Ariane 5 fairing separation induces excessive vibrations - 2020/2021

[hoku]

Does anyone have more (public) info on the "excess vibration" observed during fairing separation in two recent Ariane 5 launches?

https://www.spaceintelreport.com/fairing-separation-issue-has-grounded-ariane-5-since-august-2020-also-affected-ulas-atlas-5/

I tried to check Arianespace's live coverage of recent missions for anything obvious, but it turns out that the fairing separation sequence aired is always the same pre-recorded footage of an earlier launch (as evidenced by the same cloud pattern).

[edkyle99]

"... with similar consequences for the United Launch Alliance Atlas 5, which uses the same fairing technology ..."

  ... and Vulcan of course.

Except there was an Atlas 5 launch on November 13 (AV090/NROL-101), which doesn't line up with the "grounded since August" wording.   AV090 used a Medium height, 5 meter diameter fairing.  This one is, I think, a couple meters shorter than most Ariane 5 ECA fairings.

 - Ed Kyle

[ZachS09]

"... with similar consequences for the United Launch Alliance Atlas 5, which uses the same fairing technology ..."

  ... and Vulcan of course.

Except there was an Atlas 5 launch on November 13 (AV090/NROL-101), which doesn't line up with the "grounded since August" wording.   AV090 used a Medium height, 5 meter diameter fairing.  This one is, I think, a couple meters shorter than most Ariane 5 ECA fairings.

 - Ed Kyle

The regular Atlas V 500 fairings are about 21 meters tall while the Ariane 5 fairings are 17 meters tall.

[Redclaws]

I tried to check Arianespace's live coverage of recent missions for anything obvious, but it turns out that the fairing separation sequence aired is always the same pre-recorded footage of an earlier launch (as evidenced by the same cloud pattern).

Man, I really hate that they do that.  It’s really kind of casually dishonest - just like showing a simulation and pretending it’s actual vehicle telemetry, which they also do.

They’re not under any obligation obviously, but it just feels kind of cheap and slightly insulting to the viewers.

[edkyle99]

"... with similar consequences for the United Launch Alliance Atlas 5, which uses the same fairing technology ..."

  ... and Vulcan of course.

Except there was an Atlas 5 launch on November 13 (AV090/NROL-101), which doesn't line up with the "grounded since August" wording.   AV090 used a Medium height, 5 meter diameter fairing.  This one is, I think, a couple meters shorter than most Ariane 5 ECA fairings.

 - Ed Kyle

The regular Atlas V 500 fairings are about 21 meters tall while the Ariane 5 fairings are 17 meters tall.

I think that the Atlas 5 "Medium" fairing is shorter than the 17 meter long Ariane 5 fairing, but I'm only counting the part above the Centaur that actually surrounds the payload.  The entire thing, which is longer, does separate into two halves though, like one big fairing, including the shroud around Centaur, so there are substantial differences between Atlas and Ariane fairings I suppose.

I wonder about "excessive vibrations".  The separation event usually produces a shock event that is shown on users guides as a range of energy across a range of frequencies.  I suppose the concern beyond the energy of the shock itself is the danger of triggering resonances?  What has changed in the fairing design recently, if anything, that has brought up this concern?

 - Ed Kyle

[zubenelgenubi]

"... with similar consequences for the United Launch Alliance Atlas 5, which uses the same fairing technology ..."

  ... and Vulcan of course.

Except there was an Atlas 5 launch on November 13 (AV090/NROL-101), which doesn't line up with the "grounded since August" wording.   AV090 used a Medium height, 5 meter diameter fairing.  This one is, I think, a couple meters shorter than most Ariane 5 ECA fairings.

 - Ed Kyle

The regular Atlas V 500 fairings are about 21 meters tall while the Ariane 5 fairings are 17 meters tall.

I think that the Atlas 5 "Medium" fairing is shorter than the 17 meter long Ariane 5 fairing, but I'm only counting the part above the Centaur that actually surrounds the payload.  The entire thing, which is longer, does separate into two halves though, like one big fairing, including the shroud around Centaur, so there are substantial differences between Atlas and Ariane fairings I suppose.

