Starting from Hasting's solution, based on previous work of Hayden/Winter, of the additivity problem, it is clear that certain geometric properties of the Stinespring space of a channel are crucially important for the understanding of channels. We will combine the theory of TRO's with a thorough analysis of Stinespring spaces in order to analyze the (potential) quantum capacity of channels. This is joint work with Li Gai and Rick LaRacurente.