Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Keyword
-
- Computational Fluid Dynamics (7)
- Boundary Layer (3)
- Fluid Dynamics (3)
- Algorithms (2)
- Center_CCR (2)
-
- Collision Avoidance Systems (2)
- Drag (2)
- Electric Propulsion (2)
- Geolocation (2)
- Low Earth Orbits (2)
- Maneuvers (2)
- Test and Evaluation (2)
- Wind Tunnel Tests (2)
- #antcenter (1)
- Ablation models (1)
- Acoustic Wave Propagation (1)
- Active Flow Control (1)
- Active aircraft control (1)
- Ad-hoc mesh network (1)
- Additive manufacturing (1)
- Aerodynamic Characteristics (1)
- Aerodynamic characteristics (1)
- Aerodynamics (1)
- Air Flow (1)
- Aircraft (1)
- Aircraft control (1)
- Aircrafts (1)
- Alternative positioning methods (1)
- Altitude (1)
- Angle of arrival (1)
Articles 1 - 30 of 49
Full-Text Articles in Engineering
Earth – Mars Cycler Vehicle Conceptual Design, Bhumika Patel
Earth – Mars Cycler Vehicle Conceptual Design, Bhumika Patel
Theses and Dissertations
This thesis summarizes a conceptual design for an Earth – Mars Cycler vehicle designed to transfer astronauts between Earth and Mars. The primary objective of the design study is to accommodate the crews’ needs and to estimate the overall mass and power required during Earth – Mars transfer. The study defines a concept of operations and system functional requirements and discusses the systems breakdown and subsystems design analysis. Systems developed for the cycler vehicle is designed primarily for the S1L1 cycler trajectory. The initial sizing of cycler subsystems is based on reference data from historical human spaceflight. The study performed …
Remote Sensing, Modeling, And Spectroscopic Studies Of Gigantic Jets And Lightning Leaders, Levi Boggs
Remote Sensing, Modeling, And Spectroscopic Studies Of Gigantic Jets And Lightning Leaders, Levi Boggs
Theses and Dissertations
This dissertation focuses on four interrelated investigations with the ultimate goal of better understanding electrical phenomena in the lower and upper atmosphere. The four investigations utilized observations and data analysis for electrical discharges occurring in the troposphere, such as cloud-to-ground and intracloud discharges, and discharges occurring in the stratosphere/lower ionosphere, known as gigantic jets. The observations are from ground-based high-speed cameras and lightning locating systems, space-borne lightning imagers, and remote and in-situ meteorological instrumentation. Numerical modeling was also performed to study the lightning associated with gigantic jets by using a stochastic lighting propagation model. Finally, this dissertation focuses on the …
Investigating The Effects Of Altitude And Flap Setting On The Specific Excess Power Of A Pa-28-161 Piper Warrior, Tjimon Meric Louisy
Investigating The Effects Of Altitude And Flap Setting On The Specific Excess Power Of A Pa-28-161 Piper Warrior, Tjimon Meric Louisy
Theses and Dissertations
The high number of General Aviation (GA) accidents attributed to Loss of Control suggests that GA pilots are lacking low speed awareness and are unable to appropriately recognize when the aircraft is in a low energy state. There is, therefore, an urgent need for the development of an energy management system which is applicable to GA aircraft that can alert the pilot in situations of low energy conditions and recommends to the pilot the appropriate corrective action to restore conditions to a safe energy state. This will require the development of an algorithm that governs this energy management system that …
Dynamics Considerations Dedicated To Study Bodies In High-Altitude Free Fall, Michelle Carolina Rodriguez
Dynamics Considerations Dedicated To Study Bodies In High-Altitude Free Fall, Michelle Carolina Rodriguez
Theses and Dissertations
The objective of this thesis is to develop a simulation model to study the dynamics of a rigid body in free fall. A set of 6 degrees of freedom (DOF) equations is developed to reflect the dynamic and trajectory characteristics over time. The simulation models a body dropped at different altitudes ranging from 30,480 – 39,624 m (100,000 – 130,000 ft). The trajectory of the body is analyzed using a mathematical nonlinear dynamics model. The mathematical model was developed in MATLAB and Simulink which can be modified for different geometries and conditions. The model was validated by testing that the …
Development Of Cislunar Space Logistics Networks For Satellite Constellation Support Using Event-Driven Generalized Multi-Commodity Network Flows, Alexander R. Collins
Development Of Cislunar Space Logistics Networks For Satellite Constellation Support Using Event-Driven Generalized Multi-Commodity Network Flows, Alexander R. Collins
Theses and Dissertations
As space becomes an increasingly congested domain, the risk of damage to satellite constellations is increasing. In response, there is an increasing need for capabilities for unmanned repair, refueling, and reconstitution (R3) of those constellations. Cislunar orbits offer a promising storage and low-cost transfer solution for on-orbit service vehicles and replacement satellites to leverage those capabilities. This research makes use of mixed-integer linear programming-based logistics models to determine the situations in which a cislunar mission architecture would offer a cost-effective alternative to Earth-based R3. The network models presented in this research make use of the latest developments in Event-Driven Generalized …
