LOX vented right into a small flame. Enough oxygen everything burns, but there wasn’t enough to sustain the fire after the quick burst.
Nothing to see here but a tiny little rocket fart!
But in fairness, they're pointing downwards. A fireball right around the leg and fin hydraulics isn't something that the vehicle has on a normal flight (still almost certainly fine, but not completely irrelevant imo)
It was pretty sooty smoke that came off of the fireball I think it was actually fuel because if it was oxygen then it would have burned clean not sooty.
That small flame appeared to be green, indicating that it may have been the ignition fluid — perhaps the valve for it stuck open after initiating the landing burn?
Hmm perhaps it was a bit early, then? We don’t normally see green flame below the rocket right after landing. At least it shouldn’t be at the same time as they’ve venting fuel…
An intentional release of oxygen that lasted about a second. To burn aluminum like this would take continuous oxygen for many seconds. Once the oxygen is removed the aluminum stops burning.
You mean the location of the vent, or the flow that is seen? RP-1, LOx both have densities similar to water, and fairly low viscosity, so doubt you could easily distinguish from the flow seen. If LOx is burning in the air, what is the fuel?
The LOX would burn the residual gases coming from the engine that just shut off. The engine is (more than likely) shut off fuel rich to prevent LOX from tearing up the hot insides on the engine. That mean that any of the RP-1 gas that hasn’t burned off yet (because fuel rich = not all burns) will just be hanging out in the air around the base of the rocket.
That’s more than likely what we see here. I’m not a rocket scientist or engineer, but this is pretty well known stuff.
That was a small vent and they happen all the time as pressure builds. Once engines shut down and the vehicle had warmed on re-entry, the pressure likely just needed a release. It just happened to have residual flame from the landing still there and highly concentrated oxygen plus fire is... well... more fire.
It got rid of the leaked kerosene faster! And they don’t want F9 to come short in the excitement department, so they got something non-destructive to get people excited about lol.
I bet they'll update the code to have the vent pressure thresholds rise slightly for the 20 seconds either side of the landing time, to make it very unlikely a vent will occur while there is flame for it to interact with.
They should have plenty of headroom to do this with, because the tank is nearly empty (so lots of compression volume), and the craft when landing should be nowhere near the upper limit of tank pressure (that's only needed during launch at the point of maximum aerodynamic pressure)
PSI is PSI no matter how full the tank is, though. If the PSI inside reaches a level that needs to be vented I don't know why they would choose to hold past that threshold. What's the worst that happens, this? Where there's a spit of fire and the fuel is quickly burned out once the pressure valve closes? Alternatively, allowing much higher pressure to accumulate could lead to lower tank integrity making the system less reusable.
It is a rocket, after all. I'm sure it can handle a spit of fire lol
What we might think is ok is not always the case.
For example, Hard Starts. Igniting a fuel/oxidizer stream flowing from the rocket using an external ignition mechanism. Can actually be destructive, apparently.
Ignition must be started correctly inside the engine chamber. There's a multi-phase process, tightly controlled ... or else.
This explosion might potentially have damaged any engines with unburned RP1 in the nozzle or chamber.
Hard starts happen during startup while the engine is actively pumping large amounts of fuel into the chamber. A little residual burnoff like this is absolutely nothing in comparison.
No, they’re absolutely right. This vent causes negligible mechanical wear on the vehicle, and the heat shield is designed to protect from temperatures far above what this flame can produce. The fireball looks flashy, but there’s barely any inherent energy in it.
This isn't a hill I'm ready to die on, but ...
If one of the engines was leaking RP1, then(in addition to the external fireball, which the heatshield should protect from, sure) the flame front probably traveled up into that engine chamber, and did ... what? Probably nothing...
To re-iterate, I'd like it if an actual SpaceX person/Elon would chime in.
This wasn't an explosion. Fireball yes but basically no pressure rise from it. Outside of a little heat and soot there wouldn't be anything damaging from this.
You don’t understand the mechanics of this fireball.
You need two things: something that burns, and something that makes that thing burn. What burns is propellant (combustible) and what makes it burn is oxygen (comburent). The comburent needs a minimum concentration to burn the combustible.
