Engineering Commons^™

Porous Emitter Colloid Thruster Performance Characterization Using Optical Techniques, Eric T. Wolf

Theses and Dissertations

This research focuses on experimentally characterizing the performance parameters of a colloid thruster with porous emitters through optical techniques. Porous emitters are different than traditional needle emitters in how they allow a variation in the number and size of Taylor Cones throughout a range of propellant volumetric flow rate conditions. An algorithm is created to calculate the estimated minimum and maximum number of emitter sites based on magnified images of the porous emitter heads. Theoretical thruster performance parameters are then established from the estimated number of emitter sites. Experimental techniques for measuring the thrust and exhaust exit velocity are proposed. …

Training Maneuver Evaluation For Reduced Order Modeling Of Stability & Control Properties Using Computational Fluid Dynamics, Craig C. Porter

Theses and Dissertations

System identification has long been used as a tool for flight test engineers to characterize systems under test; however, the inputs to these characterization activities have previously been limited to wind tunnel and flight test data. There has been a recent effort to incorporate computational fluid dynamics (CFD) into the system identification process. An integral piece of the process is the simulation of training maneuvers utilizing CFD. Up until now, the suitability of particular training maneuvers has been assessed by comparing the reduced model to known results. This research strives to recommend a set of parameters to be used in …

High Frequency Magnetic Field Direction Finding Using Mgl-S8a B-Dot Sensors, Michael D. Archer

Theses and Dissertations

Aircraft based direction finding (DF) in the high frequency (HF) band is difficult due to the aircraft's size with respect to wavelength and limited azimuthal resolution. A B-dot sensor is useful for detection of the time varying magnetic field and offers improved integration into an aircraft. What the B-dot sensor gains in integration it gives up in sensitivity because it is designed for frequencies above 5 GHz. Design of an airborne HFDF array using Bdot sensors is based in maximizing the physical extent of the array and eliminating multiple main beams. The goals of this research are to complete a …

Creep Of Hi-Nicalon S Fiber Tows At Elevated Temperature In Air And In Steam, Theodore R. Shillig

Theses and Dissertations

Structural aerospace components require materials that have superior long-term mechanical properties and can withstand severe environmental conditions, such as high temperatures, high pressures and moisture. Ceramic-matrix composites (CMCs) are capable of maintaining excellent strength and creep resistance at high temperatures, which makes them attractive candidate materials for aerospace applications, particularly in propulsion components. Silicon Carbide (SiC) ceramic fibers have been used as constituent materials in CMCs, although oxidation of the SiC to SiO2 has been a known fiber degradation mechanism. Recently developed near stoichiometric Hi-Nicalon-S fibers have shown significant improvements in thermo-chemical stability. Creep of the Hi-Nicalon-S fibers at elevated …

Information Encoding On A Pseudo Random Noise Radar Waveform, Joshua A . Hardin

Theses and Dissertations

Navigation requires knowledge of current location and a planned destination. This is true with manned vehicles and unmanned vehicles. There are many ways to acquire the current location, including global positioning system (GPS), triangulation, radar, and dead reckoning. Today GPS is the most reliable and accurate navigation technique when there is a clear, unobstructed view of the satellite constellation. Various sensors can be used to perform indoor navigation; however, when the vehicle is autonomous the sensors need to provide the exact location to the system. This research determined if using a template replay strategy has the same RNR performance as …

Error Characterization Of Vision-Aided Navigation Systems, Daniel A . Marietta

Theses and Dissertations

The goal of this work is to characterize the errors committed by an Image Aided Navigation (IAN) algorithm that has been developed for use as a navigation tool in GPS denied areas. The filter under study was developed by the Air Force Institute of Technology's Advanced Navigation Technology center, and has been the focus of numerous research efforts. Unfortunately, these studies have all been based on single runs or simulations, and such results may not be indicative of the true filter performance. This problem extends to IAN publications in general; no analysis of IAN based upon a sizable real world …

Inertial Navigation System Aiding Using Vision, James O. Quarmyne

Theses and Dissertations

The aiding of an INS using measurements over time of the line of sight of ground features as they come into view of an onboard camera is investigated. The objective is to quantify the reduction in the navigation states' errors by using bearings-only measurements over time of terrain features in the aircraft's field of view. INS aiding is achieved through the use of a Kalman Filter. The design of the Kalman Filter is presented and it is shown that during a long range, wings level cruising flight at constant velocity and altitude, a 90% reduction in the aided INS-calculated navigation …

Adaptations And Analysis Of The Afit Noise Radar Network For Indoor Navigation, Russell D. Wilson Iv

