SpaceX's Starship Mk1 just blew off its bulkhead in a pressurization accident(twitter.com)
twitter.com
SpaceX's Starship Mk1 just blew off its bulkhead in a pressurization accident
https://twitter.com/NASASpaceflight/status/1197265917589303296
259 comments
I must admit that Elon has done some fairly impressive things, and I respect his hustle and innovation.
With that said, the cult that surrounds his projects where people say things like "this is what success looks like" when a big metal thing blows up unexpectedly or robot car goes flying off an exit ramp is a never ending source of amusement.
With that said, the cult that surrounds his projects where people say things like "this is what success looks like" when a big metal thing blows up unexpectedly or robot car goes flying off an exit ramp is a never ending source of amusement.
Way to misquote GP to confirm your preexisting bias. I think the quote you're looking for is:
"So as manufacturing pathfinder, this is what success often looks like. "
If blowing up a prototype enables changes to the manufacturing process that prevent the same thing happening later with a live crew on board, then it's considered a success. It doesn't matter who the CEO of the company happens to be.
"So as manufacturing pathfinder, this is what success often looks like. "
If blowing up a prototype enables changes to the manufacturing process that prevent the same thing happening later with a live crew on board, then it's considered a success. It doesn't matter who the CEO of the company happens to be.
On the other hand, perfection looks like nothing ever blowing up while job always getting done.
That creates a very conservative mindset, unsuitable for innovation.
So if this prototype had not blown up you would now be complaining that SpaceX is not sufficiently innovative?
Personally, I feel no need to complain about SpaceX, whether they blow up rockets or not. They're powering a new golden age of rockets. There's no room in my worldview for complaining about SpaceX. You are free to waste your time asking people why they aren't complaining, of course.
Who is complaining about SpaceX? The point is challenging a particular confusion which seems prevalent round here.
Suppose SpaceX had used a very similar prototype, but some process or engineer had caught the fault. Few here would be taking the lack of an explosion as evidence that SpaceX are not innovative. Instead, if anything, they would be praising the superb processes in addition to the cool prototype.
So, there is always room to improve. The reaction to this essentially anodyne point here has been really interesting.
Suppose SpaceX had used a very similar prototype, but some process or engineer had caught the fault. Few here would be taking the lack of an explosion as evidence that SpaceX are not innovative. Instead, if anything, they would be praising the superb processes in addition to the cool prototype.
So, there is always room to improve. The reaction to this essentially anodyne point here has been really interesting.
Rockets always blow up, the question is just how quickly.
Does this ever happen?
No. See X15 accidents, crew capsule fire, 2 shuttle accidents. Those all involved loss of life. There are other accidents in the US and plenty in other countries too.
AFAIK nobody has built something like this before. To have it fail during an early test doesn't seem unusual.
AFAIK nobody has built something like this before. To have it fail during an early test doesn't seem unusual.
You never get the job done without blowing things up, in any field where you’re treading untrodden ground.
See also: Soyuz 1, Soyuz 11, Challenger, Columbia, Apollo 1 - and that’s purely spacecraft which have killed people, never mind the vast list of experimental aviation deaths.
Much better to blow up some prototypes than some humans.
See also: Soyuz 1, Soyuz 11, Challenger, Columbia, Apollo 1 - and that’s purely spacecraft which have killed people, never mind the vast list of experimental aviation deaths.
Much better to blow up some prototypes than some humans.
There is no such perfection in space. Never has been.
Can't have perfection without ever blowing up. If you can launch 1000kg with a design, could it launch 1100kg by reducing the mass of the rocket? How about 1200kg? But reducing the mass of the rocket leads to explosions. If you never exploded, then you never found out how light it could be. It could be lighter. If it could be lighter, it's not perfect.
[deleted]
The cult is funny indeed, but do mind that the giant SpaceX booster rockets exploded in giant balls of fire a LOT before they eventually (and reliably) landed like in a sci-fi movie, on land and on a moving boat. SpaceX has earned some benefit of the doubt.
I don't think the issue is that a prototype didn't function as desired, it's the re-framing of that event as a "success" that reeks of cult-like worship mentality.
When something doesn't behave as desired, it is a failure. You can learn from failure, that's how you get to success, but the failure itself is not a success.
When something doesn't behave as desired, it is a failure. You can learn from failure, that's how you get to success, but the failure itself is not a success.
I agree calling it a success is too rosy, but I think people are really thinking od this as progress, not a regression like the event itself would naively suggest, because the company relies on hardware failure to inform design improvements.
FWIW the “boat” is not moving. This is in contrast to Blue Origin’s reusable booster which will literally be landing on a moving boat.
What do you mean by "not moving"? The platform sat on the surface of an ocean. It's always moving.
What he means is that the boat is moving up and down but keeps a stationary latitude/longitude.
The rocket has static landing coordinates, and if the boat were to move a few meters to either side it would miss it.
The rocket has static landing coordinates, and if the boat were to move a few meters to either side it would miss it.
SpaceX is almost certainly using an ILS-type radio system for the final 100 meters, both on the boat and on land. GPS just isn't quite good enough, especially out on the ocean where there are no WAAS base stations to cover up GPS' flaws.
It’s nearly impossible to stay put in the sea where waves and swell are meters high. The boat actually does try to stand still, for which they developed their own positioning / thrust system, but the tolerance is something like 3m-6m with the rocket adjusting its path on the fly.
But there are definitely no “static coordinates”, it would have to move a lot more than a few meters for the rocket to miss, and it would be due to trajectory and fuel constraints rather than ability to maneuver.
But there are definitely no “static coordinates”, it would have to move a lot more than a few meters for the rocket to miss, and it would be due to trajectory and fuel constraints rather than ability to maneuver.
I would suggest the boat is always moving to be able to stay in the same place
I guess the parent comment was pointing out that this actually wasn't unexpected, it was one of the expected failure modes for the test and it happened.
I don't see any constructive reason to look at it negatively, failure is part of testing. We don't test to find success, we test to find failures so that we can get them out of our systems.
I don't see any constructive reason to look at it negatively, failure is part of testing. We don't test to find success, we test to find failures so that we can get them out of our systems.
Fine, so don't call it "success!". It's a step on the way to (possible) success, but the hypersensitivity isn't helping anyone.
The semantics these days. Trade "success" for "progress"....but then also replace "accident" with "test result". Works both ways, so does the hyper-sensitivity.
We are silly animals. Links I can't help but click on....comments I can't help to respond to. The algorithms are winning.
We are silly animals. Links I can't help but click on....comments I can't help to respond to. The algorithms are winning.
If my test were designed for failures, my test results expect it to fail, and it did, then I call it a success. Science is about testing what we think we know, measuring it and confirming it.
In a Chemistry Lab, I put two elements together to show off a little explosion to my students, if it did. It was a successful demonstration, if it didn't go according to plan, it was a failure. And we will be wondering why this didn't work.
The OP said it from his perspective of pathfinder. And I assume these results were expected. And if it didn't blew up and they did not understand why it didn't, it create more uncertainty and variables during real launch. And I am sure everyone would want to minimise of that happening.
I am not sure how hard this is to see thing from his perspective, I would agree if Elon calling it a success would be hyperbole, but the OP stated he is a pathfinder, and finding out failure is exactly his job.
In a Chemistry Lab, I put two elements together to show off a little explosion to my students, if it did. It was a successful demonstration, if it didn't go according to plan, it was a failure. And we will be wondering why this didn't work.
The OP said it from his perspective of pathfinder. And I assume these results were expected. And if it didn't blew up and they did not understand why it didn't, it create more uncertainty and variables during real launch. And I am sure everyone would want to minimise of that happening.
I am not sure how hard this is to see thing from his perspective, I would agree if Elon calling it a success would be hyperbole, but the OP stated he is a pathfinder, and finding out failure is exactly his job.
You sound like the one hypersensitive here...
[deleted]
Cult not withstanding, Elon has expressed on a few occasions how he's expected some rockets to blow up, and a few have. I've had the idea the past few years that he's felt he hasn't been pushing the envelope hard enough. Progress on Starship has been at an astonishing rate by anyone's measure.
I find it fascinating that we get to observe this all playing out in real time. You might agree.
I find it fascinating that we get to observe this all playing out in real time. You might agree.
>With that said, the cult that surrounds his projects where people say things like "this is what success looks like"
Experimental rocket/spacecraft (that's a fairly rapid prototype as far as rockets are concerned), made out of non-traditional material for rockets, fails one way yielding tons of data to do it better on the next version.
That's some modicum of success no matter how you slice it. Go plug 'rocket launch fail' or 'rocket explosion' or some such into YouTube and watch various rockets failing spectacularly on the launchpad both during development and carrying actual payloads and compare it to this failure at this stage of development.
