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Articles 1651 - 1674 of 1674
Full-Text Articles in Aerospace Engineering
Investigation Of Damage Mechanisms In A Cross-Ply Metal Matrix Composite Under Thermo-Mechanical Loading, Joel J. Schubbe
Investigation Of Damage Mechanisms In A Cross-Ply Metal Matrix Composite Under Thermo-Mechanical Loading, Joel J. Schubbe
Theses and Dissertations
Metal matrix composites (MMCs) are rapidly becoming strong candidates for high temperature and high stiffness structural applications such as the Advanced Tactical Fighter (ATF). This study systematically investigated the failure modes and associated damage in a cross-ply, [0/90]2s SCS6/Ti-15-3 metal matrix composite under in-phase and out-of-phase thermomechanic fatigue. Initiation and progression of fatigue damage were recorded and correlated to changes in Young's Modulus of the composite material. Experimental results show an internal stabilization of reaction zone size but degradation and separation from constituent materials under extended cyclic thermal loading. Critical to damage were transverse cracks initiating in the 90° …
Effect Of Riblets On Pressure Recovery In A Straight-Walled Diffuser, Michael K. Reagan
Effect Of Riblets On Pressure Recovery In A Straight-Walled Diffuser, Michael K. Reagan
Theses and Dissertations
The objective of this thesis was to investigate the effect of riblets on the pressure recovery in a straight-walled diffuser. Previous work has shown that riblets were effective in reducing the viscous drag over surfaces subjected to a turbulent boundary layer. More recently, riblets were shown to delay the flow separation within a subsonic, straight-walled diffuser by as much as 200%. The purpose of this investigation was to determine the effect on the pressure distribution within a diffuser that has had the flow separation point favorably altered by the application of riblets. Investigation results revealed that riblets not only delayed …
Material Properties Of Silicon Carbide Fibers With Continuously Applied Sol-Gel Alumina Coatings, Christian C. Daehnick
Material Properties Of Silicon Carbide Fibers With Continuously Applied Sol-Gel Alumina Coatings, Christian C. Daehnick
Theses and Dissertations
An investigation was conducted to determine the effect of non-alpha- alumina coatings applied under varying conditions on some of the properties of silicon carbide fibers. Limited characterization of the coating by optical, scanning electron, and transmitted electron microscopy as well as energy- dispersive x-ray analysis was performed. Tensile tests were used to determine changes in elastic modulus, ultimate strength, and strain to failure of the coated fibers relative to uncoated fibers. The coatings were found to lower the mean value of the measured properties as their thickness increased, but the measurements were not accurate enough to determine if this corresponded …
Adaptive Filtering And Smoothing For Tracking A Hypersonic Aircraft From A Space Platform, Kenneth A. Gotski
Adaptive Filtering And Smoothing For Tracking A Hypersonic Aircraft From A Space Platform, Kenneth A. Gotski
Theses and Dissertations
This study took a previously developed six state Kalman filter (designed for space-based tracking of a hypersonic transatmospheric vehicle), tuned it, and performed a Monte Carlo analysis. Three multiple model adaptive filters were then developed, with sub-filters designed for quiescent periods and periods with apparent acceleration. Next, a smoother was developed using the six state filter as the forward filter and a form of that same filter as the backward filter. The smoother and all of the above filters were compared for their ability to most accurately estimate the transatmospheric vehicle's state, with special emphasis on the acceleration states. This …
Analysis Of Periodic Orbits About The Martian Moons By Continuation Techniques, Frank Luria
Analysis Of Periodic Orbits About The Martian Moons By Continuation Techniques, Frank Luria
Theses and Dissertations
From a few known periodic orbits of Phobos and Deimos, continuation techniques were used to find entire families of stable orbits. These techniques involved varying a parameter, the Hamiltonian, of the system and analyzing how the orbital behavior changed with the parameter. Floquet multipliers, for stability analysis, were also computed. AUTO86, a continuation/bifurcation software package, was used in this study. Artificial energy dissipation had to be added to the conservative Hamiltonian system to enable use of AUTO.
