 Such a vehicle could not fly without modification, because the S-II was designed to operate in the near-vacuum of high altitude space.Atmospheric thrust suppression reduced the five Rocketdyne J-2 engines' of vacuum thrust to at sea level, insufficient to lift the weight of the two stages, even without a payload, off of the ground.This required that the S-II be either refit with higher thrust engines, augmented with solid rocket boosters, or both.