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Full-Text Articles in Engineering
Optimal Control Of Electrodynamic Tethers, Robert E. Stevens
Optimal Control Of Electrodynamic Tethers, Robert E. Stevens
Theses and Dissertations
Low thrust propulsion systems such as electrodynamic tethers offer a fuel-efficient means to maneuver satellites to new orbits, however they can only perform such maneuvers when they are continuously operated for a long time. Such long-term maneuvers occur over many orbits often rendering short time scale trajectory optimization methods ineffective. An approach to multi-revolution, long time scale optimal control of an electrodynamic tether is investigated for a tethered satellite system in Low Earth Orbit with atmospheric drag. Control is assumed to be periodic over several orbits since under the assumptions of a nearly circular orbit, periodic control yields the only …
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Theses and Dissertations
This dissertation assesses the utility of tethered satellite formations for the space-based remote sensing mission. Energy dissipation is found to have an adverse effect on foundational rigid body (Likins-Pringle) equilibria. It is shown that a continuously earth-facing equilibrium condition for a fixed-length tethered system does not exist since the spin rate required for the proper precession would not be high enough to maintain tether tension. The range of required spin rates for steady-spin motion is numerically defined here, but none of these conditions can meet the continuously earth-facing criteria. Of particular note is the discovery that applying certain rigid body …
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 …
Orbital Maneuvering Using Electrodynamic Tethers, Hakan San
Orbital Maneuvering Using Electrodynamic Tethers, Hakan San
Theses and Dissertations
Considerably short electrodynamic tethers can be used as a low-thrust propulsion system with minimum or no mass expenditure. The propulsive force is generated by inducing a current flow through the tether which interacts with the magnetosphere of the planet (i.e. Earth, Jupiter and other planetary bodies with magnetosphere). The basics of electrodynamic tether systems have been studied and successful experiments such as boost and de-boost of spacecraft have been conducted in the past. This study presents a simple guidance scheme for the current in the tether in order to perform orbital maneuvers. The general perturbation equations are used to develop …
Analysis Of Tethers In Sampling Near Earth Objects, John W. Wong
Analysis Of Tethers In Sampling Near Earth Objects, John W. Wong
Theses and Dissertations
This study investigated the feasibility of a SAIC proposal to sample Near Earth Objects (NEOs) from an orbiting spacecraft using a tethered landing device. The parameters for suitable targets were derived from an analysis of a proposed point design as applied to current knowledge of NEOs. Tether strength and lifetime for the point design were also assessed. First order modeling of tether dynamics showed that deployment and attachment to a NEO are feasible. The dynamics of retrieving a sample via a crawler unit which crawls up the tether requires further exploration.