Engineering Commons^™

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 …

Satellite Relative Motion Control For Mit's Spheres Program, Samuel P. Barbaro

Theses and Dissertations

Autonomous formation flight concepts and algorithms have great potential to revolutionize spacecraft operations enabling missions to perform autonomous docking, in-space refueling, in-space robotic assembly, and space debris removal. Such tasks require the implementation of speed and path control algorithms to maneuver satellites along relative paths with specified rates along those paths. This thesis uses MATLAB® and SIMULINK® to design and simulate a control algorithm capable of providing relative speed and path control between satellites with a pointing error of less than two degrees, a position error of less than two millimeters, and a millimeter per second of velocity error. The …

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 …

Cubesat Attitude Determination And Helmholtz Cage Design, Megan R. Brewer

Theses and Dissertations

A method of 3-axis satellite attitude determination utilizing six body-fixed light sensors and a 3-axis magnetometer is analyzed. A Helmholtz cage is designed, built, and tested to provide a dynamic, 3-axis, uniform magnetic field to cancel the Earth's magnetic field and create an environment similar to the geomagnetic field a satellite would experience on-orbit. A CubeSat is provided the inertial magnetic vector and Sun vector, which are combined with data from the light sensors and magnetometer in a CubeSat. Attitude is estimated on-board the CubeSat via the optimal fast quaternion estimation algorithm. The capabilities of the Helmholtz cage, including the …

Computational Analysis And Characterization Of Rc-135 External Aerodynamics, Michael G. Chenery

Theses and Dissertations

Both the RC-135V/W Rivet Joint (RJ) and the RC-135U Combat Sent (CS) aircraft are United States Air Force (USAF) electronics reconnaissance platforms. The RJ is the USAF's standard airborne signals intelligence (SIGINT) gathering platform, while the CS is designed to collect technical intelligence on adversary radar emitter systems. Both aircraft are extensively modified C-135's characterized by protruding cheek fairings along the sides of the fuselage forward of the wings as well as the addition of numerous antennas along the top and bottom of the fuselage. The major distinguishing feature between the two variants is the nose radome, wherein the RJ …

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 …

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 …

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 …

Cooling Requirements For The Ultra Compact Combuster, Donald D. Johnson

Theses and Dissertations

Over the past several years, AFIT and the Air Force Research Laboratory have collaboratively investigated a novel combustor system that is compact in design and has potential use in an inter-turbine burner system. The ultra-compact combustor (UCC) design wraps the combustion section circumferentially around the axial core flow and exploits the use of high-g combustion. The combustor's volume and weight are reduced by integrating the exit compressor vane and the turbine inlet vane. This creates a new hybrid vane that resides directly below the circumferential combustor. Recently, a computational effort to understand the fundamental aspects of the UCC on a …

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 …

Methane Dual Expander Aerospike Nozzle Rocket Engine, Michael D. Moen

Theses and Dissertations

The Air Force Institute of Technology (AFIT), working to meet requirements set by the Air Force Research Laboratory's Next Generation Engine (NGE) initiative, is developing upper stage rocket models. The current path of investigation focuses on combining a dual expander cycle with an aerospike nozzle, or the Dual Expander Aerospike Nozzle (DEAN) using methane fuel. The design process will rely heavily on AFIT's previous work, which focused on the development of tools for and the optimization of a hydrogen/oxygen DEAN engine. The work outlined in this paper expands the existing research by substituting methane for hydrogen. The targets derived from …

Application Of Multi-Input Multi-Output Feedback Control For F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators, Tomoyuki D. Ono

Theses and Dissertations

Control of structural vibrations has been a popular topic. Use of MFC piezoelectric actuators and co-located sensors allows for an active rather than passive control method. The F-16 ventral fin is susceptible to buffet induced vibrations and is a perfect test structure for active vibration control for flight-testing. The research follows the previous ACTIVE FIN project and improves on the design by increasing the number of actuator layers, available actuator power, and using multi-input multi-output (MIMO) control algorithms. The research involved experimental identification of the ventral fin and its principle strain directions, selection of system components, determination of mathematical plant …

Development Of A Star Tracker-Based Reference System For Accurate Attitude Determination Of A Simulated Spacecraft, Jorge G. Padro

Theses and Dissertations

The goal of this research effort is to investigate the analysis, design, integration, testing, and validation of a complete star tracker and star field simulator system concept for AFIT's satellite simulator, SimSat. Previous research has shown that while laboratory-based satellite simulators benefit from star trackers, the approach of designing the star field can contribute significant error if the star field is generated on a flat surface. To facilitate a star pattern that better represents a celestial sky, a partially hemispherical dome surface is suspended above SimSat and populated with a system of light emitting diodes of various intensities and angles …

Desensitizing Flame Structure And Exhaust Emissions To Flow Parameters In An Ultra-Compact Combuster, Adam K. Parks

Theses and Dissertations

A major thrust of turbine engine research is to improve both efficiency and thrust-to-weight ratio of the engine. A promising solution to this challenge is the Ultra-Compact Combustor (UCC). The UCC shortens the axial length of the combustor by performing combustion circumferentially on the outer diameter of the engine. The reduction in axial length yields significant weight savings and increases the thrust-to-weight ratio. The design also increases combustion efficiency by performing the combustion in a centrifugally loaded environment which allows unreacted particles to remain in the combustor sufficiently long enough to become combustion products. The Air Force Institute of Technology …

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.

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; …

A Finite Element Analysis Of A Carbon Fiber Composite Micro Air Vehicle Wing, Theodore A. Szelag

Theses and Dissertations

Micro-air vehicles (MAV)s provide a valuable and low observable way to do the jobs that the Air Force deems to be dull, dirty and dangerous. Basing the design of an MAV wing on that of a biological counterpart will provide a proven design that is capable of achieving the mission requirements. This research is designed to analyze the design and manufacturing of a wing based off the Manduca Sexta.

