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- #antcenter (3)
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- Airfoil (1)
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- Automated Aerial Refueling (1)
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- Finite element method (1)
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- Hafnium diboride (1)
- Hall Effect (1)
- Hall thruster spectra (1)
- HfB2 (1)
Articles 1 - 30 of 33
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Flight Testing Angle-Of-Attack Warning Combinations On Part 23 Aircraft, Jennifer Grey Geehan
Flight Testing Angle-Of-Attack Warning Combinations On Part 23 Aircraft, Jennifer Grey Geehan
Theses and Dissertations
The high number of accidents involving General Aviation (GA) aircraft leads to a need for improved methods to warn pilots of high angles of attack (AOA) and impending stall. Such methods must be certified by the Federal Aviation Administration (FAA) under Federal Aviation Regulations Part 23 regarding their effectiveness in preventing departures from controlled flight. Therefore, methods of compliance must be developed to certify Part 23 aircraft equipped with AOA warning or limiting systems. The research objectives were to (a) determine methods for the evaluation of AOA warning and limiting systems and to (b) evaluate the effectiveness of baseline combinations …
Sensitivity Of Facial Organs Of Pythons As Deduced By Radiation Heat Transfer Analysis Under Varying Environmental Conditions, Rama Wairagkar
Sensitivity Of Facial Organs Of Pythons As Deduced By Radiation Heat Transfer Analysis Under Varying Environmental Conditions, Rama Wairagkar
Theses and Dissertations
Predicting the behavior of snakes has been an interest to several scientists for the last few decades. Even though considerable amount of research has been carried out pertaining to snakes, there remains a degree of curiosity regarding their striking ability, live prey detection at locations where visual clues are unobtainable, thermosensation and the phenomena that drives these conducts. Researches carried out so far have moderately disregarded the perception of sensitivity of facial pits of snakes and its characteristics under contrasting temperature domains. This thesis attempts to undertake a computational analysis of the sensitivity of facial pits of Burmese pythons under …
System Study Of An On-Orbit Additive Manufacturing Cubesat, Juliette Isabelle Bido
System Study Of An On-Orbit Additive Manufacturing Cubesat, Juliette Isabelle Bido
Theses and Dissertations
The AddCube mission aims to demonstrate additive manufacturing technology in microgravity on a CubeSat platform by 3D-printing a 1-meter long rectangular beam on orbit. To accomplish this task, Made In Space Inc. (MIS) will provide the Extended Structure Additive Manufacturing Machine – CubeSat (ESAMM-C) payload. The high power required by the ESAMM-C payload creates a complex thermal problem within the spacecraft due to tight volume constraints associated with CubeSats. To cope with this problem, an in depth worst-case thermal analysis of the integrated spacecraft is conducted and an appropriate thermal management system for the mission is designed. Temperature regulation is …
Holistic Methodology For Stochastic Space Mission Utility Analysis, Ja'mar Alexander Watson
Holistic Methodology For Stochastic Space Mission Utility Analysis, Ja'mar Alexander Watson
Theses and Dissertations
Analysis and design mechanisms have a profound effect on space missions; yet, space mission engineering is a discipline without unanimous definition and implementation. Current philosophies are inadequate due to incomplete mission phasespaces, disaggregated design methods, exclusion of constitutive relations, curtailed tradespace exploration, and unsubstantiated mission concept solutions. This dissertation presents a new paradigm for simultaneously developing, exploring, and assessing statistically validated space mission concepts. Stochastic modeling and simulation, providing multivariate mission utility analysis with concurrently integrated tradespace exploration, risk assessment, and holistic design, facilitates the methodology. Backtesting of the Apollo II-17 crewed missions to the Moon and retrodiction of Martian …
Characterization And Scaling Study Of Energy Pathways In Small Four-Stroke Internal Combustion Engines, Jason R. Blantin
Characterization And Scaling Study Of Energy Pathways In Small Four-Stroke Internal Combustion Engines, Jason R. Blantin
Theses and Dissertations
