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Articles 151 - 165 of 165
Full-Text Articles in Space Vehicles
Steady Motions Of Rigid Body Satellites In A Central Gravitational Field, Cynthia A. Provost
Steady Motions Of Rigid Body Satellites In A Central Gravitational Field, Cynthia A. Provost
Theses and Dissertations
Numerous studies have been conducted on equilibrium orientations of objects moving under the influence of a central gravitational field. The results of many of these studies conclude that equilibrium conditions exist only when one of the principal axes coincides with the radius vector. Furthermore, these results assume that the center of force is located within the orbit plane, thereby tracing a great circle orbit. While these previous works have approximated the gravitational potential, this study examines relative equilibrium obtained by retaining an exact expression for the potential of a spherical primary body, as shown in a recent paper by Wang, …
A Virtual Environment For Satellite Modeling And Orbital Analysis In A Distributed Interactive Simulation, Andrea A. Kunz
A Virtual Environment For Satellite Modeling And Orbital Analysis In A Distributed Interactive Simulation, Andrea A. Kunz
Theses and Dissertations
In response to the need for a more realistic, interactive, and immersive space simulation system, the Joint National Intelligence Defense Staff JNIDS has sponsored the development of the Satellite Modeler at the Air Force Institute of Technology AFIT. The Satellite Modeler SM is a virtual environment VE application that allows analyst-users to enter a virtual near- Earth space environment and visualize realistic satellite models performing accurate orbital motion. The Satellite Modeler provides manipulation functions that allow a user to interact with multiple satellite models and satellite constellations. The system affords the user multiple vantage points within the environment to view …
Satellite Attitude Determination Using Linear Combination Of Models, Martin S. Chin
Satellite Attitude Determination Using Linear Combination Of Models, Martin S. Chin
Theses and Dissertations
In satellite analysis, it is often necessary to determine the attitude of a satellite from a two dimensional image of the satellite. This thesis describes work performed to determine the attitude of a satellite relative to a reference position. The attitude is described in terms of the scaling, rotation and translation of the reference that will result in a pose that can be projected to form the image of interest. The techniques used are based on finding coefficients for the linear combination of basis images and decomposition of a composite transformation matrix. The methods were initially modeled in Mathematica and …
Design Analysis Of A Combined Optical-Ladar Deep-Space Surveillance Satellite, Bradley K. Fournier
Design Analysis Of A Combined Optical-Ladar Deep-Space Surveillance Satellite, Bradley K. Fournier
Theses and Dissertations
This research determines the performance requirements of a combined optical LADAR space-based system in order to detect and track deep-space satellites from a near-earth orbit satellite. The research derives the necessary equations to compare both direct and heterodyne detection techniques. The selection of the candidate laser systems is based on current space developed LADAR technology. The selection of the detector, detector size, and optic size are determined in order to maximize the signal-to-noise ratio. The analysis includes the effects of beam truncation, obscuration, pixel geometry, and background radiance. The results indicate that the direct detection technique with a GaA1As semiconductor …
Crew Scheduling Of Space Operations Squadrons (Sops), Marianne Idzi
Crew Scheduling Of Space Operations Squadrons (Sops), Marianne Idzi
Theses and Dissertations
The mission of Space Operations Squadrons is continuous support of military satellite systems. The scheduling problem associated with conducting continuous operations is threefold. The first problem is finding cyclical crew shift schedules that meet daily manning requirements, adhere to current regulations, contain a minimum number of workshift changes during consecutive duty days, and maximize the non-duty time allowed between duty shifts. The second problem is to establish a sea of criteria to evaluate alternative shift schedules. Finally, the third problem is to minimize the number of personnel required to meet the scheduling requirements stated in the first problem. This study …
An Electromagnetically-Controlled Precision Orbital Tracking Vehicle (Potv), Richard E. Lawrence Jr.
An Electromagnetically-Controlled Precision Orbital Tracking Vehicle (Potv), Richard E. Lawrence Jr.
