totm nov 2023 SpaceX Discussion Thread

[RCgothic]

You don't know those were all supposed to be 120s burns.

[sevenperforce]

2 hours ago, Exoscientist said:

But going by counting the number of tests for the Raptor that fail to reach that 115 to 120 second mark, it may be 1 in 5 to 1 in 6 fail to reach it. Note as the author of the video observes some tests are planned to be shorter. For some for instance they were intended to be about 47 seconds long. But there are a block of tests I marked off in the attached image that appear to be aiming for that 115 to 120 second mark, and several of them don’t make it. I estimate 5 or 6 out of the 30 I marked off failed to reach that planned burn length.

Another questionable issue of these static tests is the planned lengths. The largest portion them were of a planned length of about 120 seconds, 2 minutes. But judging by the two test flights the actual burn time for the booster is in the range of 2 minutes 39 seconds to 2 minutes 49 seconds range. Only very few of the test stand burns went this long or longer.

The video gives a link where you can watch the test stand burns NSF.live/McGregor. Another useful aspect here is you may be able to judge the power level of the burns. There is a graphic that shows the sound level of the burns. From that you may be able to judge whether or not the engines were firing at or close to full thrust.

In the image below, the burns in white are those shorter burns of about 47 second lengths the author of the video made note of. They may be tests of the boost back or landing burns. The ones I’m commenting on are under the yellow bar, which I estimate to be at about the120 burn time. There 5 or 6 out of 30 don’t reach the planned burned time.

Dude, this is hogwash. You have absolutely no idea what the planned burn time was for any of these tests, what was being tested, whether these were acceptance tests or tests to failure or outlier tests...nothing.

You're looking for patterns that don't exist. You might as well throw in your lot with the day-trading dopes arguing about which candles predict a new stock market trend.

[tater]

 

2 hours ago, Exoscientist said:

Only very few of the test stand burns went this long or longer.

Arguing about Raptor is completely pointless. It will work, or it won't. It will get better, or it won't. What % of early Merlin tests reached some arbitrary timing? Right, we have no idea. Be-4? Yep, we have no clue.

They're doing what they are doing, and it should not matter to anyone other than SpaceX. Why do you care? Seriously, why? They are not spending OUR money for this, they are spending THEIR money. They only get paid taxpayer money if/when they hit milestones. It might blow up and rain rocket parts into the ocean, maybe? Again, so what—every single other rocket ever flown has deposited 100% of itself into the ocean (except for junk left in space, which is its own problem).

[StrandedonEarth]

4 hours ago, Exoscientist said:

The author says the reliability is high because “most” tests were able to reach a planned length of 115 to 120 seconds.

SpaceX is unusually public with their testing. Does anyone know how many RS-25s failed acceptance testing? RS-68s? RL-10s, F-1s, J-2s? BE-4s certainly had a troubled development; how many of those make it through acceptance testing these days? How many Merlins get scrapped without flying?

The reason high-tech precision machinery is so expensive is that not all units produced pass testing, just like with silicon chips.

"Perfect" is the enemy of good enough, something I fight with myself about as I can be a bit of a perfectionist. Mucking around to make something (more) perfect can end up ruining the piece. Granted, with something like a rocket engine, often only perfect is good enough, but to maintain high production rates you can't try to make everything perfect every time. Mistakes happen, things are missed. That's why there is Quality Control/Assurance, audits and inspections, and finally acceptance testing. If it's not perfect enough, it gets fixed or scrapped. Some get scrapped before testing, some are scrapped after testing, and some are passed for use. That's the nature of manufacturing, vs the hand-made, may-as-well-be-custom-made ways of early rocketry, when still not everything made it to the test stand. I will add that I work in manufacturing, although the tolerances involved  are not anywhere near the precision required of aerospace.

For that matter, I doubt anything is ever truly perfect. There are tolerances, and if a product is within tolerance, it's all good. But if you take a close look, there will still be minute, tolerable imperfections. NASA is (was?) known for taking tolerances to seven decimal places, but if you take a perfectly (within tolerance) round shaft and go down another decimal place or two, there will still be peaks and valleys: no longer perfectly round. From the Moon, the Earth looks perfectly round, but I can look out my window at mountains that say otherwise.

How many Raptor tests are for acceptance testing, versus testing new materials/configurations/ideas, to see if it'll work for future versions? Nobody outside SpaceX knows. This is why they test, so they can find flaws and then test the fixes for the flaws. Every failure is a lesson. The only real cause for concern is when the same mistakes keep happening. Do the Raptors keep failing for the same reasons on identical hardware? That's a human problem, and it is one definition of insanity: doing the same things over and over while expecting different results. If there is one thing not happening at Boca Chica, it's doing the same things over and over (unless it already works, like making rings and barrel sections, and even those methods may still be getting iterated); every build has changes that are thought to improve the vehicle. Once everything is functioning the way it should, and only then, the design gets frozen, like F9B5.

