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Articles 1 - 30 of 68
Full-Text Articles in Engineering
1998 Reduced Gravity Student Flight Opportunity: Thin Film Extrusion In Microgravity, Jason Duckworth
1998 Reduced Gravity Student Flight Opportunity: Thin Film Extrusion In Microgravity, Jason Duckworth
Honors Capstone Projects and Theses
No abstract provided.
Experimental Investigation Of The Influence Of Molecular Weight On Mixing And Penetration In Supersonic Dissimilar Gaseous Injection Into A Supersonic Cross-Flow, Troy A. Giese
Theses and Dissertations
In pursuit of a more efficient and effective fuel-air mixing for a SCRAMjet combustor, this study investigated relative near field effects of molecular weight on mixing and penetration of different gaseous injection into a supersonic (M=2.9) cross flow. Helium and argon gas were chosen as injectants because of the large differences in molecular weights. Also, mixing enhancement was observed by injecting the traverse gas jet parallel to the compression face of a ramp. Color schlieren photography was used to identify the shock structures and interactions in the flow field. Measurements of mean flow properties were used to establish the jet …
Experimental Investigation Of Water Spray Cooling Characteristics Of A Solid Heated Surface, Rainer F. Ponzel
Experimental Investigation Of Water Spray Cooling Characteristics Of A Solid Heated Surface, Rainer F. Ponzel
Masters Theses
Water spray cooling characteristics of a solid heated surface were investigated to better understand the physical phenomenon of nucleate boiling heat transfer for full cone sprays. An experimental test loop was developed to conduct the spray cooling experiments. A uniform heat flux condition was assumed, and the liquid flow rate and nozzle orifice diameter were selected as the main variables. Two water temperatures were chosen to perform the study. Saturated water spray was utilized to measure the wall superheat temperature. Subcooled water spray was applied to investigate the effect of water spray in the single-phase regime.
Experiments conducted using the …
Applying Flywheel Energy Storage To Solar Electric Orbital Transfers, Mark W. Marasch
Applying Flywheel Energy Storage To Solar Electric Orbital Transfers, Mark W. Marasch
Theses and Dissertations
This study investigated the application of flywheel energy storage to minimum time, constant thrust orbital maneuvers using electric propulsion. The advantages of using stored energy to continue electric thruster operations while in eclipse were explored. The boundary value problems for several schemes of energy use were examined, and numerical solutions were found. Results of simulations utilizing energy storage were compared to results without energy storage. Schemes incorporating energy storage were found to have advantages in terms of propellant mass used, time spent in transit, and deliverable payload.
Velocity Profiles And Skin Friction On A Ribletted Flat Plate In Adverse Pressure Gradient., Richard D. Branam
Velocity Profiles And Skin Friction On A Ribletted Flat Plate In Adverse Pressure Gradient., Richard D. Branam
Theses and Dissertations
This project investigated the flow field characteristics over a flat, ribletted plate and the effects of an adverse pressure gradient on this flow field. Testing examined the development of the flow over the ribletted plate from laminar through fully turbulent flow fields. The flow field states (laminar, transitional, and turbulent) were determined using local turbulence intensity values and boundary layer profiles. Several parameters were examined to help better describe the flow characteristics, boundary layer profiles, and influence on skin friction drag. The skin friction drag coefficients were calculated using a numerical integration technique to determine an average value and scaled …
Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark
Multiple Model Adaptive Estimation And Control Redistribution Performance On The Vista F-16 During Partial Actuator Impairments, Curtis S. Clark
Theses and Dissertations
Multiple Model Adaptive Estimation with Control Reconfiguration (MMAE/CR) capability to estimate and compensate for partial actuator failures, or "impairments" is investigated using the high-fidelity, nonlinear, six-degree-of-freedom, VISTA F-16 simulation which currently resides on the Simulation Rapid-Prototyping Facility (SRF). After developing a model for inserting partial actuator impairments into the VISTA F-16 truth model, research begins with a battery of single actuator impairment tests. This stage of research explores the capability of the existing MMAE algorithm to estimate single, partial actuator impairments, and helps to define refinements and expansions needed in the MMAE algorithm for the second phase of research: the …
Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb
Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb
Theses and Dissertations
This research effort investigated the effects of evaporation of water on the heat transferred to the wall of the diverging portion of a porous walled nozzle The AFIT High Pressure Shock Tube was used with a two-dimensional Mach 3 nozzle. One flat surface of the nozzle was fitted with a layer of porous stainless steel from the nozzle throat to the exit. This porous material was saturated with water to simulate liquid transpiration cooling. Surface temperature data was taken in this region using fast response coaxial thermocouple. Heat transfer was determined from the surface temperature history. Data was taken for …
