using Electric Propulsion, Thomas C. Co
Theses and Dissertations
A desirable space asset is responsive and flexible to mission requirements, low-cost, and easy to acquire. Highly-efficient electric thrusters have been considered a viable technology to provide these characteristics; however, it has been plagued by limitations and challenges such that operational implementation has been severely limited. The technology is constantly improving, but even with current electric propulsion, a spacecraft is capable of maneuvering consistently and repeatedly in low-Earth orbit to provide a responsive and flexible system. This research develops the necessary algorithm and tools to demonstrate that EP systems can maneuver significantly in a timely fashion to overfly any target …
The Characterization Of Material Properties And Structural Dynamics Of The Manduca Sexta Forewing For Application To Flapping Wing Micro Air Vehicle Design, Ryan P. O'Hara
Theses and Dissertations
The Manduca Sexta species of moth serves as a source of biological inspiration for the future of micro air vehicle flapping flight. The ability of this species to hover in flapping flight has warranted investigation into the critical material, structural, and geometric properties of the forewing of this biological specimen. A rigorous morphological study of the Manduca Sexta forewing was conducted to characterize the physical and material properties of the biological forewing for the purpose of developing an advanced parametric three dimensional model finite element analysis (FEA) model. This FEA model was tuned to match the experimentally determined structural dynamics …
Novel Discretization Schemes For The Numerical Simulation Of Membrane Dynamics, Kyle F. Kolsti
Novel Discretization Schemes For The Numerical Simulation Of Membrane Dynamics, Kyle F. Kolsti
Theses and Dissertations
Motivated by the demands of simulating flapping wings of Micro Air Vehicles, novel numerical methods were developed and evaluated for the dynamic simulation of membranes. For linear membranes, a mixed-form time-continuous Galerkin method was employed using trilinear space-time elements, and the entire space-time domain was discretized and solved simultaneously. For geometrically nonlinear membranes, the model incorporated two new schemes that were independently developed and evaluated. Time marching was performed using quintic Hermite polynomials uniquely determined by end-point jerk constraints. The single-step, implicit scheme was significantly more accurate than the most common Newmark schemes. For a simple harmonic oscillator, the scheme …
Characteristics, Causes, And Evaluation Of Helicopter Particulate Obstruction, Michael P. Sullivan
Characteristics, Causes, And Evaluation Of Helicopter Particulate Obstruction, Michael P. Sullivan
Theses and Dissertations
A comprehensive approach to evaluation of rotorcraft brownout under degraded visual environmental conditions is presented. The results of a literature search covering the current state of brownout research are summarized. The brownout dust cloud generated by modern rotorcraft is analyzed and characterized using photographic and video data, coupled with examination of previous computer modeling techniques. A modeling analysis is performed in order to relate aircraft design and operating parameters to brownout dust cloud size is performed. The effect of vorticity in brownout dust cloud rollup is included. An augmented rating scale for pilot assessment is proposed for operational use, and …
Cfd Transient Simulation Of An Isolator Shock Train In A Scramjet Engine, Troy C. Hoeger
Cfd Transient Simulation Of An Isolator Shock Train In A Scramjet Engine, Troy C. Hoeger
Theses and Dissertations
For hypersonic flight, the scramjet engine uses an isolator to contain the pre-combustion shock train formed by the pressure difference between the inlet and the combustion chamber. If this shock train were to reach the inlet, it would cause an engine unstart, disrupting the flow through the engine and leading to a loss of thrust and potential loss of the vehicle. Prior to this work, a Computational Fluid Dynamics (CFD) simulation of the isolator was needed for simulating and characterizing the isolator flow and for finding the relationship between back pressure and changes in the location of the leading edge …
Freedrop Testing And Cfd Simulation Of Ice Models From A Cavity Into Supersonic Flow, Thomas J. Flora
Freedrop Testing And Cfd Simulation Of Ice Models From A Cavity Into Supersonic Flow, Thomas J. Flora
Theses and Dissertations
Weapon release at supersonic speeds from an internal bay is highly advantageous. For this reason, both experimental and numerical methods were used to investigate store separation from a cavity (L=D=4.5) into Mach 2.94 flow. The experiment used a piezoresistive pressure transducer, Schlieren and high-speed photography for data acquisition. The computational solution used the OVERFLOW solver. A sphere and a Mk-82, scaled to 1:20, were formed using frozen tap water. The sphere model was freedrop tested experimentally and computationally, while the sub-scale store shaped model was freedrop tested experimentally. The total pressure was varied to alter the dynamic response of the …
