The ship could easily have been unmanned when the Doctor launched it. Deliberately, needlessly causing the death of an antagonist didn't use to be the Doctor's way.

He would always offer an alternative, even if the offer was not taken up. It had to be clear that the bad guy had chosen his own fate, after all it was a children's show.

Or is that just my rosy childhood coloured memories of Tom Baker's Doctor?  

My adult political mind tells me its a creeping americanisation of the character, next thing you know he'll be a cowboy!

regards
prixat