Reinterpretation of Sunshine
After several viewings of this film, I think I got together a complete and hopefully coherent interpretation of the film, which is not so obvious, since the plot pretends to be of a straight-forward science fiction/horror movie. But there's much more to it, it's actually a social drama.
So here's my interpretation: Given that the crew are a bunch of scapegraces, they are not sent to save the sun from whatever the sun's pretended to be doing. Instead, the mission is to send the biggest idiots of humanity in outer space and to be burnt by the sun. An undertaking with a complete success, in both cases.