Genetic Algorithm Optimization Of A Film Cooling Array On A Modern Turbine Inlet Vane, Jamie J. Johnson
Genetic Algorithm Optimization Of A Film Cooling Array On A Modern Turbine Inlet Vane, Jamie J. Johnson
Theses and Dissertations
In response to the need for more advanced gas turbine cooling design methods that factor in the 3-D flowfield and heat transfer characteristics, this study involves the computational optimization of a pressure side film cooling array on a modern turbine inlet vane. Latin hypersquare sampling, genetic algorithm reproduction, and Reynolds-Averaged Navier Stokes (RANS) computational fluid dynamics (CFD) as an evaluation step are used to assess a total of 1,800 film cooling designs over 13 generations. The process was efficient due to the Leo CFD code's ability to estimate cooling mass flux at surface grid cells using a transpiration boundary condition, …
Effects Of Front-Loading And Stagger Angle On Endwall Losses Of High Lift Low Pressure Turbine Vanes, Michael E. Lyall
Effects Of Front-Loading And Stagger Angle On Endwall Losses Of High Lift Low Pressure Turbine Vanes, Michael E. Lyall
Theses and Dissertations
Past efforts to reduce the airfoil count in low pressure turbines have produced high lift profiles with unacceptably high endwall loss. The purpose of the current work is to suggest alternative approaches for reducing endwall losses. The effects of the fluid mechanics and high lift profile geometry are considered. Mixing effects of the mean flow and turbulence fields are decoupled to show that mean flow shear in the endwall wake is negligible compared to turbulent shear, indicating that turbulence dissipation is the primary cause of total pressure loss. The mean endwall flow field does influence total pressure loss by causing …
Unsteady Specific Work And Isentropic Efficiency Of A Radial Turbine Driven By Pulsed Detonations, Kurt P. Rouser
Unsteady Specific Work And Isentropic Efficiency Of A Radial Turbine Driven By Pulsed Detonations, Kurt P. Rouser
Theses and Dissertations
There has been longstanding government and industry interest in pressure-gain combustion for use in Brayton cycle based engines. Theoretically, pressure-gain combustion allows heat addition with reduced entropy loss. The pulsed detonation combustor (PDC) is a device that can provide such pressure-gain combustion and possibly replace typical steady deflagration combustors. The PDC is inherently unsteady, however, and comparisons with conventional steady deflagration combustors must be based upon time-integrated performance variables. In this study, the radial turbine of a Garrett automotive turbocharger was coupled directly to and driven, full admission, by a PDC in experiments fueled by hydrogen or ethylene. Data included …
Increasing Reliability Of A Small 2-Stroke Internal Combustion Engine For Dynamically Changing Attitudes, Steven C. Crosbie
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
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 …
Material Characterization For Composite Materials In Load Bearing Wave Guides, Gabriel Almodovar
Material Characterization For Composite Materials In Load Bearing Wave Guides, Gabriel Almodovar
Theses and Dissertations
This study will establish a methodology to examine samples of composite material for application in a load bearing waveguide. The composite material will operate in a specific frequency range for applications in small RPAs. A graphite epoxy stiffening component will be primarily considered. Different nickel, graphene, and carbon nanotube (CNT) coatings and films will be applied to the graphite epoxy. Tests will determine the material's radio frequency (RF) performance for application as an antenna/waveguide component. The study will use scattering (S) parameters determined from a network analyzer to collect these data. The S parameters will then be used to resolve …
Characterization Of Centrifugally-Loaded Flame Migration For Ultra-Compact Combustors, Kenneth D. Lebay
Characterization Of Centrifugally-Loaded Flame Migration For Ultra-Compact Combustors, Kenneth D. Lebay
Theses and Dissertations
The Air Force Research Laboratory (AFRL) has designed an Ultra Compact Combustor (UCC) showing viable merit for significantly reducing gas turbine combustor length making it a viable candidate for implementation as an inter-turbine burner and realization of efficiency benefits from the resulting near constant temperature cycle. This concept uses an off-axis combustor cavity and projects approximately 66% length reduction over a conventional combustor. The annular nature of the cavity creates high angular acceleration levels, on the order of 500-3500 g's, resulting in strong centrifugal and buoyant forces. This unique combination works to significantly reduce the required burn time and subsequently …
Creep Of Hi-Nicalon S Ceramic Fiber Tows At Elevated Temperature In Air And In Steam, Benjamin R. Steffens
Creep Of Hi-Nicalon S Ceramic Fiber Tows At Elevated Temperature In Air And In Steam, Benjamin R. Steffens
Theses and Dissertations
