Why Heavier subsystem; Lower Grms 2

[sarclee]

Hi, just to check the Grms for electronic equipment. Why is it smaller component (30gram) can take up to 15Grms,heavier component (400 gram) can only take 8Grms?

 

[IRstuff]

Yeah, we had those too, but the resonance came from something after the isolators, so every unit shipped with a popsicle stick.

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[nicomedian]

The levels given in SMC is acceptance levels. To achieve the qualification levels, you need to add 6 dB, which is 4 times the values you have it in the figure.

 

[sarclee]

I think the high peak psd at the interested part might be excited by the global mode resonance.

The amplification factor up to 20...

 

[rb1957]

"I think the extreme peak psd of the interested part might be excited by the global mode resonant."

? do you mean your payload structure is resonating (under the input spectrum) ? yes, sounds about right.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[sarclee]

Yes... something like the picture below. The cross marked plate is resonated by the base in vertical direction. I tried to separate them but it is very difficult...

 

[rb1957]

yeah, a flat web will do that. How big is the web ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[sarclee]

About 40x40cm.

It is a global mode that the excitation in vertical direction... Not sure can de-couple it... Hmmm

 

[WKTaylor]

When are the reaction wheels 'spun-up'? I assume prior to launch so that they are 'stable' and any anomalies could halt the launch sequence.

Perhaps HRA coiled wire vibration Isolators tuned to Your purpose... solely intended for reducing G-Rms on the reaction wheels during launch?

Is there any way to 'cage' the RW and then start-it-up late into the launch sequence, reliably?


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[rb1957]

I think you need "panel breakers", maybe divide into 4 panels.

If the panel is thin sheet, maybe a composite sandwich panel (would stiffen the panel without adding much weight) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.