The Doctor knew the TARDIS' shields won't withstand Doomsday's strikes for long. It has no defense or battle systems. *i have to get closer to the sun..* he thought and told everyone "I'm going into space. Give me 5 minutes! I will be back..." The Doctor felt bad leaving everyone bit he had to try bringing superman back. TARDIS made it's iconic noise and it took off into space. He had to hurry not wanting doomsday to attack. This creature's force seemed to rival that of a Dalek. "Come on girl let's get close to the sun!"