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To steelman the argument, maybe they meant "the monitoring system is good enough at catching defects that if none are reported, the engine will probably pass an

To steelman the argument, maybe they meant "the monitoring system is good enough at catching defects that if none are reported, the engine will probably pass an all-up hotfire test of the engine". Of course you could do a water or air-pressure leak test on the plumbing pretty easily, and you would likely do that on the first 30 engines... But if you have confidence in your build process, maybe the juice isn't worth the squeeze on (say) a direct contact ultrasound void check on every square millimeter of the part. It's all about "how expensive is it to run the test" vs "what is the likelihood the test catches an issue" vs "what's the cost of failing while everyone is watching?" Same reason SpaceX went from dry-dress-rehersals to wet-dress-rehearsals to separate-static-fire-before-launch to hold-down-for-three-seconds-before-launch... The hold-down -before-launch is an integration test that covers everything the previous tests do, so eventually you can start removing redundant tests.

sandworm101 2y ago
>> maybe the juice isn't worth the squeeze In rockets/aerospace, where the failure of any one of a thousand different parts means instant disintegration, checks are always worth the squeeze. Everyone talks about building rockets on the cheap and accepting a slightly-higher failure rate, but in reality that doesn't work. Even a tiny increase in component fault rates translates to total mission failure once multiplied across thousands of vital parts. The answer isn't to not check but to find ways to more efficiently and more thoroughly check each part. This is only more true if one considers reusable rockets where components will be expected to participate in multiple launches.
- giantrobot 2y ago
  > In rockets/aerospace, where the failure of any one of a thousand different parts means instant disintegration To make matters worse the failure modes don't only affect the launch vehicle itself. A failure of a rocket likely means a total loss of the payload. It also runs the risk of damage/loss of the launch pad, support structures, and hapless down range victims. Rockets contain a significant amount of stored chemical energy, enough to get the payload mass into a stable orbit of the Earth. If you release all of that energy at once as an explosion it will cause a significant amount of damage. Rockets aren't something to goof around with and make assumptions about safety.
- throwitaway222 2y ago
  Well, if you build it robust enough, you can test less. Not saying testing is worthless, but sometimes a one-piece that used to be 45 pieces held together by rivets is just, much much more resilient.
  - chfalck 2y ago
    It’s a bit of chicken and egg to know if you built it robust enough without meticulous testing of your robustness
  - InitialLastName 2y ago
    Robust enough to not need testing == too heavy to be cost-effective.
- jes5199 2y ago
  this might be 20th-century thinking. if you can build enough copies of a rocket cheap enough, maybe disintegrating a bunch of them isn't a showstopper
  - lesuorac 2y ago
    Who pays when the payload disintegrates?
  - nordsieck 2y ago
    > if you can build enough copies of a rocket cheap enough, maybe disintegrating a bunch of them isn't a showstopper The problem with that idea is that you won't be legally allowed to launch again until you root cause and fix the failure, which can take months (or years if you're Blue Origin). Also, your insurance rates tend to go up a lot when your rockets blow up regularly, which tends to push customers away. In practice it doesn't work. Notes: Astra said they were going to pursue this strategy. It was not well received by potential customers and they basically had to walk it back.
    - schmidtleonard 2y ago
      Doesn't work? It seems to be working great for the industry leader.
      - nordsieck 2y ago
        > Doesn't work? It seems to be working great for the industry leader. What are you talking about? SpaceX's Falcon 9 is arguably the most reliable rocket ever made. They've launched hundreds of times in a row without failure. If your point is that they're blowing up Starship prototypes, well... they're in the middle of a development program and they're not flying customer payloads.
        gus_massa 2y ago
        They blow up a few of the early Falcons, and the explosions got a lot of news coverage. Now they are launching an landing[1] safetly, but it's boring and the news show a cute puppy instead. So for most people the rate of explosions vs launching is skewed. [1] It's crazy that landing rockets is boring now.
- timerol 2y ago
  > checks are always worth the squeeze This is simply inaccurate. You can spend months and hundreds of millions of dollars running scanning electron microscopes over all of your parts - no one does this, because it's not "worth the squeeze". The question is where to draw the line, and I have no idea what your opinion is there.
- treflop 2y ago
  My dad works in aerospace. In no field or world does anyone actually check every little part. You create a process, you test that process so that you understand its limits, and then you make sure to follow that process. Now I don't know if 3D printing rocket parts actually works and I have my doubts but this startup is currently testing the process and they will figure out its limits. That's the whole point of R&D.
  - Etheryte 2y ago
    For context, 3D printing rocket parts is incredibly common, even student teams often use printed nozzles and such. The linked article is about printing a whole engine as a single piece, which is a different beast.

