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Articles 31 - 48 of 48
Full-Text Articles in Engineering
Simulation Of Locking Space Truss Deployments For A Large Deployable Sparse Aperture Reflector, Dylan M. Van Dyne
Simulation Of Locking Space Truss Deployments For A Large Deployable Sparse Aperture Reflector, Dylan M. Van Dyne
Theses and Dissertations
Large deployable space structures require an inordinate amount of effort to fully design and test on Earth. To aid in the determination of the feasibility of the reflector, a method to simulate the structure's deployment was developed using COMSOL. The simulation model is comprised of a locking hinge truss that constitutes the partial reflector structure. To meet computational and temporal restrictions, the structure is simplified to use simple beams with square cross sections and is meshed to a sufficient accuracy with second order elements. The geometry is modeled in the truss's stowed configuration, with the connecting hinges and applied forces …
Advancements Of In-Flight Mass Moment Of Inertia And Structural Deflection Algorithms For Satellite Attitude Simulators, Jonathan W. Wright
Advancements Of In-Flight Mass Moment Of Inertia And Structural Deflection Algorithms For Satellite Attitude Simulators, Jonathan W. Wright
Theses and Dissertations
Experimental satellite attitude simulators have been used to test and analyze control algorithms; driving down risk before implementation on operational satellites. Ideally, the dynamic response of a terrestrial-based experimental satellite attitude simulator matches that of an on-orbit satellite. Unfortunately, gravitational disturbance torques and poorly characterized moments of inertia introduce uncertainty into the system dynamics leading to questionable experimental results. This research consists of three distinct, but related contributions to the field of developing robust satellite attitude simulators. First, existing approaches to estimate mass moments and products of inertia are evaluated followed by a proposition and evaluation of a new approach …
Precision Relative Positioning For Automated Aerial Refueling From A Stereo Imaging System, Kyle P. Werner
Precision Relative Positioning For Automated Aerial Refueling From A Stereo Imaging System, Kyle P. Werner
Theses and Dissertations
The United States Air Force relies upon aerial refueling to fulfill its missions. Unmanned aerial systems (UAS) and remotely piloted aircraft (RPA) do not currently have access to this capability due to the lack of an on-board pilot to safely maintain a refueling position. This research examines stereo vision for precision relative navigation in order to accomplish the Automated Aerial Refueling (AAR) task. Previous work toward an AAR solution has involved the use of Differential Global Positioning (DGPS), Light Detection and Ranging (LiDAR), and monocular vision. This research aims to leverage organic systems in future aircraft to compliment these solutions. …
Error Characterization Of Flight Trajectories Reconstructed Using Structure From Motion, Daniel C. Alix
Error Characterization Of Flight Trajectories Reconstructed Using Structure From Motion, Daniel C. Alix
Theses and Dissertations
This research effort assessed the accuracy of Structure from Motion (SFM) algorithms in replicating aircraft fight trajectories. Structure from Motion techniques can be used to estimate aircraft trajectory by determining the position and pose of an aircraft mounted camera from a sequential series of images taken during flight. An algorithm is proposed and implemented that successfully reconstructed aircraft trajectory using only a known starting position and a sequential series of images. The error in and reliability of the algorithm was found to be a function of image resolution as well as the amount of overlap and angular separation between sequential …
Optimal Recovery Trajectories For Automatic Ground Collision Avoidance Systems (Auto Gcas), Angela W. Suplisson
Optimal Recovery Trajectories For Automatic Ground Collision Avoidance Systems (Auto Gcas), Angela W. Suplisson
Theses and Dissertations
The USAF's F-16 Automatic Ground Collision Avoidance System (Auto GCAS) uses a single pre-planned roll to wings- level and 5-g pull-up to meet the operational requirements of being both aggressive and timely, meaning that extremely agile avoidance maneuvers will be executed at the last second to avoid the ground. There currently exists no similar Auto GCAS for manned military heavy' aircraft with lower climb performance such as transport, tanker, or bomber aircraft. This research proposes a new optimal control approach to the ground collision avoidance problem for heavy aircraft by mapping the aggressive and timely requirements of the automatic recovery …
The Cognition Of Multiaircraft Control (Mac): Cognitive Ability Predictors, Working Memory, Interference, And Attention Control In Radio Communication, Kelly M. Amaddio
The Cognition Of Multiaircraft Control (Mac): Cognitive Ability Predictors, Working Memory, Interference, And Attention Control In Radio Communication, Kelly M. Amaddio
Theses and Dissertations
As the number of U.S. Air Force missions requiring UAVs has rapidly increased without commensurate increases in manpower, systems which permit a single operator to supervise and control multiple, highly-automated aircraft are being considered. The operator of such a system may be required to monitor and respond to voice communications for multiple UAVs, each of which can have aircraft specific call signs. The need to monitor this array of call signs may impose excessive requirements on constrained operator attention, working memory, and cognitive processing. The current research investigates the cognitive load (number of aircraft call signs) an individual can handle …
