The journey to the planets and maybe to the stars one day is an old dream of the humankind; to leave mother earth and dare the next, the interplanetary, step of exploration. “Dare mighty things” is a key slogan of these days of Percy’s arrival on the red planet. And this it is, space travel is still the great adventure of our days. Almost everybody, who is involved in space travel related activities, is passionate and enthusiastic and knows that she or he is part of something huge. Several technologies and research topics are part of space travelling. One cannot distinguish between the importance of the different involved technologies. But though, the basis and the origin of this journey is called propulsion. So, propulsion may not be more important than other technologies; but it is the fundament. And without propulsion there is basically no space exploration thinkable. For this reason, the following pamphlet is supposed to reflect the basic of propulsion in a rather naive way, which is more focusing on understanding the simple relations than to serve scientific wording. The further purpose is to derive from these relations a necessity of a very specific type of propulsion; the continuous electric high-thrust propulsion.