Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Keyword
-
- Additive manufacturing (4)
- Ceramic matrix composite (3)
- Computational fluid dynamics (3)
- Electric propulsion (3)
- UAV (3)
-
- #antcenter (2)
- 3D printing (2)
- Computer vision (2)
- Creep (2)
- Film cooling (2)
- Finite element analysis (2)
- Gas turbines (2)
- Optimization (2)
- Path planning (2)
- Space debris (2)
- UAS (2)
- 3-D modeling (1)
- Ablation (1)
- Abnormal grain growth (1)
- Ad-hoc network (1)
- Adaptive nulling (1)
- Adiabatic effectiveness (1)
- Advective capacity ratio (1)
- Aerial Port of the Future (1)
- Aerial refueling (1)
- Aerospace Industry (1)
- Aerospace structures (1)
- Alternative Decisions (1)
- Angular Spectrum Propagation (1)
- Assessment (1)
Articles 1 - 30 of 79
Full-Text Articles in Entire DC Network
Carbon Nanotube Fibers: Mechanical Behavior And The Effects Of The Space Environment, Ryan A. Kemnitz
Carbon Nanotube Fibers: Mechanical Behavior And The Effects Of The Space Environment, Ryan A. Kemnitz
Theses and Dissertations
Carbon nanotube materials are promising multifunctional materials for incorporation into aerospace structures because of their high tensile strength, high electrical conductivity, and low density. This research aimed to characterize the mechanical failure mechanisms of carbon nanotube fibers and examine the effects of the space environment on their material properties. Tensile tests were conducted at varying strain rates and on fibers of varying gage lengths to examine the underlying molecular failure mechanisms and impact of defects on fiber strength. Tensile strength and elastic modulus were observed to increase with increasing strain rate and decrease with increasing gage lengths. The observed effects …
Thermal Management Of Satellite Electronics Via Gallium Phase Change Heat Sink Devices, Brian O. Palmer
Thermal Management Of Satellite Electronics Via Gallium Phase Change Heat Sink Devices, Brian O. Palmer
Theses and Dissertations
The purpose of this research was to determine the effectiveness and feasibility of additively manufactured heat sinks using gallium as a phase change material in the thermal management of satellite electronics. A design was created based on the footprint of an Astronautical Development, LLC Lithium 1 UHF radio and six heat sinks were additively manufactured; two each of stainless steel 316, Inconel 718, and ULTEM 9085. Each heat sink was filled with gallium for testing purposes. Models were created to simulate the behavior of the heat transfer and phase change processes occurring within the heat sink. Additionally, laboratory data was …
Experimental And Computational Analysis Of The Interaction Of Carbon And Silicon Ablation Products In Expanding Hypersonic Flows, Brian E. Donegan
Experimental And Computational Analysis Of The Interaction Of Carbon And Silicon Ablation Products In Expanding Hypersonic Flows, Brian E. Donegan
Theses and Dissertations
Thermal protection is required for vehicles entering planetary atmospheres to protect against the severe heating loads experienced. Characterization of candidate materials is often done utilizing plasma or arc-jet facilities, which provide steady-state testing of the thermal environments experienced during hypersonic flight, but do not correctly simulate hypersonic flowfields. Conversely, impulse facilities can reproduce flight velocities and enthalpies but have extremely short test times, prohibiting testing of thermal response. Modeling ablation and heating rates, particularly in the wake region, remains a significant challenge due to the complexity of the flowfield. To better understand this complex phenomenon and provide data to validate …
Free Response And Trim Force Requirements For Aircraft Configuration Changes, Marvin Toepfer
Free Response And Trim Force Requirements For Aircraft Configuration Changes, Marvin Toepfer
Theses and Dissertations
As an FAA Commercial Pilot and Flight Instructor, one comes in contact with many different types of experiences and abnormal situations. A widely known cause of fatal accidents in the general aviation industry, and also currently listed on the National Transportation Safety Board Most Wanted List, is the loss of control in the traffic pattern [1]. For many years now, different departments of the FAA and Department of Transportation, such as the FAA Small Airplane Directorate, have been trying to mitigate the risks and causes associated with the loss of control in the traffic pattern. Due to technological advancements and …