A study of the efficiency and energy losses of a selection of five small (40 - 200 cm3 displacement) single cylinder, four-stroke engines was accomplished. The study was performed as part of a larger effort to improve the range and endurance of small internal combustion engines (ICE) that power Group II Unmanned Aerial Vehicles (UAVs). Little is known about the performance, efficiency, and allocation of energy losses for four-stroke ICEs in this size range. The goal of the study was to characterize these parameters for use in future research efforts. Three research objectives were developed to guide the study …
Satellite Propulsion Spectral Signature Detection And Analysis For Space Situational Awareness Using Small Telescopes, Pamela L. Wheeler
Satellite Propulsion Spectral Signature Detection And Analysis For Space Situational Awareness Using Small Telescopes, Pamela L. Wheeler
Theses and Dissertations
Safe satellite operations are of utmost importance. Maintaining precise orbital maintenance places stringent performance requirements on current propulsion systems, which are often electric propulsion systems. Electron temperature is a commonly used diagnostic to determine the performance of a Hall thruster, and recent work has correlated near infrared (NIR) spectral measurements of ionization lines of xenon and krypton to electron temperature measurements. In the research herein, appropriate line spectra ratios are identified for each propellant type when used with remote space-to-ground observations. NIR plume emissions were used to characterize a 600 Watt Hall thruster for a variety of observation angles and …
Optimal Control Methods For Missile Evasion, Ryan W. Carr
Optimal Control Methods For Missile Evasion, Ryan W. Carr
Theses and Dissertations
Optimal control theory is applied to the study of missile evasion, particularly in the case of a single pursuing missile versus a single evading aircraft. It is proposed to divide the evasion problem into two phases, where the primary considerations are energy and maneuverability, respectively. Traditional evasion tactics are well documented for use in the maneuverability phase. To represent the first phase dominated by energy management, the optimal control problem may be posed in two ways, as a fixed final time problem with the objective of maximizing the final distance between the evader and pursuer, and as a free final …
Analysis Of An Experimental Space Debris Removal Mission, Krista L.L. Roth
Analysis Of An Experimental Space Debris Removal Mission, Krista L.L. Roth
Theses and Dissertations
Encountering space debris is an ever-increasing problem in space exploration and exploitation, especially in Low Earth Orbit. While many space-faring governing bodies have attempted to control the orbital lifetime post mission completion of satellites and rocker bodies, objects already in orbit pose a danger to future mission planning. Currently, governments and academic institutions are working to develop missions to remove space debris; however, the proposed missions are typically costly primary missions. This research proposes an alternative to use an upper stage rocket, to be called a chaser, already launching a primary mission near the desired debris as a host for …
Design Of A Compact Helical Counterflow Heat Exchanger, Aravindakshan Thirumalai Ananthanpillai
Design Of A Compact Helical Counterflow Heat Exchanger, Aravindakshan Thirumalai Ananthanpillai
Theses and Dissertations
Compact heat exchangers are desirable in many aerospace applications. New additive manufacturing approaches, such 3D printing, have enabled the fabrication of heat exchange devices utilizing geometries that cannot be fabricated using traditional approaches. The new geometries enabled by 3D printing may result in higher heat transfer using smaller devices, however, constraints associated with the fabrication of these devices also impose potential performance degradations. This document presents the design and analysis of a novel, compact counter flow heat exchanger which uses helically shaped passages to enhance the effectiveness of the heat transfer. Although the helical passages increase the heat transfer and …
Investigation Of A Novel Turbulence Model And Using Leading-Edge Slots For Improving The Aerodynamic Performance Of Airfoils And Wind Turbines, Saman Beyhaghi
Investigation Of A Novel Turbulence Model And Using Leading-Edge Slots For Improving The Aerodynamic Performance Of Airfoils And Wind Turbines, Saman Beyhaghi
Theses and Dissertations
Because of the problems associated with increase of greenhouse gases, as well as the limited supplies of fossil fuels, the transition to alternate, clean, renewable sources of energy is inevitable. Renewable sources of energy can be used to decrease our need for fossil fuels, thus reducing impact to humans, other species and their habitats. The wind is one of the cleanest forms of energy, and it can be an excellent candidate for producing electrical energy in a more sustainable manner. Vertical- and Horizontal-Axis Wind Turbines (VAWT and HAWT) are two common devices used for harvesting electrical energy from the wind. …
