Ares I Thrust Oscillation meetings conclude with encouraging data, changes

[clongton]

Perhaps, for purposes of this forum, it is enough to know that nobody is fooled by this kind of dishonesty. The logical next step is how does one make those Congressional persons aware that this kind of action has occurred?

[robertross]

Perhaps, for purposes of this forum, it is enough to know that nobody is fooled by this kind of dishonesty. The logical next step is how does one make those Congressional persons aware that this kind of action has occurred?

Picket signs and protests on the Hill?
(of course, I wouldn't be able to make it)

At the risk of pulling this thread OT, I'll stop there.

[kyle_baron]

  The resonant frequency of the SRB "pipe organ" is in the 9-to-12 Hz range.  The Ares-1 super light weight second stage's first resonant mode on the other hand is around 12 Hz. 

I doubt it.  This is all theoretical speculation, considering that a 2nd stage Ares 1 with it's 4,000 lbs. of polyurathane insulation, hasn't been built or tested yet!  You would need documentation for Ares 1, 2nd stage with the polyurathane insulation, not just the 2nd stage frequencies, in order to prove your point.

[ugordan]

  The resonant frequency of the SRB "pipe organ" is in the 9-to-12 Hz range.  The Ares-1 super light weight second stage's first resonant mode on the other hand is around 12 Hz. 

I doubt it.  This is all theoretical speculation, considering that a 2nd stage Ares 1 with it's 4,000 lbs. of polyurathane insulation, hasn't been built or tested yet! 

What makes you think foam insulation would have any significant effect on the stage resonant frequency? You have not proven anything with the above remark, either. The point is a tuna can solid stack behaves vastly differently than a lightweight shell filled with low density propellant.

[clongton]

I doubt it.  This is all theoretical speculation, considering that a 2nd stage Ares 1 with it's 4,000 lbs. of polyurathane insulation, ...

Polyurathane insulation will not dampen the TO at all.

[kyle_baron]

  The resonant frequency of the SRB "pipe organ" is in the 9-to-12 Hz range.  The Ares-1 super light weight second stage's first resonant mode on the other hand is around 12 Hz. 

I doubt it.  This is all theoretical speculation, considering that a 2nd stage Ares 1 with it's 4,000 lbs. of polyurathane insulation, hasn't been built or tested yet! 

What makes you think foam insulation would have any significant effect on the stage resonant frequency?

The analogy that I had made previously, with the cymbals of a drum set.  I'll agree that a final analysis would require a full scale mock-up to be tested.

[kyle_baron]

I doubt it.  This is all theoretical speculation, considering that a 2nd stage Ares 1 with it's 4,000 lbs. of polyurathane insulation, ...

Polyurathane insulation will not dampen the TO at all.

Sure it will.  It will dampen the resonance, that leads to T.O.

[ugordan]

I doubt it.  This is all theoretical speculation, considering that a 2nd stage Ares 1 with it's 4,000 lbs. of polyurathane insulation, ...

Polyurathane insulation will not dampen the TO at all.

Sure it will.  It will dampen the resonance, that leads to T.O.

As you yourself said, show us the documentation that proves it.

[kyle_baron]

The Ares-1X's 1/2" thick plate steel skinned second stage had a first resonant frequency that was over 50 Hz, so one would not expect much vibrational coupling between these two elements.

This is interesting.  Why would Ares-1X 2nd stage, with its 1/2" plate steel be 50hz, when the 1st stage SRB, is also 1/2" steel, and vibrates at 12hz?

IIRC, someone had mentioned previously, that the carbon fiber interstage would increase the frequency, because it was stiffer.  It would appear, that he proved his point.

[Antares]

The logical next step is how does one make those Congressional persons aware that this kind of action has occurred?

Well, we know one of the key staffers reads this forum.

[JohnFornaro]

What keeps the polyurethane insulation from vibrating off ?

[bad_astra]

Perhaps, for purposes of this forum, it is enough to know that nobody is fooled by this kind of dishonesty. The logical next step is how does one make those Congressional persons aware that this kind of action has occurred?

Picket signs and protests on the Hill?
(of course, I wouldn't be able to make it)

At the risk of pulling this thread OT, I'll stop there.

Perhaps I'm the only one uncomfortable with non-nationals advocating citizens picketing Congress.

But I am.

[kyle_baron]

What keeps the polyurethane insulation from vibrating off ?

The short answer is sitting on the launch pad.  The long answer, is some SMALL amount of insulation will always come off, due to the liquid air that freezes between the tank and the insulation, along with the vibration of lift off.

[kraisee]

Perhaps I'm the only one uncomfortable with non-nationals advocating citizens picketing Congress.

But I am.

There are some precedents which indicate that help from foreigners can be very beneficial.   A few notable ones:-

Winston Churchill called for, and obtained, support from America to join the war in Europe -- even before Pearl Harbour was attacked.

Werner von Braun spent a whole decade of his time in American building US ballistic missiles for the defense of this country before he was finally naturalized.

Many of von Braun's colleagues didn't get naturalized until much later -- some were well into Apollo by the time they became American.


My point is:   Each case is always different and I would suggest not tarring all with a single brush without due consideration.

As long as the person is well-informed and well-intentioned, their opinions ought to be welcomed, not shunned.

If picket signs are needed (I simply don't know in this case, so I'll abstain from comment), and the average Joe Public isn't aware -- or worse-still, is too apathetic -- a call to action from anywhere which gets something started is not a "bad thing".

I think it would be a mistake to simply ignore all such things just because the voice comes from elsewhere.

