totm nov 2023 SpaceX Discussion Thread

[Spaceception]

Ouch

 

At least SN5 is nearly ready, and SN6/7 are on the way. Though I'd bet they'll hold off on testing, and slow construction to see what went wrong with SN4.

[Burning Kan]

mass simulator have hopped!

R.I.P SN4 and raptor20 hope goes for SN5 soon.

god bless doug and bob

 

live link:

 

Edited May 29, 2020 by Burning Kan

[Guest]

[EchoLima]

10 minutes ago, Spaceception said:

At least SN5 is nearly ready

Starship is dead, long love Starship!

[kerbiloid]

Why do they call it "static"?
It looks rather dynamic.

[CatastrophicFailure]

Spoiler

 

Well... Starship has officially launched its first payload at least... 

[RealKerbal3x]

Noooooooooooooooooooooo!

That was an awesome explosion though

[Treveli]

Lord Murphy needed a sacrifice to appease him before tomorrows launch attempt.

[ExtremeSquared]

I'm just sort of worried it's getting heavier every time a failure is addressed. There comes a point in beefing up the structure where mission capabilities need to be adjusted.

[mikegarrison]

Just now, ExtremeSquared said:

I'm just sort of worried it's getting heavier every time a failure is addressed. There comes a point in beefing up the structure where mission capabilities need to be adjusted.

Aerospace engineering 101. New designs always get heavier.

[tater]

Looked like GSE again. Static fine, then fountains from GSE racetrack.

[sevenperforce]

1 minute ago, tater said:

Looked like GSE again. Static fine, then fountains from GSE racetrack.

I agree.

Gaseous methane is actually not very flammable, all things considered. Mixed with air, it needs to be between 5% and 15% AND have sufficiently-long exposure to a suitable ignition source. 

It looks like that a GSE methane line -- likely overstressed by repeated static fires -- ruptured following the test, possibly during one of the valve transients. In other words, the valve was too hot and got stuck when the computer gave the command to open or close it, and ruptured, and the rupture propagated. Looking closely at the flow before the explosion, it doesn't look like anything is flowing down out of the skirt; it looks like it is moving laterally from the test stand. It's possible to have a methane leak under the skirt, but difficult given that the LOX tank is on the bottom.

The gout of gaseous methane displaces oxygen inside the skirt, keeping it above 15% and preventing ignition. Meanwhile the cloud grows. Finally, mixing reaches the point that a 5-15% level is exposed for long enough to the superheated metal lines around Raptor, and ignites in a fuel-air detonation. SN4 didn't stand a chance.

[Jacke]

19 minutes ago, mikegarrison said:

Aerospace engineering 101. New designs always get heavier.

Unless the design's working environment and operational life are limited and weight reduction can be forced, like what happened with the Apollo Lunar Module.  Alternately, after a working article is available, refinement can lead to some weight reductions.

[tater]

Putting the GSE in the path of all those engines (once there is more than one) is insane. It needs to be higher up, and/or far, far more robust.

 

[Delay]

Still more reliable than the N1.

[cubinator]

33 minutes ago, Delay said:

Still more reliable than the N1.

I was just thinking earlier that SpaceX may just top the N1 for most powerful non-nuclear explosion if a full stack Starship ever explodes.

[derega16]

If it cause by GSE maybe this is a reson why the didn't build any permanent launch pad yet. Boca one (RIP) is obviously temporaly test stand, Cape one is just a frame for flame diverter which nearly have nothing to change. As there was 3 incidents related to GSE right now, one on hopper and 2 for SN4, means it is a parts that might need even more redesign until operational version. To build any elaborated permanent structure just to find out it have to be rework entirely is not a wise desision.

I guess any work on permanent launch stand will not start until hight altitude hop was done for few times but still before first supper heavy. As they still need a permanent starship pad for static fire anyways means a permanent starship GSP is always needed even when they won't launch anything from it.

Edited May 29, 2020 by derega16

[mikegarrison]

38 minutes ago, cubinator said:

I was just thinking earlier that SpaceX may just top the N1 for most powerful non-nuclear explosion if a full stack Starship ever explodes.

I don't know how this myth got established, but this was far from "the most powerful non-nuclear explosion". There are fuel-air bombs that have exploded with more force than actual nuclear weapons. The current record is believed the be the Russian "Father Of All Bombs" that is estimated to have the equivalent of 44 kilotons of TNT. Big fertilizer or refinery explosions are bigger than the N1 pad explosion.

Edited May 29, 2020 by mikegarrison

[cubinator]

11 minutes ago, mikegarrison said:

I don't know how this myth got established, but this was far from "the most powerful non-nuclear explosion". There are fuel-air bombs that have exploded with more force than actual nuclear weapons. The current record is believed the be the Russian "Father Of All Bombs" that is estimated to have the equivalent of 44 kilotons of TNT. Big fertilizer or refinery explosions are bigger than the N1 pad explosion.

Interesting. Perhaps it was the largest one at the time.

[mikegarrison]

Oops. OK, my bad. I was way off on the fuel-air bombs! Sorry. The "Father Of All Bombs" exploded with the force of 44 tonnes of TNT, not 44 kilotonnes. N1 is now estimated to have been about 1 kilotonne.

However, the big refineries and fertilizer plants have actually exploded with forces in the same range as the N1.

And there have been deliberate weapons tests that exceed the N1 explosion. https://en.wikipedia.org/wiki/Minor_Scale

The "Minor Scale" test exploded with a force of 4 kilotonnes. It was intended to test silo hardening designs to find out if ICBM silos could survive direct hits by nuclear warheads.

It is estimated that the Texas City disaster of 1947 was around 3 kilotonnes.

Edited May 29, 2020 by mikegarrison

[Guest]

Actually, I don't know of any refineries. There was exactly one fertilizer plant explosion that possibly exceeded the that of the N1 (Oppau Plant explosion). The Texas City Disaster was definitely larger, but it involved a bunch of ships with fertilizer and some oil storage near the dock, not a plant or refinery. All the other big explosions involved things generally meant to blow up, though not all of them were deliberate.

[mikegarrison]

2 minutes ago, Dragon01 said:

Actually, I don't know of any refineries. There was exactly one fertilizer plant explosion that possibly exceeded the that of the N1 (Oppau Plant explosion). The Texas City Disaster was definitely larger, but it involved a bunch of ships with fertilizer and some oil storage near the dock, not a plant or refinery. All the other big explosions involved things generally meant to blow up, though not all of them were deliberate.

Yes, thanks. I did realize my error, but I appreciate the correction.

Reading up on it a little more, it seems the initial estimates of the N1 explosion assumed a lot higher percentage of the fuel was actually exploded than is now estimated. So maybe that's how it got so established as being the largest explosion, rather than as being "one of the largest".

[K^2]

"If it was methane, it would be igniting in the flare, correct?" - *FWOOSH*

Timing is everything.

[tater]

 

[CatastrophicFailure]

36 minutes ago, K^2 said:

"If it was methane, it would be igniting in the flare, correct?" - *FWOOSH*

Timing is everything.

Man, they couldn’t‘ve scripted that exchange any better.  

3 minutes ago, tater said:

 

that’ll buff out...