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SpaceX concludes anomaly investigation, sets return to flight target date (spacex.com)
309 points by dtparr on Jan 2, 2017 | hide | past | web | favorite | 131 comments

The accident investigation team concluded that one of the three composite overwrapped pressure vessels (COPVs) inside the second stage liquid oxygen (LOX) tank failed. Specifically, the failure was likely due to the accumulation of oxygen between the COPV liner and overwrap in a void or a buckle in the liner, leading to ignition and the subsequent failure of the COPV.

The investigation team identified several credible causes for the COPV failure, all of which involve accumulation of super chilled LOX or SOX in buckles under the overwrap. The corrective actions address all credible causes and focus on changes which avoid the conditions that led to these credible causes. In the short term, this entails changing the COPV configuration to allow warmer temperature helium to be loaded, as well as returning helium loading operations to a prior flight proven configuration based on operations used in over 700 successful COPV loads. In the long term, SpaceX will implement design changes to the COPVs to prevent buckles altogether, which will allow for faster loading operations.​

SpaceX is targeting return to flight from Vandenberg's Space Launch Complex 4E (SLC-4E) with the Iridium NEXT launch on January 8.

Are COPVs a universal thing in rocketry? Or has SpaceX actually loaded fuel into its rockets over 700 times?

It's true that COPVs are rather common in aerospace (being the lightest pressure tank technology available).

> Or has SpaceX actually loaded fuel into its rockets over 700 times?

This. SpaceX has done development test cycles, and for each launch performs stage acceptance tests at McGregor Texas and both "wet dress rehearsals" (now generally skipped) and static fires at their launch pads. All of these operations involve loading and unloading helium and LOX.

Given the nature of carbon-fiber composite manufacturing where it's usually applied in layers, is the risk of a tiny bubble a lot higher when it's subjected to repeated heating/cooling cycles?

Some sort of gas injection system is essentially universal in rocketry since you need something to maintain tank pressure as you use the fuel in the tank. The helium vessels aren't always COPVs, sometimes it comes from outside the tank, and some rockets use something called autogenous pressurization where propellant is heated to gas to take up that extra space. And some rockets manage without pressurization entirely though I believe only very low performance ones.

SpaceX hasn't flow anywhere close to 700 flights but a lot of testing would involve fuel loading so the 700 figure sounds high but not unreasonably high to me.

Not 100% sure, but each stage has multiple COPVs and there are two stages per vehicle, plus each vehicle is loaded multiple times (minimum two, for the static fire and the actual launch, and possibly more than that), so 700 occurrences of an individual COPV being loaded over the history of SpaceX (with ~30 total launches) is not totally ridiculous.

I believe it's a minimum of 3 loads per vehicle, as they're also tested at McGregor, Texas before being shipped to the launch site. Launch scrubs after propellant loading would add more, as would R&D testing.

They've done almost 30 Falcon 9 launches now. If there are 4 per vehicle and 3 loads per launch, that's about 360 loads just from that.

The design which failed in September has three COPVs just in the second stage LOX tank - for a picture, see http://spaceflight101.com/falcon-9-amos-6/wp-content/uploads... there are additional helium COPVs in the (much larger) first stage LOX tank.

Ah, I just assumed it was 3 in S1 (as mentioned in another comment) and 1 in S1 (pulled out of my rear). If it's 6 per vehicle, that would mean at least 540 fills, not counting scrubs and R&D tests.

For the broken link, there's just a stray semicolon at the end. Working version: http://spaceflight101.com/falcon-9-amos-6/wp-content/uploads...

Link not working, FYI.

I don't believe they are counting all the separate COPVs per rocket. 30 launches, with multiple static fires, wet dress rehearsals, acceptance testing, and the launch itself... it adds up quick.

That's just for the actual production flights, as well. Add in all their testing (Grasshopper, etc), and I have no problem believing they have tanked propellants on over 700 occasions.

If there are 3 in the first stage alone, and they static fire the stages before launching, I can see that adding up.

To save you from the endless bla bla bla:

...concluded that one of the three composite overwrapped pressure vessels (COPVs) inside the second stage liquid oxygen (LOX) tank failed

...failure was likely due to the accumulation of oxygen between the COPV liner and overwrap in a void or a buckle in the liner, leading to ignition and the subsequent failure of the COPV.