Effects Of Carbon-Based Ablation Products On Hypersonic Boundary Layer Stability, Olivia S. Elliott
Effects Of Carbon-Based Ablation Products On Hypersonic Boundary Layer Stability, Olivia S. Elliott
Theses and Dissertations
Hypersonic vehicles require an accurate prediction of the transition of the boundary layer for the design of the thermal protection system due to the high heating rates under turbulent flow. Many thermal protection systems are carbon-based and introduce new species, specifically CO2, into the boundary layer flow which are known to dampen the instabilities that lead to transition for hypersonic vehicles. A Computation Fluid Dynamics study was accomplished examining the concentration of CO2 required to impact boundary layer transition over both sharp and blunt cones. These results were used in conjunction with air-carbon ablation models models to …
Cislunar Trajectory Generation With Sun-Exclusion Zone Constraints Using A Genetic Algorithm And Direct Method Hybridization, Joshua A. Ostman
Cislunar Trajectory Generation With Sun-Exclusion Zone Constraints Using A Genetic Algorithm And Direct Method Hybridization, Joshua A. Ostman
Theses and Dissertations
Space missions to the Moon have received renewed interest in recent decades. Science missions continue to be sent to the Moon, and several space agencies have aspirations of establishing a human presence on the Moon. With the increased number of artificial objects in cislunar space, the problem of tracking these objects arises. Optical sensors are able to track these objects in deep space. However, optical sensors cannot track objects that are close to the Sun as viewed from the observer. This unobservable region is the Sun-exclusion zone (SEZ). This research attempts to create optimal Moon-Earth transfers which are completely in …
Development Of An Automated Fiber Placement Process For The Fabrication Of Thermoplastic Composite Laminates, Anthony M. Sabido
Development Of An Automated Fiber Placement Process For The Fabrication Of Thermoplastic Composite Laminates, Anthony M. Sabido
Theses and Dissertations
An automated fiber placement process is desired for manufacturing variable-stiffness thermoplastic composite laminates. By developing such a composite laminate, it is possible to take advantage of the tunable performance increases that are achievable by spatially steering individual tows. In addition, using a thermoplastic polymer as the matrix material has many advantages: a high toughness, ability to employ thermoplastic joining processes that do not require adhesives, long storage life, and lacks the need to be refrigerated. This process was experimentally developed, where the effect of various process parameters on the quality of the laminate were evaluated. An experimental AFP head was …
Experimental Analysis Of The Automated Fiber Placement Manufacturing Parameters For High And Low Tack Prepreg Material, Anis Baz Radwan
Experimental Analysis Of The Automated Fiber Placement Manufacturing Parameters For High And Low Tack Prepreg Material, Anis Baz Radwan
Theses and Dissertations
Automated Fiber Placement (AFP) is a flexible but complex manufacturing technique which is used to layup carbon fiber tows into flat or curved structures. That could be achieved through linear and steered paths of fibers. The quality of AFP layup is highly dependent on the manufacturing process parameters such as layup temperature, tow feedrate, compaction force, and tow tension. Understanding how those parameters affect the process is crucial for achieving the desirable quality and productivity. For this work, an experimental investigation is carried out to determine the processing window that yields optimal quality for two types of material: High tack …
Machine Learning Methods For Rapid Inspection Of Automated Fiber Placement Manufactured Composite Structures, Christopher Sacco
Machine Learning Methods For Rapid Inspection Of Automated Fiber Placement Manufactured Composite Structures, Christopher Sacco
Theses and Dissertations
The advanced manufacturing capabilities provided through the automated fiber placement (AFP) system has allowed for faster layup time and more consistent production across a number of different geometries. This contributes to the modern production of large composite structures and the widespread adaptation of composites in industry in general and aerospace in particular. However, the automation introduced in this process increases the difficulty of quality assurance efforts and inspection. The AFP process can induce a number of manufacturing defects including wrinkles, twists, gaps, and overlaps. The manual identification of these defects is often laborious and requires a measure of expert knowledge. …
Point Cloud Based Relative Navigation For Small Satellite Rendezvous, Branden William Blackwell
Point Cloud Based Relative Navigation For Small Satellite Rendezvous, Branden William Blackwell
Theses and Dissertations
