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Articles 451 - 480 of 1780
Full-Text Articles in Aerospace Engineering
Modeling And Control Of A 6-Dof Multi-Rotorcraft: Air-Ball, Jerry Ja Wang
Modeling And Control Of A 6-Dof Multi-Rotorcraft: Air-Ball, Jerry Ja Wang
Theses and Dissertations
The Air-Ball project seeks to develop an omnidirectional, unmanned aerial vehicle with six degrees of freedom. The Air-Ball vehicle uses six propellers powered by six independent electric motors for propulsion and control. Each motor is attached to a hollow shaft that can rotate ±360° actuated by electric servos. Four of these propulsion shafts are configured in an orientation resembling a quad-copter, where the shafts are 90° apart. The other two propulsion shafts extrude perpendicular from each side of the plane of the quadcopter configuration. Under this unique configuration, Air-Ball is capable of decoupling the motion in the translational and rotational …
Numerical And Analytical Modelling For Droplet Evaporation Resulting In Convective Flow Cooling Verified By Experimentation, Adwaith Ravichandran
Numerical And Analytical Modelling For Droplet Evaporation Resulting In Convective Flow Cooling Verified By Experimentation, Adwaith Ravichandran
Theses and Dissertations
The temperature of a gaseous convective stream can be reduced by injecting a colder liquid into the stream. The extent to which this gas temperature can be reduced depends on the amount of liquid being injected into the gas flow domain, rate of energy transfer (heat) from the gas phase to the liquid resulting in evaporation and the length of the domain itself referred to in this study as a “mixer”. This study proposes the use of a non-dimensional Damkohler number that relates the liquid residence time and the liquid life time which could serve as a yardstick to determine …
Numerical Analysis Of A Compact Helical Counterflow Heat Exchanger, Manikandan Chidambaram
Numerical Analysis Of A Compact Helical Counterflow Heat Exchanger, Manikandan Chidambaram
Theses and Dissertations
The performance of compact counter flow heat exchangers with helically shaped passages is examined using a 1-D analytical model and compared with a high-fidelity 3-D numerical simulation. The 1-D model is capable of assessing the general trends associated with the heat transfer performance and fluid pressure losses, whereas the high fidelity 3-D numerical model is needed to provide more accuracy. For water flow rates of 0.01 kg/s -1 kg/s, the models are used to predict the overall heat transfer coefficient ratio for a straight and counter helix heat exchanger. The maximum difference between the 3-D numerical and 1-D analytical model …
Development Of A Static Aeroelastic Database Using Nastran Sol 144 For Aircraft Flight Loads Analysis From Conceptual Design Through Flight Test, Ryan M. Haughey
Development Of A Static Aeroelastic Database Using Nastran Sol 144 For Aircraft Flight Loads Analysis From Conceptual Design Through Flight Test, Ryan M. Haughey
Theses and Dissertations
This paper describes a method for predicting aircraft aerodynamic and inertial loading on a structural finite element model, (FEM) based on static aeroelastic coefficients. These coefficients are computed via interpolated spline methods within NASTRAN Solution 144 (static aeroelastic solution) and the “TRIM” module to connect the doublet-lattice model (DLM) and the structural finite element model for a coupled solution. The database is created by selecting key breakpoints where linear interpolation techniques can be utilized to develop and predict static aeroelastic coefficients for the prediction of any aircraft state for a given transient solution. This method is applicable from conceptual design …
Evaluation Of Augmented Reality Glasses For Use In Flight Test Courses, Leonardo Macena Silveira
Evaluation Of Augmented Reality Glasses For Use In Flight Test Courses, Leonardo Macena Silveira
Theses and Dissertations
The objective of this thesis research was to analyze the implementation of new technologies into the flight test engineering major courses at Florida Institute of Technology. The focus was to use current augmented reality technology available in the market and create ways the students would be able to use it while performing experiments. Augmented reality is not the same as virtual reality. It is a technology that generates computer images of effect into an existing reality. In easier words, augmented reality projects images into the real-life surroundings the user locates. It allows the user to interact with the computer while …
