Author Topic: Vulcan VC2S V001 - Peregrine Lander - CCSFS SLC-41 - 8 Jan 2024 (07:18 UTC)  (Read 417666 times)

Online LouScheffer

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I think structural safety factors this low are only used on un-crewed rockets.  Since ULA would like to keep the option open of human-rating the rocket later, I suspect Vulcan uses safety factors of at least 1.4-1.5 (I don't know the current spec, but I've seen both these numbers quoted before for human-rated rockets.)
1.25
A factor of 1.25 is for yield (permanent change in shape).  1.4 is the margin for failure.  See page 29, "Minimum Design and Test Factors for Metallic Structures", in the NASA document NASA-STD-5001: STRUCTURAL DESIGN AND TEST FACTORS OF SAFETY FOR SPACEFLIGHT HARDWARE"
Vulcan is not a NASA vehicle.
Very true - ULA does not have to use 1.4 .  Apparently Delta-4 did not either.   In a 2009 ULA document outlining the changes needed for human-rating, ULA mentions that Delta would need to be upgraded to meet the 1.4 spec, but says nothing about Atlas-Centaur. 

This implies Atlas-Centaur already met the 1.4 spec.  Then a lower margin for Vulcan-Centaur could explain how they could use even thinner steel for the new Centaur, despite the larger diameter.  All other things being equal, larger diameter means larger hoop stress, so you'd expect a thicker skin, not thinner.  I was guessing that perhaps they found some way to reduce the required pressure in the tank, but an alternative (at least partial) explanation is that the new tank runs with thinner margins.  This would make it even more of a redesign and not a simple upgrade, and could have contributed to the recent test failure.

Offline Jim

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, so you'd expect a thicker skin, not thinner.  I was guessing that perhaps they found some way to reduce the required pressure in the tank, but an alternative (at least partial) explanation is that the new tank runs with thinner margins.  This would make it even more of a redesign and not a simple upgrade, and could have contributed to the recent test failure.

It is thicker.

Offline Jim

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Very true - ULA does not have to use 1.4 .  Apparently Delta-4 did not either.   In a 2009 ULA document outlining the changes needed for human-rating, ULA mentions that Delta would need to be upgraded to meet the 1.4 spec, but says nothing about Atlas-Centaur. 

This implies Atlas-Centaur already met the 1.4 spec.

Human rating doesn't require a specific safety factor.

Online LouScheffer

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Very true - ULA does not have to use 1.4 .  Apparently Delta-4 did not either.   In a 2009 ULA document outlining the changes needed for human-rating, ULA mentions that Delta would need to be upgraded to meet the 1.4 spec, but says nothing about Atlas-Centaur. 

This implies Atlas-Centaur already met the 1.4 spec.
Human rating doesn't require a specific safety factor.
Irrelevant.  The document explicitly states that if the 1.4 requirement is re-instated, then Delta will need to be modified.  It makes no such statement about Atlas-Centaur, hence the implication.

Online LouScheffer

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, so you'd expect a thicker skin, not thinner.  I was guessing that perhaps they found some way to reduce the required pressure in the tank, but an alternative (at least partial) explanation is that the new tank runs with thinner margins.  This would make it even more of a redesign and not a simple upgrade, and could have contributed to the recent test failure.
It is thicker.
You are correct.  I was confused by the ULA graphic, which visually implies the Centaur-III has dime-like thickness.  But ULA  has elsewhere stated:  "Centaurís stainless-steel tank walls are 0.02 inches thick, thinner than a dime."  So Centaur V's walls are about twice as thick, which is roughly what would be expected.
« Last Edit: 07/10/2023 04:54 pm by LouScheffer »

Offline Jim

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Very true - ULA does not have to use 1.4 .  Apparently Delta-4 did not either.   In a 2009 ULA document outlining the changes needed for human-rating, ULA mentions that Delta would need to be upgraded to meet the 1.4 spec, but says nothing about Atlas-Centaur. 

This implies Atlas-Centaur already met the 1.4 spec.
Human rating doesn't require a specific safety factor.
Irrelevant.  The document explicitly states that if the 1.4 requirement is re-instated, then Delta will need to be modified.  It makes no such statement about Atlas-Centaur, hence the implication.

Nope.  The implication is wrong.  One author was Boeing and the other LM.  Each wrote about their own vehicles independently.
« Last Edit: 07/10/2023 06:30 pm by Jim »

Online FutureSpaceTourist

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The third BE-4 Vulcan flight engine exploded during testing (posted here).

https://twitter.com/13ericralph31/status/1678846571704885249

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oof, this could be a huge setback if Blue concludes that the Cert-1 BE-4s have the same flaw as the engine that failed 😬

Of course even if not, could still delay later Vulcan flights (although Blue have said they will still meet their engine delivery commitments this year).

Letís keep this thread purely on inaugural flight impact, if any. Wider implications for the Vulcan programme belong here (with discussion of the engine issue on the BE-4 thread).
« Last Edit: 07/11/2023 07:37 pm by FutureSpaceTourist »

Online Vettedrmr

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I clicked "like", just as a thanks for keeping us updated.  Certainly don't "like" the news.
Aviation/space enthusiast, retired control system SW engineer, doesn't know anything!

