Aerospace Engineering Commons^™

Experimental Investigation Of The Effects Of Relative Physical Orientation Between Evaporator And Condenser For A Loop Heat Pipe, Brad R. Thompson

Theses and Dissertations

This research examined the effects on performance of varying angular orientation and height differences between evaporator and condenser for a loop heat pipe. Performance was defined as the difference in temperature between evaporator and condenser (DELTA T). The pipe was evaluated at varying input power (Qin) for: varying evaporator and condenser angles, different coolant temperatures, and varying relative height differences. All analysis included only steady state operation. The performance was influenced by condenser angles, with an optimal condenser angle for best performance being +45 degrees from horizontal. Additionally, the evaporator angles were found to influence performance only at low Qin …

A New Approach To Automatic Target Recognition Using Wavelet Transforms, Anitha Panapakkam, S. N. Balakrishnan, Daniel St. Clair

Computer Science Technical Reports

Automatic Target Recognition (ATR) systems have significant impact in defense applications. There is a continuing need to develop new and robust techniques to handle the increasingly complex ATR problem. The objectives of this thesis are two-fold. First a new technique to be used for ATR is developed and secondly an integrated ATR system to investigate and combine all subsystems is developed. In this thesis, we have developed a new technique for the feature extraction stage of ATR problem using wavelet transforms. Wavelet transforms have been one of the widely investigated areas of research in the past few years. The promising …

An Investigation And Improvement Of Electrorheological (Er) Fluid Technology, Adil F. Dalal

Masters Theses

The purpose of this research was to investigate and overcome the limitations of Electrorheological (ER) fluids and to introduce this advanced technology at WMU. Electrorheological (ER) Fluids are a special class of fluids, which exhibit a reversible, infinitely variable phase transition from a liquid to a solid/semi-plastic state, in the presence of an electric field.

ER fluids can provide a unique solution to the problems of vibration isolation of systems. The applications are currently limited due to the high voltage requirements, electric power related heating and limited research into wear/abrasive characteristics of ER fluids.

A specially designed and constructed "electro-viscosimeter" …

A Decision Support Model For Establishing A Plastics Recycling Program, Deven M. Dalcher

Theses and Dissertations

This research focuses on the development of a decision support model for the establishment of a plastics recycling program. The decision support model focuses on identifying the end-product uses and material specifications first. Once the end-product specifications have been identified, the recycling program can be designed. The model will provide solid waste managers an effective decision-making tool to evaluate the economic feasibility of establishing a plastics recycling program.

A Systems Engineering Approach To Environmental Risk Management: A Case Study Of Depleted Uranium At Test Area C-64, Eglin Air Force Base, Florida, Charles M. Carter, Kristina M. Fortmann, Stephen W. Hill, Robert M. Latin, Edward J. Masterson, Joseph A. Roh, Sujay R. Setlur

Theses and Dissertations

Environmental restoration is an area of concern in an environmentally conscious world. Much effort is required to clean up the environment and promote environmentally sound methods for managing current land use. In light of the public consciousness with the latter topic, the United States Air Force must also take an active role in addressing these environmental issues with respect to current and future USAF base land use. This thesis uses the systems engineering technique to assess human health risks and to evaluate risk management options with respect to depleted uranium contamination in the sampled region of Test Area (TA) C-64 …

Generic Satellite Monitoring Expert System, Loretta A. Kelemen

Theses and Dissertations

Air Force Satellite Operations is undergoing major changes. Operators no longer receive detailed satellite training, instead they are taught basic fundamentals of satellite operations and expected to control multiple multimillion dollar satellites. The need is clear. An efficient and economical automated system is necessary to assist the satellite operator in his daily tasks of maintaining these DOD priority resources. Satellite intelligent controllers been under R&D since the early 1980s to this need. These systems, however, have focused on the control of one constellation of satellites. In a military striving for efficiency and lower costs, developing a unique intelligent controller for …

Weighting Scheme For The Space Surveillance Network Automated Tasker, Beth L. Petrick

