SpaceX F9 : Starlink 6 (v1.0 L5) : Mar. 18, 2020 - Discussion

[anof]

wow, surprised they got to them tbh, I would have guessed that the first stage issues lead to them being perhaps 10km off target

Aren't fairings jettisoned before the engine shutdown occurred?

Fairings are normally jettisoned about 30 seconds after second stage ignition.

Sorry just noticed this is the update thread.

[abaddon]

Since this was the 5th reuse...would these engines if original have the updated turbopump that NASA wanted for the "cracking" issue seen on the blades?

If I am remembering correctly, the booster pre-dates that change.  As there was no evidence it was actually causing a problem, I would be surprised if SpaceX went back and replaced/modified these engines.

[abaddon]

[From the Updates thread]

wow, surprised they got to them tbh, I would have guessed that the first stage issues lead to them being perhaps 10km off target

Aren't fairings jettisoned before the engine shutdown occurred?

[And answered; no  ]

Looking at the plot on the updates thread, it looks like the shortfall came close to MECO and it sounds like S2 was likely able to make up the difference enough before fairing jettison to not impact the recovery, or the shortfall was not enough to impact fairing recovery, crossrange of fairing recovery system was able to correct for it, etc.  Just guessing here.

[eriblo]

I'm actually somewhat (irrationally?) pleased to see this. F9 has always been advertised as having engine-out capability; and we just saw that today with a successful Starlink deployment. The booster was lost, but not before putting its fifth payload where it needed to go. Congrats to B1048 for scoring SpaceX's first "ace."

And even though failure happened shortly before MECO it implies the engines were in a steady state after the failure, as they managed to restart and complete an entry burn.  So the blast containment shields appear to have done their job and there was no collateral damage to other engines.

It will be interesting to learn if the landing failure was due to the failed engine being one of "the three" or if it was just trajectory-related, due to the extended compensation burn.  If it's a trajectory problem, it's possible that software or other tweaks (reserving more fuel, stationing a third ASDS further down range) *could* save such a situation in the future... although the cure might cost too much to be worth it.  Better to crank up the engine reliability further instead.

You're assuming there was a blast to contain. The engine could have just reached some shutdown criteria like high/low temp or power and shutdown before there was further damage.

It even could have been another sensor issue.

There was debris observable at t+2:21 as well as a brightening of the plume, combined with some frame dropouts on the camera

It looks like it could be something, but then it vanishes the next frame.  If the engine blew, I'd expect a lot more than a single large fragment.  And while it's not implausible that it's an object that was blown away by the exhaust, I'm wondering if that might be soot from a fuel-rich condition caused by/causing the engine shutdown.

There are a lot of compression artifacts in the stream and there are many single frames where there is some "feature" in that particular location, both before and after the shut down. I would also think that a solid object falling through the plume would light up much more brightly...

[ulm_atms]

Since this was the 5th reuse...would these engines if original have the updated turbopump that NASA wanted for the "cracking" issue seen on the blades?

If I am remembering correctly, the booster pre-dates that change.  As there was no evidence it was actually causing a problem, I would be surprised if SpaceX went back and replaced/modified these engines.

That's what I was thinking about the timeline...I was thinking this was pre change but wasn't 100% sure...thanks!

Cracks don't always cause problems...until they do.  If this was an original engine before the crack mitigation..we might be seeing the limit of use of this version.  Cracks usually grow slowly...until they give out completely all of a sudden...especially in a turbopump environment.  Remember...this is new territory for rocket engines....being used again and again...bound to find some surprise eventually.

Anyone know how many full duration fires a single M1D have been tested to at McGregor to date?

[niwax]

wow, surprised they got to them tbh, I would have guessed that the first stage issues lead to them being perhaps 10km off target

I would expect the fairings to have significant crossrange. They glide down over a few minutes.

[Prettz]

Since this was the 5th reuse...would these engines if original have the updated turbopump that NASA wanted for the "cracking" issue seen on the blades?

If I am remembering correctly, the booster pre-dates that change.  As there was no evidence it was actually causing a problem, I would be surprised if SpaceX went back and replaced/modified these engines.

That's what I was thinking about the timeline...I was thinking this was pre change but wasn't 100% sure...thanks!

Cracks don't always cause problems...until they do.  If this was an original engine before the crack mitigation..we might be seeing the limit of use of this version.  Cracks usually grow slowly...until they give out completely all of a sudden...especially in a turbopump environment.  Remember...this is new territory for rocket engines....being used again and again...bound to find some surprise eventually.

Anyone know how many full duration fires a single M1D have been tested to at McGregor to date?

One of the first recovered boosters they did, I think, 8 (?) full duration firings on it back at McGregor. But that won't be as many engine starts/stops as the center engine of this mission's booster.

[FutureSpaceTourist]

https://twitter.com/djsnm/status/1240304106578698240

I see a lot of people think that the engine that shut down exploded in some dramatic fashion in part because they see a flash and a puff of smoke. However, if the engine shuts down then it's exhaust slows down and interacts with the other engine plumes, making them bright.

[FinalFrontier]

Good day in the end. Falcon 9 worked as designed and the engine compartment system prevented the engine from destroying the rocket or damaging the other engines when it went.

Hopefully the failure mode for that engine was relatively simple otherwise there might be some effect to the DM2 schedule. I suppose NASA will be interested to know what went on as well.

