SpaceX Falcon 9 v1.1 - Thaicom 6 - DISCUSSION THREAD

[guckyfan]

We don't know what they were really aiming for. The press release is not a bible. For a Geo-Sat this is a good orbit. For an interplanetary probe it would be a bad orbit. Why would we assume they cannot fly a good orbit for an interplanetary probe, if needed?

To me the difference is too big to be explained as an error.

[edkyle99]

SpaceX press kit says the mass of Thaicom-6 was 3016 kg while Orbital says it was 3330 kg

I am quite confident to my memory that in SpaceX's Webcast Molly or someone else said that Thaicom-satellite weights 3300 kg. Also Wikipedia says that it weights 3325 kg. Therefore it is good to be critical on sources and that 3016 kg is probably just simple mistake. People often makes this kind of mistakes, because they are not accurate with numbers.

Throw the Wikipedia number out.  The press kit is supposed to be the right number, but isn't always.  It has long seemed to me that SpaceX fudges the numbers on purpose, to create uncertainty.  But it could be that the final propellant loading changed as mission planning proceeded.  In that case, the SpaceX press kit should be the most recent value.   

 - Ed Kyle

[Jim]

Thanks, so follow up question:
Which data points would it need?
@Jim: which did you had in mind?
Industry wide history of target vs actual? Or SpaceX's history only?
What to do with intentional better orbits then initial target?
I would expect SD and 3xsigma could only establish some estimate of what the industry is capable of, not what is considered a good or even bulls eye orbit...

Antares explained it, it is based on preflight analysis and not past missions or industry.

[Jakusb]

Thanks, so follow up question:
Which data points would it need?
@Jim: which did you had in mind?
Industry wide history of target vs actual? Or SpaceX's history only?
What to do with intentional better orbits then initial target?
I would expect SD and 3xsigma could only establish some estimate of what the industry is capable of, not what is considered a good or even bulls eye orbit...

Antares explained it, it is based on preflight analysis and not past missions or industry.

Ok, so they run countless simulation runs that produce data point from which to calculate SD for this specific flight?

[edkyle99]

Review of video seems to me to show a roughly 350 second long stage 2 burn, which is about 15 seconds longer than the time listed in the press kit and the post launch press release.  Another puzzle.

 - Ed Kyle

Ed, in the update thread you stated that the first stage burned only 177s. Isn't that three seconds less than normal, the ses launch? That could explain the discrepancy.

Actually 177 seconds is three seconds longer than the first stage burn time listed in the SpaceX Thaicom 6 press kit.  As someone else wrote about the press kit - "it isn't a Bible".

 - Ed Kyle

[input~2]

...  But it could be that the final propellant loading changed as mission planning proceeded.  In that case, the SpaceX press kit should be the most recent value.   

 - Ed Kyle

FWIW, the SpaceX press kit was uploaded on January 5 at 9:05 am EST

[TrueBlueWitt]

Review of video seems to me to show a roughly 350 second long stage 2 burn, which is about 15 seconds longer than the time listed in the press kit and the post launch press release.  Another puzzle.

 - Ed Kyle

Review of video seems to me to show a roughly 350 second long stage 2 burn, which is about 15 seconds longer than the time listed in the press kit and the post launch press release.  Another puzzle.

 - Ed Kyle

Ed, in the update thread you stated that the first stage burned only 177s. Isn't that three seconds less than normal, the ses launch? That could explain the discrepancy.

Actually 177 seconds is three seconds longer than the first stage burn time listed in the SpaceX Thaicom 6 press kit.  As someone else wrote about the press kit - "it isn't a Bible".

 - Ed Kyle

It also send to

Ed, in the update thread you stated that the first stage burned only 177s. Isn't that three seconds less than normal, the ses launch? That could explain the discrepancy.

Actually 177 seconds is three seconds longer than the first stage burn time listed in the SpaceX Thaicom 6 press kit.  As someone else wrote about the press kit - "it isn't a Bible".

 - Ed Kyle

Although didn't it also seem to stay on the pad for an extra second or two?

[Arthree]

Review of video seems to me to show a roughly 350 second long stage 2 burn, which is about 15 seconds longer than the time listed in the press kit and the post launch press release.  Another puzzle.

 - Ed Kyle

Review of video seems to me to show a roughly 350 second long stage 2 burn, which is about 15 seconds longer than the time listed in the press kit and the post launch press release.  Another puzzle.

 - Ed Kyle

Ed, in the update thread you stated that the first stage burned only 177s. Isn't that three seconds less than normal, the ses launch? That could explain the discrepancy.

Actually 177 seconds is three seconds longer than the first stage burn time listed in the SpaceX Thaicom 6 press kit.  As someone else wrote about the press kit - "it isn't a Bible".

 - Ed Kyle

It also send to

Ed, in the update thread you stated that the first stage burned only 177s. Isn't that three seconds less than normal, the ses launch? That could explain the discrepancy.

Actually 177 seconds is three seconds longer than the first stage burn time listed in the SpaceX Thaicom 6 press kit.  As someone else wrote about the press kit - "it isn't a Bible".

 - Ed Kyle

Although didn't it also seem to stay on the pad for an extra second or two?

