Design And Analysis Of Air-Stiffened Vacuum Lighter-Than-Air Structures,
2021
Air Force Institute of Technology
Design And Analysis Of Air-Stiffened Vacuum Lighter-Than-Air Structures, Ruben Adorno-Rodriguez
Theses and Dissertations
Lighter-than-air (LTA) systems have been developed for numerous applications and have taken several forms. Airships, aerostats, blimps, and balloons are all part of this family of systems, which uses Archimedes principle to achieve neutral and positive buoyancy in air by replacing an air volume with LTA gases. These lifting gases stiffen the otherwise compliant envelope structures, allowing them to sustain the pressure difference brought by the displaced air. The compliance of these structures is a byproduct of the weight requirement, materials and geometrical arrangement of which these structures are built from, typically resulting in dimensionalities that exhibit low or virtually …
Applied Reachability Analysis For Time-Optimal Spacecraft Attitude Reorientations,
2021
Air Force Institute of Technology
Applied Reachability Analysis For Time-Optimal Spacecraft Attitude Reorientations, Layne C. Barrett
Theses and Dissertations
Satellite attitude reorientation has been of significant interest in astronautical engineering, and being able to reorient in a time-optimal manner has been of exceeding interest since the 1970s. Ensuring a spacecraft mission set can be conducted within a certain amount of time begs the question of whether or not a certain maneuver can be completed with a bounded control. This thesis answers that question by using the concept of reachability to provide reachable sets for different spacecraft reorientation scenarios. The reachable sets generated provide a range of initial states that guarantee a satellite reach a desired end orientation given a …
Deep Reinforcement Learning Applied To Spacecraft Attitude Control And Moment Of Inertia Estimation Via Recurrent Neural Networks,
2021
Air Force Institute of Technology
Deep Reinforcement Learning Applied To Spacecraft Attitude Control And Moment Of Inertia Estimation Via Recurrent Neural Networks, Nathaniel A. Enders
Theses and Dissertations
This study investigated two distinct problems related to unknown spacecraft inertia. The first problem explored the use of a recurrent neural network to estimate spacecraft moments of inertia using angular velocity measurements. Initial results showed that, for the configuration examined, the neural network can estimate the moments of inertia when there is a known external torque. The second problem trained a reinforcement learning agent, via proximal policy optimization, to control the attitude of a spacecraft. The results demonstrated that reinforcement learning may be a viable option for guidance and control solutions where the spacecraft model may be unknown. The trained …
A Reduced Order Model Of The Celestial Icosahedron As The Substructure For A Lighter Than Air Vehicle,
2021
Air Force Institute of Technology
A Reduced Order Model Of The Celestial Icosahedron As The Substructure For A Lighter Than Air Vehicle, Torin C. Quick
Theses and Dissertations
A finite element approach was used to investigate a novel reduced order model to determine the minimum structure dimensionality to support vacuum for a VLTAV. This modeling technique represented the individual segments of the substructure as curved beams with clamped radially-resisted boundary conditions. The full structure was then modeled as a bare structure and structure with skin to validate the results of the reduced order model. The beam geometry for the material Ultem 9085 was determined through this process leading to the 3-D printing of the structure. It was then experimentally tested under uniaxial compression complimented with a FEA model.
