Artist’s impression of the Ramjet propulsion system. Credit: NASA

Since the 1960s, there has been speculation about a hypothetical propulsion method for interstellar space travel. Calculations at TU Wien (Vienna) show: it will remain science fiction.

In science fiction stories about contact with extraterrestrial civilizations, there is a problem: What kind of propulsion system could make it possible to bridge the enormous distances between the stars? It cannot be done with ordinary rockets like those used to travel to the moon or