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Articles 61 - 90 of 110
Full-Text Articles in Aerospace Engineering
Design Study Of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine For High Altitude Flight, Christopher E. Hamilton
Design Study Of Triggered Isomer Heat Exchanger-Combustion Hybrid Jet Engine For High Altitude Flight, Christopher E. Hamilton
Theses and Dissertations
This study investigated the possibility of utilizing a Triggered Isomer Heat Exchanger (TIHE) within a conventional jet engine in order to increase the endurance of a High Altitude Long Endurance (HALE) Intelligence, Surveillance, and Reconnaissance (ISR) aircraft. Optimizations of the conventional and TIHE engines along with selection of a switchover flight condition, where the aircraft switches from combustion to TIHE operations, were made utilizing engine design and mission analysis software. Radiation shield weights were determined utilizing point source gamma ray shielding methods. The jet engine best suited for the hybrid use, where both combustion and TIHE components located in a …
Alternative Pulse Detonation Engine Ignition System Investigation Through Detonation Splitting, August J. Rolling
Alternative Pulse Detonation Engine Ignition System Investigation Through Detonation Splitting, August J. Rolling
Theses and Dissertations
A Pulse Detonation Engine (PDE) combusts fuel air mixtures through a form of combustion: detonation. Recent PDE research has focused on designing working subsystems. This investigation continued this trend by examining ignition system alternatives. Existing designs required spark plugs in each separate thrust tube to ignite premixed reactants. A single thrust tube could require the spark plug to fire hundreds of times per second for long durations. The goal was to minimize hardware and increase reliability by limiting the number of ignition sources. This research used a continuously propagating detonation wave as both a thrust mechanism and an ignition system …
The Proceedings Of The Nasa Aerospace Technology Symposium 2002, Brent D. Bowen, Mary M. Fink, Michaela M. Schaaf, Uno Aviation Institute
The Proceedings Of The Nasa Aerospace Technology Symposium 2002, Brent D. Bowen, Mary M. Fink, Michaela M. Schaaf, Uno Aviation Institute
Faculty Books and Monographs
UNOAI Report 02-4
The Investigation Of Hypervelocity Gouging, David J. Laird
The Investigation Of Hypervelocity Gouging, David J. Laird
Theses and Dissertations
The slipper/rail interface of a hypervelocity rocket sled is subject to immense forces due to dynamic loads and impact of the slipper with the rail, and tremendous heating due to aerodynamic and frictional effects is produced at the interface. Under these severe loading conditions, the material in the rail will sometimes experience large non-linear deformations known as gouging. Hydrocodes are computational solvers designed to handle such non-linear, large deformation, high shock, hydrodynamic applications. The ability of the hydrocode CTH to handle gouge modeling is considered, as well as the manner in which temperature environments affect deformation and plastic strain. The …
Using The Gps To Collect Trajectory Data For Ejection Seat Design, Validation, And Testing, Brian R. Tredway
Using The Gps To Collect Trajectory Data For Ejection Seat Design, Validation, And Testing, Brian R. Tredway
Theses and Dissertations
The dynamic characteristics of an aircraft ejection seat are a crucial concern when evaluating aircraft ejection systems and their ability to separate aircrew members safely from disabled aircraft. Every ejection seat model undergoes real-time dynamic tests to determine potential injury to aircrew members during ejection. Ejection seat tests are conducted at high-speed test tracks. The test track facilities provide the required telemetry and high-speed photography to monitor and validate the aircraft escape system performance. Ejection seat test and evaluation requires very accurate position and velocity determination during each test run to determine the relative positions between the aircraft, ejection seat, …
Analytical Derivation Of A Coupled-Circuit Model Of A Claw-Pole Alternator With Concentrated Stator Windings, Hua Bai, Steven Pekarek, Jerry L. Tichenor, Walter Eversman, Duane J. Buening, Gregory R. Holbrook, Michael L. Hull, Ronald J. Krefta, Steven J. Shields
Analytical Derivation Of A Coupled-Circuit Model Of A Claw-Pole Alternator With Concentrated Stator Windings, Hua Bai, Steven Pekarek, Jerry L. Tichenor, Walter Eversman, Duane J. Buening, Gregory R. Holbrook, Michael L. Hull, Ronald J. Krefta, Steven J. Shields