Theses and Dissertations

The purpose of this research is to find the best weighting scheme in the SPADOC 4C Sensor Tasking Prototype. This software, known as the Prototype Tasker, assigns a tasking to each sensor of the Space Surveillance Network. A tasking is a list of objects in which the sensor needs to gather positional data, called observations. One of the inputs to the Prototype Tasker is a user-definable weighting scheme. The goal is to find the weighting scheme that produces the most efficient taskings. This problem was solved using a Simulated Annealing algorithm. The values in the weighting scheme were the variables …

Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gordon C. Griffin Jr.

Theses and Dissertations

A moving bank multiple model adaptive estimator-controller (MMAE-MMAC), based on linear system, quadratic cost, and Gaussian noise (LQG) assumptions, is used to quell unwanted vibrations in a large flexible space structure. The structure, known as the SPace Integrated Controls Experiment, or SPICE, exists at Phillips Laboratory, Kirtland AFB, NM. The structure consists of a large platform and a smaller platform connected by a tripod of flexible legs. The purpose of the control system is to maintain a very precise line-of- sight vector through the center of the spacecraft. Kalman filtering, used to estimate the position and velocity of the bending …

Investigation Of Boundary Layer And Performance Effects Of Transpiration Cooling Through A Porous Plate In A Rocket Nozzle, David N. Keener

Theses and Dissertations

This study used a range of low blowing ratios with air through an area of porous material in a Mach 2.0 nozzle to quantity the change in boundary layer thickness as a function of blowing ratio. Also, exit and wall Mach number profiles at each blowing ratio were collected to characterize performance losses as a result of blowing. Performance in terms of specific impulse was also studied. As expected, the boundary layer thickness increased and nozzle performance in terms of exit Mach number decreased with increasing blowing ratio.

Investigation Into The Behavior Of Geometrically Nonlinear Composite Arches, John C. Bailey

Theses and Dissertations

This research modifies the existing finite element formulation of a potential energy based large deformation and moderate rotation theory. Hermitian shape functions replace the existing linear bending angle interpolations. Negligible differences between the two formulations indicate the underlying kinematics limit the accuracy, not the finite element interpolations. Using the new program, numerous nonlinear arch geometries are modeled to investigate the effects of arc length and thickness variations. Local and global snapping phenomena are captured as well as through the thickness shear driven nonlinearities.

The Design And Development Of A Low-Speed, Low-Force Wind Tunnel Data Acquisition System With An Application To Bicycle Front Fork Spacing, Alan W. Elledge

Theses and Dissertations

This thesis encompassed the design, development, and application of a low-speed, low-force data acquisition system for the AFIT 5-ft Wind Tunnel. The new data acquisition system was designed and developed to measure approximately 0.045 N (about 0.01 lb_f) at nearly 64.4 km/h (40 mph). Verification of the capability was obtained through testing of a cylindrical model. As part of a technology transition program with Wright Laboratory, this new system was used to investigate bicycle front fork blade spacing in order to determine the optimal spacing for minimum drag. As for the minimum drag of a bicycle with an …

The Effects Of An Integrated Space Support Node On Theater Air Combat, Paul J. Helt

Theses and Dissertations

The Air Force requires a methodology to assess alternative means for providing integrated space support data, collected from imagery space platforms, to enhance overall theater warfighting capability. This research examines imagery systems supporting the warning, surveillance, and weather missions, alternative concepts to integrate this imagery data, and models their influence on air-to-ground and limited ground-to-air combat in five potential theaters of operation. These theaters were Northeast Asia, Southeast Asia, Southeast Europe, the Caribbean, and Central America. Influence diagram decision analysis techniques were used to identify and quantify the key variables within the three space-based mission areas effecting air combat planning …

A Multi-Attribute-Utility-Theory Model That Minimizes Interview-Data Requirements: A Consolidation Of Space Launch Decisions, Raymond W. Staats

Theses and Dissertations

This research uses multi-attribute utility theory (MAUT) to define a mathematical representation of a decision maker's utility associated with a satellite system. While developing the survey instrument, we focused on making it simpler to administer, primarily by eliminating the use of lottery questions. These simplifications enabled us to shorten our interview with the decision maker to under two hours for a rather complex model.

