totm nov 2023 SpaceX Discussion Thread

[Pthigrivi]

I’ll be kind. I guess some folks are just more credulous than others. You do you. 

[Meecrob]

3 hours ago, Pthigrivi said:

The issue is that it underscores the general mental/cognitive incompetence of the person running this. The galactic stupidity of corporate misadventures like cybertruck and blowing up the OLM for no conceivable reason are illustrated as part of a pattern. Hair plugs don't fix dumb. 

https://www.thedailybeast.com/elon-musk-gives-his-craziest-interview-yet-with-cnbcs-david-faber?ref=home?ref=home

Last time I checked the buck stops at Gwynne Shotwell, not Elon.

Edit: What I mean is that its cool to hate on Elon and all, but that seems to be clouding peoples judgement.

Edited May 17, 2023 by Meecrob

[RCgothic]

Bottom lines:

Even if Raptor V3 can't operate reliably at 350bar chamber pressure, it'll operate at 300bar far more reliably than Raptor 2.

Even if SpaceX can't get full reuse to work, the disposable elements of a Starship would only be a few million more per launch than an F9 upper stage plus fairings. It'll be cheaper per kg by at least a factor of 2, guaranteed, and they don't even have to drop prices because SpaceX have already captured 90% of the market at their current prices. And if they can get full and rapid reuse to work, they win full stop. 

Private capital never has to be amortised. As long as the interest payments are affordable and there's always someone willing to lend when the old loans come due, development costs are irrelevant.

The owner's behaviour could be where SpaceX comes unstuck and it's hard not to be aware of his latest escapades, but discussing the details of those is against forum rules, so. Gwynne Shotwell has always run a tight ship and there's no reason yet to think that won't continue. Kathy Leuders' hiring to run Starbase is a good sign IMO.

Edited May 17, 2023 by RCgothic

[CBase]

29 minutes ago, RCgothic said:

Even if Raptor V3 can't operate reliably at 350bar chamber pressure, it'll operate at 300bar far more reliably than Raptor 2.

Without knowning the failure modes this is a daring conclusion. However from my professional expierence: Increasing reliablity is hard work but makes no good tweet So we shouldn't think it is not happening, because Elon is not tweeting it.

[RCgothic]

3 minutes ago, CBase said:

Without knowning the failure modes this is a daring conclusion. However from my professional expierence: Increasing reliablity is hard work but makes no good tweet So we shouldn't think it is not happening, because Elon is not tweeting it.

Most of what we've been told about Raptor's reliability is that it "super wants to melt".

Heat flux goes with the 4th power of pressure, so 350 would be generating nearly twice as much heat flux as 300. If the problem with reliability is indeed heating, then firing an engine successfully at 350bar for 40s demonstrates significant progress.

That B7 took off at only 90% throttle is evidence that reducing power helps nurse the engines. 

[JoeSchmuckatelli]

7 hours ago, Pthigrivi said:

The issue is that it underscores the general mental/cognitive incompetence of the person running this. The galactic stupidity of corporate misadventures like cybertruck and blowing up the OLM for no conceivable reason are illustrated as part of a pattern. Hair plugs don't fix dumb. 

https://www.thedailybeast.com/elon-musk-gives-his-craziest-interview-yet-with-cnbcs-david-faber?ref=home?ref=home

PayPal, Tesla and SX belie that conclusion. 

You could make an argument about his political choices or personal shenanigans all day - but if you conclude from that mental /cognitive incompetence? 

I think you're missing something in your analysis 

[tater]

 

[sevenperforce]

Some interesting developments:

With this closer view, I can see that it's actually ONE steel plate with channels cut into it, not two plates with an internally-pressurized space. That should help significantly with the structural integrity of the plate and prevent ballooning at the center. 

[RCgothic]

1 minute ago, sevenperforce said:

Some interesting developments:

With this closer view, I can see that it's actually ONE steel plate with channels cut into it, not two plates with an internally-pressurized space. That should help significantly with the structural integrity of the plate and prevent ballooning at the center. 

I don't think that's right. It's been modelled in a few videos by people who should know as two plates spaced by girders with circular holes through them.

I think you'd have to custom-order plates that thick from a foundry, and the machining costs would be ridiculous compared to just fabricating it.

[RCgothic]

Like this

 

[sevenperforce]

36 minutes ago, RCgothic said:

I don't think that's right. It's been modelled in a few videos by people who should know as two plates spaced by girders with circular holes through them.