Theses and Dissertations

After several years of development, the AFIT Noise Radar Network (NoNET) has proven to be an extremely versatile system for many standard radar functions. This pallet of capabilities includes through the wall target tracking capabilities due to its wide bandwidth and UHF operations. Utilizing White Gaussian Noise as its waveform, the NoNET can operate at much lower power levels than other comparable systems while remaining extremely covert. In an effort to explore new applications, the question arose could the NoNET provide a viable option for navigation capability in GPS denied and indoor environments? This research aims to provide proof of …

Supplementary Computer Generated Cueing To Enhance Air Traffic Controller Efficiency, Laurienne Cibelle Rodrigues De Assis Santana

Theses and Dissertations

Air traffic controllers are often required to simultaneously communicate with several aircraft over multiple radio frequencies. As a result, during peak loading, it is common for the controller to receive multiple concurrent communications, each from a different aircraft, making it difficult to discern audio messages received from multiple pilots simultaneously. To address this problem, a modified air traffic control (ATC) interface was prototyped with the goal of increasing controller-to-pilot communication efficiency. This prototype included supplementary text cueing which was provided by a hypothetical automated text to speech system in an on-screen text box for controller reference in the event of …

Development Of Autonomous Optimal Cooperative Control In Relay Rover Configured Small Unmanned Aerial Systems, Timothy J. Shuck

Theses and Dissertations

This thesis documents the research effort to develop, integrate and implement the system hardware and the software necessary to validate the Air Force Institute of Technology's theoretical advances in small unmanned aerial systems (SUAS) cooperative control. The end state objective of the research effort was to flight test an autonomous control algorithm on a communication relay unmanned aerial vehicle (UAV) that was actively relaying data to and from a rover UAV. The relay UAV is one part of a SUAS designed to utilize cooperative control to extend the effective line-of-sight operating range for a rover UAV. An algorithm is integrated …

Heat Exchanger Design And Testing For A 6-Inch Rotating Detonation Engine, Scott W. Theuerkauf

Theses and Dissertations

This thesis explains the design and testing of a water-cooled rotating detonation engine (RDE) run on hydrogen and air. The change in water temperature as it cooled the engine was used to find the steady heat rate into the containing walls of the detonation channel. The engine successfully ran four times for 20 seconds each. The steady-state heat rate was measured to be 2.5% of the propellant lower heating value (LHV) into the outer wall and 7.1% of LHV into the inner wall. Additionally, a quick-response resistance temperature detector (RTD) was used in an uncooled RDE of similar dimension to …

Real-Time Heading Estimation Using Perspective Features, James W. Dean

Theses and Dissertations

There are a large number of commercially available quad-rotor helicopters available from various manufacturers. All of these systems rely on a low cost MEMS based inertial measurement system for stabilization and navigation. These low cost inertial systems are all subject to rapid error growth in their attitude and position estimates unless bounded by external measurements. This thesis created real-time algorithm to integrate measurements from visual cues with measurements from onboard sensors to estimate the attitude position and velocity of a quad-rotor helicopter in a local navigation frame, a system model for the ARDrone, and a feed-back controller for the vehicle's …

Aerial Networking For The Implementation Of Cooperative Control On Small Unmanned Aerial Systems, Scott A . Songer

Theses and Dissertations

The employment of Small Unmanned Aerial Systems (SUAS) for reconnaissance and surveillance missions is a vital capability of the United States military. Cooperative control algorithms for SUAS can enable tactical multi-vehicle configurations for communications extension, intelligent navigation, and a multitude of other applications. Past research at AFIT has designed and simulated a cooperative rover-relay algorithm for extended communications and has investigated its implementation through various modem configurations. This research explores aerial networking options for implementing cooperative control and applies them to an actual SUAS. Using Commercial Off-The-Shelf (COTS) hardware, a system was designed and flight tested to implement the rover-relay …

Power Requirements For Bi-Harmonic Amplitude And Bias Modulation Control Of A Flapping Wing Micro Air Vehicle, Justin R. Carl

Theses and Dissertations

Flapping wing micro air vehicles (FWMAV) have been a growing field in the research of micro air vehicles, but little emphasis has been placed on control theory. Research is ongoing on how to power FWMAVs where mass is a major area of concern. However, there is little research on the power requirements for the controllers to manipulate the wings of a FWMAV. A novel control theory, BABM, allows two actuators to produce forces and moments in five of the FWMAV's six DOF. Several FWMAV prototypes were constructed and tested on a six-component balance. Data was collected for varying control parameters …

Integration Of An Inter Turbine Burner To A Jet Turbine Engine, Matthew M. Conrad