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Subjected To Tension-Tension Cycling With Hold Time, Scott A. Grant

Theses and Dissertations

This study was carried out to investigate the elevated temperature behavior of the SiC-MAS5 cross- ply [0-90]_4S ceramic matrix composite manufactured by Corning Inc. to fatigue with loading waveforms that combine the characteristics of stress rupture and high cycle fatigue. The test results were compiled in the form of S-N (cycles to failure), S-T (exposure time versus cycles to failure), S-S (energy exposure versus cycles to failure), normalized modulus degradation, strain progression, and hysteresis loop progression. From the mechanical behavior demonstrated by these curves, relationships between the effect of the environment and loading waveform were developed. In addition, a …

Compressible Turbulence Measurements In A Supersonic Boundary Layer Including Favorable Pressure Gradient Effects, Raymond S. Miller

Theses and Dissertations

The effect of a favorable pressure gradient on the turbulent flow structure in a Mach 2.9 boundary layer (R_e/m approx. 1.5 x 10⁷) is investigated experimentally. Conventional flow and hot film measurements of turbulent fluctuation properties have been made upstream of and along an expansion ramp. Upstream measurements were taken in a zero pressure gradient boundary layer 44 cm from the nozzle throat in a 6.35 cm square test section. Measurements are obtained in the boundary layer, above the expansion ramp, 71.5 cm from the nozzle throat. Mean flow and turbulent flow characteristics are measured in …

An Experimental Study Of Planar Heterogeneous Supersonic Confined Jets, Frederick J. Tanis Jr.

Theses and Dissertations

The effects of varying the exit pressure of a supersonic helium jet exhausting coaxially with two parallel supersonic air streams into a constant area duct were investigated. The method used to evaluate the mass entrainment rate was to measure helium molar concentration profiles and mass flux across the duct using a binary gas probe then calculate the mass entrainment into the helium jet. In order to conduct this study a novel binary gas probe was developed which allowed helium concentration and mass flux data to be obtained during continuous traverses across the supersonic flowfield. High exit pressure ratio (EPR) led …

The Collapse Of Composite Cylindrical Panels With Various Thickness Using Finite Element Analysis, Christopher P. Chaplin

Theses and Dissertations

This study compared numerical collapse results of graphite-epoxy cylindrical panels with free vertical edges undergoing axial compression for three different shell theories. Symmetric quasi-isotropic laminates were investigated using solid panels and panels with five different centralized cutouts with three thicknesses. The theories compared in the study were the Simplified Large displacement moderate Rotation (SLR) theory, the Donnell Cylindrical Shell (Modified Donnell) theory, and the Classical Donnell theory. The purpose of the study was to determine when large rotations and through-the-thickness shear become important in the numerical collapse analysis of cylindrical composite shells. By observing cases where the numerical collapse results …

A State-Space Model Of A Large, Lightly Damped Space Structure Using The Eigensystem Realization Algorithm, Robert D. Woods

Theses and Dissertations

Large, lightweight space structures of the future will require state-of-the-art vibration suppression systems. To design such a system, it is necessary to have a mathematical model that adequately describes the motion of the system. Coulomb damping compensation was utilized to remove a known nonlinearity from the frequency response functions obtained from the Passive and Active Control of Space Structures (PACOSS) Dynamic Test Article (DTA). Via the Eigensystem Realization algorithm (ERA), the frequency response functions were then used to generate a mathematical representation of the structure's dynamics. Two models were obtained. The first model, without friction compensation, acted as a baseline. …

Stall Precursor Study Of High Frequency Data For Three High Speed, Swept Compressor Rotors, James F. Anderton