.... corrective actions .. short term ... changing the COPV configuration to allow warmer temperature helium to be loaded ... long term, SpaceX will implement design changes to the COPVs to prevent buckles altogether

Next launch on January 8th.

Two things I learned from the report, one was that the helium tanks are actually inside the oxygen tanks. All the rockets that I can recall seeing the insides of, had the helium tanks as a sort of 'ring of pearls' around the end of the tank. Clearly from a volume perspective it doesn't matter if they are inside or outside, and from a thermal perspective it means the LOX can keep the helium cool (or vice versa I guess).

And the second is that their wrapping method allows for the creation of voids between the inner aluminum tank and the carbon fiber wrap. I can certainly imagine how that could happen with carbon fiber prepreg (it's a prewoven fabric which maximizes strength by pre-laying out the various ways the fiber goes through it) but if you were to spool on straight up fiber that would make it easier to be conformal.

I wonder if other people do the 'tanks within tanks' architecture and if so how they avoid voids and buckles in their overwrap.

In general it seems the voids and buckles problem is only seen at very very low temperatures. The AMOS-6 failure occured because the LOX was loaded too quickly after loading the helium tanks, without allowing the He to come up in temperature.

SpaceX was pushing the loading speed to expand the flight window. The update (and Ms. Shotwell a few months ago) indicate the short term fix for this is to slow down the propellant loading to allow the He to warm up a bit before LOX arrives... Which is a long way to say that it's likely other companies have not pushed the envelope far enough to encounter this voids and buckles problem.

The update also says they will eventually adjust their COPV construction to eliminate this problem and return to rapid propellant loading, but I doubt we'll hear anything about HOW they improve it. A not insignificant amount of SpaceX's "secret sauce" is in their composits manufacturing (case in point the enormous ITS LOX tank recently tested.)

Helium has a much lower boiling point (~4K vs ~90K) than oxygen, and so at the same temperature would have to be at significantly higher pressure to stay liquid. I'd expect that putting the helium tank inside the oxygen tank would allow the helium tank to be of lighter construction, since it would only have to withstand the difference in pressure between the liquid helium and liquid oxygen. Scaling up the oxygen tank to compensate for lost volume would be lighter due to the squared/cubed law.

I imagine the reason it's not done this way traditionally is that it'd be a pain to fabricate.

I think this might have something to do with it. SpaceX being SpaceX, they have a significant advantage in the agility of their fabrication process(es).

I'm not aware of any modern US rockets (other than SpaceX) that install COPV tanks inside LO2 fuel tanks. SpaceX is certainly getting a performance gain from the design at the risk of these kind of thermal related failure modes. I hope they figure out how mitigate these failure modes as a COPV exploding inside a LO2 tank is scary! Especially once they start flying humans on-board in 2018 or 2019.

This NASA article on COPV failure is enlightening. https://www.nasa.gov/offices/nesc/home/Feature_COPVs_Jan-201...

Turns out COPV's have a tendency to explode semi randomly, with failure modes that are not fully understood

The failure modes are slightly better understood now, as are the boundaries between success and failure!

It's surprising how much of a disruption this caused to their launch schedule, but it's great that they got to the bottom of the issue before repeating the process on any further rockets.

The worst kind of bug is the intermittent one that you can't reproduce or see in logs. With only 35-55 milliseconds of metrics leading up to the event and nearly obliterated evidence, it seemed nearly impossible they would be able to nail down the exact cause.

Critics have pointed out risks in SpaceX's method of loading supercooled fuel. Accidentally forming solid oxygen around carbon fibers from a buckling overwrap is an example of this.

There are benefits, but they will need to find and prevent all these possible edge cases exposed by the new method.

This "anomaly" caused hundreds of millions of dollars in losses, and was an unprecedented failure mode. It doesn't surprise me at all that it disrupted the launch schedule for the better part of a year (edit: actually the lesser part of a year, about four months total if they launch soon). If they manage to return to flight this month, it strikes me as rather quick.

I wonder if supercooled propellants are really worth it. It seems like a huge risk in exchange for a small performance increase. Hopefully this will be the last vehicle loss they suffer from it.

