Factual error: At the start the Robinsons are playing a game of fish, in weightless or free fall conditions. At about 1:30 the computer announces "Completing De-Orbit Burn." De-Orbit Burn involves deceleration. This is not free fall, they should be experiencing the deceleration and hence a sense of gravity. The cards should not float. (00:01:30)
Factual error: John Robinson, a United States Marine, is seen wearing an Army combat patch (1st Infantry Division). (00:44:05)
Answer: The Fortuna didn't have an Alien Engine. The cover story was the Fortuna was to explore Alpha Centauri but it was exploring the rift. The rift is what the Alien Engine creates and explains how the Fortuna was able to travel to a distant planet (what you call "galactic travel").
Bishop73