Here is the in-game information about Titanium-70. I have 5 units under my control, and would therefore like to take advantage of the 60% industry bonus to quickly mass an army.
The Endless Space Wiki states:
Titanium-70 is usually the first strategic resource researched by N-Way Fusion Plants. It is crucial for the development of missile technology and therefore Titanium-70 is needed to produce ships equipped with torpedoes and missiles.
This certainly seems true for Ion Torpedoes:
However, the information card for Unstable Torpedoes seems to contradict the Wiki. No Ti-70 requirement is listed:
In fact, according to the research page, Ion Torpedoes is the only module that needs Titanium-70! What should I believe? Should I assume that all missiles require Ti-70, and will benefit from the industry bonus? Or should I lade up my ships with Ion Torpedoes to take advantage of an extremely limited bonus?