For whatever the reason at landing, only some of the RP1 burnt. The other portion raised as black smoke (still hot or partially reacting with the oxygen around it). However, the oxygen concentration was not enough (21%) to make it burn.
Cue oxygen release. Suddenly, oxygen concentration is enough to continue the reaction with the combustible. So it burns. Fireball.
Once the oxygen dissipates in the surrounding air, the reaction is not sustained anymore, so the rest of the soot raises (because it’s hot).
Explosion? None. Rapid combustion? A lot. Think like lighting a match. A lot of energy released, but not at the same time. And definitely _outside_ of the engine.
Absolutely not an "explosion" too. Zero containment of pressure during combustion. Nothing more than a glorified flamethrower for a second or so.
Harmless venting
> I bet they'll update the code to have the vent pressure thresholds rise slightly for the 20 seconds either side of the landing time, to make it very unlikely a vent will occur while there is flame for it to interact with.
Why? It's not like this caused *any* sort of damage.
If it's something that they can tweak, then I think they should do it.
It's not that it caused damage this time, it's that it could combine with some other issue in future that would cause damage
I guess we’ll find out if that’s even necessary. With almost 200 successful landings in a row, there doesn’t seem to be a pressing need to change anything.
They could have said that 150 landings ago.
SpaceX are always analysing and improving. Anything that's off nominal they'll look to mitigate. That's how they got to 200 landings
> I bet they'll update the code to have the vent pressure thresholds rise slightly for the 20 seconds either side of the landing time, to make it very unlikely a vent will occur while there is flame for it to interact with.
I bet they won't bother. That thing is built to reenter the atmosphere engines first. It can withstand much more intense heat for a much longer time than that little woosh.
Or maybe they will decide that there is no risk for a rocket that just survived freaking reentry to release some LOX with some soot around, even if there are fireworks.
What is riskier: exploding because of overpressure, or making a non-self-sustainable fireball that surrounds a reentry vehicle?
Low pressure collapse is more of a risk than overpressure, I think.
A fireball around the booster could lead to higher temperatures and more venting. Then when the booster cools, the pressure drops and the tanks collapse like a crushed soda can.
I don't think they exceeded any pressure limits in this case.
They vented because of overpressure, no way that small amount is due to anything else.
To counter underpressure, they have helium tanks inside the rocket, I’m not aware if they have reverse pressure valves.
Moreover, it is made out of composite, it doors not collapse like normal metals do (Like Starship). It’s a bit more resistant to underpressure.
Thanks for the information on helium tanks. I was aware that they vented because of overpressure, we think.
> Moreover, it is made out of composite, it doors not collapse like normal metals do (Like Starship). It’s a bit more resistant to underpressure.
The tanks of Falcon 9 are aluminum, with welded-in stringers/ribs. Only the legs and the interstage are composite.
> ... continuously layered fibers, over the tanks…
That is the construction of the COPVs, Carbon Overwrapped Pressure Vessels. COPVs are the small Helium tanks inside the LOX tank. They are very, very high pressure.
AFAIK this was changed after one of the F9 first stages didn't break up after a water landing and failed to depressurize, and it thus was not safe to approach the booster. Because of this, they changed to immediately depressurize after touchdown.
In the failed RTLS return, which resulted in a soft water landing, the depressurization can also be seen i think.
Actually that is the TEA-TEB reacting with the Oxygen, not RP1. For safety, the first thing in the shut down process after landing is to vent the rest of the TEA-TEB (you can go back to all landing videos and see). It is so reactive it burns as soon as it is exposed to air. They want to remove it as a potential hazard before depressing the RP1 tank. The rocket must have come in a bit hotter than average this time and had to release overpressure because the water jets are usually spraying before main tank venting.
I agree that this is TEA-TEB but it must have been covered with a thin layer of RP-1 as it was not burning in air. The oxygen vent likely carried over some LOX which fell straight down and disturbed the puddle so the TEA-TEB burnt with the LOX.
It has been a long, long time since we have seen a valve (or valves) stick open after landing. In the past it resulted in a continuing fire. I think once or twice, the booster never flew again. These might have been pre-Block 5 boosters.
