A Molecular Dynamics Study Of Transient Evaporation And Condensation,
2020
Missouri University of Science and Technology
A Molecular Dynamics Study Of Transient Evaporation And Condensation, Zhi Liang, Anirban Chandra, Eric Bird, Pawel Keblinski
Mechanical and Aerospace Engineering Faculty Research & Creative Works
We Use Molecular Dynamics (MD) Simulations to Study the Transient Evaporation and Condensation of a Pure Fluid Ar in a Nanochannel. in the MD Model, the Evaporation and Condensation of Fluid Ar is Initiated by a Sudden Increase of the Temperature or Periodically Varying the Temperature in the Solid Substrate on One Side of the Nanochannel. in Both Cases, We Find the Transient Evaporation and Condensation Rates Obtained Directly from MD Simulations Are in Good Agreement with the Predictions from the Schrage Relationships. Furthermore, Our Analyses Show that the Kinetics of the Transient Heat and Mass Transfer between the Evaporating …
John Houbolt: The Unsung Hero Of The Apollo Moon Landings,
2020
Purdue University
John Houbolt: The Unsung Hero Of The Apollo Moon Landings, William F. Causey
Purdue University Press Book Previews
In May 1961, President Kennedy announced that the United States would attempt to land a man on the moon and return him safely to the earth before the end of that decade. Yet NASA did not have a specific plan for how to accomplish that goal. Over the next fourteen months, NASA vigorously debated several options. At first the consensus was to send one big rocket with several astronauts to the moon, land and explore, and then take off and return the astronauts to earth in the same vehicle. Another idea involved launching several smaller Saturn V rockets into the …
On Controlling Interfacial Heterogeneity To Trigger Bridging In Secondary Bonded Composite Joints: An Efficient Strategy To Introduce Crack-Arrest Features,
2020
Missouri University of Science and Technlogy
On Controlling Interfacial Heterogeneity To Trigger Bridging In Secondary Bonded Composite Joints: An Efficient Strategy To Introduce Crack-Arrest Features, Ran Tao, Xiaole Li, Arief Yudhanto, Marco Alfano, Gilles Lubineau
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Secondary adhesive bonding of carbon fiber-reinforced polymer laminates is of great interest for the aerospace and automotive industries. However, joint reliability is still a major concern because of fabrication-induced or service-related cracks that are difficult to monitor and can lead to catastrophic failure. In this work, we propose a patterning strategy where the careful design of spatially varying interface properties enables the formation of an adhesive ligament that acts as a crack-arrest feature. Bi-dimensional finite element models of adhesively bonded double cantilever beams were employed to investigate the role of the main parameters of the pattern (i.e., geometrical parameters and …
A System Architecture For Phased Development Of Remote Suas Operation,
2020
California Polytechnic State University, San Luis Obispo
A System Architecture For Phased Development Of Remote Suas Operation, Eric Ashley
Master's Theses
Current airspace regulations require the remote pilot-in-command of an unmanned aircraft systems (UAS) to maintain visual line of sight with the vehicle for situational awareness. The future of UAS will not have these constraints as technology improves and regulations are changed. An operational model for the future of UAS is proposed where a remote operator will monitor remote vehicles with the capability to intervene if needed. One challenge facing this future operational concept is the ability for a flight data system to effectively communicate flight status to the remote operator. A system architecture has been developed to facilitate the implementation …
Improved Ground-Based Monocular Visual Odometry Estimation Using Inertially-Aided Convolutional Neural Networks,
2020
Air Force Institute of Technology
Improved Ground-Based Monocular Visual Odometry Estimation Using Inertially-Aided Convolutional Neural Networks, Josiah D. Watson
Theses and Dissertations
While Convolutional Neural Networks (CNNs) can estimate frame-to-frame (F2F) motion even with monocular images, additional inputs can improve Visual Odometry (VO) predictions. In this thesis, a FlowNetS-based [1] CNN architecture estimates VO using sequential images from the KITTI Odometry dataset [2]. For each of three output types (full six degrees of freedom (6-DoF), Cartesian translation, and transitional scale), a baseline network with only image pair input is compared with a nearly identical architecture that is also given an additional rotation estimate such as from an Inertial Navigation System (INS). The inertially-aided networks show an order of magnitude improvement over the …
Microturbine Turbojets: Experimental Evaluation Of Commercially Available Engines,
2020
Air Force Institute of Technology
Microturbine Turbojets: Experimental Evaluation Of Commercially Available Engines, Richard A. Depaola Iii
Theses and Dissertations
This research assessed the performance of commercial microturbine turbojets and was the first industry-wide investigation into this class of engine by AFRL's SERL. Four commercial engines of the same thrust class were evaluated for overall and component-level performance. In addition to providing an evaluation of existing systems, the maximum performance for a commercial turbojet was predicted based on component evaluations. This analysis indicated that a commercial turbojet could have comparable thrust performance to a similarly sized military-grade engine, but it is unlikely that commercial engines can achieve the SFC of military engines without upgrading the compressors found in commercial microturbines.