I mean, look at stuff like Apollo 1. An electrical fire killed all of the crew during a test less roughly a month before launch. Starship is a very early prototype that probably yielded more actionable data than the Apollo 1 accident did.
Experimental rocket/spacecraft (that's a fairly rapid prototype as far as rockets are concerned), made out of non-traditional material for rockets, fails one way yielding tons of data to do it better on the next version.
That's some modicum of success no matter how you slice it. Go plug 'rocket launch fail' or 'rocket explosion' or some such into YouTube and watch various rockets failing spectacularly on the launchpad both during development and carrying actual payloads and compare it to this failure at this stage of development.
I mean, look at stuff like Apollo 1. An electrical fire killed all of the crew during a test less roughly a month before launch. Starship is a very early prototype that probably yielded more actionable data than the Apollo 1 accident did.
Or that Elon Musk and SpaceX are doing real engineering work and other engineers recognize it and try to explain it to those who don't recognize engineering methods and processes?
You're saying this to a community with the mantra, "move fast and break things."
celticninja(1)
Why would they be using hardened steel for a pressure vessel that has to deal with vibrations?
Also, someone on twitter said a horizontal weld failed. If this is true I'm surprised they didn't do two things: - tune their welding procedure by destructive testing with the same type of steel - and X-ray (or use another non-destructive method) the welds after assembly.
Welding (including more interesting metals) is my hobby so I had an opportunity to see that there a huge amount of knowledge in the field. There are routine testing procedures that ensure situations like this one don't happen.
Also, someone on twitter said a horizontal weld failed. If this is true I'm surprised they didn't do two things: - tune their welding procedure by destructive testing with the same type of steel - and X-ray (or use another non-destructive method) the welds after assembly.
Welding (including more interesting metals) is my hobby so I had an opportunity to see that there a huge amount of knowledge in the field. There are routine testing procedures that ensure situations like this one don't happen.
Maybe they did both things, and the weld still failed. The rocket's being engineered, which means they make it as weak as possible without it blowing up. Those welds might be perfect in the x-rays, they might've done all sorts of destructive analysis, and still the thing might fail in staging.
Of course, they might also be on a deadline, and just went ahead and built it to spec and test it. But I don't think you can just say there's routine testing procedures that ensure rockets never blow up. If that were the case we wouldn't have needed SpaceX to reinvigorate the space industry.
Of course, they might also be on a deadline, and just went ahead and built it to spec and test it. But I don't think you can just say there's routine testing procedures that ensure rockets never blow up. If that were the case we wouldn't have needed SpaceX to reinvigorate the space industry.
>Maybe they did both things, and the weld still failed. The rocket's being engineered, which means they make it as weak as possible without it blowing up. Those welds might be perfect in the x-rays, they might've done all sorts of destructive analysis, and still the thing might fail in staging.
Yes, that is also a possibility. I'm not sure how likely is it that a pressure vessel would fail along a weld if that weld was without faults and as strong as other surfaces. Perhaps it matters that there is also a sharp corner there?
>Of course, they might also be on a deadline, and just went ahead and built it to spec and test it. But I don't think you can just say there's routine testing procedures that ensure rockets never blow up.
I agree if they are trying to make it as light as possible and pushing the boundaries a bit while experimenting. One can't innovate without risk.
It would be good if they released more info about this incident.
Yes, that is also a possibility. I'm not sure how likely is it that a pressure vessel would fail along a weld if that weld was without faults and as strong as other surfaces. Perhaps it matters that there is also a sharp corner there?
>Of course, they might also be on a deadline, and just went ahead and built it to spec and test it. But I don't think you can just say there's routine testing procedures that ensure rockets never blow up.
I agree if they are trying to make it as light as possible and pushing the boundaries a bit while experimenting. One can't innovate without risk.
It would be good if they released more info about this incident.
AFAIK, during early development they are using a different, simpler welding process, including more welds and thicker off-the-shelf steel plates to compensate strength.
The welding process probably isn't optimized or fully inspected and the weakest parts would expectedly be the welds.
The welding process probably isn't optimized or fully inspected and the weakest parts would expectedly be the welds.
As far as I know the type of steel they are using increases in strength as it gets colder, so that should be ideal for the LOX.
They are using 301 stainless which, as far as I know, cannot be hardened.
What does pathfinder mean in the context of manufacturing?
A fuzzball of patches and “good ideas at the time”. It’s like the first iteration of an app that never sees the light of day, as you finish, sit back, go “ah, an abomination”, and rewrite the thing properly with what you learned from the prototype.
I do this pretty much any time I’m doing something new - I have three revisions of a solar panel stand sat out on the lawn right now, each better than the last, as I needed to build the thing to see how it actually held up to forces as it’s easier and more accurate (ah, how do I fit a screwdriver in this gap to fasten this?) than doing an engineering simulation.
I do this pretty much any time I’m doing something new - I have three revisions of a solar panel stand sat out on the lawn right now, each better than the last, as I needed to build the thing to see how it actually held up to forces as it’s easier and more accurate (ah, how do I fit a screwdriver in this gap to fasten this?) than doing an engineering simulation.
At the highest level, the conversation looks like:
The design engineer: "We know on paper how the product needs to function in terms of strength, weight, durability, etc"
The manufacturing engineer: "We've never made something like this before. I've got a couple ideas how we can bend/shape/form/machine/weld these materials into the shape, but I don't know how those bend/shape/form/machine/welding operations are going to affect the underlying physical properties of the material. I know on paper these operations should be OK, and we can inspect them as we go, but again we've never done them before, we most likely will overlook something or discovery something new, so let's try one of them and break it early before we get too far down a potentially bad path."
The test engineer: "Well it worked up until X point then failed, here's the data for you design engineer and you manufacturing engineer, better try something else".
Design engineer: "Shoot, what we thought we were manufacturing isn't actually what got manufactured. Hmmm, is it even possible to make the part we need? Or do we now need to redesign the part because it can't actually be made. Let's try another approach. And maybe it's smart to pursue a few of these in parallel to increase our overall chance of success"
Those 3 roles can be the same person or separate organizations of hundreds/thousands of people. Requirements documents, manufacturing/quality reports, test reports, inspection reports are the language of this technical interchange.
The design engineer: "We know on paper how the product needs to function in terms of strength, weight, durability, etc"
The manufacturing engineer: "We've never made something like this before. I've got a couple ideas how we can bend/shape/form/machine/weld these materials into the shape, but I don't know how those bend/shape/form/machine/welding operations are going to affect the underlying physical properties of the material. I know on paper these operations should be OK, and we can inspect them as we go, but again we've never done them before, we most likely will overlook something or discovery something new, so let's try one of them and break it early before we get too far down a potentially bad path."
The test engineer: "Well it worked up until X point then failed, here's the data for you design engineer and you manufacturing engineer, better try something else".
Design engineer: "Shoot, what we thought we were manufacturing isn't actually what got manufactured. Hmmm, is it even possible to make the part we need? Or do we now need to redesign the part because it can't actually be made. Let's try another approach. And maybe it's smart to pursue a few of these in parallel to increase our overall chance of success"
Those 3 roles can be the same person or separate organizations of hundreds/thousands of people. Requirements documents, manufacturing/quality reports, test reports, inspection reports are the language of this technical interchange.
Essentially doing something for the first time, no one has built a steel structure of this size before, that will have to withstand the forces that this will be out through in normal operation.
Tabu search thru a semi-dynamic design space.
https://en.wikipedia.org/wiki/Tabu_search
https://en.wikipedia.org/wiki/Tabu_search
Soumds similar to tracer bullet development.
"You will learn more from your failures than your successes - so embrace those mistakes, as difficult as that sounds, and grow from them. When a project is successful, you're never really sure why, because so many elements come into play. However, when you fail, you always know why. That is how you learn and grow."
Lynda Resnick
Lynda Resnick
Oh dear! It looks like someone accidentally divided by 2 for the cylindrical hoop stresses, forgetting that they're not the same equation as for spherical stresses. :)
Less facetiously, a thin-walled cylinder's stress is a function of pressure, radius and thickness with the equation:
sigma = P*r/t
whereas for a sphere (including the spherical end caps on a cylindrical pressure vessel), it follows the equation:
sigma = Pr/(2t)
To me, it looked like it failed around the join between the spherical end cap and the cylindrical body, where this transition between stress regimes occurs, which is a common weak spot in the above analysis. This is a canonical early engineering statics problem.
It's worth noting, though, that all of the above is almost certainly a gross simplification and likely has very little bearing on the actual problem. It's fun to simplify and hypothesise, though! Also, unplanned failures make for great viewing :)
Less facetiously, a thin-walled cylinder's stress is a function of pressure, radius and thickness with the equation:
sigma = P*r/t
whereas for a sphere (including the spherical end caps on a cylindrical pressure vessel), it follows the equation:
sigma = Pr/(2t)
To me, it looked like it failed around the join between the spherical end cap and the cylindrical body, where this transition between stress regimes occurs, which is a common weak spot in the above analysis. This is a canonical early engineering statics problem.