My understanding is it effectively reduces launch costs by ~25% by getting ~30% more mass to LEO. Really if it increases risks of failure by less than 10% it's probably worth it for unmanned rockets.

PS: High launch costs set up a cost escalation as satellites are so expencive they can't fail. Which means launches need a really high success rate. If you could get 10,000kg to LEO for say 1 million but had a 40% failure rate you would see a very different approach with much lower overall costs.

With this explosion, there was a ~$200 million satellite destroyed as part of a ~$60 million launch. We'll probably see much cheaper payloads to go along with cheaper launches eventually, but for right now the payload loss dominates, so you have to look at that as well.

For this particular problem, the risk to the payload will be eliminated by not attaching it for the static fire. Any risk during the actual launch would still affect the payload, though.

Payloads are insured, most likely SpaceX itself takes most of the loss.

Insurance isn't magic money. The cost of the satellite is recouped through premiums charged to companies launching satellites. It becomes part of the cost of launching one way or another. If gain X has cost Y, Y still factors into the tradeoff even if it's insured.

To put it in concrete terms, if insurers decide that SpaceX is significantly more dangerous to its payloads, then launch insurance for satellites using SpaceX rockets will become significantly more expensive.

Not sure what you're getting at with the condescending tone. My point is that the satellite owner did not realize a $200m loss; SpaceX being at least partially self-insured, from what I've read, is more likely to take a hit. There were 85 launches in 2016, one rocket blowing up is not going to significant change the landscape (heh).

Disclaimer: I don't know shit about the space industry, so don't waste your time.

We're discussing the tradeoffs involved in making launches cheaper but more risky. My point here is that insurance is irrelevant to that tradeoff. One way or another, the payload owners are ultimately paying for that risk.

The insurer took the loss on the satellite, SpaceX took the loss on the vehicle/launch contract, and the pad equipment.

"small performance increase"

FT can get 30% more mass to LEO. That is a pretty big performance increase, especially considering that it enables SpaceX to carry the maximum payload of v1.1 in expendable configuration and still land the FT rocket. Even if we assume that half of that performance boost came from the other improvements, 15% is a significant increase.

That's the seductive side of design tradeoffs with rockets.

Shaving just a little weight (especially on the 2nd stage) or squeezing out just a little more performance can have dramatic differences in mass to LEO.

The question is how much this will increase overall operational cost. Up until this year or so, it has seemed that SpaceX has been willing to compromise on performance to get lower overall operational cost and reliability.

I'm a bit worried that they've started to go the other way with some of the improvements they've made this year.

Following STS-51-L (i.e., the Space Shuttle flight on which Challenger exploded on ascent), the Space Shuttle fleet was grounded for a bit over two-and-a-half years. This is quick (OTOH, this is unmanned!).

After the Ariane 5 first-launch failure, it was well over a year before it flew again.

It disrupted the schedule for 3 months, not for "the better part of a year". Otherwise you are making a fair point (but SpaceX seem to believe that it is worth it and that they will iteratively fix all these issues without losing customer trust).

Huh, I was sure it was in June. Actually September 1st. I guess it just feels longer to me. Thanks for pointing that out.

This fault wasn't due to the introduction of supercooled LOX, though. They've been doing that for a while. The change here was to the tanking schedule so that it could better withstand a last-minute hold. As it stands, they're back to any hold during tanking leading to a launch scrub.

Once the redesigned tanks come in, it's likely that they'll go right back, because little holds aren't uncommon.

They'd been doing it for about nine months before this explosion. It wasn't the proximate cause, but it was a major change to the vehicle, one which is highly unusual in rocketry, and without that change, the proximate causes for the explosion wouldn't have happened. Without supercooled propellants, there wouldn't have been the need for faster tanking (because the fuel can just be at ambient temperature, and the LOX maintains temperature by boiling), and even if there were, the LOX wouldn't have been cold enough to solidify.

I find the whole idea of carbon fiber inside a pressurized LOX contain a bit risky. Also, what about all those reports that we're running out of helium? Is that credible threat to ongoing space flight?