I wonder about "excessive vibrations".  The separation event usually produces a shock event that is shown on users guides as a range of energy across a range of frequencies.  I suppose the concern beyond the energy of the shock itself is the danger of triggering resonances?  What has changed in the fairing design recently, if anything, that has brought up this concern?

 - Ed Kyle

Re: upcoming JWST flight: change of PLF design, followed by testing on recent launches--for smoother, more complete de-compression under the PLF before fairing jettison.

[hoku]

"... with similar consequences for the United Launch Alliance Atlas 5, which uses the same fairing technology ..."

  ... and Vulcan of course.

Except there was an Atlas 5 launch on November 13 (AV090/NROL-101), which doesn't line up with the "grounded since August" wording.   AV090 used a Medium height, 5 meter diameter fairing.  This one is, I think, a couple meters shorter than most Ariane 5 ECA fairings.

 - Ed Kyle

The regular Atlas V 500 fairings are about 21 meters tall while the Ariane 5 fairings are 17 meters tall.

I think that the Atlas 5 "Medium" fairing is shorter than the 17 meter long Ariane 5 fairing, but I'm only counting the part above the Centaur that actually surrounds the payload.  The entire thing, which is longer, does separate into two halves though, like one big fairing, including the shroud around Centaur, so there are substantial differences between Atlas and Ariane fairings I suppose.

I wonder about "excessive vibrations".  The separation event usually produces a shock event that is shown on users guides as a range of energy across a range of frequencies.  I suppose the concern beyond the energy of the shock itself is the danger of triggering resonances?  What has changed in the fairing design recently, if anything, that has brought up this concern?

 - Ed Kyle

Re: upcoming JWST flight: change of PLF design, followed by testing on recent launches--for smoother, more complete de-compression under the PLF before fairing jettison.

Thanks for the clarification and for providing the context! I had forgotten about the concerns related to residual air trapped in the folded JWST sunshield, and the resulting modifications to the Ariane 5 fairing vents - see the Jan 27, 2021 JWST update by Eric P. Smith
https://www.nsf.gov/attachments/300822/public/12_James_Webb_Space_Telescope_Update_Eric_Smith.pdf

[FutureSpaceTourist]

https://twitter.com/spacenews_inc/status/1392807819821428736

Ariane 5 hasn’t flown since August 2020, leading to speculation there was an issue with the rocket. Arianespace acknowledges in a statement to SpaceNews that post-flight analyses of two recent launches raised concerns about fairing separation.

https://spacenews.com/ariane-5-issue-could-delay-jwst/

Edit to add:

[…] industry sources familiar with the issue said that, on both the August 2020 launch and the previous Ariane launch in February 2020, the separation of the faring induced vibrations into the payload stack well above acceptable limits. Neither incident damaged any of the payloads, but raised concerns about the effect on future missions, including JWST.

[EnigmaSCADA]

I hope testing is thorough beyond compare and there's no sense of pressure to "wing it". JWST is too precious to risk if everyone is not fully satisfied with this fairing situation. Rightly/wrongly, heads will roll and nasty finger pointing will ensue if something goes wrong, especially if it involves an issue that was known and cause for concern ahead of time.

I find myself more & more in the camp of those that think these one-of-a-kind multi-billion dollar irreplaceable missions that simply can't/won't be replaced/followed-on should something happen is a terrible strategy and not worth the resources. Much better to pair things down a bit and be able to make more than one (eg. Spirit/opportunity & Curiosity/Perseverance) than one super-duper boondoggle that will set you back 10+ years if it fails.

Sent from my Pixel 5 using Tapatalk

[Jim]

I find myself more & more in the camp of those that think these one-of-a-kind multi-billion dollar irreplaceable missions that simply can't/won't be replaced/followed-on should something happen is a terrible strategy and not worth the resources. Much better to pair things down a bit and be able to make more than one (eg. Spirit/opportunity & Curiosity/Perseverance) than one super-duper boondoggle that will set you back 10+ years if it fails.