Evaluation Of High Velocity Wear, Armando Deleon
Evaluation Of High Velocity Wear, Armando Deleon
Theses and Dissertations
The HHSTT located at Holloman Air Force Base conducts hypersonic testing in a unique way. Rather than perform cost prohibitive flight testing or hypersonic wind tunnel testing, a rocket-powered sled propels test articles down a track. This test setup has been used to test at speeds up to 2885 m/s (~Mach 8.6). The sled is kept on the rails by utilizing slippers, fabricated to wrap around the rail [1]. This slipper design keeps the sled from separating from the rail during a test due to the airflow producing lift, in a designed effort to minimize the wear that occurs during …
Effects Of Manufacturing Process Variables On Ultrasonic Testing In Electron Beam Melted Ti-6al-4v, Andrew D. Durkee
Effects Of Manufacturing Process Variables On Ultrasonic Testing In Electron Beam Melted Ti-6al-4v, Andrew D. Durkee
Theses and Dissertations
Further research on validating additive manufacturing production quality is required before the realization of direct print-to-fly application of critical components. This research examines the response of ultrasonic testing as a function of various manufacturing variables in electron beam melted samples of Ti-6Al-4V. Four dimensionally identical blocks with 6 spherical voids at varying depths were manufactured using different combinations of stock powder, edge treatments, and void melting. Scans were completed on two sides of each specimen with the transducer focused on the mid-plane. Additionally, one specimen was scanned 6 times, with the focal plane adjusted for each scan to match the …
Human Optimization And Performance Enhancement In Flight Via Real-Time Biofeedback (Project Have Hope), Michael S. Fritts
Human Optimization And Performance Enhancement In Flight Via Real-Time Biofeedback (Project Have Hope), Michael S. Fritts
Theses and Dissertations
A four-phase, chronological, and build-up approach was implemented that commenced with basic hardware testing in a centrifuge and culminated in flights augmented by real-time biofeedback displays. A prototype Portable Electrocardiogram Unit (PECGU) was designed and proven to accurately measure heart rate (HR) and display percent heart rate reserve (%HRR). Results showed that %HRR was not a sole predictor of cognitive state. Cognitive responses indicated some correlation with %HRR, but were influenced by environment (centrifuge vs. flight). Subjective perceived exertion levels did not show statistically significant changes during test with biofeedback. A G-tracking task was evaluated during centrifuge and flight tests. …
Passive Load Testing For Evaluation Of Electromechanical Actuators, Jeremiah R. Hoffman
Passive Load Testing For Evaluation Of Electromechanical Actuators, Jeremiah R. Hoffman
Theses and Dissertations
While aircraft control surfaces traditionally use hydraulic actuators, electromechanical actuators (EMAs) are interesting as they have potential to be lighter, lower maintenance, and more robust. However, EMAs require more research regarding force-fight characteristics, power requirements, performance specifications, and more. The Air Force Research Laboratory is conducting some of this research, and operates a test rig which provides a passive load to a pair of EMAs. This rig is designed for simple test profiles for investigating force-fight; if it could be used to represent actual flight profiles, the rig could accommodate a wider variety of tests. The focus of this project …
Design, Buildup, And Testing Of A Radial Rotating Detonation Engine For A Compact Auxiliary Power Unit, Riley Huff
Design, Buildup, And Testing Of A Radial Rotating Detonation Engine For A Compact Auxiliary Power Unit, Riley Huff
Theses and Dissertations
Current power generators consume a large portion of the aircrafts usable volume and they are also extremely heavy for the amount of power that they can produce. Therefore, a need for compact, lightweight Auxiliary Power Units (APU) with high power density has arisen. A novel solution to this problem comes in the form of coupling a Rotating Detonation Engine (RDE) with a turbine generator. A new type of RDE referred to as the Radial Rotating Detonation Engine (RRDE) has been developed to fill this need. This project marks the first radial ow RDE successfully operated in the United States, and …
Wall-Modeled Large Eddy Simulation Of A Three-Dimensional Shock-Boundary Layer Interaction, Nicholas J. Marco
