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Link Performance Analysis For A Proposed Future Architecture Of The Air Force Satellite Control Network, Eric W. Nelson
Link Performance Analysis For A Proposed Future Architecture Of The Air Force Satellite Control Network, Eric W. Nelson
Theses and Dissertations
The Air Force Satellite Control Network (AFSCN) is a worldwide network of ground stations that support a wide variety of users from the National Aeronautics and Space Administration (NASA) to the National Reconnaissance Office (NRO). The network performs tracking, telemetry, and commanding (TT&C) for these varied users. Users, located at Satellite Operations Centers (SOC), must compete for time on the AFSCN. This thesis demonstrates how to predict satellite link performance, specifically by users of the AFSCN. It will also demonstrate how users might use this capability to save spacecraft power. A tool was created called the AFSCN Link Predictor (LP) …
Development Of Photographic Dynamic Measurements Applicable To Evaluation Of Flapping Wing Micro Air Vehicles, Jeremy C. Murray
Development Of Photographic Dynamic Measurements Applicable To Evaluation Of Flapping Wing Micro Air Vehicles, Jeremy C. Murray
Theses and Dissertations
Developments in the area of flapping wing micro air vehicles (FWMAVs) of a small size and with limited range. This has lead to a great deal of interest in biomimetric designs based on flapping wing flyers, including the North American Hawkmoth (Manduca Sexta). By utilizing high speed photography and photogrammetry the dynamic flapping of the wing can be characterized for comparison with mathematical models, namely computational fluid dynamics (CFD) and finite element analysis (FEA).To successfully utilize high speed image capture, a method of successfully digitizing many data points in a short period of time needs to be developed. The effort …
Scramjet Isolator Modeling And Control, John R. Hutzel
Scramjet Isolator Modeling And Control, John R. Hutzel
Theses and Dissertations
The scramjet isolator is a duct in which pressure increases from the inlet to the combustor via a shock train. The shock train leading edge (LE) location must be controlled in an operational scramjet. A LE location measurement algorithm, dynamic model, and control algorithm were developed and validated with 500 frame per second (FPS) shadowgraph images in this research. The test apparatus consisted of a direct connect cold-flow high-speed wind tunnel with an adjustable ramp mounted in the tunnel floor. Ramp adjustments changed the tunnel cross-sectional area which changed the tunnel back pressure and LE location. Wall-mounted pressure transducers and …
Coupled Radiation-Gasdynamic Solution Method For Hypersonic Shock Layers In Thermochemical Nonequilibrium, Christopher L. Martin Jr.
Coupled Radiation-Gasdynamic Solution Method For Hypersonic Shock Layers In Thermochemical Nonequilibrium, Christopher L. Martin Jr.
Theses and Dissertations
The purpose of this research was to develop a highly accurate computational method for calculating the nonequilibrium radiative heat transfer within reentry shock layers. The nonequilibrium state of the flowfield was solved using the multispecies multitemperature nonequilibrium flow solver NH7AIR which is capable of separately tracking the vibrational energy of each diatomic species and the energy of the free electrons. The calculation of radiative heat transfer was performed by utilizing the detailed line-by-line spectral radiation solver SPRADIAN. Two radiative transport schemes were implemented in this coupled code. The first scheme was the standard tangent slab solution method. The second scheme …
The Use Of Various Failure Criteria As Applied To High Speed Wear, David A. Huber
The Use Of Various Failure Criteria As Applied To High Speed Wear, David A. Huber
Theses and Dissertations
This research has been aimed at developing methods to predict mechanical wear of sliding bodies at high velocities. Specifically, wear of test sled slippers at the Holloman High Speed Test Track at Holloman AFB, NM, is being considered. Developing a numerical model to represent the velocity range achieved at the test track is infeasible, so numerical modeling techniques must be adopted. Previous research has made use of finite element codes to simulate the high velocity sliding event. However, the extreme velocities at the test track can create numerical errors in the finite element codes. To avoid the numerical errors, an …
Increasing The Performance Of A Sliding Discharge Actuator Through The Application Of Multiple Potentials, Steven D. Seney Jr.