Design, Development, And Testing Of A Low Cost, Additively-Manufactured, Centrifugal Compressor,
2020
Air Force Institute of Technology
Design, Development, And Testing Of A Low Cost, Additively-Manufactured, Centrifugal Compressor, Aaron P. Bauer
Theses and Dissertations
The three objectives of this research were to: 1.) design, build, and test AM compressors to substitute into COTS micro-gas turbine engines, 2.) provide initial correlations between FEA and compressor failure speed, and 3.) characterize the effects of AM on compressor performance. These goals improved the design cycle cost and the design-validation time cycle. ULTEM 9085, 300-AMB, and Onyx-Kevlar temperature-dependent tensile properties were measured. FEA-predicted failure speeds of stock compressor designs led design improvements, potentially fulfilling the original compressor requirements. Physical testing of the stock and ULTEM 9085 compressors occurred. Comparing these compressors' performances demonstrated that low cost, AM materials …
Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi,
2020
Air Force Institute of Technology
Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi, Daniel Holobeny
Theses and Dissertations
Ultra Compact Combustors are a novel approach to modern gas turbine combustor designs that look to reduce the overall combustor length and weight. A previous study integrated an Ultra Compact Combustor into a JetCat P90 RXi turbine engine and achieved self-sustained operation with a length savings of 33% relative to the stock combustor. However, that combustor could not operate across the full stock engine performance range due to flameout at increased mass ow rates as reactions were pushed out of the primary zone. To ensure reactions stayed in the primary zone, a new design with a larger combustor volume was …
Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion,
2020
Air Force Institute of Technology
Modeling Hybrid Composites Using Tsai-Wu And Hashin Failure Criterion, Candice R. Roberts
Theses and Dissertations
Hybrid composites require further study and testing for future use in various fields. This study focuses on simulating a Hybrid Composite using IM7-977-3 laminae with steel foils in Abaqus under bolt loading by using Hashin and Tsai-Wu failure criterion. Initial simulations contain only the IM7-977-3 composite with cohesive layers. Foil samples were then tested for accurate material properties from which the simulations were then updated to include steel foils. The two models show that Tsai-Wu failure criterion, while great for anisotropic material in tension, does not prove accuracy around the hole of the composite material which is in compression. Hashin …
Design And Analysis Of A Disk-Oriented Engine Combustor,
2020
Air Force Institute of Technology
Design And Analysis Of A Disk-Oriented Engine Combustor, Bennett M. Staton
Theses and Dissertations
In a novel approach to gas-turbine power production, an engine was designed and analyzed to use both a single-stage centrifugal compressor and single-stage radial in- ow turbine configured back-to-back. This air path reduced the axial length of the engine up to 60%, providing additional modularity in a gas-turbine engine that could be used to improve mobility of ground-based power units or increase the survivability of aircraft through the use of distributive propulsion. This increased modularity was made possible by the use of a circumferential ow combustor that substantially decreased the axial length of the burner and negated the need to …
Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam,
2020
Air Force Institute of Technology
Fatigue Behavior Of An Advanced Melt-Infiltrated Sic/Sic Composite With Environmental Barrier Coating At 1200°C In Air And In Steam, Thaddeus M. Williams
Theses and Dissertations
Advanced aerospace applications such as aircraft turbine engine components, hypersonic flight vehicles, and spacecraft reentry thermal protection systems require structural materials that have superior long-term mechanical properties under high temperature, high pressure, and varying environmental factors, such as moisture. Because of their low density, high strength and fracture toughness at high temperatures SiC fiber-reinforced SiC matrix composites are being evaluated for aircraft engine hot-section components. In these applications the composites will be subjected to various types of mechanical loadings at elevated temperatures in oxidizing environments. Because their constituents are intrinsically oxidation-prone, the most significant problem hindering SiC/SiC composites is oxidation …