Yes, there was a 3-second delay on the video.  MECO happened at 2:57 on the on-screen clock, or 2:54 (174s) with the 3-second delay.

[Lars_J]

Fix yer' quotes, people!

[ugordan]

No matter how much I seem to rant about it, it seems some people still don't seem to get it that SpaceX webcasts are not in sync with just about anything else and take the events as happening on screen at face value. The fact is the on-screen clock is not in good sync with the audio which is not in sync with video which is not in sync with video from *another source*. This leads to discussions about pad aborts at T+2 seconds, vehicle lifting off not at T-0 but later, etc. They are an artifact of the sync problem. Check these videos out for an example of video with an audio source that is *not* significantly delayed - my guess a conventional radio transmission from the range center or something:
www.youtube.com/watch?v=6-_vdpY9n-M
www.youtube.com/watch?v=DfSsnpjZbys

I, too, was fooled into thinking there was an abort with Thaicom 6 when the view switched from a closeup of the engines to the wide pad shot that seemed to show no liftoff at first (looked like a shutdown actually!) since that wide shot historically seemed to be *ahead* of other pad views, not behind. It does go to show that you should not trust anything you see on screen, especially if you time one event from one video source and another event from another.

[WmThomas]

Was the Thaicom 6 F9 held down for a longer time than on previous flights?

If the apparent delay in the video feed was illusory, they would have had to have been editing the live feeds with recorded material at launch time. I doubt they did this as part of the webcast.

If it was held down longer, did the extra water on the launcher have anything to do with plans for a longer hold-down than they had used in the past?

[ugordan]

If the apparent delay in the video feed was illusory, they would have had to have been editing the live feeds with recorded material at launch time.

I don't know why you would come to that conclusion. It is easy to conceive of a situation where all the feeds are digital so inevitably buffered to some extent (either for compression or transmission via different paths), but are not buffered by the same amount and, without timestamps, there's no easy way of synchronizing them properly. This is what I believe is happening. It's not their intention to do that. I would wager to say it's a big nuisance to them instead.

[Prober]

From the Spacex press release:
Falcon 9 delivered THAICOM 6 to its targeted 295 x 90,000 km geosynchronous transfer orbit at 22.5 degrees inclination.

From the update thread:
...catalogued by USSTRATCOM.
Object A: 2014-002A/39500 at 0051UTC was in 376 x 90039 km x 22.46° (tentatively Thaicom-6)

Looks pretty darn close to me, but what do I know Given that nothing is ever exact, what are the industry standards for "close enough" and "bulls eye" and what if anything are the implications for the spacecraft of these specific (tentative) variations from nominal? Good, bad, or indifferent?

If they are within 3 sigma, then no issues.  If it is pushing 3 sigma, Spacex may look at things to see where the errors added up.

english please!?
#notarocketscientist

http://en.wikipedia.org/wiki/Standard_deviation

oh Jim your getting sloppy using that site as a source.

[Robotbeat]

It's not a source, it's a summary.

[edkyle99]

No matter how much I seem to rant about it, it seems some people still don't seem to get it that SpaceX webcasts are not in sync with just about anything else ....

Yes, but the second stage video that shows the entire second stage burn shows these events from the same camera with presumably the same delay and therefore should be possible to be timed.  In both of the two most recent flights it shows longer burn times than predicted in the press kits.  About 15 seconds longer in both cases.  Unless 15 seconds of additional delay is added during the burns.

 - Ed Kyle

[ugordan]

Yes, but the second stage video that shows the entire second stage burn shows these events from the same camera with presumably the same delay and therefore should be possible to be timed.

Theoretically, yes, although I would use the hard-coded timestamp difference instead of timing it off the webcast since there are many data dropouts and bufferings.

The first stage burn duration, though... anybody's guess. I usually trust amateur videos from the ground more than the webcast, but the clouds intervened in this case.

[StephenB]

The latest Orbital press release does mention SpaceX.

[kevin-rf]

The latest Orbital press release does mention SpaceX.

I thought it always did, the omission was Orbital's name in the SpaceX press release.

Anyway's congratulations to both of them working together on a job well done.

[sdsds]

I've been burned recently while trying to interpret catalog data, but like a stubborn child I'll reach towards the stove again here:

2 Objects have now been catalogued by USSTRATCOM.
Object A: 2014-002A/39500 at 0051UTC was in 376 x 90039 km x 22.46° (tentatively Thaicom-6)
Object B: 2014-002B/39501 at 2336UTC was in 457 x 91590 km x 22.39°

My spreadsheet shows the Object A orbit is better for the spacecraft (closer to GEO) than the target orbit, though only by 4 m/s.

Also it shows the minimum delta-v between the Object A orbit and the Object B orbit as 288 m/s. Can that be achieved purely with venting?

(On the topic of standard deviation: I think something like https://en.wikipedia.org/wiki/Monte_Carlo_method is implicit.)

[Lars_J]

Also it shows the minimum delta-v between the Object A orbit and the Object B orbit as 288 m/s. Can that be achieved purely with venting?

It is possible that a initial small separation burn was already done by the satellite.