Heiligers, J. (2010) Displaced geostationary orbits using hybrid low-thrust propulsion. In: 61st International Astronautical Congress, IAC 2010, 2010-09-27 - 2010-10-01, Prague, Czech Republic.
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In this paper, displaced geostationary orbits using hybrid low-thrust propulsion, a complementary combination of Solar Electric Propulsion (SEP) and solar sailing, are investigated to increase the capacity of the geostationary ring that is starting to get congested. The SEP propellant consumption is minimized in order to maximize the mission lifetime by deriving semi-analytical formulae for the optimal steering laws for the SEP and solar sail accelerations. By considering the spacecraft mass budget, the performance is also expressed in terms of payload mass capacity. The analyses are performed for both the use of SEP and hybrid sail control to allow for a comparison. It is found that hybrid sail control outperforms the pure SEP case both in terms of payload capacity and mission lifetime for all displacements considered. Hybrid sails enable payloads of 250-450 kg to be maintained in a 35 km displaced orbit for 10-15 years. Finally, two transfers that allow for an improvement in the performance of hybrid sail control are optimized for the SEP propellant consumption by solving an optimal control problem using a direct pseudo-spectral method. The first type of transfer enables a transit between orbits displaced above and below the equatorial plane, while the second type of transfer enables „customized service‟ in which the spacecraft is transferred to a Keplerian parking orbit when coverage is not needed. While the latter requires a modest propellant budget, the first type of transfer comes at the cost of a negligible SEP propellant consumption.
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