Author Topic: SpaceX Falcon 9: To Static Fire or not to Static Fire; that is the question  (Read 54500 times)

Offline Norm38

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This is why I'm souring on static fires [referring to the static fire for the Starlink v1.0 Flight 9 launch vehicle].  Two days ago [June 24] they didn't have an O2 leak, now they do.  Should have launched on Wed instead of doing the dress rehearsal.
Static fires don't prevent problems from happening later on.
« Last Edit: 06/27/2020 05:00 am by zubenelgenubi »

Offline RocketLover0119

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This is why I'm souring on static fires.  Two days ago they didn't have an O2 leak, now they do.  Should have launched on Wed instead of doing the dress rehearsal.
Static fires don't prevent problems from happening later on.

Think about what you just said. You have 0 idea there was a leak when they fired, it’s possible there was hence why no immediate tweet from them. Also, if they launch the leak develops in flight, and ends in a loss of mission. Static fires really do help......
« Last Edit: 06/27/2020 05:00 am by zubenelgenubi »
"The Starship has landed"

Offline intelati

This is the third 5th launch?

I forget the exact count.

I expect to have static fires for the long life boosters. Maybe not the 2-3 launch boosters. Especially on Starlink/Rideshare missions.

Edit: Second of all time. So yeah. Two doesn't even make a pattern to go off of...

"once is happenstance twice is coincidence three times is a pattern..."
« Last Edit: 06/27/2020 05:01 am by zubenelgenubi »
Starships are meant to fly

Offline Norm38

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This is why I'm souring on static fires.  Two days ago they didn't have an O2 leak, now they do.  Should have launched on Wed instead of doing the dress rehearsal.
Static fires don't prevent problems from happening later on.

Think about what you just said. You have 0 idea there was a leak when they fired, it’s possible there was hence why no immediate tweet from them. Also, if they launch the leak develops in flight, and ends in a loss of mission. Static fires really do help......

The opposite. I know there was no leak on Wed, else they wouldn’t have fired. You have no certainty this leak would have resulted in failure. And you can’t predict this leak. It’s the N+1 fallacy, I know.  Flip the switch N times, that means N+1 won’t fail.

No. Because I have seen test 501 fail.

There is no benefit to making N large. Only more cost and lost time.
« Last Edit: 06/27/2020 05:01 am by zubenelgenubi »

Offline Lars-J

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This is why I'm souring on static fires.  Two days ago they didn't have an O2 leak, now they do.  Should have launched on Wed instead of doing the dress rehearsal.
Static fires don't prevent problems from happening later on.

Think about what you just said. You have 0 idea there was a leak when they fired, it’s possible there was hence why no immediate tweet from them. Also, if they launch the leak develops in flight, and ends in a loss of mission. Static fires really do help......

The opposite. I know there was no leak on Wed, else they wouldn’t have fired. You have no certainty this leak would have resulted in failure. And you can’t predict this leak. It’s the N+1 fallacy, I know.  Flip the switch N times, that means N+1 won’t fail.

No. Because I have seen test 501 fail.

There is no benefit to making N large. Only more cost and lost time.

But this wasn't test 501. Not even close...

If this was caused by a short few seconds static fire, you can bet your ass that a full launch to orbit would have caused it as well. (whether it would have been catastrophic is best to leave to SpaceX, hence the abundance of caution)

What you are advocating is the wishful thinking approach to testing, i.e "can't have test failures if you don't test". If you are afraid that adding a single additional test will break things, your system is not robust by any definition. (Of course things fail due to mechanical wear and tear, but that should occur much later)
« Last Edit: 06/27/2020 05:01 am by zubenelgenubi »

Offline Norm38

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If you are afraid that removing a single test will miss things, your system is not robust by any definition.

The N+1 fallacy works both ways.
But entropy only moves right.
« Last Edit: 06/27/2020 05:02 am by zubenelgenubi »

Offline Alexphysics

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The opposite. I know there was no leak on Wed, else they wouldn’t have fired.