Theses and Dissertations

The frequency spectra of three single stage, high speed compressor rotors were derived and analyzed from experimental data. The compressor rotors included straight, backward-swept, and forward-swept blade designs. Data was acquired from four pressure transducers located on the compressor casing and arranged axially between locations 40% of blade chord upstream of the rotor face to just over the leading edge of the blades. Each rotor was throttled to stall at two constant speeds between 90% and 100% of design speed. Data digitization at 20 kHz revealed multiples of the rotor frequency up to and beyond a dominant blade passing frequency. …

Telepresent Spacecraft Docking With Object-Based Bilateral Control (Obbc), Paul Woznick

Theses and Dissertations

The concept of object-based control is extended to the field of teleoperation, specifically to accomplish the task of spacecraft docking via a bilateral manual controller. An object-based controller with bilateral feedback controls the motion of the grasped object, not the trajectory of the manipulator. For this reason it can be designed with feedback that is intricately linked with the task kinematics. The benefits derived from anthropomorphicity and force feedback are possible without kinematically-geometrically similar master-slave systems, complex calibration and joint mapping schemes, or expensive, high degree-of-freedom force reflection. Object-based control is ideal for low-level telerobotic interfaces. A hand controller and …

Analysis Of Hypersonic Boundary Layer Second Mode Instability Over A 7° Cone, Richard A. Dennery

Theses and Dissertations

This paper presents the results of the analysis of Mach 8.0 flow over a seven degree half-angle cone. The purpose of this analysis was to develop techniques to examine boundary layer transition at hypersonic velocities. The specific objectives were to look for second mode instability waves characteristic of the transition process and to quantify the percentage of turbulent flow. Two sets of data were used in this analysis. The first set of data was taken at several axial positions at a freestream Reynolds number 4.265 million per meter. This data was used to develop the analysis techniques. The second set …

Characterization Of Fatigue Behavior Of 2-D Woven Fabric Reinforced Ceramic Matrix Composite At Elevated Temperature, Daniel J. Groner

Theses and Dissertations

This study investigated the fatigue behavior and associated damage mechanisms in notched and unnotched enhanced Sic-SiC ceramic matrix composite specimens at 1100°C. Stiffness degradation, strain variation, and hysteresis were evaluated to characterize material behavior. Microscopic examination was performed to characterize damage mechanisms. During high cycle-low stress fatigue tests, far less fiber-matrix interface debond was evident than in low cycle-high stress fatigue tests. Notched specimens exhibited minimal stress concentration during monotonic tensile testing and minimal notch sensitivity during fatigue testing. Damage mechanisms were also similar to unnotched.

Viscoplastic Characterization And Fatigue Modeling Of Titanium Based Metal Matrix Composites, Mark A. Foringer

Theses and Dissertations

Viscoplastic characterization and fatigue modeling of titanium-based metal matrix composites was accomplished by combining a unified viscoplastic theory, a nonlinear micromechanics model, and a linear damage accumulation model. First. Ti 15-3 was characterized using the Bodner-Partom viscoplastic theory. A micromechanics model was then employed in a linear damage accumulation fatigue model to predict the fatigue behavior of titanium based composites. The viscoplastic behavior predictions of the micromechanics model were used to eliminate separately defined time dependent terms in the fatigue model. Also, a new linear damage accumulation model was developed from the fatigue behavior of the composite constituents. Finally, it …

A Comparison Of The Neal-Smith And ΩSpΤΘ2, ΣSp, ΤΘ Flying Qualities Criteria, Brian A. Kish

Theses and Dissertations

Aircraft pitch response is a vital element of piloted vehicle flying qualities. There has been controversy over both the form and the substance of the requirements for short-term pitch response. Currently, MIL-STD- 1797A offers six different methods for evaluating short-term pitch response. These six methods often give conflicting results. Two methods are analyzed in this thesis - the Neal-Smith criteria and the ω_spΤ_θ2, ς_sp, τ_θ criteria. Domains from both criteria are mapped into each other identifying regions of conflict and regions of agreement. Parametric studies are performed and evaluated for trends. Further, a …