Low Earth Orbit Satellite Tracking Telescope Network: Collaborative Optical Tracking For Enhanced Space Situational Awareness, Victor A. Salvador
Low Earth Orbit Satellite Tracking Telescope Network: Collaborative Optical Tracking For Enhanced Space Situational Awareness, Victor A. Salvador
Theses and Dissertations
The Air Force Institute of Technology has spent the last seven years conducting research on orbit identification and object characterization of space objects through the use of commercial-off-the-shelf hardware systems controlled via custom software routines, referred to simply as TeleTrak. Year after year, depending on the research objectives, students have added or modified the system's hardware and software to achieve their individual research objectives. In the last year, due to operating system and software upgrades, TeleTrak became inoperable. Furthermore, due to a lack of student overlap, knowledge of the basic operation of the TeleTrak deteriorated. This research re-establishes the basic …
Methods Of Measuring Stress Relaxation In Composite Tape Springs, Justin T. Heppe
Methods Of Measuring Stress Relaxation In Composite Tape Springs, Justin T. Heppe
Theses and Dissertations
Composite tape springs present an opportunity to use stored energy for the deployment of space structures. Concern has risen over the dissipation of strain energy during storage due to viscoelasticity inherent in polymeric materials commonly used as the composite matrix. Tests to measure the internal behavior of a composite tape spring over time are conducted along with methods of analyzing and fitting the resulting data. The three constant strain configurations tested were compression force of the cross section, a restraining force of a longitudinal fold, and the change in shape of a folded section. While the shape changing test did …
Reflections Of A Wave: An Analysis Of Photonic Doppler Velocimetry Systems, Brian K. Lagrange
Reflections Of A Wave: An Analysis Of Photonic Doppler Velocimetry Systems, Brian K. Lagrange
Theses and Dissertations
Munitions are one of the Air Force's most effective weapons in eliminating targets, but also one of the most expensive. Due to the inherent high-cost in deploying munitions, munition shock wave detonation must be better observed and quantified for munitions to be more cost-efficient. PDV systems have the potential to achieve this quantification of shock wave properties on a molecular scale during solid-against-solid impacts. The overall goal of this research was to determine whether the current photonic Doppler velocimetry (PDV) system at Eglin Air Force Base is prepared for future explosive sensitivity testing. This determination was done through an uncertainty …
A Monocular Slam Method To Estimate Relative Pose During Satellite Proximity Operations, Scott J. Kelly
A Monocular Slam Method To Estimate Relative Pose During Satellite Proximity Operations, Scott J. Kelly
Theses and Dissertations
Automated satellite proximity operations is an increasingly relevant area of mission operations for the US Air Force with potential to significantly enhance space situational awareness (SSA). Simultaneous localization and mapping (SLAM) is a computer vision method of constructing and updating a 3D map while keeping track of the location and orientation of the imaging agent inside the map. The main objective of this research effort is to design a monocular SLAM method customized for the space environment. The method developed in this research will be implemented in an indoor proximity operations simulation laboratory. A run-time analysis is performed, showing near …
Characterization And Modeling Of A Control Moment Gyroscope, Dylan R. Penn
Characterization And Modeling Of A Control Moment Gyroscope, Dylan R. Penn
Theses and Dissertations
The Air Force Research Laboratory (AFRL) is developing a spacecraft simulator that uses Control Moment Gyroscopes (CMGs). Prior to the research herein, the Air Force Institute of Technology (AFIT) designed and built six laboratory-rated CMGs for use on the AFRL spacecraft simulator. The main contributions of this research are in the testing and modeling of a single CMG. Designing, building, and operating spacecraft simulators is time consuming and expensive, but less so than tests with on-orbit spacecraft. Reductions in cost and schedule can be realized by investing in modeling the spacecraft simulator and payload before testing. A model of the …
Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser
Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser
Theses and Dissertations
Tension-compression fatigue behavior of an oxide-oxide ceramic matrix composite was investigated at 1200°C in air and steam. The composite is comprised of an alumina matrix reinforced with Nextel 720 fibers woven in an eight harness satin weave. The composite relies on a porous matrix for damage tolerance. Compression and tension tests to failure were conducted to characterize basic mechanical properties. Tension-compression fatigue tests were performed at 1 Hz frequency with a ratio of minimum to maximum stress of -1. Maximum stresses ranged from 60-120 MPa. Fatigue run-out (defined as 105 cycles) was achieved in air at 80 MPa and in …
Computer Modeling Of A Rotating Detonation Engine In A Rocket Configuration, Nihar Shah