The cost of the physical helium in rocketry is going to remain negligible for a long time. The total cost of materials in a modern rocket is something like 1/2 of a percent of the cost of a launch, and I'm confident saying Helium is a tiny fraction of that. It doesn't matter if it goes up in price by a few orders of magnitudes. We are also still producing it in large quantities (natural gas often contains a lot of helium, which we extract). Rocket's also use a tiny amount of helium percentage wise, simply because there are so few rocket launches.

However even if we did somehow run out of Helium entirely, once SpaceX switches to Methane fuel (as they plan to do for the ITS) they won't need it anymore. Currently it's used to pressurize the tanks, but Methane does that for itself. It would mean speeding up development of 'small' methane launch vehicles presumably, but that's it.

I imagine that there are other ways to accomplish the same goal, as well, such as using other noble gasses. Helium provides the best cost/benefit tradeoff but surely other approaches would be practical if helium becomes unavailable.

How would you pressurize the liquid oxygen needed for the methane to burn?

Per the other comment, no other noble gas has a low enough boiling point to remain a gas at LOX temperatures...

If you need to you can heat up the oxygen to increase it's volume until the pressure is correct. I forget the reason that it's easier to do with methane than oxygen but it's possible to do with oxygen too if you really need to. ULA's new ACES upper stage is planned to use autogenous pressurization for both it's oxygen and hydrogen tanks.

We're not really running out, it's just getting more expensive because the government doesn't regulate it's availability anymore since the strategic helium reserve was done away with. It won't be a big deal for (already expensive) rocketry. Buying helium balloons for your birthday will be pricey, though.

Um, no. We are in fact running out of helium. There's only a certain mount and nobody not even natural processes is making anymore in any significant quantity. And what we do have is rapidly being released into the atmosphere and escaping into space.

And given that the nearest natural source of helium is Jupiter, that is a little concerning.

You can extract helium from natural gas.

An estimated 54 billion cubic feet (1.5×109 m3) of helium was detected in Tanzania in 2016


Yes that is where all helium on earth comes from: trapped ground sources, often in natural gas and oil deposits. Alpha particles from the Earth's radioactive core propagate upwards and get trapped somewhere in the earths crust, where we find them. But it took hundreds of millions of years to create macroscopic amounts of helium, so once all the sources in the ground or tapped it's gone, on human timescales at least. And you can't recycle from the atmosphere because it escapes the Earth's gravity.

I'm pretty sure we could make more helium if we really needed it. Nuclear fusion produces helium as a waste, and I expect fusion to become widespread before we run out of natural sources of helium on Earth.

We already rely on nuclear reactors to get several elements that are used in radiotherapy. IIRC there was a major shortage of medical isotopes a few years ago when a Canadian reactor that used to supply most of them was shut down.

Of course, it will be expensive, so no more cheap helium balloons for our grandkids. For specialized applications, though, we can afford some artificial helium.

A big difference between radionuclides and helium is that radionuclides are only needed in a relatively "small" quantity (producable by fission). Nuclear fusion would create helium but in very small quantities. Having 1TWe of fusion reactors would only yield 5grams of helium/second. That is not much.

> And given that the nearest natural source of helium is Jupiter, that is a little concerning.

Sun is closer and produces helium all the time, but less practical to harvest it from.

The US government alone is in the process of disposing[1] 1 billion cubic meters of the stuff from it's strategic reserves dating to back when airships where a thing. That volume is equivalent to a cube 1km long on each side.

1. https://en.wikipedia.org/wiki/National_Helium_Reserve

And when it is gone?

New helium is generated by alpha decay, and it comes up in natural gas wells that happen to be located in areas with natural radioactivity.

Not much, though. A quick perusal of Wikipedia (buyer beware, etc.) indicates that about 3,000 tons of helium are generated per year through radioactive decay (that's all happening in assorted rocks throughout the Earth's crust, so much of it wouldn't be easy to recover, either) while current production rates are around 9,000 tons per year.

A natural gas well has 10s of millions of years of helium accumulation from its local area.

Right, which means that while it's renewable over geological timescales, it's more or less a fixed reserve in human timescales. Much like oil.

Avogadro's number is very big: 6e22.

It's even bigger than that: ~ 6e23.