But hey, if you want to build a test stand for full-up, full-mission-duration, full power, full 33-engine Superheavy testing out of your own pocket, I don't think SpaceX will object. Good luck getting permission to build it anywhere in this hemisphere, though.

Edited January 6 by StrandedonEarth
perfectionism acting up, hope I don't wreck my post

[Exoscientist]

8 hours ago, zolotiyeruki said:

This is the question that Exoscientist has been studiously avoiding.  If, like SpaceX, you have the ability to flight test the hardware, why would you limit yourself to ground testing? I'm trying to think of what advantages a ground test fire would have over a flight test, and I'm coming up empty-handed. 

…

 I have discussed this. It is standard industry procedure to do full thrust, full up(all engines), full flight duration(actual mission length) static fire tests before doing flight tests. Even SpaceX did this when qualifying the Merlins on the Falcon 9 for flight:

SpaceX Testing - Falcon 9 Engine Test
147,136 views  Nov 25, 2008
The full mission duration test firing of the Falcon 9 first stage lasting nearly 3 minutes. The nine Merlin engines produced 855,000 lbs. of thrust and consumed over half a million pounds of liquid oxygen and rocket grade kerosene during the test.

 And this video shows this being done for the Saturn V first stage:

Saturn V S IC Static Firing (archival film)
34,163 views  Aug 15, 2018
This film provides an overview of testing of the Saturn V first stage, the S-IC stage at NASA's Marshall Space Flight Center during the Apollo Program. The five F-1 engines which made up the stage generated a combined seven and a half million pounds of thrust.

 

 

 Such tests are more challenging for the engines and the stages. But that is the point.

It is because such tests were done  that the Falcon 9 and the Saturn V were spectacular successes.

  Bob Clark

 

 

Edited January 6 by Exoscientist

[tater]

11 minutes ago, Exoscientist said:

 I have discussed this. It is standard industry procedure to do full thrust, full up(all engines), full flight duration(actual mission length) static fire tests before doing flight tests. Even SpaceX did this when qualifying the Merlins on the Falcon 9 for flight:

Don't care at all what "industry" does, it's completely irrelevant. How many crew missions to ISS has Starliner flown? They did it the "industry way."

So try to answer his questions from first principles. There are pros and cons of both methods I'm sure we cal all think of—many have been posted recently in this thread.

11 minutes ago, Exoscientist said:

It is because such tests were done  that the Falcon 9 and the Saturn V were spectacular successes.

Falcon had some failures.

Scenario:

IFT-3 (or 4, or 5) is completely successful. They get SS and SH working, then they manage SH recovery, much later they finally get SS to be reusable (the long pole)—all via flying to test.

A new rocket company challenger appears! Should they do it the way every other company did it back in the day, or should they do it how the largest rocket company on Earth, who just managed full reuse on the largest rocket ever flown did it?

Edited January 6 by tater

[tater]

BTW, SLS was never tested all up for a static fire of ANY duration, much less full duration. To actually test it the way you want SS/SH tested, they should have built an entirely new pad at KSC, designed to fire the SRBs for full duration, along with the RS-25s.

Pro—they would have done what you currently demand.

Con—Lesse, ~$1.17B in SRB cost for testing. Also a new or remodeled pad—what's a 39B type pad cost these days if the taxpayer is paying? Billions, right? Maybe they just remodel 39B... if that is even possible. Still billions, maybe fewer billions than a new one? Schedule risk? Years. Oh, and the test will be the first time the pad is ever used, so maybe they have an IFT-1 event, right? EIR? Launch and possible explosion/deflagration are already accounted for, but that's not the same as several minutes blasting away on the ground.

[sevenperforce]

10 hours ago, Exoscientist said:

Such tests are more challenging for the engines and the stages. But that is the point.

I am pretty damn sure that all-up, full-mission-duration static fire tests are NOT more challenging for engines and stages than all-up, full-mission-duration launch tests. 

[JoeSchmuckatelli]

1 hour ago, sevenperforce said:

I am pretty damn sure that all-up, full-mission-duration static fire tests are NOT more challenging for engines and stages than all-up, full-mission-duration launch tests. 

Do static fires experience Max Q? 

By the way - if using a candle for market prediction, is it better to use scented or pure beeswax? 

[darthgently]

1 hour ago, JoeSchmuckatelli said:

Do static fires experience Max Q? 

