Docking fees
From Starsonata Wiki
Docking fees are no longer in the game, but they were once a fee based on the combined hull of all your docked ships. Every 15 minutes, the combined amount of hull in credits was deducted from the amount of credits you were carrying. For hardcore base-builders with many capacity augged thatches, these fees could run into millions.
The docking fees were initially added as a balance for the lack of a limit to the number of ships a player could own. A limit of 25 ships was added and eventually docking fees were removed.