The thesis describes the development and testing of a point cloud based relative navigation sensor. The objective of this research is to provide a low cost, lightweight, low power, and low volume alternative to established rendezvous sensors , in order to enable small satellites to conduct missions such as in-space inspection, on-orbit servicing, and space debris removal. The sensor system must be able to provide relative position and orientation data to a control system independent of the cooperation of the target spacecraft or object. This is done using commercially available hardware (Microsoft Kinect v2) and an open source C++ library …
A First-Principle Power And Energy Model For Evtol Vehicles, Max Skuhersky
A First-Principle Power And Energy Model For Evtol Vehicles, Max Skuhersky
Theses and Dissertations
A number of well-established aircraft manufacturers, such as Airbus, Boeing, or Bell, along with new startups have begun developing flying prototypes of electric Vertical Takeoff and Landing vehicles (eVTOL). To certify this emerging type of air mobility vehicles for commercial use, the Federal Aviation Administration (FAA) is considering adjusting currently used certification procedures for small aircraft to include eVTOL vehicles. One of the hurdles to this approach is that eVTOL vehicles are neither able to glide like a small, fixed-wing aircraft, nor to autorotate, like a helicopter, if the batteries are depleted. Therefore, active energy management and energy awareness by …
Study Of A Crew Transfer Vehicle Using Aerocapture For Cycler Based Exploration Of Mars, Larissa Balestrero Machado
Study Of A Crew Transfer Vehicle Using Aerocapture For Cycler Based Exploration Of Mars, Larissa Balestrero Machado
Theses and Dissertations
This thesis presents the results of a conceptual design and aerocapture analysis for a Crew Transfer Vehicle (CTV) designed to carry humans between Earth or Mars and a spacecraft on an Earth-Mars cycler trajectory. The thesis outlines a parametric design model for the Crew Transfer Vehicle and presents concepts for the integration of aerocapture maneuvers within a sustainable cycler architecture. The parametric design study is focused on reducing propellant demand and thus the overall mass of the system and cost of the mission. This is accomplished by using a combination of propulsive and aerodynamic braking for insertion into a low …
Continuous Tow Path Generation For Constant And Variable Stiffness Composite Laminates On Single And Double Curved Surfaces, Caleb R. Pupo
Continuous Tow Path Generation For Constant And Variable Stiffness Composite Laminates On Single And Double Curved Surfaces, Caleb R. Pupo
Theses and Dissertations
A novel approach for the generation of steered tow paths on curved shell surfaces is presented. The approach is used to translate optimal theoretical analysis expressed from ply to ply as fiber angle distributions for steered laminates into discrete tow paths on planar, single and double curved surfaces. By adapting the multi mesh approach earlier developed by van Tooren and Elham [1–3] to the new tow path generation code. Two meshes are utilized, a coarse mesh which is generated during the optimization and contains the optimal fiber angle distributions, and a denser mesh obtained from tessellating the surface to better …
Analysis Of Satellite Timing And Navigation Receiver Pseudorange Biases Due To Spreading Code Puncturing And Phase Optimized Constant Envelope Transmission, Nathaniel J. Raquet
Analysis Of Satellite Timing And Navigation Receiver Pseudorange Biases Due To Spreading Code Puncturing And Phase Optimized Constant Envelope Transmission, Nathaniel J. Raquet
Theses and Dissertations
There is a desire for future GPS satellites to be software-defined to enable greater operational flexibility and adapt to a variety of current and future threats. This includes implementing new modulation techniques such as phase optimized constant envelope transmission (POCET) and asymmetric signal authentication methods such as chips message robust authentication (Chimera). Any new GPS signal transmitted must be backwards compatible with the millions of receivers already in use. This thesis shows a variety of tests performed to demonstrate the effects of Chimera and POCET-enabled signals. It is shown through actual radio frequency signal generation, testing the response of current-generation …
Active Control Of A Morphing Wing Aircraft And Failure Analysis For System Reliability, Madison J. Montgomery
Active Control Of A Morphing Wing Aircraft And Failure Analysis For System Reliability, Madison J. Montgomery
Theses and Dissertations
A morphing wing aircraft has the ability to increase the efficiency of an aircraft by better optimizing lift and drag characteristics during a flight. A morphing wing UAV was designed and constructed by AFRL/RQVS and required a means of control and method of characterizing the performance of the aircraft through flight testing. This research presents the design and construction of a control system capable of adjusting the morphing wing shape based on pilot commands and current flight status. The control system was tested and improved following a flight test crash utilizing failure mode analysis.
