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The Solar Photon Thruster as a Terrestrial Pole Sitter
Author(s) -
MATLOFF GREGORY L.
Publication year - 2004
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1311.028
Subject(s) - physics , spacecraft , radiation pressure , sunlight , earth's orbit , solar sail , aerospace engineering , astronomy , engineering
A bstract : Geosynchronous satellites are invisible at high latitudes. A pole‐sitting spacecraft would have communication, climate‐studies, and near‐polar Earth observation applications. We present a pole‐sitter based on the solar photon thruster (SPT), a two‐sail variant of the solar sail using a large curved collector sail (always normal to the Sun) to direct sunlight against a much smaller thruster. Thrust decreases slower for an SPT than for a conventional sail arrangement as the angle between sunlight and the collector normal increases. An SPT pole‐sitter is offset from the terrestrial pole so that a component of Earth gravity balances the solar radiation‐pressure component pushing the SPT off station. The component of gravitational attraction of the Earth pulling the spacecraft towards Earth is also balanced by a solar radiation‐pressure component. Results are presented for 80‐100% collector/thruster reflectivities. For a spacecraft areal mass thickness of 0.002 kg/m 2 , collector and thruster reflectivities of 0.9, the SPT can be situated above latitude 45° at a distance of approximately 60 Earth radii. An SPT pole sitter would be affected by lunar perturbation, which can be compensated for by an on‐board rocket thruster producing 2 × 10 −6 g acceleration, a second SPT thruster sail thrusting against the influence of the Moon, or by directing a microwave beam against the spacecraft. Since an SPT pole sitter is in a position rather than an orbit, the effect of terrestrial gravitation limits the size and design of the payload package, which limits terrestrial target resolution.