By the way - if using a candle for market prediction, is it better to use scented or pure beeswax? 

Max Q does indeed occur during a static fire, though it will be substantially lower than max Q during a test flight and very near ambient pressure.  Ha

For predicting and outpacing the future, no matter what type of candle is involved, best results occur when burning the candle from both ends.  By this is meant that working longer hours and not sleeping will give one faster reaction time to events.  This optimized OODA loop is your best bet. 

Disclaimer:  Actually knowing the future involving chaotic self-referentiial processes is considered entirely candle resistant . No warranties or guarantees are implied and by reading this viewer agrees to all terms and conditions that may change without notice or forethought 

 

Edited January 6 by darthgently

[Exoscientist]

18 hours ago, sevenperforce said:

Dude, this is hogwash. You have absolutely no idea what the planned burn time was for any of these tests, what was being tested, whether these were acceptance tests or tests to failure or outlier tests...nothing.

You're looking for patterns that don't exist. You might as well throw in your lot with the day-trading dopes arguing about which candles predict a new stock market trend.

 You don’t have to take the video authors word on this. You can judge for yourself if there is a most common length over which most of the tests are done:

 

 

  Robert Clark

Edited January 6 by Exoscientist

[tater]

@Exoscientist

14 hours ago, tater said:

Scenario:

IFT-3 (or 4, or 5) is completely successful. They get SS and SH working, then they manage SH recovery, much later they finally get SS to be reusable (the long pole)—all via flying to test.

A new rocket company challenger appears! Should they do it the way every other company did it back in the day, or should they do it how the largest rocket company on Earth, who just managed full reuse on the largest rocket ever flown did it?

This is a simple question to answer. You want to require a particular flow to first launch because "that's how it's done" when that flow developed organically during the early space program, and was not decided on from first principles.

Testing is testing. It doesn't matter at all if the rocket is tested on the ground, or flying.

Ground testing used to give you more data, because remote sensors and data rates were low. This is no longer the case.

Ground testing doesn't give you important data about the stage in actual flight. How do the engines function at 3-4g?

 

 

On topic:

 

[Shpaget]

15 hours ago, Exoscientist said:

It is standard industry procedure to do full thrust, full up(all engines), full flight duration(actual mission length) static fire tests before doing flight tests.

Did space shuttle have those? Was the full configuration ever static tested (two SRBs + orbiter with the big boy tank)?

[tater]

32 minutes ago, Shpaget said:

Did space shuttle have those? Was the full configuration ever static tested (two SRBs + orbiter with the big boy tank)?

No rocket with SRBs has ever been tested in this way by anyone*—and the SRB/core engine  interaction (largely heating) is a nontrivial factor. It's a testing regime that is ideal for programs with more money than hardware.

(and cost-plus give them ~infinite money)

* that I am aware of

Edited January 6 by tater

[RCgothic]

3 hours ago, Exoscientist said:

 You don’t have to take the video authors word on this. You can judge for yourself if there is a most common length over which most of the tests are done:

 

 

  Robert Clark

Even if it was a knife-edge of mostly exactly 120s tests with a few falling short (which this data isn't), that would *still* not say anything about raptor's reliability because 3rd party observers have no idea what's being tested or what the abort criteria are.

It could be GSE faults. It could be test aborts more conservative than flight. It could be testing above 100% throttle. It could be deliberate tests to failure.

Nothing can be inferred definitively from this data.

[PakledHostage]

5 hours ago, JoeSchmuckatelli said:

By the way - if using a candle for market prediction, is it better to use scented or pure beeswax? 

I understand that bovine excrement works well...

Also, while I am here, I saw this article in my feed this morning:

https://www.nasa.gov/general/electro-luminescently-cooled-zero-boil-off-propellant-depots/

Might be a solution for the boil-off expected for some of SpaceX's orbital fuel depot aspirations?

[CatastrophicFailure]

On 1/4/2024 at 1:32 PM, sevenperforce said:

Agreed. As outlined above, building an actual single-launch architecture for meaningful moon landings would require a rocket almost double the liftoff mass of the Saturn V (and likely more).

In that case, and also checking that nostalgia box, I humbly submit my 9000-tonne F-1A powered Soyuz. 

As an added bonus, the cryogenics plant (and probably the entire launch facility) could be powered by harnessing the energy of both Korolev and Von Braun spinning in their graves.

[SunlitZelkova]

2 hours ago, CatastrophicFailure said:

As an added bonus, the cryogenics plant (and probably the entire launch facility) could be powered by harnessing the energy of both Korolev and Von Braun spinning in their graves.

