It’s hard to be sure if the holes are angled at all. I think they probably are, though at the same time I don’t think it matters much. Even if they’re at a 45-degree angle, if the thrust is pushing down so that the stagnation point is 2 meters up (for example), then horizontally the water has only moved 2 meters. The pad is so large that it just doesn’t matter much.
Here’s another video of the showerhead test:
Some of the streams look a bit angled (you can see this as the water tails off), but compared to the overall level of water, I think it’s pretty much irrelevant.
Seems like they have flow issues or I don’t understand the video: if you look at :31, the flow on the opposite side of the pad is twice as high as the dwindling near nozzles. I’m probably wrong – maybe those are center nozzles, but it looks weird.
I agree that it’s a bit uneven, but that’s to be expected. The water is plumbed in from three out of the six sides. There will be a pressure drop from one side to the other. While I’m sure they accounted for this to some extent, the modeling isn’t going to be perfect. They just need sufficient pressure across the whole surface, not for it to be perfectly even.
Glad to! But the credit surely goes to the people recording events and actively figuring this stuff out. I do try to keep abreast of things and put together the pieces from various sources, but when it comes to the nitty gritty (like producing the render above), others are putting in way more effort. It’s sorta remarkable how Starbase has created this hive of secondary media activity. And it’s all better sourced than typical media coverage.
Wait, what? They’re pressurizing all that water with gas? Why not just build tall water towers with big pipes - open all the valves at once and kablooey! ? Isn’t that how NASA did it? ETA: wiki says NASA used a gravity fed system. Probably I’m misunderstanding your comment.
Yep, they’re using tanks at ground level and gas to pressurize them. I assume this is due to the required pressure: they’d need a 160 meter water tower for 16 bar pressure. That’s not a small thing. So they just use gas instead.
There was a vent test a couple days ago, but I can’t seem to find a video link right now…
Well, they can always increase the pressure further to account for variation. To some extent, the unevenness will be reduced when the rocket is actually firing. The unevenness is probably mostly coming from the pressure drop as the water flows through the plate (which has a bunch of internal supports that restrict flow). Just like electricity and voltage drop, pressure drop is proportional to the amount of flow. When the rocket is firing, the flow will be reduced (assuming constant head pressure). So less pressure drop across the plate, and therefore more even pressure as it comes out the holes.
We can ballpark the stagnation pressure as the thrust divided by the area. That’s 74.5 MN divided by the area of a 9-meter circle. That’s 1.17 MPa, or 12 atmospheres. Take thrust variation into account (the pressure will be higher when directly under an engine) and bumping that to 16 (or even much higher) seems reasonable.
I’m not sure how the pending lawsuit affects anything here. The judge hasn’t issued an injunction or anything. But is the FAA nevertheless obligated to wait until any legal actions are resolved? I haven’t even seen any speculation on the topic. Ideally, it would just be business as usual until the judge issues some order, but I really have no idea.
I like the extra shielding. The new pad will help a great deal too, but I think they’ll still want to minimize any chance at all at debris causing engine failures. Gives it a nice, clean look as well. Though if you look closely you can see some cables attached with 4000-mile-per-hour-tape (I’m pretty sure they’ll remove this before flying)
Those streams are now going over the elevation of the engines. Though now they’re much more clearly pointed outward. Supposedly, there’s still another tank on the way, so this might not yet be at full volume.
You want a layer of water between the pad & the engines. You don’t want to be hosing the underside of the engines and rocket body with high pressure water. Exactly how you aim to achieve both those things isn’t obvious to the likes of me. But that’s what the engineers are trying for.
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