I love it when a movie captivates you with a very simple story. Stripped down. Get from point a to point b. Everything in this had my attention. If i was to pick flaws, I really would be nitpicking. I guess in such a great movie the flaws were only noticeable because of how rare they were. So I guess ill pick at them, but none of them were even remotely close to ruining the film:

****SPOILERS BELOW
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1) She lost her daughter and obviously was traumatized by it. If she was to go into space she would have failed the psychological test and never would have been permitted to go. I understand that they were banking on that whole angle of her battling her demons and it was important for the drama, but its just one little thing that stood out. No way would she be permitted to go.

2)Her talking to herself and the whole "lets go home" moments were a bit much. Again, probably made to dramatize it a little but was just a little too cliche'

3)the sequence of events was pretty unbelievable and might be a bit of a reach. Yet again its understandable that it all needed to happen to keep you captivated, as it did just that.