A Comparison Of The Optimization And Analysis Of Doubly Curved Shells Using Msc/Nastran And Astros, John R. Dewsnap
A Comparison Of The Optimization And Analysis Of Doubly Curved Shells Using Msc/Nastran And Astros, John R. Dewsnap
Theses and Dissertations
This study identified techniques and software available for the optimization of doubly curved shells and applied them in the context of a large nozzle shape. An optimality criteria scheme that can reduce solution time was evaluated and compared to the Method of Feasible Directions. MSC/NASTRAN and ASTROS were used to perform finite element analysis and optimization, and the results were compared to the theory. The programs give virtually identical results, and if plates and shells are carefully modeled, then stresses, displacements and modes are accurate to within ten percent. A Mindlin-type axisymmetric finite element was implemented in ASTROS that preserved …
Skin Friction And Heat Transfer Predictions For Hypersonic Turbulent Flow Over An Ogive-Cylinder, Richard H. Byers
Skin Friction And Heat Transfer Predictions For Hypersonic Turbulent Flow Over An Ogive-Cylinder, Richard H. Byers
Theses and Dissertations
The WRDC/FIMG Parabolized Navier-Stokes (PNS) Code is used to numerically predict both laminar and turbulent hypersonic flows over an ogive- cylinder body at zero angle of attack. A parametric study is conducted to determine the effects of selected code input variables on heat transfer and skin friction predictions. Comparisons are made between the PNS predictions and experimental data from the WRDC/Mach 6 High Reynolds Number Test Facility. Various problems encountered while obtaining PNS starting and marching solutions and corrective steps taken are discussed. A mesh resolution study indicates the minimum radial grid density sufficient for obtaining reasonable heat transfer results. …
Damping Of Layered Beams With Mixed Boundary Conditions, Eugene T. Cottle
Damping Of Layered Beams With Mixed Boundary Conditions, Eugene T. Cottle
Theses and Dissertations
For many years, viscoelastic materials have been used in damping treatments to control vibration. In order to optimize a damping treatment for maximum damping, a design engineer must be able to predict frequencies of vibration of damped normal modes and loss factors as a function of the design parameters. Theoretical models of layered beams have been developed, but to date, exact solutions have assumed boundary conditions to be the same for all layers. In this thesis, equations of motion for a damped, layered beam are solved for the longitudinal displacement of both elastic layers, as well as the lateral displacement …
Numerical Analysis Of Critical Inclinations About The Planet Mars, Kenneth J. Hyatt
Numerical Analysis Of Critical Inclinations About The Planet Mars, Kenneth J. Hyatt
Theses and Dissertations
This study investigated critical inclinations about the planet Mars. Averaged equations of motion were numerically integrated over a time span of ten Earth years for various inclinations, eccentricities, and perigee heights. Each orbit (i.e. set of initial conditions) produced a standard deviation of the variations in eccentricity (SDE) and inclination (SDI). These were calculated using a polynomial approximation to the variations. Surface plots of SDI and SDE vs the initial conditions are then examined to ascertain the critical inclinations.
Dynamic Analysis Of A Combat Aircraft With Control Surface Failure, Marc Roy
Dynamic Analysis Of A Combat Aircraft With Control Surface Failure, Marc Roy
Theses and Dissertations
An investigation was performed to analyze the dynamic stability characteristic of an aircraft which has sustained damage to a primary control surface. The analysis was performed using the existing functional form of actual wind tunnel data taken on an F-16 model. Two control schemes are used for trimming an F-16 that has sustained damage to its rudder. The first control scheme represent the basic aircraft, while the second allowed the horizontal tail ailerons to move independently from the flaperons. The investigation was conducted for one flight condition representative of the aircraft at cruise speed. Region in α/β (angle of attack)/(sideslip …
Analysis Of Parking Orbits For A Sts External Tank In Low Earth Orbit, James E. Cross
Analysis Of Parking Orbits For A Sts External Tank In Low Earth Orbit, James E. Cross
Theses and Dissertations
A study was conducted of a single external tank in low earth orbit. Criteria for a parking orbit are then defined. Various orbits are then selected by varying the semi-major axis, eccentricity, and inclination. The resulting equations of motion for each of the above orbits (including atmospheric drag and a 2x0 gravity model) are numerically integrated over a time span of 90 earth days. An examination was made of the lowest initial altitudes which allowed the external tank to remain in the orbit window.
Minimum Orbits About The Planet Venus, Jeffrey J. Smith
Minimum Orbits About The Planet Venus, Jeffrey J. Smith
Theses and Dissertations
An investigation is conducted into low orbiting satellites around the planet Venus with drag limited lifetimes. It is possible to specify combinations of orbital elements which result in orbital lifetimes in excess of some desired value. These combinations can be assembled into Critical Curves and Critical surfaces. Critical Curves and Surfaces are defined as curves and surfaces in orbital element space above which initial element sets will result in orbits that meet or exceed lifetime requirements. A numerical method is implemented for finding these combinations, and three Critical Surfaces are examined. A decay threshold is selected for bounding satellite lifetime. …
On The Maximum Range Of Flying Wings, Peter J. Torvik
On The Maximum Range Of Flying Wings, Peter J. Torvik
AFIT Documents
The classical equations for determining the maximum range of aircraft with propeller and jet propulsion systems are reviewed, along with previous work conducted to determine the optimal division of aircraft volume between fuselage and wing components. That the jet powered flying wing configuration produces optimal range only for limited geometries is confirmed. The optimal range of aircraft employing high bypass jet engines is explored, and found to lead to a broader range of design parameters for which the flying wing design produces maximum range than is the case when a pure jet system is used.