Takeoff And Landing Distance Measurement: An Evaluation Of Laser Altimetry For The Collection Of Absolute Aircraft Altitude, Christopher John Kennedy
Takeoff And Landing Distance Measurement: An Evaluation Of Laser Altimetry For The Collection Of Absolute Aircraft Altitude, Christopher John Kennedy
Theses and Dissertations
The measurement of takeoff and landing distance during flight testing of general aviation aircraft requires the accurate measurement of aircraft position over the ground and altitude up to 50 feet above surface elevation. Current methods of evaluating takeoff and landing distances include cinetheodolites, laser and radar trackers, and Differential Global Positioning Systems (DGPS). The use of laser altimetry to range altitude above the ground originated with military and agricultural aircraft. The AgLaser laser module was an infrared laser ranging unit designed for agricultural aircraft to gauge optimal spray height above a field. The AgLaser system has a stated accuracy of …
Multidisciplinary Shape Optimization Of A Composite Blended Wing Body Aircraft, Charles Maxwell Boozer
Multidisciplinary Shape Optimization Of A Composite Blended Wing Body Aircraft, Charles Maxwell Boozer
Theses and Dissertations
A multidisciplinary shape optimization tool coupling aerodynamics, structure, and performance was developed for battery powered aircraft. Utilizing high-fidelity computational fluid dynamics analysis tools and a structural wing weight tool, coupled based on the multidisciplinary feasible optimization architecture; aircraft geometry is modified in the optimization of the aircraft’s range or endurance. The developed tool is applied to three geometries: a hybrid blended wing body, delta wing UAS, the ONERA M6 wing, and a modified ONERA M6 wing. First, the optimization problem is presented with the objective function, constraints, and design vector. Next, the tool’s architecture and the analysis tools that are …
Single Waypoint Zem/Zev Based Closed-Loop Controller Design For Rendezvous With A Rotating Target, Armando Alvarez Rolins
Single Waypoint Zem/Zev Based Closed-Loop Controller Design For Rendezvous With A Rotating Target, Armando Alvarez Rolins
Theses and Dissertations
The research presented in this thesis addresses a very specific kind of autonomous rendezvous procedure between two spacecraft in close proximity, namely that in which the chaser object is attempting to dock at a location on a rotating target which is tracing a circle perpendicular to the axis of rotation. The approaches that have been mentioned in literature which focus on this specific condition make use of offline optimization algorithms to plot the trajectory of the chaser and use closed-loop control to follow that trajectory. This method is computationally demanding and does not allow for feedback in the desired boundary …
Effect Of The Wake Structure On Drag Coefficient For A Thin Flexible Wire, Harika Gurram
Effect Of The Wake Structure On Drag Coefficient For A Thin Flexible Wire, Harika Gurram
Theses and Dissertations
The present research work focuses on investigating the effect of wake structure on the drag coefficient of a thin flexible wire. Previous researchers have investigated the flow characteristics around the cylinder and estimated the drag coefficient for different Reynold’s number range. The flow transition characteristics in the boundary layer and its effect on the drag coefficient were described. These studies were performed on a non-deformable cylinder. The present work focuses on the drag characteristics of thin flexible cylinders whose diameter is on the order of microns. The results showed up to 30% lower value than reported literature drag coefficient values …
Small Fixed-Wing Aerial Positioning Using Inter-Vehicle Ranging Combined With Visual Odometry, Benjamin M. Fain
Small Fixed-Wing Aerial Positioning Using Inter-Vehicle Ranging Combined With Visual Odometry, Benjamin M. Fain
Theses and Dissertations
There has been increasing interest in developing the ability for small unmanned aerial systems (SUAS) to be able to operate in environments where GPS is not available. This research considers the case of a larger aircraft loitering above a smaller GPS-denied SUAS. This larger aircraft is assumed to have greater resources which can overcome the GPS jamming and provide range information to the SUAS flying a mission below. This research demonstrates that using a ranging update combined with an aircraft motion model and visual odometry can greatly improve the accuracy of a SUASs estimated position in a GPS-denied environment.
