|M.Sc Student||Amit-Shapira Yonatan|
|Subject||Fuel-Efficient Cross-Track Distance Establishment in|
|Department||Department of Aerospace Engineering||Supervisor||PROF. Pinchas Gurfil|
|Full Thesis text|
Satellite formations have numerous applications. However, the initial establishment of such formations can require a high fuel expenditure, due to cross-track distance requirements. This work proposes a strategy to significantly reduce the fuel required for the formation establishment. Instead of direct out-of-plane maneuvers, it is suggested to use in-plane maneuvers, while utilizing natural forces, specifically the J2 perturbation. This methodology extends the establishment duration, and thus requires re-establishment of the along-track distance. First, some definitions regarding cross-track distance are made. The cross-track distance geometry and dynamics are explored. A few formation geometries are discussed, and collision avoidance is addressed. Second, analytical expressions for the cross-track distance and the establishment duration are derived for the case of impulsive-thrust, with and without drag. For most cases, the expected duration is reasonable, and the fuel saving is shown to be considerable.
For the continuous-thrust case, optimal control methods were used. The proposed strategy is proven to be optimal for an example problem with two cases: limited and unlimited thrust magnitude. Non-linear J2 dynamics were used, since the distances between the satellites during the cross-track distance establishment are large. Finally, the cases of impulsive and continuous-thrust are compared. It is shown that continuous-thrust is preferable in terms of fuel, for similar cross-track establishment durations.