Aerospace Engineering Commons^™

Contingency Planning And An Air Force Space Command Information System, Kaylin Freedman, Michael R. Grimaila

Faculty Publications

No abstract provided.

Managing The Integration Of Space And Information Operations, Daniel F. Gottrich, Michael R. Grimaila

Faculty Publications

No abstract provided.

Numerical Study On Capillarity- Dominant Free Surface And Interfacial Flows, Zhaoyuan Wang

Mechanical and Aerospace Engineering Dissertations - Archive

The continuum surface force (CSF) method has been extensively employed in the volume-of-fluid (VOF), level set (LS) and front tracking methods to model surface tension forces. Its ability is limited for the surface tension dominant free surface and interfacial flows due to the existence of spurious currents. These currents may lead to disastrous interface instabilities and failure of grid convergence, which are present in all the previous versions of the CSF algorithm. In this study, a coupled level set and volume-of-fluid method (CLSVOF) is employed for interface tracking, which offers more accurate computations of the curvature and the normal vector …

Boundary Interference Assessment And Correction For Open Jet Wind Tunnels Using Panel Methods, Wael Ahmed Mokhtar

Mechanical & Aerospace Engineering Theses & Dissertations

The presence of nearby boundaries in a wind tunnel can lead to aerodynamic measurements on a model in the wind tunnel that differ from those that would be made when the boundaries of the moving fluid were infinitely far away. The differences, referred to as boundary interference or wall interference, can be quite large, such as when testing aircraft models developing high lift forces, or whose wingspan is a large fraction of the wind tunnel width, or high drag models whose frontal area is a large fraction of the tunnel cross section. Correction techniques for closed test section (solid walled) …

Impact Simulation And Analysis Of Sandwich Structures, Daewon Kim

Master's Theses - Daytona Beach

Impact damage on aircraft and spacecraft can be a severe problem that may cause catastrophic results. Several aerospace structures have been used to resist or absorb energy in the occasion of impact. Among these, a sandwich structure has advantages with high stiffness, strength to weight ratio, and its relatively cheap cost. However, finding the impact structural response of a sandwich structure, by performing experiments, has disadvantages. First, impact is a complex problem with a multi-parameter nature and many factors should be considered. Secondly, it is a destructive test and the test subject may be damaged during the test. On the …

Improving Efficiency In Engineering Design Using Augmented D-Optimal Designs 'Synthetic Jet' Design Optimization Study, Fatih Erdogan

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this thesis is to study the efficiency of several "design of experiments" (DOE) approaches used for the analysis and optimization of engineering designs. A literature review is conducted to study various "design of experiments" methods and the advantages and limitations of each method are discussed.

As an application, Augmented D-Optimal designs are utilized for a design study of 'synthetic jet'.

With the objective of improving efficiency and providing a minimum point experimental design model, computer-aided D-optimal method is preferred for this study. For setting up the design of the experiments and for performing the analysis of results, …

A Comparative Analysis Of Transmission Control Protocol Improvement Techniques Over Space-Based Transmission Media, Joseph M. Lawson

Theses and Dissertations

The purpose of this study was to assess the throughput improvement afforded by the various TCP optimization techniques, with respect to a simulated geosynchronous satellite system, to provide a cost justification for the implementation of a given enhancement technique. The research questions were answered through model and simulation of a satellite transmission system via a Linux-based network topology; results of the simulation were analyzed primarily via a non-parametric method to ascertain performance differences between the various TCP optimization techniques. It was determined that each technique studied, which included the Space Communication Protocol Standard-Transport Protocol (SCPS-TP), window scale, selective acknowledgements (SACKs), …

Intelligent System Applications Based On Genetic Algorithms, Yasin Volkan Pehlivanoglu

Mechanical & Aerospace Engineering Theses & Dissertations

As a stochastic search method, evolutionary algorithm (EA) is an emergent optimization algorithm mimicking the natural evolution, where a "biological population" evolves over generations to adapt to an environment by selection, recombination, and mutation. When EA is applied to optimization problems, fitness, individual, and genes usually correspond to an objective function value, a design candidate, and design variables, respectively.