Optimal Non-Coplanar Launch To Quick Rendezvous, Gregory B. Sears
Optimal Non-Coplanar Launch To Quick Rendezvous, Gregory B. Sears
Theses and Dissertations
The purpose of this study was to determine the feasibility of launching a Delta Clipper-like vehicle on an optimal, non-coplanar trajectory to rendezvous with an earth orbiting object in one orbit or less. The focus of the research was to determine what such a trajectory would look like, and to determine the cost, in payload mass, of flying such a trajectory. A model for the ascent trajectory was developed using the dynamics equations of motion, an atmosphere model, and an aerodynamic model for the DC-Y concept vehicle. A boundary value problem was posed and solved for a coplanar rendezvous. The …
Space Shuttle East Coast Abort Modes For High Inclination Launches, Richard K. Neufang
Space Shuttle East Coast Abort Modes For High Inclination Launches, Richard K. Neufang
Theses and Dissertations
This study investigated the possibility of abort landing the Space Shuttle at east coast airports when launched at inclinations of 51.6 degrees or more. Computer modeling was used to characterize both the Shuttle launch out of Cape Canaveral and two methods of unpowered abort descents from various points in the launch following Solid Rocket Booster SRB separation. The first method used varying values of pitch and roll held constant to control the descent. By plotting the latitude and longitude of the point in the descent when the nominal landing altitude was achieved against locations of east coast airports it was …
Development And Validation Of An Experimental Test Rig For Electrohydrodynamic Enhancement Of Forced Convective Heat Transfer, William T. Caldwell
Development And Validation Of An Experimental Test Rig For Electrohydrodynamic Enhancement Of Forced Convective Heat Transfer, William T. Caldwell
Theses and Dissertations
This report details the development of a facility for the experimental investigation of electrohydrodynamic (EHD) enhancement of forced convection heat transfer. The test facility was developed for the Thermal and Transparencies Laboratory (TATLAB), Air Force Research Laboratory (AFRL), for use in future research into the applicability of EHD for the miniaturization of Air Force heat exchangers. During this research, a closed l6op, medium scale electrohydrodynamic test rig was developed and brought online. The test fluid loop was integrated with a data acquisition and parameter control system. Basic loop and fluid performance testing was accomplished through the use of a 3mm …
Orbit Estimation Using Track Compression And Least Squares Differential Correction, Vincent J. Chioma
Orbit Estimation Using Track Compression And Least Squares Differential Correction, Vincent J. Chioma
Theses and Dissertations
This thesis develops two methods of compressing a track of radar observations of a satellite into a single state vector and associated covariance matrix, and a method of estimating orbits using results from multiple tracks. The track compression uses least squares differential correction to determine a state vector at the central observation time. The resulting state vectors and covariance matrices are then used to estimate the satellite's orbit, also using least squares differential correction. Numerical integration using two-body, J2 and an atmospheric drag model is used to represent the dynamics. This orbit estimation produces a state vector which includes …
Satellite Integrated Power And Attitude Control System Design Study, Stephen A. Fischer, Dwight D. Fullingim, Brian L. James, James M. Valenti, Jorg D. Walter, Paul J. Cotter, William A. Seeliger
Satellite Integrated Power And Attitude Control System Design Study, Stephen A. Fischer, Dwight D. Fullingim, Brian L. James, James M. Valenti, Jorg D. Walter, Paul J. Cotter, William A. Seeliger
Theses and Dissertations
Technological advances have brought Flywheel Energy Storage (FES) systems to the point where they can be used in satellites as replacements for chemical batteries. Flywheels have characteristics that may overcome limitations inherent in batteries. These characteristics include high specific energy, minimal degradation over time, and precise knowledge of charge level. A further advantage of flywheels is that, in a combined system, they can be used to replace traditional attitude control hardware. These Integrated Power and Attitude Control Systems (IPACS) show the potential to have less mass than the systems they replace. The question this study seeks to answer is, "In …
Optimal Orbit Insertion Strategies Using Combined High And Low Thrust Propulsion Systems, Darren W. Johnson
Optimal Orbit Insertion Strategies Using Combined High And Low Thrust Propulsion Systems, Darren W. Johnson
Theses and Dissertations
