SpaceX Falcon 9 : GPS III SV04 : SLC-40 : November 5, 2020

[zubenelgenubi]

Status questions:
Is the LV still vertical at the pad?

Will the repair (or remove and replace) work be performed at the pad, or back in the SLC-40 HIF?

And scheduling questions:
How long will repair (or R&R) take?

Might SpaceX proceed with the Starlink v1.0 Flight 13 campaign (possible Static Fire, then launch), at the same location, while the GPS LV is "in the shop?"

[CorvusCorax]

It would be glad to know then what "turbomachinery gas generator" is because, as the phrase indicates, it has nothing to do witht the main RP-1 and LOX pumps but rather with the gas generator. As you say, it doesn't have any pumps or something like that. Then what's that turbomachinery all about?

let's ride this dead horse a bit longer.

the "turbomachinery gas generator" is the gas generator that creates the hot high pressure gas for the turbine that in turn drives the propellant pumps. Because these pumps are driven by a turbine, they are called "turbopumps".

The entirety of gas generator, turbine and turbopumps is sometimes called "turbomachinery".

with the Merlin, the main combustion chamber could in technically also be called "thrust gas generator" as opposed to the "turbomachinery gas generator". This is because both the "main combustion chamber" and "turbopump combustion chamber" in the Merlin1D are supplied with the very same ingredients: high pressure liquid kerosine (RP1) and oxygen, supplied by the turbopumps, which then burns to produce high pressure exhaust gas. In both cases it is pressed through a nozzle - the small one drives a turbine, the big one pushes the rocket.

so the terms "combustion chamber" and "gas generator" can technically be used interchangeably on this kind of engine.

To tell the 2 chambers apart it kinda makes sense to call one "thrust chamber" and the other "turbomachinery gas generator" - you have then disambiguated the terms.

That being said, in practice, when someone says "gas generator" they typically mean "turbomachinery gas generator" - afaik it's not particularly common to refer to the main combustion chamber like that. But then again, we shouldn't complain if Elon is being specific.

[soltasto]

Did anyone else note that the SpaceX webcast announcer said “.. four...three...” but never said “two” as the abort occurred around two seconds before scheduled launch.
Contrast this with Delta IV Heavy where the announcer kept counting through “Liftoff” although their abort happened several seconds earlier.
That may say something about the structure of the two organizations, flatter vs. hierarchical.

The SpaceX webcast also switches completely to the main countdown loop during the last seconds and for a while after T-0, so the announcer in that moments is actually someone in Mission Control or Launch Control who has access to the real information, not only to what is relayed to them. The SpaceX webcast Timer is also directly hooked up with the real timer, so the other commentators can actually see the real number. The ULA one is most likely a simulated one as they remove it prior to liftoff. So if an abort happens the ULA webcast team may not know that it happened for a while,

[kdhilliard]

Did anyone else note that the SpaceX webcast announcer said “.. four...three...” but never said “two” as the abort occurred around two seconds before scheduled launch. ...

She was on the ball.


What did you make of the one second flash of light which occurred at the base of the Falcon 9 shortly after that?

I don't know how synchronized the video is with the countdown net or the on-screen countdown clock, but if I call the moment that "T-00:00:02" appeared as T-2.00s, then a flash started slowly building at T-1.23s and was near its full brightness at T-0.27s before abruptly disappearing one frame later (on the 30 fps YouTube video) at T-0.23s.  Much was obscured by the drifting clouds of condensation, but was it green enough to be TEA-TEB?

Here is the webcast set to T-10s: https://youtube.com/watch?v=JESG7x0X0ek&t=1002

Screencaps:
16:50F20 - T-1.27s Immediately before start of flash
16:51F03 - T-0.83s Full flash
16:51F20 - T-0.27s Last frame of flash
16:51F21 - T-0.23s Flash abruptly extinguished

[soltasto]

Did anyone else note that the SpaceX webcast announcer said “.. four...three...” but never said “two” as the abort occurred around two seconds before scheduled launch. ...

She was on the ball.


What did you make of the one second flash of light which occurred at the base of the Falcon 9 shortly after that?

I don't know how synchronized the video is with the countdown net or the on-screen countdown clock, but if I call the moment that "T-00:00:02" appeared as T-2.00s, then a flash started slowly building at T-1.23s and was near its full brightness at T-0.27s before abruptly disappearing one frame later (on the 30 fps YouTube video) at T-0.23s.  Much was obscured by the drifting clouds of condensation, but was it green enough to be TEA-TEB?

