5 ms·

I'm guessing / hoping that the engine outs we're planned, or that they ran the engines with slightly different parameters to test them. If it's just unreliabili

by Geee 5mo ago

I'm guessing / hoping that the engine outs we're planned, or that they ran the engines with slightly different parameters to test them. If it's just unreliability then it might be a hard problem to solve.

Octoth0rpe 5mo ago
> If it's just unreliability then it might be a hard problem to solve. It might, but it certainly helps having a ton of them around. Given that they used 42 of them today and 2 failed in some fashion, we'll call that a 1:21 failure rate. On a more typical rocket with say 10 engines (eg falcon 9), there's a good chance they wouldn't have seen the same failure till flight 3.
- deleted 5mo ago
  [deleted]
- brianwawok 5mo ago
  It’s something like up to 6 can fail and it keeps going, seems pretty good. I know they did some stuff like remove a heat tile to get failure feedback, wonder if engine was planned or accidental
  - NetMageSCW 5mo ago
    Accidental since they didn’t make the sub-orbit they were aiming for and thus couldn’t test engine re-light.
- avmich 5mo ago
  > Given that they used 42 of them today 20+10+3=33 on the booster, 3+3=6 on the Ship, total 39. I remember Elon said they want to add 2 engines to the first stage, but that still would be 41. Where's the 42th supposed to be?
  - Octoth0rpe 5mo ago
    I messed up, for some reason I had it in my head that there were 9 on starship, so 33 + 9 = 42.
- mlyle 5mo ago
  Adjusted wald intv'l gives us for 2 observed out of 39 gives us a "true" failure rate from 1 in 200 to 1 in 6 (95% CI).
Zee2 5mo ago
Very first flight of a brand new engine type (Raptor 3) with totally reworked heatshielding/plumbing/sensors/control systems/etc.
- ajross 5mo ago
  Which is true, but at the same time: this is Starship Flight 12. The whole point of Starship is that it's a reusable vehicle with easy turnaround and quick maintenance. And in particular it's supposed to be different than the other reusable vehicle with easy turnaround and quick maintenance, which turned out to be sort of a boondoggle. Yet, they've now hand-built and destroyed twelve of these things across multiple redesigns, and it still hasn't completed its design mission once. In fact basically every launch has unexpected major failures. As poor as its safety record ultimately ended up being, the shuttle launched successfully on its very first try. And we only had to hand-build five of them. And lost two, sure, which is still a lot less than twelve. Yes yes, I understand that iterative design has merits and that the ability to rapidly prototype and try things in the stratosphere allows for less conservative tolerances and better ultimate performance. But does it really take 13+ tries?! At what point to we start wondering if we have another boondoggle on our hands?
  - redox99 5mo ago
    If you can afford it, I'm sure anyone developing a rocket would prefer to do it this iterative way. I don't really understand the complain.
    - ajross 5mo ago
      The point was more that there is a point where (to borrow the software terminology) "iterative design" becomes "death march". Trying a few times in the early days and being willing to throw stuff out and start over is a powerful tool. I think blowing up a handful of rockets is a fine idea. But at some point you have to ask yourself if it will ever work? Why are we on a another engine redesign? Why is this the third iteration of the second stage? How many more? And what number is that point? Six? Nine? I'm thinking thirteen may be getting into the danger zone.

by Geee 5mo ago

Octoth0rpe 5mo ago

> If it's just unreliability then it might be a hard problem to solve. It might, but it certainly helps having a ton of them around. Given that they used 42 of them today and 2 failed in some fashion, we'll call that a 1:21 failure rate. On a more typical rocket with say 10 engines (eg falcon 9), there's a good chance they wouldn't have seen the same failure till flight 3.

deleted 5mo ago
[deleted]
brianwawok 5mo ago
It’s something like up to 6 can fail and it keeps going, seems pretty good. I know they did some stuff like remove a heat tile to get failure feedback, wonder if engine was planned or accidental
- NetMageSCW 5mo ago
  Accidental since they didn’t make the sub-orbit they were aiming for and thus couldn’t test engine re-light.
avmich 5mo ago
> Given that they used 42 of them today 20+10+3=33 on the booster, 3+3=6 on the Ship, total 39. I remember Elon said they want to add 2 engines to the first stage, but that still would be 41. Where's the 42th supposed to be?
- Octoth0rpe 5mo ago
  I messed up, for some reason I had it in my head that there were 9 on starship, so 33 + 9 = 42.
mlyle 5mo ago
Adjusted wald intv'l gives us for 2 observed out of 39 gives us a "true" failure rate from 1 in 200 to 1 in 6 (95% CI).

Zee2 5mo ago

Very first flight of a brand new engine type (Raptor 3) with totally reworked heatshielding/plumbing/sensors/control systems/etc.

ajross 5mo ago
Which is true, but at the same time: this is Starship Flight 12. The whole point of Starship is that it's a reusable vehicle with easy turnaround and quick maintenance. And in particular it's supposed to be different than the other reusable vehicle with easy turnaround and quick maintenance, which turned out to be sort of a boondoggle. Yet, they've now hand-built and destroyed twelve of these things across multiple redesigns, and it still hasn't completed its design mission once. In fact basically every launch has unexpected major failures. As poor as its safety record ultimately ended up being, the shuttle launched successfully on its very first try. And we only had to hand-build five of them. And lost two, sure, which is still a lot less than twelve. Yes yes, I understand that iterative design has merits and that the ability to rapidly prototype and try things in the stratosphere allows for less conservative tolerances and better ultimate performance. But does it really take 13+ tries?! At what point to we start wondering if we have another boondoggle on our hands?
- redox99 5mo ago
  If you can afford it, I'm sure anyone developing a rocket would prefer to do it this iterative way. I don't really understand the complain.
  - ajross 5mo ago
    The point was more that there is a point where (to borrow the software terminology) "iterative design" becomes "death march". Trying a few times in the early days and being willing to throw stuff out and start over is a powerful tool. I think blowing up a handful of rockets is a fine idea. But at some point you have to ask yourself if it will ever work? Why are we on a another engine redesign? Why is this the third iteration of the second stage? How many more? And what number is that point? Six? Nine? I'm thinking thirteen may be getting into the danger zone.