Aerospace 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. …

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 …

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 …

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 …

Experimental Characterization Of The Structural Dynamics And Aero-Structural Sensitivity Of A Hawkmoth Wing Toward The Development Of Design Rules For Flapping Wing Micro Air Vehicles, Aaron G. Norris

Theses and Dissertations

A case is made for why the structures discipline must take on a more central role in the research and design of flapping-wing micro-air-vehicles, especially if research trends continue toward bio-inspired, insect-sized flexible wing designs. In making the case, the eigenstructure of the wing emerges as a key structural metric for consideration. But with virtually no structural dynamic data available for actual insect wings, both engineered and computational wing models that have been inspired by biological analogs have no structural truth models to which they can be anchored. An experimental framework is therefore developed herein for performing system identification testing …

Biaxial (Tension-Torsion) Testing Of An Oxide/Oxide Ceramic Matrix Composite, Joseph M. Derienzo

Theses and Dissertations

High temperatures and structural loads in advanced aerospace structures often result in complex loading conditions. This study is focused on biaxial (tension-torsion) testing of an oxide-oxide porous matrix ceramic matrix composite (CMC) (NextelTM 720/AS) thin wall tube with a novel involute layup. Tests included pure torsion and biaxial (tension- torsion) loading. Strain gages were used in addition to digital image correlation (DIC) to measure strains and to detect crack initiation and propagation. Room temperature and 1100°C uniaxial tests were performed in a build up approach prior to biaxial (tension-torsion) testing. Double-notch shear (DNS) specimens were tested at 1100°C in air …

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.

A Study Of The Thermal Environment Developed By A Traveling Slipper At High Velocity, Kathleen H. Le

Theses and Dissertations

The research presented in this thesis is developed from the relative sliding motion of a traveling slipper and stationary rail at the Holloman High Speed Test Track located at Holloman AFB, NM. The high velocity condition of the slipper traveling down the rail creates a thermal environment that is of interest to the researchers at the Air Force Institute of Technology. The high temperatures coupled with high velocity leads to a non-linear problem known as melt wear. The goal of this research is to characterize the amount of heat flow going into the slipper as it traverses the rail and …

Development Of Optimized Piezoelectric Bending Actuators For Use In An Insect Sized Flapping Wing Micro Air Vehicle, Robert K. Lenzen

Theses and Dissertations

Piezoelectric bimorph actuators, as opposed to rotary electric motors, have been suggested as an actuation mechanism for flapping wing micro air vehicles (FWMAVs) because they exhibit favorable characteristics such as low weight, rapidly adaptable frequencies, lower acoustic signature, and controllable flapping amplitudes. Research at the Air Force Research Labs and the Air Force Institute of Technology has shown that by using one actuator per wing, up to five degrees of freedom are possible. However, due to the weight constraints on a FWMAV, the piezoelectric bimorph actuators need to be fully optimized to support free flight. This study focused on three …

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 …

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 …

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 …

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 …

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 …

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 …

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 …