This set of lectures starts with a general view of space science missions, from their rationale to the sequence in which they have been defined in the last decades. A crucial aspect in the definition of the mission is its launch and cruise strategies. In the case of solar system bodies, also orbital insertion becomes a major issue in the mission planning. The different strategies based on gravity assists maneuvers, chemical and electric propulsion are detailed. As case examples the Rosetta, Bepi-Colombo and Solar Orbiter missions are studied in their different scenarios.