Mr Stephenson, from Bristol, his woman Maryanne, 29, and his parents Brian, 66, and Sheralyn, 56, were striking dead at the scene in Titusville.
Monday’s crash, described by police as a “brutal collision” is being investigated.
Titusville Police Department said the conveyance’s satellite navigation was instructing a U-turn at a junction, probably due to a road blockage on SR 407, the unique route from the Space Center, back to a rented property in Davenport, where the kindred was staying.
Truck driver James Walsh, who was taken to hospital with trifling injuries, told police there was “nothing he could do” to avoid the bang, Deputy Chief Todd Hutchinson said.
The officer said Mr Stephenson’s “unfamiliarity” with the space could have contributed to the smash as he attempted the U-turn.
Police said Mr Stephenson’s confrere, who has not yet been named, was also on the family holiday but was not in the car.
It is believed he missed the falter trap and stayed at the rental property.
Mr Hutchinson said: “The vehicle they collided with was a massy duty Ford pick-up truck driven by a local man who said that the instrument pulled right in front of him and there was nothing he could do.”