A Reference Architecture For Cubesat Development,
2020
Air Force Institute of Technology
A Reference Architecture For Cubesat Development, Luke J. Farrell
Theses and Dissertations
Developing a space vehicle is a complex and detailed process, and while CubeSats are smaller and more accessible than traditional satellites the design process is relatively unchanged. Creating a viable space vehicle design requires detailed analysis of a set of mission needs in order to define the mission, with this need set used to then create the specific mission requirements. These requirements are used to formulate a concept of operations, and then move into developing a physical system for executing the mission. The successful production of CubeSats within an organization is contingent upon the accurate execution of the general CubeSat …
Evaluation Framework For Cislunar Space Domain Awareness (Sda) Systems,
2020
Air Force Institute of Technology
Evaluation Framework For Cislunar Space Domain Awareness (Sda) Systems, Simon R. Knister
Theses and Dissertations
Modern space missions are increasingly transiting cislunar space, requiring expansion of existing Space Traffic Management (STM) functions. Legacy Space Domain Awareness (SDA) systems were not purpose-built to detect and track cislunar objects, which could require acquisition of a new system of systems. There are numerous parameters that could be varied for each system, as well as the type and location of systems across the architecture. This research attempts to solve this problem by applying a model-based systems engineering (MBSE) approach to assess the performance and financial burden of a given system of systems. Fitness metrics are developed based upon the …
The Impact Of Changing The Size Of Aircraft Radar Displays On Visual Search In The Cockpit,
2020
Air Force Institute of Technology
The Impact Of Changing The Size Of Aircraft Radar Displays On Visual Search In The Cockpit, Justin R. Marsh
Theses and Dissertations
Advances in sensor technology have enabled our fighter aircraft to find, fix, track, target, engage (F2T2E) at greater distances, providing the operator with more data within the battlefield. Modern aircraft are designed with larger displays while our legacy aircraft are being retrofitted with larger cockpit displays to enable display of the increased data. While this modification has been shown to enable improvements in human performance of many cockpit tasks, this effect is often not measured nor fully understood at a more generalizable level. This research outlines an approach to comparing human performance across two display sizes in future F-16 cockpits. …
Development, Test And Evaluation Of Autonomous Unmanned Aerial Systems In A Simulated Wide Area Search Scenario: An Implementation Of The Autonomous Systems Reference Architecture,
2020
Air Force Institute of Technology
Development, Test And Evaluation Of Autonomous Unmanned Aerial Systems In A Simulated Wide Area Search Scenario: An Implementation Of The Autonomous Systems Reference Architecture, Katherine E. Cheney, David D. King
Theses and Dissertations
The implementation and testing of autonomous and cooperative unmanned systems is challenging due to the inherent design complexity, infinite test spaces, and lack of autonomy specific measures. These challenges are limiting the USAF's ability to deploy and take advantage of tactical and strategic advantages offered by these systems. This research instantiates an Autonomous System Reference Architecture (ASRA) on a Wide Area Search (WAS) scenario as a test bed for rapid prototyping and evaluation of autonomous and cooperative systems. This research aims to pro- vide a framework to evaluate the system’s ability to achieve mission and autonomy objectives, develop reusable autonomous …
Improving Aeromagnetic Calibration Using Artificial Neural Networks,