Aerodynamic Model Of The Piper Warrior Ii Based On Flight Test Data, Nicholas Casciola
Aerodynamic Model Of The Piper Warrior Ii Based On Flight Test Data, Nicholas Casciola
Theses and Dissertations
Aerodynamic modeling is an important part of aircraft design and of aircraft testing. Generally, this is done through CFD models and Wind Tunnel tests prior to the aircrafts first flight but building the models using flight test data is also very important. It is used to verify theoretical models generated from the computer and wind tunnel tests. They are also useful for building simulators, particularly those in modeling and analyzing airport traffic patterns. These tests used a Piper Pa-28-161 Warrior II owned by the Florida Tech Flight Test Engineering program. It has a 160hp Lycoming engine. The test pilot was …
Effect Of Film Cooling Hole Size On A Turbine Rotor Blade, Klint Martis
Effect Of Film Cooling Hole Size On A Turbine Rotor Blade, Klint Martis
Theses and Dissertations
The objective of this study was to evaluate the effect of the cooling hole size on the adiabatic film cooling effectiveness over a rotating turbine blade section. The study was conducted using ANSYS FLUENT to determine the adiabatic wall temperature over the blade surface. The geometry was created to be a single section of a turbine rotating at 4000 rpm, and the blade increases in camber from tip to hub. Cylindrical cooling holes were created and the diameters were varied from 0.5 mm to 1.5 mm. The pitch-to-diameter ratio and the length-to-diameter ratio were kept constant at a value of …
Cubesat Docking And Resource Sharing Mechanism, Shingo Kunito
Cubesat Docking And Resource Sharing Mechanism, Shingo Kunito
Theses and Dissertations
This thesis addresses the design concept of a CubeSat docking and resource sharing mechanism that allows to transfer propellant that is pressurized gas, data, and power. In docking and capture design, the interface is equipped with two air cylinders that are rated up to 20.68 MPa internal pressure generating the ideal force of 1218.4 N each. With the designed air cylinder and mounted configuration, the maximum capture distance between the target and the chaser CubeSat is 40.30 mm. Since air cylinder and body frame are designed specifically for this interface, structural analysis was conducted in ANSYS where results show a …
Quantitative Measurement Techniques For Vibration And Buffet, Edward Thomas Meyer
Quantitative Measurement Techniques For Vibration And Buffet, Edward Thomas Meyer
Theses and Dissertations
This paper outlines a proposed parameter for measurement of vibration and buffet in vehicles. It is intended to be used where applicable in lieu of raw accelerometer data or qualitative comments to measure ride quality, quantify vibration levels, and aid in certification matters. In flight vehicle applications which employ fly-by wire flight control systems with closed loop and variable gain control laws, the phenomenon of buffet in its various forms is becoming somewhat specious as an aircrew cue in relation to the stability and control of flight vehicles. In these applications, stability and control throughout the operating envelope is designed …
Development Of Adaptable Human-Machine Interface For Teleoperation Over Time Delay, May Nyein Chan
Development Of Adaptable Human-Machine Interface For Teleoperation Over Time Delay, May Nyein Chan
Theses and Dissertations
The Adaptable Human-Machine Interface (AHMI) was developed for the Orbital Robotic Interaction, On-orbit servicing, and Navigation (ORION) Laboratory of the Florida Institute of Technology. The primary project objective was to develop and test a predictive display for mitigating the effects of time delay in teleoperation of space robots and Unmanned Aerial Vehicles (UAV) using quadcopters as a test case. Regardless of the increasing popularity of various autonomous systems, research and development of teleoperating system should not be neglected since it is often utilized as a back-up in most autonomous systems especially in systems for human spaceflight and UAV operations in …
Control Development For Autonomous Landing Of Quadcopter On Moving Platform, Rakhayai Mangsatabam
Control Development For Autonomous Landing Of Quadcopter On Moving Platform, Rakhayai Mangsatabam
Theses and Dissertations