Thank you.

los grandes avogadro's :)

I believe that it's very likely that SpaceX can recover the helium used during operation. The helium isn't expelled from the fuel tanks. Since the 1st stage returns, it could be recovered.

Its more of we are running out of cheap helium as the US has been selling off its massive stockpile and its nearly depleted.

How does the gas get into this void between liner and overwrap? I presume the liner is meant to be impermeable? Or is it only impermeable when properly backed with the overwrap?

The helium COPV is submerged in LO2, so it's the oxygen that's soaking into the wrapping. I think the failure is that the oxygen is soaking into the wrapping before the helium is fully pressurized, and then the metal container expands slightly and crushes the oxygen that soaked in between the metal vessel and the carbon wrapping.

To really be sure they got to the bottom of the issue and are not seeing an intermittent issue they should duplicate the failure, but it may not be possible to do this safely. I detect a little bit of hand waving around the source of ignition:

"breaking fibers or friction can ignite the oxygen in the overwrap"

I would like to see at least this ignition source duplicated.

Note that the company that used to produce COPVs for SpaceX had a large explosion during testing at their factory. Some testing now takes place on barges at sea, and the huge carbon-fiber tank for ITS was also tested at sea.

They have duplicated the failure at their test site, possibly a number of times. At least one was mentioned but there have been multiple explosions.

It doesn't specify whether the mechanism proposed to have caused this particular anomaly has been experimentally verified to be able to cause ignition but, even if it had, it would still not prove it was the mechanism that was at work in this particular instance.

Yes, proposing a theory and reproducing a result experimentally doesn't prove anything - but it is the basis of all science.

My point is that the wording "several credible causes for the COPV failure" does not imply they haven't experimentally verified that those causes can cause a COPV failure, which you seemed to imply.

Who says they didn't repro the failure?

I also found it a little surprising with so much involved that they didn't take the effort to reproduce the failure case, perhaps doing so on a smaller scale than a full vehicle launch if possible.

The problem is that accurately reproducing this failure case is very difficult. You need to replicate the thermal properties of the loading process and the tanks, at the same speed with the same amounts of propellant and helium, effectively meaning that you have to do it with a full-size tank, and with a large amount of pad equipment. This is all extremely dangerous and almost certainly will result, if successful, in the loss of the testing stand.

Ouch it looks like the Isreali company lost their previous satellite too after 4 yrs of being in space:


There is still no cause listed on Wikipedia.

> Industry experts described the total loss of contact with the satellite as a highly uncommon event.

This one was built by Russians for the first time. It looks like they went back to a domestic built one with SpaceX and it blew up. That's some bad luck :/


That's why insurance isn't the end-all/be-all.

They've got enough money out of insurance to build themselves a new satellite, the problem is that they need that satellite yesterday, not today.

On the other hand, SpaceX isn't living off poor blokes who were hoodwinked by a starry-eyed agent. Their customers are professionals with lawyers and accountants taking care of things, so I don't feel that SpaceX is particularly unethical.

Does anyone know if the public can watch when they launch at Vandenberg AFB Space Launch Complex. I have always wanted to do this but never sure if it is open to the public

Kinda. Read the details at r/spacex FAQ and the links there https://www.reddit.com/r/spacex/wiki/faq/watching#wiki_i.27m...

What is the primary purpose of using liquid helium in a Falcon 9?

A quick google search for `liquid helium rocket` introduced me to pressure-fed engines [1]. A pressure-fed engine uses liquid helium, and is a replacement for a turbopumps. Since the Falcon 9 uses turbopumps, I don't understand what the liquid helium is for.

If I had to guess, it sounds like a Falcon 9 has a pressure-fed engine AND a turbopump. On a car, that'd be kind of like using both a turbocharger and a supercharger, which sounds complicated.


It's not liquid helium, it's gaseous helium, which is why it is at such high pressures. It's primarily used as a pressurant for the liquid oxygen and rocket fuel (RP-1) tanks. Since liquid oxygen and RP-1 are being sucked out of the tanks at high speed by the engine turbopumps, it needs some low-density gas to fill the tanks so that they don't crumple from negative pressure.

Falcon-9 has no pressure-fed-only engines, all 10 engines are fed by turbopumps.

