I hated this movie I watched with my son. I would have walked out of I had been there myself. It lost all credibility when mercenaries used shoulder launched missiles to shoot down shuttles in near geosynchronous orbit.
It was further compounded by making incredible machinations in order to irradiate Matt Damon with a fatal dose of radiation calculated to incapacitate him in exactly 24 hours.
No science, all fiction. At the end of the movie my son remarked: "Well, I guess Jody Foster really stuck her neck out on this one!" Really disappointing considering this director's debut movie, District 9, I believe. I would rate this zero or negative stars if I could.