This page of the guide to Void Bastards contains information on how to get torpedoes. Torpedoes can help you greatly in your journey through the galaxy as they can be used to destroy Void Whales and pirate ships.
In the initial part of the campaign, look for ships with a description informing you that they have a Torpedo Cache. After the start of this mission, remember to open all the interactive containers on that ship. Torpedoes will be stored in one of them.
Later in the campaign, you will encounter enemy ships with a description informing you about a Torpedo Rack.
Once you reach that ship, start looking for Torpedo Racks located in one or a few TUBES rooms.
Unfortunately, you never have one hundred percent guarantee that after you reach the TUBES room a torpedo will be on the rack. It can happen that a rack is empty - if that happens, look for another one. The picture above shows an example of a torpedo that can be collected.