Piezoelectric Sensor Crack Detection On Airframe Systems, Kevin J. Lin
Piezoelectric Sensor Crack Detection On Airframe Systems, Kevin J. Lin
Theses and Dissertations
In 2008, the Department of Defense published a guidebook for a methodology named Condition-Based Maintenance Plus (CBM+) which capabilities include improving productivity, shortening maintenance cycles, lowering costs, and increasing availability and reliability. This push replaces existing inspection criteria, often conducted as non-destructive testing (NDT), with structural health monitoring (SHM) systems. The SHM system addressed utilizes guided Lamb waves generated by piezoelectric wafer active sensors (PWAS) to detect the existence, size, and location of damage from through-thickness cracks around a rivet hole. The SHM field lacks an experiment testing how small changes in receiver sensor distances affect damage detection. In addition, …
Performance Analysis Of Angle Of Arrival Algorithms Applied To Radiofrequency Interference Direction Finding, Taylor S. Barber
Performance Analysis Of Angle Of Arrival Algorithms Applied To Radiofrequency Interference Direction Finding, Taylor S. Barber
Theses and Dissertations
Radiofrequency (RF) interference threatens the functionality of systems that increasingly underpin the daily function of modern society. In recent years there have been multiple incidents of intentional RF spectrum denial using terrestrial interference sources. Because RF based systems are used in safety-of-life applications in both military and civilian contexts, there is need for systems that can quickly locate these interference sources. In order to meet this need, the Air Force Research Laboratory Weapons Directorate is sponsoring the following research to support systems that will be able to quickly geolocate RF interferers using passive angle-of-arrival estimation to triangulate interference sources. This …
Cyber-Attack Drone Payload Development And Geolocation Via Directional Antennae, Clint M. Bramlette
Cyber-Attack Drone Payload Development And Geolocation Via Directional Antennae, Clint M. Bramlette
Theses and Dissertations
The increasing capabilities of commercial drones have led to blossoming drone usage in private sector industries ranging from agriculture to mining to cinema. Commercial drones have made amazing improvements in flight time, flight distance, and payload weight. These same features also offer a unique and unprecedented commodity for wireless hackers -- the ability to gain ‘physical’ proximity to a target without personally having to be anywhere near it. This capability is called Remote Physical Proximity (RPP). By their nature, wireless devices are largely susceptible to sniffing and injection attacks, but only if the attacker can interact with the device via …
High Resolution Low-Bandwidth Real-Time Reconnaissance Using Structure From Motion With Planar Homography Estimation, Christian M.A. Arnold
High Resolution Low-Bandwidth Real-Time Reconnaissance Using Structure From Motion With Planar Homography Estimation, Christian M.A. Arnold
Theses and Dissertations
Aerial real-time surveillance exists in a paradigm balancing the constraints of delivering high quality data and transporting data quickly. Typically, to have more of one, sacrifices must be made to the other. This is true of the environment in which an Unmanned Aerial Vehicle (UAV) operates, where real-time communication may be done through a low-bandwidth satellite connection resulting in low-resolution data, and serves as the primary limiting factor in all intelligence operations. Through the use of efficient computer vision techniques, we propose a new Structure from Motion (SfM) method capable of compressing high-resolution data, and delivering that data in real-time. …
High Fidelity Satellite Navigation Receiver Front-End For Advanced Signal Quality Monitoring And Authentication, Andrew D. Braun
High Fidelity Satellite Navigation Receiver Front-End For Advanced Signal Quality Monitoring And Authentication, Andrew D. Braun
Theses and Dissertations