And how do you know it? Were you there to check it out yourself? Do you even know in which condition that leak developped? Was prior to firing? During the firing? After the firing? What caused it? If you have to wonder, then that's why there are static fire tests. They don't know too much about the conditions of heavily used boosters, hence why they need to static fire them otherwise they may encounter serious problems on launch day and we would be living in between constant launch scrubs (just look at how ULA does when they don't perform WDR's on their rockets for months because they just do it on the most sensitive missions and then end up having multiple scrubs for stupid things that could have been caught on a WDR).

[zubenelgenubi: Yes, this post belongs in this splinter thread.]
« Last Edit: 06/27/2020 07:54 pm by zubenelgenubi »

Offline king1999

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If you are afraid that removing a single test will miss things, your system is not robust by any definition.

The N+1 fallacy works both ways.
But entropy only moves right.
Come on you know better. That's NOT a test. It was a WDR to shake things up for a 4 time flight old used rocket!
« Last Edit: 06/27/2020 05:03 am by zubenelgenubi »

Offline TorenAltair

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As far as I know, the leak rumour is only based on a post in Reddit. I would be careful to take such statements for fact.

Offline AndrewRG10

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As far as I know, the leak rumour is only based on a post in Reddit. I would be careful to take such statements for fact.

A good indication of its legitimacy is that it was deleted. No idea why but SpaceX really cracks down on employees whenever they do the PR teams job of being transparent. I've seen a couple of different reddit users talk about SpaceX stuff that turns out to be true and they always delete the post and account an hour or so after posting.
It's disappointing to see SpaceX crack down on transparency but it's a good indication that it's the truth.

Offline tyrred

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As far as I know, the leak rumour is only based on a post in Reddit. I would be careful to take such statements for fact.

A good indication of its legitimacy is that it was deleted. No idea why but SpaceX really cracks down on employees whenever they do the PR teams job of being transparent. I've seen a couple of different reddit users talk about SpaceX stuff that turns out to be true and they always delete the post and account an hour or so after posting.
It's disappointing to see SpaceX crack down on transparency but it's a good indication that it's the truth.

Nonsense.

Offline Thunderscreech

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A good indication of its legitimacy is that it was deleted.
If this is the criteria, then someone could first post something silly like "the static fire revealed that they had accidentally installed an MVac in one of the positions on the booster" then delete that message after a few minutes and have its subsequent legitimacy bolstered by the fact that it was deleted.

Maybe the O2 leak message was legit, maybe it wasn't, but regardless I wouldn't read too much into it being deleted as evidence for anything other than...  that it was deleted. 
Ben Hallert - @BocaRoad, @FCCSpace, @Spacecareers, @NASAProcurement, and @SpaceTFRs on Twitter

Offline Glorin

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As far as I know, the leak rumour is only based on a post in Reddit. I would be careful to take such statements for fact.

A good indication of its legitimacy is that it was deleted. No idea why but SpaceX really cracks down on employees whenever they do the PR teams job of being transparent. I've seen a couple of different reddit users talk about SpaceX stuff that turns out to be true and they always delete the post and account an hour or so after posting.
It's disappointing to see SpaceX crack down on transparency but it's a good indication that it's the truth.

Regardless of the rest, which others have addressed, I’d like to point out that “transparency” is not a requirement in any fashion, and is not even a realistic expectation. We certainly shouldn’t feel any special entitlement to additional info.

We certainly want them to relay lots of information. That’s great for us. But SpaceX is under no obligation to relay what’s going on. There are a ton of reasons they might not release information, many of them altogether boring.

Even if they do say something - perhaps the time hasn’t come yet. They’ll sometimes give a quick passing statement about issues leading to launch, during the webcast.

Online Welsh Dragon

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So this whole thread is based on someone who may or may not be making stuff up on Reddit? Really? Come on people....

Offline Norm38

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If you are afraid that removing a single test will miss things, your system is not robust by any definition.

The N+1 fallacy works both ways.
But entropy only moves right.
Come on you know better. That's NOT a test. It was a WDR to shake things up for a 4 time flight old used rocket!

If static fires are being done to “shake things up” and see what comes loose, I consider that to be a problem.
The only reason to intentionally cycle a system as a test is if you know there are infant mortality failure modes to get past.  After that cycles only add stress.