Wall-Modeled Large Eddy Simulation Of A Three-Dimensional Shock-Boundary Layer Interaction, Nicholas J. Marco
Theses and Dissertations
The direct simulation of turbulent flows is prohibitive at high Reynolds numbers; thus, methods such as RANS and LES are used. However, these methods still require a large number of cells near a solid boundary. To circumvent this issue, a Wall-Modeled Large Eddy Simulation (WM-LES) can be used. Of interest is how these wall models perform in comparison to a Wall-Resolved Large Eddy Simulation (WR-LES) and experimental results of a shock turbulent boundary layer interactions (STBLI) and specifically, whether equilibrium wall models are sufficient to resolve the oscillatory and hence non-equilibrium nature of these flows or whether a non-equilibrium model …
Creep Of Nextel 720/A Ceramic Matrix Composite With Laser Drilled Effusion Holes At 1200°C In Air And In Steam, Savannah N. Minor
Creep Of Nextel 720/A Ceramic Matrix Composite With Laser Drilled Effusion Holes At 1200°C In Air And In Steam, Savannah N. Minor
Theses and Dissertations
Creep behavior of an oxide-oxide ceramic matrix composite (CMC) containing an array of effusion holes was investigated at 1200⁰C in air and in steam. The composite (N720/A) consisted of a porous alumina matrix reinforced with alumina-mullite NextelTM 720 fibers. Test specimens had an array of 17 effusion holes with 0.5-mm diameter. The effusion holes were drilled through the specimen thickness normal to the specimen surface using a CO2 laser. Effect of the effusion holes on tensile properties was evaluated tension tests to failure at 1200°C in air. Creep of specimens with effusion holes at 1200°C was studied for creep stresses …
Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry
Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry
Theses and Dissertations
Refractory metal borides, commonly referred to as Ultra High Temperature Ceramics (UHTCs), exhibit a number of unique properties, such as extremely high melting temperature and hardness, chemical stability, high electrical and thermal conductivity and corrosion resistance. It has been demonstrated that the addition of SiC improves the oxidation resistance of ZrB2- and HfB2-based UHTCs above 1200°C by modifying the composition of the oxide scale. Addition of SiC retards the oxidation rate of ZrB2 and HfB2 by forming a protective layer of borosilicate glass. Creep deformation is one of the critical criterion for structural application of ceramics at elevated temperatures. Compression …
Design And Testing Of An Additively Manufactured Cubesat Structural Bus, Karson A. Roberts
Design And Testing Of An Additively Manufactured Cubesat Structural Bus, Karson A. Roberts
Theses and Dissertations
Recent innovations in additive manufacturing and design capabilities have opened the door for more opportunities to integrate multiple functions into a structural de- sign. Specifically, 3D printing through advanced laser powder bed fusion of metal powder allows for the development and integration of advanced structures that were previously unachievable. The demonstration of these techniques on a small satellite results in a structural bus consisting of various external and internal features, increasing its functionality and capabilities beyond simply providing structural support. 3D printing a multi-functional CubeSat bus with these integrated features such as internal lattices and wiring tabs demonstrates a new …
Parameter Study Of An Orbital Debris Defender Using Two Team, Three Player Differential Game Theory, David F. Spendel
Parameter Study Of An Orbital Debris Defender Using Two Team, Three Player Differential Game Theory, David F. Spendel
Theses and Dissertations
The United States Air Force and other national agencies rely on numerous space assets to project their doctrine. However, space is becoming an increasingly congested, contested, and competitive environment. A common risk mitigation strategy for the orbit debris problem is either performing evasive maneuvers, or placing additional shielding on the satellite before launch. Current risk mitigation strategies have significant consequences to satellite operators and may not produce sufficient risk mitigation. This research poses that an orbital debris defender, which would defend the primary satellite from orbital debris, may be a more effective risk mitigation strategy. By assuming the worst case …
Investigation Of Geometric And Thermal Scaling Effects On Simulated Turbine Vane Leading Edge Model, James G. Tewaheftewa
