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Spacecraft Resonance
- Thread starter sarclee
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- #3
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?
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?
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'...
“Anything 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]
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'...
“Anything 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]
SWComposites
Aerospace
If launch vibrations result in resonance of local modes, you very well may have a problem.
GregLocock
Automotive
For Space Shuttle payloads they did a lot of modal and fatigue analysis and aeroacoustic excitation (blast it with loud noise?) in the stored configuration.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
- Thread starter
- #7
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]
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]
jackaustin
Materials
@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.
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GregLocock
Automotive
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
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
New here? Try reading these, they might help FAQ731-376
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
New here? Try reading these, they might help FAQ731-376
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