Increasing The Performance Of A Sliding Discharge Actuator Through The Application Of Multiple Potentials, Steven D. Seney Jr.
Theses and Dissertations
This work encompasses a comparison between a sliding discharge DBD actuator with grounded and AC biased sliding electrode driven at kHz frequency. The induced velocity in the bulk flow was recorded with PIV and compared for multiple potential splits between two test configurations and a baseline sliding discharge actuator over three test phases. In the first test phase, varying potential splits were examined between the primary and secondary electrode with the sliding electrode grounded. The potential splits induced a thicker induced jet than the baseline case with similar peak velocities on the order of 1.25 m/s at the 61 mm …
Design And Control Of Flapping Wing Micro Air Vehicles, Michael L. Anderson
Design And Control Of Flapping Wing Micro Air Vehicles, Michael L. Anderson
Theses and Dissertations
Flapping wing Micro Air Vehicles (MAVs) continues to be a growing field, with ongoing research into unsteady, low Re aerodynamics, micro-fabrication, and fluid-structure interaction. However, research into flapping wing control of such MAVs continues to lag. Existing research uniformly consists of proposed control laws that are validated by computer simulations of quasi-steady blade-element formulae. Such simulations use numerous assumptions and cannot be trusted to fully describe the flow physics. Instead, such control laws must be validated on hardware. Here, a novel control technique is proposed called Bi-harmonic Amplitude and Bias Modulation (BABM) which can generate forces and moments in 5 …
Two-Dimensional, Time-Dependent Plasma Structures Of A Hall Effect Thruster, David Liu
Two-Dimensional, Time-Dependent Plasma Structures Of A Hall Effect Thruster, David Liu
Theses and Dissertations
The Hall thruster is a type of electric propulsion utilized by satellites to perform a wide variety of missions ranging from station keeping, orbital maneuvers, and even deep space propulsion. In order to accommodate the multitude of missions it also has a wide assortment of sizes and power configurations which can range from approximately an inch in diameter at 20 W to a couple of feet in diameter at 1.5 kW. Additionally, this electro-static device provides high specific impulse without the added weight penalty associated with conventional chemical thrusters. It supplies this high specific impulse by ionizing a gas such …
Evaluation Of Nanocomposites For Shielding Electromagnetic Interference, Kenneth Y. Chong
Evaluation Of Nanocomposites For Shielding Electromagnetic Interference, Kenneth Y. Chong
Theses and Dissertations
Numerous efforts are ongoing to research and develop nanocomposite materials for space applications. Current composite spacecraft materials are nonconductive and require costly shielding materials to be applied in order to protect spacecraft from the harmful effects caused by electromagnetic interference (EMI), which is a by-product of exposure to the space environment. Conductive fillers (nanofibers) are being employed in composites to produce nanocomposites to reduce the dry weight of space vehicles while providing sufficient protection against EMI. This eliminates the need to apply secondary shielding materials to spacecraft. This thesis studied a nanocomposite consisting of Cycom 5575-2 glass with multi-walled carbon …
Stochastic Real-Time Optimal Control: A Pseudospectral Approach For Bearing-Only Trajectory Optimization, Steven M. Ross
Stochastic Real-Time Optimal Control: A Pseudospectral Approach For Bearing-Only Trajectory Optimization, Steven M. Ross
Theses and Dissertations
A method is presented to couple and solve the optimal control and the optimal estimation problems simultaneously, allowing systems with bearing-only sensors to maneuver to obtain observability for relative navigation without unnecessarily detracting from a primary mission. A fundamentally new approach to trajectory optimization and the dual control problem is developed, constraining polynomial approximations of the Fisher Information Matrix to provide an information gradient and allow prescription of the level of future estimation certainty required for mission accomplishment. Disturbances, modeling deficiencies, and corrupted measurements are addressed with recursive updating of the target estimate with an Unscented Kalman Filter and the …
