Patchy yet captivating first novel about familial fractures- -with an unusual conceit. The conceit is that heroine Helen Urie, 20, is separated from her mother not only by emotional distance but by an unprecedented physical gap--because Canadian astronaut Barbara Urie is orbiting the Earth as half of a male-female team aiming to set a record for in-space habitation. The story opens with Helen and her brother, Paul, watching from a deliberate distance as Barbara rockets into orbit--``and in that instant, everything...changed,'' including the validity of perception: That night, the two gaze in disbelief as a TV replay shows their doubles at the launch's viewing stand--``a backup family'' supplied by a media-minded NASA for the no-show siblings who chose to watch from afar. Also backed-up is their dad, David, whom they haven't seen since he lit out years before to provide earthquake relief when the ``Big One'' hit L.A. (one of several ecodisasters that backdrop the plot). Author Bush pushes the sense of dislocation by alternating first- and third-person narration as Helen returns to hometown Toronto and takes an anonymous job waitressing. She also joins an animal-rights group, which leads to her unmasking when she's arrested for civil disobedience. But that act of defiance begins a transformative dialogue between Helen and Barbara (via telephone and closed- circuit TV), and--after Barbara is forced to make a fateful decision about staying in orbit--the entire family has a chance to start anew.... A slightly surreal collage of often remarkable images and sensitively drawn characters that doesn't quite cohere--but that Bush is a talent to watch is without doubt.