Optimal Design Of A Hexakis Icosahedron Vacuum Based Lighter Than Air Vehicle, Joseph R. Schwemmer
Optimal Design Of A Hexakis Icosahedron Vacuum Based Lighter Than Air Vehicle, Joseph R. Schwemmer
Theses and Dissertations
Due to the rising cost and scarcity of helium, new methods to ensure buoyancy for lighter-than-air vehicles (LTAVs) are being sought. One alternative under study uses an internal vacuum to reduce the weight to buoyancy ratio. It's a novel approach; however, the vacuum presents challenges for the vehicle's structure. The structure must have minimum mass while preventing buckling and excess stress throughout the frame and membrane. The structure under analysis is a hexakis icosahedron with a membrane covering. Achieving minimum mass involves optimizing the structure under the loading conditions. Finite-element analysis (FEA) and direct-search methods are employed, providing an optimal …
Military Space Mission Design And Analysis In A Multi-Body Environment: An Investigation Of High-Altitude Orbits As Alternative Transfer Paths, Parking Orbits For Reconstitution, And Unconventional Mission Orbits, John N. Brick
Theses and Dissertations
High-altitude satellite trajectories are analyzed in the Earth-Moon circular restricted three-body problem. The equations of motion for this dynamical model possess no known closed-form analytical solution; therefore, numerical methods are employed. To gain insight into the dynamics of high-altitude trajectories in this multi-body dynamical environment, periapsis Poincare' maps are generated at particular values of the Jacobi Constant. These maps are employed as visual aids to generate initial guesses for orbital transfers and to determine the predictability of the long term behavior of a spacecraft's trajectory. Results of the current investigation demonstrate that high-altitude transfers may be performed for comparable, and …
Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite At 1200°C In Air And In Steam, Nicholas J. Boucher
Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite At 1200°C In Air And In Steam, Nicholas J. Boucher
Theses and Dissertations
The tension-tension fatigue behavior of an advanced melt-infiltrated (MI) silicon carbide/silicon carbide (SiC/SiC) ceramic matrix composite (CMC) was investigated at 1200 degrees Celsius in air and in steam. The MI composite consisted of ten 0/90 plies of Hi-Nicalon-S SiC fibers woven in a five harness satin weave (5HSW), a CVI BN interphase to provide a weak fiber-matrix interphase, and a CVI SiC matrix layer followed by infiltration with SiC particulate slurry and molten silicon. Nine tensile specimens of the material were used in a pilot investigation of mechanical performance at elevated temperature. One specimen was used in a monotonic tensile …
Time-Dependent Validation Of Finite Element Strain Distribution Of A Plastically-Deformed Plate Via Digital Image Correlation, Kevin R. Knapp
Time-Dependent Validation Of Finite Element Strain Distribution Of A Plastically-Deformed Plate Via Digital Image Correlation, Kevin R. Knapp
Theses and Dissertations
Generation of residual stress is an essential step in the generation of Goodman data via Air Force Research Laboratory's vibration-based fatigue test. Conventional Goodman data is constructed through uniaxial fatigue testing at a rate of 40 Hz, while the vibration-based testing excites stresses at 1,600 Hz in a stress state that is similar to those seen in gas turbine engine airfoils. A pre-strain procedure is conducted to form residual tensile stress, which serves as a steady stress when the specimen is subjected to fully-reversed vibration-based fatigue loads. This steady tensile stress is desired at the fatigue zone of the test …
Computational Optimization Under Uncertainty Of An Active Flow Control Jet, Luke A. Welch
Computational Optimization Under Uncertainty Of An Active Flow Control Jet, Luke A. Welch
Theses and Dissertations
Optimization under uncertainty is performed to determine the optimal parameters of an active flow control jet to impart robust control during transonic cruise. A steady blowing jet is optimized on an airfoil to impart a change in lift greater than or equal to that generated by traditional control surfaces. The design candidates are computationally evaluated using the NASA flow solver, FUN3D, under 20 unique combinations of angle of attack, Reynolds number, and Mach number in order to propagate model input uncertainty. The mean change in lift and the associated standard deviation are included in the optimization framework to help ensure …
