Autonomous systems are becoming an accepted part of life, but questions are often raised about the ethics of their use. The debates can be at the philosophical level, with arguments about which ethical theory or moral code should be applied, or even if technologies for specific applications should be banned. These debates are usually very general even when discussing systems which are the subject of the book: those which interact with humans and have both some level of autonomy and a physical structure. More practical arguments arise about the legal framework that should be used when the system is in use, usually demonstrating that this new technology requires new laws or new interpretations of the existing ones. These debates and arguments have an extensive literature and are often given wide publicity, especially when artificial intelligence or autonomous road vehicles are included. The book examines autonomous systems in the context of their wider ethical and legal environment with equal weight given to both engineering and legal principles. The book has a bias to aerospace applications but shows how system engineering principles are applied to highly automated systems in other fields such as autonomous vehicles and robots.