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

[AJA]

1. I think it's a bit patronizing to assume that those staffing the requisite equipment at CCAFS aren't as excited about supporting a rocket launch as SpaceX is - Thanksgiving or not. Also, if most of them are contractors, wouldn't it make more sense for SpaceX to table a bid, offering to replace the current contractors? Might work out cheaper for both SpaceX and USAF? (Given there's no intermediary with its own profit margin). Especially seeing as they're going to be using SLC-40 quite a lot. (Of course, this depends on how long is left on the current contract and the legal procedures for such things.)

2.

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.

No Venturi effect sucking air out from the fairing?

Plus, aren't these 'holes' valved to allow inside to outside purge only? In which case the only valve that would allow air "in" would be the one whose umbilical was just disconnected. In which case, couldn't you design the delta-p head required to open the valve to be large enough such that ambient winds etc. wouldn't be strong enough?

3.

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.
...
...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.

...My point was that it “may” have exceeded nominal flight pressure requiring a dump...

Same question. What's the design of these vent valves? If they've to be commanded to open, does that imply that there's no mechanical path that automatically acts as a relief? i.e. if delta-p is a certain limit, then the valve is forced open by the higher inside pressures - regardless of whether it's commanded to do so.. Not an irreversible valve failure in the open position, but something like a high tension spring, which you can wind up pre-launch to give way when you approach a red-line pressure - as opposed to sensing it with a transducer and then commanding the valve to open by energising whatever coil mechanism (this could fail in a valve-closed position due to software/instrumentation/actuator failure).

DaveS, you say that flight pressures are more than the pad pressures (during, or post tanking). Are you referring to the pressure head of the prop available at the turbo-pumps/pressure feed points into the combustion chamber (which would be larger for an accelerating vehicle, than a stationary one - with the same volume of propellant in the tank) - or do you mean to say that the gas pressure above the free surface of the prop is higher when in flight, than on the ground? The latter shouldn't be affected by the acceleration of the rocket, so if you are indeed, referring to this, then do the rates of pumping of He into the tanks increase that much as you climb uphill? Reason I ask, is of course, because the vent valves would only care about the gas pressure in the propellant tank, and not the fluid column pressure.

[Chris Bergin]

Thanks chaps. Edited the line about the erector (didn't know that!).

[Jim]

Also, if most of them are contractors, wouldn't it make more sense for SpaceX to table a bid, offering to replace the current contractors? Might work out cheaper for both SpaceX and USAF?

No.  There is nothing to base that claim on.
A.  Spacex has no experience in running the range and base.
b.  It would be a conflict of interest.  Spacex would have to support ULA, LM, Boeing, etc.

[Jim]

Plus, aren't these 'holes' valved to allow inside to outside purge only? In which case the only valve that would allow air "in" would be the one whose umbilical was just disconnected. In which case, couldn't you design the delta-p head required to open the valve to be large enough such that ambient winds etc. wouldn't be strong enough?

No, because they are too big. 
Design the umbilical so that is doesn't accidentally disconnect.

[AndyX]

Copying over from the launch thread for the discussion thread:

So rather than another revision of William's article, I've written up a standalone article to expand on the three holds during the scrub, following collation of information in L2's F9/SES-8 section.

Include's MeekGee's F9 logo redesign to mark the Thanksgiving target

http://www.nasaspaceflight.com/2013/11/falcon-9-aiming-thanksgiving-launch-ses-8/

Great read as always Chris! And Happy Birthday!

[MP99]

Thread trimmed. Some of the posts were worse than the party thread.

Have a think before posting. Seriously.

Party threads are a pressure release mechanism.

Maybe the valve on that thread is out-of-family? :-)

Cheers, Martim

[DFSL]

The title of the article on the NSF page should be "Falcon 9 v1.1 aiming for Thanksgiving launch after three consecutive holds" , "Problematic start for the new Falcon" or "Debut of new Falcon plagued by last minute issues", that way it would match the patronizing tone used for other launchers.

[Mader Levap]

The title of the article on the NSF page should be "Falcon 9 v1.1 aiming for Thanksgiving launch after three consecutive holds" , "Problematic start for the new Falcon" or "Debut of new Falcon plagued by last minute issues", that way it would match the patronizing tone used for other launchers.

"Debut of new Falcon"? Do you know it is second F9 v1.1?

[AJW]

The title of the article on the NSF page should be "Falcon 9 v1.1 aiming for Thanksgiving launch after three consecutive holds" , "Problematic start for the new Falcon" or "Debut of new Falcon plagued by last minute issues", that way it would match the patronizing tone used for other launchers.

NSF Article Source?