Theses and Dissertations

As aircraft power requirements continue to grow, whether for electrical systems or increased thrust, improved engine efficiency must be found. An Ultra-Compact Combustor (UCC) is a proposed apparatus for accomplishing this task by burning in the circumferential direction as a main combustor or an Inter-Turbine Burner (ITB). In order for the UCC to be viable it is important to study the effects of feeding the core and circumferential flows from a common gas reservoir. This research effort has developed a diffuser, for the AFIT Combustion Laboratory, that is capable of 80/20, 70/30, and 60/40 mass flow splits between the core …

Opto-Mechanical Design Of A Chromotomographic Imager Direct-Vision Prism Element, Timothy E. Coon

Theses and Dissertations

Chromotomographic Imaging (CTI) offers advantages in remote sensing by resolving intensity distribution spatially, spectrally, and temporally. The Chromotomography Experiment (CTEx) at the Air Force Institute of Technology (AFIT) explores the application of CTI as a space-based observer. Previous work in instrument development has revealed many of the intricacies of component fabrication and how they impact the resolving of image data. The proposed CTEx instrument has as its chromatic dispersion element a direct-vision prism (DVP) that is made to rotate in order to achieve multiple projection angles. Analysis of previous research established the need for a more accurate characterization of the …

Using Hysteretic Energy To Evaluate Damping Characteristics Of Hard Coating On Titanium, Colin C. Engebretsen

Theses and Dissertations

Current methods of material damping evaluation consist of bending tests involving half-power bandwidth base excitation or free decay methods measured by laser vibrometer. These methods are accompanied by complex, nonlinear strain evaluation; they are vulnerable to undesired air damping; and they require less than commonplace equipment. The measurement of hysteretic energy loss in axial cyclic loading alleviates these difficulties. By using common tensile testing machines, strain is kept linear and air damping is of no concern. Furthermore, the static test section allows for simplified environmental variation for high temperature or high humidity testing. This study set forth to advance and …

Dynamic Constellation Tasking And Management, Steven P. Ingraham

Theses and Dissertations

Responsive orbits have gained much attention in recent years and many AFIT theses have addressed this topic. Specifically, the following topics have been studied: phasing within an orbit, adjusting time of arrival, avoidance, and maneuver detection. This thesis seeks to determine the feasibility of maneuvering satellites from circular (600 km) orbits to eccentric (600 km by 175 km) orbits in order to collect high resolution images for Earth surveillance. Coverage is calculated for multiple 6-satellite constellations. Perturbations for the subject orbits are analyzed and compared to simulation results.

Design Of A Control Moment Gyroscope Attitude Actuation System For The Attitude Control Subsystem Proving Ground, Samuel C. Johnson

Theses and Dissertations

All spacecraft represent a considerable investment of both time and money. To ensure mission success, testing and validation of all vital systems is crucial to the design process. The attitude control subsystem (ACS) is typically tested thoroughly, to include both hardware and control algorithms. Computer simulations offer a simple and relatively cheap method of predicting the performance of the ACS; however, computer simulations cannot provide the assurances necessary to qualify an ACS hardware configuration or control algorithm spaceworthy. For this reason, physical spacecraft simulators must be used to validate ACS dynamics. Previous research showed there is room for significant improvement …

Experimental Analysis Of Dampened Breathing Mode Oscillation On Hall Effect Thruster Performance, Christopher D. Vineski

Theses and Dissertations

Experiments were performed at AFIT to determine the effect of active control of the magnetic field strength to reduce the breathing mode oscillation on the efficiency of a 200W Hall thruster. The breathing mode oscillation amplitude was measured by the root mean square (RMS) variation in the AC portion of the discharge current. Experiments were run using krypton and xenon propellant. Using the xenon propellant control of the RMS improved the propellant utilization efficiency by approximately 2% in two cases, while reducing the magnet current efficiency by about 10%. Control of the RMS's effect on the divergence angle of the …

Effects Of Stereoscopic 3d Digital Radar Displays On Air Traffic Controller Performance, Jason G. Russi

Theses and Dissertations

Air traffic controllers are responsible for directing air traffic based upon decisions made from traffic activity depicted on 2Dimensional (2D) radar displays. Controllers must identify aircraft and detect potential conflicts while simultaneously developing and executing plans of action to ensure safe separation is maintained. With a nearly 100% increase in traffic expected within the next decade (FAA, 2012a), controllers' abilities to rapidly interpret spacing and maintain awareness for longer durations with increased workload will become increasingly imperative to safety. The current display design spatially depicts an aircraft's position relative to the controller's airspace as well as speed, altitude, and direction …

Comm-Using Decibels, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs on "Comm-Using Decibels" from March 14, 2014.