Inaccuracies in the fiber orientation can result in substantial changes in the material properties. Experimental vibration data of composite material samples manufactured using a three-ply [0/90/0] small non-homogenous fiber composite provided …

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 …

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 …

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 …

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, …

Impact Of Trench And Ramp Film Cooling Designs To Reduce Heat Release Effects In A Reacting Flow, Michael R. Delallo

Theses and Dissertations

Increasing combustor fuel-air ratios are a recent area of concern in gas turbine film cooling due to the potential for heat release on the surface of film-cooled components. This investigation compared four different cooling designs on their heat release potential: namely fanned, normal and radial trenched, and ramped. Measurements of heat flux to the downstream surface, when subjected to a reacting mainstream flow, provide a qualitative comparison between the four tested configurations. Furthermore, this work studied the effect of multiple injection points in series along the surface of a flat plate. An upstream set of normal holes and an upstream …

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 …

Determination Of Effective Crossover Location And Dimensions For Branched Detonation In A Pulsed Detonation Engine, Louis A. Camardo Ii

Theses and Dissertations

A study is presented of the optimal crossover duct location and width to obtain consistent branched detonation transition from one detonation tube to another. On a Pulsed Detonation Engine (PDE) with detonation branching, the duct location at which the detonation crosses from one (primary) tube to a branched (secondary) tube impacts the number of successful detonations. In this paper, a comparison is made of the effects of the location and width of the crossover duct for hydrogen, ethylene and an n-alkane. The crossover location is varied from the aft end of the detonation tube to the middle of the detonation …

Hybrid Solution Of Stochastic Optimal Control Problems Using Gauss Pseudospectral Method And Generalized Polynomial Chaos Algorithms, Gerald C. Cottrill

Theses and Dissertations

Two numerical methods, Gauss Pseudospectral Method and Generalized Polynomial Chaos Algorithm, were combined to form a hybrid algorithm for solving nonlinear optimal control and optimal path planning problems with uncertain parameters. The algorithm was applied to two concept demonstration problems: a nonlinear optimal control problem with multiplicative uncertain elements and a mission planning problem sponsored by USSTRATCOM. The mission planning scenario was constructed to find the path that minimizes the probability of being killed by lethal threats whose locations are uncertain to statistically quantify the effects those uncertainties have on the flight path solution, and to use the statistical properties …

Conceptual Layout Of Wing Structure Using Topology Optimization For Morphing Micro Air Vehicles In A Perching Maneuver, James R. Elgersma

Theses and Dissertations

A topology optimization model for conceptual wing structure layouts of morphing micro air vehicles (MAVs) has been developed and implemented in MATLAB. Specifically, a six degree-of-freedom finite element (FE) model with a general quadrilateral discretization scheme was created by superposition of a known simple linear plane membrane element and a Kirchhoff plate bending element derived herein. The purpose of the six degree-offreedom model was to accommodate in-plane and out-of-plane aerodynamic loading combinations. The FE model was validated and the MATLAB implementation was verified with classical beam and plate solutions. A compliance minimization optimization objective was then formulated with the Solid …

Build Up And Operation Of An Axial Turbine Driven By A Rotary Detonation Engine, Jonathan R. Tellefsen

Theses and Dissertations

Detonation combustors provide advantages over current deflagration combustors due to their pressure gain and simplicity of design. Rotary detonation engines (RDEs) offer advantages over pulsed detonation engines (PDEs) due to a steadier exhaust and fewer total system losses. All previous research on turbine integration with detonation combustors has focused on utilizing PDEs to drive axial and centrifugal turbines. The objective of this thesis was the integration and testing of an axial turbine driven by a rotary detonation engine (RDE) to determine turbine operability. In pursuit of this objective, convergent nozzle sections were placed on the RDE to simulate the back-pressurization …

Reynolds Number Effects On Thrust Coefficients And Piv For Flapping Wing Micro Air Vehicles, John P. Tekell

Theses and Dissertations

For the last several years the Air Force Institute of Technology (AFIT) has conducted research in aerodynamics for flapping wing micro air vehicles (MAVs). The focus of this research was to augment this effort by measuring thrust, velocity, and torque in tanks of water and glycerin using a scale and a reaction torque cell. The results for different flapping mechanisms are compared to a rotating propeller with the goal of elucidating the design trade space between rotorcraft and flapping wings at Reynolds numbers less than 100,000. In addition, flow visualization and quantitative velocity data were captured in the wake of …

Integration Of Cold Atom Interferometry Ins With Other Sensors, Aaron J. Canciani

Theses and Dissertations

Inertial navigation systems (INS) using cold-atom interferometry are currently under development, and sensors in these systems are expected to be several orders of magnitude more ccurate than current navigation grade sensors. This signi cant increase in accuracy motivates the need to explore how these high accuracy inertial navigation systems can be integrated with other sensors. This research focuses on methods of integrating cold atom interferometry INS with conventional navigation grade INS, as well as with GPS. Results from a full 6 degree of freedom simulation show that integrating CAI INS with navigation grade INS is a successful way to address …

Aircraft Course Optimization Tool Using Gpops Matlab Code, Ryan D. Gauntt

Theses and Dissertations

Aircraft course planning between two points in a clear, no threat environment is easy and straightforward. However, the addition of various threats can greatly increase the difficulty and complexity of course planning. Placing new waypoints along the edge of each threat, mostly skirting the dangerous environment, may not prove too difficult, but such courses are far from optimal. Given aircraft, environment, and time constraints it is likely a much more optimal path exists between any given start and end points. This research focuses on determining the feasibility of using the General Pseudospectral Optimization Software program files written for the MATLAB …