Investigation Of Dynamic Store Separation Out Of A Weapons Bay Cavity Utilizing A Low Speed Wind Tunnel, Andrew D. Bower
Investigation Of Dynamic Store Separation Out Of A Weapons Bay Cavity Utilizing A Low Speed Wind Tunnel, Andrew D. Bower
Theses and Dissertations
Characterizing mission store trajectories as they separate from a weapons bay cavity is highly relevant to the Air Force mission. The flow around a weapons bay is unsteady. The unsteady flow can cause a mission store separation trajectory to be unpredictable, and such is the case for what some have termed a pitch bifurcation. Traditional wind tunnel testing is incapable of detecting a bifurcation because traditional wind tunnel testing records time-averaged data. In this study, an experimental testing system was developed and refined in order to support the time-accurate characterization of dynamic mission store separation events. A Motion Test Apparatus …
An Analysis Of Radio-Frequency Geolocation Techniques For Satellite Systems Design, Daniel R. Barnes
An Analysis Of Radio-Frequency Geolocation Techniques For Satellite Systems Design, Daniel R. Barnes
Theses and Dissertations
This research 1) evaluates the effectiveness of CubeSat radio-frequency geolocation and 2) analyzes the sensitivity of different RF algorithms to system parameters. A MATLAB simulation is developed to assess geolocation accuracy for variable system designs and techniques (AOA, TDOA, T/FDOA). An unconstrained maximum likelihood estimator (MLE) and three different digital elevation models (DEM) are utilized as the surface of the Earth constraint to improve geolocation accuracy. The results presented show the effectiveness of the MLE and DEM techniques, the sensitivity of AOA, TDOA, and T/FDOA algorithms, and the system level performance of a CubeSat geolocation cluster in a 500km circular …
Analysis Of Additively Manufactured Lattice Structures Using Finite Element Methods, Christopher A. Box
Analysis Of Additively Manufactured Lattice Structures Using Finite Element Methods, Christopher A. Box
Theses and Dissertations
Additive Manufacturing (AM) processes are well known for their ability to fabricate parts with complex geometries. Lattice structures leverage this ability to create parts with high strength-to-weight ratio and other desirable structural qualities. This research presents a parameterized modeling tool using common Finite Element Analysis (FEA) and scripting software with which aggregated lattice structures can be analyzed, given different geometric properties and loading conditions. A full factorial Design of Experiments is run to explore the effects of various parameters on the strength of lattice structures. Experimental compressive strength results from three FDM-produced PLA lattices are discussed and compared to predictions …
Stressed Oxidation Of Hafnium Diboride In Air At 1500°C, Thomas A. Bowen
Stressed Oxidation Of Hafnium Diboride In Air At 1500°C, Thomas A. Bowen
Theses and Dissertations
Hypersonic vehicles with narrow airfoils produce thin boundary layers and shock temperatures in excess of 2000°C, exceeding the operating limits of traditional aerospace materials. The use of ultra-high temperature ceramics (UHTCs) allows for operating temperatures far exceeding those of metallic alloys. One such UHTC is hafnium diboride (HfB2). Transition metal diborides generally experience significant oxidation degradation at elevated temperatures. The use of additives, such as silicon carbide (SiC) has been shown to reduce the oxidation of transition metal diborides. This research focused on the compressive creep of HfB2 with varying amounts of SiC in air at 1500°C. …
The Impact Of Atmospheric Fluctuations On Optimal Boost Glide Hypersonic Vehicle Dynamics, Melissa A. Dunkel
The Impact Of Atmospheric Fluctuations On Optimal Boost Glide Hypersonic Vehicle Dynamics, Melissa A. Dunkel
Theses and Dissertations
A project under the management of Air Force Research Laboratory has begun development of a six degree of freedom model for use in hypersonic vehicle development and application. One area of interest is the perturbation of vehicle behavior based on atmospheric fluctuations – how the performance of the vehicle changes with respect to “hot”, “cold” and standard day conditions. The method developed to fill this need uses real-world data from the Global Forecast System to create a “hot” and “cold” day dataset to compare with the standard day model. The key parameter is atmospheric density, a value calculated over a …
