Board Thread:Warhammer 40k General Discussion/@comment-25222488-20151025234507/@comment-18016240-20151123025017

Gellar fields are essentially shields meant to keep the Warp from getting into a ship as it goes through it. If it's too weak or malfunctions (considering that a lot of ships are centuries, if not millenia old this happens often) then it's party time.

I think generation ships are ships wherein the passengers' descendants are supposed to reach their destination after their parents die, since the voyage may take too long for one life time.