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

[meekGee]

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.

The debris observed before the re-entry burn may be significant.

Right, forgot about that.

Still though, one of the three could have shut down rightfully but peacefully during ascent, and the restart criteria during descent are much looser and so it tried, but failed (hence debris)

The other two engines weren't affected either, burned longer, but by that time trajectory/propellant margins were off and so the stage is lost.

[JamesH65]

This new Starlink profile doesn’t seem to be working very well so far.

From the satellites POV, it's a winner...

[XenIneX]

A reminder:  every time something goes off-nominal, cries of "debris!" start flying thick and fast.  And it's never debris.  Any debris would have been scoured from the aft end of the booster and blasted dozens of miles away by the exhaust of a million and a half pounds of rocket thrust.  Whatever's left would remain firmly attached all the way to the waterline (or, at least, until the atmosphere turned into a corrosive plasma soup).

When in doubt, it's ice.  It's always ice.

[meekGee]

This new Starlink profile doesn’t seem to be working very well so far.

This second recovery failure in a row is disappointing.

A bit premature...  what's next, the "two out of two" crowd?

[meekGee]

From the latest tweet I take it that the failed engine is the same one as the out-of-family abort engine.

[whitelancer64]

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."

Emphasis mine.

Engine out capability of F9 was already demonstrated 7.5 years ago, on 7 October 2012, during the CRS-1 launch.
During that launch, one of the nine Merlin engines blew it's LOX dome and the engine was shutdown roughly 80 seconds into the launch. The primary payload - a cargo Dragon - was successfully delivered into orbit.

Worth noting that the Falcon 9 still had Merlin 1C engines on the CRS-1 launch.

This is the first, so far as I am aware, in-flight failure of a Merlin 1D engine.

[andrewsdanj]

I did notice the entry burn plume did not have the usual plume "diffraction spikes"...

[HVM]

The flash appeared left of center, and the 5 visible plumes looked normal afterward, so maybe it was the lower left engine (seen from the camera POV).

Which engine plume and shutdown phenomenon intersect (most)?

[racevedo88]

Good news Booster accomplished mission delivering satellite and proving reuse up to 5 tomes.  Potential Worry What impact if any does engine failure has on demo 2.  The fact that two Apollo flights and 1 shuttle flight had engine out events, and that Falcon is designed with engine out capability might help to mitigate impact.  But keeping finger crossed

[LaunchedIn68]

A reminder:  every time something goes off-nominal, cries of "debris!" start flying thick and fast.  And it's never debris.  Any debris would have been scoured from the aft end of the booster and blasted dozens of miles away by the exhaust of a million and a half pounds of rocket thrust.  Whatever's left would remain firmly attached all the way to the waterline (or, at least, until the atmosphere turned into a corrosive plasma soup).

When in doubt, it's ice.  It's always ice.

Awful lot of ice every time a booster is lost.  It's always ice, until its not.

[ugordan]

The flash appeared left of center, and the 5 visible plumes looked normal afterward, so maybe it was the lower left engine (seen from the camera POV).

Which engine plume and shutdown phenomenon intersect (most)?

Fun fact: those "petals" where the plume blossoms our are actually locations where adjacent engine plumes collide and escape outward. The actual engine locations would be at midpoints between the green circles you outlined.

[litton4]

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

[yokem55]

Good news Booster accomplished mission delivering satellite and proving reuse up to 5 tomes.  Potential Worry What impact if any does engine failure has on demo 2.  The fact that two Apollo flights and 1 shuttle flight had engine out events, and that Falcon is designed with engine out capability might help to mitigate impact.  But keeping finger crossed

If SpaceX can clearly demonstrate that this engine out was due to the extended re-use of this booster, and not something that could happen in a new vehicle, the impact would be pretty minimal, and should add confidence to Falcon's engine out capabilities. If there is reason to believe this could happen on a new vehicle, well, then there absolutely could be a big delay to fix the issue.

[ZachS09]

https://twitter.com/SpaceX/status/1240285435722706945

[ugordan]

https://twitter.com/SpaceX/status/1240285435722706945

Is this implying that the fairings missed the catcher ships?

Given the loss of thrust on ascent and hence slightly longer time to MECO velocity, the vehicle would have been slightly further downrange than expected and so would the fairings at fairing sep. Not to mention if the engine-out changed burnout altitude due to that delay and hence subsequent apogee of the fairings at release. All this affects impact point at splashdown.

[kevinof]

If this was a center engine then it's possible that it has completed a lot of firings at this stage. 4 flights with 4 ignitions per flight plus 1 test in Texas). That's 17 engine runs for the center engine(s).  Then add this flight of 1 static fire and a launch.

That's a lot of engine time so maybe it was down to the stresses of repeat launches.

Good news Booster accomplished mission delivering satellite and proving reuse up to 5 tomes.  Potential Worry What impact if any does engine failure has on demo 2.  The fact that two Apollo flights and 1 shuttle flight had engine out events, and that Falcon is designed with engine out capability might help to mitigate impact.  But keeping finger crossed

If SpaceX can clearly demonstrate that this engine out was due to the extended re-use of this booster, and not something that could happen in a new vehicle, the impact would be pretty minimal, and should add confidence to Falcon's engine out capabilities. If there is reason to believe this could happen on a new vehicle, well, then there absolutely could be a big delay to fix the issue.

[MKrob89]

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

[XenIneX]

The flash appeared left of center, and the 5 visible plumes looked normal afterward, so maybe it was the lower left engine (seen from the camera POV).

Which engine plume and shutdown phenomenon intersect (most)?

That looks distinctly center-ish to me, and subsequent frames after the transient calmed down look notably symmetrical.  *shrug*

A reminder:  every time something goes off-nominal, cries of "debris!" start flying thick and fast.  And it's never debris.  Any debris would have been scoured from the aft end of the booster and blasted dozens of miles away by the exhaust of a million and a half pounds of rocket thrust.  Whatever's left would remain firmly attached all the way to the waterline (or, at least, until the atmosphere turned into a corrosive plasma soup).

When in doubt, it's ice.  It's always ice.

Awful lot of ice every time a booster is lost.  It's always ice, until its not.

"Awful lot of ice every time a booster is lost."

There's ice every launch.  People just generally don't get too weird about it unless something notable happens.

Note that the specific ice in question seems to come from the vicinity of a cold-gas thruster, just as the booster's doing final alignment for the entry burn.  It's the same kind of ice donut we tend to get around this phase of flight.

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.

https://twitter.com/SpaceX/status/1240285435722706945

Is this implying that the fairings missed the catcher ships?

Given the loss of thrust on ascent and hence slightly longer time to MECO velocity, the vehicle would have been slightly further downrange than expected and so would the fairings at fairing sep. Not to mention if the engine-out changed burnout altitude due to that delay and hence subsequent apogee of the fairings at release. All this affects impact point at splashdown.

Eh.  Paragliders have quite a lot of cross-range.  Given how quickly they scooped them up, I'd still put this down as them not having the "fairing catching thing" not dialed in yet.

[abaddon]

It will be interesting to see what if any impact this has on DM-2 NET ~two months out.  IIRC the return to flight of the Soyuz launch that failed recently was pretty quick.  Of course, not all failures are the same - this one made it to orbit safely with a payload heavier than the Crew Dragon and was on its 5th reuse... if anyone's counting.

In the end, it's a good thing that SpaceX has a high flight rate as it helps expose issues sooner.  There is no quality like quantity when it comes to validating a design.  Better to have this happen here and now than later on a crew flight, success of the payload delivery to orbit notwithstanding.

[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?