Towards A “Cloud Curriculum” In Art And Science?, Roger Malina

The Transdisciplinary STEAM+ Journal

Recently an email hit my desk from Paul Thomas in Australia with a proposal to work together on a “Cloud Curriculum for Art and Science”. I immediately agreed to collaborate. I don’t yet have a clue of what a cloud curriculum is, but what I do know is that we are ‘backing into the future’ in educational institutions and we desperately need a ‘cloud curriculum.’ We need to look over the ten year horizon. And in the emerging art-science field I doubt that the usual approach to curriculum development will work.

Design Of A Specimen Fixture For Impact Resistance Testing In An Instron Dynatup 8250 Drop Weight Impact Tester, Daniel Alejandro Barath

Aerospace Engineering

The purpose of this report is to outline the path and methods used to design a specimen fixture for the testing and analysis of fiber reinforced composites subjected to impact loading. This design is done in support of the California Polytechnic State University in San Luis Obispo Structures and Composites Laboratory. The design request was made at the request of Dr. Eltahry Elghandour to support the graduate students Kodi A. Rider and Y. Vanessa Wood in their master’s degree thesis projects.

The design request involved the design of a specimen fixture compatible with the existing impact apparatus located in the …

Influence Of Wing Span On The Aerodynamics Of Wings In Ground Effect, Sammy Diasinos, Tracie J. Barber, Graham Doig

Aerospace Engineering

A computational fluid dynamics study of the influence of wing span has been conducted for an inverted wing with endplates in ground effect. Aerodynamic coefficients were determined for different spans at different ground clearances, highlighting a trend for shorter spans to delay the onset of both separation and resulting loss of negative lift. The vortices at the wing endplates were not observed to change significantly in terms of strength and size; thus, at shorter spans, their influence over a larger percentage of the wing helped the flow stay attached and reduced the severity of the adverse pressure gradient which invokes …

Implementing A Matlab Based Attitude Determination Algorithm In C Within The Polysat Software Architecture, Dominic Bertolino

Computer Engineering

This project focuses on one component within a complete attitude determination and control system (ADCS) for a small satellite. The component consists of porting the algorithm that determines the current attitude of the satellite developed by AERO students / team members. The original algorithm has been developed in MATLAB code. The actual algorithm will be simulated and tested in MATLAB by the AEROs. The porting consisted of integrating the pieces into the custom PolySat software environment in C. Testing was done to verify the ported component corresponded to the original MATLAB component as well as verify its runtime on the …

Senior Project Report - Doctest, Stephen Weessies

Computer Engineering

DocTest is a program that, simply put, allows a programmer or user to document STANAG 4586 (a standard for unmanned aerial vehicle interoperability) messages and test the vehicle system at Lockheed Martin [5]. The program is extensible to allow for further development aiding our software team to do what they do best and not get bogged down in tedious but necessary documentation. DocTest is also used to aid in testing, keeping track of the issues and bugs found and creating a document that captures each issue so an issue is not missed or forgotten. This program was made for use …

A Gravity Gradient, Momentum-Biased Attitude Control System For A Cubesat, Ryan J. Sellers

Master's Theses

ExoCube is the latest National Science Foundation (NSF) funded space weather CubeSat and is a collaboration between PolySat, Scientific Solutions Inc. (SSI), the University of Wisconsin, NASA Goddard and SRI International. The 3U will carry a mass spectrometer sensor suite, EXOS, in to low earth orbit (LEO) to measure neutral and ionized particles in the exosphere and thermosphere. Measurements of neutral and ion particles are directly impacted by the angle at which they enter EXOS and which leads to pointing requirements. A combination of a gravity gradient system with a momentum bias wheel is proposed to meet pointing requirements while …

Ad-Hoc Regional Coverage Constellations Of Cubesats Using Secondary Launches, Guy G. Zohar

Master's Theses

As development of CubeSat based architectures increase, methods of deploying constellations of CubeSats are required to increase functionality of future systems. Given their low cost and quickly increasing launch opportunities, large numbers of CubeSats can easily be developed and deployed in orbit. However, as secondary payloads, CubeSats are severely limited in their options for deployment into appropriate constellation geometries.

This thesis examines the current methods for deploying cubes and proposes new and efficient geometries using secondary launch opportunities. Due to the current deployment hardware architecture, only the use of different launch opportunities, deployment direction, and deployment timing for individual cubes …

Film Cooling In Fuel Rich Environments, Jacob J. Robertson

Theses and Dissertations

The ultra compact combustor is a high performance gas turbine design concept that portends reduced weight for future weapons platforms. A natural outcome of the design is the continual presence of fuel-rich air in the turbine component of the engine. Because modern cooling schemes for hot section turbine blades involve injecting cool, oxygen-rich air adjacent to the surface, the potential arises for reaction with the unconsumed radicals in the mainstream ow and augmented heat transfer to the blade. This outcome is contrary to the purpose of film cooling, and can lead to early life-cycle turbine failure. This study examined the …