totm nov 2023 SpaceX Discussion Thread

[RealKerbal3x]

Just now, Geonovast said:

Hopefully whatever it was is something they'd already improved for Mk2.

Yeah...we wouldn’t want to rely on Mk2 and then have it do the same thing

[CatastrophicFailure]

 

[KSK]

That’ll be the new Russian hire’s work. Aleksandr Popov.

 

Edit. To be clear, this comment was made purely for the bad pun. I am not casting aspersions on Russian engineering or Russians in general.

Edited November 20, 2019 by KSK

[Scotius]

Welp, on to the next prototype. Frankly, i don't think anyone at SpaceX was terribly surprised something like that happened. There was a reason they built multiple prototypes

[Ultimate Steve]

Oof.

I wonder if parts of Mk1 got higher than Starhopper.

 

[sh1pman]

12 minutes ago, KSK said:

That’ll be the new Russian hire’s work. Aleksandr Popov.

Roscosmos sends their regards

[mikegarrison]

55 minutes ago, tater said:

the whole thing smoothed out under pressure, looked much cleaner before it blew.

This is kind of like saying, "my car looked great right until it crashed into that tree".

[tater]

38 minutes ago, mikegarrison said:

This is kind of like saying, "my car looked great right until it crashed into that tree".

I was just thinking of how the texture changed under pressure. Mk3/4 will have those 1 piece rings, faster to build, presumably.

[mikegarrison]

One reason planes have traditionally used a lot of rivets and fasteners instead of welds is that welds tend to be a little more variable. It's harder to be sure of exactly how strong they are.

It's also a lot trickier to weld aluminum without messing up the very important heat treatment characteristics.

Edited November 20, 2019 by mikegarrison

[mikegarrison]

With actual water tanks, and a lot of other pressure vessels, it's pretty standard to use a criterion known as "leak before burst". I wonder if SpaceX explicitly considered that? (Of course, they may have, and this was just an unexpected failure mode.)

https://en.wikipedia.org/wiki/Pressure_vessel#Leak_before_burst

[StrandedonEarth]

Well now that's a shame. But hey, it's real rocket science when pieces go flying.

2 hours ago, Serpens Solidus said:

Switch to camera 3 and rewind to 3:25:50 pm

Dang, I waited too long and can't rewind that far now. Pity.

 

[tater]

55 minutes ago, mikegarrison said:

With actual water tanks, and a lot of other pressure vessels, it's pretty standard to use a criterion known as "leak before burst". I wonder if SpaceX explicitly considered that? (Of course, they may have, and this was just an unexpected failure mode.)

https://en.wikipedia.org/wiki/Pressure_vessel#Leak_before_burst

They did that yesterday, actually, I think. People seem to think they were pressurizing it this time with nitrogen, BTW, no idea if that is true.

[mikegarrison]

13 minutes ago, tater said:

They did that yesterday, actually, I think. People seem to think they were pressurizing it this time with nitrogen, BTW, no idea if that is true.

"Leak before burst" isn't a test, really. It's a design criterion, mostly about crack propagation. If the cracks propagate slowly enough, then the vessel starts to leak and the pressure is relieved. If the crack propagates too quickly, you have events like this where the tank blows apart before enough pressure has leaked out.

Blowout panels and safety valves are much the same idea and serve the same purpose, although they are conceptually more like fuses. Leak before burst is more like choosing a failure mode that is less catastrophic than the alternative failure mode.

Edited November 21, 2019 by mikegarrison

[CatastrophicFailure]

They were, indeed, pressurizing to max, so likely nitrogen.

I think they found “Max” too...

...guess he was mad...

[jadebenn]

3 hours ago, CatastrophicFailure said:

They were, indeed, pressurizing to max, so likely nitrogen.

I think they found “Max” too...

...guess he was mad...

No offense, but that's like excusing a boiler explosion by saying it was under a lot of pressure. This is not cutting edge materials science. We know how to make pressure vessels that don't blow up when in use.

Edited November 21, 2019 by jadebenn

[ZooNamedGames]

28 minutes ago, jadebenn said:

No offense, but that's like excusing a boiler explosion by saying it was under a lot of pressure. This is not cutting edge materials science. We know how to make pressure vessels that don't blow up when in use.

