I have no idea, except that money is not spared on missile troops, and they are kept well fed at all times to ensure their loyalty. If you seen videos of Soviet missile submarines with Jacuzzi, this is about that.

So far one thing is universally confirmed, launch officers get autonomy when "Contact is lost, and Moscow is confirmed destroyed." How much destroyed is counted as destroyed? Nobody knows, probably because officers themselves don't know, and don't delve into such scenario.