Why can't I launch units from my transport?

[Silent Sorrow]

Arrghh! I went through all the trouble of building a large transport before loading it up with population, small fighters and small satelites. Now the game won't let me launch the satellites or fighters. What's the problem? Can you only launch these units from actual carriers (as in the designation from the design phase)?

Needless to say, this has severely screwed up a major attack of which I was in the middle of undertaking. (And why, for the love of God, is stuff like this unexplained in that mostly crappy "manual"?)