Structural aerospace components require materials to have superior long-term mechanical properties that can withstand severe environmental conditions, such as high temperatures, high pressures and moisture, whilst enduring the loads they are designed for. Ceramic-matrix composites (CMCs) are capable of maintaining excellent strength and creep resistance at high temperatures, which make them attractive candidate materials for aerospace applications, particularly in propulsion. Silicon Carbide (SiC) ceramic fibers have been used as constituent materials in CMCs, although oxidation of the SiC to SiO2 has been a known degredation mechanism. Recently developed near stoichiometric SiC fibers have shown significant improvements in thermochemical stability; …
Accurate Modeling Of Stability And Control Properties For Fighter Aircraft From Cfd, Jedediah H. Butler
Accurate Modeling Of Stability And Control Properties For Fighter Aircraft From Cfd, Jedediah H. Butler
Theses and Dissertations
Difficulties in obtaining accurate Stability and Control (S&C) data for nonlinear regions in the flight envelope early in the design phase often lead to costly fixes late in the acquisition process. Work examined herein addresses this problem by utilizing recent advances in Computational Fluid Dynamics (CFD) to create a high-fidelity database before any parts have to be physically produced. In combination with CFD, System Identification (SID) is used to characterize the S&C characteristics of aircraft by some Reduced Order Model (ROM). The method of obtaining enough data in the right places, via some optimized maneuver, to create an accurate ROM …
Applications Of Aerodynamic Forces For Spacecraft Orbit Maneuverability In Operationally Responsive Space And Space Reconstitution Needs, Matthew N. Goodson
Applications Of Aerodynamic Forces For Spacecraft Orbit Maneuverability In Operationally Responsive Space And Space Reconstitution Needs, Matthew N. Goodson
Theses and Dissertations
Each year multiple satellites are launched to provide end users key pieces of information. This information ranges from remote sensing data for military or civilian purposes (e.g., weather forecasting, troop movements, agricultural production, etc.) to large bandwidth telecommunications sensors. No matter the type of information needed, society is demanding more. Because of this continual rise in information needs, the current model of launching one satellite for one mission is not sustainable. To satisfy the information needs of nations across the globe, a means for satellites to transition from one mission type to another must be developed. One means of transitioning …
Enhanced Image-Aided Navigation Algorithm With Automatic Calibration And Affine Distortion Prediction, Juan D. Jurado
Enhanced Image-Aided Navigation Algorithm With Automatic Calibration And Affine Distortion Prediction, Juan D. Jurado
Theses and Dissertations
This research aims at improving two key steps within the image aided navigation process: camera calibration and landmark tracking. The camera calibration step is improved by automating the point correspondence calculation within the standard camera calibration algorithm, thereby reducing the required time for calibration while maintaining the output model accuracy. The feature landmark tracking step is improved by digitally simulating affine distortions on input images in order to calculate more accurate feature descriptors for improved feature matching in high relative viewpoint change. These techniques are experimentally demonstrated in an outdoor environment with a consumer-grade inertial sensor and three imaging sensors, …
Integration, Testing And Validation, Of A Small Hybrid-Electric Remotely-Piloted Aircraft, Joseph K. Ausserer
Integration, Testing And Validation, Of A Small Hybrid-Electric Remotely-Piloted Aircraft, Joseph K. Ausserer
Theses and Dissertations
Parallel hybrid-electric technology offers a wide variety of new mission capabilities including low-observable loiter operations and increased fuel efficiency for small remotely-piloted aircraft. This research focused on the integration, validation, and testing of a hybrid-electric propulsion system consisting of commercially available components to fabricate a small remotely-piloted aircraft capable of extended low-observable operation. Three novel aspects contributed to the success of the design: optimization of the propulsive components to the integrated system, torque control of the components for additive power, and a one-way bearing/ pulley mechanism (patent pending) mechanically linking the hybrid system components. To the knowledge of the author …
Gravitational Lens: Deep Space Probe Design, Berkley R. Davis
Gravitational Lens: Deep Space Probe Design, Berkley R. Davis
Theses and Dissertations
A number of interstellar precursor missions have been designed, but they have all made use of unproven future technologies. This research focuses on designing an interstellar precursor mission to the gravitational lens that can be manufactured solely with today's technology. The design includes an examination of trip time and trajectory, a system trade between subsystems, a launch vehicle analysis and an overall spacecraft performance analysis. The trip time was found to be approximately 108 years using the NEXT thruster and GPHS power source. The GPHS provided approximately 4 kW of power at BOL. The communications subsystem relied on a 12 …
Validation Of The Chemistry Module For The Euler Solver In Unified Flow Solver, William C. Humphrey Jr.
