Bernd Dachwald
Interplanetary Mission Analysis for Non-Perfectly Reflecting
Solar Sailcraft Using Evolutionary Neurocontrol
In: Advances in the Astronautical Sciences, Vol. 116: Astrodynamics 2003 – Part II (Proceedings of the AAS/AIAA Astrodynamics Conference 2003, Big Sky (MT), USA) Univelt, San Diego, pp. 1247-1262 (AAS-03-579)
Solar sailcraft trajectories are typically presented for
high-performance sailcraft, assuming that the sail is an ideal reflector, or
considering the non-ideal reflectivity through an overall efficiency factor.
Otherwise, using traditional local trajectory optimization methods, it is
difficult to generate the required initial guess. A real solar sail, however, is
not a perfect reflector and a thorough trajectory simulation must therefore take
into account the optical characteristics of the real sail film that lead not
only to a reduced magnitude of the solar radiation pressure force but also to a
directional deviation.
Within this paper, minimal transfer times for rendezvous missions within the
inner solar system are presented for perfectly and non-perfectly reflecting
solar sailcraft, including a typical near-Earth asteroid rendezvous (1996FG3)
and a typical main belt asteroid rendezvous (Vesta). For the different solar
radiation pressure force models, the minimal transfer times are compared,
extending thereby the currently available data to moderate-performance sailcraft
of the first generation.
Using evolutionary neurocontrol as a global trajectory optimization method, it
is shown that there is a considerable increase of about 5-15% in the minimal
transfer times, if the non-perfect reflectivity of the solar sail is taken into
account. This fact must be considered for a thorough mission analysis. The
simplification that the non-ideal reflectivity of the sail can be modelled with
an overall sail efficiency factor should only be made for very preliminary
mission analyses.
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