  To develop a spacefaring civilization, humankind must develop technologies
which enable safe, affordable and repeatable mobility through the solar system.
One such technology is nuclear fusion propulsion which is at present under
study mostly as a breakthrough toward the first interstellar probes. The aim of
the present paper is to show that fusion drive is even more important in human
planetary exploration and constitutes the natural solution to the problem of
exploring and colonizing the solar system.