Study Of Varying Boundary Layer Height On Turret Flow Structures, Renato Jelic
Study Of Varying Boundary Layer Height On Turret Flow Structures, Renato Jelic
Theses and Dissertations
The Air Force Institute of Technology and the Air Force Research Labs are investigating flows over turrets which are commonly encountered in directed energy integrations with air vehicles. In this work, the computational study was performed using the NASA developed time-marching finite volume code OVERFLOW 2.2 to analyze the effect of boundary layer height on symmetrical and non-symmetrical turret geometries. The effects of aerodynamics yield to the aberration of the laser beam through two methods, aero-optical and aero-mechanical jitter. The analysis of the flow features, pressure fluctuations, density fluctuations, and forces and moments on the various geometries was conducted to …
Optical Flow-Based Odometry For Underground Tunnel Exploration, Terra Kier
Optical Flow-Based Odometry For Underground Tunnel Exploration, Terra Kier
Theses and Dissertations
As military operations in degraded or GPS-denied environments continue to increase in frequency and importance, there is an increased necessity to be able to determine precision location within these environments. Furthermore, authorities are finding a record number of tunnels along the U.S.-Mexico border; therefore, underground tunnel characterization is becoming a high priority for U.S. Homeland Security as well. This thesis investigates the performance of a new image registration technique based on a two camera optical- flow configuration using phase correlation techniques. These techniques differ from other image based navigation methods but present a viable alternative increasing autonomy and answering the …
Solar Warning Architecture For Manned Missions To Mars, James S. Bohren, John K. Howard
Solar Warning Architecture For Manned Missions To Mars, James S. Bohren, John K. Howard
Theses and Dissertations
Solar radiation storms represent a dire threat to manned interplanetary space travel. Earth's current solar forecasting architecture is Earth-focused and insufficient to provide timely warnings to a manned mission to Mars, therefore a "best value" solar warning architecture must be identified. A total of 14 solar warning architectures were developed by varying 5 solar sensor locations, 2 processing locations, and 2 communications strategies. Using Satellite Tool Kit, performance of the candidate architectures in terms of Warning Time and Solar Coverage was quantified during a Mars mission scenario based on NASA's Design Reference Architecture 5.0. Cost of each candidate architecture was …
Spacecraft Demand Tasking And Skip Entry Responsive Maneuvers, Robert A. Bettinger
Spacecraft Demand Tasking And Skip Entry Responsive Maneuvers, Robert A. Bettinger
Theses and Dissertations
The purpose of this research was to parametrically investigate the viability of skip entry maneuvers as an alternative to vacuum-only maneuvers, and to identify whether skip entry maneuvers can extend spacecraft mission lifetime by limiting propellant expenditure through the exploitation of the aerodynamic interaction between the upper atmosphere and an example entry vehicle and remote-sensing orbital platform. Employing the X-37B Orbital Test Vehicle (OTV) and a notional satellite design as the example entry vehicles, the entry profile dynamics of a skip entry maneuver were characterized with varying trajectory initial conditions such as entry altitude, entry flight-path angle, and vehicle aerodynamics. …
A Relay-Rover Differential Game, Youngdong Choi
A Relay-Rover Differential Game, Youngdong Choi
Theses and Dissertations
Guidance laws are developed to optimally position a relay Micro-UAV (MAV) to provide an operator at the base with real-time Intelligence, Surveillance, and Reconnaissance (ISR) by relaying communication and video signals when the rover MAV performing the ISR mission is out of radio contact range with the base. The ISR system is comprised of two MAVs, the Relay and the Rover, and a Base. The Relay strives to minimize the radio frequency (RF) power required for maintaining communications, while the Rover performs the ISR mission, which may maximize the required RF power. The optimal control of the Relay MAV entails …
Design And Characterization Of A Space Based Chromotomographic Hyperspectral Imaging Experiment, Jason D. Niederhauser
