A singer brings the wine glass to his lips. Unleashing a sustained note directly into the side of the glass, the goblet’s walls begin shaking. If the tone is just right, it can trigger vibrations in the brittle material that eventually causes the glass to shatter.
The phenomenon is called resonance, when a transmitted sound wave’s frequency matches the natural frequency of a receiving material and causes it to oscillate.
Now picture a rocket lighting up. It turns out that the same acoustic phenomenon can happen inside the liquid-fueled engine as combustion occurs. The results, as one might imagine, are not good.
“The flame is the singer that can excite a tone, and combustion can couple with the acoustics of the rocket chamber,” says John Bennewitz, a University of Alabama in Huntsville (UAH) graduate student and Von Braun Propulsion Fellow. “The tone can eventually rip the whole engine apart.”
In a former Boeing 747 assembly plant within shouting distance of the Los Angeles International Airport, Space Exploration Technologies, or SpaceX, is building a revolution.
Since the dawn of space flight, the industry has been dominated by large firms essentially writing their own paychecks. Only the biggest communications companies and national governments could afford launches costing hundreds of millions of dollars. That’s changing now, in large part because of SpaceX.