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.”
Undersea vehicles might soon be getting an agility and efficiency upgrade thanks to a few tips from marine animals.
In two different announcements last week, researchers said they are decoding the mechanics of how stingrays and penguins swim. The result could be better propulsion systems for unmanned underwater vehicles.
There are nearly two million people who are missing one or more limbs in the United States alone. Around the world, a number of research groups are working to advance robotic prostheses to restore a sense of normality to the lives of amputees.
Michael Goldfarb, a Vanderbilt University mechanical engineering professor, is at the cutting edge of these advancements. His lab is making robotic limbs more human.