Gotcha. Thanks!

Not only is pressurized gas used to avoid the tanks from crumpling from negative pressure, they cannot sustain themselves without internal pressure.

This gas need to be as inert as possible, hence helium. Another noble gas could in theory be used, but I think price is the reason.

Not just price, but density is the reason. The next noble gas up is neon, which is quite scarce and more expensive than helium, and denser anyways. After that it's argon, which is cheap and plentiful, but about ten times denser, so it's not nearly as good as helium.

Nitrogen would be the obvious choice but it dissolves in liquid oxygen, making usage harder. Soyuz however does use nitrogen.

Gases at the same pressure and temperature have the same molecular density, so lowering molecular weight translates directly into lower total weight of pressurant gas needed.

Alternately, if the propellants allow, it's possible to use those in gaseous form for pressurization (by passing some of it through a heat exchanger). This increases the weight of pressurant gas wasted but it saves the weight of the Helium system, and the complexity, so ultimately it's a big win. Unfortunately, this doesn't work with kerosene so the Falcon 9 needs a Helium system.

Could they use oxygen gas for pressurization, since the helium tank in a Falcon 9 seems to be inside the liquid oxygen tank? Or would it be too dangerous?

You can use oxygen gas for pressurization of oxygen tanks, but it introduces a new set of problems, since you've got to get a stable pressure of oxygen gas inside a container with a huge volume of sub-cooled liquid oxygen, and you have to have a high-pressure tank in there anyways to pre-load pressurized oxygen gas, so that you can get it into the tank fast enough. Also it means you've got reactive oxygen gas all around, so you have to redesign things for that.

However, this kind of oxygen-gas pressurization is exactly what's planned for SpaceX's next-generation oxygen-methane rockets.

The Space Shuttle used autogenous pressurization for its main engines / external tank, and the Delta IV is eventually planned to do so as well. And as you mentioned SpaceX plans to use the same system with their next generation of rockets. It is tricky to get working correctly and requires a larger up front engineering effort, but the payoff in simplicity of operations is significant. Additionally, it provides gaseous propellants that can be used for other purposes, such as attitude control thrusters.

Yes, it's great if you can manage it. But helium is so pleasingly inert and cold, I can see why it's not always the choice.

Too dangerous, it's not a good idea to combine pressurized high temperature oxygen and kerosene. Also, I think the Oxygen would dissolve in the kerosene, which would complicate the combustion process and make it less predictable.

Even with a pump-fed engine you still need some minimum pressure at the turbopump inputs to keep the fuel flowing and burning smoothly.

variations in the density of fuel entering the combustion chamber lead to variations in thrust which can lead to pogo oscillations.

My question is:

1. How often does this happen?

2. Hoe many tests did SpaceX do before the first FT launch?

Considering that most rockets don't use supercooled fuels, I would expect insane tests (they can't rely on NASA's historical data).

All the well known rockets use cryogenic fuel at least in their ascent stages: Space Shuttle, Saturn V, Soyuz. They certainly can't rely solely on NASA's or Russia's data, but it will/has undoutably helped.

Cryogenic fuel is not the same is supercooled; supercooled is closer to freezing than to boiling

I've been trying to dig up the launch time. Does anyone know when that will be? Thanks.

https://www.reddit.com/r/spacex usually has the most up to date information. They are saying 10:28/18:28 (PST/GMT).

Does anyone else think the timing is kinda funny? Today, at least in the US, is probably the slowest news day of the year. Great time to unload anything unfavorable :)

Wouldn't you want to unload something unfavorable on a fast news day, where it would get buried by other, bigger news?

They are announcing that they are returning to flight. Hardly 'unfavorable'.

That's multiple complete losses now that have been caused by issues with COPVs. I remember reading some discussion on /r/spacex about SpaceX going with really aggressive COPV technologies to shave as much weight as possible, but they're definitely paying for it in reliability. Hopefully they can iron it out, and maybe they'll switch to less aggressive COPV designs soon?

The previous loss was, as far as they can tell, related to a strut that broke under strain and released an otherwise-fine COPV into the oxygen tank. As far as they can tell it didn't have anything to do with aggressive design, just a part failing under its rated strength.

