Certain more intangible resources include Supply Points and Capital Ship Crews. Supply Points are used up when ships are purchased, and cannot be accumulated, acting as a population cap for the player's fleet. Capital Ship Crews and Supply Points are both required for the construction of powerful capital ships; regular capital ships require one crew, while the giant titans in the "Rebellion" expansion require two. A player's maximum Supply Points and Capital Ship Crews can be upgraded, but increased Supply Points require more logistical support, imposing a permanent reduction on the player's income.