On each side of the main engine exhaust hole there are two large devices called Tail Service Masts. They are 15 ft. long, 9 ft. wide and rise 31 ft. above the MLP deck. Their function is to provide umbilical connections for liquid oxygen and liquid hydrogen lines to fuel the external tank from storage tanks adjacent to the launch pad. Other umbilical lines carry helium and nitrogen, as well as ground electrical power and connections for vehicle data and communications.At launch, the umbilicals are pulled away from the Shuttle and retracted into the masts where protective hoods rotate closed to protect the umbilicals from possible exhaust flame damage.
Sorry, I am not sure what you are talking about.Do you mean the two little flat towers, with the round top that end just at the top surface of the rear part of the wings?/Armin
