SpaceX Texas launch site Discussion and Updates - Thread 12

[FutureSpaceTourist]

[Tangilinear Interjar]

I wonder if the concrete that they are pulling up is old stuff that they didn't replace before. It would make sense to only replace some of the damaged concrete with Fondag and then test it to make sure it does the job adequately before replacing everything.

Also the color of what they are removing seems very brown but the data sheet on Fondag says it's a very dark grey.

[InterestedEngineer]

On the Stage 0 churn at BC, I've always found it to be unsurprising, given the long term objective of being able to have Starships (but not Boosters) land at, and perhaps take off again from, relatively austere off-world sites.

So in addition to "best part is no part",
there might also have been a bias for doing without:
- a Grand Canyon class flame trench,
- a tsunami-class deluge system, and
- Maginot Line-class GSE protection.

Yes, 110%.

Turns out the physics never required a flame trench for all the history of rocketry, because flow redirection can be done using the characteristics of the flow itself impinging on a perpendicular surface, which is a senior level college problem in fluid dynamics classes in mech. engineering and physics.  Odd, that that it took a company that is an expert in CFD to finally utilize the effect.

A bonus part about "best part is no part" is the trench and deluge system would have had a pretty significant environmental impact, the trench being below water table line and dumping of huge amounts of fresh water into a semi-saline environment.

I think the non-Maginot-line class GSE optimism has to await an actual launch to see if it works

Flow redirection isn't the only (or even the main) purpose of flame trenches (or water suppression, for that matter). And plenty of orbital launches have occurred from pads without them. Saturn IB even got two kicks at that can: the first being an elevated pad with a diverter sat underneath, and the second being the infamous 'milkstool' sat far above LC-39A.

One of the main purposes of flame trenches and water suppression is to prevent blast and debris hitting the spacecraft.

If the latest slow-mo video doesn't persuade you that problem is solved with the OLM, or the video on the math of how that works, then not much will.

The biggest barrier to "best part is no part" are those who insist without evidence that the part is needed, and use FUD to try and keep the part, or use everyone's prior mistakes to try and keep the part.   I've seen this dozens of times in my career.

[edzieba]

On the Stage 0 churn at BC, I've always found it to be unsurprising, given the long term objective of being able to have Starships (but not Boosters) land at, and perhaps take off again from, relatively austere off-world sites.

So in addition to "best part is no part",
there might also have been a bias for doing without:
- a Grand Canyon class flame trench,
- a tsunami-class deluge system, and
- Maginot Line-class GSE protection.

Yes, 110%.

Turns out the physics never required a flame trench for all the history of rocketry, because flow redirection can be done using the characteristics of the flow itself impinging on a perpendicular surface, which is a senior level college problem in fluid dynamics classes in mech. engineering and physics.  Odd, that that it took a company that is an expert in CFD to finally utilize the effect.

A bonus part about "best part is no part" is the trench and deluge system would have had a pretty significant environmental impact, the trench being below water table line and dumping of huge amounts of fresh water into a semi-saline environment.

I think the non-Maginot-line class GSE optimism has to await an actual launch to see if it works

Flow redirection isn't the only (or even the main) purpose of flame trenches (or water suppression, for that matter). And plenty of orbital launches have occurred from pads without them. Saturn IB even got two kicks at that can: the first being an elevated pad with a diverter sat underneath, and the second being the infamous 'milkstool' sat far above LC-39A.

One of the main purposes of flame trenches and water suppression is to prevent blast and debris hitting the spacecraft.

If the latest slow-mo video doesn't persuade you that problem is solved with the OLM, or the video on the math of how that works, then not much will.

Sub-scale static fire != launch.

In addition to the more than double the amount of engines firing (and possibly greater than double thrust, as we do not know definitively if the 11 engine static fire was all engines at 100%, or if individual engines started at 100% then throttled down to some lower throttle range for the rest of the test), a launch also involves the vehicle lifting off of the pad. That means the nice spherical-cow flow pattern is disrupted by having a varying path length, varying thrust angle as engine vectoring has its biggest challenge of stabilising the stack at near 0 velocity and maximum mass, and a honking great steel donut impinging into the flow path shortly after liftoff.

Everyone hopes it'll work, but all three previous super-heavy-lift vehicles to fly from LC-39 (Saturn V, STS, and now SLS) started out with "bah, you're overegging it, it'll be fine, the numbers all work out!" for the first launch, followed by having to beef up suppression systems (and repair damage) for all subsequent launches.
History is not on the side of underestimating the launch environment.

[alugobi]

Alternative #3: "wait and see what happens".

[tgr9898]

Alternative #3: "wait and see what happens".

Have you met The Internet before?

[alugobi]

Lab and NSF cam are showing a concrete pumper filling the form atop the berm.

[alugobi]

Alternative #3: "wait and see what happens".

Have you met The Internet before?

Is that the thing where somebody is wrong so I can't go to bed yet?

Edit:  I knew I had that somewhere.

[InterestedEngineer]

Everyone hopes it'll work, but all three previous super-heavy-lift vehicles to fly from LC-39 (Saturn V, STS, and now SLS) started out with "bah, you're overegging it, it'll be fine, the numbers all work out!" for the first launch, followed by having to beef up suppression systems (and repair damage) for all subsequent launches.
History is not on the side of underestimating the launch environment.

