The Torpedo Bay 20Q was introduced in 0.4.5. It was meant for a later version but was moved ahead. As of 0.5.3 it can store almost all types of torpedoes.
The torpedo bay 20Q can store different ammunition types: photon-, quantum-, tricobalt-torpedo, and EPC missiles (for the Abh Electromagnetic Projection Cannon). It's main starting storage type if quantum tropedo, a necessary setup for AI use.
By toggling the UI button it can switch its storage to a different type of ammunition. When changing ammo, the game will automatically clean out the storage and any torpedo will be lost.