Over the last several years, interest in utilizing foreign satellite timing and navigation (satnav) signals to augment GPS has grown. Doing so is not without risks; foreign satnav signals must be vetted and determined to be trustworthy before use in military applications. Advanced signal quality monitoring methods can help to ensure that only authentic and reliable satnav signals are utilized. To effectively monitor and authenticate signals, the front-end must impress as little distortions upon the received signal as possible. The purpose of this study is to design, fabricate, and test the performance of a high-fidelity satnav receiver front-end for advanced …
Convolutional Neural Network Architecture Study For Aerial Visual Localization, Jedediah M. Berhold
Convolutional Neural Network Architecture Study For Aerial Visual Localization, Jedediah M. Berhold
Theses and Dissertations
In unmanned aerial navigation the ability to determine the aircraft's location is essential for safe flight. The Global Positioning System (GPS) is the default modern application used for geospatial location determination. GPS is extremely robust, very accurate, and has essentially solved aerial localization. Unfortunately, the signals from all Global Navigation Satellite Systems (GNSS) to include GPS can be jammed or spoofed. To this response it is essential to develop alternative systems that could be used to supplement navigation systems, in the event of a lost GNSS signal. Public and governmental satellites have provided large amounts of high-resolution satellite imagery. These …
Aerial Simultaneous Localization And Mapping Using Earth's Magnetic Anomaly Field, Taylor N. Lee
Aerial Simultaneous Localization And Mapping Using Earth's Magnetic Anomaly Field, Taylor N. Lee
Theses and Dissertations
Aerial magnetic navigation has been shown to be a viable GPS-alternative, but requires a prior-surveyed magnetic map. The miniaturization of atomic magnetometers extends their application to small aircraft at low altitudes where magnetic maps are especially inaccurate or unavailable. This research presents a simultaneous localization and mapping (SLAM) approach to constrain the drift of an inertial navigation system (INS) without the need for a magnetic map. The filter was demonstrated using real measurements on a professional survey flight, and on an AFIT unmanned aerial vehicle.
Monocular Visual Odometry For Fixed-Wing Small Unmanned Aircraft Systems, Kyung M. Kim
Monocular Visual Odometry For Fixed-Wing Small Unmanned Aircraft Systems, Kyung M. Kim
Theses and Dissertations
The popularity of small unmanned aircraft systems (SUAS) has exploded in recent years and seen increasing use in both commercial and military sectors. A key interest area for the military is to develop autonomous capabilities for these systems, of which navigation is a fundamental problem. Current navigation solutions suffer from a heavy reliance on a Global Positioning System (GPS). This dependency presents a significant limitation for military applications since many operations are conducted in environments where GPS signals are degraded or actively denied. Therefore, alternative navigation solutions without GPS must be developed and visual methods are one of the most …
Verification Of Autonomous Systems: Developmental Test And Evaluation Of An Autonomous Uas Swarming Algorithm Combining Simulation, Formulation And Live Flight, Corey A. Combs
Theses and Dissertations
This research was driven by the increase of autonomous systems in the current millennium and the challenging nature of testing and evaluating their performance. A review of the current literature revealed proposed methods for verifying autonomous systems, but few implementations. It exposed several gaps in the current verification and validation methods and suggested goals for filling them. Through the use of modeling, software in the loop (SITL), and flight test, this research verified an autonomous swarming algorithm for unmanned aerial systems (UAS) and validated an exemplar of a testing framework. Thirteen sets of three-vehicle swarm data produced over two days …
Search-Based Vs. Task-Based Space Surveillance For Ground-Based Telescopes, Fred D. Hertwig
Search-Based Vs. Task-Based Space Surveillance For Ground-Based Telescopes, Fred D. Hertwig
Theses and Dissertations
