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- Space vehicles--Propulsion systems (5)
- Artificial satellites--Control systems (4)
- Space vehicles--Control systems (3)
- Aerodynamics (2)
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- Artificial satellites--Optical observations (2)
- Astronautics (2)
- Flexible structures (2)
- Flight control (2)
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- Fretting corrosion (2)
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- Internal combustion engines--Ignition (2)
- Magnetohydrodynamics (2)
- Nozzles--Fluid dynamics (2)
- Reconnaissance aircraft (2)
- Aeronautical instruments--Display systems (1)
- Aeronautics--Safety measures (1)
- Air flow (1)
- Air-supported structures (1)
- Aircraft exhaust emissions (1)
- Airplanes--Piloting--Computer simulation (1)
- Airplanes--Ramjet engines (1)
- Airplanes--Wings--Design and construction (1)
- Artificial satellites--Tracking (1)
- Balancing of machinery (1)
- Ballistic missiles--Atmospheric entry (1)
- Cavities (Airplanes) (1)
- Chemiluminescence--Measurement (1)
- Coanda effect (1)
Articles 1 - 30 of 44
Full-Text Articles in Engineering
Wind Tunnel Investigation Of The Static Stability And Control Effectiveness Of A Rotary Tail In A Portable Uav, Jose R. Rivera Parga
Wind Tunnel Investigation Of The Static Stability And Control Effectiveness Of A Rotary Tail In A Portable Uav, Jose R. Rivera Parga
Theses and Dissertations
The Air Force Research Lab, Munitions Directorate, Flight Vehicles Integration Branch (AFRL/MNAV) developed a man-portable, carbon-fiber matrix UAV with a flexible rectangular wing of 24" span and 6" chord, 18.2" length. There is a need for the development of smaller and lighter UAV's to perform certain missions. The objective of this experimental study was to determine the behavior and the aerodynamic characteristics of rotary tails. The bird-inspired rotary tail mechanism studied enabled control of two degrees of freedom and was configured to provide elevator deflection and rotation. Its effects on the static stability and control effectiveness were measured using the …
Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo
Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo
Theses and Dissertations
Satellite formations or distributed satellite systems provide advantages not feasible with single satellites. Efficient operation of this platform requires the use of optimal control of the entire satellite formation. While the optimal control theory is well established, only a very simple dynamical system affords an analytical solution. Any practical optimal control problem solves the resulting two-point boundary value (TPBV) problem numerically. The relative satellite dynamics using Hill's coordinate system and approximations made by Clohessy and Wiltshire, combined with body-fixed thruster control, result in a linearized dynamic system. This dissertation provides the analysis for the minimum time satellite formation control by …
Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman
Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman
Theses and Dissertations
There is a growing interest in understanding how uncertainties in flight conditions and structural parameters affect the character of a limit cycle oscillation (LCO) response, leading to failure of an aeroelastic system. Uncertainty quantification of a stochastic system (parametric uncertainty) with stochastic inputs (initial condition uncertainty) has traditionally been analyzed with Monte Carlo simulations (MCS). Probability density functions (PDF) of the LCO response are obtained from the MCS to estimate the probability of failure. A candidate approach to efficiently estimate the PDF of an LCO response is the stochastic projection method. The objective of this research is to extend the …
Aerodynamic Analysis Of Lattice Grid Fins In Transonic Flow, Karl S. Orthner
Aerodynamic Analysis Of Lattice Grid Fins In Transonic Flow, Karl S. Orthner
Theses and Dissertations
Lattice grid fins have been studied for missile tail control for several years. A lattice grid fin can be described as an unconventional missile control surface comprised of an outer frame supported by an inner lattice grid of lifting surfaces. This unconventional fin design offers favorable lift characteristics at high angle of attack as well as almost zero hinge moments allowing the use of small and light actuators. In addition, they promise good storability for potential tube-launched and internal carriage dispenser-launched applications. The drawback for the lattice grid fins is the high drag and potentially poor radar cross section performance …
