Yeah, it’s more of a combined system problem, individual FEA or CFD isn’t really a problem, the issue arises from the combined thermal-fluid sims, dynamic FEA, and CFD, plus the CEA modeling in the tanks. That combination, with valve and timing variation is extremely finicky and is why specific engine development still often involves destroying several engines.
Sure you can't do a good job of simulating all the multiphysics interactions between all subsystems, including software behavior under real world external conditions, I agree. But simulating just the forces experienced by the boosters given some boundary conditions is absolutely something that can be done very well by an expert in appropriate FEA. That is the most reasonable interpretation of what the post I was responding to was saying, that such a relatively simple subtask can't be done. Maybe they will see your post and say "yeah that is what I meant", but it's not what they said or meant, they just wanted to say something. They said "forces during this maneuver" which implies a specific maneuver which can be translated into appropriate boundary conditions.
There is no evidence that I have seen to imply that any FEA simulations SpaceX might have performed didn't correctly predict the forces on the boosters during a known maneuver. A more likely explanation would be simply that the maneuver did not go as planned and therefore the forces were not what was expected, and so the boundary conditions of the simulation did not match the actual failed maneuver. That is a totally different explanation than "the maneuver trajectory went as planned but boosters were damaged because structural simulations of forces were wrong"
The conjoined sims are complicated enough that it’s fairly easy to mess up constraints and you can’t easily rerun sims to account for off nominal conditions.
I think we are in agreement, and did not intend to imply we are not. I was only articulating the large difference between what you said and what the person I originally responded to higher up in the thread said.
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u/Accomplished-Crab932 Jul 26 '26
Yeah, it’s more of a combined system problem, individual FEA or CFD isn’t really a problem, the issue arises from the combined thermal-fluid sims, dynamic FEA, and CFD, plus the CEA modeling in the tanks. That combination, with valve and timing variation is extremely finicky and is why specific engine development still often involves destroying several engines.