Harvesting energy from souls in the after life to power a rocket factory sounds like the plot of an anime.

[tater]

SpaceX is targeting Sunday, January 7 for a Falcon 9 launch of 23 Starlink satellites to low-Earth orbit from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station in Florida. Liftoff is targeted for 5:35 p.m. ET, with backup opportunities available until 7:59 p.m. ET. If needed, additional opportunities are also available on Monday, January 8 starting at 4:01 p.m. ET.

 

[CatastrophicFailure]

On 1/5/2024 at 7:31 PM, tater said:

BTW, SLS was never tested all up for a static fire of ANY duration, much less full duration. To actually test it the way you want SS/SH tested, they should have built an entirely new pad at KSC, designed to fire the SRBs for full duration, along with the RS-25s.

Pro—they would have done what you currently demand.

Con—Lesse, ~$1.17B in SRB cost for testing. Also a new or remodeled pad—what's a 39B type pad cost these days if the taxpayer is paying? Billions, right? Maybe they just remodel 39B... if that is even possible. Still billions, maybe fewer billions than a new one? Schedule risk? Years. Oh, and the test will be the first time the pad is ever used, so maybe they have an IFT-1 event, right? EIR? Launch and possible explosion/deflagration are already accounted for, but that's not the same as several minutes blasting away on the ground.

And then, after all that, a pressurant tank inside the core stage pops loose due to faulty struts and causes a RUD on the first flight test… because that’s exactly the kind of issue that can only be uncovered under actual flight conditions. No amount of static fires would ever find it, because it only happens under flight loading. 
 

And that’s just one more example. 

On 1/6/2024 at 6:56 AM, JoeSchmuckatelli said:

By the way - if using a candle for market prediction, is it better to use scented or pure beeswax? 

Oxygen. 

On 1/6/2024 at 10:19 AM, tater said:

No rocket with SRBs has ever been tested in this way by anyone*—and the SRB/core engine  interaction (largely heating) is a nontrivial factor. It's a testing regime that is ideal for programs with more money than hardware.

(and cost-plus give them ~infinite money)

* that I am aware of

Including that rather anticipated candle they’re about to light tomorrow morning…

[tater]

12 minutes ago, CatastrophicFailure said:

Including that rather anticipated candle they’re about to light tomorrow morning…

Just after midnight here in NM, and still today for peeps on the west coast.

[magnemoe]

19 hours ago, CatastrophicFailure said:

In that case, and also checking that nostalgia box, I humbly submit my 9000-tonne F-1A powered Soyuz. 

As an added bonus, the cryogenics plant (and probably the entire launch facility) could be powered by harnessing the energy of both Korolev and Von Braun spinning in their graves.

Nice that I was not the only one who used the Soyuz boosters on an Saturn 5, it had to be done. also made an mini Soyuz for Eve accent. 

[tater]

I was at dinner when this launch happened:

 

Thing was in the hanger until right before launch.

 

[zolotiyeruki]

On 1/5/2024 at 9:06 PM, Exoscientist said:

 I have discussed this. It is standard industry procedure to do full thrust, full up(all engines), full flight duration(actual mission length) static fire tests before doing flight tests. Even SpaceX did this when qualifying the Merlins on the Falcon 9 for flight:

A few counterpoints:

1) You have written many, many words, but you still haven't answered the simple question: "what benefit would ground testing give you that modern flight testing doesn't?" 

2) Sure, SpaceX and NASA have done integrated tests in the past.  That doesn't mean they absolutely must adhere to that same practice for every engine and every vehicle.  A wise young guy once told me "tradition has to claim on sanctity."  Just because a full-up, full-thrust, full-duration static test was called for under a previous program a decade or a freaking half century ago doesn't mean that the same test is appropriate for this program at this stage with SpaceX's current development philosophy.

[magnemoe]

2 minutes ago, zolotiyeruki said:

A few counterpoints:

1) You have written many, many words, but you still haven't answered the simple question: "what benefit would ground testing give you that modern flight testing doesn't?" 

2) Sure, SpaceX and NASA have done integrated tests in the past.  That doesn't mean they absolutely must adhere to that same practice for every engine and every vehicle.  A wise young guy once told me "tradition has to claim on sanctity."  Just because a full-up, full-thrust, full-duration static test was called for under a previous program a decade or a freaking half century ago doesn't mean that the same test is appropriate for this program at this stage with SpaceX's current development philosophy.

This, nobody has done an full burn with SRB for for good reasons, heavy lift orbital rockets here not military stuff. But srb add stress to craft , side boosters do same is true for falcon heavy, who was delayed by years so spacex dropped side boosters from their plan.