This thesis focuses on the control development for autonomous landing of a quadcopter on a moving platform. The object tracking and path following is performed through on-board vision-based systems. The goal of the thesis is to develop a controller for autonomous landing of a quadcopter and test its fidelity with simulations and experiments. The thesis is carried out in two sections, simulation and experiment. The simulation was carried out based on the system modeled and a PD (Proportional Derivative) controller was used to simulate the quadcopter landing. The simulation was split into three parts, with each part attempting to become …
Comparing Specific Excess Power Of General Aviation Aircraft, Yohan Forbes Auguste
Comparing Specific Excess Power Of General Aviation Aircraft, Yohan Forbes Auguste
Theses and Dissertations
The high number of Loss of Control and Controlled Flight into Terrain Accidents in General Aviation (GA) suggests that there is a lack of understanding and recognition of low energy states by pilots of GA aircraft. As a result there is a desire to implement an energy management system in GA aircraft to alert the pilot of low energy conditions and to give the required corrective action to get to a desired energy state. This requires an understanding of the performance capabilities of GA aircraft in terms of their ability to change their energy state. The ability to change the …
Investigation Of The Mechanical Behavior Of Non-Conventional Laminates: Anisotropy Of Tensile Strength In Coupons With Quasi-Isotropic Stiffness Characteristics, Israel Oluwatunmise Ayodele
Investigation Of The Mechanical Behavior Of Non-Conventional Laminates: Anisotropy Of Tensile Strength In Coupons With Quasi-Isotropic Stiffness Characteristics, Israel Oluwatunmise Ayodele
Theses and Dissertations
Advanced composites have emerged as viable structural solutions over the years and have therefore become implemented in several applications, notably aerospace structures. In modern aircraft structures, they have been gradually introduced to both secondary and primary components. Laminated composites used in such applications have generally been restricted to those with straight fibers, that are aligned to only a handful of pre-selected fiber orientations; 0˚, 45˚, 90˚ and -45˚. Recent advances in the technology of laminated composites have however indicated the possibility to harness significantly higher structural gains by allowing the use of other fiber orientations, and even implementing curvilinear fibers …
Reconstruction Of The 3d Temperature And Species Concentration Spatial Distribution Of A Jet Engine Exhaust Plume Using An Infrared Fourier Transform Spectrometer Hyperspectral Imager, Mason D. Paulec
Theses and Dissertations
The measurement of combustion byproducts is useful for determining pollution of any fuel burning application, efficiency of combustion, and determining detectability of aircraft exhausts. Both intrusive and non-intrusive techniques have been utilized to measure these quantities. For the majority of the non-intrusive techniques, the absorption and emission spectra of the gases are utilized for measurements. For this research, the use of the Telops Infrared Fourier Transform Spectrometer (IFTS) Hyperspectral Imager (HSI) was explored within the scope of combustion diagnostic methods, as an option for remote measurements of a jet turbine to determine concentration of species and temperature of the combustion …
A Heuristic Method For Task Selection In Persistent Isr Missions Using Autonomous Unmanned Aerial Vehicles, Christopher C. Olsen
A Heuristic Method For Task Selection In Persistent Isr Missions Using Autonomous Unmanned Aerial Vehicles, Christopher C. Olsen
Theses and Dissertations
The Persistent Intelligence, Surveillance, and Reconnaissance (PISR) problem seeks to provide timely collection and delivery of data from prioritized ISR tasks using an autonomous Unmanned Aerial Vehicle (UAV). In the literature, PISR is classified as a type of Vehicle Routing Problem (VRP), often called by other names such as persistent monitoring, persistent surveillance, and patrolling. The objective of PISR is to minimize the weighted revisit time to each task (called weighted latency) using an optimal task selection algorithm. In this research, we utilize the average weighted latency as our performance metric and investigate a method for task selection called the …
Application Of Spectral Solution And Neural Network Techniques In Plasma Modeling For Electric Propulsion, Joseph R. Whitman
