SpaceX Falcon 9 v1.1 - SES-8 - DISCUSSION THREAD

[Lars_J]

Why is the next launch window only on thursday? I thought there would be a window to GTO daily. Or is it time they need to ready the launch vehicle again?

Thanks.

It was mentioned somewhere that tomorrow and Wednesday are the busiest travel days of the year, so I presume they won't be allowed to shut down the airspace around CCAFS. I might be wrong.

[Halidon]

The umbilical which disconnects from the fairing in that video doesn't look like it had anywhere near the slack it would need to stay connected after strongback retraction. Either it was planned to disconnect or they installed completely the wrong size.

[Mapperuo]

The umbilical which disconnects from the fairing in that video doesn't look like it had anywhere near the slack it would need to stay connected after strongback retraction. Either it was planned to disconnect or they installed completely the wrong size.

Looks like to me it's folded half way along the hose and held up to keep the slack tidy until it's needed to be extended, clearly didn't move when the Erector lowered though.

[cambrianera]

Looked at the F9-Cassiope video; the fairing umbilical seems to be released at +4 s during liftoff (see pics).

[WHAP]

Why is the next launch window only on thursday? I thought there would be a window to GTO daily. Or is it time they need to ready the launch vehicle again?

Thanks.

At this point, I'd be more concerned about the spacecraft than anything else.  There's no reason to expect that the launch vehicle isn't healthy.  But loss of ac to the spacecraft, if that's really what happened, is not good.  Spacecraft are typically very concerned about excursions beyond specified conditions for even a short duration, and those conditions probably can't be maintained without environmental conditioning. 

Of course, SpaceX still need to troubleshoot and correct whatever caused the abort as well, and we have no idea how long that will take. 

[Avron]

Looked at the F9-Cassiope video; the fairing umbilical seems to be released at +4 s during liftoff (see pics).

Yes, that's what I recall, so there is an issue or a redesign.. That umbilical, did not extend to the point shown during yesterdays attempt. I can remember wondering why so late in the launch T+4 is late.. well yesterday it was closer to T-4

[Kabloona]

Why is the next launch window only on thursday? I thought there would be a window to GTO daily. Or is it time they need to ready the launch vehicle again?

Thanks.

At this point, I'd be more concerned about the spacecraft than anything else.  There's no reason to expect that the launch vehicle isn't healthy.  But loss of ac to the spacecraft, if that's really what happened, is not good.  Spacecraft are typically very concerned about excursions beyond specified conditions for even a short duration, and those conditions probably can't be maintained without environmental conditioning. 

Of course, SpaceX still need to troubleshoot and correct whatever caused the abort as well, and we have no idea how long that will take.

It was reported on another site that FAA would not grant a launch license for Tues or Weds due to heavy air travel.

As for SES-8, the sun had already set and ambient temps were moderate and dropping when the duct detached, and the spacecraft probably wasn't generating much heat itself, so hopefully it wasn't a big deal.

[Rocket Science]

My impression for what its worth....Every SpaceX launch from that pad in one way or another has had Lox issues.
This launch was like a completely different from the Vandenberg launch.  In that launch the sb moved back and the noticeable pressure of the connections.   Did the SB retract all the way in this launch, or have the procedures changed?
 

I was looking at that.. looks like it stops at the venting associated with the abort .. cannot be sure

I saw that as well, a massive vent with the coinciding with the call...

Just depressing the tanks.. something that tells me that they have aborted... remember the tanks get pressurized for launch..

Yes, and perhaps over pressurized?

Negative. Flight pressure is significantly higher than the standard pre-launch post-tanking pressure. So what you saw was the immediate release of that delta pressure (delta-p) when the automatic sequencer cut-off the count and commanded the stage 1 vent valve to full open. This rapid change in pressure caused the stage to vibrate enough to dislodge some of the ice that had formed on the exterior of the stage 1 LOX tank.

It was nothing anomalous, it was exactly how the system should work as the last thing you'd want in a case like this is a potential unstable bomb just waiting to detonate. By fully opening the vent valve you remove that extra pressure inside the tank that is no longer necessary.
Remember, LOX is a cryogenic liquid that keeps boiling off and turning into GOX. This GOX increases the pressure inside the tank so it needs somewhere to go unless you want the tank to overpressurize and explode. This is handled by a pressure relief valve at the top of the tank. The excess GOX is vented overboard and there's no risk of overpressure unless the relief valve fails in the closed position.

Thanks for your comment Dave, I’m aware of this. My point was that it “may” have exceeded nominal flight pressure requiring a dump. The video/audio may be slightly out of sync on my end as I saw and heard it... If they already suspect a valve then that’s good news, the other issues not so much...

