The costume designer claims that the blue cloth outfit we see first, is just a covering and the orange-piping suit is what's underneath. Supposedly as the film wears on, people realize they don't need to wear the entire suit because of the earth-normal atmosphere in the pyramids. Also there's a huge rush to put on spacesuits near the end of the film so they don't have time to mess with the whole thing (Vickers puts her suit on in under 30 seconds!)
I don't buy it tho, I think the orange-piping-wetsuit thing was concocted to better show off Charlize and Noomi's assets.
Note for example how none of the men wear the orange piping suit. :rolleyes
Also they have a whole separate upper armor for the orange piping suit which conveniently exposes more of the actors' chest.
Anybody who doubts that Ridley would want to show off the bodies of his female actors need only watch the last 10 minutes of ALIEN.
Plus also there's a lot of strenuous running in the end of the film, which is facilitated (conveniently) by the stretchier orange-piped suits, which have no knee or shin armor.
Another suit oddity, is that at one point Shaw (wearing the orange piped suit) is lying on the ground outdoors.. but she has no
gloves on. So clearly the air pressure is reasonably near normal, and there are no corrosives... apparently the only problem with the air is the high CO2 content! :eek
k