Application Of Spectral Solution And Neural Network Techniques In Plasma Modeling For Electric Propulsion, Joseph R. Whitman
Theses and Dissertations
A solver for Poisson's equation was developed using the Radix-2 FFT method first invented by Carl Friedrich Gauss. Its performance was characterized using simulated data and identical boundary conditions to those found in a Hall Effect Thruster. The characterization showed errors below machine-zero with noise-free data, and above 20% noise-to-signal strength, the error increased linearly with the noise. This solver can be implemented into AFRL's plasma simulator, the Thermophysics Universal Research Framework (TURF) and used to quickly and accurately compute the electric field based on charge distributions. The validity of a machine learning approach and data-based complex system modeling approach …
Navigation With Artificial Neural Networks, Joseph A. Curro Ii
Navigation With Artificial Neural Networks, Joseph A. Curro Ii
Theses and Dissertations
The objective of this dissertation is to explore the applications for Artificial Neural Networks (ANNs) in the field of Navigation. The state of the art for ANNs has improved significantly so now they can rival and even surpass humans in problems once thought impossible. We present different methods to augment, combine, or replace existing Navigation filters with ANN. The main focus of these methods is to use as much existing knowledge as possible then use ANNs to extend the current knowledge base. Next, improvements are made for a class of Artificial Neural Network (ANN)s which provide covariance called Mixture Density …
Satellite Articulation Sensing Using Computer Vision, David H. Curtis
Satellite Articulation Sensing Using Computer Vision, David H. Curtis
Theses and Dissertations
Autonomous on-orbit satellite servicing benefits from an inspector satellite that can gain as much information as possible about the primary satellite. This includes performance of articulated objects such as solar arrays, antennas, and sensors. A method for building an articulated model from monocular imagery using tracked feature points and the known relative inspection route is developed. Two methods are also developed for tracking the articulation of a satellite in real-time given an articulated model using both tracked feature points and image silhouettes. Performance is evaluated for multiple inspection routes and the effect of inspection route noise is assessed. Additionally, a …
Three-Dimensional Wall Effects In A Scramjet Cavity Flameholder, Evan P. Oren
Three-Dimensional Wall Effects In A Scramjet Cavity Flameholder, Evan P. Oren
Theses and Dissertations
Scramjets, or supersonic combustion ramjets, are a key component for the development of powered hypersonic vehicles. The flameholding strategy used in this engine creates a recirculation region by creating a cavity in one side of the combustor. This highly unsteady region is difficult to interrogate through conventional means. A novel optical observation technique called hyperspectral imaging has been developed to examine the scramjet combustion chamber. The hyperspectral camera is capable of generating an interferogram at hundreds to thousands of wavelengths. These data are integrated across the line-of-sight with no information on three-dimensional (3D) location of origin. A model must be …
Investigation Of A Pressure Wave Supercharger For An Industrial Diesel Engine, Brian A. Beasley
Investigation Of A Pressure Wave Supercharger For An Industrial Diesel Engine, Brian A. Beasley
Theses and Dissertations
Internal combustion engines suffer from decreased performance as altitude is in- creased. This performance decrease can be overcome by increasing the pressure in the engine's intake manifold. Typically, this is accomplished with a turbocharger or supercharger. However, mechanical compression devices such as these suffer from decrease compression efficiency as the size of the device decreases. The size of the compression device scales with the amount of mass ow through the device, and the amount of mass ow is proportional to the size of the engine. This means a small turbocharger for a small engine is less efficient than a larger …
Thermochemical Non-Equilibrium Models For Weakly Ionized Hypersonic Flows With Application To Slender-Body Wakes, Matthew P. Clarey
Thermochemical Non-Equilibrium Models For Weakly Ionized Hypersonic Flows With Application To Slender-Body Wakes, Matthew P. Clarey
