Delta-v

A change in a spacecraft's velocity. A ship's delta-v capacity determines what trajectories it can follow and how much time it spends accelerating before it runs out of reaction mass and/or fuel. Low delta-v craft are limited to brief periods of engine use over the course of their mission, such as a rocket burn to achieve orbit around a planet, while a ship with high delta-v using a torch drive can follow a constant-acceleration trajectory for fast interplanetary travel.