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A lumped-parameter coupled-circuit model of a claw-pole alternator is derived. To derive the model, analytical techniques are used to define a three-dimensional (3-D) Fourier-series representation of the airgap flux density. Included in the series expansion are the harmonics introduced by rotor saliency, concentrated stator windings, and stator slots. From the airgap flux density waveform, relatively simple closed-form expressions for the stator and rotor self- and mutual-inductances are obtained. The coupled-circuit model is implemented in the simulation of an alternator/rectifier system using a commercial state-model-based circuit analysis program. Comparisons with experimental results demonstrate the accuracy of the model in predicting both …
Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren
Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren
Theses and Dissertations
In most recent years, both high-resolution imagery systems and images were only available to military and national security organizations. Distinctive changes within the commercial image industry allowed space-borne pioneers to provide high-resolution images. Space-borne Image Company's Ikonos satellite provides a 1-meter resolution for the past 3 years. Current development of .5-meter resolution will be offered in the near future. Access of these images is available in ground stations located worldwide in different regions. Studies have shown that these high quality images are eye-catching and may serve a purpose through its design; on contrary high cost and accessibility does not met …
Commercial Regional Space/Airborne Imaging, Ugur Akyazi, Ali Durmus, Birce Boga Bakirli, Arif Arin
Commercial Regional Space/Airborne Imaging, Ugur Akyazi, Ali Durmus, Birce Boga Bakirli, Arif Arin
Theses and Dissertations
In this work goal programming is used to solve a minimum cost multicommodity network flow problem with multiple goals. A single telecommunication network with multiple commodities (e.g., voice, video, data, etc.) flowing over it is analyzed. This network consists of: linear objective function, linear cost arcs, fixed capacities, specific origin-destination pairs for each commodity. A multicommodity network flow problem with goals can be successfully modeled using linear goal programming techniques. When properly modeled, network flow techniques may be employed to exploit the pure network structure of a multicommodity network flow problem with goals. Lagrangian relaxation captures the essence of the …
The Combined Effects Of Freestream Turbulence, Pressure Gradients, And Surface Roughness On Turbine Aerodynamics, Christine P. Ellering
The Combined Effects Of Freestream Turbulence, Pressure Gradients, And Surface Roughness On Turbine Aerodynamics, Christine P. Ellering
Theses and Dissertations
This work used scaled facsimiles of real turbine blade surfaces to characterize correlations between turbine blade roughness, freestream turbulence, pressure gradients and skin friction (Cf). Addition of roughness caused Cf to increase: up to 300% for the roughest surface. Addition of freestream turbulence resulted in 125% increase for the same surface. The combined effects showed increases up to 380%. Although decreasing roughness, freestream turbulence, and Reynolds number resulted in less dramatic results, it was concluded that the Cf increases due to combined effects were consistently higher than their corresponding sum of the parts. The combined effects of roughness and pressure …
Computational Aerodynamic Analysis Of The Flow Field About A Hypervelocity Test Sled, Andrew J. Lofthouse
Computational Aerodynamic Analysis Of The Flow Field About A Hypervelocity Test Sled, Andrew J. Lofthouse
Theses and Dissertations
The flow field about the nose section of a hypervelocity test sled is computed using computational fluid dynamics. The numerical model of the test sled corresponds to the Nike O/U narrow gage sled used in the upgrade program at the High Speed Test Track facility, Holloman Air Force Base, New Mexico. The high temperatures and pressures resulting from the aerodynamic heating and loading affect the sled structure and the performance of the vehicle. The sled transitions from an air environment to a helium environment at a speed of approximately 3,300 feet per second (Mach 3 in air, Mach 1.02 in …
Suppression Of Pilot-Induced Oscillation (Pio), Donald A. Johnson
Suppression Of Pilot-Induced Oscillation (Pio), Donald A. Johnson
Theses and Dissertations
Closed loop instability caused by excess phase lag induced by actuator rate limiting has been suspected in many pilot-induced oscillations (PIOs) and oscillatory departures from controlled flight. As part of the joint AFIT/TPS program, a longitudinal pilot command notch filter activated by a real-time oscillation verifier (ROVER) algorithm was developed to eliminate the PIO source for any developing, severe PIO. Closed loop computer simulations were conducted to prepare for the flight test. The HAVE ROVER flight test project was flown using the NF-16D Variable Stability In-flight Simulator Test Aircraft (VISTA). A programmable heads-up display (HUD) was used to generate a …
An Analytical Study Of T-38 Drag Reduction In Tight Formation Flight, Eugene H. Wagner Jr.
An Analytical Study Of T-38 Drag Reduction In Tight Formation Flight, Eugene H. Wagner Jr.