[Jim]

As for SES-8, the sun had already set and ambient temps were moderate and dropping when the duct detached, and the spacecraft probably wasn't generating much heat itself, so hopefully it wasn't a big deal.

Contamination and humidity would be issues.  Moist air entering could have condensed on cool spacecraft surfaces.

[DaveS]

As for SES-8, the sun had already set and ambient temps were moderate and dropping when the duct detached, and the spacecraft probably wasn't generating much heat itself, so hopefully it wasn't a big deal.

Contamination and humidity would be issues.  Moist air entering could have condensed on cool spacecraft surfaces.

Yes. Wasn't there an accidental AC duct umbilical detach a few years back that occurred during the scrub turnaround activities on a Delta II launch from SLC-2W at Vandenberg AFB? They had to check the spacecraft and the inside of the payload fairing for contamination before a new launch attempt could be OK'ed?

[ugordan]

Re the A/C premature disconnect: how ironic given that when Antares had a premature disconnect on its first launch attempt, one (now former) SpaceXer tweeted that their quick disconnect designer "just burst out laughing"...

Not so funny now, is it?

[Kabloona]

Speaking of A/C duct mishaps, I seem to recall that after the Mars Observer/Commercial Titan stack was secured on the pad in advance of Hurricane Andrew, after the storm blew through, the duct was reattached to the PLF ans blew contamination all over the spacecraft. It had to be destacked, cleaned, and restacked, with a week launch slip.

Hopefully not the case here.

[rsnellenberger]

As for SES-8, the sun had already set and ambient temps were moderate and dropping when the duct detached, and the spacecraft probably wasn't generating much heat itself, so hopefully it wasn't a big deal.

Contamination and humidity would be issues.  Moist air entering could have condensed on cool spacecraft surfaces.

Wouldn't there be a cover that drops into place after the umbilical detaches?

[cambrianera]

Looked at the F9-Cassiope video; the fairing umbilical seems to be released at +4 s during liftoff (see pics).

Yes, that's what I recall, so there is an issue or a redesign.. That umbilical, did not extend to the point shown during yesterdays attempt. I can remember wondering why so late in the launch T+4 is late.. well yesterday it was closer to T-4

Yesterday it was -4m21s, during strongback retraction.
The release of F9-Cassiope umbilicals seems entirely consequence of the pull of the rocket during liftoff.

[eriblo]

Re the A/C premature disconnect: how ironic given that when Antares had a premature disconnect on its first launch attempt, one (now former) SpaceXer tweeted that their quick disconnect designer "just burst out laughing"...

Not so funny now, is it?

I'm curious whether it was the "Ha ha, amateurs!" or the "Ha ha, 'twitch', he he... 'stuff of my nightmares', he he...'I'm going to cry now'" kind of laugh 

[Prober]

Looked at the F9-Cassiope video; the fairing umbilical seems to be released at +4 s during liftoff (see pics).

Yes, that's what I recall, so there is an issue or a redesign.. That umbilical, did not extend to the point shown during yesterdays attempt. I can remember wondering why so late in the launch T+4 is late.. well yesterday it was closer to T-4

Yesterday it was -4m21s, during strongback retraction.
The release of F9-Cassiope umbilicals seems entirely consequence of the pull of the rocket during liftoff.

just watched this:  http://new.livestream.com/spacex/F9-6     Just a whole different feeling.

[Norm38]

Contamination and humidity would be issues.  Moist air entering could have condensed on cool spacecraft surfaces.

Wouldn't there be a cover that drops into place after the umbilical detaches?

That's a good point. If the umbilical detach just leaves an open hole into the fairing, then what keeps moisture out during the first few minute of flight, especially at max Q?  Would they really just count on airflow creating low pressure?

[Jim]

That's a good point. If the umbilical detach just leaves an open hole into the fairing, then what keeps moisture out during the first few minute of flight, especially at max Q?  Would they really just count on airflow creating low pressure?

There are other "holes" in the fairing.   The pressure in the fairing is higher than outside due to the vehicle climbing in the atmosphere. There are vents to relieve the internal pressure as the vehicle ascents.  These vents are also where the AC purge air leaves the fairing while on the pad.

[Lurker Steve]

Why is the next launch window only on thursday? I thought there would be a window to GTO daily. Or is it time they need to ready the launch vehicle again?

Thanks.

It was mentioned somewhere that tomorrow and Wednesday are the busiest travel days of the year, so I presume they won't be allowed to shut down the airspace around CCAFS. I might be wrong.

How difficult is it to convince the Air Force guys who operate the range to work on a Holiday ? They aren't SpaceX employees. They have families also.
 

[rds100]

I thought AF personnel works 24/7, regardless of any holidays, launches, etc. ?