The torpedo launch tube construction display lists the torpedo launcher systems that you have both the resources and tech level to build at this time. When you build a torpedo launcher it remains in storage at the starbase until you fit the torpedo launcher onto a hull.
The display shows the cost to build this torpedo launcher in megacredits and the amount of material needed. The display also shows the amount of money in the planet's treasury and materials remaining on the planet ready to be made into whatever you see fit.
Torpedo launch tubes aim and arm standard torpedoes. A standard torpedo takes up one kiloton of cargo space. In combat the torpedo is moved from the cargo hold into the launch tube. The torpedo is the most powerful weapon on any starship and has a range second only to fighters. Major drawbacks of torpedoes are the cargo spaces needed to hold the torpedoes and the mass of the torpedo launchers.
A launcher is only able to fire torpedoes designed for it. For example, a mark 5 photon torpedo can only be fired from a mark 5 photon torpedo launcher.
For safety reasons a starship may only carry torpedoes that match the torpedo launch system it has. Freighters may not transport torpedoes.
Ships can convert their torpedoes into deep space mines.