Safe Spacecraft Rendezvous And Proximity Operations Via Reachability Analysis,
2021
Air Force Institute of Technology
Safe Spacecraft Rendezvous And Proximity Operations Via Reachability Analysis, Paul A. Grossi
Theses and Dissertations
The rapid expansion of the utilization of space by nations and industry has presented new challenges and opportunities to operate efficiently and responsibly. Reachability analysis is the process of computing the set of states that can be reached given all admissible controls and can be a valuable component in an autonomous mission planning system if conducted efficiently. In the current research, reachability analysis is used with several relative motion models to show that all ranges of orbits can be computed in milliseconds, and that it is a feasible approach for on-board autonomous mission planning. Reachability analysis is then combined with …
Improving Manufacturability And Reducing Cracking In Additively Manufactured Tungsten Alloys,
2021
Air Force Institute of Technology
Improving Manufacturability And Reducing Cracking In Additively Manufactured Tungsten Alloys, Christopher P. Fassio
Theses and Dissertations
Additively Manufactured tungsten suffers from low () densities due to high concentrations of microcracks as the printed layers cool past tungsten's high ductile to brittle transition temperature. In this study, tungsten-rhenium and tungsten rhenium hafnium carbide compositions were evaluated on density and tensile strength. In addition to varying the compositions of each alloy, printing parameters and post-processing methods were also compared. Print parameters varied for all compositions on an MLab 200R C using included the laser scan strategy, hatch spacing, scan speed, laser power, and print bed material. Post processing techniques of the WRe compositions included hot isostatic pressing and …
Gps-Denied Localization Of Daughter-Ships In A Mother-Daughter Ship Collaborative Environment,
2021
Air Force Institute of Technology
Gps-Denied Localization Of Daughter-Ships In A Mother-Daughter Ship Collaborative Environment, Ethan W. Jacquin
Theses and Dissertations
This research investigates the possibility of using the communication link between a mothership and daughter-ship UAV and an Extended Kalman Filter algorithm as a replacement of GPS, assuming a ranging link exists between the mothership and daughter-ship and that the mothership is GPS-enabled. A simulation study examines the viability of the approach and the effect of parameters such as distance, altitude, roll angle, speed, ranging sensor noise, and inertial measurement unit uncertainty were considered. The magnitude of the errors between predicted and measured position were examined and a range of acceptable flight parameters was formed.
Real-Time Aerial Magnetic And Vision-Aided Navigation,
2021
Air Force Institute of Technology
Real-Time Aerial Magnetic And Vision-Aided Navigation, Daniel J. Clarke
Theses and Dissertations
Aerial magnetic navigation has shown to be a viable alternative navigation method that has the potential for world-wide availability, to include over oceans. Obtaining GPS-level accuracy using magnetic navigation alone is challenging, but magnetic navigation can be combined with other alternative navigation methods that are more posed to obtaining GPS-level accuracy in their current state. This research presents an aerial navigation solution combining magnetic navigation and vision-aided navigation to aid an inertial navigation system (INS). The navigation solution was demonstrated in real-time playback using simulated magnetic field measurements and flight-test captured visual imagery. Additionally, the navigation solution was flight-tested on …
Automated Find Fix And Track With A Medium Altitude Long Endurance Remotely Piloted Aircraft,
2021
Air Force Institute of Technology
Automated Find Fix And Track With A Medium Altitude Long Endurance Remotely Piloted Aircraft, Aubrey L. Olson
Theses and Dissertations
A limitation in RPA ISR operations is loss of target track if the command link is severed. For an RPA to effectively execute the ISR mission without a command link, it needs the capability to F2T targets autonomously. Automated Find Fix and Track (AFFTRAC) was developed to help solve this problem by demonstrating a proof of concept tactical autopilot. Monocular stereo vision was used to process sequential images acquired during orbit to produce a partial structural point cloud of the original structure. This partial structural point cloud was then exploited to create a holding area density for the aircraft to …
Impendance Probe Payload Development For Space-Based Joint Service Collaboration,
2021
Air Force Institute of Technology
Impendance Probe Payload Development For Space-Based Joint Service Collaboration, Brian T. Kay
Theses and Dissertations
Collaborations utilizing small spacecraft in near earth orbit between the U. S. Coast Guard Academy (CGA), Naval Research Lab (NRL), the U. S. Naval Academy (USNA), and the Air Force Institute of Technology (AFIT) have initiated scientific and engineering space-based experiments. Sourced opportunities like the VaSpace ThinSat missions have provided a platform for payload, sensor, and experiment development that would have otherwise been resource prohibitive. We have constructed an impedance probe payload derived from the existing ‘Space PlasmA Diagnostic suitE’ (SPADE) mission operating from NASA’s International Space Station. Currently both space and laboratory plasmas are investigated with AC impedance measurements …
