Key and Horn on Keeping a Rocket’s Internal Form Sound

“Earlier, we were looking at chip patterns,” Key said, pausing beside the simple cross-section. “Here the question changes. A solid rocket motor has an internal form, and that form has to remain sound through the stresses of service.”

Horn studied the uninterrupted shape. “So it isn’t enough for the interior to look right at the start. If it loses its integrity, the original shape no longer tells the whole story.”

“Exactly,” said Key. “NASA’s June 1973 monograph treats structural integrity of the solid-propellant grain as its own engineering concern. Its foreword calls the document guidance, not an automatic set of project requirements.”

Horn nodded. “A useful distinction: understand what must be protected before mistaking a drawing for a promise.”