The loss of solar heating has caused the Earth's atmosphere to freeze into thick layers of "snow". The boy's father had worked with a group of other scientists to construct a large shelter, but the earthquakes accompanying the disaster had destroyed it and killed the others. He managed to construct a smaller, makeshift shelter called the "Nest" for his family, where they maintain a breathable atmosphere by periodically retrieving pails of frozen oxygen to thaw over a fire.
It starts with cadet Roger, urm, nicking a study spool for use in a competitive exam -- but that leads all of our cadets into a fight, and when they're caught at that, a trial. In the midst of the trial they get assigned to duty on a Top Secret Projectile Project, and things go wrong there in ways at once related and impossible to connect. Someone is causing real menace to roost in the cadets' lives, and the worst is still ahead...
The space ships were miracles of power and precision; the men who manned them, rich in endurance and courage. Every detail had been checked and double checked; every detail except--
Captain Brandon was a pioneer. He explored the far reaches of space and reported back on how things were out there. So it was pretty disquieting to find out that the "far reaches of space" knew more about what went on at home than he did.