Detached Eddy Simulation Analysis Of Pak-B Low Pressure Turbine Blade, Kyle Malone
Detached Eddy Simulation Analysis Of Pak-B Low Pressure Turbine Blade, Kyle Malone
Theses and Dissertations
Two cases were computationally investigated using the detached eddy simulation (DES) turbulence model: an unmodified Pak-B blade and a Pak-B blade with a dimple located at 65% of axial chord. Both cases were created so that they simulated an infinite span with an infinite number of dimples. The cases were run for an inlet Reynolds number of 25,000. The computed results were used to resolve the location of separation and reattachment, visualize the streamlines for the dimpled case, build velocity magnitude contour and vector plots, and map the thickness of the boundary layer. The results were then compared to previous …
Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Brian H. Harrington
Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Brian H. Harrington
Theses and Dissertations
The effect of magnetogasdynamic (MGD) interactions on flow acceleration and thrust in a scramjet accelerator/nozzle are examined numerically at a free-stream flight condition of Mach 8. The parameters of conductivity pattern and load factor are varied in both inviscid and viscous flow regimes with the intent of increasing axial force exerted on the flow through a scramjet accelerator. The numerical code solves the Navier-Stokes equations with additional source terms for the MGD forces and energy interactions. An accelerating Lorentz force is applied to the flow resulting from a constant magnetic field and an electric field produced by two continuous side …
Fretting Fatigue Behavior Of Shot-Peened Titanium Alloy Tl-6al-4v Under Seawater Conditions, William Y. Allen
Fretting Fatigue Behavior Of Shot-Peened Titanium Alloy Tl-6al-4v Under Seawater Conditions, William Y. Allen
Theses and Dissertations
The fretting fatigue behavior of the shot-peened titanium alloy, Ti-6Al-4V, was investigated under a corrosive environment of synthetic seawater. Fretting fatigue tests were performed over a wide stress range to determine the effect of seawater at high and low cycle fatigue regimes. The results from this study showed: (1) seawater significantly reduces the fretting fatigue life of shot-peened Ti-6Al-4V at both high and low cycle fatigue relative to its counterpart in ambient laboratory conditions, (2) shot peening increases the fretting fatigue life of Ti-6Al-4V when tested under dry and seawater conditions relative to its counterpart of unpeened Ti-6Al-4V, (3) surface …
Cold Flow Testing Of A Modified Subscale Model Exhaust System For A Space Based Laser, David B. Jarrett
Cold Flow Testing Of A Modified Subscale Model Exhaust System For A Space Based Laser, David B. Jarrett
Theses and Dissertations
The aim of this research was a continued study of gas-dynamic phenomena that occurred in a set of stacked nozzles as reported by Captains Ian Bautista in 2003 and Scott Bergren in 2002. The arrangement of the stacked nozzles was a modified version of a 1/5th scale-model of one quadrant of the conceptual Space Based Laser Integrated Flight Experiment (SBL IFX) gas dynamic laser. Rather than cylindrical rings of nozzles, the stacked nozzles were flat and able to be rotated about a vector normal to the nozzle exits. This set of stacked flat nozzles was installed on a blow-down/vacuum wind …
Shock Tube Investigation Of Pressure And Ion Sensors Used In Pulse Detonation Engine Research, Robert J. Mcmillan
Shock Tube Investigation Of Pressure And Ion Sensors Used In Pulse Detonation Engine Research, Robert J. Mcmillan
Theses and Dissertations
Shock tubes utilize a difference in pressures between gases separated by a diaphragm to create a shock wave when the diaphragm ruptures. By using sensors of known spacing, the speed of the wave can be determined. The AFIT 2-inch shock tube was reassembled and tested to ensure proper and safe operation. A high-speed data acquisition system was configured to take data at 2 MS/s. This research showed that the Mach number of the shock waves produced in this shock tube fall within 7% of theoretical values at speeds under Mach 3 and within 9% at higher speeds. The peak velocity …