One of the key features of EA is that they search from multiple points in design space, instead of moving from a single point as in gradient-based methods. Furthermore, EA works on function evaluations alone and does not require derivatives or …

A Markovian Statistical Analysis Of Single-Event Upsets On Closed-Loop Flight Control Systems, Anushka Vishnukumar Lakdawaia

Electrical & Computer Engineering Theses & Dissertations

The operation of aircrafts depend heavily on closed-loop digital flight control systems which can be disrupted or upset by errant neutrons at aircraft flight altitudes. These upsets, called single-event upsets, range from data corruption to short circuits which can potentially cause physical damage to digital devices and unexpected behaviors in flight controls. Experiments conducted at the Los Alamos Neutron Science Center consisted of irradiating an experimental flight control computer (FCC) architecture with a high intensity neutron beam while the FCC controlled a simulation of a Boeing 737. It was postulated that the upset statistics on the FCC could be fitted …

Space For Project Based Learning Programs, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Space for Project Based Learning Programs" from March 24, 2006.

Assessing The Potential For Improved Scramjet Performance Through Application Of Electromagnetic Flow Control, Martin F. Lindsey

Theses and Dissertations

Hypersonic flight using scramjet propulsion bridges the gap between turbojets and rockets. Recent efforts focus on magnetogasdynamic (MGD) flow control to mitigate the problems of high thermomechanical loads and low efficiencies associated with scramjets. This research is the first flight-scale, three-dimensional computational analysis of a realistic scramjet to assess how MGD flow control improves scramjet performance. Developing a quasi-one dimensional design tool culminated in the first open source scramjet geometry. This geometry was tested with the Air Force Research Laboratory's electromagnetic computational code. To increase fidelity, an algorithm was developed to incorporate thermochemistry, resulting in the only open-source model of …

Design Optimization Of The First Stage Fan Blade Of A Low Bypass Turbofan Engine, Troy James Ramnath

Master's Theses - Daytona Beach

A procedure for solving for and analyzing the aerodynamics, thermodynamics, and blade geometry across the first stage rotor blade under an extreme set of conditions, while altering several design parameters, has been developed and applied. The conditions for which the analyses have been developed were designed for the use of, but not exclusively limited to the application of, military aircraft at altitude. The approach consists of solving for specific key performance parameters across the first stage rotor and analyzing their trends due to the effect of varying other parameters, such as the axial velocity at the rotor's trailing edge, circumferential …

Formation Flight Control For Aerial Refueling, Steven M. Ross

Theses and Dissertations

A controller is designed for an aircraft to autonomously fly formation during aerial refueling. Requirements for a refueling autopilot are stated. A six-degree-of-freedom model is developed for an F-16 lead aircraft and a Learjet LJ-25 wing aircraft. Bare airframe stability of both aircraft is investigated, and stability augmentation is performed. A Matlab Simulink® simulation is built to reproduce the sensor inputs that will be available to the wing aircraft in flight, including disturbances. Control frames are investigated to determine the optimum presentation of the error vector for control during the task of air refueling. Control laws are developed from the …

Characterization Of Pulse Detonation Engine Performance With Varying Free Stream Stagnation Pressure Levels, Wesley R. Knick

Theses and Dissertations

A pulse detonation engine operates on the principle that a fuel-air mixture injected into a tube will ignite and undergo a transition from a deflagration to a detonation and exit the tube at supersonic velocities. Studies in the field of combustion have shown that both ignition time and deflagration to detonation transition time can vary as a function of pressure. It can be hypothesized that if ignition and deflagration to detonation transition times can be reduced by increasing the free stream stagnation pressure level of the tube, it would then be possible to shorten the detonation tube length and increase …

Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt

Theses and Dissertations

There are many situations in which GPS is either unable to provide the desired level of accuracy or is unavailable. Use of a pseudolite-based reference system for navigation can be a means for positioning during these times. While there are advantages in using a pseudolite-based reference system, there are still implementation issues and deficiencies that must be addressed. In many cases, a pseudolite system with ground-based transmitters has difficulty determining the height of the receiver accurately. This is due to the poor vertical observability inherent in the geometry of the system. A common approach in naval applications for solving the …

Free Flight Store Simulation Using Beggar, Judson T. Babcock

Theses and Dissertations

The complete numerical solution of the airflow around a store in extended free flight is of particular importance to the United States Air Force. Beggar is the primary Computational Fluid Dynamics (CFD) program used by the USAF to obtain solutions for store separations. However, Beggar's ability to simulate a store in free flight is limited because the store must fall through a static background mesh, eventually reaching a point where the solution will fail. The length of any free flight simulation is consequently limited by the height of the background mesh. Code modifications are made to Beggar to remove this …

Quantitative Analysis Of A Turbulent Wind Tunnel With Obstructions For Use In Liquid Flame Spread Experiments, Beau M. Brantley