Online FutureSpaceTourist

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ULA already saying no expected impact:

https://twitter.com/thesheetztweetz/status/1678850341989695489

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ULA statement: "The BE-4 testing issue is not expected to impact our plans for the Vulcan Cert-1 mission."

Quote from: ULA statement
The BE-4 testing issue is not expected to impact our plans for the Vulcan Cert-1 mission. The Cert-1 engines successfully passed acceptance testing and the BE-4 engines are qualified for the Cert-1 mission.

Suggests they think itís an engine specific defect, or at least that if Cert-1 engines had it then they wouldnít have completed testing successfully.
« Last Edit: 07/11/2023 08:13 pm by FutureSpaceTourist »

Online FutureSpaceTourist

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Voila:

https://twitter.com/torybruno/status/1678865222604574720

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Sure.  Every engine, elex box, COPV, etc, gets an Acceptance Test (ATP) as they come off the line to verify good workmanship.  (The one time Qual verifies the design.  BE4 is qualified).  The BE4's on Cert1 have passed ATP, as have many others.  This engine failed ATP.

Online FutureSpaceTourist

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How confident are you that this was a result of poor workmanship and not a design flaw that is exposed under specific circumstances?

https://twitter.com/torybruno/status/1678955725366886401

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Very

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@torybruno is the maiden Vulcan launch affected by this?

https://twitter.com/torybruno/status/1678956991648243713

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Very unlikely

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@torybruno Does the BE-4 test failure set back the Vulcan launch at all?

https://twitter.com/torybruno/status/1678957842760634370

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Very unlikely. We always check every ATP anomaly for any cross over, but not expected here
« Last Edit: 07/12/2023 05:49 am by FutureSpaceTourist »

Online deadman1204

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Is peregrine able to take advantage of this time?

Offline lrk

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Is peregrine able to take advantage of this time?

Not really, the Peregrine lander has been ready and waiting for its ride for a few months now. 

Online LouScheffer

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Irrelevant.  The document explicitly states that if the 1.4 requirement is re-instated, then Delta will need to be modified.  It makes no such statement about Atlas-Centaur, hence the implication.
Nope.  The implication is wrong.  One author was Boeing and the other LM.  Each wrote about their own vehicles independently.
Interesting.  It's as if the two vehicles were competing against each other, despite both being ULA. This would lead to exactly the opposite conclusion.  The Delta team would brag that they could meet the 1.4 spec (should it be reinstated), where the Atlas folks would be silent since they had no plausible way to meet the spec.

So what safety factor was used on Atlas V-Centaur?

Offline sebk

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So what safety factor was used on Atlas V-Centaur?

AFAIR 1.2 or 1.25

Online FutureSpaceTourist

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https://twitter.com/sciguyspace/status/1679506723386580992

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United Launch Alliance CEO Tory Bruno is holding a media call on the status of the Vulcan rocket. "Development is essentially done," he says. Vehicle is fully qualified with the exception of the structure of the Centaur V. I'll add updates here.

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Bruno says the Centaur V failure on March 29 occurred during the 15th test of the tank. A hydrogen leak developed near the front end of the stage. Lasted for 4.5 minutes, a crack propagated.

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Bruno describes the "fractography" analysis that went into determining the origin of the crack in the liquid hydrogen tank. Leak originated near the top of the hydrogen dome. Built a model to understand the loads and stresses in this area.

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Found that while the stress in this area was high, the structure still should not have failed. Issue was due to welds. Laser welding used on Centaur 5, rather than arc welding on Centaur 3. Combination of higher stress than anticipated and slightly less strong welds --> failure.

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The fix is relatively simple; strengthening the top of the tank with an extra ring of stainless steel.
« Last Edit: 07/13/2023 03:22 pm by FutureSpaceTourist »

Online FutureSpaceTourist

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https://twitter.com/sciguyspace/status/1679511021252145152

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Tory Bruno confirms that the goal now is to launch Vulcan's Certification-1 mission in the fourth quarter of 2023.

Online FutureSpaceTourist

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https://twitter.com/alexphysics13/status/1679521017465634817

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Asked about whether Vulcan's first flight, Cert-1, could still be successful without mods, @torybruno says it could have been good enough but this flight is carrying customers.

"Other people could have considered flying in the condition we were at but we're not other people"

Offline Robert_the_Doll

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https://twitter.com/w_robinsonsmith/status/1679516007910502403
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Bruno: Very pleased with test. Points to Astrobotic for timing of delivering its Peregrine lander to the Cape for processing.

Online FutureSpaceTourist

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https://twitter.com/jeff_foust/status/1681691023439986689

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In a #GlennSymposium2023 panel, Dan Hendrickson of Astrobotic says their Peregrine lander is "completely finished" and that company just waiting for the call from ULA to ship to the Cape for launch on the first Vulcan Centaur (now projected for the 4th quarter of this year.)

 

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