Theses and Dissertations
This thesis explores the benefits of flying in a tight formation, mimicking the natural behavior of migratory birds such as geese. The first phase of the research was to determine an optimal position for the wingman of a tight formation flight of T-38 Talon aircraft using the HASC95 vortex lattice code. A second wingman was then added to determine the benefit derived by increasing formation size. The second wingman was predicted to derive an even greater induced drag benefit than the first wingman for T-38s operating at Mach 0.54 at a 10,000-foot altitude. The predicted values were 17.5% savings for …
Investigation Of Cooperative Behavior In Autonomous Wide Search Munitions, Robert E. Dunkel Iii
Investigation Of Cooperative Behavior In Autonomous Wide Search Munitions, Robert E. Dunkel Iii
Theses and Dissertations
The purpose of this research is to investigate the effectiveness of wide-area search munitions in various scenarios using different cooperative behavior algorithms. The general scenario involves multiple autonomous munitions searching for an unknown number of targets of different priority in unknown locations. Three cooperative behavior algorithms are used in each scenario: no cooperation, cooperative attack only, and cooperative classification and attack. In the cooperative cases, the munitions allocate tasks on-line as a group, using linear programming techniques to determine the optimum allocation. Each munition provides inputs to the task allocation routine in the form of probabilities of successfully being able …
Periodic Methods For Controlling A Satellite In Formation, Erin Y. Carraher
Periodic Methods For Controlling A Satellite In Formation, Erin Y. Carraher
Theses and Dissertations
Precise position determination and control is necessary to accomplish proposed satellite formation flying missions of ground movement target indication and synthetic aperture radar. This thesis combines the estimation and control techniques of past AFIT theses with various time-varying and time-invariant LQG control methods. Linear time-invariant control is ideal for on-board satellite estimation and control applications, freeing-up the satellite's limited computational capacity. Using a dynamics frame transformation from the nodal frame to an orbital frame, a higher fidelity, time-periodic model produced nearly identical results for either time-varying or time-invariant control for many scenarios. Scenarios included initial perturbations in the radial, in-track, …
Orbital Maneuvering Using Electrodynamic Tethers, Hakan San
Orbital Maneuvering Using Electrodynamic Tethers, Hakan San
Theses and Dissertations
Considerably short electrodynamic tethers can be used as a low-thrust propulsion system with minimum or no mass expenditure. The propulsive force is generated by inducing a current flow through the tether which interacts with the magnetosphere of the planet (i.e. Earth, Jupiter and other planetary bodies with magnetosphere). The basics of electrodynamic tether systems have been studied and successful experiments such as boost and de-boost of spacecraft have been conducted in the past. This study presents a simple guidance scheme for the current in the tether in order to perform orbital maneuvers. The general perturbation equations are used to develop …
A Study Of Satellite Navigation, Dilution Of Precision, And Positioning Techniques For Use On And Around The Moon, John H. Macnicol
A Study Of Satellite Navigation, Dilution Of Precision, And Positioning Techniques For Use On And Around The Moon, John H. Macnicol
Theses and Dissertations
The National Aeronautics and Space Agency is examining several approaches to meet navigational requirements for spacecraft in lunar orbit, in transit to or from the moon, and for personnel on the lunar surface requiring an accurate, real-time, on-board navigation capability. This work addresses one possible solution to the navigation problem in the vicinity of the moon using a lunar satellite navigation system. Dilution of precision is the figure of merit used to determine if a candidate lunar satellite navigation system can meet accuracy specifications based on a given satellite constellation and the measurement types used. Ten satellite constellations, using two …
Performance Tradeoff Study Of A Gps-Aided Ins For A Rocket Trajectory, Muhittin Istanbulluoglu
Performance Tradeoff Study Of A Gps-Aided Ins For A Rocket Trajectory, Muhittin Istanbulluoglu
Theses and Dissertations
The Turkish Air Force (TuAF) has started a project to launch a satellite using only Turkish resources. Primary motivation behind this research is to assist TuAF's project by keeping up with these innovations in the navigational arena. The basic challenge in navigation system design is to decide which navigation system (or systems) and implementation techniques will be used, depending on accuracy requirements. The two primary navigation systems that will be integrated in this research are the Inertial Navigation System (INS), and the Global Positioning System (GPS). The Kalman filter algorithm is used to integrate INS and GPS. The rocket (Atlas …
Ins Aiding By Tracking An Unknown Ground Object, Mursy Polat
Ins Aiding By Tracking An Unknown Ground Object, Mursy Polat
Theses and Dissertations
The reduction of the navigation error in an inertial navigation system by optically tracking a ground object is investigated. Multiple observations of the ground object are used. The location of the ground object is assumed unknown. A careful analysis of the measurement situation at hand reveals that by optically tracking an unknown ground object using passive, bearings-only measurements, the aircraft's angle of attack and sideslip angle can be measured. Thus, two new independent measurement equations featuring the aircraft's angular navigation variables are obtained. Hence, by optically tracking over time an unknown ground object, inertial navigation system aiding is in fact …
Flight Control Failure Detection And Control Redistribution Using Multiple Model Adaptive Estimation With Filter Spawning, Michael L. Torres Jr.
