WARNING: SPOILERS FOLLOW!!
The movie starts out with what you expected in the trailer – Sandra Bullock gets separated after some debris from crashed satellites goes by like bullets and then she is free floating/spiraling through space, terrified. I thought the whole movie was going to be about that but it wasn’t at all! George Clooney rescues her using his jet pack and they head back to their shuttle together, shaken up but totally fine.
What the previews didn’t show is that the real movie really starts after she gets rescued! When they get back to the shuttle, it’s been totally destroyed by the projectiles – killing everyone in it and destroying the escape pod too. Sandra and George decide to use his jet pack to try to get to the nearby International Space Station in under 90 minutes before the debris should pass them again.