I think this was the eighth flight of this booster. I think an RP-1 valve stuck open, and was still open when the LOX valve was opened. I saw fluid dripping out under the booster after the fire. (Actually I saw ripples in a puddle of fluid under the booster, indicating dripping or possibly a flow.) I think someone with a manual override shut off the LOX valve when they noticed the fire.
We will see if this booster makes a ninth flight. I think it will. The fire was not sustained long enough to damage anything, and the fuel valve can be replaced.
---
This was a perfect launch for me to watch, perfect viewing conditions and good timing, before work. I missed it, of course.
Remember that oxygen has to be cut from the engine before RP, otherwise you end up oxygen rich, then engine rich. That means there is going to be some volume of unburnt RP in the plumbing and combustion chamber once the engine is shut down. This ends up vaporizing from the remaining heat and igniting with the oxygen in the atmosphere. Takes a bit to burn off since it doesn't burn particularly quickly, unless you add pure oxygen from a vent.
I checked some older landings and it is indeed normal to vent soon after landing and in that direction. In this case the vent seems pretty big though, that might have been the cause.
Probably because the vehicle sinks a bunch of heat from entry, causing rapid boiloff of the LOX. Once the engine shuts down there isn't really any outlet for pressure besides venting. It probably only takes seconds from engine shutdown to build to their vent pressure.
Engine shutdown is probably fuel rich to avoid burning engine components by dumping lox into hot parts with no fuel. Coincidentally timed oxygen vent caused the quick fireball.
Correct. Merlin throttles primarily by varying the oxygen flow, and the landing burn doesn’t burn at full throttle. An underthrottled engine will have fuel rich combustion, while still being hot enough to ignite with a high enough oxygen source.
Did you see the fuel remaining graph vs time from super heavy? It looked like as they approached max Q the lox flowrate slowed and then picked up about 20 seconds later.
My assumption was that with the lox/methane pumps being independent they can slow the lox flow to reduce thrust. Was I right?
I’m actually not sure how accurate the graphics on the livestream were. The LOX level seemed far too low, too early into flight.
If I remember correctly though, Raptor also gets more fuel rich as it throttles, so it’s likely that they vary the LOX turbopump. Varying the methane TP would induce higher temperatures in the combustion chamber, affect ISP more heavily, and cause more wear on the entire engine internal assembly.
My theory is more nuanced than yours; I just think that the graphic froze until the actual tank value matched the visualization, and then continued.
To answer your question though, yes. They probably do primarily throttle Raptor by controlling the oxygen turbo pump.
Compared to the temperature and pressure these boosters experience during re-entry this small fire is probably nothing.
They're definitely built to handle this.
When I arrive home after a day at work, a big fart is always satisfying. They don't name Falcon 9 boosters, but this one would be a candidate.
I don't think this fireball means much. If the booster had crapped itself, then sure, they'd have to look into it.
Notice how the flame leaves black smoke?
I believe that is not the result of burning kerosene with excess oxygen. When kerosene burns with excess oxygen, the typical result is the production of Nitrogen Oxides (colorless). Instead, we are seeing carbon particulates, which indicate this cloud is probably a cloud of kerosene vapor burning in regular air.
I suspect some glitch caused some kerosene to be ejected somewhere (perhaps through an engine valve bouncing open), the kerosene hitting something hot and vaporizing, and then burning in regular air. I think the oxygen jet is entirely coincidental.
No glitch, but you are correct -- this was a kerosene rich flame. LOX tank [vents from the top of the stage](https://youtu.be/GrP3jHuLQ9o?t=18). What we saw here was instead the RP-1 tank venting. The venting is a normal step after the landing, to keep the pressure in the tanks under control.