Improved Numerical Solution Of Mixed H2/H∞ Optimization With Applications, Linda D. Smith

Theses and Dissertations

This study improved the numerical optimization technique used to compute mixed H₂/H_∞ controllers. The run time to generate the full curve of an H₂/H_∞ design was reduced by a factor of almost 200 for a specific example. This was accomplished by improving gradient calculations, upgrading the H_∞ norm calculation to capture multiple peaks in the singular value plot and using routines that minimized processing time. The optimization routine used was the MATLAB CONSTR' Sequential Quadratic Programming (SQP) routine. This SQP routine was compared to a FORTRAN SQP numerical optimizer, IMSL-DNCONG. The method was …

The Design And Analysis Of Integrated Navigation Systems Using Real Ins And Gps Data, Curtis D. Evans

Theses and Dissertations

An extended Kalman filter (EKF) is used to combine the information obtained from a Global Positioning System (GPS) receiver and an Inertial Navigation System (INS) to provide a navigation solution. This research compares the results of an actual tightly-coupled GPS-INS integrated system with those obtained in computer simulation. Differences between the simulation and actual hardware results, such as navigation solutions and tuning values, are shown in the research. An analysis of various GPS models was studied to determine the best representation for a system truth model. Measurement updates and their effects upon position accuracies was considered and preliminary research was …

Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz

Theses and Dissertations

This experiment analyzed the effects of blowing ratio on heat transfer to the throat region of a porous-walled nozzle, using the AFIT low speed shock tube. Heat flux data were taken from both sides of a two-dimensional Mach 2.0 Re-m=5.2x10⁷ nozzle using thin film resistance thermometers. One side was transpiration-cooled by secondary air injection through a sintered wall, while the other side served as a control. Control results were validated using empirical relations, and cooled side results showed up to a 14% reduction in heat transfer coefficient at blowing ratios of only 0.51%. The linear nature of cooling effectiveness …

A New Drag Measurement System For Wind Tunnel Testing Of The Racing Bicycle And Rider To Determine A Low Drag Configuration, Brian A. Parker

Theses and Dissertations

This study investigated the application of splitter plate effects to reduce the aerodynamic drag of the racing bicycle and rider system. A sensitive, low-force, beam-type, single-component balance was developed to provide drag measurements accurate to within 0.053 N (0.012 lb_f). The performance of the new system was verified by comparing the measured drag on a three-dimensioaal, right-circular cylinder model, 0.127 m (5.0 in) in diameter and 0.610 m (24 in) long, with the results from a commercial balance and a other similar data. The bicycle and rider model consisted of a full-scale mannequin comprising only the hips, legs …

Finite Element Methods For Nonlinear Static Analysis Of Sandwich Plates, Damin J. Siler

Theses and Dissertations

A finite element method, developed for static analysis of composite plates, was enhanced to be used with sandwich plates. The theory considers geometric nonlinearity and transverse shear. Furthermore, a new postprocessor was written to check for initial failure using the maximum stress criteria. It also includes a procedure for evaluating transverse normal stresses by enforcing equilibrium. The code modifications for sandwiches were verified by comparing finite element solutions to closed-form sandwich theories. Both methods showed good correlation. In addition, comparisons between one type of composite plate and a similar sandwich plate found that the sandwich had better specific stiffness for …

An Investigation Of The Afit 2-Inch Shock Tube As A Flow Source For Supersonic Testing, Kevin M. Vlcek

Theses and Dissertations

An investigation of the AFIT high pressure shock tube was conducted to determine how closely it followed ideal shock tube theory and to determine the available test times for an attached Mach 3 nozzle. The driver section was five feet (1.52 m) long and the driven section was 25 feet (7.62 m) long. The driver gas used for this study was helium while the driven gas was atmospheric air. The pressure rise measured behind the incident shock wave was, on average, 30% lower than predicted by the ideal shock tube relations. Behind the reflected shock, the pressure rise was 65% …