Ship Range

Ship Range is the maximum distance a fleet can be from a planet or starbase.

Upon selecting a fleet, the is visually represented by a dashed border. By holding down the Control key, a tool tip will display showing the distance the tile under the mouse cursor is from the currently selected unit.

The larger the galaxy size, the longer the base.

Bonuses to
The primary way to increase is by adding a Life support module to a ship. The branch provides upgrades to life support, as well as direct  bonuses.

Other bonuses include:
 * The Adventuresome trait
 * The Determined ability
 * The Starfaring ability can construct the improvement
 * The anomaly in the Precursor Worlds DLC
 * Certain planet types construct ships with increased in the Precursor Worlds DLC