The nozzle directs a hot river of gas that reaches the speed of sound.

Homer Hickman and his friends were interested in getting a rocket to work, but it was no easy task for the children of coal miners.  One of their problems was a lack of advanced math, and another was a lack of materials.

Miss Riley had enough faith in the boys to convince them that science was the ticket out of the coal mines.  She provided them with a book that showed them step by step how to build a rocket successfully.  Even though the math was difficult, the boys managed to make it work and by the time they were building AUK XXIII they had been working on the process for two years.

Once they were able to determine how to make the rocket, they realized that the key to the successful launch of their mini-rocket was the nozzle. 

But if the gas river reached the speed of sound at the throat (“The key to nozzle design, Sonny!”), then the gas flow in the divergent section would go supersonic, a very good thing. (Ch. 22)

In order to successfully launch the rocket, the rocket fuel must reach the speed of sound at the throat.  Calculations Homer did resulted in an estimated speed of 545.45 miles per hour.

In this inspirational true story, we learn that anything is possible if you want it enough.  Homer and his friends, and the teacher Miss Riley, kept trying even after repeated failure.  With hope and hard work, anything is possible.