The Internet seems to be in disagreement: some reviewers of Frederik Pohl's Gateway blame Rob for pushing the button and killing the other nine people. Others say it was an accident (or should I call that luck?). And Rob's doing the same when recalling the events of that trip. One minute he is talking about the dread of his sacrifice, the other he's confusingly blabbering about saving himself and leaving his crewmates stuck in time. You could say - nah, it's just survivor's guilt talking. But then again, Rob was depicted as a rather flawed protagonist, not the hero kind.
Did Frederik Pohl actually leave that question unanswered? Or where there indications in the book that would make one of the conclusions more likely?