Investigation Of Geometric And Thermal Scaling Effects On Simulated Turbine Vane Leading Edge Model, James G. Tewaheftewa
Theses and Dissertations
Film cooling is still a bustling research topic, especially with burgeoning manufacturing techniques on the horizon that will open the design space. However, despite the number of years that have gone into gas turbine design and research, evaluating cooling performance on components still presents challenges. This task becomes especially difficult and dangerous if trying to do so in realistic engine conditions. Therefore, the majority of film cooling research is performed at conditions far from realistic engine conditions, often using materials that would never hold up to turbine inlet temperature, and scaled to predict results at engine conditions. Previous film cooling …
Tensile Properties And Fatigue Behavior Of Geopolymer Matrix Composites With Carbon Fiber Reinforcement At Elevated Temperature, Steffan M. L. Wilcox
Tensile Properties And Fatigue Behavior Of Geopolymer Matrix Composites With Carbon Fiber Reinforcement At Elevated Temperature, Steffan M. L. Wilcox
Theses and Dissertations
The tensile stress-strain and tension-tension fatigue of geopolymer matrix composites reinforced with 0/90 carbon fibers was investigated at 23 and 300°C in laboratory air. Geopolymers are inorganic polymeric materials composed of alumina, silica, and alkali metal oxides. Because geopolymers are synthesized as a fluid mixture or particles and liquid, they can be cast into a desired shape, and cured at only slightly elevated temperatures. The relative ease of synthesis and low processing temperatures make geopolymers an attractive choice as a matrix material for composite materials. Geopolymers also offer resistance to heat and oxidizing environments. Currently, geopolymer matrix composites are being …
Characterization And Analysis Of Plasma Instabilities In A 600 W Permanent Magnet Hall Thruster, Samuel D. Wright
Characterization And Analysis Of Plasma Instabilities In A 600 W Permanent Magnet Hall Thruster, Samuel D. Wright
Theses and Dissertations
Electric propulsion is an important technology for the future of space operations and exploration. Within the range of electric propulsion devices, Hall Effect Thrusters provide a balance of thrust and specific impulse well-suited for many Earth-centric missions. Hall Effect Thrusters have been studied since their development in the 1960s and have been flown on hundreds of spacecraft, but the intimate details of the plasma behavior within the thruster exhaust plume are still not well understood. Furthering this knowledge may be key to improving thruster design to yield better performance and longer lifetimes. To this end, experiments were conducted to measure …
Behavior Flexibility For Autonomous Unmanned Aerial Systems, Taylor B. Bodin
Behavior Flexibility For Autonomous Unmanned Aerial Systems, Taylor B. Bodin
Theses and Dissertations
Autonomous unmanned aerial systems (UAS) could supplement and eventually subsume a substantial portion of the mission set currently executed by remote pilots, making UAS more robust, responsive, and numerous than permitted by teleoperation alone. Unfortunately, the development of robust autonomous systems is difficult, costly, and time-consuming. Furthermore, the resulting systems often make little reuse of proven software components and offer limited adaptability for new tasks. This work presents a development platform for UAS which promotes behavioral flexibility. The platform incorporates the Unified Behavior Framework (a modular, extensible autonomy framework), the Robotic Operating System (a RSF), and PX4 (an open- source …
Modeling A Space-Based Quantum Link, Alexander W. Duchane
Modeling A Space-Based Quantum Link, Alexander W. Duchane
Theses and Dissertations
Quantum sources and single photon detectors have improved, allowing quantum algorithms for communication, encryption, computing, and sensing to transition from theory and small-scale laboratory experiments to field experiments. One such quantum algorithm, Quantum Key Distribution, uses optical pulses to generate shared random bit strings between two locations. These shared bit strings can be turned into encryption keys to be used as a one-time-pad or integrated with symmetric encryption techniques such as the Advanced Encryption Standard. This method of key generation and encryption is resistant to future advances in quantum computing which significantly degrade the effectiveness of current asymmetric key sharing …
