Ziggurat
Penultimate Amazing
- Joined
- Jun 19, 2003
- Messages
- 59,291
I'm not completely convinced about their analysis of the new water deluge system.
I think their analysis is simply wrong. They make several assumptions that I don't think are at all justified. For one, they assumed that the amount of water pumping through the plates has to match the deluge system used by Artemis. Even assuming that SpaceX wants to use that much water (and it looks like they don't), it doesn't all have to flow through the plates. Second, they're interpreting a statement by Musk about the water pressure pushing against the rocket exhaust pressure as meaning a lot more than I think it actually means. They seem to think that Musk is claiming that the water spray from the plates will act like a water rocket to counter the booster rockets. But I don't think that's at all what Musk is saying. I think all he's saying is that the internal water pressure has to exceed the gas pressure on top of the plates so that water comes out the plates. That water doesn't have to form a counteracting rocket of its own. It's fine if that water layer stays on the surface of the plates. Hell, it may even work if there's NO liquid water on the surface, if you're just getting water vapor coming out the holes, as long as you're pushing enough water into the sandwich to keep it cool enough.
As for thermal expansion, he seems to be going off third party speculative renders to conclude that there's nothing in the design to account for thermal expansion. I wouldn't consider that reliable.
He's also stuck on the whole cement thing, and how fondag isn't the strongest cement out there. Which, yeah, looks like it's true: it doesn't have the strongest compressive strength. But it's got really good thermal resistance, which was the expected limiting factor. And I don't think he understands how the concrete failed. It didn't fail because the concrete just crumbled under the immense pressure because the compressive strength wasn't high enough. What appears to have happened is that the foundation under the slab got compressed, allowing the concrete to crack under a bending load, and once it cracked, that allowed high pressure to get in under the slab and start pushing stuff up from underneath. One of the big things SpaceX is doing with the reconstruction which isn't getting a lot of press is reinforcing the foundation. They're putting in much stronger pillars under the base than they previously had. If the foundation doesn't sag, then you won't get that same failure mode.