AMALIA MISSION ANALYSIS - Lunar assisted transfer
The velocity variation needed to transfer a spacecraft from a Low Earth Orbit (LEO) to the Geostationary Orbit depends on the height and inclination of the LEO. The usual Geostationary Transfer Orbit (GTO) is a two impulse Hohmann transfer with plane variation distributed between the two impulses. However it can be easily shown that for inclination greaten than 40° any three impulse bielliptic geostationary transfer is convenient with respect to the classical GTO.
For higher apogees, it is appropriate to consider the lunisolar effect and to investigate whether it is possible to take advantage of this effect in order to reduce the ΔV needed to reach the geostationary orbit. In fact, the ΔV can be reduced if a suitable lunar fly-by is performed and such savings can be rather relevant for highly inclined LEO justifying the longer time needed to the transfer as well as the introduction of launch windows.
It will be shown that the ΔV needed in a geostationary transfer assisted by lunar fly-by is an increasing function of the apogee altitude. In such dynamical system the Moon drives the spacecraft towards the lunar orbit and the geostationary perigee and inclination are achieved after the lunar encounter. It turns out that this lunar transfer is more economical with respect to the classical one.