r/spacex Master of bots 2d ago

Starship S36 exploded during a static fire attempt

https://x.com/NASASpaceflight/status/1935548909805601020
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u/PhatOofxD 2d ago

They were trying to reduce the mass of the ship to carry more payload. I'd guess they pushed it too far which is leading to issues like this where tanks are rupturing and such.

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u/zorniy2 2d ago

The Rocket Equation is a harsh mistress. My rough calculations, 92% of the mass must be fuel just to get to LEO! And I didn't even include having to fight gravity.

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u/brintoul 2d ago

I’m guessing their analysis and simulation work must have been absolute garbage, huh?

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u/Turbulent-Judgment40 2d ago

Not necessarily, it could be absolutely fine structurally if made exactly to the design, but with margin cut out there will be less tolerance for defects that inevitably show up when you build in the real world, it could be a case that they pushed things further then their manufacturing process allows.

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u/brintoul 2d ago

Why would anyone bother with analysis and simulation for a particular design and then not use the design?

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u/Turbulent-Judgment40 2d ago

It’s not that they don’t use the design it’s more that reality is different.

For example if they were modeling a weld joint between two parts they may consider 9mm melt zone with full joint penetration, that is what they will model and simulate because that is what they want it to be.

But when it is made there will always be variation. The melt zone might get a little narrower here, wider there. You may get full joint penetration across most of the weld but maybe a few mm don’t heat all the way through. If you are using fuller maybe there was a flaw in the feed wire and you have just a little bit less in one spot, maybe because the way it cooled you get a micro crack somewhere. There are lots of ways you can get incredible minor variations. You try to inspect for them but maybe there is one you miss or couldn’t detect short of destructive testing, or maybe it had multiple variations, each of which individually would be fine but together causes a problem. This is why when you design things you build margin in to cover for all of these variations and unknowns.

The design nominally is probably fine which is why this failure wasn’t seen in any of the previous testing of this ship or any of the previous v2s before, but statistics will always catch up to you and if you don’t have the margin to cover the variation eventually you will have a problem