alt Hacker NewsI was wondering about that, so I looked up the heat shield issues. It seems like their solution was very defensible and there was every reason to believe it would work out just fine. The plan that did not work as they wanted had a new idea, a double re-entry, and when the results were concerning they backed off to using a traditional single re-entry. That seems like a legitimate fix?
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thegrim33 • today at 1:29 AM
Yes, but it was the biggest opening for propagandists to latch on to for demoralizing and spreading fear/uncertainty/doubt about the mission.
Scott Manley went into the details in a recent video.
The reason the heat shield failed was due to gas buildup inside the ablative material. This was due to the skip reentry profile they used, where the craft does a single skip (as in skipping stones) during reentry. The high bounce caused the shield to be heated enough that the heat penetrated the material causing gas release but not enough that the material ablated. Thus gas would build up deep inside up until it caused large chunks to break off. They could reproduce this in tests.
The fix was two-fold. First they lowered the bounce height, so a much less pronounced skip, avoiding the lowered heating of the shield. And they tweaked the material formula a bit so it was more porous, allowing subsurface gas to escape rather than build up.