Hadn't the helmet been damaged on the Satan Pit world already (glass broken)? or was there made any mention as to whether he changed helmets with the female astronaut he returned to the shuttle when fetching Rose?
Or is the helmet rather the one he got while leaving the ship in "42"?
Maybe even the TARDIS provides faculties to repair such things as helmet glass? 92.50.94.35 15:09, January 23, 2010 (UTC)
He replaced the broken helmet with the one he had taken from Ida. (Ida didn't have her helmet anymore when he exchanged her with Rose, and he never returned the helmet to any other crew member, so it has to be assumed)