I don't think it even failed under it's rated strength, it was that their supplier for the struts provided sub-par/faulty struts and they couldn't handle the pressure they were supposed to be rated for

That's what I meant. It was rated for a certain load, but there was a faulty strut in the batch, and it failed well under that rated load.

Isn't that what 'failed under its rated strength' means?

"Multiple complete losses" is quite a misleading statement, in my opinion.

It's been exactly two.


Unless the parent has edited their comment, I don't see any 'outrage' or need to 'calm down'...

Accusing someone of being misleading is unwarranted ad hominem. A better way for him to approach his comment would have been to simply say there were two such incidents, no comments on motives necessary.

It's true that the statement is likely to mislead. If I hear "multiple" I certainly think "more than two". No one said it was intentionally misleading...

The fact that it's misleading is simply a fact. It's only an ad hominem if they ascribe malicious intent, which they did not.

Multiple means more than one: https://www.merriam-webster.com/dictionary/multiple (see the first definition). It's not misleading when you describe an indefinite quantity as "multiple" when all you know about it is more than one.

Also, what phrasing would you have preferred? "More than one" is the most accurate and least subject to misinterpretation, but then of course you'd still say it's misleading if the answer turns out to be two. If I knew the exact number I would've just said it. The point of using indefinite quantifiers is to convey uncertainty, it is not to mislead.

> Also, what phrasing would you have preferred?


Always using exact numbers and never indefinite quantifiers requires a level of omniscience that none of us has.

My suspicion was that SpaceX was rushing to validate their carbon fiber tank plans, which is why they did it on stage 2 (process is lower scale and easier to experiment). Well, at least they failed fast. I made this prediction in a private twitter DM (yes, weaksauce, I should have been bolder with a public post) the day that Musk announced their plans for giant carbon fiber tanks, with no knowledge that the stage 2 tank was made of carbon fiber.


The Carbon-Overwrapped Pressure Vessels are quite different from the large-scale carbon fiber tanks they're building now. The new large tanks are designed to be able to contain large quantities of propellant at moderate pressures, possibly without a liner, while the COPVs are meant to contain pressurant gas at extremely high pressure, with a metal liner. SpaceX has been using COPVs to hold helium pressurant since the first Falcon 9 back in 2010. This is not a new technology. What is new is the large propellant tanks, which have not been done before at this scale, and have not been used in Falcon 9s at any point.

So no, you shouldn't have been bolder with a public post.

Are you confusing the small COPV helium tanks with the much larger metal LOX tank?

100% wrong. COPVs and carbon fiber tanks are entirely different beasts. In fact, if carbon fiber He tanks had been used instead of the COPV bottles this failure wouldn't have happened.

Could we link to something less intrinsically biased, such as a news report, and not SpaceX's press release? Here's one:


The release is SpaceX reporting on an investigation they themselves conducted. There probably aren't other sources besides SpaceX that are better equipped to report on an investigation conducted by SpaceX or to independently corroborate or dispute its findings; all we can do is take their word for it, biased or not. Indeed, that NYT article is mostly just a regurgitation of the release.

> There probably aren't other sources besides SpaceX that are better equipped to report on an investigation conducted by SpaceX

I disagree; SpaceX has a clear interest (and a well-established track record) of presenting things in a way that bolsters their image. Outside experts could provide critiques of the report: What represents bad luck, what is trivial, and what is a serious error; where is SpaceX being straightforward and where are they spinning things; where are the gaps, where are there alternative analyses of the same data, and what seems solid.

That is a big reason why journalism is important: It provides context and other voices.

That's all fine and good, but the only source NYTimes article you suggested is SpaceX, so you're not getting commentary from any outside experts. Instead, you are just getting quotes and paraphrases from this and previous SpaceX press releases.

It's just one article of many possibilities. Also, they still can contextualize info and filter out spin.

Incidentally, any time you post something that isn't fully saturated with the SpaceX Kool-Aid, you get a strong reaction. Look at all the comments and the downvoting over a pretty mundane detail and a common concern: Don't link to a press release. I didn't even criticize the Great and Powerful Wizard or his rocket ships.

To be clear, I don't care about the votes, but I think the overall response says more than the comments.