Modeling Situation Awareness In A Uav Scenario Using Sysml,
2021
Air Force Institute of Technology
Modeling Situation Awareness In A Uav Scenario Using Sysml, Tommy R. Hernandez
Theses and Dissertations
The U.S. Department of Defense (DoD) is rapidly moving towards using increasingly automated systems. Unmanned Aerial Systems (UAS) will be used in contested environments where direct human control may be impossible for long stretches of time. This increase in automation brings with it challenges in maintaining resilient Situation Awareness (SA) for operators, who still need to set goals for the UAS to accomplish their missions. Simultaneously, the DoD is increasing the adoption of Model-Based Systems Engineering (MBSE) in the development of weapon systems. This thesis explores the use of SysML to model of an SA repair system for a UAS …
Neuromorphic Vision Sensors For Space-Based Applications,
2021
Air Force Institute of Technology
Neuromorphic Vision Sensors For Space-Based Applications, Jessica L. Horn
Theses and Dissertations
This research examines the viability of event-based vision (neuromorphic) sensors for future use on satellites. Outputting single pixel events only when a change in intensity is detected, event-based vision sensors offer a potential low power, low latency, high temporal resolution, and high dynamic range solution as compared to traditional CCD or CMOS camera technology. The commercial off-the-shelf DVS240C sensor, is analyzed to determine if operability is affected by launch conditions and the low Earth space environment through vacuum, thermal vacuum, and vibration tests. No appreciable changes in sensor operation was observed throughout testing. Additionally, the sensor was able to detect …
Adaptive Augmentation Of Non-Minimum Phase Flexible Aerospace Systems,
2021
Embry-Riddle Aeronautical University
Adaptive Augmentation Of Non-Minimum Phase Flexible Aerospace Systems, Michael A. Dupuis
Doctoral Dissertations and Master's Theses
This work demonstrates the efficacy of direct adaptive augmentation on a robotic flexible system as an analogue of a large flexible aerospace structure such as a launch vehicle or aircraft. To that end, a robot was constructed as a control system testbed. This robot, named “Penny,” contains the command and data acquisition capabilities necessary to influence and record system state data, including the flex states of its flexible structures. This robot was tested in two configurations, one with a vertically cantilevered flexible beam, and one with a flexible inverted pendulum (a flexible cart-pole system). The physical system was then characterized …
Time-Dependent System Reliability Analysis With Second-Order Reliability Method,
2021
Missouri University of Science and Technology
Time-Dependent System Reliability Analysis With Second-Order Reliability Method, Hao Wu, Zhangli Hu, Xiaoping Du
Mechanical and Aerospace Engineering Faculty Research & Creative Works
System reliability is quantified by the probability that a system performs its intended function in a period of time without failures. System reliability can be predicted if all the limit-state functions of the components of the system are available, and such a prediction is usually time consuming. This work develops a time-dependent system reliability method that is extended from the component time-dependent reliability method using the envelope method and second-order reliability method. The proposed method is efficient and is intended for series systems with limit-state functions whose input variables include random variables and time. The component reliability is estimated by …
Cislunar Debris Propagation Following A Catastrophic Spacecraft Mishap,
2021
Air Force Institute of Technology
Cislunar Debris Propagation Following A Catastrophic Spacecraft Mishap, Nathan R. Boone
Theses and Dissertations
This research involves theoretical analysis of the short- and long-term motion of space debris in cislunar trajectories following a spacecraft catastrophic mishap. Specifically, the research formulates a debris propagation model using four-body dynamics and determines debris trajectories following breakup events for a variety of different initial orbital positions. A spacecraft survivability model is then used to quantify the risks from the debris to other cislunar spacecraft. First, a study of the risks due to natural debris comprising the Kordylewski clouds at the Earth-Moon ��4 and ��5 Lagrange points is conducted as an introduction to cislunar debris propagation. Next, …
Hybridized Spacecraft Attitude Control Via Reinforcement Learning Using Control Moment Gyroscope Arrays,
2021
Air Force Institute of Technology
Hybridized Spacecraft Attitude Control Via Reinforcement Learning Using Control Moment Gyroscope Arrays, Cecily C. Agu
Theses and Dissertations
Machine learning techniques in the form of reinforcement learning (RL) can solve complex nonlinear problems found within spacecraft attitude determination and control systems (ADCS). Three CMG arrays were implemented in two simulated spacecraft environments using a reinforcement learning controller. The performance of the controllers were evaluated using target profiles from traditional control law implementations, singularity measure, and variable initial state values. The current research demonstrates that while RL techniques can be implemented, further exploration is needed to investigate the operational efficacy of an approach for producing comparable performance attributes with respect to traditional control laws.