Not relevant analogy.  Spirit/opportunity was a one off project.  Perseverance was not planned at the time of Curiosity.
Europa Clipper, WFIRST, Cassini etc are all high value spacecraft

[electricdawn]

Doesn't change the outcome, though. At least IMHO. We need to get away from these super expensive one-offs and find ways to do it cheaper with multiple, smaller modules.

[hoku]

Attached is the (full frame) fairing separation clip (stills in the 1st post of this thread), which Arianespace airs at the time of fairing jettison for many of the Ariane 5 launches. It shows the "normal" oscillations of one of the fairing halves ("breathing mode" according to the commentator).

[hektor]

Having to spend money to fix a launcher which is at the end of its operational life, for a single mission, must not be welcome news in Europe. I wonder who is paying. Is it ESA or Ariane ? Is it a change a specs or a case of not meeting the specs.

[hoku]

Having to spend money to fix a launcher which is at the end of its operational life, for a single mission, must not be welcome news in Europe. I wonder who is paying. Is it ESA or Ariane ? Is it a change a specs or a case of not meeting the specs.

There are quite some commonalities between Ariane 5 and 6. For Ariane 6 a new "out-of-autoclave" production method for fairings was implemented. Fairings produced with the new (and cheaper) method were first launched in 2017 on VA238:
https://www.ruag.com/en/news/milestone-space-industry-ruag-made-new-ariane-6-payload-fairing-debut-ariane-5

Thus one could see this more as a continued development towards a (hopefully) better product. Reduced (acoustic) vibrations during launch and reduced oscillations during the fairing jettison event should for example ease environmental requirements on the payload.

P.S.: the attached image shows the location of the 14 vents around the lower section in the interior of a fairing half

[Jim]

Doesn't change the outcome, though. At least IMHO. We need to get away from these super expensive one-offs and find ways to do it cheaper with multiple, smaller modules.

Doesn't work that way

[electricdawn]

It depends on the mission, I think. Yes, some applications don't lend themselves to dividing them up into smaller, cheaper and redundant modules. Others might.

Don't think I'm not respecting your experience. But I think it is possible for some applications to go different ways.

Edit: And my apologies for the off-topic.

[woods170]

Having to spend money to fix a launcher which is at the end of its operational life, for a single mission, must not be welcome news in Europe. I wonder who is paying. Is it ESA or Ariane? Is it a change a specs or a case of not meeting the specs.

Emphasis mine.

The answer is: the Swiss government (Ruag is a Swiss company):

https://www.spaceintelreport.com/fairing-separation-issue-has-grounded-ariane-5-since-august-2020-also-affected-ulas-atlas-5/

Excess vibration during fairing separation on two European Ariane 5 missions in 2020 forced a months-long inquiry that has grounded the vehicle since August, with similar consequences for the United Launch Alliance Atlas 5, which uses the same fairing technology, government and industry officials said.

With the help of a recent emergency cash infusion by the Swiss government, Ariane 5 and Atlas 5 fairing manufacturer Ruag Space, based in Switzerland, apparently has identified the root cause of the issue and begun implementing corrective measures.

[heiterefahne]

I actually asked the Swiss government about this and they did not officially confirm it, just gave me a boilerplate answer on how ESA georeturn works.

I have also not seen any Swiss news regarding this, which is strange. I do think the government is funding this, but it's done in a very secretive way. I'd love to know de Selding's source.

[Jim]

The answer is: the Swiss government (Ruag is a Swiss company):

RUAG is owned by the Swiss government.

[woods170]

The answer is: the Swiss government (Ruag is a Swiss company):

RUAG is owned by the Swiss government.

That is almost correct. Ruag is owned by the state of Switzerland (or more accurately: the Swiss confederation). Government and state are closely joined but not quite the same thing.