This book gives an account, as little biased as possible, on human space missions beyond low Earth orbit in general, and specifically to the planets of the solar system. The importance of advanced propulsion is stressed and the mathematical methods needed to design missions based on them are described. The included computer code allows the user to assess the feasibility of the various missions using different propulsion systems and how advancements in propulsion can allow humankind to become a true spacefaring civilization. As opposite to the majority of books dealing with mission design, where the subject is usually dealt with in a highly mathematical way, here an attempt is made to avoid as much as possible the mathematical complexities and to focus on the practical aspects of the design. However, the equations needed to make numerical analysis and simulations of the missions are described and discussed. An original computer code is included in the book, and an appendix helps the reader to understand how to use it. The code is different from existing ones since its main aim is to be user friendly and to allow the user to make a preliminary design of interplanetary missions aimed to planets and their satellites, comets or asteroids.