Persistent Space Situational Awareness (SSA) is one of the top priorities of the DoD. Currently the Space Surveillance Network (SSN) operates using only a task-based method. The goal of this thesis was to compare the current task-based space surveillance performance to a search-based method of space surveillance in the GEO belt region. The performance of a ground telescope network, similar to the Ground-Based Electro-Optical Deep Space Surveillance (GEODSS) network, was modeled and simulated using AGI’s Systems Tool Kit (STK) and Python. The model compared search-based and task-based space surveillance methods by simulating 813 Resident Space Objects (RSOs) on the summer …
A Mixed Integer Programming Framework For The Fuel Optimal Guidance Of Complex Spacecraft Rendezvous And Proximity Operation Missions, Andrew S. Levalley
A Mixed Integer Programming Framework For The Fuel Optimal Guidance Of Complex Spacecraft Rendezvous And Proximity Operation Missions, Andrew S. Levalley
Theses and Dissertations
Space is a contested, congested, and competitive environment where space situational awareness (SSA) is a key factor in the long term sustainability of space as a national interest. Space-based SSA conducted by inspector satellites is critical to the detecting, tracking, and attribution of actions in space. Thus, space-based fuel-optimal maneuvers are essential to increasing mission life and improving the capability of inspector satellites working to characterize resident space objects (RSOs) in geosynchronous orbit (GEO). Additionally, on-orbit inspection missions can be characterized by multiple waypoint visits where an inspector is accomplishing a set of proximity operation mission objectives through the visit …
Simulation And Piloted Simulator Study Of An Automatic Ground Collision Avoidance System For Performance Limited Aircraft, James D. Carpenter
Simulation And Piloted Simulator Study Of An Automatic Ground Collision Avoidance System For Performance Limited Aircraft, James D. Carpenter
Theses and Dissertations
The F-16 Automatic-Ground Collision Avoidance System (Auto-GCAS) has been a resounding success since implementation in Nov 2014, saving 8 pilots and 7 aircraft from Controlled Flight into Terrain (CFIT). However, there is no implemented Auto- GCAS for "heavy" performance limited aircraft. This research endeavors to expand on the success of F-16 Auto-GCAS to other aircraft in the Air Force inventory such as the C-130, C-17, and B-1. MIL-STD-1797 classifies performance limited aircraft as large, heavy, and low to medium maneuverability. Using a stitched Learjet-25D model (LJ-25D), an Auto-GCAS algorithm was developed to predict multiple escape-maneuver trajectories, compare these paths to …
Optimal And Robust Neural Network Controllers For Proximal Spacecraft Maneuvers, B. Cole George
Optimal And Robust Neural Network Controllers For Proximal Spacecraft Maneuvers, B. Cole George
Theses and Dissertations
Recent successes in machine learning research, buoyed by advances in computational power, have revitalized interest in neural networks and demonstrated their potential in solving complex controls problems. In this research, the reinforcement learning framework is combined with traditional direct shooting methods to generate optimal proximal spacecraft maneuvers. Open-loop and closed-loop feedback controllers, parameterized by multi-layer feed-forward artificial neural networks, are developed with evolutionary and gradient-based optimization algorithms. Utilizing Clohessy- Wiltshire relative motion dynamics, terminally constrained fixed-time, fuel-optimal trajectories are solved for intercept, rendezvous, and natural motion circumnavigation transfer maneuvers using three different thrust models: impulsive, finite, and continuous. In addition …
Flow Behavior In Radial Rotating Detonation Engines, Scott A. Boller
Flow Behavior In Radial Rotating Detonation Engines, Scott A. Boller
Theses and Dissertations
Recent progress has been made in demonstrating Radial Rotating Detonation Engine (RRDE) technology for use in a compact Auxiliary Power Unit with a rapid response time. Investigation of RRDEs also suggests an increase in stable operating range, which is hypothesized to be due to the additional degree of freedom in the radial direction which the detonation wave can propagate. This investigation seeks to determine if the detonation wave is in fact changing its radial location. High speed photography was used to capture chemiluminescence of the detonation wave within the channel to examine its radial location, which was found to vary …