It's worth noting, though, that all of the above is almost certainly a gross simplification and likely has very little bearing on the actual problem. It's fun to simplify and hypothesise, though! Also, unplanned failures make for great viewing :)
That's why you take your maximum design stress and double it, right? /s
I don't know what happened here, but if I remember correctly, in rockets, safety factor is typically smaller than 2 or the design would be too heavy. But I guess the safety factor for pressure testing is 4.
Source: article 6.8.2.2 of this document; https://www.faa.gov/about/office_org/headquarters_offices/as...
Edit: I didn't see the "/s" before writing this comment.
Source: article 6.8.2.2 of this document; https://www.faa.gov/about/office_org/headquarters_offices/as...
Edit: I didn't see the "/s" before writing this comment.
> in rockets, safety factor is typically smaller than 2 or the design would be too heavy
Safety factors feel like p-values. Why .05? Because. What if it's not good enough? We'll move the goal post.
Safety factors feel like p-values. Why .05? Because. What if it's not good enough? We'll move the goal post.
They are, somewhat. You can theoretically make a safety factor 1.0 if you're really absolutely certain of the input criteria.
Safety factor is really just a (somewhat blunt) method of managing risk. It's just admitting that we don't know the true load spectra that a design is exposed to, so we take what we believe is the max load and then slap a multiplier on it to manage how much uncertainty we expect, be it from estimates of that load, or dynamic factors, etc. etc.
We then also consider the consequence (since risk = likelihood x consequence). If the consequence of a failure is that our balsa-wood model bridge falls over, we shrug and keep it low. If it's that our pressure vessel undergoese a BLEVE [1] in the middle of a population centre then you jack it right the hell up.
There's nothing that specifically requires a safety factor. We could spend millions of dollars and thousands of hours understanding exactly the load spectra a design experiences, but that may be prohibitively expensive in the case of designing a bridge, so we instead accommodate more risk by overdesigning the item. In a space application where every kg of launch mass represents big $$$, then spending that extra time and money to understand the load specifics in more detail makes sense.
[1]: https://en.wikipedia.org/wiki/BLEVE
Safety factor is really just a (somewhat blunt) method of managing risk. It's just admitting that we don't know the true load spectra that a design is exposed to, so we take what we believe is the max load and then slap a multiplier on it to manage how much uncertainty we expect, be it from estimates of that load, or dynamic factors, etc. etc.
We then also consider the consequence (since risk = likelihood x consequence). If the consequence of a failure is that our balsa-wood model bridge falls over, we shrug and keep it low. If it's that our pressure vessel undergoese a BLEVE [1] in the middle of a population centre then you jack it right the hell up.
There's nothing that specifically requires a safety factor. We could spend millions of dollars and thousands of hours understanding exactly the load spectra a design experiences, but that may be prohibitively expensive in the case of designing a bridge, so we instead accommodate more risk by overdesigning the item. In a space application where every kg of launch mass represents big $$$, then spending that extra time and money to understand the load specifics in more detail makes sense.
[1]: https://en.wikipedia.org/wiki/BLEVE
Safety factors also mitigate stupidity (your bridge is rated for load X, but someone drives 1.1 X through it because they're in a hurry) and cascade failures (a component upstream of yours fails and sends more load down your way).
Those both sound like kinds of ways the real maximum load could be higher than what you've called your maximum load
Only as long as your "real maximum load" != "announced maximum load". For the type of stupidity mitigation I mentioned, you want the real maximum load to be greater than the max load you announce to the customer/users. For mitigating cascade failures, you want the real maximum load to be greater than the maximum load value meant to be used internally by people designing other components in the system (though here, a smarter way would be to do a system-wide analysis of load flows to prevent cascade failures under user stupidity; however, here we're rapidly approaching the point at which I just talk out of my ass, having no real expertise on the topic).
There's also some benefit in throwing a moderate safety factor on something if it doesn't actually compromise the intended form or function of the component, just as future insurance. For example, if you design a bit of equipment to take a certain load, but there's no size or mass constraints on it, and you can throw a 1.5x safety factor on, then it's not necessarily a bad thing. Even if your 'true' load as measured over several years of service only ends up being 1.2x, then the extra 0.3 or so can come in useful if a future engineer has to make modifications to the function of the device, or if they are asked to evaluate a life extension, etc.
In less words, I'm eternally thankful that I work in an era where much of the older equipment I used was designed in an era of slide rule. This means there's a bit of extra 'meat' in the designs which often means that when I do a more precise computational analysis, I can deal with 10% material loss through corrosion, or extend out the life by some period of time because it's not been designed precisely to the material limits.
In less words, I'm eternally thankful that I work in an era where much of the older equipment I used was designed in an era of slide rule. This means there's a bit of extra 'meat' in the designs which often means that when I do a more precise computational analysis, I can deal with 10% material loss through corrosion, or extend out the life by some period of time because it's not been designed precisely to the material limits.
> I'm eternally thankful that I work in an era where much of the older equipment I used was designed in an era of slide rule.
Yes, I feel this way too. The knowledge and tooling of modern engineers is amazing, and can do miracles when applied to tasks that seemed impossible just a century ago. But more often than not, it's used to pinch pennies from old designs. This makes me wish for infrastructure projects to be forced to be designed with slide rules again - the less precise your determination of maximum load is, the less the beancounters can "optimize" it.
This is doubly sad in our era, where matter is cheap and labor is expensive - adding extra safety margin can be almost free, but it's an easy target for cost reduction.
Yes, I feel this way too. The knowledge and tooling of modern engineers is amazing, and can do miracles when applied to tasks that seemed impossible just a century ago. But more often than not, it's used to pinch pennies from old designs. This makes me wish for infrastructure projects to be forced to be designed with slide rules again - the less precise your determination of maximum load is, the less the beancounters can "optimize" it.
This is doubly sad in our era, where matter is cheap and labor is expensive - adding extra safety margin can be almost free, but it's an easy target for cost reduction.
This is getting into the "really absolutely certain of the input criteria" category your initial parent was talking about
It's more like a re-usability factor in mechanical design. Higher safety factor tends to equal fewer cracked welds down the road in anything exposed to vibration and shock. I've only ever heard of one lifting fixture weldment that used a safety factor of 1.0. Every single welded joint was taped instead of painted, and peeled off and fully mag particle tested between each use.
Keep in mind that weld strength is not one single number, it is a wide range. You can inspect a weld with X-ray, UT, MT, and PT methods to narrow the range, but there are still variable heat input, soluble hydrogen content, pre-heat and post-weld heat treatment factors that ALL affect the final hardness/brittleness and ultimate strength of a welded fabrication.
Keep in mind that weld strength is not one single number, it is a wide range. You can inspect a weld with X-ray, UT, MT, and PT methods to narrow the range, but there are still variable heat input, soluble hydrogen content, pre-heat and post-weld heat treatment factors that ALL affect the final hardness/brittleness and ultimate strength of a welded fabrication.
Note that p<0.05 isn't the arbitrary threshold for something to be true, it's the threshold for something to be interesting. If your p-values are greater than 0.05, you're wasting your peers' time trying to show off your work.
Typically the factor of safety is not that high in the aerospace industry.
How else do you think I keep my reputation as a miracle worker? -- Scotty
"The tank can't handle that much pressure."
"Where'd you get that idea?"
"What do you mean, where did I get that idea? It's in the impulse engine specifications."
"Regulations 42/15: 'Pressure Variances in IRC Tank Storage'?"
"Yeah."
"Forget it. I wrote it… A good engineer is always a wee bit conservative, at least on paper."
- La Forge and Scott, Star Trek TNG "Relics"
"Where'd you get that idea?"
"What do you mean, where did I get that idea? It's in the impulse engine specifications."
"Regulations 42/15: 'Pressure Variances in IRC Tank Storage'?"
"Yeah."
"Forget it. I wrote it… A good engineer is always a wee bit conservative, at least on paper."
- La Forge and Scott, Star Trek TNG "Relics"
It's been a while since I did pressure vessels but it's usually 2.5 times for proof and 3.5 for burst. Then with added safety you usually need about 4x to actually see a "planned" failure. This is most likely a construction fault.
They left the nose cone off to save money. I wonder if the designer counted on some portion of the cone weight to support the cylinder head in their design?
I'm fairly sure SpaceX's engineers know 1st year mechanics.