sandworm101 2y ago

>> maybe the juice isn't worth the squeeze In rockets/aerospace, where the failure of any one of a thousand different parts means instant disintegration, checks are always worth the squeeze. Everyone talks about building rockets on the cheap and accepting a slightly-higher failure rate, but in reality that doesn't work. Even a tiny increase in component fault rates translates to total mission failure once multiplied across thousands of vital parts. The answer isn't to not check but to find ways to more efficiently and more thoroughly check each part. This is only more true if one considers reusable rockets where components will be expected to participate in multiple launches.

giantrobot 2y ago
> In rockets/aerospace, where the failure of any one of a thousand different parts means instant disintegration To make matters worse the failure modes don't only affect the launch vehicle itself. A failure of a rocket likely means a total loss of the payload. It also runs the risk of damage/loss of the launch pad, support structures, and hapless down range victims. Rockets contain a significant amount of stored chemical energy, enough to get the payload mass into a stable orbit of the Earth. If you release all of that energy at once as an explosion it will cause a significant amount of damage. Rockets aren't something to goof around with and make assumptions about safety.
throwitaway222 2y ago
Well, if you build it robust enough, you can test less. Not saying testing is worthless, but sometimes a one-piece that used to be 45 pieces held together by rivets is just, much much more resilient.
- chfalck 2y ago
  It’s a bit of chicken and egg to know if you built it robust enough without meticulous testing of your robustness
- InitialLastName 2y ago
  Robust enough to not need testing == too heavy to be cost-effective.
jes5199 2y ago
this might be 20th-century thinking. if you can build enough copies of a rocket cheap enough, maybe disintegrating a bunch of them isn't a showstopper
- lesuorac 2y ago
  Who pays when the payload disintegrates?
- nordsieck 2y ago
  > if you can build enough copies of a rocket cheap enough, maybe disintegrating a bunch of them isn't a showstopper The problem with that idea is that you won't be legally allowed to launch again until you root cause and fix the failure, which can take months (or years if you're Blue Origin). Also, your insurance rates tend to go up a lot when your rockets blow up regularly, which tends to push customers away. In practice it doesn't work. Notes: Astra said they were going to pursue this strategy. It was not well received by potential customers and they basically had to walk it back.
  - schmidtleonard 2y ago
    Doesn't work? It seems to be working great for the industry leader.
    - nordsieck 2y ago
      > Doesn't work? It seems to be working great for the industry leader. What are you talking about? SpaceX's Falcon 9 is arguably the most reliable rocket ever made. They've launched hundreds of times in a row without failure. If your point is that they're blowing up Starship prototypes, well... they're in the middle of a development program and they're not flying customer payloads.
      - gus_massa 2y ago
        They blow up a few of the early Falcons, and the explosions got a lot of news coverage. Now they are launching an landing[1] safetly, but it's boring and the news show a cute puppy instead. So for most people the rate of explosions vs launching is skewed. [1] It's crazy that landing rockets is boring now.
timerol 2y ago
> checks are always worth the squeeze This is simply inaccurate. You can spend months and hundreds of millions of dollars running scanning electron microscopes over all of your parts - no one does this, because it's not "worth the squeeze". The question is where to draw the line, and I have no idea what your opinion is there.
treflop 2y ago
My dad works in aerospace. In no field or world does anyone actually check every little part. You create a process, you test that process so that you understand its limits, and then you make sure to follow that process. Now I don't know if 3D printing rocket parts actually works and I have my doubts but this startup is currently testing the process and they will figure out its limits. That's the whole point of R&D.
- Etheryte 2y ago
  For context, 3D printing rocket parts is incredibly common, even student teams often use printed nozzles and such. The linked article is about printing a whole engine as a single piece, which is a different beast.