Theses and Dissertations
The current resurgence of interest in hypersonic technologies has warranted an inquiry into the commonly employed thermochemical non-equilibrium models within computational fluid dynamic (CFD) simulations. Additionally, research has historically focused on forebody flowfields, while studies of the complex wake structure have remained elusive. Although the forebody is of significance for vehicle analysis, the wake presents many exploitative characteristics. This dissertation aimed to address these two deficits. First, two three-temperature non-equilibrium models were developed, increasing the fidelity of hypersonic solutions above that of the legacy two-temperature model. The models were then investigated via zero-dimensional simulations, to detail the non-equilibrium processes, and …
Simplex Control Methods For Robust Convergence Of Small Unmanned Aircraft Flight Trajectories In The Constrained Urban Environment, Michael D. Zollars
Simplex Control Methods For Robust Convergence Of Small Unmanned Aircraft Flight Trajectories In The Constrained Urban Environment, Michael D. Zollars
Theses and Dissertations
Constrained optimal control problems for Small Unmanned Aircraft Systems (SUAS) have long suffered from excessive computation times caused by a combination of constraint modeling techniques, the quality of the initial path solution provided to the optimal control solver, and improperly defining the bounds on system state variables, ultimately preventing implementation into real-time, on-board systems. In this research, a new hybrid approach is examined for real-time path planning of SUAS. During autonomous flight, a SUAS is tasked to traverse from one target region to a second target region while avoiding hard constraints consisting of building structures of an urban environment. Feasible …
Optimal Finite Thrust Guidance Methods For Constrained Satellite Proximity Operations Inspection Maneuvers, Eric R. Prince
Optimal Finite Thrust Guidance Methods For Constrained Satellite Proximity Operations Inspection Maneuvers, Eric R. Prince
Theses and Dissertations
Algorithms are developed to find optimal guidance for an inspector satellite operating nearby a resident space object (RSO). For a non-maneuvering RSO, methods are first developed for a satellite subject to maximum slew rates to conduct an initial inspection of an RSO, where the control variables include the throttle level and direction of the thrust. Second, methods are developed to optimally maneuver a satellite with on/off thrusters into a natural motion circumnavigation or teardrop trajectory, subject to lighting and collision constraints. It is shown that for on/off thrusters, a control sequence can be parameterized to a relatively small amount of …
Self-Assembly Of Protein Fibrils In Microgravity, Dylan Bell
Self-Assembly Of Protein Fibrils In Microgravity, Dylan Bell
Theses and Dissertations
Deposits of insoluble protein fibrils in human tissue are associated with amyloidosis and neurodegenerative diseases. Different proteins are involved in each disease; all are soluble in their native conformation in vivo, but by molecular self-assembly, they all form insoluble protein fibril deposits with a similar cross -sheet structure. The study of molecular self-assembly is also of interest to origin of life. The development of cellular activity was dependent upon the creation of large complex molecular structures in the chemical and environmental conditions present when life originated. Although life probably arose in a planetary environment, microgravity is known to effect cellular …
Control Laws For Autonomous Landing On Pitching Decks, Kendrick Buchala
Control Laws For Autonomous Landing On Pitching Decks, Kendrick Buchala
Theses and Dissertations
This thesis addresses the problem of landing a quadcopter onto the pitching deck of a ship, as a partial simulation of a shipboard landing during high seas. The deck is modeled to pitch with a sinusoidal motion. While shipboard landing consists of many stages, only the final landing is simulated in this research. Other ship motions, such as roll and heave, are likewise not considered. The goal is to land the quadcopter in the center of the deck with minimal position and pitch error, where position error measures how far fore or aft of the center of the landing pad …
Dynamics Of Spacecraft Orbital Refueling, Casey Clark
Dynamics Of Spacecraft Orbital Refueling, Casey Clark
Theses and Dissertations