Pronated Escape System For Fighter Aircraft, Allen D. Disselkoen Jr., Robert F. Gargiulo, James E. Haywood, Keith H. Heise, Darrell H. Holcombe, Stuart C. Kramer, Gregory R. Miller, Jeffrey S. Nicholson, Curtis H. Spenny
Pronated Escape System For Fighter Aircraft, Allen D. Disselkoen Jr., Robert F. Gargiulo, James E. Haywood, Keith H. Heise, Darrell H. Holcombe, Stuart C. Kramer, Gregory R. Miller, Jeffrey S. Nicholson, Curtis H. Spenny
AFIT Patents
An improved aircraft ejection seat system is described which embodies a forward leaning position for an occupant of the aircraft providing enhanced acceleration tolerance for an occupant during ejection from the cockpit, comprising a platform supporting at a rearward end thereof a seat having a seat back and seat pan sized and configured for accommodating the occupant, a forwardly disposed cowling integral with and faired to the platform for providing windblast protection to the occupant, a solid or cushioned upright wall member disposed centrally of the platform and extending between the seat and cowling and supporting an inclined chest plate …
System For Boundary Layer Control Through Pulsed Heating Of A Strip Heater, Milton E. Franke, Lawrence Kudelka
System For Boundary Layer Control Through Pulsed Heating Of A Strip Heater, Milton E. Franke, Lawrence Kudelka
AFIT Patents
A system is described for controlling the transition of laminar/turbulent flow at a surface which comprises a thin narrow strip heater disposed adjacent the surface and extending substantially transversely of the flow of the air stream thereacross, the heater being resiliently held in tension on or in closely spaced relationship to the surface, and a power source operatively connected to the heater for applying pulsed voltage of preselected amplitude and frequency to the heater.
Multiple Jet Blowing Around The Blunt Trailing Edge Of A Circulation Controlled Airfoil, John K. Harvell, Milton E. Franke
Multiple Jet Blowing Around The Blunt Trailing Edge Of A Circulation Controlled Airfoil, John K. Harvell, Milton E. Franke
AFIT Patents
A circulation controlled airfoil has a body structure with leading and trailing ends and upper and lower surfaces extending therebetween, and a cylindrical member disposed along the trailing end of the body structure between the upper and lower surfaces thereof so as to form a rounded, blunt trailing edge surface on the airfoil. A first blowing jet slot is defined between the outer surface of the cylindrical member and the trailing end of the body structure adjacent its upper surface. A second blowing jet slot is defined in a tubular wall of the cylindrical member. The latter member can be …
Solution To Eigenvalue Problems Of Antisymmetric Cross-Ply And Antisymmetric Angle-Ply Laminated Plates Using Affine Transformations, Zaffir A. Chaudry
Solution To Eigenvalue Problems Of Antisymmetric Cross-Ply And Antisymmetric Angle-Ply Laminated Plates Using Affine Transformations, Zaffir A. Chaudry
Theses and Dissertations
Using affine transformations and suitably recasting the buckling vibration differential equations, the eigenvalue problem of anti-symmetric cross-ply and antisymmetric angle-ply laminated rectangular plates has been reduced to a function of two strong material constants, the generalized rigidity ratio, whose range is in the closed interval from 0 to 1, and the ratio of principal lamina stiffness. With the reduction in number of constants an exhaustive parameter study of buckling and vibration solution trends, is possible. The buckling coefficients decrease with decreasing value of generalized rigidity ratio for both antisymmetric cross-ply and antisymmetric angle-ply laminates. For a given aspect ratio, and …
Planning For The On-Orbit Servicing Of Military Spacecraft, Michael E. Russell, Robert M. Tayloe
Planning For The On-Orbit Servicing Of Military Spacecraft, Michael E. Russell, Robert M. Tayloe
Theses and Dissertations
On-orbit spacecraft servicing for military programs is examined. The military community appears to be somewhat reticent to embrace or, in some cases, to even consider on-orbit servicing. The civilian community appears enthusiastic about the potential of on-orbit servicing and the majority of economic studies of civilian missions show servicing strategies to be an attractive alternative to most expendable spacecraft strategies. A model called SATSERV is presented. This model can be used to conduct economic comparisons from an overall standpoint between expendable and servicing strategies. The model is implemented in a microcomputer spreadsheet format for rapid implementation and application along with …
Axisymmetric Thrust Augmenting Ejector With Discrete Primary Air Slot Nozzles, Steven G. Reznick, Milton E. Franke
Axisymmetric Thrust Augmenting Ejector With Discrete Primary Air Slot Nozzles, Steven G. Reznick, Milton E. Franke