An Assessment Of Modern Methods For Rotor Track And Balance, Michael J. Renzi
An Assessment Of Modern Methods For Rotor Track And Balance, Michael J. Renzi
Theses and Dissertations
One routine maintenance item facing the helicopter industry today is the issue of rotor track and balance (RT&B). While the task of reducing vibrations is often overlooked as simply an unimportant maintenance concern, what should not be overlooked is the extensive amount of time and money committed by maintenance to smoothing an aircraft. If there were a way to make the process of rotor track and balance more efficient it would be a huge boost to the helicopter industry in both time and money. The first steps towards research into new and improved methods is to evaluate what is currently …
Isomer Heat Exchanger Combustor Replacement For A Supersonic Ramjet Powered Vehicle, Jonathan C. Cox
Isomer Heat Exchanger Combustor Replacement For A Supersonic Ramjet Powered Vehicle, Jonathan C. Cox
Theses and Dissertations
This study investigated the possibility of utilizing a Triggered Isomer Heat Exchanger (TIHE) within a ramjet engine to power a supersonic Conventional Air Launched Cruise Missile (CALCM). A computational ramjet engine was created using engine analysis software. This model was then run through a simulated cruise missile mission using AEDsys, a mission analysis and engine performance software suite. The replacement of the combustor with a TIHE led to an impressive range increase for the supersonic cruise missile.
Aeroelastic Analysis Of A Joined-Wing Sensorcraft, Jennifer J. Sitz
Aeroelastic Analysis Of A Joined-Wing Sensorcraft, Jennifer J. Sitz
Theses and Dissertations
This study performed an aeroelastic analysis of a joined-wing SensorCraft. The analysis was completed using an aluminum structural model that was splined to an aerodynamic panel model. The force and pressure distributions were examined for the four aerodynamic panels: aft wing, fore wing, joint, and outboard tip. Both distributions provide the expected results (elliptical distribution), with the exception of the fore wing. The fore wing appears to be affected by interference with the joint. The use of control surfaces for lift and roll was analyzed. Control surfaces were effective throughout most of the flight profile, but may not be usable …
A Study Of A Skirtless Hovercraft Design, Edward A. Kelleher
A Study Of A Skirtless Hovercraft Design, Edward A. Kelleher
Theses and Dissertations
Initial study into three possible skirtless hovercraft designs. The designs utilize Coanda nozzles and a Coanda wing surface to generate lift and create a pressure cushion below the craft. The pressure cushion is to be maintained by an air curtain created by flow spill from the Coanda wing surface. Three proposed skirtless hovercraft designs were analyzed via computational fluid dynamics to ascertain their lift generation capabilities. The three designs were adaptations from William Walter's hybricraft primer and his patent for a fan driven lift generation device. Each design featured Coanda nozzles, or nozzles that utilize the Coanda effect, to redirect …
Coplanar Air Launch With Gravity-Turn Launch Trajectories, David W. Callaway
Coplanar Air Launch With Gravity-Turn Launch Trajectories, David W. Callaway
Theses and Dissertations
The purpose of this study was to determine the feasibility of launching a vehicle based on the Boeing AirLaunch System in a coplanar, direct to rendezvous trajectory with gravity-turn. The focus of the research was to model the launch trajectory and determine the ability to reach different coplanar orbits. The launch trajectory was modeled using two-dimensional equations of motion and a boundary value problem was posed and solved for the gravity-turn trajectory. Trajectories were then created in an attempt to reach different altitudes through coasting and transfer orbits. Finally a specific orbital altitude was chosen and the trajectories were analyzed …
Analytical Results For A Single-Unit System Subject To Markovian Wear And Shocks, Daniel E. Finkelstein
Analytical Results For A Single-Unit System Subject To Markovian Wear And Shocks, Daniel E. Finkelstein
Theses and Dissertations