Design And Characterization Of A Space Based Chromotomographic Hyperspectral Imaging Experiment, Jason D. Niederhauser
Theses and Dissertations
This research focuses upon the design, analysis and characterization of several systems related to a spacebased chromotomographic experiment (CTEx), a hyperspectral imager, currently in development at the Air Force Institute of Technology. Three interrelated subject-areas were developed. The initial focal point was a generic, system-level mechanical layout and integration analysis of the space-based instrument. The scope of this work was intended to baseline the space-based system design in order to allow for further trade-space refinement and requirements development. Second, development of an iteration upon the ground-based version of CTEx was accomplished in an effort to support higher-fidelity field data-collection. This …
Process For Refining And Validating A Finite Element Model Of An Experimental High-Altitude, Long-Endurance (Hale) Aircraft, Nicholas A. Sinnokrak
Process For Refining And Validating A Finite Element Model Of An Experimental High-Altitude, Long-Endurance (Hale) Aircraft, Nicholas A. Sinnokrak
Theses and Dissertations
The work presented here focuses on finite element (FE) modeling of X-HALE, a test aircraft designed and built by the University of Michigan, in conjunction with the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory (AFRL). This scaled vehicle is representative of high-altitude, long-endurance (HALE) aircraft and was designed to provide controlled aeroelastic and flight data. FE models of portions of the X-HALE wing structure were created and analysis results were compared against two separate laboratory static bending tests conducted on X-HALE wing sections. The process documented here should improve future efforts to refine FE models of …
Photogrammetric Measurement Of Recession Rates Of Low Temperature Ablators Subjected To High Speed Flow, David W. Callaway
Photogrammetric Measurement Of Recession Rates Of Low Temperature Ablators Subjected To High Speed Flow, David W. Callaway
Theses and Dissertations
This research advances a technique to simulate high temperature/high speed effects in a high speed/low temperature environment and to capture recession of the test article in three-dimensions. A method of fabricating dry ice test articles was developed, and the AFIT Mach 3 pressure-vacuum wind tunnel was used in combination with the dry ice test articles to collect three-dimensional ablation data for models of different shapes at stagnation pressures ranging from approximately 0.4 atm to 3 atm and stagnation temperatures equivalent to room temperature. High speed Schlieren photography was used for visualization, and the three dimensional shape change was quantified with …
Operational Characteristics Of A Rotating Detonation Engine Using Hydrogen And Air, Rachel M. Russo
Operational Characteristics Of A Rotating Detonation Engine Using Hydrogen And Air, Rachel M. Russo
Theses and Dissertations
Rotating detonation engines (RDE) are pressure gain combustion engines that have the potential for greater efficiency than traditional, constant pressure, deflagration engines. RDEs are smaller and mechanically simpler than pulsed detonation engines. A small diameter (3 in) engine was successfully run on hydrogen and air. Most of the tests were conducted using air with a slightly lower diluents percentage (77% nitrogen as opposed to 79% nitrogen). These tests provided the foundation for determining the operational space (mass flow rate and equivalence ratio) of the rotating detonation engine. From the tests conducted with the lower diluents air, the appropriate run conditions …
Simulations For The Test Flight Of An Experimental Hale Aircraft, Brooke E. Kaszynski
Simulations For The Test Flight Of An Experimental Hale Aircraft, Brooke E. Kaszynski
Theses and Dissertations
Recent events, such as the crash of NASA's Helios aircraft during a test flight, show that more must be known about the nonlinear control of HALE aircraft. Shearer, Cesnik and their co-workers have developed a code that is a practical solution to the coupled nonlinear aeroelasticity and flight dynamics of very flexible aircraft called the University of Michigan's Nonlinear Aeroelastic Simulation Toolbox (UM/NAST). They are also in the process of developing a model HALE aircraft called X-HALE which will be used to validate this code experimentally. This research performs flight simulations with UM/NAST so as to make predictions about X-HALE's …