Flight Control Failure Detection And Control Redistribution Using Multiple Model Adaptive Estimation With Filter Spawning, Michael L. Torres Jr.
Theses and Dissertations
In the current research, the MMAE with Filter Spawning and Control Redistribution (MMAE/FS/CR) are used together to identify failures and apply appropriate corrections. This effort explores the performance of the MMAE/FS/CR in different regions of the flight envelope using model and gain scheduling. The MMAE/FS/CR is able to detect complete and partial actuator/surface failures, as well as complete sensor failures. Once the actuator/surface failure is identified and the effectiveness is determined in the case of partial failures, proper control is applied in order to accomplish the desired pilot command. Improvements in the algorithm are required in order to enhance the …
Microdot - A Four-Bit Microcontroller Designed For Distributed Low-End Computing In Satellites, Anthony R. Woodcock
Microdot - A Four-Bit Microcontroller Designed For Distributed Low-End Computing In Satellites, Anthony R. Woodcock
Theses and Dissertations
Many satellites are an integrated collection of sensors and actuators that require dedicated real-time control. For single processor systems, additional sensors require an increase in computing power and speed to provide the multi-tasking capability needed to service each sensor. Faster processors cost more and consume more power, which taxes a satellite's power resources and may lead to shorter satellite lifetimes. An alternative design approach is a distributed network of small and low power microcontrollers designed for space that handle the computing requirements of each individual sensor and actuator. The design of microdot, a four-bit microcontroller for distributed low-end computing, is …
Evaluation And Mission-Specific Optimization Of Satellite Packet Telemetry Protocol For Use On Dod Flight Test Ranges, Beth A. Trapp
Evaluation And Mission-Specific Optimization Of Satellite Packet Telemetry Protocol For Use On Dod Flight Test Ranges, Beth A. Trapp
Theses and Dissertations
The DoD test range community has come to the realization that its telemetry abilities are obsolete. Efforts are therefore underway to improve telemetry systems at DoD test ranges. The overall objective of this project was to evaluate the practical use of the CCSDS packet telemetry protocol in DoD test ranges and determine the configuration that would maximize performance based on mission requirements. A secondary objective was to compare the CCSDS and ATM protocols in order to substantiate further exploration of using ATM in future DoD telemetry systems. Modeling and simulation of the CCSDS protocol showed a correlation between three CCSDS …
An Examination Of Latency And Degradation Issues In Unmanned Combat Aerial Vehicle Environments, Shane A. Dougherty
An Examination Of Latency And Degradation Issues In Unmanned Combat Aerial Vehicle Environments, Shane A. Dougherty
Theses and Dissertations
Since the multidimensional knapsack problems are NP-hard problems, the exact solutions of knapsack problems often need excessive computing time and storage space. Thus, heuristic approaches are more practical for multidimensional knapsack problems as problems get large. This thesis presents the results of an empirical study of the performance of heuristic solution procedures based on the coefficients correlation structures and constraint slackness settings. In this thesis, the three representative greedy heuristics, Toyoda, Senju and Toyoda, and Loulou and Michaelides methods, are studied. The purpose of this thesis is to explore which heuristic of the three representative greedy heuristics perform best under …
Experimental Vibration Analysis Of Inflatable Beams For An Afit Space Shuttle Experiment, Thomas G. Single
Experimental Vibration Analysis Of Inflatable Beams For An Afit Space Shuttle Experiment, Thomas G. Single
Theses and Dissertations
This study investigated the use of MEMS based devices to control the boundary layer separation from a circular cylinder in cross flow. Velocity profiles were measured experimentally in a low speed wind tunnel. Momentum thickness was measured as the primary way to determine a change in the flow field. The goal was to determine the angular location and frequency of operation that would provide an effect on the boundary layer of the cylinder. A 25% reduction of momentum loss in the cylinder wake was detected with an optimal angle of 69 degrees and an optimal frequency of operation equal to …
New Technologies For Rapid Space Experiments: Preliminary Design Review, Robert J. Twiggs
New Technologies For Rapid Space Experiments: Preliminary Design Review, Robert J. Twiggs
Robert "Bob" Twiggs STEM Education Collection
A PowerPoint Presentation created by Professor Bob Twiggs titled "New Technologies for Rapid Space Experiments: Preliminary Design Review" from February 25, 2002.