Computer Modeling Of A Rotating Detonation Engine In A Rocket Configuration, Nihar Shah
Theses and Dissertations
Detonation-based combustors leverage the higher thermodynamic efficiency of the Atkinson cycle compared to the traditional deflagration-based combustion of the Brayton cycle. The rotating detonation engine (RDE) has one or more shock waves rotating around an annulus. The RDE can theoretically be 20% more thermally efficient than a traditional deflagration-based cycle. A RDE was modeled in Numerical Propulsion System Simulation (NPSS) based on a model developed in Microsoft Excel. The thermodynamic analysis of the RDE in these models is broken into four streams. Empirical models were used to find the percentage of the total flow in each stream. The pre-detonation pressure …
Characterization Of A Robotic Manipulator For Dynamic Wind Tunnel Applications, James C. Lancaster
Characterization Of A Robotic Manipulator For Dynamic Wind Tunnel Applications, James C. Lancaster
Theses and Dissertations
The newly acquired 6-DOF Motion Test Apparatus (MTA) was installed to perform dynamic wind tunnel testing in the AFIT Low Speed Wind Tunnel. Several complex motions revealed that the overall performance of the test rig needed improvement especially during small motions. The motions exposed that further enhancements would need to be performed individually for each joint. This research effort focused on the improvement of the MTA wrist roll motor and controller using a pitch oscillation. The controller software was improved using position feedback because the MTA wrist roll motor and controller exhibited reduced signal bias and amplitude attenuation. The enhanced …
Mechanical Testing Of Ultra-High Temperature Ceramics At 1500°C In Air -Development Of An Experimental Facility And Test Method, Sheena L. Winder
Mechanical Testing Of Ultra-High Temperature Ceramics At 1500°C In Air -Development Of An Experimental Facility And Test Method, Sheena L. Winder
Theses and Dissertations
With a melting point in excess of 3000°C and a high density, ultra-high temperature ceramics (UHTCs) are a candidate material for hypersonic flight vehicles, atmospheric re-entry vehicles, and rocket propulsion systems. When ceramics are under consideration as a structural material, creep is an important design criterion and a life-limiting condition. However, the characterization of mechanical behavior at temperatures in excess of 1300°C has many challenges to overcome. Of utmost importance is the selection of materials for test fixtures. Materials selected must maintain their structural integrity, not cause chemical degradation of the test material, and not interfere with the acquisition of …
Pilot Assisted Inertial Navigation System Aiding Using Bearings-Only Measurements Taken Over Time, Anthony T. Mirabile
Pilot Assisted Inertial Navigation System Aiding Using Bearings-Only Measurements Taken Over Time, Anthony T. Mirabile
Theses and Dissertations
The objective of this work is to develop an alternative INS aiding source other than the GPS, while preserving the autonomy of the integrated navigation system. It is proposed to develop a modernized method of aerial navigation using driftmeter measurements from an E/O system for ground feature tracking, and an independent altitude sensor in conjunction with the INS. The pilot will track a ground feature with the E/O system, while the aircraft is on autopilot holding constant airspeed, altitude, and heading during an INS aiding session. The ground feature measurements from the E/O system and the INS output form measurements …
Modeling Navigation System Performance Of A Satellite-Observing Star Tracker Tightly Integrated With An Inertial Measurement Unit, Scott J. Pierce
Modeling Navigation System Performance Of A Satellite-Observing Star Tracker Tightly Integrated With An Inertial Measurement Unit, Scott J. Pierce
Theses and Dissertations
This dissertation evaluates a navigation system using satellite observations from a star tracker tightly-integrated with an inertial measurement unit (IMU) and a barometric altimeter using an extended Kalman filter. The star tracker measurement accuracy of a satellite is derived. Several system configurations are simulated comparing the performance of the estimate with respect to system parameters of the IMU, and star tracker, as well as comparing performance when providing a remote sensor satellite ephemeris error correction. Experimental observations are used to evaluate the model performance. Additionally, power requirements were calculated for a satellite signal operating in imaging bands, such that a …
On The Integration Of Medium Wave Infrared Cameras For Vision-Based Navigation, Justin S. Tharp
On The Integration Of Medium Wave Infrared Cameras For Vision-Based Navigation, Justin S. Tharp
Theses and Dissertations
The ubiquitous nature of GPS has fostered its widespread integration of navigation into a variety of applications, both civilian and military. One alternative to ensure continued flight operations in GPS-denied environments is vision-aided navigation, an approach that combines visual cues from a camera with an inertial measurement unit (IMU) to estimate the navigation states of a moving body. The majority of vision-based navigation research has been conducted in the electro-optical (EO) spectrum, which experiences limited operation in certain environments. The aim of this work is to explore how such approaches extend to infrared imaging sensors. In particular, it examines the …