[deleted]
I know that SpaceX is trying to make space flight cheap so they have to figure out how to do things like use cheap pressure vessels but this mode of failure is exactly why aerospace pressure vessels have long been made from a hot rolled body (as opposed to cold worked and welded).
https://www.youtube.com/watch?v=MvADC43EHmE
https://www.youtube.com/watch?v=MvADC43EHmE
And that's why they are testing it.
Depends on what kind of test that was supposed to be.
If they pumped it until it explodes it would be a kind of test (also called experiment) where it makes sense.
If you design something with a margin of safety, then pump it to working pressure and it blows, then it means you made a mistake. If you made a mistake it shows you don't know what is necessary to design a rocket (yet).
Seriously, they don't build skyscrapers or bridges and leave for 5 days to see if they topple to prove the design was correct.
If they pumped it until it explodes it would be a kind of test (also called experiment) where it makes sense.
If you design something with a margin of safety, then pump it to working pressure and it blows, then it means you made a mistake. If you made a mistake it shows you don't know what is necessary to design a rocket (yet).
Seriously, they don't build skyscrapers or bridges and leave for 5 days to see if they topple to prove the design was correct.
> If you made a mistake it shows you don't know what is necessary to design a rocket (yet).
Yeah, sure SpaceX doesn't know what's necessary to design a rocket.
Yeah, sure SpaceX doesn't know what's necessary to design a rocket.
Rockets are designed to have a vastly lower margin of safety. If they never fail in testing that’s a sign you’re over engineering it and sacrificing cargo capacity, which is a bad thing. That said, these failures should be uncommon.
Starship needs to be reusable dozens of times, with no refit between launches (only refueling). Fuel is cheap; the vehicle needs to survive. It also needs to be reliable enough to carry people. They're not using razor-thin safety margins on it.
Fuel is not cheap. Fuel is heavy and payload reduction is money lost.
Fuel is very cheap. SpaceX has built their whole business around the idea that it's worth trading payload for re-usability.
SpaceX has built part of their business around the idea that it's worth trading a moderate amount of payload for re-usability as long as they can still reach the orbit their customers care about and it was considered an extremely risky bet before they made it routine.
It doesn't make fuel cheap, let alone very cheap.
Actually another significant part of SpaceX business is modern engineering and modern mean of production. They used to launch without recoverability for some high orbit payloads and they were competitively priced for that too.
It doesn't make fuel cheap, let alone very cheap.
Actually another significant part of SpaceX business is modern engineering and modern mean of production. They used to launch without recoverability for some high orbit payloads and they were competitively priced for that too.
Musk has said the cost of the methane for one Starship/Super Heavy launch will be about $1 million.
Fuel is cheap on a monetary basis.
_Lifting_ that fuel is NOT CHEAP. See also, the rocket equation.
_Lifting_ that fuel is NOT CHEAP. See also, the rocket equation.
But the primary cost of lifting fuel (if you have a reusable rocket) is fuel. Leaving us back at cheap.
But we're essentially arguing whether max payload per launch or payload efficiency to orbit is more important.
But we're essentially arguing whether max payload per launch or payload efficiency to orbit is more important.
With exponential compounding, I wouldn’t be so sure that it’s still cheap…
Yeah, and with much higher required dv and more required stages this would be a huge problem. But we only need two stages to orbit when launching from Earth, so it's really not that big of a deal, and it turns out that optimizing for reusability ends up being a lot cheaper than optimizing for minimum fuel use. For example, it only costs $200k for a fuel load of Falcon 9 fuel. If you got rid of reusability you'd need less fuel and could save tens of thousands of dollars ... but at the cost of needing to build a new $54M spacecraft with each launch. Clearly that trade-off isn't worth it.
So yes, fuel is cheap.
So yes, fuel is cheap.
Fuel becomes more expensive on reusable spacecraft. Granted, the first pound of fuel is cheap, but the costs keep rising.
With one and done you have a larger mass fraction to work with. Reusable spacecraft operate on much tighter constraints. Every single wasted pound in Space X’s design likely costs them 100’s of thousands of dollars in lost profit over time.
With one and done you have a larger mass fraction to work with. Reusable spacecraft operate on much tighter constraints. Every single wasted pound in Space X’s design likely costs them 100’s of thousands of dollars in lost profit over time.
Not sure what’s to disagree with about that: “The reusable Falcon 9’s performance to GTO is listed at 5,500 kilograms. The same rocket in fully expendable version can lift 50 percent more payload — 8,300 kilograms. For the Falcon Heavy, the performance to GEO is about 2.8x that of the reusable version” https://spacenews.com/spacexs-new-price-chart-illustrates-pe...
Reusable means cost savings, but it has a dramatic reduction in cargo capacity. This means more trips to get the same mass into orbit, which means mire fuel directly used and every extra lb in the design is then carried up multiple times while further requiring more trips.
Reusable means cost savings, but it has a dramatic reduction in cargo capacity. This means more trips to get the same mass into orbit, which means mire fuel directly used and every extra lb in the design is then carried up multiple times while further requiring more trips.
Speaking relatively here.. spaceships are still more expensive.
Fuel is cheap. Spaceships are not.
That's basically been the conventional thinking about rocketry historically - scientists and engineers looked at the tyranny of the rocket equation and choose to maximize payload per launch because they were largely funded by government or quasi government "cost plus" types of contracts. The design philosophy of working close to margins comes from this thinking.
SpaceX's greatest contribution has been to look at rocketry from the point of view of economics of running a rocket launching business as opposed to a "per launch cost plus" model realizing that fuel cost for launching a rocket is close to trivial compared to the facrication cost of making a rocket.
So their entire design philosophy is around reusability and reusability seems to push costs down low enough that you can get more payload up by simply doing more launches. While SpaceX is famous for not filing patents and instead protecting their IP using the trade secret approach and fabricating everything in-house, you can bet they'll be operating with more engineering headroom to get reliability and reusability.
Evidence for their bet having been right is the fact that they have grabbed virtually 100% of commercial and quasi-governmental launches and some part of US government launches. Other players in this space now almost entirely depend on defence contracts or national prestige contracts to survive.
SpaceX's greatest contribution has been to look at rocketry from the point of view of economics of running a rocket launching business as opposed to a "per launch cost plus" model realizing that fuel cost for launching a rocket is close to trivial compared to the facrication cost of making a rocket.
So their entire design philosophy is around reusability and reusability seems to push costs down low enough that you can get more payload up by simply doing more launches. While SpaceX is famous for not filing patents and instead protecting their IP using the trade secret approach and fabricating everything in-house, you can bet they'll be operating with more engineering headroom to get reliability and reusability.
Evidence for their bet having been right is the fact that they have grabbed virtually 100% of commercial and quasi-governmental launches and some part of US government launches. Other players in this space now almost entirely depend on defence contracts or national prestige contracts to survive.
Doesn't matter. If you take the conservative assumptions that go into manufacturing, say, a car and apply those to a rocket, you'll get something that won't even lift off the ground, much less make orbit.
Any rocket HAS to be very close to the limits of what materials used allow, and not the +50% margin of error you routinely seen in other fields. What you say about SpaceX is true, but only relative to the rocket industry as a whole. E.g. SpaceX uses cheap, available materials and simple designs over exotic composites and complex mechanisms. But they still operate close to the margins, as they have to in order to have any payload capacity at all. In fact, the move to steel probably reduced their mass margins even further.
EDIT: Actually maybe I shouldn't have used a car as an example: https://www.youtube.com/watch?v=pJdrlWR-yFM
Any rocket HAS to be very close to the limits of what materials used allow, and not the +50% margin of error you routinely seen in other fields. What you say about SpaceX is true, but only relative to the rocket industry as a whole. E.g. SpaceX uses cheap, available materials and simple designs over exotic composites and complex mechanisms. But they still operate close to the margins, as they have to in order to have any payload capacity at all. In fact, the move to steel probably reduced their mass margins even further.
EDIT: Actually maybe I shouldn't have used a car as an example: https://www.youtube.com/watch?v=pJdrlWR-yFM
I think SpaceX has proven they know how to design rockets. But they are newcomers to building rockets from welded steel.
It is my understanding that the pressure vessels are carbon fiber composites. The skin is steel.
The skin is the pressure vessel, double walls are a waste of valuable mass.
They gave up on carbon fiber awhile ago.
*I think they still use small composite overwrapped pressure vessels for fluids they need less of than CH4 and O2, just referring to giving up on carbon for the main tanks.
They gave up on carbon fiber awhile ago.
*I think they still use small composite overwrapped pressure vessels for fluids they need less of than CH4 and O2, just referring to giving up on carbon for the main tanks.
https://everydayastronaut.com/stainless-steel-starship/
Edit: "So in summary. SpaceX chose stainless steel over carbon composites because it’s about as light, it can handle higher temperatures which means less heat shield is need, which then makes it lighter, it reflects heat which means even less heat shield which again makes it even lighter, it’ll be cheaper and quicker to build AND it’ll look FREAKING AWESOME."