This thesis develops and analyzers a mathematical model for the reliability measures of a single-unit system subject to continuous wear due to its operating environment and randomly occurring shocks that inflict a random amount of damage to the unit. Assuming a Markovian operating environment and shock arrival mechanism, Laplace-Stieltjes transform expressions are obtained for the failure time distribution and all of its moments. Moreover, an analytical expression is derived for the long-run availability of the single-unit system when it is subject to an inspect-and-replace maintenance policy. The analytical results are illustrated, and their results compared with those of Monte Carlo-simulated …
An Analysis Of The Potential For Using Over-The-Horizon Radar Systems For Space Surveillance, Matthew J. Colbert
An Analysis Of The Potential For Using Over-The-Horizon Radar Systems For Space Surveillance, Matthew J. Colbert
Theses and Dissertations
The Australian Defence Force is investigating the development of a space surveillance system. While several dedicated facilities for space surveillance are in operation around the world, Australia s Over-The-Horizon Radar (OTHR) network has some potential for this role. The OTHR operates in the HF band and is constrained by the propagation effects of the ionosphere. A spherically stratified ionospheric model and a model for a nominal OTHR antenna are developed that allow calculation of path propagation, power distribution, and clutter returns. A software-based radar receiver processing system is modeled to determine detection probabilities and the minimum detectable radar cross-section of …
Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca
Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca
Theses and Dissertations
The Air Force Research Lab, Munitions Directorate, Eglin Air Force Base, Florida has designed a man-portable carbon-fiber Micro-Air-Vehicle (MA V) used for on-the-spot surveillance by Special Operations Forces (SOF) for enemy reconnaissance as well as post-strike Battle Damage Assessment (BDA).The main goals of this experiment are: 1) characterize the flow quality of the new AFIT 3' x 3' wind tunnel and 2) determine the aerodynamic performance characteristics of the 24" span, 6" chord flexible and rigid wing MA V s. The turbulent intensity of the wind tunnel was approximately 2%. Both MA Vs had an average lift slope within 3.5% …
Detonation Branching In A Pde With Liquid Hydrocarbon Fuel, Kristin L. Panzenhagen
Detonation Branching In A Pde With Liquid Hydrocarbon Fuel, Kristin L. Panzenhagen
Theses and Dissertations
A pulse detonation engine (PDE) capitalizes on the large mass flux and pressure rise associated with detonations to create thrust, which is proportional to PDE cycle frequency. This research showed that using a branched detonation as an ignition source, as opposed to standard spark ignition, deposits more energy into the thrust tube head. The increase in energy decreases ignition delay and detonation to deflagration transition (DDT) time. This allows a theoretical 85% cycle frequency increase that is accompanied by an 85% increase in thrust. The increase in energy also reduces the need for a DDT enhancement device, thereby increasing thrust …
Ion Based Pressure Sensor For Pulse Detonation Engines, Jeffrey S. Zdenek
Ion Based Pressure Sensor For Pulse Detonation Engines, Jeffrey S. Zdenek
Theses and Dissertations
A high speed, durable, ion probe based pressure sensor is being investigated for use in pulse detonation engines. Traditional pressure sensors are ill suited for the high temperature and vibratory environment encountered in such engines. An alternative transient pressure sensing method is investigated for pressures behind a hydrocarbon flame. These flames generate ions that are quenched by collisions as a function of pressure. An experiment was devised to correlate the ion decay rate with the pressure using an ion probe well suited for the flow. A correlation has been established showing the ion decay rate is a function of pressure. …
Data Sorting And Orbit Determination Of Tethered Satellite Systems, Mark J. Faulstich
Data Sorting And Orbit Determination Of Tethered Satellite Systems, Mark J. Faulstich
Theses and Dissertations
Tethered satellite system end masses do not obey the normal laws of motion developed for determining their orbits. In addition, tethered satellite systems cause unique problems for satellite tracking because there are potentially two or more objects which may be tracked. This thesis provides insight into these issues by developing a method of sorting out observation data of tethered satellite systems into their appropriate end mass and providing an estimate on the center of mass orbit of the tethered satellite system. The method used to accomplish both of these tasks is optimization of an estimated simulated orbit. This orbit estimate …