[Antares]

The title of the article on the NSF page should be "Falcon 9 v1.1 aiming for Thanksgiving launch after three consecutive holds" , "Problematic start for the new Falcon" or "Debut of new Falcon plagued by last minute issues", that way it would match the patronizing tone used for other launchers.

That's lame, dude.  NSF is pretty evenhanded toward everyone.  Please cite a patronizing tone for the other launchers that an NSF headline has used.

[DFSL]

NSF articles are excellent and generally unbiased, like the BBC. But just like the BBC, that impartiality suffers when pressed to discuss issues that obviously touch core preferences or values.
If I'm not mistaken, recent articles about the heavy Russian launcher included a gratuitous mention to the last failure, glitches were scrutinized even after successful launches on other rockets and so on. So why not mention the dangers of the F9 shortfalls? The unproved upper stage, the scrubs, etc. Mention those in the front page, like the rest.

[AS-503]

NSF articles are excellent and generally unbiased, like the BBC. But just like the BBC, that impartiality suffers when pressed to discuss issues that obviously touch core preferences or values.
If I'm not mistaken, recent articles about the heavy Russian launcher included a gratuitous mention to the last failure, glitches were scrutinized even after successful launches on other rockets and so on. So why not mention the dangers of the F9 shortfalls? The unproved upper stage, the scrubs, etc. Mention those in the front page, like the rest.

With Proton we are talking about a "Return to Flight" launch after a very dramatic failure. It goes without saying that with a scenario like that it changes the entire tone of the coverage. It seems bizarre to have to spell that out to you.

[AJW]

NSF articles are excellent and generally unbiased, like the BBC. But just like the BBC, that impartiality suffers when pressed to discuss issues that obviously touch core preferences or values.
If I'm not mistaken, recent articles about the heavy Russian launcher included a gratuitous mention to the last failure, glitches were scrutinized even after successful launches on other rockets and so on. So why not mention the dangers of the F9 shortfalls? The unproved upper stage, the scrubs, etc. Mention those in the front page, like the rest.

Why not read the NSF article about the scrub and you'll find these sentences:

"SpaceX will perform the launch of SES-8 using a Falcon 9 rocket. Founded by billionaire Elon Musk in March 2002, SpaceX developed the small Falcon 1 rocket which first flew unsuccessfully in 2006.  Following three consecutive launch failures the rocket made its first successful launch in September 2008."

 If there was bias towards SpaceX that you claim, these comments would not have been written.

Again, stop with the arm waving and cite specific examples as I have.

[Pete]

NSF articles are excellent and generally unbiased, like the BBC. But just like the BBC, that impartiality suffers when pressed to discuss issues that obviously touch core preferences or values.
If I'm not mistaken, recent articles about the heavy Russian launcher included a gratuitous mention to the last failure, glitches were scrutinized even after successful launches on other rockets and so on. So why not mention the dangers of the F9 shortfalls? The unproved upper stage, the scrubs, etc. Mention those in the front page, like the rest.

_{bold applied to quote, to highlight the statements/words i comment on}

You are mistaken.
NSF referring to the previous (and very spectacular!) launch failure of the Proton, when discussing the return-to launch of the same, is in no ways gratuitous.

For you to feel that a safe launch scrub & 3 day delay should be treated in the same way as a launch failure impacting into its pad, IS quite egregious.

I see no sign of the bias to which you refer, other than in your very own statements.

[Chris Bergin]

No, I don't want this modded, so I've returned the comments and I'll address this personally. It's very important we address both good and bad feedback

The title of the article on the NSF page should be "Falcon 9 v1.1 aiming for Thanksgiving launch after three consecutive holds" , "Problematic start for the new Falcon" or "Debut of new Falcon plagued by last minute issues"

Those titles don't work for several reasons.

1) We already had the scrub article on via the modification to William's article. A second article mentioning the event as the headline is wrong per the timing and angle. The readers need to know when the next attempt is, a status update so to speak. They knew there were three holds and a scrub the day before.

2) However, the article is mostly about explaining the holds that caused the eventual scrub, in detail, via a lot of work in L2.

3) Headlines and abstracts are restricted by length. They also need to be accurate (this wasn't the debut of the Falcon 9 v1.1 itself etc.)

that way it would match the patronizing tone used for other launchers.

I've never been patronizing about any launcher. I love all rockets. It's our "thing" here. We call them "shes" more times than any other site, because we give as much love towards them as would be expected for a site that is sometimes more interested in the rockets than the astronauts (per Shuttle days).

NSF articles are excellent and generally unbiased, like the BBC.

Woo! (And I hope you mean the BBC's space reporting. Jonathan Amos is amazing. The rest of the BBC can struggle with political alignments.....so they - as an organization - can struggle with that, but not the space news side. That's excellent.)

