I'm curious as to the QA system used here. I imagine with proper simulation this should have been catchable. I wonder if SpaceX's low cost approach means cutting certain corners and situations like these where catchable issues make it into the wild because of the difficulty of rocketry in general with the added difficulty of cheap spaceflight tacked on.
I really hope they didn't just find themselves in a STS-51-L moment where it'll take months to truly iron out the root issues. Thank goodness there was no loss of life and SpaceX's stack isn't man rated yet.
I imagine this level of simulation might not be entirely feasible yet. Maybe for the lack of trying or budget. In a growth industry or one powered by both commercial and technical pressures, it may be difficult to sit down and build something like this out. From a more practical point of view, it may make sense to just let things explode than spend years running expensive simulations instead of building things, launching, and collecting paychecks.
Part of what makes the idea of bringing the first stage back to the pad so important is that we so rarely get to use the same engines multiple times in the field (where all the really nasty reality checks are done). Being able to reuse stages allows us to far better model how they will perform in the future. Otherwise, we're using test beds to feed parameters into sims to inform our launches; it's good practice, but more physical evidence is always better.
Frankly, no. You're wildly underestimating the complexity of the system.
We don't know in this specific instance, but generally this is just fundamentally not true. You're way over-estimating the abilities of computers and way under-estimating the complexity of these systems.
I haven't been down voting your comments, but if I had to guess as to why other people are, it's because comments like this are typical of a certain kind of arrogance. I think we've all had that moment where we think "what, that sounds easy!" about someone else's problems, only to realise when we try to solve it ourselves we're suddenly confronted with that problem's true complexity. These are very smart people working on these problems, and your comments come across as if you're suggesting they've been negligent–while that could be true, it wouldn't be my first guess. Rocket science is hard, and things go wrong, and no amount of computing can change that.
You have literally hundreds of systems working in concert and tied to more hundreds of physical components coming under extreme temperature and pressure conditions, some of which can interact in the weirdest and most unexpected ways - certainly not ones you'd always think to model. The chances that any one of those does something unexpected is not low, and the chances that it cascades into a much larger failure is non-significant.
edit: It's also sometimes a human problem - thousands of people working on this together, and all sorts of different incentives. Here's a famous example of a failure, and the PR kerfuffle that ensued: https://en.wikipedia.org/wiki/Rogers_Commission_Report
Quoth Feynman:
"It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management. What are the causes and consequences of this lack of agreement? Since 1 part in 100,000 would imply that one could put a Shuttle up each day for 300 years expecting to lose only one, we could properly ask "What is the cause of management's fantastic faith in the machinery? .. It would appear that, for whatever purpose, be it for internal or external consumption, the management of NASA exaggerates the reliability of its product, to the point of fantasy."
This is exactly what computers are for: doing hard stuff we can't do on paper or just by real world prototype testing. I imagine this is a hard problem, but it may be so because from a time/budget perspective it may just make financial sense to let stuff blow up now and again, than build out such a system.
I kinda see this as the difference between writing typical code versus writing code that's deterministic. The former is cheaper/faster but the latter is safer but more expensive and slower. In growth industries or when you have a strict schedule on your back, the slower approach is often ignored.
>Quoth Feynman
Feynman died when the hottest CPU was the 386. We simply have the capabilities, at least in hardware, for non-trivial simulation that during Feynman's time would have required CPU resources ridiculous to even speculate about. Safe assumption in Feynman's world (1918-1988), at least in regards to technology and engineering, may not be safe assumptions in our world. The same way our assumptions today won't make too much sense for our grandchildren. They might be bewildered by the idea that rocket fails were constant and common, the same way I'm bewildered by things like hot-days causing vapor lock to shut down old cars or, say, occasionally tuning a carburetor. We have electric gas pumps and computer controlled fuel injectors now.
edit: to reply to jacquesm. That's a pretty bold claim about O-rings. We fully understand the materials they're made of, their typical decays, etc. They're not magic. If someone wanted to make a top-down simulation that included, well, everything, it certainly seems possible to me, and while certainly not perfect, if done right, should provide positive outcomes. The real question is, what's the incentive? Spend billions and years doing this for one system (which may be old or even obsolete by the time the simulation is complete) or just accept the occasional preventable loss. Seems the latter approach just makes more sense financially, but that doesn't mean the former approach must be impossible. Many things are possible that just aren't incentivized.
I'm not even talking about jackquesm's note about the failure mode, either. Just real insidious errors in manufacturing that can't be detected in any sort of reliable, sane way. Even the Challenger's o-ring wasn't guaranteed to fail, and indeed most didn't. In fact, most of that entire o-ring didn't fail.
I've seen some really freaky things amplify what are essentially chaotic edge cases. You can certainly figure them out, but you'd never get anything done for any level of affordability in time for any ship date if you didn't just calculate risk and go ahead.
TL;DR: risk is always there because the world's imperfect. At best you just tighten the statistical confidence, but that's super hard.
No, we don't. While we can do this very well for the "high level" physics, we can't do it very well for the "low-level" physics such as -- for one example -- the detailed effects of turbulent flows (both outside of the craft and inside of the plumbing), which are usually modeled based on averages of aggregate effects and random models because a detailed deterministic model is impractical (both, IIRC, because doing so at the level we could in theory do is too computationally expensive to do in practice, and because even our theory is pretty limited when it comes to turbulence.)
> I imagine with proper simulation this should have been catchable.
Its possible that there is some level of simulation which would have caught this (we won't know unless they figure out with enough detail what the problem was), but even if it would have been possible, it may not have been cost effective.