Polarimetric Enhancements To Electro-Optical Aided Navigation Techniques, Jeremiah D. Johnson
Polarimetric Enhancements To Electro-Optical Aided Navigation Techniques, Jeremiah D. Johnson
Theses and Dissertations
Navigation in indoor and urban environments by small unmanned systems is a topic of interest for the Air Force. The Advanced Navigation Technology Center at the Air Force Institute of Technology is continually looking for novel approaches to navigation in GPS deprived environments. Inertial sensors have been coupled with image aided concepts, such as feature tracking, with good results. However, feature density in areas with large, flat, smooth surfaces tends to be low. Polarimetric sensors have been used for surface reconstruction, surface characterization and outdoor navigation. This thesis combines aspects of some of these algorithms along with a realistic, micro-facet …
Airborne Pseudolites In A Global Positioning System Degraded, Halit Oktay
Airborne Pseudolites In A Global Positioning System Degraded, Halit Oktay
Theses and Dissertations
The high accuracy of the Global Positioning System allows for precision navigation in support of current and future military operations. However, generating a three-dimensional position using GPS requires a clear line-of-sight between the user and at least four GPS satellites, and so the GPS service can be denied in scenarios such as a street surrounded by tall buildings. Therefore, there is a need for augmentation in these environments. Pseudolites, which transmit GPS-like ranging signals, can be deployed in order to improve the geometry and provide additional ranging signals. Users can then receive and process both GPS and pseudolite signals simultaneously …
Non-Gps Navigation Using Vision-Aiding And Active Radio Range Measurements, Erich H. Lichtfuss
Non-Gps Navigation Using Vision-Aiding And Active Radio Range Measurements, Erich H. Lichtfuss
Theses and Dissertations
The military depends on the Global Positioning System (GPS) for a wide array of advanced weaponry guidance and precision navigation systems. Lack of GPS access makes precision navigation very difficult. Inclusion of inertial sensors in existing navigation systems provides short-term precision navigation, but drifts significantly over long-term navigation. This thesis is motivated by the need for inertial sensor drift-constraint in degraded and denied GPS environments. The navigation system developed consists of inertial sensors, a simulated barometer, three Raytheon DH500 radios, and a stereo-camera image-aiding system. The Raytheon DH500 is a combat communication radio which also provides range measurements between radios. …
Signals Of Opportunity Navigation Using Wi-Fi Signals, Wilfred E. Noel
Signals Of Opportunity Navigation Using Wi-Fi Signals, Wilfred E. Noel
Theses and Dissertations
Since GPS is generally limited to areas with clear sky view, additional methods of navigation are currently being explored. This thesis explores navigation using Signals of Opportunity(SoOP). The signals chosen for evaluation in this thesis are the common Internet IEEE 802.11a/g signals, or Wi-Fi. This thesis presents SoOP navigation based on cross-correlations of received data from multiple Wi-Fi stations. It shows the effectiveness of the methods using collected Wi-Fi signals in a real-world environment. By using simple statistical representations of collected data in large groups, or windows, cross-correlation calculations can produce timing offsets between simulated stations. The timing offsets, or …
Vision Aided Inertial Navigation System Augmented With A Coded Aperture, Jamie R. Morrison
Vision Aided Inertial Navigation System Augmented With A Coded Aperture, Jamie R. Morrison
Theses and Dissertations
Navigation through an indoor environment is a formidable challenge for an autonomous micro air vehicle. One solution is a vision aided inertial navigation system using depth-from-defocus to determine heading and depth to features in the scene. Depth-from-defocus uses a focal blur pattern to estimate depth. As depth increases, the observable change in the focal blur is generally reduced. Consequently, as the depth of a feature to be measured increases, the measurement performance decreases. The Fresnel zone plate, used as an aperture, introduces multiple focal planes. Interference between the multiple focal planes produce changes in the aperture that extend the depth …