Low thrust electric propulsion systems are becoming sufficiently mature to consider their use as primary propulsion for orbital transfer in place of high thrust chemical systems. Instead of facing an either/or situation, it may be advantageous to use both types. This effort demonstrates a technique for finding orbital transfer strategies that use both high and low thrust propulsion systems and which result in optimal tradeoffs of the performance parameters cost of orbit insertion, total orbit transfer time, and available spacecraft mass at final orbit. These performance parameters are calculated as a function of the fraction of orbit transfer from Low …
Flow Field And Loading Analysis On A Wrap-Around Fin Missile, Thomas C. Mcintyre
Flow Field And Loading Analysis On A Wrap-Around Fin Missile, Thomas C. Mcintyre
Theses and Dissertations
Wrap-around fin (WAF) missiles offer packaging benefits but experience rolling moments due to the curved fin design. Rolling moments stabilize unguided projectiles, but cause guidance and control problems for future guided applications. Understanding the flow field in the vicinity of the fins is critical to future missiles. Fin pressure profiles were characterized with pressure-sensitive paint. Two rectangular four-fin constructions were tested-one solid and one with a rectangular hole (slotted fin). Static pressure data were divided by free-stream total pressure for presentation. Tests were conducted at Mach numbers of 2.15, 2.28, 2.41, 2.86, 3.25, 3.50 and 3.83. Reynolds numbers based on …
Warning Times And Impact Predictions Of Asteroids And Comets On A Collision Course With Earth, Ahren D. Heidt
Warning Times And Impact Predictions Of Asteroids And Comets On A Collision Course With Earth, Ahren D. Heidt
Theses and Dissertations
This study investigates the amount of data and time necessary to accurately predict Earth impacts of Earth Crossing Objects (ECOs). Trajectories are simulated by numerically integrating in an N-Body system. Given final impact parameters, the trajectory is propagated backwards to an earlier time, creating initial conditions and simulated observation data at requested intervals to which Gaussian random noise is introduced. Utilizing a Bayes Filter to estimate position and velocity from the simulated observation data, the estimate is then propagated forward in time to determine whether or not an impact can be accurately predicted. State vectors and covariance matrices are then …
Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer
Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer
Theses and Dissertations
Recent research efforts have applied the receding horizon Model Predictive Control (MPC) strategy to linearized high performance aerospace systems. The research contained in this thesis used these recent results in order to apply the MPC strategy to a nonlinear high performance aerospace system, specifically an F-16 fighter aircraft model. The model was commanded to follow dynamic trajectories of roll angle and altitude. Further, adaptive constraint techniques were used to improve system tracking. To accomplish these tasks, code and block diagrams were generated using the commercial software packages of Matlab and Simulink. Numerous simulations were conducted with the goal of achieving …
Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr.
Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr.
Theses and Dissertations
This research project investigated the design, construction and evaluation of a pseudorandom code generator for communication and navigation system applications. These types of codes include spreading codes, Gold codes, Jet Propulsion Laboratory (JPL) ranging codes, syncopated codes, and nonlinear codes. Such waveforms are typically used in communication and navigation system applications. The code generator uses the Stanford Telecom STEL-1032 Pseudorandom Number (PRN) coder. A coder interface was designed and constructed for manual data entry to the registers of the PRN coder. The code generator is capable of independently clocking and generating all possible codes with lengths up to 4,294,967,295 bits. …
An Analysis Of Current Interruption Upon The Behavior Of Light Bulb Filament During Initial Aircraft Impact In Support Of Aircraft Accident Investigations, Daniel J. Larow
Master's Theses - Daytona Beach
The purpose of analyzing annunciator panels, warning, and indicator lamps is to determine the state ("on" or "off") of each light bulb immediately before the impact. Determination of the state of lamps may help investigators determine the probable cause of the accident. The information gained from the lamp's filaments may be used to infer the aircraft's operational parameters prior to impact and to a qualitative appreciation of the severity of the accident. It is generally agreed that upon impact the filament of an unlit bulb will fracture without deformation and the filament of a lit bulb will display plastic deformation …
Flightlines, Vol. 6, No. 1, Jeffrey A. Johnson
Flightlines, Vol. 6, No. 1, Jeffrey A. Johnson
Flightlines Newsletter
No abstract provided.
Review Of The Challenger Launch Decision: Risky Technology, Culture And Deviance At Nasa, Peter F. Meiksins
Review Of The Challenger Launch Decision: Risky Technology, Culture And Deviance At Nasa, Peter F. Meiksins
Sociology & Criminology Faculty Publications
Reviews the book "The Challenger Launch Decision: Risky Technology, Culture and Deviance at NASA," by Diane Vaughan.
Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun
Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun
Theses and Dissertations
An analysis and assessment of three mechanisms describing plasma/shock wave interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of ion-acoustic wave damping, post-shock energy addition and thermal inhomogeneities were examined by numerically solving the Euler equations with appropriate source terms adapted for each mechanism. Ion-acoustic wave damping was examined by modeling the partially ionized plasma as two fluids in one spatial dimension using the Riemann problem as a basis. Post-shock energy addition in the form of nonequilibrium vibrational energy relaxation was also examined in one spatial dimension using the Riemann problem as a …
Trends. The Cassini Mission To Saturn: Plutonium As Propaganda, Ibpp Editor
Trends. The Cassini Mission To Saturn: Plutonium As Propaganda, Ibpp Editor
International Bulletin of Political Psychology
The author discusses the plutonium-carrying Cassini mission to Saturn.
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society Vol. 3, No. 1, Tae Hoon Oum, Brent D. Bowen, Uno Aviation Institute
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society Vol. 3, No. 1, Tae Hoon Oum, Brent D. Bowen, Uno Aviation Institute
Faculty Books and Monographs
UNOAI Report 97-7
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society Vol. 1, No. 3, Tae Hoon Oum, Brent D. Bowen, Uno Aviation Institute
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society Vol. 1, No. 3, Tae Hoon Oum, Brent D. Bowen, Uno Aviation Institute
Faculty Books and Monographs
UNOAI Report 97-4
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society, Vol. 1, No. 1, Tae Hoon Oum, Brent Bowen, Uno Aviation Institute
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society, Vol. 1, No. 1, Tae Hoon Oum, Brent Bowen, Uno Aviation Institute
Faculty Books and Monographs
UNOAI Report 97-2
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society Vol. 2, No. 2, Tae Hoon Oum, Brent D. Bowen, Uno Aviation Institute
The Conference Proceedings Of The 1997 Air Transport Research Group (Atrg) Of The Wctr Society Vol. 2, No. 2, Tae Hoon Oum, Brent D. Bowen, Uno Aviation Institute
Faculty Books and Monographs
UNOAI Report 97-6
Reorientations Of Flexible Spacecraft Using Momentum Exchange Devices, Kevin A. Ford
Reorientations Of Flexible Spacecraft Using Momentum Exchange Devices, Kevin A. Ford
Theses and Dissertations
We study rest-to-rest reorientations of flexible spacecraft using momentum exchange devices. A new and concise form of the equations of motion for a rigid body containing a cluster of gimbaled momentum wheels is developed using the Euler-Newton approach. Special restrictions of the gimbaled momentum wheel equations yield equations of motion for the momentum wheel cluster and the control moment gyroscope cluster. A mathematical model of a free spacecraft with Euler-Bernoulli appendages is developed. Using the assumed modes method, a complete set of equations is developed which describes the dynamics of a spacecraft with flexible appendages and gimbaled momentum wheels. Special …
Fiber Volume Fraction Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Coghlan
Fiber Volume Fraction Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Coghlan
Theses and Dissertations
The purpose of this study was to determine the effects of fiber volume fraction on the fatigue behavior of Silicon Carbide fiber-reinforced Titanium alloy, SCS-6/Ti-15-3. Three fiber volume fractions were investigated; 15%, 25%, and 42%. The tests were performed under fully-reversed, strain-controlled conditions at 427 °C. The primary objectives of this study were to develop a fatigue life diagram and to document the damage and failure mechanisms. Compressive loads on the slender specimens were kept from buckling the specimens through the use of a buckling guide. This device allows unrestricted axial movement of the composite, while preventing any out-of-plane motion. …
Improved Load Alleviation Capability For The Kc-135, Adam L. Mortensen
Improved Load Alleviation Capability For The Kc-135, Adam L. Mortensen
Theses and Dissertations
The Air Force will greatly increase its use of Unmanned Aerial Vehicles (UAVs) in the next century and the latter part of this decade. These UAVs will require refueling like their manned counterparts. The KC-135 and the KC-10 are candidates to provide this refueling task. The KC-10 is equipped with an automatic load alleviation system on its refueling boom which minimizes radial loads at the receiver of the aircraft being refueled. The KC-135 does not have such a system on its boom. Because the boom operator relies on visual cues to tell him when the boom is bending to adjust …
Relative Equilibria Of A Rigid Satellite In A Central Gravitational Field, Jeffrey A. Beck
Relative Equilibria Of A Rigid Satellite In A Central Gravitational Field, Jeffrey A. Beck
Theses and Dissertations
We apply noncanonical Hamiltonian methods to examine relative equilibria of a rigid body in a central gravitational field. These equilibria correspond to fixed points of a reduced set of equations expressed in a rotating frame and are representative of an orbiting satellite with fixed attitude relative to an observer rotating at the orbital rate. Our objective is to clarify the relationship between the classical approximation and a recent noncanonical Hamiltonian treatment. In contrast to the classical approximation, the orbital and attitude equations of motion for the noncanonical system remain coupled and the general solution is a circular orbit for which …