But just like the BBC, that impartiality suffers when pressed to discuss issues that obviously touch core preferences or values.

If anything, we're completely opposite of that. Some sites show bias against SLS. Some show bias towards Commercial Space. We like both....But I guess you're talking about Russian vehicles, per the next comment.

If I'm not mistaken, recent articles about the heavy Russian launcher included a gratuitous mention to the last failure, glitches were scrutinized even after successful launches on other rockets and so on.

One has to reference previous launches for each rocket. Proton had a dramatic failure and thus that is going to be referenced in articles covering the next missions. If you think we're having a go at Proton in some sort of anti Russian launcher bias, then you're very mistaken. I know there's a number of Russian friends on here who would immediately pull me up on that if I did. Again, we like all rockets here. Please look back to the live coverage of that Proton failure. No one was 'excited' or 'happy'. I was actually sick to my stomach watching her topple over like she did.

 So why not mention the dangers of the F9 shortfalls? The unproved upper stage, the scrubs, etc. Mention those in the front page, like the rest.

Again, the article you're complaining about was mostly about the holds. You're acting like you only read the headline. It was written explaining the technicalities behind it, as opposed to trying to find a negative "SpaceX sucks" angle, which I dare say you seem to be wishing for.

So who's the one with the bias?

[LouScheffer]

The title of the article on the NSF page should be "Falcon 9 v1.1 aiming for Thanksgiving launch after three consecutive holds" , "Problematic start for the new Falcon" or "Debut of new Falcon plagued by last minute issues", that way it would match the patronizing tone used for other launchers.

If anything, I think this is backwards.  "Dream Chaser ETA review promotes positives despite anomaly" could have been written "Dream Chaser ETA review has some positive points despite crash landing", if Chris wanted to be snarky.  What's the example you are thinking of?

[Kabloona]

It's strange how two people can read the same article and come to completely different conclusions about the author's intent, bias, or preference. As someone who has no particular ax to grind or favorite horse, I've found Chris' articles remarkably even-handed and fair when reporting both the successes and failures of any particular launcher, be it Proton, Falcon 9, or whatever.

Chris said upthread that "I love all rockets," (emphasis added) and that seems to me to be the truest statement of his journalistic bias, if it can be called such.

[beancounter]

It's strange how two people can read the same article and come to completely different conclusions about the author's intent, bias, or preference. As someone who has no particular ax to grind or favorite horse, I've found Chris' articles remarkably even-handed and fair when reporting both the successes and failures of any particular launcher, be it Proton, Falcon 9, or whatever.

Chris said upthread that "I love all rockets," (emphasis added) and that seems to me to be the truest statement of his journalistic bias, if it can be called such.

If anyone wants to see bias, I suggest you try some of the articles written by Jason Rhian at America Space although it does look like he's moved on to a new site SpaceFlightInsider.  In addition, although Chris will occasionally chastise contributors here, so far as I know, no one has ever been banned again unlike the aforementioned site. 

Points for NSF:
1.  NSF is particularly tolerant of all views. 
2.  NSF is the most comprehensive space site on the web that I've been able to find if you're prepared to fork out for L2 which I strongly recommend.
3.  NSF has fantastic contacts and that speaks volumes for it's editorial reputation.
4.  NSF has many expert posters who work in the industry and are happy to provide commentary and analyses of issues.

Hats off to NSF. 

Cheers,

[Roy_H]

I would like to know what drives the launch window of 66 minutes. Since the target orbit is GEO, it seems to me that the rocket and satellite have to go through the exact same maneuvers regardless of the time of day (or time of year for that matter). Should be able to launch anytime. Why do they have to wait until 5:37 pm?

To put the spacecraft near the desired orbital slot and there are solar/thermal considerations during the transfer orbits

Thought I'd try again. Jim's response pointing out the obvious environmental differences didn't help much as it still doesn't answer why. It did make me think of one possible reason, maybe the satellite can lock on to it's navigational stars easier if it is in earth's shadow. Right? Wrong? Anybody know why launching into the dark side of the earth is better than daylight?

[SBerger]

A major reason for launching a comsat such that the first nodal crossing (when the upper stage does its burn to GTO) is at 'local midnight' is to maximize the time that the transfer orbit is sunlit.  Most, if not all, of the GSO missions that we have launched on Atlas in the last 25 years wanted to get their solar panels deployed and providing power (i.e., in the sun) as soon as possible in order to minimize the time on battery power alone.  Jim could better explain how paranoid the spacecraft people are about battery conditioning (up to and including charging to the last possible second and keeping prelaunch battery temperatures as cold as possible).  The second consideration that Jim mentioned - timing the trajectory to minimize the amount of drifting required to reach the desired final position at GTO - is also important.