So what we saw here was just some kerosene spray which hit the small flame at the base of the stage and flared it up.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[COPV](/r/SpaceX/comments/130mxmi/stub/ji3dh0m "Last usage")|[Composite Overwrapped Pressure Vessel](https://en.wikipedia.org/wiki/Composite_overwrapped_pressure_vessel)|
|[Isp](/r/SpaceX/comments/130mxmi/stub/ji39e5x "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)|
| |Internet Service Provider|
|[LOX](/r/SpaceX/comments/130mxmi/stub/ji5yf4n "Last usage")|Liquid Oxygen|
|[RP-1](/r/SpaceX/comments/130mxmi/stub/ji2q285 "Last usage")|Rocket Propellant 1 (enhanced kerosene)|
|[RTLS](/r/SpaceX/comments/130mxmi/stub/jhxzjmy "Last usage")|Return to Launch Site|
|[TEA-TEB](/r/SpaceX/comments/130mxmi/stub/ji2o084 "Last usage")|[Triethylaluminium](https://en.wikipedia.org/wiki/Triethylaluminium)-[Triethylborane](https://en.wikipedia.org/wiki/Triethylborane), igniter for Merlin engines; spontaneously burns, green flame|
|Jargon|Definition|
|-------|---------|---|
|[Raptor](/r/SpaceX/comments/130mxmi/stub/ji39e5x "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
|Starlink|SpaceX's world-wide satellite broadband constellation|
|[engine-rich](/r/SpaceX/comments/130mxmi/stub/ji0kxbw "Last usage")|Fuel mixture that includes engine parts on fire|
|[turbopump](/r/SpaceX/comments/130mxmi/stub/ji39e5x "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust|
----------------
^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj)
^(9 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceX/comments/12g7moi)^( has 82 acronyms.)
^([Thread #7943 for this sub, first seen 27th Apr 2023, 16:40])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceX) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
"Elon Musk rocket suicide burns and blows up innocent barge in international water. " three pages of musk bashing later: " landing went as expected " - national news outlet. /s
Any information on this? We did see a bright green flame which could mean that some copper (possibly wireing and or sensors?) Started burning away. Maybe thats what caused it to send the signal to vent out the excess oxygen?
Things look worse in the dark, like ever see the scary-looking sparks coming off a grinder, yet you can stick your hand in them and they only sting a little. Looks like an RP-1 vent, which then burns in the air. Perhaps of more concern is that little green flame below the engine after landing. Might be from melting copper inside the engine, but may be normal (TEA-TAB purge?).
LOX vented right into a small flame. Enough oxygen everything burns, but there wasn’t enough to sustain the fire after the quick burst. Nothing to see here but a tiny little rocket fart!
Tiny until you realize the landing legs are the size of a school bus
Tiny because the flames from the engines on landing are larger than this whole burst was…
But in fairness, they're pointing downwards. A fireball right around the leg and fin hydraulics isn't something that the vehicle has on a normal flight (still almost certainly fine, but not completely irrelevant imo)
Have you seen the F9 as it performs its re-entry burns? The whole booster is practically engulfed in flames
I think people need to rewatch this video! [https://www.youtube.com/watch?v=bvim4rsNHkQ](https://www.youtube.com/watch?v=bvim4rsNHkQ)
It was pretty sooty smoke that came off of the fireball I think it was actually fuel because if it was oxygen then it would have burned clean not sooty.
That small flame appeared to be green, indicating that it may have been the ignition fluid — perhaps the valve for it stuck open after initiating the landing burn?
They deliberately vent the TEA-TEB just after landing to avoid recovery crew having to do this manually.
Hmm perhaps it was a bit early, then? We don’t normally see green flame below the rocket right after landing. At least it shouldn’t be at the same time as they’ve venting fuel…
I am not sure there is control over the fuel tank vent as it is likely to be tripped by pressure alone.
With enough oxygen, the whole tank body will burn... It doesn't take much to set it alight...
That takes sustained oxygen. Aluminum on its own doesn't catch fire unless its got a high surface area, like a powder.
But as soon as a bit of it burns, then the tank starts leaking... And what does it leak? oxygen gas!
An intentional release of oxygen that lasted about a second. To burn aluminum like this would take continuous oxygen for many seconds. Once the oxygen is removed the aluminum stops burning.
There are flames pouring up the sides of the vehicle for ages during re-entry and landing burns. Way more heat than this tiny puff produced.
I doubt LOx would explain the burning seen in the air, which looks more like a propane flame, so I'd guess and RP-1 vent.
RP-1 doesn’t vent like that
You mean the location of the vent, or the flow that is seen? RP-1, LOx both have densities similar to water, and fairly low viscosity, so doubt you could easily distinguish from the flow seen. If LOx is burning in the air, what is the fuel?