Edit: "So in summary. SpaceX chose stainless steel over carbon composites because it’s about as light, it can handle higher temperatures which means less heat shield is need, which then makes it lighter, it reflects heat which means even less heat shield which again makes it even lighter, it’ll be cheaper and quicker to build AND it’ll look FREAKING AWESOME."
Do you have a source?
My understanding is that the skin is the pressure vessel. The reason for going with stainless steel at all is because it maintains integrity at high temperature. Carbon fiber does not. So a stainless steel combined heatsink and structure can maintain integrity at 1000C or whatever, while carbon fiber+ceramic heatshield will need to hold temperatures below 400C or whatever.
And even though the fiber structure is much, much lighter, the amount of heat protection required is massive. And the stainless steel "cheats" by performing double duty. And you get a second free lunch because the heat protection requirements are slimmer.
It wouldn't be the first time I've been wrong today though. Nor the second.
My understanding is that the skin is the pressure vessel. The reason for going with stainless steel at all is because it maintains integrity at high temperature. Carbon fiber does not. So a stainless steel combined heatsink and structure can maintain integrity at 1000C or whatever, while carbon fiber+ceramic heatshield will need to hold temperatures below 400C or whatever.
And even though the fiber structure is much, much lighter, the amount of heat protection required is massive. And the stainless steel "cheats" by performing double duty. And you get a second free lunch because the heat protection requirements are slimmer.
It wouldn't be the first time I've been wrong today though. Nor the second.
Apparently I have not been following this as closely as I thought I was. This 12 meter diameter tank is from 2016. Not part of current design.
https://everydayastronaut.com/stainless-steel-starship/
https://everydayastronaut.com/stainless-steel-starship/
> But they are newcomers to building rockets from welded steel.
AFAIK everybody is.
AFAIK everybody is.
Atlas was steel. The first US ICBM and an early space launch vehicle.
To this day, the Centaur hydrogen upper stage with RL10 engine is steel. Balloon tanks. They inspired SpaceX heavily.
This and the Mk2 prototype in Florida are mostly experiments with manufacturing processes; I would not be surprised if there were a reliability problem with their methods that weakened the product.
Skyscrapers have been built again and again, and they have much different constraints. Starship Mk1 is the first of its kind.
I expect this was more likely a manufacturing mistake. It was assembled night and day under a very tight deadline.
> Seriously, they don't build skyscrapers or bridges and leave for 5 days to see if they topple to prove the design was correct.
Perhaps a better analogy is carving a violin top. Skyscrapers and bridges can be overbuilt without destroying their utility, but a violin has to be as thin as possible without breaking if you want it to function well as a violin.
Perhaps a better analogy is carving a violin top. Skyscrapers and bridges can be overbuilt without destroying their utility, but a violin has to be as thin as possible without breaking if you want it to function well as a violin.
Boeing intentionally snaps of the wings of prototype aircraft to find the breaking point/prove the margin of stress.
No, they don't. They load it to 150% of max design load. Sometimes they keep bending it until it snaps (777) and sometimes they don't (787 - no one wants to clean carbon fibre mess). Sometimes it snaps before it's reached and it's ok (airbus a380).
At least the pump is working and generating pressure.
Seems like the difference between unit tests and integration tests.
Yea, there is something about all the attention on this thing that stresses me out. Its a prototype, right? There is going to be things that appear bad, but its really just a treasure chest of data.
It depends on whether or not there was a reasonable expectation that the test was going to result in a failure.
Suppose you bought a used car, and the brakes failed before you could drive it off the dealer's lot. The dealer graciously fixes the problem, and points out the great news - that nothing catastrophic happened, and that the problem is now fixed!
You would, of course, start wondering - what other unexpected failures are going to take place, after you drive out of the dealership. Maybe nothing. Maybe something life-threatening.
If the failure was a surprise for everyone involved, I'd be worried - because other surprises might not get caught in testing. If it was a 'Well, we're not sure what would happen', I'd be less worried.
Suppose you bought a used car, and the brakes failed before you could drive it off the dealer's lot. The dealer graciously fixes the problem, and points out the great news - that nothing catastrophic happened, and that the problem is now fixed!
You would, of course, start wondering - what other unexpected failures are going to take place, after you drive out of the dealership. Maybe nothing. Maybe something life-threatening.
If the failure was a surprise for everyone involved, I'd be worried - because other surprises might not get caught in testing. If it was a 'Well, we're not sure what would happen', I'd be less worried.
That’s one way to get the neighbors to move!
Also, by paying the neighbors 3x their property value to buy out their homes.
Yeah I know ... my comment was in jest ....but note the dateline below was yesterday...<raised eyebrow>
https://www.krgv.com/news/spacex-extends-buyout-offer-deadli...
https://www.krgv.com/news/spacex-extends-buyout-offer-deadli...
This twitter reply sums it up well:
“SUCCESS! We now now max pressure the tank can hold and the damage a rupture might do.”
“SUCCESS! We now now max pressure the tank can hold and the damage a rupture might do.”
Well, we know max pressure THAT PARTICULAR TANK could hold.
Don't get too excited about the damage, in space it does not matter much, the crew is screwed anyway.
Don't get too excited about the damage, in space it does not matter much, the crew is screwed anyway.
Good news, everyone!
Ah so this wasn't an accident? They needed to know the pressure limits so they purposely blew the bulkhead?
It clearly was an accident, why would they put 3 rocket engines in it if they were going to stress test the tank?
Unlikely.
But they have learned to be more careful with the welds going forward. Though, admittedly, they only used panel welding on the first prototype and have already switched it up for the second one.
But they have learned to be more careful with the welds going forward. Though, admittedly, they only used panel welding on the first prototype and have already switched it up for the second one.
[deleted]
Yup, curious to see the analysis of this failure when/if it's available. Failures like this often provide a great view into the difficulties of aerospace manufacturing and testing along the entire supply chain.
I mean, sure, but they certainly wanted to get more data out of it than they did. This is a setback.
They are supposed to begin personal cross continental flights on this thing in just a few years for a bit more than the cost of an economy coach plane ticket.
A bit before that it is supposed to do a manned moon flyby in 2023.
A bit before that it is supposed to do a manned moon flyby in 2023.
Sources:
New York to Shanghai slightly more than economy ticket by 4/2028:
https://www.vox.com/2018/4/11/17227036/flight-spacex-gwynne-...
Moon 2023:
https://www.scientificamerican.com/article/spacex-plans-to-f...
New York to Shanghai slightly more than economy ticket by 4/2028:
https://www.vox.com/2018/4/11/17227036/flight-spacex-gwynne-...
Moon 2023:
https://www.scientificamerican.com/article/spacex-plans-to-f...
It's amazing they know the exact month already.
Is the Starship Mk1 more structurally sound than it looks? From a first glance and having no knowledge of its design, it looks like an empty soda can that would deform at the slightest disturbance. And the way it crumpled in the video doesn't seem far off from what I would expect.
You're actually spot on. For example the Space Shuttle main tank had a 96:4 contents:structure ratio[0]. A soda can is 94:6.
[0] https://www.nasa.gov/mission_pages/station/expeditions/exped...
[0] https://www.nasa.gov/mission_pages/station/expeditions/exped...
How does that compare to commercial airplanes?
I'm guessing something in the 3:2 range on payload to structure ratio.
Yes, rockets are basically soda cans full of propellant with rocket engines on the bottom and the payload usually on the top.
They are entirely constrained by thrust versus mass, so the designers make the structure as light/thin as possible while still being able to handle the acceleration forces when fuelled and pressurised.
If the weight of the rocket itself is too high it will not be able to lift any payload. If it is too light it falls apart in flight (or in one spectacular case, crumples in on itself when pressurisation fails).
They are entirely constrained by thrust versus mass, so the designers make the structure as light/thin as possible while still being able to handle the acceleration forces when fuelled and pressurised.
If the weight of the rocket itself is too high it will not be able to lift any payload. If it is too light it falls apart in flight (or in one spectacular case, crumples in on itself when pressurisation fails).
Atlas booster:
https://www.youtube.com/watch?v=imkdz63agHY
https://www.youtube.com/watch?v=imkdz63agHY
Rockets are actually pretty easy to poke holes in. They're meant to keep stuff in, not out. A dropped torque wrench blew up a Titan.
https://en.m.wikipedia.org/wiki/1980_Damascus_Titan_missile_...
https://en.m.wikipedia.org/wiki/1980_Damascus_Titan_missile_...
It's somewhat impressive that the actual nuclear warhead didn't so much as leak. Which is what's supposed to happen but still you don't usually design something to withstand a botched missile launch capable of 'catapulting' a 740 ton door.
