Optimizing Electrodynamic Tether System Performance

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76123/1/AIAA-2009-6734-525.pd

Electrodynamic Tether System Analysis Comparing Various Mission Scenarios

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76450/1/AIAA-2005-4435-964.pd

Theory and Experimental Evaluation of Electrodynamic Tether Systems and Related Technologies.

The unique work presented in this thesis will first focus on integration of the latest theoretical and experimental electrodynamic aspects of an electrodynamic tether (EDT) into a time-independent simulation tool. Numerous elements have then be compared on a system level, including passive electron collection (or active ion emission) technologies, active electron emission technologies, bare versus insulated tether scenarios, boosting and de-boosting conditions, and various system element configurations. These results indicate that in many cases bare tether anodes are the optimal electron collection mechanism. In addition, it was shown that while hollow cathodes may be the best active electron emission technique, field emitter arrays result in less than 1% difference in system thrusting and use no consumables. This is based on the assumption that several-amp field emitter arrays can be built eventually. Issues that have troubled previous systems are the efficiency at which the tether collects current, the total surface area, and the bare tether geometry. Experimental work was conducted to compare the effects of porous flat-tape tether geometries to those of slotted and solid geometries. The experiment investigated these different tether configurations to better understand the physics involved and how to apply the different tether geometries to an EDT system. This work has resulted in evidence showing that, regardless of the orientation of the probe with respect to the flowing plasma, equivalent mass holed tapes outperform that of slotted tapes. These slotted tapes, in turn, outperform solid tapes on an equivalent mass basis. Modeling of hollow cathodes and other ion emission technologies has been a key concern to EDT technology and will have great implications to EDT systems. As tether systems venture outside of the ionosphere, there will likely need to be an alternate method for collecting electrons. An initial investigation using a hollow cathode as an electron collection source in the momentum exchange electrodynamic reboost (MXER) system was conducted. Results indicated that although this technology may produce a slight enhancement in thrust over a bare tether in altitudes over 1000 km, however, it requires too much consumable mass to be feasible.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57663/2/kfuhrhop_1.pd

Electron Emission for Electrodynamic Tether Systems in Space

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76291/1/AIAA-2004-3495-765.pd

A Comparison of Laboratory Experimental and Theoretical Results for Electrodynamic Tether Electron Collection Performance for Some Bare Tether Geometries

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76910/1/AIAA-2009-6659-508.pd

System Analysis of the Expected Electrodynamic Tether Performance for the ProSEDS Mission

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76057/1/AIAA-2003-5096-440.pd

Measurement of Cross-Section Geometry Effects on Electron Collection to Long Probes in Mesosonic Flowing Plasmas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77060/1/AIAA-2003-4950-410.pd

Current Collection to Electrodynamic Tether Systems in Space

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77109/1/AIAA-2004-5670-600.pd

Tethered Satellites as an Enabling Platform for Operational Space Weather Monitoring Systems

Tethered satellites offer the potential to be an important enabling technology to support operational space weather monitoring systems. Space weather "nowcasting" and forecasting models rely on assimilation of near-real-time (NRT) space environment data to provide warnings for storm events and deleterious effects on the global societal infrastructure. Typically, these models are initialized by a climatological model to provide "most probable distributions" of environmental parameters as a function of time and space. The process of NRT data assimilation gently pulls the climate model closer toward the observed state (e.g., via Kalman smoothing) for nowcasting, and forecasting is achieved through a set of iterative semi-empirical physics-based forward-prediction calculations. Many challenges are associated with the development of an operational system, from the top-level architecture (e.g., the required space weather observatories to meet the spatial and temporal requirements of these models) down to the individual instruments capable of making the NRT measurements. This study focuses on the latter challenge: we present some examples of how tethered satellites (from 100s of m to 20 km) are uniquely suited to address certain shortfalls in our ability to measure critical environmental parameters necessary to drive these space weather models. Examples include long baseline electric field measurements, magnetized ionospheric conductivity measurements, and the ability to separate temporal from spatial irregularities in environmental parameters. Tethered satellite functional requirements are presented for two examples of space environment observables

The Integrated Structureless Electrodynamic Propulsion (ISEP) Experiment

The objective of the Integrated Structural Electrodynamic Propulsion (ISEP) Experiment is to demonstrate the ability of multi-functional conductive structures to generate thrust and torque on a spacecraft system. The ISEP experiment will deploy several lightweight, conducting structures nominally 10 meters in length from a CubeSat and demonstrate generation of electrodynamic thrust and torque by driving currents along these booms. To affect current closure to the plasma, a combination of field emissive array cathodes (FEACs) along with simple lightweight, compact electron collectors, and miniature plasma contactors will be used to drive up to 1 ampere of current through the booms. The goal is to generate current flow through the conductors in such a way as to produce measurable thrust and torque on the host spacecraft, further validating the proposed concept. The data obtained on plasma contactor performance and electrodynamic thrust will validate the feasibility of the ISEP concept and provide crucial guidance on how to design future space systems incorporating structures with integrated electrodynamic (ED) propulsion. These results will also be of benefit to missions and concepts that utilize electrodynamic propulsion ranging from ED tether deorbit systems, ED drag makeup tether systems, as well as systems requiring efficient plasma contactors such as traditional electric propulsion and spacecraft charging subsystems