MS thesis abstract - McGuire, Thomas
| Author: | McGuire, Thomas |
| Degree: | Masters of Science |
| SERC #: | 13-01 |
| File type: | PDF, 6368 kB |
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Aero-Assisted Orbital Transfer Vehicles Utilizing Atmosphere Ingestion
The atmosphere present in low Earth orbits can be used to provide working fluid to an electric propulsion system. As the craft plows through low Earth orbit (~175 - 225 km), incident gases are collected, ionized and routed through a high power electromagnetic thruster. A spacecraft utilizing this concept can generate thrust without expending on-board propellant. The performance of the system is explored in this thesis. An example mission of interest, orbital transfer of communications satellites from low Earth orbit (LEO) to geostationary Earth orbit (GEO) is presented and compared to the state-of-the-art techniques and a proposed solar thermal orbital transfer vehicle from the Boeing company. Performance increases possible with this system include lower cost per kilogram to the higher orbits, smaller and more cost effective launch vehicles for a given payload, and threefold increases in GEO capability of current launch vehicles.
In support of this concept, a large intake 'scoop' is required. Of the various options available, a solid hypersonic intake appears to be the simplest near-term option. The drag characteristics and low-density, high speed-ratio flow (speeds much greater than thermal speed) behavior around a solid-walled scoop is explored via a kinetic approach. A particle-in-cell method is used to model particle motion in a density and velocity field. The effects of surface interactions and collisions between neutral particles are treated with a Monte Carlo model. The general flowfield behavior is presented via density maps and velocity plots. The general scaling of the system drag, drag coefficient, and capture ratio are presented with variations in the cone angle of the scoop, intake radius, and assumed variables. The fine structure of the flow field is resolved within the limits of available computing power, showing a 'fuzzy' shock wave and weak bowshock effect. The last contributions of the model are drag and mass-capture values for a proposed reusable orbital vehicle.
Using the mission study and the scoop model, a high-level conceptual design of a reusable orbital transfer vehicle is presented. The proposed vehicle features a modestly-sized inflatable intake, 100 kW nuclear power source, and a spacecraft bus capable of years of operation. The mission consists of ferrying payloads from low Earth orbit to primarily geostationary orbits. The cycle time for conventional payloads is 4-5 months, allowing for many missions per year. The estimated revenue has the potential to be lucrative if development and operation costs are manageable.