Each situation should really be evaluated on its particular merits, and the merits of the person in question.

In this situation, I would suggest that Robert has regularly demonstrated himself to have a sound head on his shoulders, from his previous comments on this forum.   That should warrant some consideration for his ideas, instead of simple blind dismissal simply because he comes from somewhere else.

You never know:   This could be one of those "Never look a gift-horse in the Mouth" situations.

Just MHO.   YMMV.

Ross.

[robertross]

Each situation should really be evaluated on its particular merits, and the merits of the person in question.

In this situation, I would suggest that Robert has regularly demonstrated himself to have a sound head on his shoulders, from his previous comments on this forum.   That should warrant some consideration for his ideas, instead of simple blind dismissal simply because he comes from somewhere else.

You never know:   This could be one of those "Never look a gift-horse in the Mouth" situations.

Just MHO.   YMMV.

Ross.

Thanks for those kind words Ross.

And I would say that if it was a choice of *Direct or nothing, I would be dressed in a bright orange rocket suit with placard in hand saying 'GO DIRECT'.  LMAO.

* (or maybe shuttle extension) 



Getting too far OT now...sorry mods

[Ben the Space Brit]

Perhaps I'm the only one uncomfortable with non-nationals advocating citizens picketing Congress.

At the risk of a thread derailment... why? They do say that you can't see the forest for the trees.  So, a different viewpoint for a slight remove might even be the clearer understanding of the situation!

I seem to remember that 'failure to redress grievances' is, at least in part, what started this whole thing off anyway.  You guys fought a war for this stuff...! Might as well use it!

[MP99]

The Ares-1X's 1/2" thick plate steel skinned second stage had a first resonant frequency that was over 50 Hz, so one would not expect much vibrational coupling between these two elements.

This is interesting.  Why would Ares-1X 2nd stage, with its 1/2" plate steel be 50hz, when the 1st stage SRB, is also 1/2" steel, and vibrates at 12hz?

IIRC, someone had mentioned previously, that the carbon fiber interstage would increase the frequency, because it was stiffer.  It would appear, that he proved his point.

The resonant frequency of the SRB is not from the plate steel casing, it is from acoustic effects in the cavity at the SRB's core. The SRB's case must presumably have a different resonant frequency in order not to rip itself apart on every Shuttle flight.

From what I understand of damping panels used for domestic acoustics (ie music) foam on the upper stage tanks will do exactly nothing to vibrations within several octaves of 12Hz.

cheers, Martin

[William Barton]

Perhaps I'm the only one uncomfortable with non-nationals advocating citizens picketing Congress.

At the risk of a thread derailment... why? They do say that you can't see the forest for the trees.  So, a different viewpoint for a slight remove might even be the clearer understanding of the situation!

I seem to remember that 'failure to redress grievances' is, at least in part, what started this whole thing off anyway.  You guys fought a war for this stuff...! Might as well use it!

Anyway, those of us not "foreign nationals" could just as well advocate citizens of reasonably democratic states also picket their own parliaments, diets, bundestags, etc.

[sdsds]

It's called dynamic resonant coupling between any two driven distributed bodies that have structure resonant frequencies that are within an octave frequency of each other.  The resonant frequency of the SRB "pipe organ" is in the 9-to-12 Hz range.  The Ares-1X's 1/2" thick plate steel skinned second stage had a first resonant frequency that was over 50 Hz, so one would not expect much vibrational coupling between these two elements.  The Ares-1 super light weight second stage's first resonant mode on the other hand is around 12 Hz.  I'll let you draw your own conclusions as to whether the Ares-1X provided any worthwhile date in regards to how the real Ares-1 second stage will react when driven at 10-to-12 Hz, other than to say I hope that LOX damper system works really, really well....

Paraphrasing Star Trek regarding the Ares-1X upper stage, "Dammit Jim I'm an upper stage mass simulator, not an upper stage dynamics simulator!"

That's why the Ares 1 team needs to be given the time to fly the Ares-1Y mission with a five segment SRB and a realistic upper stage.  Even if J-2X isn't ready to go, Ares-1Y thus defined gets a realistic first stage burn with realistic upper stage dynamics, a realistic stage separation event, and could provide a realistic high-altitude abort test as well.  It's a winner of an idea that deserves funding.  But there's no need to rush if NASA temporarily decouples Orion from Ares-I by using the proven Delta IV-H launch system as the interim gap-filler.

[Star-Drive]

The Ares-1X's 1/2" thick plate steel skinned second stage had a first resonant frequency that was over 50 Hz, so one would not expect much vibrational coupling between these two elements.

This is interesting.  Why would Ares-1X 2nd stage, with its 1/2" plate steel be 50hz, when the 1st stage SRB, is also 1/2" steel, and vibrates at 12hz?

IIRC, someone had mentioned previously, that the carbon fiber interstage would increase the frequency, because it was stiffer.  It would appear, that he proved his point.

:Why would Ares-1X 2nd stage, with its 1/2" plate steel be 50hz, when the 1st stage SRB, is also 1/2" steel, and vibrates at 12hz?"

Because of the difference in the fully fueled mass of the SRB (~590,000 kg) verses the unfueled mass of the Ares-1X second stage mass simulator, which is around 190,000 kg, plus the internal structural bracing found in the Ares-1X second stage that is not found in the Shuttle SRBs.  These structures are nothing more or less than spring/damper systems tied to a supporting structure with a certian stiffness tied to a vibrational forcing generator called a rocket.  So once you know the stage's strucure stiffness, mass, bending modes and force function, the structural resonant frequencies fall out naturally for each element in the system.