totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

3 minutes ago, sevenperforce said:

Rewatching for the fourth time at 25% speed.

Raptor SN42 is never ignited; just the other two. They provide the entire kick-flip torque.

At T+6:32, a few green flashes appear on the left-hand Raptor relative to SN42.

By T+6:37, the exhaust from the left-hand Raptor is bright green:

It appears to correct a moment later and becomes the familiar pink-purple again:

One second later the green has returned and it's almost violent in its hue:

The green disappears, and the other engine, on the right, is shut down, apparently because they were planning on a 2-1 landing burn:

The green comes back, this time to stay, and becomes so bright that it fills up the entire skirt section. The length of the plume is noticeably shortened as copper residue fills the exhaust, which in turn is saturated with soot:

So it looks like they planned a 2-1 landing burn, but the engine they chose to land with had an anomaly on restart that led to it eating itself from the inside out over a period of about 4 seconds.

 

Thanks!

 

- but am I correct: the one that did not relight is the last one firing before the kickover at the top of the flight?

Edited December 9, 2020 by JoeSchmuckatelli

[sevenperforce]

1 minute ago, JoeSchmuckatelli said:

Thanks!

- but am I correct: the one that did not relight is the last one firing before the kickover at the top of the flight?

Yes, correct.

I was curious about what their flight profile would be, and how they would get a "failure over water" if something went wrong.

What they did was actually quite inventive. They flew out over the water, pitching over upside down like the Shuttle. They maintained heading on two engines. Then, they reduced to a single engine which allowed them to fly at a high AoA, basically hovering sideways. They used this engine for a tiny kick at shutdown to help tip back over in the opposite direction and then used the skydive to fly back.

Roll and pitch control with those flaps was awe-inspiring.

If you play at reduced speed you see that they never did extend the legs. Clearly the leg-extension was supposed to happen a few moments later.

[RyanRising]

Holy cow. I don't have any clever insight on this, but I just want to put in my two cents that that was one of the most incredible things I've ever seen, even though it was over the internet. I thought for sure the flip would have messed up if the descent didn't, but it made it to the ground upright. And there was an earth-shattering kaboom. Wow.

[tater]

Was talking to a friend who stopped by (we watched together).

That was epic.

Wow.

And SN9 is good to go. We get to see this again.

So cool.

[Flying dutchman]

Sn8

 

Edited December 9, 2020 by Flying dutchman

[computercat04]

That landing was so epic yet so sad!! F in chat for SN8.

[sh1pman]

17 minutes ago, sevenperforce said:

If you play at reduced speed you see that they never did extend the legs. Clearly the leg-extension was supposed to happen a few moments later.

It probably never reached the speed at which they were supposed to extend. 

[Serpens Solidus]

Yeah just blame the header tank

[pmborg]

The Flight was perfect allow collecting performance data for 3 engines, 2 engines and fly only with one engine.

But this was the fatal Moment (the Second Engine Cut-off), after this the Ship was doomed: (not enouf power to reduce the Vertical speed in time)

 

[RCgothic]

I'm out of likes right now. I think it was supposed to be a 2-1 landing burn, but the 1 was having an engine-rich anomaly (not its fault, due to low tank pressure). The engine would not abort in this situation, it has to try and save the stage at the cost of its own internals.

One of the ground tents is on fire.

Landing site on fire.

 

Edited December 10, 2020 by RCgothic

[Meecrob]

So what are the bets that they knew they would have this header tank issue and SN13 is the new design?

 

[JoeSchmuckatelli]

10 minutes ago, Meecrob said:

So what are the bets that they knew they would have this header tank issue and SN13 is the new design?

 

If true and they still flew - good on them! 

[T-20000]

Although the test ended in a massive fire ball, it's still very spectacular!

[Serpens Solidus]

The nose is still fine, they could have put people on it!

[mikegarrison]

1 hour ago, sevenperforce said:

Methalox produces just water and CO2, nothing else. The only thing cleaner is hydrolox, which produces only water.

In theory any hydrocarbon burned with oxygen produces only water and CO2, but in practice this is not the case. The more complicated the hydrocarbon chains, the more likely they are to not break and just leave particles of carbon or hydrocarbon that incompletely combust.

Methane is the simplest hydrocarbon, and depending on the purity (ie. no ethane, propane etc.  mixed in) has no carbon-carbon bonds. So it tends to leave very few uncombusted particles.

Edited December 10, 2020 by mikegarrison

[sh1pman]

6 minutes ago, mikegarrison said:

Methane is the simplest hydrocarbon, and depending on the purity (ie. no propane mixed in, etc.) has no carbon-carbon bonds. So it tends the leave very little uncombusted particles.

True if it’s burnt at or near stoichiometric ratio or with excess of oxygen. But if there’s a great excess of fuel (as in a fuel preburner), that’s a different story. 

[JoeSchmuckatelli]

1 hour ago, Serpens Solidus said:

Yeah just blame the header tank

you gotta love his optimism... but I clearly saw stuff that probably was not suppose to be on fire, on fire during the ascent.

 

But the fact it turned back on again is amazing

[sevenperforce]

9 minutes ago, JoeSchmuckatelli said:

you gotta love his optimism... but I clearly saw stuff that probably was not suppose to be on fire, on fire during the ascent.

 

But the fact it turned back on again is amazing

That was just a glut of unburned propellant igniting in air. The skirt can handle the heat.

[sh1pman]

So where did the green come from, what do you think? Was it copper from fuel channels inside engine bells? 

 

[Brotoro]

I was rewatching the video. Stuff that looked bad when I watched it live look cool now. When the engines get turned off, there's lots of activity, but the engine appears to smartly lock itself out at full gimbal to get out of the way of the other engines. Much better than the "uh, oh! Engine failure!" That I was thinking at the time.

[kylelander]

I fell asleep watching the livestream, but watching he replay...

I was stunned! Everything was nominal, just not the landing.

 

[Geonovast]

Overlapping threads have been merged.

[JoeSchmuckatelli]

43 minutes ago, sevenperforce said:

That was just a glut of unburned propellant igniting in air. The skirt can handle the heat.

I can accept that - but the foil wrapped stuff and some kind of tubing went up too.  At the 1:40 mark - the stuff on the right catches fire.  Not educated enough to know what it was - but clearly the ship continued to operate without.

 

On another note: why would they not deploy the legs earlier?  Even if they had collapsed given the rate of descent there at the end... might they not have acted like a bumper and increased the chance of less than complete destruction?

[sevenperforce]

1 hour ago, sh1pman said:

So where did the green come from, what do you think? Was it copper from fuel channels inside engine bells? 

Yep. Oxygen-rich combustion became engine-rich combustion. 

[tater]

Holy %$#@ I saw this at first and thought it was a render...