 Why does Mary ask Phil to go to the rocket as soon as they can see it?
Phil Conover pulled the zipper of his flight suit up the front of his long, thin body and came into the living room. Yes, I'm sure you did," she said, finishing the ritual; but her voice broke, and she turned her head away. If anything could go wrong, they wouldn't be sending me; you know that. "Mary, you know I can't back out now. Nothing would ever be right with me again if I didn't go. "Phil, if you go, I won't be here when you get back—if you get back. I won't be here because I won't be the wife of a space pilot for the rest of my life.
 She did not want to prolong the painful goodbye.
 She was not allowed to stay there, as a civilian, so she had to leave.  She did not want him to be late for his very important mission.  She needed to drop them off so she could leave.  She did not want to prolong the painful goodbye.