Wait, you are suggestion SpaceX might have to iterate on Stage 0?

I'm pretty sure that's their plan.

Given some very highly planned, over-specified, the-more-parts-the-better launch systems have failed, the best method is to go faster and see what fails.   Go with as few parts as possible as the first goal, add parts later.

[DigitalMan]

Everyone hopes it'll work, but all three previous super-heavy-lift vehicles to fly from LC-39 (Saturn V, STS, and now SLS) started out with "bah, you're overegging it, it'll be fine, the numbers all work out!" for the first launch, followed by having to beef up suppression systems (and repair damage) for all subsequent launches.
History is not on the side of underestimating the launch environment.

Wait, you are suggestion SpaceX might have to iterate on Stage 0?

I'm pretty sure that's their plan.

Given some very highly planned, over-specified, the-more-parts-the-better launch systems have failed, the best method is to go faster and see what fails.   Go with as few parts as possible as the first goal, add parts later.

At the rate SpaceX is going I wonder how long it would take them to spend a similar amount to what was spent for LC-39B + ML and how many pads would they have to build? The cost of the various approaches is interesting.

[FutureSpaceTourist]

https://twitter.com/csi_starbase/status/1600723036646170624

The reason the OLM has to get repainted after every Static Fire attempt, is because the paint is designed to be ablated away. This protects the underlying steel from the thermal energy.

Protection against salt water is a distant secondary function....far from a primary reason.

twitter.com/calengray/status/1600723287331307520

How will this work long term with rapid reusability?

https://twitter.com/csi_starbase/status/1600723593821765632

I don't believe rapid reusability is possible at Starbase. It might be at Pad39 though.

[InterestedEngineer]

https://twitter.com/csi_starbase/status/1600723036646170624

The reason the OLM has to get repainted after every Static Fire attempt, is because the paint is designed to be ablated away. This protects the underlying steel from the thermal energy.

Protection against salt water is a distant secondary function....far from a primary reason.

twitter.com/calengray/status/1600723287331307520

How will this work long term with rapid reusability?

https://twitter.com/csi_starbase/status/1600723593821765632

I don't believe rapid reusability is possible at Starbase. It might be at Pad39 though.

How much ablation can a thin layer of paint provide?   The mass can't be more than a few hundred kg spread over 10s of square meters.   That isn't very many joules dissipated, whether kinetic or thermal

I don't get the physics on that assertion.

[edzieba]

https://twitter.com/csi_starbase/status/1600723036646170624

The reason the OLM has to get repainted after every Static Fire attempt, is because the paint is designed to be ablated away. This protects the underlying steel from the thermal energy.

Protection against salt water is a distant secondary function....far from a primary reason.

twitter.com/calengray/status/1600723287331307520

How will this work long term with rapid reusability?

https://twitter.com/csi_starbase/status/1600723593821765632

I don't believe rapid reusability is possible at Starbase. It might be at Pad39 though.

How much ablation can a thin layer of paint provide?   The mass can't be more than a few hundred kg spread over 10s of square meters.   That isn't very many joules dissipated, whether kinetic or thermal

I don't get the physics on that assertion.

Intumescent paints have been used for fire protection for almost a century. There is a wealth of information available on how they work, and they do indeed work.

[baking]

Intumescent paints have been used for fire protection for almost a century. There is a wealth of information available on how they work, and they do indeed work.

But there is no way intumescent paint would be used in this application.

[FutureSpaceTourist]

https://twitter.com/vickicocks15/status/1600768547315077120

What an absolute rat's nest! I hope #SpaceX find a way of simplifying this on future versions of the #OLM. This one at #Starbase is a mess! And they keep adding more! Crazy complicated!
@LabPadre  #Rover2Cam

[InterestedEngineer]

https://twitter.com/vickicocks15/status/1600768547315077120

What an absolute rat's nest! I hope #SpaceX find a way of simplifying this on future versions of the #OLM. This one at #Starbase is a mess! And they keep adding more! Crazy complicated!
@LabPadre  #Rover2Cam

there are three lines of high pressure startup gases going up the OLM (LOX, CH4, N2, perhaps helium).  Each of those feeds ~11 engines one at a time.  That's 11*3 = 33 high pressure on/off switches per cabinet or set of cabinets.

In theory.

Now, to find a hi-res picture and count how many are actually there.

[Nomadd]

 I made a good living cleaning up rats nests and was impressed with how neatly everything is laid out on the mount. Complex doesn't have to equal sloppy.

[InterestedEngineer]

I made a good living cleaning up rats nests and was impressed with how neatly everything is laid out on the mount. Complex doesn't have to equal sloppy.

And none of that complexity flies either.   (we hope)

[alugobi]

Not screwing around on the berm.  Forms removed from the first pour, and going up on the wet end.

This is going to chop off some of the view of the launch mount from Rover Cam 2.

[FutureSpaceTourist]

https://twitter.com/rgvaerialphotos/status/1601429556501811201

SpaceX must have seen @CSI_Starbase tweet