Commissioned by the European Space Agency, this book details specific propulsion technologies as envisioned by 2020. Each technology has been considered in terms of concept, associated key technologies, development status and proposed roadmaps. The reader is led through all the steps that propulsion will likely take between now and the 2020s in a clear, concise, and detailed way, including market and feasibility perspectives when applicable.The 16 chapters follow a developmental logic. The material starts with the future of SRM, grounded on R&D done at present, goes through the development of LOX/HC liquid rocket engines, a technology based on U.S. and Russian work of the 60s and 70s. It then looks into future technologies, and systems just beginning to make their impact felt now, such as superconductivity applied to electric propulsion, MW-class ion engines (perhaps utilizing a nuclear power source), solar sails, laser propulsion, nuclear propulsion (such as the promising VASIMR), and ISRU.