Validation Of The Chemistry Module For The Euler Solver In Unified Flow Solver, William C. Humphrey Jr.
Theses and Dissertations
In the world of computational fluid dynamics (CFD), three main types of flow regimes exist: continuum, rarified, and free molecular. Of these regimes, the rarified regime is the most difficult to model because the continuum equations don't apply and using the Boltzmann equation is too computationally expensive to use. The Unified Flow Solver (UFS) is currently being developed to solve this problem by using the kinetic continuum Euler equations where valid, and only using the Boltzmann equation where necessary, thus reducing the computational cost. The use of the kinetic Euler equations helps to aid in the coupling of the Euler …
Development And Testing Of A Rotating Detonation Engine Run On Hydrogen And Air, Jason C. Shank
Development And Testing Of A Rotating Detonation Engine Run On Hydrogen And Air, Jason C. Shank
Theses and Dissertations
Rotating detonation engines (RDEs) have the potential for greater efficiencies over conventional engines by utilizing pressure gain combustion. A new modular RDE (6 in diameter) was developed and successfully run on hydrogen and standard air. The RDE allows for variation of injection scheme and detonation channel widths. Tests provided the operational space of the new RDE as well as characterized detonation unsteadiness. It was found that a smaller equivalence ratio than previous was required to obtain continuous detonations. Also discovered was VCJ was reached in the RDE, but not sustained.
Boundary Layer Measurements In The Trisonic Gas-Dynamics Facility Using Particle Image Velocimetry With Co₂ Seeding, Daniel B. Wolfe
Boundary Layer Measurements In The Trisonic Gas-Dynamics Facility Using Particle Image Velocimetry With Co₂ Seeding, Daniel B. Wolfe
Theses and Dissertations
Particle image velocimetry (PIV) is utilized with solid carbon dioxide (CO2) seeding material to conduct boundary layer measurements in the test section of the Air Force Research Laboratory's Trisonic Gas-dynamics Facility (TGF), which has a 24 inch by 24 inch cross-section. Freestream velocity was set at Mach 0.3, Mach 0.5, or Mach 0.8 while stagnation pressure ranged from 500 to 2400 pounds per square foot (psf). High pressure liquid CO2 was directed through expansion nozzles into shroud tubes which led to solidified particles in the wind tunnel stagnation chamber. Two different sets of shroud tubes were used …
Empirical Characterization Of Unconstrained Tape Spring Deployment Dynamics, Daniel M. Williams
Empirical Characterization Of Unconstrained Tape Spring Deployment Dynamics, Daniel M. Williams
Theses and Dissertations
Satellite cost and mission capability are very sensitive to mass requirements. Mass or volume savings in one component will either lower total spacecraft mass, or provide greater margin for design error in other components. Solar arrays and antennas in particular are often driven by launch vehicle volume constraints instead of mission needs. Deployable structures provide more on-orbit area for both solar arrays and antennas, while occupying less space during launch. These structures therefore, help address these constraints and have been proven as efficient solutions for many years. Tape springs are one example in this category of structures which offer greater …
Trajectory Control And Optimization For Responsive Spacecraft, Costantinos Zagaris
Trajectory Control And Optimization For Responsive Spacecraft, Costantinos Zagaris
Theses and Dissertations
The concept of responsive space has been gaining interest, and growing to include systems that can be re-tasked to complete multiple missions within their lifetime. The purpose of this study is to develop an algorithm that produces a maneuver trajectory that will cause a spacecraft to arrive at a particular location within its orbit earlier than expected. The time difference, delta t, is used as a metric to quantify the effects of the maneuver. Two separate algorithms are developed. The first algorithm is an optimal control method and is developed through Optimal Control Theory. The second algorithm is a feedback …