But expendable rockets aren’t allowed to have infant mortality, and reusable ones aren’t either.

Offline king1999

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If you are afraid that removing a single test will miss things, your system is not robust by any definition.

The N+1 fallacy works both ways.
But entropy only moves right.
Come on you know better. That's NOT a test. It was a WDR to shake things up for a 4 time flight old used rocket!

If static fires are being done to “shake things up” and see what comes loose, I consider that to be a problem.
The only reason to intentionally cycle a system as a test is if you know there are infant mortality failure modes to get past.  After that cycles only add stress.

But expendable rockets aren’t allowed to have infant mortality, and reusable ones aren’t either.
So after you changed the transmission or rebuilt the engine of your car, you don't want to drive around a little bit to see it is working fine before taking a long trip? No, no, "I consider that to be a problem, it will add stress to my transmission (or engine)."
So SpaceX refurbished the rocket for the fourth times, and cleaning up some components here, changing a few parts there. Don't you think it is beneficial for them to do a WDR to make sure nothing is missed in the process? I think that's common sense to me.
The MD engines are designed to work 10 flights without major maintenance. I don't think a few seconds of WDR firing would add any meaningful stress to them. If that's the case, I consider THAT to be a problem.

"Infant mortality" only applies to new rockets, and that's why some people consider F9 flights 2-3 are probably more reliable. Yes, rockets "aren't allowed" to have infant mortality, if you are the rocket God.

Offline quagmire

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B1048.5 should be enough of a reason to static fire the boosters that have the most use on them right now as they gather data on how well they handle. Granted they didn't discover the root cause of the issue until the actual flight, but they had an issue with it during the static fire which caused the launch to slip, then the launch was aborted at T-0 at ignition due to an engine reading out of limits. Then the actual launch had the engine cut out early. Now it is only speculation that all three events are related to the same engine, but at least the static fire revealed an issue.

Offline AndrewRG10

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Regardless of the rest, which others have addressed, I’d like to point out that “transparency” is not a requirement in any fashion, and is not even a realistic expectation. We certainly shouldn’t feel any special entitlement to additional info.

We certainly want them to relay lots of information. That’s great for us. But SpaceX is under no obligation to relay what’s going on. There are a ton of reasons they might not release information, many of them altogether boring.

Even if they do say something - perhaps the time hasn’t come yet. They’ll sometimes give a quick passing statement about issues leading to launch, during the webcast.

Oh yeh by no means is SpaceX or anyone obligated to tell what they're doing. They don't even have to do a webcast. They're definitely one of the more open, if not the most open aerospace corporations. However, if you want to call yourself a transparent company, you better live up to that by telling about why things are delayed, don't ignore a landing failure for several weeks or pretend the fairing catch attempt never happened when it splashed down.

Offline king1999

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Oh yeh by no means is SpaceX or anyone obligated to tell what they're doing. They don't even have to do a webcast. They're definitely one of the more open, if not the most open aerospace corporations. However, if you want to call yourself a transparent company, you better live up to that by telling about why things are delayed, don't ignore a landing failure for several weeks or pretend the fairing catch attempt never happened when it splashed down.
I don't recall SpaceX ever called themselves "transparent" or something like that. They are just doing their best and disclose enough to keep the public interested in space, which is in their own interest to make public opinions sway in their favor policy directions of the US Congress or Administration. People calling them "transparent" is comparative to other space companies like Blue Origin or ULA. And I don't think disclosing too much is in their interest considering all the competitors and other countries like China.

Offline Norm38

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So SpaceX refurbished the rocket for the fourth times, and cleaning up some components here, changing a few parts there. Don't you think it is beneficial for them to do a WDR to make sure nothing is missed in the process? I think that's common sense to me.
The MD engines are designed to work 10 flights without major maintenance. I don't think a few seconds of WDR firing would add any meaningful stress to them. If that's the case, I consider THAT to be a problem.

Is cleaning defined as “major maintenance”?  You do have a valid point, they did just have an issue due to cleaning fluid, so maybe they’re back to regular static fires until they work that out. 
But long term they should not need to fire if they didn’t do “major” work or replace engines.
It’s all about not doing harm.

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