Here is the webcast set to T-10s: https://youtube.com/watch?v=JESG7x0X0ek&t=1002

Screencaps:
16:50F20 - T-1.27s Immediately before start of flash
16:51F03 - T-0.83s Full flash
16:51F20 - T-0.27s Last frame of flash
16:51F21 - T-0.23s Flash abruptly extinguished

As the issue was with the gas generators, and as those ignite with TEA-TEB too, I would say that TEA-TEB was definitely involved. The count most definitely stopped at T-2.something (They truncate it for the webcast as from T-0 to T+0 there is a full second as well as from T+0 to T+1 second) but once you release the TEA-TEB it will still take a while to burn. The video feed from florida is also a bit delayed compared to the timer which is most likely based on the Mission Control one so that adds up to the offset.
TLDR: There are transients and delays

[kdhilliard]

As the issue was with the gas generators, and as those ignite with TEA-TEB too, I would say that TEA-TEB was definitely involved. ...

And the brighter green flashes we see on normal engine starts would be from the TEA-TEB ignition of the main combustion chambers.  So it makes sense we'd see only a muted flash for an aborted, partial start.

[CorvusCorax]

I would not read too much into the flashes.

We don't know if the startup of the engine's is currently staggered or simultaneous. Even if it's simultaneous, we don't know if the flash is from the engine that caused the abort or from another and if that other engine possibly went further along its startup sequence than the abort-causing one.

It's thinkable that the engine that had the unexpected pressure rise was still in the spoolup or pre-ignition phase of it's preburner, while another engine was already feeding TEA/TEB to it's main combustion chamber. In such a case we would see the green flash from the latter engine, which got further along in the sequence until the commanded abort, while the "culprit" so to speak would have given no visible evidence at all.

Of course the green flash *could* actually be from the problematic engine, but we just can't tell without more info from SpaceX - There's 9 engines there after all

[the_other_Doug]

My impression was that I saw the green stutter-flash of the igniters, but not the orange-to-white color of a Merlin engine's exhaust as it starts up.

I wonder if the Merlins ever started to flow props?  Didn't really look like it, to me...

[CorvusCorax]

My impression was that I saw the green stutter-flash of the igniters, but not the orange-to-white color of a Merlin engine's exhaust as it starts up.

I wonder if the Merlins ever started to flow props?  Didn't really look like it, to me...

There also was no bellowing of steam from the flame trench. If any significant amount had come out of any engine, I think we'd have seen at least a "burp" in form of a steam cloud from there, the only clouds I saw were the usual condensation clouds from the cryogenic plumbing and pre-chill.

[The Roadie]

let's ride this dead horse a bit longer....

...This is because both the "main combustion chamber" and "turbopump combustion chamber" in the Merlin1D are supplied with the very same ingredients: high pressure liquid kerosine (RP1) and oxygen, supplied by the turbopumps, which then burns to produce high pressure exhaust gas.

During start-up of the GG, there is no high pressure RP1 or LOX because the common shaft is not turning the impellers yet. (I don't believe GSE is supplying such propellant because the Merlin wouldn't have that available in flight for a restart.)

The volutes are at low pressure, or at least not acting as a typical mechanical load on the shaft, or else the helium turbine wheel spin-up couldn't happen. I think the issue being discussed isn't the existence of the high pressure, high volume pumps, but the existence of any smaller pumps before the GG burner to give it starting propellant so its TEA-TEB charge can get it ignited. I'm speculating the GG just starts up using normal low pressure propellant from the tank-fed plumbing.

[The Roadie]

Here's a photo from Teslarati I edited to add callouts for the various parts. It's been difficult to locate a photo that shows the GG burner attached to the turbine wheel housing, and I needed this for an educational trivia quiz I was running. We were also discussing the fact that on the MVac the turbopump is mounted so it gimbals with the engine, but on the M1D, it's fixed to the main engine plate and the high pressure propellant lines have to accommodate the gimbaling.

[XenIneX]

Did anyone else note that the SpaceX webcast announcer said “.. four...three...” but never said “two” as the abort occurred around two seconds before scheduled launch. ...

She was on the ball.


What did you make of the one second flash of light which occurred at the base of the Falcon 9 shortly after that?

I don't know how synchronized the video is with the countdown net or the on-screen countdown clock, but if I call the moment that "T-00:00:02" appeared as T-2.00s, then a flash started slowly building at T-1.23s and was near its full brightness at T-0.27s before abruptly disappearing one frame later (on the 30 fps YouTube video) at T-0.23s.  Much was obscured by the drifting clouds of condensation, but was it green enough to be TEA-TEB?

Here is the webcast set to T-10s: https://youtube.com/watch?v=JESG7x0X0ek&t=1002

Screencaps:
16:50F20 - T-1.27s Immediately before start of flash
16:51F03 - T-0.83s Full flash
16:51F20 - T-0.27s Last frame of flash
16:51F21 - T-0.23s Flash abruptly extinguished

You missed a step...

