It naturally alters history, BTTF style, but only to the extent of creating the "once-around" time loop that results in the "second ship" sailing home in the end. The universe where the "first ship" was not saved from Christopher's spying eyes is a truncated one, only comprising the hours covered in the episode. That is, the rest of that timeline does not feature any out-of-time starships.
Timo Saloniemi
Timo Saloniemi