2020
Air Force Institute of Technology
Improving Aeromagnetic Calibration Using Artificial Neural Networks, Mitchell C. Hezel
Theses and Dissertations
The Global Positioning System (GPS) has proven itself to be the single most accurate positioning system available, and no navigation suite is found without a GPS receiver. Even basic GPS receivers found in most smartphones can easily provide high quality positioning information at any time. Even with its superb performance, GPS is prone to jamming and spoofing, and many platforms requiring accurate positioning information are in dire need of other navigation solutions to compensate in the event of an outage, be the cause hostile or natural. Indeed, there has been a large push to achieve an alternative navigation capability which …
Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles,
2020
Air Force Institute of Technology
Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit
Theses and Dissertations
The commercial-off-the-shelf small Unmanned Aerial Vehicle (UAV) market is expanding rapidly in response to interest from hobbyists, commercial businesses, and military operators. The core commercial mission set directly relates to many current military requirements and strategies, with a priority on short range, low cost, real time aerial imaging, and limited modular payloads. These small vehicles present small radar cross sections, low heat signatures, and carry a variety of sensors and payloads. As with many new technologies, security seems secondary to the goal of reaching the market as soon as innovation is viable. Research indicates a growth in exploits and vulnerabilities …
An Analytic Study Of Pursuit Strategies,
2020
Air Force Institute of Technology
An Analytic Study Of Pursuit Strategies, Mark E. Vlassakis
Theses and Dissertations
The Two-on-One pursuit-evasion differential game is revisited where the holonomic players have equal speed, and the two pursuers are endowed with a circular capture range ℓ > 0. Then, the case where the pursuers' capture ranges are unequal, ℓ1 > ℓ2 ≥ 0, is analyzed. In both cases, the state space region where capture is guaranteed is delineated and the optimal feedback strategies are synthesized. Next, pure pursuit is considered whereupon the terminal separation between a pursuer and an equal-speed evader less than the pursuer's capture range ℓ > 0. The case with two pursuers employing pure pursuit is considered, and …
Semantic Segmentation Of Aerial Imagery Using U-Nets,
2020
Air Force Institute of Technology
Semantic Segmentation Of Aerial Imagery Using U-Nets, Terence J. Yi
Theses and Dissertations
In situations where global positioning systems are unavailable, alternative methods of localization must be implemented. A potential step to achieving this is semantic segmentation, or the ability for a model to output class labels by pixel. This research aims to utilize datasets of varying spatial resolutions and locations to train a fully convolutional neural network architecture called the U-Net to perform segmentations of aerial images. Variations of the U-Net architecture are implemented and compared to other existing models in order to determine the best in detecting buildings and roads. A final dataset will also be created combining two datasets to …
Analysis Of Additively Manufactured Rings Under Compression Loading For Use In A Vacuum Lighter Than Air Vehicle Structure,
2020
Air Force Institute of Technology
Analysis Of Additively Manufactured Rings Under Compression Loading For Use In A Vacuum Lighter Than Air Vehicle Structure, Kevin D. Greenoe
Theses and Dissertations
A Vacuum Lighter Than Air Vehicle (VLTAV) utilizes a lightweight structure paired with an internal vacuum to achieve buoyancy; this allows it to float through-out a given atmosphere. The pressure differential between the internal vacuum andexternal atmosphere places the vehicle under intense loading. A specific structure under investigation is the celestial icosahedron, which features nine intersecting rings that have an outer diameter of 0.2032m and circular cross-sectionalthickness of 5.08mm.The celestials rings are positioned in three different orientations and are analyzed both experimentally and analytically.