I blame Musk since his excessively tight scheduling regime leaves little room for error, meaning every test, every inspection, every review has to be perfect. Humans aren’t. Though we don’t know the cause yet- it often is rooted in human error- and if it’s mechanical- that’s even more reason to panic as that’s a sign of ineptitude or an engineer’s design ignorance. Either way, this does not paint Musk in a good light.

[tater]

3 minutes ago, ZooNamedGames said:

I blame Musk since his excessively tight scheduling regime leaves little room for error, meaning every test, every inspection, every review has to be perfect. Humans aren’t. Though we don’t know the cause yet- it often is rooted in human error- and if it’s mechanical- that’s even more reason to panic as that’s a sign of ineptitude or an engineer’s design ignorance. Either way, this does not paint Musk in a good light.

It cost the taxpayer... nothing at all. Delays on someone else's dime are not terribly concerning. You know what would paint Musk in a really bad light? If his goal was to make a Moon rocket, and he spent billions to build a "not quite Moon rocket" that wasn;t really good for anything at all.

 

 

Rumors are flying right now, a couple interesting ones:

First (and hinted at by a Musk tweet), Mk3/4 are substantially different than Mk1/2 in some way (mass is already expected to be substantially less than the 200t+ mk1), and that Mk1 wasn't gonna do the 20km flight. This was even out there this morning before the test apparently.

Second, there is some talk that they were doing a planned test to 1.5-2X the densified prop pressure (~3bar for that, so testing to 4.5 - 6 bar), and a GSE error resulted in it going well past that.

[jadebenn]

3 minutes ago, tater said:

Second, there is some talk that they were doing a planned test to 1.5-2X the densified prop pressure (~3bar for that, so testing to 4.5 - 6 bar), and a GSE error resulted in it going well past that.

I'm not sure if that would be better or worse than it just suddenly popping a seam.

On one hand, it would mean that their tanks weren't crap. On the other hand, it would suggest they had no alternative safe-guards and therefore had a single point of failure.

Edited November 21, 2019 by jadebenn

[tater]

4 minutes ago, jadebenn said:

On one hand, it would mean that their tanks weren't crap. On the other hand, it would suggest they had no alternative safe-guards and therefore had a single point of failure.

This was always a throw away vehicle. It's a hopper meant to test a specific thing, horizontal fall, and transition back to vertical for landing. My only concern is I wanted to see one of these fly sooner rather than later (like within weeks vs months).

From the NSF article:

Quote

But the impact will likely be limited, with SpaceX also noting that a decision not to fly Mk1 had already been made prior to today’s test. Instead, the company will focus on the improved Mk3 design. Elon Musk noted in September that Mk3 would not only have a very different build process, but would also take significantly less time to construct than Mk1.

 

[tater]

Definitely an issue to be addressed, BTW---whatever the failure was, GSE, welds, failed pressure release valve (does it have one?).

Best "silver lining" would be if it was indeed accidentally overpressured beyond 3X, and they got good data.

[Wjolcz]

[jadebenn]

37 minutes ago, tater said:

This was always a throw away vehicle. It's a hopper meant to test a specific thing, horizontal fall, and transition back to vertical for landing. My only concern is I wanted to see one of these fly sooner rather than later (like within weeks vs months).

True. But at the same time this failure mode shouldn't be hard to mitigate.

Like I said, a lot depends on the specifics.

[tater]

38 minutes ago, jadebenn said:

True. But at the same time this failure mode shouldn't be hard to mitigate.

Like I said, a lot depends on the specifics.

Agreed.

[magnemoe]

1 hour ago, tater said:

 

Rumors are flying right now, a couple interesting ones:

First (and hinted at by a Musk tweet), Mk3/4 are substantially different than Mk1/2 in some way (mass is already expected to be substantially less than the 200t+ mk1), and that Mk1 wasn't gonna do the 20km flight. This was even out there this morning before the test apparently.

Second, there is some talk that they were doing a planned test to 1.5-2X the densified prop pressure (~3bar for that, so testing to 4.5 - 6 bar), and a GSE error resulted in it going well past that.

Its pretty standard to pressure test with higher than standard pressure. This to make sure that you have margins and that its unlikely that the tank will blow up at an later date, if you just pressurized with 3 bar, you proven that it can take 3 bar for 30 minutes, not 3 days. 

We have seen the new sections, fewer welds for one, it looks like its full lengt panels so just one weld to make an section, 

[RealKerbal3x]

If they say that they’re going straight for Mk3, what will happen with Mk2? Will it still fly?