There wouldn't be much to 'leak'. The nuclear material in weapons is relatively safe to handle as long as you don't ingest it. It's the post-explosion fission products that are nasty.
Also with nuclear weapons, as much engineering has gone into safety as into weapon design itself. It's astronomically improbable for a modern nuclear weapon to detonate prior to arming even if the explosive lens is set off.
The reentry vehicle is designed to come down at circa mach 14 so a little bit of heat and jostling isn't going to bother it.
Cool video about some of the engineering involved: https://www.youtube.com/watch?v=97t7Xj_iBv0
Also with nuclear weapons, as much engineering has gone into safety as into weapon design itself. It's astronomically improbable for a modern nuclear weapon to detonate prior to arming even if the explosive lens is set off.
The reentry vehicle is designed to come down at circa mach 14 so a little bit of heat and jostling isn't going to bother it.
Cool video about some of the engineering involved: https://www.youtube.com/watch?v=97t7Xj_iBv0
The word "safety" in connection with nukes has been redefined to mean "it blows when you push the button". So the DOE's responsibility to maintain the "safety" of the arsenal sounds much better than it is.
Not blowing up when you don't push the button doesn't have a name.
When they actually dropped a pair by accident from a B-52, both got very far into their ignition sequence before something failed. Questions were Asked, after. So it is probably better now. Here. Russia? Israel? India? No telling.
Not blowing up when you don't push the button doesn't have a name.
When they actually dropped a pair by accident from a B-52, both got very far into their ignition sequence before something failed. Questions were Asked, after. So it is probably better now. Here. Russia? Israel? India? No telling.
You're talking about an incident involving a mark-39 bomb which was built in the 1950s, the same time period when USA ran reactors with a man wielding an axe to cut rope to drop control rods as an emergency shutdown measure.
We have come a long, long way since then in nuclear safety both in weapons and reactors.
We have come a long, long way since then in nuclear safety both in weapons and reactors.
Who is "we"?
Does it include Rick Perry? You are aware that the supposed secret "nuke launch code" was seventeen zeroes?
Does it include Rick Perry? You are aware that the supposed secret "nuke launch code" was seventeen zeroes?
The code you're talking about is the final step in a long sequence of events that requires positive authorisation from 6+ individuals from the president down.
By the time you've punched in the code, whether it's an OTP or seventeen zeroes, you've already committed a missile to a target and you're already 100% going to go through with the launch because two missile combat crew members turned their keys.
Russia doesn't even bother with these kinds of codes. Their second strike capability is fully autonomous and will launch even if all of c&c infra is destroyed.
This also has absolutely nothing to do with the mechanical intrinsic safety of the actual nuclear weapon during a fire or the RV that carries it. Which is the original topic at hand. The code is just an extra step to arm the weapon. The physical safeties are there to 99.999% guarantee that the weapon will not detonate unless armed. Even if you try really really hard to detonate it.
More thinking has gone into each tiny element of this process including the kind of paint used on bombs, than you have given to the topic as a whole.
By the time you've punched in the code, whether it's an OTP or seventeen zeroes, you've already committed a missile to a target and you're already 100% going to go through with the launch because two missile combat crew members turned their keys.
Russia doesn't even bother with these kinds of codes. Their second strike capability is fully autonomous and will launch even if all of c&c infra is destroyed.
This also has absolutely nothing to do with the mechanical intrinsic safety of the actual nuclear weapon during a fire or the RV that carries it. Which is the original topic at hand. The code is just an extra step to arm the weapon. The physical safeties are there to 99.999% guarantee that the weapon will not detonate unless armed. Even if you try really really hard to detonate it.
More thinking has gone into each tiny element of this process including the kind of paint used on bombs, than you have given to the topic as a whole.
Once you've already designed something to survive a very steep and fast atmospheric re-entry with delicate electronics intact, it's going to withstand other kinds of punishment pretty well too.
An 8lb socket dropped 80 feet. That's going to put a heck of a dent in almost anything.
Assuming I remember my high school physics correctly, the socket would be moving ~50mph on impact. Definitely a recipe for a bad day.
For reference, the average human seems (from a very brief search) to swing an 8lb sledgehammer at ~25mph. So it's a bit like someone very, very strong (think strongman competitions) nailing the thing as hard as they can with a sledgehammer.
It would be a glancing blow, though. Bad, but not as bad as a blow striking orthogonal to the surface.
It wasn't a glancing blow. It solidly struck a thrust mount and then bounced to pierce the tank. So while some energy was lost in the collision with the thrust mount (how elastic was it?) the blow that counted was dead-on.
Then the fuel just drained out for a long time. Long enough for the guy to dawdle before telling anybody, and then to get orders from higher-up, and for everybody to high-tail it out of the complex.
Not far enough, though.
Not far enough, though.
Except the guy they sent back in to turn on an exhaust fan that arced and blew everything up...
Poor bastard.
Poor bastard.
Ah, good point. For some reason I was imagining the rocket lying on its side or some nonsense.
There's also a fantastic This American Life about the incident: https://www.thisamericanlife.org/634/human-error-in-volatile...
I find the mobile view a lot easier to read on my laptop, funnily enough. I've started preferring mobile links to wikipedia lately.
You're not wrong that Starship has very thin walls, but they're actually quite thick compared to some rockets. There are rockets in use today that have to be pressurized to avoid collapsing under their own weight.
Any lead on where I can read on starship technical docs? Things like wall width
The /r/spacex subreddit can be a good source, as well as the NSF forums (particularly the L2 (subscription) side).
https://forum.nasaspaceflight.com/
https://forum.nasaspaceflight.com/
Soda cans are actually incredibly strong for their weight.
At least when filled and pressurized.
An empty soda can is much stronger relative to its weight than a full one.
If it's filled with liquid.
You don't want your rocket to be heavier than necessary. They're usually dead weight once in orbit. So yes, they're a bit like a soda can. Just as strong as necessary.
It looks as if not only the bulkhead got separated but also the top-most ring where it was attached. I don't remember right now how that section looked, but maybe it was not the bulkhead at a fault but the seam between the first and second ring from the top.
I agree that's what it looks like. Interestingly, during fabrication, the bulkhead was attached to the ring, and then the whole ring was lifted up and welded on. Maybe there was interaction of the heat affected area from the two welds? The bulkhead was welded only ~100mm up from the bottom of the ring.
During prototype tests you don't have to target 6-sigma, obviously, but I hope we get a post-mortem without spin.
When their entire business depends on very carefully managing their PR, you're not going to get a public post-mortem without spin.
If a government regulator runs the investigation, you might. I don't know if a regulator's going to get involved in this, though.
If a government regulator runs the investigation, you might. I don't know if a regulator's going to get involved in this, though.
> When their entire business depends on very carefully managing their PR
You really think this? My perception is that their PR is fairly blunt and upfront. while they may not tell you everything they dont seem to be trying to "spin" anything
You really think this? My perception is that their PR is fairly blunt and upfront. while they may not tell you everything they dont seem to be trying to "spin" anything
>they dont seem to be trying to "spin" anything
Compare their statements about the cause of the CRS-7 explosion to NASA's.
Compare their statements about the cause of the CRS-7 explosion to NASA's.
I dug around and didn't find an official SpaceX statement. The cause was a poorly constructed struct they bought from a 3rd party company.
> Compare their statements about the cause of the CRS-7 explosion to NASA's.
Did NASA's and SpaceX's statements differ in content?
> Compare their statements about the cause of the CRS-7 explosion to NASA's.
Did NASA's and SpaceX's statements differ in content?
SpaceX statement: https://www.spacex.com/news/2015/07/20/crs-7-investigation-u...
NASA accident investigation report: https://www.nasa.gov/sites/default/files/atoms/files/public_...
TBF the NASA report came much later than the SpaceX explanation. However it might be of interest to compare:
SpaceX explanation of why looking at the right telemetry is hard vs "Technical Finding 4" from NASA.
SpaceX explanation of the strut's "certifications" and max load vs "Technical Finding 1" (and the longer explanation earlier in the document, you can do a control-f for "Where the IRT differs with SpaceX is in regards to the initiating cause")
NASA accident investigation report: https://www.nasa.gov/sites/default/files/atoms/files/public_...
TBF the NASA report came much later than the SpaceX explanation. However it might be of interest to compare:
SpaceX explanation of why looking at the right telemetry is hard vs "Technical Finding 4" from NASA.
SpaceX explanation of the strut's "certifications" and max load vs "Technical Finding 1" (and the longer explanation earlier in the document, you can do a control-f for "Where the IRT differs with SpaceX is in regards to the initiating cause")
"SpaceX chose to use an industrial grade (as opposed to aerospace grade) ... cast part"
Hmm.. Isn't this a common cost-cutting strategy for Musk's companies? The touchscreen in the Model 3s was (is?) also industrial grade, if I recall correctly.