Theses and Dissertations
A propulsion configuration it defined for a precision orbital tracking vehicle (POTV) that employs electrodynamic forces to control vehicle attitude and position with respect to another spacecraft. A pair of electrically powered thrusters assist the POTV in position control. The vehicle can maintain continuous standoff at close range from another spacecraft in any direction, has docking capability, and has gross orbital transfer capability. These capabilities and the specific design derived for the POTV have been defined by the requirements of a postulated space facility (ASSET) that salvages structural aluminum from the external fuel tank of the space shuttle. Precision control …
A Synthetic Environment For Satellite Modeling And Satellite Orbital Motion, David L. Pond
A Synthetic Environment For Satellite Modeling And Satellite Orbital Motion, David L. Pond
Theses and Dissertations
Analysts tasked to study satellites moving in space must often rely on photographs to conduct their analysis. Often these photographs do not adequately represent how satellites move in space, their spatial relationships, or their interaction with other satellites. What analysts need is a three- dimensional synthetic environment that depicts satellites as they actually move and interact in space. This thesis addresses the early development of the Satellite Modeler (SM), a system that allows analysts to study, satellite motion and maneuvering of computer aided design (CAD) models of those satellites in a three-dimensional orbit. The system contains equipment that allows analysts …
An Approximate Solution For The Linearized Spinup Dynamics Of A Dual-Spin Spacecraft, David L. Kinney
An Approximate Solution For The Linearized Spinup Dynamics Of A Dual-Spin Spacecraft, David L. Kinney
Theses and Dissertations
An approximate solution is obtained for the linearized equations of motion for the spinup dynamics of a dual-spin spacecraft. The approximation is obtained from the WKB (Wentzel, Kramers, and Brillouin) method, which usually generates a divergent series. Comparison between the WKB solution and the numerically integrated solution are used to study the effects of spinup torque magnitude and the number of WKB terms used on the accuracy of the approximation. The WKB method generates accurate approximations for small spinup torques using as few as two terms in the series when no singularities are present in the WKB terms during the …
Passive Damping Of A Solar Array, Mark A. Scharpen
Passive Damping Of A Solar Array, Mark A. Scharpen
Theses and Dissertations
This study was an attempt to conceptualize, design, build, and test a constrained layer damping device that uses mechanical advantage for the purpose of increasing the damping of transient vibration of a five-bay planar truss. The aluminum truss was clamped to a fixed support and simulated a solar array. A conventional constrained layer treatment was designed, built, and tested to serve as a benchmark for comparison. For the conventional treatment, Plunkett and Lee's segmented constraining layer technique was used. The improved device, two three-layer sandwich beams spanning the two bays nearest the built-in end, were supported several inches away from …
Vibration Suppression In Large Flexible Space Structures Using Active Control Techniques, Chad T. Matheson
Vibration Suppression In Large Flexible Space Structures Using Active Control Techniques, Chad T. Matheson
Theses and Dissertations
This report investigates the use of active vibration control techniques applied to the PACOSS Dynamic Test Article as an experimental structure. In the course of the research, a mathematical model of the lightly damped experimental structure was created based on experimental data. This model was used in the design of two classes of controllers. The first class is pure rate feedback of the structure's measured states such that global stability is insured. The second type of controller investigated was an optimal controller (LQG) that was created using the truncated mathematical model. The rate feedback controller showed significant improvements in the …
Total Hemispherical Emittance Of Niobium-1% Zirconium Fuel Cladding For The Sp-100 Space Reactor, John E. Thomason Iii
Total Hemispherical Emittance Of Niobium-1% Zirconium Fuel Cladding For The Sp-100 Space Reactor, John E. Thomason Iii
Theses and Dissertations
Total hemispherical emittance was measured for the SP-100 reactor fuel cladding alloy (Nb-l% Zr). Based on a standard test method (ASTM C 835-82), experiments were conducted on a reference sample of oxidized stainless steel and then on a sample of actual cladding. The sample is heated in a vacuum by passing DC current through it until reaching equilibrium. Measurements are made of the electrical power dissipated in the sample and of the surface temperature. Using the Stefan-Boltzmann Law and some key assumptions concerning conductive and radiative heat transfer, the measured quantities are used to calculate emittance. Calculated values for unoxidized …
Analysis Of The Effects Of Removing Nose Ballast From The F-15 Eagle, Richard L. Bennett
Analysis Of The Effects Of Removing Nose Ballast From The F-15 Eagle, Richard L. Bennett
Theses and Dissertations
This study investigated the results of removing lead ballast from the nose section of the F-15 Air Superiority fighter. The goal of the investigation was to determine if aircraft handling qualities remained acceptable with the ballast removed, and also to determine what improvements in aircraft nose pointing authority resulted. Actual F-15 weight reports were used to calculate the worst case aft center of gravity location shift due to the ballast removal. Several configurations with different center of gravity locations (based on various amounts of lead weights removed) were used for comparison to the baseline aircraft. Moments of inertia were calculated …
A Correlation And Forecasting Analysis On Lost Satellites, Kenneth R. Norton
A Correlation And Forecasting Analysis On Lost Satellites, Kenneth R. Norton
Theses and Dissertations
The relationship between the size of the United States Air Force Space Command's lost satellite lists and thirteen other variables is investigated. The thirteen variables contain the Space Surveillance Center crew's effort to work the lost list, solar activity, geomagnetic field strength, and the number of observations received each day from seven space track sensors. To identify the relationship of cause and effect between the lost lists and the thirteen variables, simple and multiple linear regressions are used on a data set that begins on 1 January 1988 and ends on 31 December 1988. Multiple linear regression and basic time-series …
Application Of Influence Diagrams In Identifying Soviet Satellite Missions, Cary C. Chun
Application Of Influence Diagrams In Identifying Soviet Satellite Missions, Cary C. Chun
Theses and Dissertations
This thesis investigates the feasibility of applying influence diagrams to capture expert knowledge and incorporate decision theory to construct a Soviet satellite mission prediction model. Before a Soviet launch occurs, formulations of the model's prior probability distribution allows the input of expert knowledge and any available information. As the predictive variables of the model become known, the information is used to successively refine the estimate of the probable mission, thereby, reducing the uncertainty in the model. Discretizing is used to approximate continuous variables as discrete variables which successfully allows the combination of both variable types in a single influence diagram …
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 …