Auk XII was the first rocket the boys launched that was loaded with the fuel they called "rocket candy." It was built to the same design as its predecessors, and would be the first rocket to be launched with an electrical-ignition system. When Sonny touched a wire to an old car battery the boys had rigged up, the rocket rose high into the air and then faltered and began to fall. When it landed on the slack, the boys ran to get it, and discovered that the rocket's nozzle had blown out. Further examination showed that the weld was still intact; the center of the nozzle had simply been eaten away, causing the rocket to lose its thrust.

A theodolite was a crude instrument invented by Quentin to measure the highest altitude of the rocket. It was made from a broomstick with an upside-down protractore attached on one end and a wooden straightedge on the opposing side that rotated around a nail. By jamming the stick in the slack and squinting along the straightedge at the rising rocket, then noting the angle the ruler made with the protractor at the rocket's highest point, Quentin could, by using trigonometry, calculate the altitude of the rocket's flight. In this manner, Quentin estimated that Auk XII reached a height of seven hundred and sixty feet.

Thanks to posted notices and a series of articles written about the Rocket Boys, a group of about fifty people were on hand for the the launching of Auk XII. The audience included several members of the high school football team, who were hostile and derisive, angry at having the attention of the community focused on the Rocket Boys instead of on themselves. The rest of the spectators, however, were excited and highly supportive. Some of them even began to cheer for the Rocket Boys, just as they would at an athletic event (Chapter 11).