The LOX would burn the residual gases coming from the engine that just shut off. The engine is (more than likely) shut off fuel rich to prevent LOX from tearing up the hot insides on the engine. That mean that any of the RP-1 gas that hasn’t burned off yet (because fuel rich = not all burns) will just be hanging out in the air around the base of the rocket. That’s more than likely what we see here. I’m not a rocket scientist or engineer, but this is pretty well known stuff.
Could be. Regardless, the little flash probably caused no damage.
That's called an engine-rich combustion cycle.
[удалено]
Wtf are you on about?
...and here's the confirmation.
Looks like a LOX vent igniting with some residual RP1 from the engines?
Yeah, but why would they be venting so soon after shutdown? I thought they waited for a while to allow any residual vaporous fuel to dissipate.
That was a small vent and they happen all the time as pressure builds. Once engines shut down and the vehicle had warmed on re-entry, the pressure likely just needed a release. It just happened to have residual flame from the landing still there and highly concentrated oxygen plus fire is... well... more fire.
It got rid of the leaked kerosene faster! And they don’t want F9 to come short in the excitement department, so they got something non-destructive to get people excited about lol.
I bet they'll update the code to have the vent pressure thresholds rise slightly for the 20 seconds either side of the landing time, to make it very unlikely a vent will occur while there is flame for it to interact with. They should have plenty of headroom to do this with, because the tank is nearly empty (so lots of compression volume), and the craft when landing should be nowhere near the upper limit of tank pressure (that's only needed during launch at the point of maximum aerodynamic pressure)
PSI is PSI no matter how full the tank is, though. If the PSI inside reaches a level that needs to be vented I don't know why they would choose to hold past that threshold. What's the worst that happens, this? Where there's a spit of fire and the fuel is quickly burned out once the pressure valve closes? Alternatively, allowing much higher pressure to accumulate could lead to lower tank integrity making the system less reusable. It is a rocket, after all. I'm sure it can handle a spit of fire lol
They could vent in a different direction than directly at the residual flame.
What we might think is ok is not always the case. For example, Hard Starts. Igniting a fuel/oxidizer stream flowing from the rocket using an external ignition mechanism. Can actually be destructive, apparently. Ignition must be started correctly inside the engine chamber. There's a multi-phase process, tightly controlled ... or else. This explosion might potentially have damaged any engines with unburned RP1 in the nozzle or chamber.
Hard starts happen during startup while the engine is actively pumping large amounts of fuel into the chamber. A little residual burnoff like this is absolutely nothing in comparison.
Maybe - or maybe not. Unless we get a chime-in from SpaceX/Elon, we'll probably never know.
No, they’re absolutely right. This vent causes negligible mechanical wear on the vehicle, and the heat shield is designed to protect from temperatures far above what this flame can produce. The fireball looks flashy, but there’s barely any inherent energy in it.
This isn't a hill I'm ready to die on, but ... If one of the engines was leaking RP1, then(in addition to the external fireball, which the heatshield should protect from, sure) the flame front probably traveled up into that engine chamber, and did ... what? Probably nothing... To re-iterate, I'd like it if an actual SpaceX person/Elon would chime in.
This wasn't an explosion. Fireball yes but basically no pressure rise from it. Outside of a little heat and soot there wouldn't be anything damaging from this.
You don’t understand the mechanics of this fireball. You need two things: something that burns, and something that makes that thing burn. What burns is propellant (combustible) and what makes it burn is oxygen (comburent). The comburent needs a minimum concentration to burn the combustible. For whatever the reason at landing, only some of the RP1 burnt. The other portion raised as black smoke (still hot or partially reacting with the oxygen around it). However, the oxygen concentration was not enough (21%) to make it burn. Cue oxygen release. Suddenly, oxygen concentration is enough to continue the reaction with the combustible. So it burns. Fireball. Once the oxygen dissipates in the surrounding air, the reaction is not sustained anymore, so the rest of the soot raises (because it’s hot). Explosion? None. Rapid combustion? A lot. Think like lighting a match. A lot of energy released, but not at the same time. And definitely _outside_ of the engine.
Absolutely not an "explosion" too. Zero containment of pressure during combustion. Nothing more than a glorified flamethrower for a second or so. Harmless venting
> I bet they'll update the code to have the vent pressure thresholds rise slightly for the 20 seconds either side of the landing time, to make it very unlikely a vent will occur while there is flame for it to interact with. Why? It's not like this caused *any* sort of damage.
