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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

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.

19870213 7y ago
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.
tinco 7y ago
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.
- Roark66 7y ago
  >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.
  - labawi 7y ago
    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.
lutorm 7y ago
They are using 301 stainless which, as far as I know, cannot be hardened.

19870213 7y ago

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.

tinco 7y ago

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.

Roark66 7y ago
>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.
- labawi 7y ago
  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.

lutorm 7y ago

They are using 301 stainless which, as far as I know, cannot be hardened.