The processes that space science missions follow, from proposal to a space agency, to successful mission completion, are numerous. The rationale behind approval of a mission and its payload cannot be presented in undergraduate courses. This book contains contributions from experts involved in today's space missions at various levels. Chapters cover mission phases and implementation, launchers and cruise strategies, including gravity assist maneuvers and different thrust scenarios. Although the book concentrates on the ESA program Cosmic Visions, its content is relevant to space science missions at all space agencies.