16:50F26 - T-1.07s Vents at interstage surge, indicating depressurization

[CorvusCorax]

During start-up of the GG, there is no high pressure RP1 or LOX because the common shaft is not turning the impellers yet. (I don't believe GSE is supplying such propellant because the Merlin wouldn't have that available in flight for a restart.)

The volutes are at low pressure, or at least not acting as a typical mechanical load on the shaft, or else the helium turbine wheel spin-up couldn't happen. I think the issue being discussed isn't the existence of the high pressure, high volume pumps, but the existence of any smaller pumps before the GG burner to give it starting propellant so its TEA-TEB charge can get it ignited. I'm speculating the GG just starts up using normal low pressure propellant from the tank-fed plumbing.

I think so, too. It's possible to start a rocket engine without helium spinup. The A4 was started like that, propellant was being pushed through the turbo pump by tank pressure and ignited in the main combustion chamber several seconds before the gas generator was even activated, which then spun up the turbopump to high speeds - increasing pressure, flow and thrust to flight levels.

Same with RS-25 http://large.stanford.edu/courses/2011/ph240/nguyen1/docs/SSME_PRESENTATION.pdf -- there is no helium spinup, the engine spools up using tank pressure only (helium is used to purge and equalize the POGO accumulator between the pump stages during startup though)

Merlin1D needs to start up quicker for in flight relight, so the turbine spin up is accelerated by releasing high pressure helium into the gas generator andturbine. But there is no need for any extra pumps, nor would anyone spin up the turbine with the main fuel/oxygen valves closed- that'd be horrible - the pump would cavitate and the turbine would rapidly overspeed, only to be violently slowed down once the propellant valves are finally opened. Recipe for disaster!

The entire point of the helium spin start is to get the fuel and oxygen flowing through the pumps at sufficient speed and pressure to both ignite the pre-burner combustion chamber and reach steady state combustion as quickly as possible. The moment the fire is lit, the exhaust gasses take over for the high pressure helium (Or steam from peroxide decomposition in case of Soyuz, or gunpowder-smoke in case of Titan1) and drive the turbine from then on.

A video about various rockets engine startup sequences - including Falcon9

[Michael Baylor]

Falcon 9 is horizontal.

[Ben the Space Brit]

Engines need access only possible in the HIF?

[Lars-J]

Engines need access only possible in the HIF?

The most likely explanation, yes.

[oldAtlas_Eguy]

If there is going to be a n engine swap they will likely need to remove from the strongback. But for just inspection and minor "repair" it would remain on the strongback. There is a lot more equipment in the HIF for inspection and testing.

Also with NRO-108 showing a NET 10-25-20 date. That gives SpaceX 4 days to get GPS back onto the pad for launch on or about 10-11-20.

Without SpaceX statements as to what they are doing all schedule and hardware actions are just speculation.

[gongora]

https://twitter.com/SpaceXFleet/status/1313594783408029698

It would appear that SpaceX is standing down the droneship for the GPS mission and recalling it to Port Canaveral.

Tug Hawk and Just Read the Instructions droneship got underway from the LZ shortly after the Starlink mission earlier today.

[zubenelgenubi]

What a spaghetti schedule.

Looking ahead at the Space Coast launch schedule for the rest of October and the first half of November:

Scheduled:
Date - Satellite(s) - Rocket - Launch Site - Time (UTC)

2020
October 3 TBD - GPS III SV04 - Falcon 9-095 (B1062.1 S) - Canaveral SLC-40 - ~01:00 01:43
(15 minute launch window; launch about 4 minutes earlier/day)
October 1 16 - NROL-44: Orion 10 (RIO 10, Mission 8306, Mentor 8 ) (TBD) - Delta IV-H [D-385] - Canaveral SLC-37B - 02:00-06:42
(launch about 4 minutes earlier/day)
NET October 10 TBD - Starlink flight 14 (x60) [v1.0 L13] - Falcon 9-096 (B1051.6 S) - Canaveral SLC-40 / Kennedy LC-39A - 15:01-16:18
October - NROL-101 - Atlas V 531 (AV-090) - Canaveral SLC-41
NET October 25 - NROL-108 -  Falcon 9 - Canaveral SLC-40
October 31 - USCV-1: Dragon v2 "Resilience" Crew-1 - Falcon 9 (B1061.1 S) - Kennedy LC-39A - 06:40
(launch 22-26 minutes earlier/day)
November 6 - SiriusXM SXM-7 - Falcon 9 - Canaveral SLC-40 Kennedy LC-39A

Changes on October 1st
Changes on October 2nd
Changes on October 3rd
Changes on October 4th
Changes on October 5th
Changes on October 6th
Changes on October 7th
Changes by zubenelgenubi

EDIT: There's a little more information than posted here in the respective L2 sub-forums.

[Ben the Space Brit]

Is there any solid information about what needs to be done to this launcher and the likely time-line until it is ready to launch again?