Interplanetary spaceflight is also called interplanetary travel.
 They aren't practical for human crewed missions because they generally take years or decades, but may be useful for high-volume transport of low-value commodities if humanity develops a space-based economy
 It is difficult to use this method for journeys in the inner part of the Solar System, although it is possible to use other nearby planets such as Venus or even the Moon as slingshots in journeys to the outer planets