University Space Programs & Collaborative Space Research, Robert J. Twiggs
University Space Programs & Collaborative Space Research, Robert J. Twiggs
Robert "Bob" Twiggs STEM Education Collection
A PowerPoint Presentation created by Professor Bob Twiggs titled "University Space Programs & Collaborative Space Research" from February 8, 2002.
Neil Armstrong, Monish Ranjan Chatterjee
Neil Armstrong, Monish Ranjan Chatterjee
Electrical and Computer Engineering Faculty Publications
In addition to his outstanding and pioneering contributions to the National Aeronautics and Space Administration’s (NASA) crewed spaceflight program, Armstrong served with distinction as a professor of aerospace engineering, chairman and director of several corporations, and member of presidential commissions.
The Wright Stuff: A Redesign Of The 1905 Wright Flyer, Adam Richards, Ben Case, Eric Peterson, Nathan Holman, Wayne Goodrich, Amy Hintze, Carson Esplin, David Christensen, Jonathan Holfeltz, Nick Filimoehala, Nicholas Alley
The Wright Stuff: A Redesign Of The 1905 Wright Flyer, Adam Richards, Ben Case, Eric Peterson, Nathan Holman, Wayne Goodrich, Amy Hintze, Carson Esplin, David Christensen, Jonathan Holfeltz, Nick Filimoehala, Nicholas Alley
Mechanical and Aerospace Engineering Capstone Projects
No abstract provided.
Computing Small-Fleet Aircraft Availabilities Including Redundancy And Spares, Jeffery K. Cochran, Theodore P. Lewis
Computing Small-Fleet Aircraft Availabilities Including Redundancy And Spares, Jeffery K. Cochran, Theodore P. Lewis
United States Air Force: Publications
Logistics support is a key element of aircraft transportation systems. This paper is concerned with the impact of aircraft spares provisioning decisions on the availability of aircraft. Spares provisioning in this context is complicated by the fact that spares may be shared across aircraft and that aircraft may have redundant systems. In addition, decisions concerning aircraft spares support require a rapid response for safety reasons. Analytical models have proven to provide a quicker response time than corresponding simulation models. There is an existing analytical model that includes the effect of redundancy and spares, but the underlying assumption is that a …
Victim, Perpetrator, Family, And Incident Characteristics Of Infant And Child Homicide In The United States Air Force, Don R. Lucas, Kelley C. Wezner, Joel S. Milner, Thomas R. Mccanne, I. Nell Harris, Carla Monroe-Posey, John P. Nelson
Victim, Perpetrator, Family, And Incident Characteristics Of Infant And Child Homicide In The United States Air Force, Don R. Lucas, Kelley C. Wezner, Joel S. Milner, Thomas R. Mccanne, I. Nell Harris, Carla Monroe-Posey, John P. Nelson
United States Air Force: Publications
Objective: The present study describes factors related to fatal abuse in three age groups in the United States Air Force (USAF).
Method: Records from 32 substantiated cases of fatal child abuse in the USAF were independently reviewed for 60 predefined factors.
Results: Males were over-represented in young child victims (between 1 year and 4 years of age) and child victims (between 4 years and 15 years of age) but not in infant victims (between 24 hours and 1 year of age). African-American infant victims and perpetrators were over-represented. Younger victims were more likely to have been previously …
Atmospheric Turbulence Conditions Leading To Focused And Folded Sonic Boom Wave Fronts, Andrew A. Piacsek
Atmospheric Turbulence Conditions Leading To Focused And Folded Sonic Boom Wave Fronts, Andrew A. Piacsek
All Faculty Scholarship for the College of the Sciences
The propagation and subsequent distortion of sonic booms with rippled wave fronts are investigated theoretically using a nonlinear time-domain finite-difference scheme. This work seeks to validate the rippled wave front approach as a method for explaining the significant effects of turbulence on sonic booms [A. S. Pierce and D. J. Maglieri, J. Acoust. Soc. Am. 51, 702–721 (1971)]. A very simple description of turbulence is employed in which velocity perturbations within a shallow layer of the atmosphere form strings of vortices characterized by their size and speed. Passage of a steady-state plane shock front through such a vortex layer …