Theses and Dissertations

The research was done as part of an effort to develop alternative fire suppressant technologies for aircraft engine nacelles. The turbulent shear flow behind a surface mounted fence inside an open circuit wind tunnel was investigated experimentally. The tunnel test section was designed to be 2-D and exhibit flow qualities similar to those found in a typical engine nacelle. A 279 mm wide fuel pan was inserted approximately four fence heights downstream of the fence location. The fuel pan was filled using water to simulate fuel with a depth of 32 mm. Cold flow tests were done on different fence …

Space-Time Adaptive Processing For Side-Looking Arrays With Platform Maneuver, John T. Buckreis

Theses and Dissertations

This research effort develops a space-time adaptive processing (STAP) radar data model for the side-looking (SL) array with platform maneuver. A primary assumption of most STAP models is the absence of platform maneuver during the coherent processing interval (CPI). This research abandons the platform stationarity assumption, allowing platform pitch, roll, and yaw during the CPI. The model developed characterizes platform maneuver effects on the clutter spectrum, examines Matched Filter (MF) output Signal-to-Interference-plus-Noise-Ratio (SINR), and investigates maneuver impact on sample support homogeneity. The introduction of pitch marginally impacts MF SINR due to the lack of achieved azimuth resolution in this research, …

Characterization Of Functionally Graded Materials, Benjamin D. Chapman

Theses and Dissertations

The purpose of this study was to characterize the behavior of a functionally graded material through experimentation and analytical modeling. Functionally graded materials are a ceramic metal composite which transitions from metal on one face to ceramic on the opposite face. Creating reliable models required verifying the material properties. This was accomplished through the use of a static modulus of elasticity test as well as a dynamic ping test. The natural frequencies from the dynamic test were compared with finite element models to determine which material properties most accurately represented the functionally graded material. It was found that the material …

Spatially-Resolved Temperature Diagnostic For Supersonic Flow Using Cross-Beam Doppler-Limited Laser Saturation Spectroscopy, Grady T. Phillips

Theses and Dissertations

Optical techniques for measuring the temperature in three-dimensional supersonic reactive flows have typically depended on lineshape measurements using single-beam laser absorption spectroscopy. However, absorption over extended path lengths in flows with symmetric, turbulent eddies can lead to systematically high extracted temperatures due to Doppler shifts resulting from flow along the absorption path. To eliminate these problems, Cross-Beam Saturation Absorption Spectroscopy (CBSAS) and Cross-Beam Inter-Modulated Fluorescence (CBIMF) have been developed which utilize two crossed and nearly copropogating laser beams.to record the spectral signal of an I₂ ro-vibrational line in a small three-dimensional volume using a tunable CW dye laser. Temperature …

Discrete Event Simulation Model Of The Ground Maintenance Operations Cycle Of A Reusable Launch Vehicle, John T. Pope Iii

Theses and Dissertations

The Air Force uses a family of expendable launch vehicles to meet its spacelift needs. Unfortunately, this method is not responsive: months of preparation are typically required and launch costs are high. Consequently, the Air Force seeks a reusable military launch vehicle that can be launched inexpensively and quickly regenerated between flights. Air Force Research Laboratory personnel desire a tool to help evaluate candidate designs and perform tradeoff studies necessary to acquire a launch vehicle that will achieve Air Force goals. The objective of this research was first to develop a conceptual model of maintenance operations needed to regenerate a …

A Discrete Event Simulation Model For Evaluating Air Force Reusable Military Launch Vehicle Prelaunch Operations, Adam T. Stiegelmeier

Theses and Dissertations

As the control and exploitation of space becomes more important to the United States military, a responsive spacelift capability will become essential. Responsive spacelift could be defined as the ability to launch a vehicle within hours or days from the time a launch order is given, instead of the weeks or months it takes currently. As the Air Force contemplates moving toward a reusable military launch vehicle (RMLV) capability, it faces key design and ground processing decisions that will affect the vehicle regeneration timeline. This thesis develops a computer simulation model that mimics RMLV prelaunch operations-those activities that take place …

Optimizing Mean Mission Duration For Multiple-Payload Satellites, John A. Flory

Theses and Dissertations

This thesis addresses the problem of optimally selecting and specifying satellite payloads for inclusion on a satellite bus to be launched into a constellation. The objective is to select and specify payloads so that the total lifetime utility of the constellation is maximized. The satellite bus is limited by finite power, weight, volume, and cost constraints. This problem is modeled as a classical knapsack problem in one and multiple dimensions, and dynamic programming and binary integer programming formulations are provided to solve the problem. Due to the computational complexity of the problem, the solution techniques include exact methods as well …

Evaluating The Correlation Characteristics Of Arbitrary Am And Fm Radio Signals For The Purpose Of Navigation, Bryan S. Kim