A quantitative collation of relevant parameters for successfully completed experimental on-orbit fluid transfers and anticipated orbital refueling future missions is performed. The dynamics of connected satellites sustaining fuel transfer are derived by treating the connected spacecraft as a rigid body and including an internal mass flow rate. An orbital refueling results in a time-varying local center of mass related to the connected spacecraft. This is accounted for by incorporating a constant mass flow rate in the inertia tensor. Simulations of the equations of motion are performed using the values of the parameters of authentic missions in an endeavor to provide …
Direct Numerical Simulations Of Incompressible Flow Through Porous Packs Over A Wide Range Of Reynolds Numbers, Antoine Michael Diego Jost
Direct Numerical Simulations Of Incompressible Flow Through Porous Packs Over A Wide Range Of Reynolds Numbers, Antoine Michael Diego Jost
Theses and Dissertations
Direct numerical simulations of incompressible flow through periodic square/rectangular (two-dimensional; 2-D) and cubic (three-dimensional; 3-D) arrays of particles and periodic random packs of polydisperse spheres over a wide range of Reynolds numbers and at various porosities are performed. The unsteady Navier- Stokes equations are solved with either a 3-D parallel finite-difference (FD) inhouse research code on a collocated Cartesian grid and with an immersed boundary method (IBM) to treat the internal boundaries, or with the finite-volume (FV) solver OpenFOAM R⃝ on an unstructured grid and with an explicit treatment of the boundaries. The FD explicit solver is used for 2-D …
Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1100°C In Air And In Silicic Acid-Saturated Steam, Logan M. Gumucio
Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1100°C In Air And In Silicic Acid-Saturated Steam, Logan M. Gumucio
Theses and Dissertations
Innovations in SiC based ceramic matrix composites (CMCs) have yielded exceptional high-temperature properties and performance in aggressive oxidizing environments. These material characteristics provide potential avenues for future advancements in many applications where current metallic alloys perform near their operating temperature limits in a harsh environment. As steam (typically present in these environments) enters through cracks in the matrix of a SiC/SiC composite, it leaches Si and becomes saturated with silicic acid, Si(OH)4, prior to attacking the reinforcing SiC fibers. Therefore, it is paramount that a thorough understanding of the performance and durability of SiC fibers be obtained under …
Mitigating Interference With Knowledge-Aided Subarray Pattern Synthesis And Space Time Adaptive Processing, Yongjun Yoon
Mitigating Interference With Knowledge-Aided Subarray Pattern Synthesis And Space Time Adaptive Processing, Yongjun Yoon
Theses and Dissertations
Phased arrays are essential to airborne ground moving target indication (GMTI), as they measure the spatial angle-of-arrival of the target, clutter, and interference signals. The spatial and Doppler (temporal) frequency is utilized by space-time adaptive processing (STAP) to separate and filter out the interference from the moving target returns. Achieving acceptable airborne GMTI performance often requires fairly large arrays, but the size, weight and power (SWAP) requirements, cost and complexity considerations often result in the use of subarrays. This yields an acceptable balance between cost and performance while lowering the system’s robustness to interference. This thesis proposes the use of …
Impact Load Identification Using Optimal Sensor Placement And Model Reduction, Bella Jackson Chembakassery
Impact Load Identification Using Optimal Sensor Placement And Model Reduction, Bella Jackson Chembakassery
Theses and Dissertations
Any structure which is used in service can be subjected to different kinds of loads such as static, dynamic, moving or impact loads. It is very much necessary such structures are reliable and robust enough to be used for service. Hence accurately estimating the load acting on the structure is very important. In case of impact loading, it is very difficult to estimate the load because it acts for a short period of time. For such loading, the structural response of the system can be used as a medium to estimate the applied load. The structural response used could be …
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 …