The material in this book is essential for engineers studying and working in the field of spacecraft design. Its emphasis is on the bus rather than the payload. The working of spacecraft systems of various types are described—mechanical, electrical, propulsion, thermal, control, etc., both on-board and ground-based—together with essential disciplines which ensure that they work reliably and in harmony with each other. The scene is set by a description of the operating environments of the spacecraft, and of the fundamental dynamic behaviour that governs its trajectory and its orientation. This is then translated into options that meet specific mission objectives that are set by the payload. This second edition is an update of the first, and includes two extra chapters. The first is on Mechanisms, and addresses the problems posed by their requirement for extreme reliability and longevity in the harsh environment of space—and some solutions. The second is on the subject of Systems Engineering, and it includes examples of applications to different types of mission.