I get moton sickness very easily on alot of rides (Star Tours) so I took 2 Bonine 30 min before I went on Mission Space and I was just fine. Make sure you listen to what they tell you also, like don't close your eyes and don't look to the right or left. My DH got queasy because he looked over at our DD.
I took a Dramamine an hour before I rode it and I was ok. The second time I rode it however I started to feel a little sick. I guess once was enough for me. But like a previous poster said, everyone is different.