>downvoting over a pretty mundane detail and a common concern: Don't link to a press release.

I didn't downvote your comments but I can see why you got them: you provided an NYT article that wasted readers' time.

Yes, it's wise to be skeptical of "press releases" to avoid spin but your rigid adherence to avoid-press-releases-at-all-costs put you on autopilot and caused you to link an article that was worse than the press release.

Now, you think the downvotes are about disagreeing with your principles about press releases when it may just be downvotes about that specific NYT article that added no value.

Sure, when Apple makes a press release, readers would be better off skipping their corporate marketing fluff and look at the Ars Technica writeup that will be more critical. However, the NYT writeup of SpaceX's accident report isn't an analogous example value-added journalism. (The newswriter Kenneth Chang is not a rocket scientist and can't offer any expert counterweight to the press release.)

This comment attributes many things to my thinking that are the creation of the commenter, some of which are contradicted by what I wrote myself, such as:

> you think the downvotes are about disagreeing with your principles about press releases

You keep talking about hypothetical advantages of outside articles. But you linked to a specific article which provides none of those advantages. I don't think you're being downvoted for not being sufficiently reverent of SpaceX. You're being downvoted for making a bad recommendation and defending it with irrelevant points.

If this were the report about the Tesla autopilot crash, I would totally agree with you. In that instance, where the investigation was conducted by a government entity, linking to Tesla's release about the investigation would have been the wrong move, because the release would be spin on something that journalists, or we as readers, could assess for ourselves directly (the actual independent report), so there would be no reason to get it via Tesla's PR filter. In this instance, though, they are unfortunately one and the same. The data upon which they are basing their conclusions (the actual telemetry from their sensors, etc.) is not public. Nobody is as informed as they are about their results, so any cross examination of their results would be de facto incomplete. Note that NYT is fully aware of this, also: their article is not reporting on what happened during the explosion, it's reporting on what SpaceX says happened during the explosion, because that's all that can be done given publicly available information.

Journalism is important.

Journalism is not regurgitating press releases.

A journalist would have tried to find experts able to comment on the SpaceX release to reveal information that was obfuscated or omitted.

The NYT article you linked was not journalism. If you want to wave the "do not link to press releases" banner, do not link to press releases :D

Since outside experts didn't provide critiques of the report, what makes this article better?

If you linked to an article that provided such things, I'd see your argument. But you linked to something that just regurgitated the press release, and said it was better than the press release. If outside experts didn't provide critiques, the fact that they could is meaningless.

That article is just a summary/rewrite of SpaceX's press release, with some publicly available background information glued on. I don't see how linking to a recap of a press release would be better than linking to the press release directly.

To avoid redundancy, see this post:


I would agree with you if you had an article by a journalist who interviewed someone from the FAA who has read the report and provided any comments to contrast with the company's press release. But as other pointed out, your link is not that.

It's a fairly cynical take on journalism, but it seems like an article like that would be mostly "read SpaceX's press release and a few of their tweets, then summarize and paraphrase". If a not-very-well-known blogger did the same thing, we'd call it "blogspam".

What about these possibilities?:


The company's determination is the "primary source", even if it might be biased or added some marketing spin.

>> This "anomaly" caused hundreds of millions...

It also produced a large quantity of nonsense. WAPO kicked that off with speculation of "sabotage." [1] By the time that stuff had finished ricocheting around the echo chamber it was SPETSNAZ snipers. Today WAPO has finally grounded out it's "Russian's hacked the US power grid" fiction. [2]

[1] https://news.ycombinator.com/item?id=12617990 [2] https://yro.slashdot.org/story/16/12/31/1533245/washington-p...

It would be nice if Elon could take a few minutes and install some grown-up editors at his paper. It's turning into a tabloid.

* Oh dear, I've mixed up my celebrity billionaires... Yes, Elon would have to get Bezos to fix the paper.

Are you perhaps confusing Jeff Bezos with Elon Musk?


Mind that Bezos also has his own aerospace company -- Blue Origin -- so it'd in fact be in his interest to report negatively about SpaceX. (If you subscribe to the theory that he's personally interfering with WaPo's editorial choices, which I do not.)

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