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Full-Text Articles in Engineering
Satellite Formation Control Using Atmospheric Drag, Blake B. Hajovsky
Satellite Formation Control Using Atmospheric Drag, Blake B. Hajovsky
Theses and Dissertations
This study investigates the use of a linear quadratic terminal controller to reconfigure satellite formations using atmospheric drag actuated control while minimizing the loss of energy of the formation. The linearized Clohessy-Wiltshire equations of motion are used to describe the motion of the two-satellite formation about an empty reference position maintained at the formation center. Reconfigurations to final in-plane and elliptical formations are simulated at orbital radii of 6800 km and 7000 km, and the altitude loss and a ?v budget were recorded as performance measures for each reconfiguration. The final states of the spacecraft upon reconfiguration were propagated forward …
A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike
A Wind Tunnel Investigation Of Joined Wing Scissor Morphing, Christopher C. Dike
Theses and Dissertations
The Air Force Research Laboratory's Munitions Directorate has been looking to extend the range of its small smart bomb. Corneille [6] has conducted tests to determine the aerodynamic characteristics of joined wings on a missile and determine if joined wings are more beneficial than a single wing configuration. The concept of retrofitting wings on the bomb introduced an interesting problem: storage before deployment. This study conducted steady-state low speed wind tunnel testing of a joined wing configuration that morphed from a compact configuration for storage to a full extension. These steady-state tests examine differing sweep angles of the same joined …
Drag Estimates For The Joined-Wing Sensor Craft, Ryan L. Craft
Drag Estimates For The Joined-Wing Sensor Craft, Ryan L. Craft
Theses and Dissertations
This research studied the drag effects of the joined-wing sensor craft technology demonstrator being developed at the Air Force Research Laboratory (AFRL). Although many performance parameters have been studied and evaluated for this vehicle, to date no detailed drag estimates have been conducted for the AFRL configuration. Previous performance parameters of the aircraft have been estimated based solely on a constant lift-to-drag ratio assumption. Using the Air Vehicles Technology Integration Environment created by Dr. Maxwell Blair, and supplemented by MATLAB code, this study explored three different drag prediction methods to determine accurate estimates of both parasite and induced drag. The …
A Study In Drag Reduction Of Close Formation Flight Accounting For Flight Control Trim Positions And Dissimilar Formations, Michael T. Morgan
A Study In Drag Reduction Of Close Formation Flight Accounting For Flight Control Trim Positions And Dissimilar Formations, Michael T. Morgan
Theses and Dissertations
This thesis further defines the position of greatest fuel savings benefit for the trail aircraft flying in a two-ship formation. The HASC95 vortex lattice code was used for the examination. Investigations of a similar formation of F-16 aircraft and a dissimilar formation of a lead KC-135 aircraft and a trail F-16 aircraft were conducted. The analyses determined the effects of varying airspeed on the optimal position. In addition, flight control surface deflections were taken into account during the analyses. Both investigations trimmed the aircraft in the yaw and roll axes to determine the optimal savings. The similar analysis was conducted …
Investigation Of Atmospheric Reentry For The Space Maneuver Vehicle, Dennis J. Mcnabb
Investigation Of Atmospheric Reentry For The Space Maneuver Vehicle, Dennis J. Mcnabb
Theses and Dissertations
This study investigated the atmospheric reentry of the Space Maneuver Vehicle from low-earth orbit using an entry guidance concept similar to the Space Shuttle. The Space Maneuver Vehicle was modeled as a point mass with aerodynamic properties as determined using Newtonian impact theory. For the rarefied-flow transition regime bridging formulae are used to capture the effects of both hypersonic continuum flow and free molecular flow. Constraints to the reentry are developed and a reentry corridor is defined in the drag-velocity plane. Bank angle modulation is established as the primary means for controlling drag and range. The guidance concept is applied …
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 …
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 …
Vehicle Thermal Control With A Variable Area Inlet, Thomas R. Layne
Vehicle Thermal Control With A Variable Area Inlet, Thomas R. Layne
Theses and Dissertations
This study developed a variable area inlet and controller that regulated the temperature of an electrical component with ram air. The intent of the variable area inlet was to reduce vehicle drag by eliminating inefficiencies associated with component cooling and fixed area inlets. These inefficiencies arise from vehicles moving at varying speeds through varying air temperatures. The hardware model consisted of an electrical component mounted inside a right-circular cylindrical duct. The variable area inlet, mounted in the front of the duct, consisted of a butterfly valve that was actuated by a stepper controller acted on the feedback signal of a …
The Design And Development Of A Low-Speed, Low-Force Wind Tunnel Data Acquisition System With An Application To Bicycle Front Fork Spacing, Alan W. Elledge
The Design And Development Of A Low-Speed, Low-Force Wind Tunnel Data Acquisition System With An Application To Bicycle Front Fork Spacing, Alan W. Elledge
Theses and Dissertations
This thesis encompassed the design, development, and application of a low-speed, low-force data acquisition system for the AFIT 5-ft Wind Tunnel. The new data acquisition system was designed and developed to measure approximately 0.045 N (about 0.01 lbf) at nearly 64.4 km/h (40 mph). Verification of the capability was obtained through testing of a cylindrical model. As part of a technology transition program with Wright Laboratory, this new system was used to investigate bicycle front fork blade spacing in order to determine the optimal spacing for minimum drag. As for the minimum drag of a bicycle with an …
A New Drag Measurement System For Wind Tunnel Testing Of The Racing Bicycle And Rider To Determine A Low Drag Configuration, Brian A. Parker
A New Drag Measurement System For Wind Tunnel Testing Of The Racing Bicycle And Rider To Determine A Low Drag Configuration, Brian A. Parker
Theses and Dissertations
This study investigated the application of splitter plate effects to reduce the aerodynamic drag of the racing bicycle and rider system. A sensitive, low-force, beam-type, single-component balance was developed to provide drag measurements accurate to within 0.053 N (0.012 lbf). The performance of the new system was verified by comparing the measured drag on a three-dimensioaal, right-circular cylinder model, 0.127 m (5.0 in) in diameter and 0.610 m (24 in) long, with the results from a commercial balance and a other similar data. The bicycle and rider model consisted of a full-scale mannequin comprising only the hips, legs …