Theses and Dissertations

The Global Positioning System (GPS) provides position estimates on the Earth at anytime, anywhere and in any weather. However, to provide robust positioning, GPS requires an unobstructed path to satellite signals. As such, GPS performance generally degrades or becomes non-existent in environments such as large urban areas. This research investigates and analyzes the correlation characteristics of arbitrary AM and FM radio signals for the purpose of navigation. Simulations are conducted with different combinations of correlation methods (`fixed' or `varying'), modulation types (AM or FM), and signal types (song or voice). Out of the eight different variations considered, only two provided …

Performance Analysis Of A Cooperative Search Algorithm For Multiple Unmanned Aerial Vehicles Under Limited Communication Conditions, Kevin M. Morris

Theses and Dissertations

This research investigates the impacts of realistic wireless communications upon a group of unmanned aerial vehicles (UAVs) utilizing a distributed search algorithm. The UAVs are used to survey an area for mobile targets and they require communication to cooperatively locate the targets. The mobile targets do not continually radiate energy, which exacerbates the search effort; a UAV could fly directly over a target and not detect it. A simulation of cooperative UAVs is implemented using the OPNET Modeler network simulation tool. The search performance of a group of UAVs is observed when communication range, data rate, and the number of …

Estimation And Mitigation Of Unmodeled Errors For A Pseudolite Based Reference System, Jeremiah A. Shockley

Theses and Dissertations

Current flight reference systems rely heavily on the Global Positioning System (GPS), causing susceptibility to GPS jamming. Additionally, an increasing number of tests involve jamming the GPS signal. A need exists to develop a system capable of GPS-level accuracy during these outages. One promising solution is a ground-based pseudolite system capable of delivering sub-centimeter level accuracy, yet operating at non-GPS frequencies. This thesis attempts to determine the unknown errors in the Locata system, one such pseudolite-based system, to achieve the accuracy required. The development of a measurement simulation tool along with a Kalman filter algorithm provides confirmation of filter performance …

Bio-Inspired, Odor-Based Navigation, Maynard John Porter Iii

Theses and Dissertations

The ability of moths to locate a member of the opposite sex, by tracking a wind-borne plume of odor molecules, is an amazing reality. Numerous scenarios exist where having this capability embedded into ground-based or aerial vehicles would be invaluable. The main crux of this thesis investigation is the development of a navigation algorithm which gives a UAV the ability to track a chemical plume to its source. Inspiration from the male moth's, in particular Manduca sexta, ability to successfully track a female's pheromone plume was used in the design of both 2-D and 3-D navigation algorithms. The algorithms were …

Detailed Design Of The Rigidizable Inflatable Get-Away-Special Experiment, Jeremy S. Goodwin

Theses and Dissertations

The Rigidizable Inflatable Get-Away-Special Experiment is a Space Shuttle experiment that will study the effects of the zero-gravity space environment on the deployment and modal analysis of three inflatable and rigidizable tubes using a sub-Tg rigidization technique. In 2004, RIGEX was transitioned from the Space Shuttle's Get-Away-Special (GAS) canister to its Canister for All Payload Ejections (CAPE), requiring several modifications to the design. The results of these modifications, along with further refinements made to previous efforts, combine to form the detailed design of the experiment. In addition to the design modifications, analyses were conducted to determine the containment capabilities of …

Development And Testing Of An Inflatable, Rigidizable Space Structure Experiment, Sarah K. Helms

Theses and Dissertations

Many recent space technology concepts require large space structures such as solar arrays and large aperture antennas; however, tight constraints on payload mass and volume often preclude their launch. Employing inflatable, rigidizable structures can reduce mass and volume while providing sufficient packing flexibility and structural stiffness. AFIT has developed RIGEX to flight-test this type of structure. RIGEX will test the deployment and structural characteristics of three thermoplastic composite Sub-Tg tubes. Once launched on the Space Shuttle in 2007, the spaceflight results will be compared to lab data to validate on-orbit reliability and ground test methods. This paper documents three main …

Evaluation Of Factors Contributing To Damping Of Coated And Uncoated Titanium Plates, Dustin W. Lee

Theses and Dissertations

High Cycle Fatigue (HCF) is the leading cause of component failure in gas turbine engines today, which poses great risk to aircraft, engines, and their crews. Mitigation of HCF effects has become a priority topic, and the damping benefits of hard coatings are being reevaluated for this purpose. Research was conducted to further understanding of damping measurements on these coatings. This study continues work to characterize the damping effects of a magnesium aluminate spinel (mag spinel) coating applied to a titanium plate via vibration testing. Two different plate sizes were evaluated in a clamped-free-free-free condition and a free-free-free-free condition, respectively. …