OT: SpaceX Starship/Booster test flight 04/20/23

[eKretz]

Heat green concrete, or just about any concrete, superheated steam will blow it to bits, Big Bang,
There are refractory concretes that work, after preheating for several days or weeks but not in thick sections, vibrated reinforced concrete isn’t porous enough to release the steam
Mark

I've mentioned this before here and been pooh-pooh'ed over it. Proof is in the pudding.

 

[crickets]

I've mentioned this before here and been pooh-pooh'ed over it. Proof is in the pudding.

Not necessarily. They have conducted quite a few static fires at that pad and didn't destroy it, which is probably what encouraged them to risk a launch. If it were so black and white, the issue would reveal itself when they did the static fire with most of the engines running at the same time.

 

[Milland]

If it were so black and white, the issue would reveal itself when they did the static fire with most of the engines running at the same time.

The problem with that static fire test was:

1) Only the one "all engine" (31 of 33) test.

and

2) Not at full power (just 50%)

My take is that the actual thermal load difference between what they called half throttle and full was more than double, and the intensity basically ramped the stress on the concrete to well over what it could handle. And we saw the results...

 

[crickets]

The problem with that static fire test was:

1) Only the one "all engine" (31 of 33) test.

and

2) Not at full power (just 50%)

My take is that the actual thermal load difference between what they called half throttle and full was more than double, and the intensity basically ramped the stress on the concrete to well over what it could handle. And we saw the results...

Of course, they exceeded the engineering limits when they went for launch. I actually don't know if they had the engines at 100% on takeoff, or if they were throttled below full power yet above 50% (plus we should remember the duration - static fires are 2-3 times shorter than liftoff). Either way, the point is it wasn't obvious they'd exceed the limit, or there would be no launch. Real engineers work there, they just pushed it a bit too far

 

[jim rozen]

Another nail-in-coffin issue: this booster had no hold-downs. Saturn 5 launches had the engines go mainstage full thrust right away, and then hold-downs were retracted to allow the liftoff. The rocket that destroyed the launchpad here had no hold-downs, so they throttled the engines up slowly over a relatively long time, giving them a longer time to beat up the pad.

After the hold-downs on the saturn launches retracted, the boster was still retained briefly on the pad by soft bolts that were extruded through sockets, to attenuate the shock of the launch.

 

[boslab]

I don’t know what they did, test firing might have cooked the concrete a bit but the drying ( cyclic kind of process) strength is reached at about 28days but moisture in the core takes a hell of a time to clear, mainly the fact that vibrated concrete holds moisture in, curing castable concrete in furnaces takes often weeks to do , gentle at first, ramping up slowly, even then I’ve seen reheat furnaces blow out after a week of preheat when the furnace was ramped up to operating temp, bits of concrete sticking up like the titanic sinking, steel mangled. Could have been a wetter mix when poured or som such, though test cubes are religiously cast and tested to see what the concrete is up to, as I said 28 days is the magic figure for strength but moisture? Vary variable, but it is going bang if it’s new and not dry, that you can take to the bank as they say.
Either way I hope they sort themselves out, I find the whole thing inspirational in what feels like the most depressing world I could not have imagined if I tried,
Mark

 

[Milland]

Another nail-in-coffin issue: this booster had no hold-downs. Saturn 5 launches had the engines go mainstage full thrust right away, and then hold-downs were retracted to allow the liftoff. The rocket that destroyed the launchpad here had no hold-downs, so they throttled the engines up slowly over a relatively long time, giving them a longer time to beat up the pad.

There are hold downs on the pad, what are essentially pinch clamps distributed around the periphery of the Booster that are hydraulically released when it's Go-Time.

Major elements of Starship Orbital Launch Pad in place as launch readiness draws nearer - NASASpaceFlight.com

With the maiden orbital flight of Starship approaching, Orbital Launch Pad A in Starbase, Texas,…

www.nasaspaceflight.com

"The launch table has 20 separate hold-down clamps that attach to the bottom of the booster for static fires and launches from the orbital pad. For launches, these hold-down clamps will release once all the engines on the booster are at nominal thrust."

 

[jim rozen]

Maybe they did, and maybe they did not have the hold-downs. From the exact same article:

"The water deluge system will spray water onto the bottom of the launch mount and on the ground to help lessen the sound waves of 29 and eventually 33 raptors firing at full thrust so that the sound waves do not damage the rocket or the pad."

No flame trench, no water deluge. No hold-downs? I think that PR article might have been 'wishful thinking.'

 

[Milland]

No flame trench, no water deluge. No hold-downs? I think that PR article might have been 'wishful thinking.'

They had hold downs, no question. Thrust was at 100% for 3 seconds or more before liftoff*.


*Well, 100% minus the damaged engines...

 

[jim rozen]

Then they also had water deluge? Per the same article?

No.

 

[DDoug]

More importantly...How does Greta feel about all this ?

 

[Milland]

Then they also had water deluge? Per the same article?

No.

Not sure why you need to hang on to this so tightly - almost like booster hold down clamps...

 

[CAMasochism]

Not sure why you need to hang on to this so tightly - almost like booster hold down clamps...

I really don't know what the hang up is. They are trying new things, seeing what they can and cannot get away with.

It's acting like HSS endmills are good enough because it's always worked and why change what you know works rather than pushing it till it breaks then back off 10%.

 

[Milland]

It's acting like HSS endmills are good enough because it's always worked and why change what you know works rather than pushing it till it breaks then back off 10%.

I use high-carbon endmills that I hand-forge myself, then sharpen on a treadle grindstone.

 

[CAMasochism]

I use high-carbon endmills that I hand-forge myself, then sharpen on a treadle grindstone.

Did you go to the quarry and pick out the grindstone yourself?

 

[Milland]

Did you go to the quarry and pick out the grindstone yourself?

No, just granite up here. I had to travel to Japan to get my abrasive, because I needed that extra-keen edge.

 

[empower]

well done chaps! gave me a good chuckle

 

[jim rozen]

"...hang on to this so tightly..."

The article has incorrect information.

 

[Milland]

"...hang on to this so tightly..."

The article has incorrect information.

Argh...

OK, I'll call Elon and get a confirmation. Perhaps it's static electricity that holds the Booster down, or staff volunteers...

 

[standardparts]

News reporting Biden Administration's FAA has grounded SpaceX pending investigation over environmental concerns stemming from the last launch.
This will be fun to watch. Wonder if the FAA in D.C. is handling this or dropped it in the lap of local FSDO.