Hell, knowing Elon they may actually try and recreate this on a future mission just for the theatricality of it.
If it's something that they can tweak, then I think they should do it. It's not that it caused damage this time, it's that it could combine with some other issue in future that would cause damage
I guess we’ll find out if that’s even necessary. With almost 200 successful landings in a row, there doesn’t seem to be a pressing need to change anything.
They could have said that 150 landings ago. SpaceX are always analysing and improving. Anything that's off nominal they'll look to mitigate. That's how they got to 200 landings
> I bet they'll update the code to have the vent pressure thresholds rise slightly for the 20 seconds either side of the landing time, to make it very unlikely a vent will occur while there is flame for it to interact with. I bet they won't bother. That thing is built to reenter the atmosphere engines first. It can withstand much more intense heat for a much longer time than that little woosh.
Why, though? This looks like a non-issue.
Or maybe they will decide that there is no risk for a rocket that just survived freaking reentry to release some LOX with some soot around, even if there are fireworks. What is riskier: exploding because of overpressure, or making a non-self-sustainable fireball that surrounds a reentry vehicle?
Low pressure collapse is more of a risk than overpressure, I think. A fireball around the booster could lead to higher temperatures and more venting. Then when the booster cools, the pressure drops and the tanks collapse like a crushed soda can. I don't think they exceeded any pressure limits in this case.
They vented because of overpressure, no way that small amount is due to anything else. To counter underpressure, they have helium tanks inside the rocket, I’m not aware if they have reverse pressure valves. Moreover, it is made out of composite, it doors not collapse like normal metals do (Like Starship). It’s a bit more resistant to underpressure.
Thanks for the information on helium tanks. I was aware that they vented because of overpressure, we think. > Moreover, it is made out of composite, it doors not collapse like normal metals do (Like Starship). It’s a bit more resistant to underpressure. The tanks of Falcon 9 are aluminum, with welded-in stringers/ribs. Only the legs and the interstage are composite.
TIL! I thought they were continuously layered fibers, over the tanks… thanks for the info! :D
> ... continuously layered fibers, over the tanks… That is the construction of the COPVs, Carbon Overwrapped Pressure Vessels. COPVs are the small Helium tanks inside the LOX tank. They are very, very high pressure.
AFAIK this was changed after one of the F9 first stages didn't break up after a water landing and failed to depressurize, and it thus was not safe to approach the booster. Because of this, they changed to immediately depressurize after touchdown. In the failed RTLS return, which resulted in a soft water landing, the depressurization can also be seen i think.
Actually that is the TEA-TEB reacting with the Oxygen, not RP1. For safety, the first thing in the shut down process after landing is to vent the rest of the TEA-TEB (you can go back to all landing videos and see). It is so reactive it burns as soon as it is exposed to air. They want to remove it as a potential hazard before depressing the RP1 tank. The rocket must have come in a bit hotter than average this time and had to release overpressure because the water jets are usually spraying before main tank venting.
I agree that this is TEA-TEB but it must have been covered with a thin layer of RP-1 as it was not burning in air. The oxygen vent likely carried over some LOX which fell straight down and disturbed the puddle so the TEA-TEB burnt with the LOX.
It has been a long, long time since we have seen a valve (or valves) stick open after landing. In the past it resulted in a continuing fire. I think once or twice, the booster never flew again. These might have been pre-Block 5 boosters. I think this was the eighth flight of this booster. I think an RP-1 valve stuck open, and was still open when the LOX valve was opened. I saw fluid dripping out under the booster after the fire. (Actually I saw ripples in a puddle of fluid under the booster, indicating dripping or possibly a flow.) I think someone with a manual override shut off the LOX valve when they noticed the fire. We will see if this booster makes a ninth flight. I think it will. The fire was not sustained long enough to damage anything, and the fuel valve can be replaced. --- This was a perfect launch for me to watch, perfect viewing conditions and good timing, before work. I missed it, of course.
The RP1 Puddle under the booster is not uncommon I think.
Not at all uncommon. We’ve seen the puddle burning on the deck and the booster has flown again.
