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Danny Harvey

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Reply with quote  #31 
"...to dampen the resonance."

They would do it to DAMP the resonance, not dampen it. To dampen it would be to make it wet.

I don't normally call out that error but if you're putting it into a book...

arrow1head

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Reply with quote  #32 

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In space it is funny, there are almost no flow if you don't count the solar wind? So what can vibrate and create vibration in hull or anywhere?

I've learned that a process called "neutron embrittlement" could change the molecular integrity of the hull of a ship, thereby potentially causing resonance problems. Space is full of sub-atomic particles, sometimes only one or two particles per cubic meter, but traveling at speed, those particles would impact the hull over time. But yes…I think ultimately the resonance in the ship would have to do with itself and its internal functioning, which could get out of hand in a vast, complicated ship with a lot of powerful energy systems inside of it. I mean, that seems to be what I'm hearing from you experts.



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So it would be an option on a hull vibration problem, internal or external. Not a pendulum of course, where the 'centering force' comes from gravity, but rather a cantilever beam which wouldn't care about gravity. 

This is damn interesting!


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They would do it to DAMP the resonance, not dampen it. To dampen it would be to make it wet.

You are right sir….an amateur mistake! The funny thing is, I read about somebody else committing this blunder before I myself did.




OLi

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Reply with quote  #33 
If you dampen the resonance it will freeze to ice and that will damp it, maybe? :-). At some speed like Warp 5 maybe you will maybe have a flow of some sort.......?
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Curran919

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Reply with quote  #34 
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They would do it to DAMP the resonance, not dampen it. To dampen it would be to make it wet.


Hold on... to dampen also means "make less strong or intense", or what I normally refer to as attenuating in terms of vibration. I imagine this is probably related to adding damping to something. It would not explicitly mean to add damping, where to damp would be appropriate.

However, I would also argue that you can not damp a resonance. One of my personal pet peaves is when people refer to a natural frequency as a resonance or resonance frequency. It is not. A resonance requires both a discrete/narrowband excitation that is in coincidence with a natural frequency. You can damp a natural frequency, but you can not damp a resonance. Actually, I would argue that can dampen a resonance (or attenuate a resonance) through the act of detuning that resonance.

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I've learned that a process called "neutron embrittlement" could change the molecular integrity of the hull of a ship...

I would look into something called hydrogen embrittlement. This is very common and can affect primarily titaniums and high-strength steels, but also many other exotic sounding metals. This may be interesting if the ship has to pass through a dense nebula, which of course is composed largely of molecular hydrogen and hydrogen gas.

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This is damn interesting!


If you want to look into passive dynamic absorbers (or dynamic vibration absorber or sometimes tuned mass damper), its may get pretty complicated. This video is the most 'watchable' for non-engineers that i know of, but it also focuses on a pendulum damper (as most buildings to), which wouldn't be useful in space 😋

Danny Harvey

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Reply with quote  #35 
I suppose that dampen has come to be accepted usage just as "normalcy" was only with less notoriety.
Curran919

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Reply with quote  #36 
Did you decide on a failure mode, OP?
arrow1head

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Reply with quote  #37 
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IMHO, if you want to explain, the detuning of resonance by changing the natural frequency is a good one that readers can understand and you can have creative solutions. However, if you want to just sound sciency, I am very partial to MarkL's suggestion of expanding on the Triboelectric effect as a real problem we can have, but still a word that sounds cool that most readers probably won't be familiar with and so will avoid the 'bad sci-fi jargon' trope.


This thread has generated really good and specific ideas. I'm sure the solution is here, perhaps in a combination of these things. 

Let's say it's a very large craft with a few thousand people living in it. Perhaps they would have a specific protocol for addressing a vibrational problem like this. Perhaps they would have dynamic vibration absorbers that could even be attached to the INSIDE of the hull, in order to "pull" some of the offending vibration into it.

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We use a lot of passive dynamic absorbers on our pumps and in the past, on train bogeys. So it would be an option on a hull vibration problem, internal or external. Not a pendulum of course, where the 'centering force' comes from gravity, but rather a cantilever beam which wouldn't care about gravity. This concept may be a bit harder to explain to readers, and I think the fact that it is called an absorber also tends to really confuse people since that's not really what it does.


In a scenario like this, I wonder how would you determine WHERE on the hull you should install this vibrational patch, or cantilever beam? Perhaps analytics would tell you that attaching an absorber at 'x' location would cure the problem?

Also, any opinions on whether navigational gyroscopes could cause vibration problems in a spacecraft?


p.s. Curran, I don't know WHY, but I somehow missed one of your posts from earlier. Thanks for the useful ideas, and I like that concept, how different environmental conditions would lead to different physiological/sociological realities. 
OLi

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Reply with quote  #38 
I doubt you would have gyros with rotating parts anymore they surely have a finite operational time. If you would have that anyway they are balanced as good as you possibly can to get reasonable operational time.
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John from PA

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Reply with quote  #39 
Quote:
Originally Posted by Danny Harvey
"...to dampen the resonance."

They would do it to DAMP the resonance, not dampen it. To dampen it would be to make it wet.

I don't normally call out that error but if you're putting it into a book...



Ah yes...Don Bently used to go ballistic if someone used the improper term!
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Reply with quote  #40 
Brings up imbalance and unbalance.... mmm...

Vibe-Rater

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Reply with quote  #41 
I'm heading down the coast for some refinery work tomorrow. Wish me luck. I do enjoy the data collection thing still. Unfortunately I can't take photos b/c not allowed to carry camera. I wish I could. would be nice to have a shot. rgds

arrow1head

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Reply with quote  #42 
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I doubt you would have gyros with rotating parts anymore they surely have a finite operational time.


I see. What other kind of gyroscopes are there, besides those with rotating parts?

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If you would have that anyway they are balanced as good as you possibly can to get reasonable operational time.


I don't understand.
Curran919

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Reply with quote  #43 
Quote:
Originally Posted by arrow1head

Let's say it's a very large craft with a few thousand people living in it. Perhaps they would have a specific protocol for addressing a vibrational problem like this. Perhaps they would have dynamic vibration absorbers that could even be attached to the INSIDE of the hull, in order to "pull" some of the offending vibration into it.


Vibration absorbers must be quite massive in order to be effective. I don't think that is something they would just have a 'spare' of. They also have to be tuned differently to different situations. Generally, the spaceship can be designed from the beginning to resist any foreseen vibration. It is the unforeseen vibration that you would use an absorber on, because they are quite ad-hoc solutions.

Quote:
Originally Posted by arrow1head

In a scenario like this, I wonder how would you determine WHERE on the hull you should install this vibrational patch, or cantilever beam? Perhaps analytics would tell you that attaching an absorber at 'x' location would cure the problem?


Quite simply, wherever the highest amplitude of vibration is (with obvious practical caveats). Then the absorber has to be aligned in the proper direction, such that its vibration vector matches the vibration vector of its point of attachment to the object.

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Originally Posted by arrow1head

Also, any opinions on whether navigational gyroscopes could cause vibration problems in a spacecraft?


Anything with a rotating can cause vibration. However, gyroscopes are the most highly balanced tools of all. That's because a small amount of unbalance/imbalance, even leading to a tiny amount of vibration, can negate the sensitivity of the device. I don't know how sensitive the gyroscopes would be to external vibration, probably not very? I also don't know of navigation gyroscopes that don't have a flywheel...
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