Evaluating The Autonomous Flying Qualities Of A Simulated Variable Stability Aircraft, Ali M. Hamidani
Evaluating The Autonomous Flying Qualities Of A Simulated Variable Stability Aircraft, Ali M. Hamidani
Theses and Dissertations
Delivering communications from high altitudes, at airspeeds of just 30 knots, gathering data from active volcanoes and forming hurricanes, and collecting ISR over hostile territories, UAVs are at the ready to perform those missions that are too dull, dirty, or dangerous for manned aircraft. However, the proliferation of this new technology has its fair share of challenges. Over 460 DoD UAV mishaps have occurred since 2001, with almost half resulting in damages of $2M or more. One incident almost ended in fatalities, when a UAV, suffering from loss of control, collided with a C-130. That loss of control is what …
Formation Flight Of Earth Satellites On Kam Torus Using Classical Orbital Elements, Marissa C. Reabe
Formation Flight Of Earth Satellites On Kam Torus Using Classical Orbital Elements, Marissa C. Reabe
Theses and Dissertations
This research uses the KAM theory that has been refined by Wiesel to show that Earth-satellites dynamics can be represented by an integrable Hamiltonian system with a small perturbation, like Earths geopotential. The satellite will follow a torus in phase space and remain on that KAM torus for all time unless acted on by a non-conservative force. A torus frequency was calculated, in this research, using a truth model in System Tool Kit (STK) and the High Precision Orbit Propagator (HPOP) to develop an accurate ephemeris file listing the Classical Orbital Elements (COEs). The frequencies found from the truth model …
Investigating Analytical And Numerical Methods To Predict Satellite Orbits Using Two-Line Element Sets, Adam T. Rich
Investigating Analytical And Numerical Methods To Predict Satellite Orbits Using Two-Line Element Sets, Adam T. Rich
Theses and Dissertations
As Low Earth Orbit (LEO) contains an ever-increasing number of objects, the prediction of future object positions must be precise in order to avoid collisions. Object positions are distributed in two-line element (TLE) sets and are generated using the analytical propagator known as Simplified General Perturbations 4 (SGP4). However, a numerical integrator called Special Perturbations (SP) provides an alternative approach to TLE generation and propagation. In this thesis, TLE accuracy was determined with both models, and the length of time that a single element set can provide valid information was also established. With two-line element sets as data, comparisons were …
Relating Film Cooling Performance Between Ambient And Near Engine Temperatures, Christopher J. Vorgert
Relating Film Cooling Performance Between Ambient And Near Engine Temperatures, Christopher J. Vorgert
Theses and Dissertations
This thesis explores multiple topics, including the relative importance of nondimensional parameters that relate film cooling performance within different temperature regimes and the effects of internal coolant flow and coolant temperature on overall film cooling effectiveness. A Hastelloy model representative of a turbine blade was utilized for IR tests. Near engine temperatures were produced via premixed propane and air combustion in a Well-Stirred Reactor (WSR) with air supplied as the film coolant gas. Near ambient conditions used heated air for freestream flow and carbon dioxide, argon, or air as film coolant gases. It was found that even with multiple matched …
Combined Stereo Vision And Inertial Navigation For Automated Aerial Refueling, Daniel T. Johnson
Combined Stereo Vision And Inertial Navigation For Automated Aerial Refueling, Daniel T. Johnson
Theses and Dissertations
This paper describes the design of an EKF to obtain the precise relative position of two aircraft in a refueling maneuver while operating in GPS denied environments. The EKF uses the INS already present in both aircraft as well as the stereo camera system organic to new tanker systems. The aircraft trajectories are generated according to authentic refueling profiles with flight dynamics software and executed in a 3D virtual environment to enable deterministic simulation of the stereo camera system and to demonstrate the effectiveness of the combined system in a refueling scenario. Results show the system can achieve sufficient accuracy …