I rode both missons last year for the first time. I was worried about riding the orange misson and my boyfriend convinced me to at least try the green misson. He really loves Misson Space and was able to help calm my nerves. In fact he convinces me to ride a ton of rides. He's good at getting me on roller coasters. lol
Anyway Green Misson is least intense. It does not spin, but the vechical you are in does move. It rocks you around kind like Star Tours. You do feel some g-force when "lifting off", but it's not so bad. I rode this version twice. The second time my boyfriend and my mom convince my mom to ride it. She is not a thrill seeker at all! And she loved it!
As for the Orange Misson, yes it is more intense. However despite the spinning I never felt it? I mean I knew were moving, but it felt like I was riding The Scambler (the typical ride you see at festivals or other amusment parks. It spins you around in a circle). I did feel the g-forces. A bit more intense than Green, but not as bad as thought it would be. My tip for anyone who wants to ride, but is afarid of getting sick. This tip can work for green too. Keep your mind busy! Don't focus on the monitor 100%. Look at the control panel and pick a nob, switch, or a button to foucs on, when you feel uncomfortable. Seeing an object on the panel can trick your brain into thinking you are stationary. This isn't a 100% cure to motion sickness. Everyone has a different levels, but I'm sure it can help for some people.
I really loved Mission Space. Whenever I go back to WDW, I will ride it again!