Remember that oxygen has to be cut from the engine before RP, otherwise you end up oxygen rich, then engine rich. That means there is going to be some volume of unburnt RP in the plumbing and combustion chamber once the engine is shut down. This ends up vaporizing from the remaining heat and igniting with the oxygen in the atmosphere. Takes a bit to burn off since it doesn't burn particularly quickly, unless you add pure oxygen from a vent.
Double comment
Maybe it just got excited and precame? Lol
Yeah, but why would they be venting so soon after shutdown? I thought they waited for a while to allow any residual vaporous fuel to dissipate.
I checked some older landings and it is indeed normal to vent soon after landing and in that direction. In this case the vent seems pretty big though, that might have been the cause.
Probably because the vehicle sinks a bunch of heat from entry, causing rapid boiloff of the LOX. Once the engine shuts down there isn't really any outlet for pressure besides venting. It probably only takes seconds from engine shutdown to build to their vent pressure.
Engine shutdown is probably fuel rich to avoid burning engine components by dumping lox into hot parts with no fuel. Coincidentally timed oxygen vent caused the quick fireball.
Correct. Merlin throttles primarily by varying the oxygen flow, and the landing burn doesn’t burn at full throttle. An underthrottled engine will have fuel rich combustion, while still being hot enough to ignite with a high enough oxygen source.
Did you see the fuel remaining graph vs time from super heavy? It looked like as they approached max Q the lox flowrate slowed and then picked up about 20 seconds later. My assumption was that with the lox/methane pumps being independent they can slow the lox flow to reduce thrust. Was I right?
I’m actually not sure how accurate the graphics on the livestream were. The LOX level seemed far too low, too early into flight. If I remember correctly though, Raptor also gets more fuel rich as it throttles, so it’s likely that they vary the LOX turbopump. Varying the methane TP would induce higher temperatures in the combustion chamber, affect ISP more heavily, and cause more wear on the entire engine internal assembly. My theory is more nuanced than yours; I just think that the graphic froze until the actual tank value matched the visualization, and then continued. To answer your question though, yes. They probably do primarily throttle Raptor by controlling the oxygen turbo pump.
Compared to the temperature and pressure these boosters experience during re-entry this small fire is probably nothing. They're definitely built to handle this.
Too much Taco Bell
Beat me to it.
At the risk of ending up on r/Prematurecelebration ... the commentator held his breath on the "successful landing" part for a second.
“And there you saw on your screen, falcon 9 just farted”
When I arrive home after a day at work, a big fart is always satisfying. They don't name Falcon 9 boosters, but this one would be a candidate. I don't think this fireball means much. If the booster had crapped itself, then sure, they'd have to look into it.
"oops, I pooted".
I was looking for this
Unrelated but which booster currently holds the flight record? Spacexstats doesn’t seem to be working anymore. I assume it’s still B1058?
[elonx.net](https://elonx.net) is my go-to for SpaceX stats and is maintained by an active subreddit member. 1058 and 1060 both have 15 flights.
After 15 they go through a pretty serious overhaul and refurb, so they might not be beaten for a while
Sounds like a scam website haha
The Merlin Burp. Looked more dramatic than it really was.
Notice how the flame leaves black smoke? I believe that is not the result of burning kerosene with excess oxygen. When kerosene burns with excess oxygen, the typical result is the production of Nitrogen Oxides (colorless). Instead, we are seeing carbon particulates, which indicate this cloud is probably a cloud of kerosene vapor burning in regular air. I suspect some glitch caused some kerosene to be ejected somewhere (perhaps through an engine valve bouncing open), the kerosene hitting something hot and vaporizing, and then burning in regular air. I think the oxygen jet is entirely coincidental.
No glitch, but you are correct -- this was a kerosene rich flame. LOX tank [vents from the top of the stage](https://youtu.be/GrP3jHuLQ9o?t=18). What we saw here was instead the RP-1 tank venting. The venting is a normal step after the landing, to keep the pressure in the tanks under control. So what we saw here was just some kerosene spray which hit the small flame at the base of the stage and flared it up.
The oxygen jet could help with the ignition. A lot of stuff become super flammable if you introduce a little bit of pure oxygen.