Hmm.. Isn't this a common cost-cutting strategy for Musk's companies? The touchscreen in the Model 3s was (is?) also industrial grade, if I recall correctly.
> The touchscreen in the Model 3s was (is?) also industrial grade, if I recall correctly.
Isn't that exactly what it should be? Or would you expect aerospace grade material there? Or is there yet another grade in between called 'automotive'?
Isn't that exactly what it should be? Or would you expect aerospace grade material there? Or is there yet another grade in between called 'automotive'?
Yup! I think the common electronic tolerances go: commerical, industrial, automative, military, aerospace, and then space, though I may be missing one or two.
There was a public accusation that a competitor shot one of their rockets with a rifle, causing it to fail. If they had reasonable suspicion of that, they should have kept it to themselves and the FBI/law enforcement. What really happened is that a strut failed due to faulty batch of material that wasn't tested before fabrication.
I'm not sure if this was deliberate spin, but it seemed pretty shady to me at the time.
I'm not sure if this was deliberate spin, but it seemed pretty shady to me at the time.
I don't think SpaceX ever made that accusation. At the time (2016) Musk said the cause of failure was unknown. He was asked directly about sabotage on Twitter and replied that they didn't rule that out. As far as I can tell, the first time anyone at SpaceX talked about the rifle hypothesis was Musk simply saying SpaceX looked into it (the implication being it wasn't sabotage).
WaPro: http://archive.is/j8zjc
WaPro: http://archive.is/j8zjc
These are the guys that give us amusing compilations of some of their more explosive mistakes:
https://www.youtube.com/watch?v=bvim4rsNHkQ
So much for very carefully managing PR.
https://www.youtube.com/watch?v=bvim4rsNHkQ
So much for very carefully managing PR.
Thank you so much for sharing this!
> When their entire business depends on very carefully managing their PR
That is simply wrong. Their business depends on reliably launching rockets and delivering payloads to station. And that is what they have done.
> If a government regulator runs the investigation, you might. I don't know if a regulator's going to get involved in this, though.
They are not going to. Starship is a SpaceX project that is not financed by NASA or the DoD.
That is simply wrong. Their business depends on reliably launching rockets and delivering payloads to station. And that is what they have done.
> If a government regulator runs the investigation, you might. I don't know if a regulator's going to get involved in this, though.
They are not going to. Starship is a SpaceX project that is not financed by NASA or the DoD.
If you go back a couple hours in the linked live feed you can find the event pretty easily. Look for the big plume in the preview when you hover over the progress bar. About 1:50 ago at this working writing. I guess it would have been around 1540 EST.
Looks like the welds holding the bulkhead on failed.
For those who aren't keeping up with this the failure was on the Mk1 prototype. Mk2 has been build nearly in parallel with Mk1 and will take over early flight testing (20km hop). Elon has tweeted that this team will jump to Mk3 instead of trying to repair Mk1.
For those who aren't keeping up with this the failure was on the Mk1 prototype. Mk2 has been build nearly in parallel with Mk1 and will take over early flight testing (20km hop). Elon has tweeted that this team will jump to Mk3 instead of trying to repair Mk1.
Airliners rarely use welds because they're very hard to make with consistent high quality and are also very hard to inspect. Instead, they're riveted together.
There are airplanes constructed with chemical bonding as well, such as the Boeing 787 Dreamliner and my personal favorite, the AA-1, released in 1967! Welded airplanes are practically nonexistent, but there are techniques other than riveting. And with the rise in popularity of composite materials, we're likely to see fewer and fewer rivets on airplanes.
Friction stir welding is popular in rocketry because it is very controllable.
Is the mk2 in the parallel location?
Yes, SpaceX is currently building Mk2 in Cocoa, Florida.
Here's an aerial video from beginning of october: https://www.youtube.com/watch?v=ChXMhSmqYqs
Here's an aerial video from beginning of october: https://www.youtube.com/watch?v=ChXMhSmqYqs
Comment from Elon Musk: https://twitter.com/elonmusk/status/1197271943180771329
Official SpaceX statement: https://twitter.com/thesheetztweetz/status/11973066177605591...
Official SpaceX statement: https://twitter.com/thesheetztweetz/status/11973066177605591...
I don’t know the specifics of this particular setup, but aren’t pressure vessels usually tested hydrostatically.
Water, for example, can be pressurised without actually compressing, and therefore doesn’t undergo rapid expansion when a failure occurs.
There may be reason that precluded pressure testing with a fluid tough.
Water, for example, can be pressurised without actually compressing, and therefore doesn’t undergo rapid expansion when a failure occurs.
There may be reason that precluded pressure testing with a fluid tough.
Compared to the fuels that the vessel is designed to carry, water might as well be liquid lead. It would easily crush the structure before you got enough in there to do hydro testing.
Edit: correction, looks like they're using methane/LOX. Methane is 422g/L and LOX is 1141g/L (compared to water at 1000g/L). If it was the LOX tank then they could have probably hydro tested it. Not so much with the CH4 which is probably the upper tank? It also bears mentioning that they would want to test at the appropriate temperatures. Water isn't great for hydro testing at LOX/liquid CH4 temps.
Edit: correction, looks like they're using methane/LOX. Methane is 422g/L and LOX is 1141g/L (compared to water at 1000g/L). If it was the LOX tank then they could have probably hydro tested it. Not so much with the CH4 which is probably the upper tank? It also bears mentioning that they would want to test at the appropriate temperatures. Water isn't great for hydro testing at LOX/liquid CH4 temps.
How do you "hydro" test it at cryogenic temperatures, where physical properties of the vessel material are markedly different?
Maybe weight? Filling something that big with water would be very heavy; maybe it's not strong enough in all the right places to support that much mass.
Water is lighter than liquid oxygen (which is what this tank would be holding in "production"). For the purposes of this test, they were likely using liquid nitrogen, which has ~80% the mass of water.
Just another test.
However...
To me there is an issue with large diameter pressured tubes - the point where the tube connects to the top is affected by the surface area divided by the diameter. Obviously one of those scales linearly, and the other squared.
That suggests to me (I'm definitely not a rocket scientist!) that the upper bound might be smaller than this diameter, or the weight will have to increase in order to beef up the strength of this point.
Pretty interesting problem to deal with now that they are this far into the design. I'm sure there are many possible solutions, and it will be fun to see what they come up with.
However...
To me there is an issue with large diameter pressured tubes - the point where the tube connects to the top is affected by the surface area divided by the diameter. Obviously one of those scales linearly, and the other squared.
That suggests to me (I'm definitely not a rocket scientist!) that the upper bound might be smaller than this diameter, or the weight will have to increase in order to beef up the strength of this point.
Pretty interesting problem to deal with now that they are this far into the design. I'm sure there are many possible solutions, and it will be fun to see what they come up with.
Nothing blows up means you aren't innovative enough.
I think it’s good. Better to find the flaws now and do a resdesign, instead of having astronaughts being blown out into space ;)
I haven’t seen an mention if anyone was injured. Was there someone on the cherry picker?
You would never have people around when doing high pressure ops. This might even have been a proof test, where the tank is pressurized to test for leaks so something like this failure is a plausible scenario.
Whoever gets in that thing is spam in a can /s (quote from the right stuff)
"Was that the primary buffer panel?"
for some reason i feel like im watching a 2nd grader's baking soda volcano project. i guess it's the perspective of the camera, or im not accustomed to the looks of prototype rockets, but to me it looks like a paper mache diorama
Starship looks particularly shoddy because it's made from relatively small steel plates welded together. The welding process causes each plate to warp slightly, so the end result looks like a quilt rather than a nice uniformly smooth cylinder. Most rockets don't look like this. Most prototype rockets don't look like this either.
The argument has been that this is good enough to start testing structural features, and probably also good enough to do a little bit of low-stress flying as well. The first argument seems sound. I'm not so sure about the second... there are a lot of welds. At least a few of them are likely to be structurally unsound, and assessing weld quality is difficult.
In any case, for the "real" Starship, they plan to use a technique similar to the one they use on Falcon, where they roll a huge metal plate and then stir-friction weld along the seam. This kind of tooling is difficult and expensive to set up, and the configuration of the machinery and the material depends a lot on the actual design, which hasn't been finalized yet.
Apparently they're using thicker steel then they plan to use on the monolithically constructed version to compensate for weld quality, but I don't know... weld seams are great stress concentrators, and stress concentrations are where fractures are likely to form, and fractures on the skin of a rocket are usually catastrophic failures. All it takes is one defect.
The argument has been that this is good enough to start testing structural features, and probably also good enough to do a little bit of low-stress flying as well. The first argument seems sound. I'm not so sure about the second... there are a lot of welds. At least a few of them are likely to be structurally unsound, and assessing weld quality is difficult.
