SpaceX Falcon 9 FT - ORBCOMM-2 - Dec. 21, 2015 (Return To Flight) DISCUSSION

[NovaSilisko]

Sounds to me like a valve on the ground equipment was opening slower than expected. So the rocket is being told about the delay to compensate.

[Semmel]

Let me rephrase my question: what are the ground valves for?

[to_boldly_go]

Let me rephrase my question: what are the ground valves for?

Generally the purpose of valves is to control the flow of fluids and gasses through pipes... 

[Lars-J]

I really don't get people who complain about SpaceX and transparency.  Musk is often way more transparent than I would be in his position.

Indeed. When a CEO is basically live-tweeting a hot fire troubleshooting, all complaints of lack of transparency should be out the window. But then again, we did have a poster complain about DoD levels of secrecy a few pages back. 

[411rocket]

Elon Musk ‏@elonmusk  27s27 seconds ago
Aborted on ignition timing due to slow ground side valve. Adjusting ignition sequence by 0.6 secs for next attempt.

Sounds like the rocket is behaving, but the GSE let them down on that attempt.

Willing to entertain thoughts

Should have used Dev2, to do pad workups, like done in Vandy.

[Craftyatom]

Elon Musk ‏@elonmusk  27s27 seconds ago
Aborted on ignition timing due to slow ground side valve. Adjusting ignition sequence by 0.6 secs for next attempt.

Sounds like the rocket is behaving, but the GSE let them down on that attempt.

Willing to entertain thoughts

Should have used Dev2, to do pad workups, like done in Vandy.

To be fair, the previous attempt was aborted due to a second stage issue.  So while they would've caught a lot of issues, it wouldn't have been flawless.

[cscott]

Probably they don't want to light the candle until they get confirmation the ground side LOX supply valves are closed.  Humidity and cryo temps making the Canaveral LOX valve a little sticky.

I'm guessing this is the LOX valve, not kero, because supercooling pretty much dictates continual active cooling/replenish of LOX preflight.  Makes sense they'd want to keep that going until the last possible moment in order to launch with LOX as cold as possible.

[CorvusCorax]

with what we know that would be speculation, but there's
- ground based valves for 1st stage kerosene feed input (multiple along the line plus safety redundants)
- ground based valves for 1st stage kerosene detanking (dito ...)
- ground based valves for 1st stage lox feed (...)
- ground based valves for 1st stage lox detanking
- ... same for 2nd stage ...
- ... and possibly payload (not used on this mission, but valves might be present for future/dragon flight)
- Niagara sound supression system water flush valves
- fire prevention/extinction system liquid valves
- valves for LOX coolant (liquid N2?)
- feed/release valves for auxilliary fluids (liquid He for tank pressurization, nitrogen thruster tanks, ...) (are they fed on pad or pre-filled in hangar?)
- fresh and greywater for pad facility lavatories
- ...

if you think about it for a while, theres ****loads of valves on a pad, maybe even more than on an oilrig

[Dante80]

Its a launch pad, of course there are a lot of valves!

- fresh and greywater for pad facility lavatories

This made me chuckle. 

"Elon Musk ‏@elonmusk  27s27 seconds ago
Aborted on ignition timing due to slow pad lavatory valve (LPLV). Asking all personnel to wear diapers/hold it for next attempt."

[nadreck]

with what we know that would be speculation, but there's
- ground based valves for 1st stage kerosene feed input (multiple along the line plus safety redundants)
- ground based valves for 1st stage kerosene detanking (dito ...)
- ground based valves for 1st stage lox feed (...)
- ground based valves for 1st stage lox detanking
- ... same for 2nd stage ...
- ... and possibly payload (not used on this mission, but valves might be present for future/dragon flight)
- Niagara sound supression system water flush valves
- fire prevention/extinction system liquid valves
- valves for LOX coolant (liquid N2?)
- feed/release valves for auxilliary fluids (liquid He for tank pressurization, nitrogen thruster tanks, ...) (are they fed on pad or pre-filled in hangar?)
- fresh and greywater for pad facility lavatories
- ...

if you think about it for a while, theres ****loads of valves on a pad, maybe even more than on an oilrig

But we can eliminate some of those valves knowing that they didn't need to change position just at or just before ignition:

No one flushed the loo just before ignition so that leaves out those associated with the lavatories ...

I make a distinction between valves on feeds (and drains) going between the craft and the ground facilities because the valves that are needed for the sound suppression, etc are not as likely to be affected by the subcooled LOX, or anything that happened on the spacecraft, but the pressurant lines, LOX lines may well be behaving differently than previous launch attempts because of the subcooled LOX

[411rocket]

Sounds like the rocket is behaving, but the GSE let them down on that attempt.

Willing to entertain thoughts

Should have used Dev2, to do pad workups, like done in Vandy.

To be fair, the previous attempt was aborted due to a second stage issue.  So while they would've caught a lot of issues, it wouldn't have been flawless.

True, but we could have possibly, saved a day or two, in this static fire effort.

[mtakala24]

Elon Musk ‏@elonmusk  7s7 seconds ago
Rounding up to 1 sec for a bit of timing margin. Updating flight computer command sequence …

[andrewsdanj]

...that's the language of an excited ubergeek. Go temporarily light that candle!

[cro-magnon gramps]

...that's the language of an excited ubergeek. Go temporarily light that candle!

refresh, Refresh, REFRESH!! Where is the Candle...

[Lee Jay]

Elon Musk ‏@elonmusk  7s7 seconds ago
Rounding up to 1 sec for a bit of timing margin. Updating flight computer command sequence …

I have personal experience with equipment (not mine) failing catastrophically after people started opening up timing windows to account for other faulty equipment.

I've been pretty horribly uncomfortable with any such "pennies in the fuse box" ever since.

[laika_fr]

sounds like a classic auto-sequence calibration they've done the same with previous versions

[Mike_1179]

From the Update thread:

L2 now has an instantaneous T-0 of 20:29 Eastern for the attempt on the 20th. Previously was a three hour window. Next opportunity on the 22nd is showing a 15 minute window!

Window changing from three hours to instantaneous.

Is that because they are making a change to the vehicle so that it doesn't have the performance needed to support a 3 hour window? Not cooling the LOX so much perhaps?

[mtakala24]

Things seem to have gone quiet for today. Going to catch some sleep soon..

[Craftyatom]

From the Update thread:

L2 now has an instantaneous T-0 of 20:29 Eastern for the attempt on the 20th. Previously was a three hour window. Next opportunity on the 22nd is showing a 15 minute window!

Window changing from three hours to instantaneous.

Is that because they are making a change to the vehicle so that it doesn't have the performance needed to support a 3 hour window? Not cooling the LOX so much perhaps?

I wouldn't think so, my guess is that they're not going to change anything, especially since they've put so much planning (and now two days at the pad) into getting it to work.  My (admittedly uneducated) guess is that it's to do with orbital inclination, and wanting to get everything done in one S2 burn.

[Proponent]

I really don't get people who complain about SpaceX and transparency.  Musk is often way more transparent than I would be in his position.

On the other hand, compare the amount of information in the Falcon 9 Payload User's Guide with the equivalents for Atlas V and Delta IV.  SpaceX is sometimes less transparent.