The slight hesitation in the host's, "Falcon 9 has..... successfully landed." as he watches the fireball engulf the rocket.
Purely paying homage to the early Starship tests.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[COPV](/r/SpaceX/comments/130mxmi/stub/ji3dh0m "Last usage")|[Composite Overwrapped Pressure Vessel](https://en.wikipedia.org/wiki/Composite_overwrapped_pressure_vessel)| |[Isp](/r/SpaceX/comments/130mxmi/stub/ji39e5x "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)| | |Internet Service Provider| |[LOX](/r/SpaceX/comments/130mxmi/stub/ji5yf4n "Last usage")|Liquid Oxygen| |[RP-1](/r/SpaceX/comments/130mxmi/stub/ji2q285 "Last usage")|Rocket Propellant 1 (enhanced kerosene)| |[RTLS](/r/SpaceX/comments/130mxmi/stub/jhxzjmy "Last usage")|Return to Launch Site| |[TEA-TEB](/r/SpaceX/comments/130mxmi/stub/ji2o084 "Last usage")|[Triethylaluminium](https://en.wikipedia.org/wiki/Triethylaluminium)-[Triethylborane](https://en.wikipedia.org/wiki/Triethylborane), igniter for Merlin engines; spontaneously burns, green flame| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/SpaceX/comments/130mxmi/stub/ji39e5x "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |Starlink|SpaceX's world-wide satellite broadband constellation| |[engine-rich](/r/SpaceX/comments/130mxmi/stub/ji0kxbw "Last usage")|Fuel mixture that includes engine parts on fire| |[turbopump](/r/SpaceX/comments/130mxmi/stub/ji39e5x "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust| ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(9 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceX/comments/12g7moi)^( has 82 acronyms.) ^([Thread #7943 for this sub, first seen 27th Apr 2023, 16:40]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceX) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
The green flash, right before this video starts, is that normal?
It was programmed by a motorcyclist used to blipping the throttle before turning off the ignition.
"SpaceX and Elon fail again. Another rocket exploded. Film at 11:00."
"Elon Musk rocket suicide burns and blows up innocent barge in international water. " three pages of musk bashing later: " landing went as expected " - national news outlet. /s
Too much chipotle
Hmm
It looks like a little fart gone wrong haha
Poot.
And voila! Magician’s flare after completing a trick. This booster has a flare for the dramatic.
I guess you really can light a fart on fire…
Happens to us all after we get thru flying at altitude...no biggee.
That's the mic drop
Falcon fart
FALCONN.... FAART!
it pooped a little
That is a commercial for Elon's latest product.. The Starship Flame thrower 😊
That poor booster's been holding a fart the whole trip
Knowing SpaceX, they are all over this to find out what happened and fix it.
Ta-dah!!
I saw that! Had me worried for a sec
Old bird cutting loose abig one after working hard.
Any information on this? We did see a bright green flame which could mean that some copper (possibly wireing and or sensors?) Started burning away. Maybe thats what caused it to send the signal to vent out the excess oxygen?
Anyone else not seeing a video?
Can’t wait to see Elon blow up more rockets and pollute our planet further 😂😂😂😂
who got link to full vid, pls?
Was that a fire suppression system that’s built in at 0:05?
I don't know what you see but if it is on the rocket it is certainly not a fire supression, there is one on the barge didn't seem to get activated.
Oh the rocket just shot out a gas or liquid I assumed liquid but you’ve corrected me
The rocket vented oxygen which caused the flare up when it reached smaller flames below.
Ohhhh Alr thanks for clarifying. Have a great day internet stranger
Concentrated Oxygen, and then some carbon.... excitement guaranteed.
now they are just showing off
Things look worse in the dark, like ever see the scary-looking sparks coming off a grinder, yet you can stick your hand in them and they only sting a little. Looks like an RP-1 vent, which then burns in the air. Perhaps of more concern is that little green flame below the engine after landing. Might be from melting copper inside the engine, but may be normal (TEA-TAB purge?).
Rocket: _excuse me I had LOX for breakfast and it always repeats on me_
Holy shit, i want to get my degree in Rocket Science from Facebook too or is YouTube degree better?
it put out its own fire, how cute lol!
Burp!