Author Topic: Delta IV-H - NROL-71 - January 19, 2019  (Read 81327 times)

Offline Steven Pietrobon

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Unexpected condition at T-7.5 s.

"8:57 p.m. PST (11:57 p.m. EST; 0457 UTC)
(Vandenberg Air Force Base, Calif., Dec. 8, 2018) ĖThe launch of a United Launch Alliance Delta IV Heavy carrying the NROL-71 mission for the National Reconnaissance Office was scrubbed today due to an unexpected condition during terminal count at approximately 7.5 seconds before liftoff. The team is currently reviewing all data and will determine the path forward. A new launch date will be provided when available."
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Offline zubenelgenubi

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Correct me if I'm wrong:
Troubleshooting a redundant circuit in the holdfire circuitry is what scrubbed the first launch attempt.

Scrubbing the second launch attempt at T-7.5 seconds would have required the use of the holdfire circuitry?
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Online niwax

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Do we know if the cores need some kind of refurbishment if the insulation has been singed?
Which booster has the most soot? SpaceX booster launch history!

Online DaveS

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Correct me if I'm wrong:
Troubleshooting a redundant circuit in the holdfire circuitry is what scrubbed the first launch attempt.

Scrubbing the second launch attempt at T-7.5 seconds would have required the use of the holdfire circuitry?
No. The holdfire command is an Range-only command which is used by the ROC to manually command a hold. It has nothing to do with Terminal Countdown Sequencer Rack (TCSR) which is what kicked them out of the count.
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Offline Star One

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Someone suggested around the time of the Parker Solar Probe scrub, that this vehicle gets a lot of scrubs because it just doesnít fly very often?

Online ugordan

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Someone suggested around the time of the Parker Solar Probe scrub, that this vehicle gets a lot of scrubs because it just doesnít fly very often?

Yes, it appears to be much more... temperamental, even in the single-stick configuration than the Atlas. Mostly on the GSE side, IIRC.

Offline MattBaker

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And the Delta IV (any configuration) doesn't fly very often from Vandenberg either, two mediums in January and 2016, the last Heavy was over five years ago. It's pretty much exclusively an NRO launchpad and they only need it every year or two.

Online LouScheffer

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Someone suggested around the time of the Parker Solar Probe scrub, that this vehicle gets a lot of scrubs because it just doesnít fly very often?
Yes, this same observation, speculating on the same cause, was made at the time of the PSP scrubs...

Online edkyle99

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Has Delta (any variant) had an ignition time abort before?
Apparently not:
The previous abort shows that the ROFIs produce a lot of smoke all by themselves, possibly accounting for much of the smoke seen last night.

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Offline Newton_V

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Offline Lee Jay

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Then I'm confused. If the engines didn't start, why did they confirm MECO?

Online Lars-J

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Then I'm confused. If the engines didn't start, why did they confirm MECO?

Itís the dark secret of rocket launch broadcasts... most of the time they read off a script. :-) All providers do this more or less.
« Last Edit: 12/10/2018 03:27 am by Lars-J »

Offline Newton_V

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Then I'm confused. If the engines didn't start, why did they confirm MECO?
Inexperience maybe?  Confusion?  There's a lot going on in a few seconds there.  I didn't hear what was called, but a "script" has nothing to do with real callouts of telemetry.  Scripts are for calling out major events by a "PR" person, looking at nominal preflight timelines, and a list of mark events as they're happening.  They would have called liftoff at time-zero, even if the engines shut off at T-1 seconds because it's takes a second to say "liftoff".
On the internal nets are chief engineers or certified people looking at real-time telemetry and making callouts and more detailed information about specific systems.
« Last Edit: 12/10/2018 03:57 am by Newton_V »

Offline Lee Jay

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Then I'm confused. If the engines didn't start, why did they confirm MECO?

Itís the dark secret of rocket launch broadcasts... most of the time they read off a script. :-) All providers do this more or less.

Yeah...but it sounded like it came from the loop, not the announcer, and it was quite a bit after the event.  Also, the announcer wouldn't have MECO in the script until many minutes later and even then, only if there were a launch.

Offline RonM

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Then I'm confused. If the engines didn't start, why did they confirm MECO?

Itís the dark secret of rocket launch broadcasts... most of the time they read off a script. :-) All providers do this more or less.

Yeah...but it sounded like it came from the loop, not the announcer, and it was quite a bit after the event.  Also, the announcer wouldn't have MECO in the script until many minutes later and even then, only if there were a launch.

They follow check lists. Confirming MECO is probably on the page for last few seconds launch abort.

Offline clongton

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So did the TCSR command the abort or was it manually initiated following some telemetry observation?
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Offline Newton_V

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So did the TCSR command the abort or was it manually initiated following some telemetry observation?
TCSR commanded abort.

Online dglow

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To confirm, we did have engine start on the DIVH.  Abort was triggered almost right at that time.  MECO was confirmed by ULA engineers several (several) seconds thereafter. 

The "fire" was the start of the nominal burn off of the ambient LH2 the surrounds the DIVH.

The abort happened before engine start.

Then I'm confused. If the engines didn't start, why did they confirm MECO?

The abort occurred before any engines ignited, yes Ė and while LH2 wasn't flowing yet it would have been very soon. But some amount of LOX had been released for engine chilldown, so I'd wager MECO was called to verify all prop valves were fully closed.

Online Michael Baylor

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