Flow Around An Object Projected From A Cavity Into A Supersonic Freestream, Scott T. Bjorge
Flow Around An Object Projected From A Cavity Into A Supersonic Freestream, Scott T. Bjorge
Theses and Dissertations
The pressure and flow field of a supersonic flow over a cavity, with and without a store, was the focus of this experiment. One cavity geometry (length to depth ratio 3.6) was studied; the freestream Mach number and the placement of the store relative to the cavity floor were varied. The pressure spectra on the cavity floor were markedly different between Mach numbers of 1.8 and 2.9. The Mach 1.8 case exhibited clear spectral peaks consistent with predictions by Rossiter, whereas the Mach 2.9 flow did not. With the store placed within the free shear layer, the pressure fluctuations on …
Systems-Level Feasibility Analysis Of A Microsatellite Rendezvous With Non-Cooperative Targets, Allen R. Toso
Systems-Level Feasibility Analysis Of A Microsatellite Rendezvous With Non-Cooperative Targets, Allen R. Toso
Theses and Dissertations
The feasibility of using a microsatellite to accomplish an orbital rendezvous with a noncooperative target was evaluated. This study focused on identifying and further exploring the technical challenges involved in achieving a noncooperative rendezvous. A system engineering analysis and review of past research quickly led to a concentration on the guidance, navigation, and control elements of the microsatellite operation. The integration of control and orbit determination algorithms was investigated. A simple yet robust solution could not be found to meet reasonable rendezvous criteria, using essentially off-the-shelf technology and algorithms. System feasibility has been assessed to have a low probability in …
Structural Design And Analysis Of A Rigidizable Space Shuttle Experiment, Raymond G. Holstein Iii
Structural Design And Analysis Of A Rigidizable Space Shuttle Experiment, Raymond G. Holstein Iii
Theses and Dissertations
AFIT is in the process of designing a Space Shuttle experiment designated as the Rigidized Inflatable Get-Away-Special Experiment (RIGEX) to study the effects of microgravity on the deployment of rigidizable composite structures. Once in space, the experiment will inflate and rigidize three composite structures and perform a vibration analysis on each by exciting the tubes using piezoelectric patches and collecting data via an accelerometer. This paper presents the structural and vibration analysis of the RIGEX assembly and inflatable composite tubes using ABAQUS Finite Element Analysis (FEA) software. Comparison of the analysis has been carried out with Eigenvalue/Eigenvector experimentation by means …
Controlling The Primary Mirror In A Space-Based Telescope Utilizing An Eigenstructure Assignment Technique, Kim Kyongsoo
Controlling The Primary Mirror In A Space-Based Telescope Utilizing An Eigenstructure Assignment Technique, Kim Kyongsoo
Theses and Dissertations
The feasibility of using a sparse array of mirrors in a satellite system is being evaluated. This study focused on the control laws necessary for achieving the minimization of the effect of vibration which happens at the primary mirror of the satellite, by using the eigenstructure assignment technique. White Gaussian noise was assumed as the external input. AFRL has developed a 79 state model with 9 control inputs and 9 outputs, 3 sparse array mirrors, and a base. To extend the theory, a simplified model with 2 mirrors and a base which has 12 states, 4 control inputs and 8 …
Design Of A Space Borne Autonomous Infrared Tracking System, Matthew B. Kimsal
Design Of A Space Borne Autonomous Infrared Tracking System, Matthew B. Kimsal
Theses and Dissertations
Complete characterization of the space environment in support of the United States goal of space Situational Awareness is not currently achievable. When confronted with recent increases in the deployment and miniaturization of microsatellites by numerous nations, the questions of foreign space capabilities are magnified. This study sought to determine the feasibility of and experimentally demonstrate a microsatellite capability to autonomously loiter about and track a target satellite. Various methods of passive remote sensing were investigated to determine the best means of detecting and tracking a target in space. Microbolometer-based infrared sensors were identified as the best alternative. A representative system …
