Dry Dock is an option at the ship selector which allows storing of your currently active ships occupying regular ship slots. Dry Docked ships are moved into separate slots, freeing up the room for another ship to be ready for active duty. While stored, ships cannot be used, but they can be reactivated again at the ship selector if there is a free active ship slot.
When you Dry Dock a ship, all of its items are moved into your inventory, while visual customization is reset. Ship's name, Starship Mastery progress and saved Loadouts (with exception of tray configuration) will be retained. Dry Dock slots are for those ships that you wish to keep but do not want them taking up regular ship slots.
Each character without subscription will start with 5 Dry Dock slots, while Gold and Lifetime members start with 10. Additional 5 slots can be purchased from the C-Store for 400 (Services tab), with maximum of 305 slots available for Silver accounts and 310 for Gold or Lifetime.