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Spacecraft Resonance

Spacecraft Resonance

Spacecraft Resonance

(OP)
Hi, should we consider the local mode resonance at solar panel for spacecraft in modal analysis to meet the fundamental resonance requirement from launcher?

RE: Spacecraft Resonance

Yes.

RE: Spacecraft Resonance

(OP)
Thanks for your reply SWComposites.

Why do we look at local mode instead of global mode? It could be not critical mode, right?

For example, if the antenna is modeled in the modal FEM, antenna would be the first mode and lowest frequency which could be much lower than the fundamental resonance requirement. Should we look for global mode resonance instead?

RE: Spacecraft Resonance

sl...

We cannot resolve this issue for You with a stock-photo and a few simplified questions... but with reference to 'general experience'... back-to-you, thus.

As I recall, one of the significant factors affecting the Hubble Space Telescope on commissioning... in addition to the primary mirror optical aberration... was that the solar panels had long-term undampened vibrations as the observatory shifted aim-points and it transitioned thru day-night-day-night-etc thermal cycles.

The first HST servicing mission installed the COSTAR for the optics correction; and removed and replaced both solar panels with new massively-improved ones [among a few other important modifications... and maybe something regarding the high-gain/tracking antenna?].

LOTS of engineering lessons have been learned the hard way... and always to extremes in spaceflight. In accordance with the most popular version of 'Murphy's Law'...

ÔÇťAnything that can go wrong, will go wrong. ... and Murphy was an optimist.

Or... if You insist on not testing/analyzing the antennas and panels... and simply assume your micro/small-Satellite will be immune-to, or otherwise not be significantly affected by vibrations... then I shall quote Clint Eastwood from the movie 'Dirty Harry' [the actual words]...

"You've got to ask yourself one question. 'Do I feel lucky?' Well, do you, punk?"

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Spacecraft Resonance

If launch vibrations result in resonance of local modes, you very well may have a problem.

RE: Spacecraft Resonance

(OP)
Appreciate everyone!

RE: Spacecraft Resonance

S... one fine point...

IF You are designing a new small-sat from scratch, then the road is a lot harder... as opposed-to if You are re-using most of a 'stock/proven' small-sat design [body/chassis, antennas, solar panels, batteries, etc]... and incorporating only small changes.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Spacecraft Resonance

@sarclee Whenever I want to put a satellite relay network into orbit I like to use resonant orbits to make sure the satellites are evenly spaced but to find the resonant orbit I've been doing it by trial and error rather than calculating it. I'd get 2 ships, one in the target orbit and another with a matching apoapsis and low periapsis. I'd time warp and adjust the periapsis depending on whether it needs to speed up or slow down to match the ship in the circular orbit. I'd keep going like that until they are in orbital resonance.

RE: Spacecraft Resonance

(OP)
Thanks everyone once again.

We are going to do vibration testing to verify the results after we separate the resonance from other payload resonance.

RE: Spacecraft Resonance

(OP)
Another question... We managed to shift the resonance... Wonder if the payload resonant freq should avoid the resonant frequency of the interface or the satellite system/ global resonant frequency?

RE: Spacecraft Resonance

What you need is a top secret document called a modal alignment chart. The only useful copy of one I can find has been cleverly encoded, if you can break the code you will probably be able to figure it out

https://www.researchgate.net/figure/Figure-A1-Moda...

so what you do is put all your excitation frequencies in, and then put your resonances in. Ideally no two resonances should coincide in frequency (unless you want them to for super top secret reasons) and in my case I wouldn't want a vertical bending mode to align with a vertical excitation, ideally.

Cheers

Greg Locock


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