AFIT Patents
A circular thrust augmenting ejector has an annular wall which defines a central passageway and a convergent contoured inlet section, a constant area cylindrical mixing section and a divergent conical diffuser outlet section. The inlet, mixing and outlet sections merge one into the next in axisymmetric serial relationship. The ejector also has a plurality of discrete primary nozzles arranged about the periphery of the annular wall at the entrance to the inlet section thereof for injecting a primary flow of high velocity air into the inlet section and thereby entraining a secondary flow of ambient air into the central passageway …
Stochastic Estimation Applied To The Land Speed Of Sound Record Attempt By A Rocket Car, David A. Reinholz
Stochastic Estimation Applied To The Land Speed Of Sound Record Attempt By A Rocket Car, David A. Reinholz
Theses and Dissertations
Optimal linear smoothing theory is applied to the data from the Speed of Sound record attempt of a three-wheeled rocket car on 17 December 1979. A forward-backward estimation method is used which employs a seven state forward-running extended Kalman filter and a Meditch-form backward recursive 'fixed-interval' smoothing algorithm. Data for this analysis is supplied by a longitudinal accelerometer mounted on the vehicle and tracking radar measurements of range, azimuth, and elevation. States of interest include two components of vehicle position and velocity, accelerometer time-correlated error, and radar range and azimuth bias errors. Two iterations of the forward-backward smoothing algorithm provide …
Modal Control Of An Unstable Periodic Orbit, William Wiesel, William Shelton
Modal Control Of An Unstable Periodic Orbit, William Wiesel, William Shelton
Faculty Publications
We apply Floquet theory to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time periodic linear system, which is augmented by a time periodic control term. We show that this can be done such that a) the application of control produces only inertial accelerations, b) positive real Poincare exponents are shifted into the left half-plane, and c) the shift of the exponent is linear with control gain. We apply these developments to an unstable orbit near the Earth-Moon L3 point perturbed by the Sun. Finally, …
A Study Of A Wind Tunnel Measurement System For Unsteady Pressures Using Pneumatic Transmission Lines, Mohammed Javed Khan
A Study Of A Wind Tunnel Measurement System For Unsteady Pressures Using Pneumatic Transmission Lines, Mohammed Javed Khan
Theses and Dissertations
The application of pneumatic transmission lines theory to a tube-scanning valve system for unsteady pressure measurements in the AFIT 5-foot wind tunnel is investigated. Transfer gains of various tube-scanning valve configurations were experimentally measured and the validity of a theoretical model verified for a frequency range of 20 Hz to 140 Hz. The selected system having a 0.0625-in. ID flexible tube of 84 in. length connected to a scanning valve was installed in the wind tunnel. Unsteady pressures introduced over an 18 percent airfoil at zero angle of attack were measured with this system. Data were collected for 0, 40, …
Faa/Dod Liaison In Management Of The National Aviation System, Ronald S. Brooks, Jerry L. Beatty
Faa/Dod Liaison In Management Of The National Aviation System, Ronald S. Brooks, Jerry L. Beatty
Theses and Dissertations
This study describes and analyzes military and FAA liaison efforts which impact on the management of the National Aviation System. It begins with the historical development of the National Airspace System (NAS), The system is evolutionary in nature and most innovations have come from user demands and outside sources, Long term government responsibility to manage the system has been secondary to the operation and maintenance functions, There has been duplication of effort due to poor coordination on developing common goals, The military has been the leader in developing technology that led to improvement of the system.
Air Corp Engineering School, Wright Field - 1935 Catalog, Air Corps Engineering School, A. W. Robins
Air Corp Engineering School, Wright Field - 1935 Catalog, Air Corps Engineering School, A. W. Robins
AFIT Documents
This publication is issued to fill the need on the part of the Air Corps in general for a more detailed description of the curriculum of the Air Corps Engineering School. This description will serve as a guide to the accepted applicant in his preliminary preparation and a standard by which the individual Air Corps officer can arrive at an intelligent decision as to whether his own enthusiasm and preparation will be sufficient to warrant making application for the course. Entrance requirements are definitely stated herein. For those who do not contemplate intensive aeronautical engineering training, this publication may be …