An Exploration Of Error-Correcting Codes For Use In Noise-Prone Satellite Environments, Min W. Kang
An Exploration Of Error-Correcting Codes For Use In Noise-Prone Satellite Environments, Min W. Kang
Theses and Dissertations
Satellites are crucial for the modern world to function properly as they provide Global Navigation Satellite System (GNSS) and global communication. However, the data that is stored on these satellites can be corrupted by the radiation found in space, and its bits can be improperly flipped. In the past, Forward Error Correction (FEC) algorithms were selected based on their strength and implemented to correct these bit flips back to their original values. This thesis seeks to determine if the strength of the FEC algorithms Reed Solomon (RS) code and Reed Solomon Product Code (RSPC) directly translates to their effectiveness. These …
Stereo Vision: A Comparison Of Synthetic Imagery Vs. Real World Imagery For The Automated Aerial Refueling Problem, Nicholas J. Seydel
Stereo Vision: A Comparison Of Synthetic Imagery Vs. Real World Imagery For The Automated Aerial Refueling Problem, Nicholas J. Seydel
Theses and Dissertations
Missions using unmanned aerial vehicles have increased in the past decade. Currently, there is no way to refuel these aircraft. Accomplishing automated aerial refueling can be made possible using the stereo vision system on a tanker. Real world experiments for the automated aerial refueling problem are expensive and time consuming. Currently, simulations performed in a virtual world have shown promising results using computer vision. It is possible to use the virtual world as a substitute environment for the real world. This research compares the performance of stereo vision algorithms on synthetic and real world imagery.
Integrity Monitoring For Automated Aerial Refueling: A Stereo Vision Approach, Thomas R. Stuart
Integrity Monitoring For Automated Aerial Refueling: A Stereo Vision Approach, Thomas R. Stuart
Theses and Dissertations
Unmanned aerial vehicles (UAVs) increasingly require the capability to y autonomously in close formation including to facilitate automated aerial refueling (AAR). The availability of relative navigation measurements and navigation integrity are essential to autonomous relative navigation. Due to the potential non-availability of the global positioning system (GPS) during military operations, it is highly desirable that relative navigation can be accomplished without the use of GPS. This paper develops two algorithms designed to provide relative navigation measurements solely from a stereo image pair. These algorithms were developed and analyzed in the context of AAR using a stereo camera system modeling that …
Design And Test Of A Uav Swarm Architecture Over A Mesh Ad-Hoc Network, Timothy J. Allen
Design And Test Of A Uav Swarm Architecture Over A Mesh Ad-Hoc Network, Timothy J. Allen
Theses and Dissertations
The purpose of this research was to develop a testable swarm architecture such that the swarm of UAVs collaborate as a team rather than acting as several independent vehicles. Commercial-off-the-shelf (COTS) components were used as they were low-cost, readily available, and previously proven to work with at least two networked UAVs. Initial testing was performed via software-in-the-loop (SITL) demonstrating swarming of three simulated multirotor aircraft, then transitioned to real hardware. The architecture was then tested in an outdoor nylon netting enclosure. Command and control (C2) was provided by software implementing an enhanced version of Reynolds’ flocking rules via an onboard …
Stabilized Rpa Flight In Building Proximity Operations, Michael M. Kaniut
Stabilized Rpa Flight In Building Proximity Operations, Michael M. Kaniut
Theses and Dissertations
The thesis seeks a solution to the requirement for a highly reliable and capable Unmanned Air Vehicle (UAV) to support a wide array of missions and applications that require close proximity flight to structures. The scope of the project includes the drafting of a concept of operations (CONOPs) describing how the mission requirements might be met using the sensor, operators, and air vehicle described here in. The demonstration of the wall-following section of that CONOPs is performed by cart testing a custom algorithm and evaluating its ability to react to its environment. Finally, a flight test was performed to characterize …
Military Application Of Aerial Photogrammetry Mapping Assisted By Small Unmanned Air Vehicles, Kijun Lee
