Why SpaceX's launch for NASA is such a big deal for Elon Musk's rocket company and the US as a whole

· SpaceX is set to launch NASA astronauts to the International Space Station for the first time on Saturday afternoon.
· Poor weather conditions forced NASA and SpaceX to scrap their first liftoff attempt on Wednesday.
· A successful launch would mark the first time an American-made spacecraft has launched humans from US...