While Rockwell finishes out his three-year stint up on that space station, he’ll have some form of company in Kevin Spacey, utilizing the irony of his name in a better way than K-PAX. All we know so far (courtesy of io9) is that Spacey will provide his voice to a robot of some kind — whether it’s a humanoid mech or the presence of the high-tech facility itself remains to be seen heard. Either way, Spacey’s vocals could be either soothing or a contributing factor to Sam’s space madness.
It would seem there could also be more Sam than just Sam, but you can visit io9 to get the skinny on that. The movie is directed by Duncan Jones (son of David Bowie).