In any case, for the "real" Starship, they plan to use a technique similar to the one they use on Falcon, where they roll a huge metal plate and then stir-friction weld along the seam. This kind of tooling is difficult and expensive to set up, and the configuration of the machinery and the material depends a lot on the actual design, which hasn't been finalized yet.
Apparently they're using thicker steel then they plan to use on the monolithically constructed version to compensate for weld quality, but I don't know... weld seams are great stress concentrators, and stress concentrations are where fractures are likely to form, and fractures on the skin of a rocket are usually catastrophic failures. All it takes is one defect.
The Starships shininess makes it look even more wrinkly. If it wasn't reflecting its surroundings so well, you would not be able to see that it's not perfectly smooth.
Here's a similar effect on windows:
https://c8.alamy.com/comp/D60B28/distorted-reflections-in-a-...
That's why Starship can look a lot better when photographed from nearby - the view is tilted more upwards and the sky is reflecting in it which does not have enough details to let one see these wrinkles.
Here's a similar effect on windows:
https://c8.alamy.com/comp/D60B28/distorted-reflections-in-a-...
That's why Starship can look a lot better when photographed from nearby - the view is tilted more upwards and the sky is reflecting in it which does not have enough details to let one see these wrinkles.
The front fell off!
kouba(1)
[deleted]
Aren't pressure tests done with water?
That way, since water is non-compressible, if it fails, you just get a small hole or buldge somewhere rather than the catastrophic damage seen here.
Perhaps they already tested with water and now needed to test with the real fuel/oxygen to get the temperature correct?
That way, since water is non-compressible, if it fails, you just get a small hole or buldge somewhere rather than the catastrophic damage seen here.
Perhaps they already tested with water and now needed to test with the real fuel/oxygen to get the temperature correct?
Is it strong enough to take a full tank of water? Liquid methane weighs less than half what water weighs.
Liquid oxygen weighs more than water though...
True, although only slightly. Of course, it also wouldn't be trying to take off with a full tank of water and you'd expect it to pull at least 2G during takeoff (do we have an actual figure?) so I'm guessing the answer would be 'yes, it could take it'?
This integration test is way too late to be finding faults like these. This is top down design, which is expensive an error prone. The ship should be designed and tested in a bottom up fashion, such that the failure modes of every individual component is already known, as per Feynman. SpaceX is repeating the mistakes of the Space Shuttle program.
There was a post on HN a few days ago about how SpaceX got a full examination, while Boeing more or less got a pass from Nasa. This is a different vehicle, but it gives an idea of the maturity of SpaceX. And yes, the earlier story was really more about trying to establish a pattern around the 737 Max failure, but that issue was at least complicated. This is just sloppy.
[1]: https://news.ycombinator.com/item?id=21574080
[1]: https://news.ycombinator.com/item?id=21574080
I had an unpopular opinion amongst friends that this thing looked like a total piece of shit, like a movie prop. They were using rented lifts and cranes to assemble it in the field. Clock right twice a day or maybe there's a reason everything about Apollo spacecraft was meticulously assembled.
I have a feeling that they could blow up another dozen of these and still be spending less than doing it the "traditional" way of in cleanrooms and the VFAB building.
This was a prototype that they've publicly said was most likely never to reach orbit, they are building this stuff right now to learn, test, and prove that their design works and find improvements that can be made.
This was a prototype that they've publicly said was most likely never to reach orbit, they are building this stuff right now to learn, test, and prove that their design works and find improvements that can be made.
Any elementary student of history can tell you how bad an idea this is. Apollo 1 almost ended the program. A backlash in public opinion will crater SpaceX in the market and legislature.
There is no space mission in the near decades worth the loss of human life. Economy in terms of money is no priority if you are to undertake human space flight. Move fast and break things is cute for a global search index or regressing public discourse and attention span; it's astronomically stupid and not acceptable for safety of human life.
If this were a billionaire playboy stroking his ego and putting his own money and life on the line who cares. It's not, he's using my tax dollars and is going to hurt others for negligible gain.
There is no space mission in the near decades worth the loss of human life. Economy in terms of money is no priority if you are to undertake human space flight. Move fast and break things is cute for a global search index or regressing public discourse and attention span; it's astronomically stupid and not acceptable for safety of human life.
If this were a billionaire playboy stroking his ego and putting his own money and life on the line who cares. It's not, he's using my tax dollars and is going to hurt others for negligible gain.
They aren't using any tax dollars for Starship. It's entirely funded by their profits (at least as far as I know).
And this Starship MK1 is/was a prototype designed to test some aspects of their design in the real world. It was never going to be anywhere close to taking people onboard. Even this incident had all people far away before they started doing anything like pressurising.
This is active development, every single rocket company or program in existence has had explosions and test failures, and they will continue to have them. The important part is that they are doing this safely and nobody is getting hurt, these are controlled tests.
It may not be the way you think rockets should be designed and built (I'm personally kinda skeptical that they will actually build the full prototypes/rockets outside like this), but it's not more dangerous than any other rocket company.
And this Starship MK1 is/was a prototype designed to test some aspects of their design in the real world. It was never going to be anywhere close to taking people onboard. Even this incident had all people far away before they started doing anything like pressurising.
This is active development, every single rocket company or program in existence has had explosions and test failures, and they will continue to have them. The important part is that they are doing this safely and nobody is getting hurt, these are controlled tests.
It may not be the way you think rockets should be designed and built (I'm personally kinda skeptical that they will actually build the full prototypes/rockets outside like this), but it's not more dangerous than any other rocket company.
Citations needed for the funding. Sounds like people being loose with the truth. The accounting alone would be close to impossible to keep separate.
I meant it as in no government contracts are going toward starship development, but looking it up it seems I'm actually wrong, maybe...
The air force has given them some money for development on their Raptor engine, and they've talked about wanting more government funding for starship itself, but they've also talked about how starship has been privately funded so far.
The air force has given them some money for development on their Raptor engine, and they've talked about wanting more government funding for starship itself, but they've also talked about how starship has been privately funded so far.
To be fair, the Raptor engine is a hell of an invention (a full flow engine!!), and well worth investing money into.
I love how people keep bringing up the fact SpaceX gets some government subsidies. Ever heard of SLS? LMAO.
Depends on what they're testing.
Every single one of my electronics prototypes look like shit. About one five of them produce smoke and burn marks. Every twentieth does something dramatically unexpected (usually entertaining).
Every single one of my electronics prototypes look like shit. About one five of them produce smoke and burn marks. Every twentieth does something dramatically unexpected (usually entertaining).
It looking like a piece of shit is an unpopular opinion?
I assumed that was a consensus. The thing isn't trying to win any beauty contests, it's covered in ugly seam welds.
And none of that matters, not one bit.
I assumed that was a consensus. The thing isn't trying to win any beauty contests, it's covered in ugly seam welds.
And none of that matters, not one bit.
It's not cosmetics. What kind of tolerances can you get dangling a massive assembly from a crane in the wind? How many people are cross checking the work? What kind of instrumentation are you using to check joint quality and integrity at these heights from a genie lift? It’s hard to shoot a stucco roof from a genie lift, I can’t help but laugh out loud at the assertion this is sane. Astronomically stupid.
I laugh out loud at armchair engineers who think they have any real insight into a massive engineering development program like Starship.
SpaceX has proven themselves over and over again of being more than capable of achieving their goals in light of people like you.
SpaceX has proven themselves over and over again of being more than capable of achieving their goals in light of people like you.
Yup let's see how the non critically thinking Musk fan thing works out for you in 10 years. People like Carl Sagan and Richard Feynman would be shaking their heads at these spectacles.
You were the guy who 10 years ago said electric cars and reusable rockets would never be practical.
Meanwhile SpaceX is on their way to building a global internet constellation, have a working full flow combustion engine, and has multiple prototype Mars rockets in development.
I'd love to take your 10 year bet. Easy money.
Meanwhile SpaceX is on their way to building a global internet constellation, have a working full flow combustion engine, and has multiple prototype Mars rockets in development.
I'd love to take your 10 year bet. Easy money.
Except I wasn't. SpaceX has done well for cargo launches. The cargo work appears to be good enough with great economy and any losses can be modeled by the mature insurance industry.
Starhopper looked just as "rough and ready" but completed a successful test flight a few months back.
I wish more smart people like you worked there.
Well, it's not like this is rocket science. Oh, wait...
Manufacturing and assembly of high strength hardened steel is near black art.
Pathfinders do exactly what they say, they lead you through unknown territory to the outcome of the manufacturing journey you embarked on. Often things go boom, you find out why, add it to your corpus of black art knowledge, and keep pathfinding until you run out of budget / succeed / change mission.
So as manufacturing pathfinder, this is what success often looks like.