An Investigation Relating Longitudinal Pilot-Induced Oscillation Tendency Rating To Describing Function Predictions For Rate-Limited Actuators, Joel B. Witte
Theses and Dissertations
The purpose of this study was to investigate pilot-induced oscillations (PIO) and determine a method by which PIO tendency rating could be predicted. In particular, longitudinal PIO in the presence of rate-limited actuators were singled out for examination. Sinusoidal input/triangular output describing function techniques using Nichols charts were used. A new criterion dubbed Gap Criterion was calculated for PIO sensitivity. This criterion consists of the product of pilot gain necessary to cause PIO and the normalized maximum amplitude of the commanded actuator. These results were paired with simulator and flight test PIO tendency rating data. The PIO rating scale used …
Effect Of Dimple Pattern On The Suppression Of Boundary Layer Separation On A Low Pressure Turbine Blade, John P. Casey
Effect Of Dimple Pattern On The Suppression Of Boundary Layer Separation On A Low Pressure Turbine Blade, John P. Casey
Theses and Dissertations
Three dimple patterns were investigated to ascertain their relative effectiveness on controlling boundary layer separation from a low-pressure turbine blade. The three cases included a single row of dimples at 65% of the axial chord with 2.22 cm spacing, a single row of dimples at 65% of the axial chord with 4.44 cm spacing, and a two-row staggered pattern with rows at 65% and 76% of the axial chord with 4.44 cm spacing. The multiple row case was such that the center of the upstream dimple set at the midpoint between two downstream dimples. The dimple spacing was measured center-on-center. …
Magnetogasdynamic Flow Control Of A Mach Reflection, Brian E. Earp
Magnetogasdynamic Flow Control Of A Mach Reflection, Brian E. Earp
Theses and Dissertations
Two-dimensional regular and Mach reflections have been studied in the Mach 4.96 dual-solution domain for a 25° and 26° double-fin inlet. The steady-state computational Mach and regular reflections were subjected to magnetogasdynamic forces to determine whether these forces could be used as a possible flow control mechanism. The numerical code employed for this research solved the inviscid Euler equations with added source terms for the ponderomotive force and accompanying energy interactions. The 25° regular reflection was determined to be extremely sensitive to a decelerating Lorentz force. Transient application of the force led to the transition of the regular reflection to …
Axisymmetric Optical Membrane Modeling Based On Experimental Results, Brian J. Lutz
Axisymmetric Optical Membrane Modeling Based On Experimental Results, Brian J. Lutz
Theses and Dissertations
The United States Air Force, Department of Defense and commercial industry have recognized the great value of near-earth space development, specifically in satellites for use in communications, ground and space surveillance and more active roles. However, resolution, or the primary optic’s diameter, has been a limitation, especially for ground surveillance. Deployable optics has been investigated to allow larger optics in space and membrane optics has received increasing attention recently. The membrane’s flexible nature requires some passive and possibly active control to reduce optical distortion caused by manufacturing, deployment, or other effects during use. Piezoelectric surface controllers are one option to …
Experimental And Computational Analysis Of Modes In A Partially Constrained Plate, Robert M. Vandawaker
Experimental And Computational Analysis Of Modes In A Partially Constrained Plate, Robert M. Vandawaker
Theses and Dissertations
The field of structural health monitoring (SHM) attempts to reduce labor and cost by allowing technicians to monitor selected properties of an aircraft's structure to detect impending failure. This research examines methods to detect damage to a thermal protection system (TPS) tile using representative 2024-T3 aluminum plates. Plates are subjected to modal analysis in single and joined conditions in an attempt to provide the capability of sensing damage to a tile on the surface of a vehicle while the sensors remain on the superstructure of the airframe. Jointly, the development of a means to model the system using finite element …