Military Application Of Aerial Photogrammetry Mapping Assisted By Small Unmanned Air Vehicles, Kijun Lee
Theses and Dissertations
This research investigated the practical military applications of the photogrammetric methods using remote sensing assisted by small unmanned aerial vehicles (SUAVs). The research explored the feasibility of UAV aerial mapping in terms of the specific military purposes, focusing on the geolocational and measurement accuracy of the digital models, and image processing time. The research method involved experimental flight tests using low-cost Commercial off-the-shelf (COTS) components, sensors and image processing tools to study key features of the method required in military like location accuracy, time estimation, and measurement capability. Based on the results of the data analysis, two military applications are …
Pseudo Linear Hall Effect Thruster Characterization Through Potential, Magnetic, And Optical Measurements, Braeden A. Sheets
Pseudo Linear Hall Effect Thruster Characterization Through Potential, Magnetic, And Optical Measurements, Braeden A. Sheets
Theses and Dissertations
Electric propulsion systems are a more mass efficient method for providing a change in velocity, ΔV, to on-orbit spacecraft, than their chemical counterparts. In comparison, electric systems generally have a much higher specific impulse, Isp, than chemical systems. One option within the realm of electric propulsion is Hall Effect Thrusters, which have moderately high specific impulse values. From their advent in the 1960s, Hall Effect Thrusters have been used for orbit station keeping, attitude control, and orbit transfer. Although the discharge cavity is conventionally circular, pseudo-linear or racetrack shaped cavities have been developed. Even though Hall thrusters have decades of …
Optimal Trajectory Generation In A Dynamic Multi-Body Environment Using A Pseudospectral Method, Jacob A. Dahlke
Optimal Trajectory Generation In A Dynamic Multi-Body Environment Using A Pseudospectral Method, Jacob A. Dahlke
Theses and Dissertations
High-altitude parking orbits could provide resiliency to the military space infrastructure by providing redundancy in key assets, allowing for rapid reconstitution of underperforming satellites. When analyzing trajectories in a high-altitude regime, two-body models of Keplerian motion become less accurate since the gravitational effects of other bodies are no longer negligible. To provide a higher fidelity model of the dynamics in a high-altitude regime, a multiple-body model can be used. In the Earth-Moon system, a spacecraft operating in the high-altitude regime can be modeled with three-body dynamics. With certain simplifying assumptions, the model is called the circular-restricted three-body problem (CR3BP). The …
Control, Characterization, And Cooling Of An Ultra-Compact Combustor, Kevin J. Demarco
Control, Characterization, And Cooling Of An Ultra-Compact Combustor, Kevin J. Demarco
Theses and Dissertations
An Ultra-Compact Combustor (UCC) is novel alternative to axial flow combustors commonly used in gas turbine engines. The UCC offers multiple benefits to engine design. First, the UCC aims to increase the thrust-to-weight ratio of an aircraft gas turbine engine by decreasing the size, and thus weight, of the engine's combustor. This is done by utilizing a Circumferential Cavity (CC) wrapped around the main core flow which hosts the combustion event, allowing a shortened combustor length. Second, within the CC, the combusting mixture is subjected to a high centrifugal loading which aids combustion by improving both flame propagation and residence …
Analytical Determination Of A Helicopter Height Velocity Diagram, Michael J. Harris
Analytical Determination Of A Helicopter Height Velocity Diagram, Michael J. Harris
Theses and Dissertations
A helicopter height velocity (HV) diagram was analytically constructed using optimal control techniques. A three degree of freedom, point-mass, dynamic model was developed and validated with flight test data. An induced velocity calculation was incorporated which addressed the effects of vortex ring state. The problem was posed as an open final time, constrained initial state, constrained final state problem, with the objective function as a weighted sum of the initial altitude and quadratic controls. This formulation was solved using direct pseudo-spectral collocation and adaptive mesh refinement as implemented by the GPOPS-II® software suite. Proper adjustment of path constraints was crucial …