Good Read Spacecraft Launch Vibration

Pennywise or Mc Donald? Perhaps a jester?

That's Pogo ...click on him

Is that a dastardly clown cookie? Why I believe it is! Thank you not for the dastardly clown cookie.

Is Google not available in that part of the world?

Yes, there is. Just fishing down here. Someone might be into it, who knows.

They have to bang two coconuts together to activate Google over there.

Rocket Vibration

Good Vibrations

I appreciate it Lyn, thanks.

Long ago I worked in a environmental test lab. One important lesson I learned was that most prime movers respond to vibration as a function of their speed. For those applications we often did our vibration testing using a swept sine wave. Not true with rocket motors. They generate white noise, which essentially means the superposition of many frequencies. This means that two loads that would normally respond separately under swept vibration may respond simultaneously under white noise conditions and cause substantial damage. Rockets change everything.

White noise vibration yields sum, difference and the two originals, just like voltage modulation does and does so simultaneously.

Sine sweeps find the individual resonances, and white nose vibration recreates their real-world interactions.

Are you saying that vibrational mechanical modes (including pogo) in a rocket system can exchange energy freely and rapidly? I think that almost has to be true.

A productive way to think about this is to consider two cantilevers with different resonant frequencies mounted on a support at right angle to each other. When the support is driven by a swept sine wave, one cantilever will resonate at its natural frequency. As the frequency is changed, that cantilever's oscillations will be reduced and the second cantilever may become resonant. So, during this sweep, each cantilever goes into, and out of resonance, just once, and neither cantilever interferes with the other. Under white noise excitation however, both cantilevers can become resonant it the same time and cause significant damage.