Debris your seeing on footage is probably pieces of the engine and engine bay heat shield for that engine that broke away.

This is the first time (we know of) that the current merlin 1D advanced variant has failed in flight, but it would be hard to say whether one of these has failed on a test stand or not. Presumably yes.

Given how many of these have flown and how much firing time has been amassed this was probably due to either wear and tear or a manufacturing defect specific to that engine.

[racevedo88]

Does anyone know if we fully lost the booster or if it possibly splashed down (softly) further downrange.  if it did its recovery will be great help to the investigation

[illectro]

I'm not confident enough to post this on twitter yet, but I think there might have been a second engine failure during the entry burn, and that killed the chance of landing.
 
At entry burn there's a change in the exhaust pattern accompanied by what looks like a bump, then the  camera got fogged up with visible drops of liquid, which I think is unburned fuel expelled during an engine failure.

F9 uses 3 engines for entry burn, if one of the engines that shut down on ascent was one of these 3 I don't think we'd see an entry burn attempt, and then if one of the engines used for landing failed during the entry burn then it might not even make it to the surface.

[envy887]

Good day in the end. Falcon 9 worked as designed and the engine compartment system prevented the engine from destroying the rocket or damaging the other engines when it went.

Debris your seeing on footage is probably pieces of the engine and engine bay heat shield for that engine that broke away.

We don't know if the shutdown was energetic enough to liberate any engine parts.

And it's highly unlikely that the debris floating past during coast was related to the engine. Ice shedding during coast is normal.

[whitelancer64]

Does anyone know if we fully lost the booster or if it possibly splashed down (softly) further downrange.  if it did its recovery will be great help to the investigation

There was no call-out for landing burn start on the webcast. If the booster did not fire for the landing burn, then it impacted the ocean at high speed and is in very small pieces.

[daedalus1]

Hopefully the failure mode for that engine was relatively simple otherwise there might be some effect to the DM2 schedule. I suppose NASA will be interested to know what went on as well.


Given how many of these have flown and how much firing time has been amassed this was probably due to either wear and tear or a manufacturing defect specific to that engine.

Considering that the Atlas engines that launch the Starliner end up in the Atlantic after one use, why would this delay Dragon 2 launch? This is the 5th launch of these engines and Dragon will not be on a 5th used booster. Talk about one rule for one...!

[gongora]

Hopefully the failure mode for that engine was relatively simple otherwise there might be some effect to the DM2 schedule. I suppose NASA will be interested to know what went on as well.


Given how many of these have flown and how much firing time has been amassed this was probably due to either wear and tear or a manufacturing defect specific to that engine.

Considering that the Atlas engines that launch the Starliner end up in the Atlantic after one use, why would this delay Dragon 2 launch? This is the 5th launch of these engines and Dragon will not be on a 5th used booster. Talk about one rule for one...!

An engine failed on ascent.  That has to be looked at.

[eriblo]

I'm not confident enough to post this on twitter yet, but I think there might have been a second engine failure during the entry burn, and that killed the chance of landing.
 
At entry burn there's a change in the exhaust pattern accompanied by what looks like a bump, then the  camera got fogged up with visible drops of liquid, which I think is unburned fuel expelled during an engine failure.

F9 uses 3 engines for entry burn, if one of the engines that shut down on ascent was one of these 3 I don't think we'd see an entry burn attempt, and then if one of the engines used for landing failed during the entry burn then it might not even make it to the surface.

The change in pattern comes after a short period of dropped frames so does not have to be as abrupt as it appears and we can not compare to the previous Starlink launch as it lost the signal at about this point. The reentry burn plume is always rather turbulent. The fouling of the lens happens to varying degree on all landings and I personally do not think it indicates anything special. The exhaust contains plenty of soot and water and they actually had to redesign the camera housing to improve visibility.

[Nomadd]

 Everybody keeps saying "engine failure". Isn't it possible that the engine was intentionally shut down because of a slightly off nominal condition, since other engines could just throttle up to make up  the difference? Meaning they might even have used it for the entry burn since there was nothing to lose?

[whitelancer64]

Everybody keeps saying "engine failure". Isn't it possible that the engine was intentionally shut down because of a slightly off nominal condition, since other engines could just throttle up to make up  the difference? Meaning they might even have used it for the entry burn since there was nothing to lose?

Whatever triggered the shut down can reasonably be called a failure of the engine.

[aviators99]

I know SpaceX is a private company, but I'm disappointed at the lack of information during the live broadcast.  Not because I think they "owe" it to us or anything, but it's just that I'm interested in what's happening while it's happening.  The people who talk on the stream are obviously knowledgable and highly skilled.  But they are acting as PR people; not scientists.

I know that the people actually handling the situations are too busy to be dealing with viewers.  But if you are going to have dedicated people to announce the status, and they are skilled enough to understand what's going on, I wish they would actually report the status.  The launchpad abort, although an unfortunate mistake, leads me to believe they are reading from a script and not looking at actual telemetry.

Sorry to vent about this.  Again, I don't feel like they owe it to us and they're a private company.  I just wish it was different.

[Nomadd]

Everybody keeps saying "engine failure". Isn't it possible that the engine was intentionally shut down because of a slightly off nominal condition, since other engines could just throttle up to make up  the difference? Meaning they might even have used it for the entry burn since there was nothing to lose?

Whatever triggered the shut down can reasonably be called a failure of the engine.

There are other sites you might go to if you want six pages of semantical nonsense.