I think you'd have to custom-order plates that thick from a foundry, and the machining costs would be ridiculous compared to just fabricating it.

Oooh, I get it now. Yeah I guess I was wrongly assuming that the plates were solid steel.

[sevenperforce]

@RCgothic, are we thinking that the pipes running lengthwise through the assembly will have holes in the side to allow the entire assembly to fill with pressurized water, which then would exit through the holes on top?

EDIT: Wait, no, now I see the pipe holes coming up underneath. Is it a flow-through design? I'm having trouble visualizing the water path.

Edited May 17, 2023 by sevenperforce
Realized something else

[RCgothic]

37 minutes ago, sevenperforce said:

@RCgothic, are we thinking that the pipes running lengthwise through the assembly will have holes in the side to allow the entire assembly to fill with pressurized water, which then would exit through the holes on top?

EDIT: Wait, no, now I see the pipe holes coming up underneath. Is it a flow-through design? I'm having trouble visualizing the water path.

I think the idea is that the through-pipes feed the next plate section along, and the vertical pipes feed this plate section.

[JoeSchmuckatelli]

So... The new plan is to use tons of water to quickly erode the sand around the launch table during takeoff? 

B/c if they don't light the candle on time and convert it to steam... Won't that be the result? 

[StrandedonEarth]

I would expect them to have some sort of collection system to recapture and reuse the runoff, since I would assume fresh water isn’t exactly abundant around there, and I don’t think that they would want to use seawater. 

Of course, I could be totally wrong about that…

[JoeSchmuckatelli]

24 minutes ago, StrandedonEarth said:

I would expect them to have some sort of collection system to recapture and reuse the runoff, since I would assume fresh water isn’t exactly abundant around there, and I don’t think that they would want to use seawater. 

Of course, I could be totally wrong about that…

Every coastal launch site deluge system article I've read has talked about the corrosive nature of sea water.  I'm guessing they're aware of the consensus. 

 

It's just when I think about not only the design of the Table and the area around it - I'm having a hard time figuring how they'll contain and collect that much water w/o some kind of trenching - which they apparently don't want to do b/c of the water table. 

And yet - aside from acoustic concern - I can't figure out how a water filled pool around the table could be a bad thing 

...unless building a pool effectively guarantees focusing shockwaves back at the vehicle 

[sevenperforce]

3 hours ago, JoeSchmuckatelli said:

So... The new plan is to use tons of water to quickly erode the sand around the launch table during takeoff? 

B/c if they don't light the candle on time and convert it to steam... Won't that be the result? 

The actual amount of water being used may not be THAT extreme, all things considered. It will be a lot, of course, but possibly not as much as in some other designs. They are going to use blow-down from a pressurized gas reservoir to force the water through rapidly during ignition and liftoff.

[mikegarrison]

16 minutes ago, sevenperforce said:

The actual amount of water being used may not be THAT extreme, all things considered. It will be a lot, of course, but possibly not as much as in some other designs. They are going to use blow-down from a pressurized gas reservoir to force the water through rapidly during ignition and liftoff.

I don't understand why they thought they didn't need an extreme amount of water in the first place. They are obviously releasing an incredible amount of thermal energy, and I would think they they need a lot of mass flow to carry it away.

[FleshJeb]

9 hours ago, mikegarrison said:

I don't understand why they thought they didn't need an extreme amount of water in the first place. They are obviously releasing an incredible amount of thermal energy, and I would think they they need a lot of mass flow to carry it away.

That's because you're from an engineering discipline with low risk tolerance and a robust culture.

I'm from the small consulting Civil Engineering side. This had all the hallmarks of, "enthusiastic junior engineers with inadequate mentoring and supervision."  A lot of firms coast on this because we have well-developed standards and regulations, high safety factors, and mostly low-stakes. Plus contractors with a lot of experience who are perfectly willing to call us idiots and fix it with a change order.

I have a hunch Leuders was brought on to stop this kind of embarrassing catastrophe from happening again. She has an excellent skillset for it.

[tater]

 

[tater]

Tonight:

 

[tater]

 

[tater]

 

[darthgently]

1 hour ago, tater said:

 

Definitely holes in the top surface for the exit of the water directly into the furnace, so "film" and evaporative is very much involved.  Not just heat transfer of top plate involved as some have fretted over

[tater]