Satellite Tracking With Neuromorphic Cameras For Space Domain Awareness,
2021
Air Force Institute of Technology
Satellite Tracking With Neuromorphic Cameras For Space Domain Awareness, Joseph G. Bacon Jr.
Theses and Dissertations
A significant number of objects orbit the space around Earth. Each of these objects, be it debris, a functioning satellite, or even a staffed space station, circle the planet at extreme speeds relative to most objects on the Earth's surface. Any collision would result in disaster thanks to the extreme amount of kinetic energy involved. Space Domain Awareness (SDA) includes the detection, identification, cataloging, and tracking of orbiting objects to prevent such catastrophes. SDA is maintained in multiple ways to include radar, lidar, telescopes, and other sensors. This research investigates the maturing technology of neuromorphic cameras to determine their applicability …
Cubesat Attitude Determination And Control System (Adacs) Characterization And Testing For Rendezvous And Proximity Operations (Rpo),
2021
Air Force Institute of Technology
Cubesat Attitude Determination And Control System (Adacs) Characterization And Testing For Rendezvous And Proximity Operations (Rpo), Steven T. Bednarski
Theses and Dissertations
This research endeavors to evaluate and characterize the performance of CubeSat specific commercial-off-the-shelf (COTS) Attitude Determination and Control Systems (ADACS) for Mission suitability. To ensure COTS components are capable of meeting CubeSat mission requirements, deliberate performance testing of critical CubeSat subsystems in flight-like conditions is essential. This effort focuses on testing the MAI-401 ADACS subsystem as configured to support the Grissom-1 CubeSat mission, as mounted to an air bearing, residing within a 3-axis Helmholtz Cage, and subjected to a simulated magnetic environment of various orbital parameters.
Scaling Gas Turbine Film Cooling Adiabatic Effectiveness Through Simultaneous Matching Of Momentum Flux Ratio And Advective Capacity Ratio,
2021
Air Force Institute of Technology
Scaling Gas Turbine Film Cooling Adiabatic Effectiveness Through Simultaneous Matching Of Momentum Flux Ratio And Advective Capacity Ratio, Evan C. Glowiak
Theses and Dissertations
The study of gas turbine engine performance improvement requires extracting usable work from the hot section turbine. To prevent heat damage to turbine blades, film cooling is employed. Low temperature tests are conducted at ambient pressure on scale models to analyze the effects of gas flow parameters on scaling adiabatic effectiveness at easily repeatable conditions. This research aims to determine how matching coolant flow rate parameters Momentum Flux Ratio (I) and Advective Capacity Ratio (ACR) can scale adiabatic effectiveness on flat plate and leading edge geometries between air and carbon dioxide gas. Results indicate improvement in scaling adiabatic effectiveness when …
A Framework For Autonomous Cooperative Optimal Assignment And Control Of Satellite Formations,
2021
Air Force Institute of Technology
A Framework For Autonomous Cooperative Optimal Assignment And Control Of Satellite Formations, Devin E. Saunders
Theses and Dissertations
A decentralized, cooperative multi-agent optimal control framework is presented to offer a solution to the assignment and control problems associated with performing multi-agent tasks in a proximity operations environment. However, the framework developed may be applied to a variety domains such as air, space, and sea. The solution presented takes advantage of a second price auction assignment algorithm to optimally task each satellite, while model predictive control is implemented to control the agents optimally while adhering to safety and mission constraints. The solution is compared to a pseudospectral collocation method, and a study on tuning parameters is included.
