For most spacecraft trajectories within the solar system, the expansion of the universe is not significant and can be safely ignored. The gravitational forces of the sun and planets, as well as other factors such as atmospheric drag and solar radiation pressure, are typically much more important for determining spacecraft trajectories within the solar system.

That being said, the expansion of the universe can be important for certain types of spacecraft missions, such as those that are designed to study the expansion of the universe itself or those that are designed to travel to other galaxies. In these cases, the expansion of the universe must be taken into account in the spacecraft's trajectory calculation.