Kernelized Locality-Sensitive Hashing For Fast Image Landmark Association, Mark A. Weems
Kernelized Locality-Sensitive Hashing For Fast Image Landmark Association, Mark A. Weems
Theses and Dissertations
As the concept of war has evolved, navigation in urban environments where GPS may be degraded is increasingly becoming more important. Two existing solutions are vision-aided navigation and vision-based Simultaneous Localization and Mapping (SLAM). The problem, however, is that vision-based navigation techniques can require excessive amounts of memory and increased computational complexity resulting in a decrease in speed. This research focuses on techniques to improve such issues by speeding up and optimizing the data association process in vision-based SLAM. Specifically, this work studies the current methods that algorithms use to associate a current robot pose to that of one previously …
Analysis Of Flow Migration In An Ultra-Compact Combustor, Brian T. Bohan
Analysis Of Flow Migration In An Ultra-Compact Combustor, Brian T. Bohan
Theses and Dissertations
One of the major efforts for turbine engine research is to improve the thrust to weight of the system. One novel concept for accomplishing this is the use of an Ultra-Compact Combustor (UCC). The UCC attempts to shorten the overall combustion length (thereby reducing weight) by performing the combustion in the circumferential direction along the outside diameter of the core flowpath. One of the major benefits of this design is enhanced combustion due to the establishment of a high-g field in the circumferential cavity. AFIT and the Air Force Research Laboratory (AFRL) have been teamed for several years in understanding …
Performance Characterization Of A Novel Plasma Thruster To Provide A Revolutionary Operationally Responsive Space Capability With Micro- And Nano-Satellites, John-David C. De La Harpe
Performance Characterization Of A Novel Plasma Thruster To Provide A Revolutionary Operationally Responsive Space Capability With Micro- And Nano-Satellites, John-David C. De La Harpe
Theses and Dissertations
Few options currently exist to provide propulsion for extremely small satellites due to design constraints on power, volume, and weight. However, future operation will require a capability to conduct orbital maneuvers, momentum dumping, and precision pointing for these low cost satellites. The research presented here represents the first effort to operate and quantify the performance of a new micro plasma thruster design which provides a novel solution to these disparate competing constraints. The thruster in this study represents a deviation from traditional circular Hall thruster design practices, because it eschews a central magnetic circuit, which results in nearly parallel electric …
Vibration Interaction In A Multiple Flywheel System, Jordan A. Firth
Vibration Interaction In A Multiple Flywheel System, Jordan A. Firth
Theses and Dissertations
This study uses a linear model of an Integrated Power and Attitude Control System (IPACS) to investigate the vibration interaction between multiple flywheels. An easily extendable Matlab® script is created for the analysis of flywheel vibrations. This script is used to build a vibration model consisting of two active magnetic bearing flywheels mounted on a support structure. The flywheels are rotated at varying speeds, with an imbalance-induced centripetal force in one or both wheels causing vibrations in both wheels. Flywheel and system responses are examined for low frequency vibrations which would cause undesirable excitation to a satellite using IPACS, with …
Kam Torus Frequency Generation From Two-Line Element Sets, Gregory R. Frey
Kam Torus Frequency Generation From Two-Line Element Sets, Gregory R. Frey
Theses and Dissertations
The Kolmogorov Arnold and Moser (KAM) theorem states that a lightly perturbed Hamiltonian system will have solutions which lie on a torus. Earlier work by the second author has shown that most Earth satellite orbits perturbed by the geopotential lie on KAM tori. The problem then arises as to how to convert the current satellite tracking orbits to KAM tori. A KAM torus is characterized by three frequencies and three phase angles. The frequencies are essentially the rates of change of the mean anomaly, the longitude of the ascending node, and the argument of perigee. In this paper we explore …