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

[fatjohn1408]

What's the perigee? Should be able to figure out when it'll eventually come down.

Per press kit, target orbit was 295km x 80,000km at 20.75 degrees.

Target, any idea how close they got?

[sittingduck]

The rear-view image of the Earth that Musk tweeted was at a distance of ~12000km, only 1/5 of the way to  apogee.  Does it take roughly 12h to make it to apogee?  How long does the S2 battery last?  From how far out will it have been able to return an image?

[ugordan]

Does it take roughly 12h to make it to apogee?

There is a very large difference in orbital speed at perigee and apogee for such an elliptic orbit. Speed quickly drops off going uphill so, yes, it takes many hours. The batteries will most likely be dead by then.

[ugordan]

For some reason the tracking cameras were all over the place this time... I wonder why.

I think SpaceX might have cropped the tracker frame (higher resolution view of the rocket in the left video pane that way) so the vehicle would appear to go out of FOV even though it might not have went out of the entire original frame to the person actually tracking the camera.

[ChrisWilson68]

What's the perigee? Should be able to figure out when it'll eventually come down.

Per press kit, target orbit was 295km x 80,000km at 20.75 degrees.

Target, any idea how close they got?

CelesTrack is showing something labeled "Object A" with a launch date of 12/3/2013 from Florida.  It has international designator 2013-071A and NORAD catalog number 39460.

The TLE for this object is:

1 39460U 13071A   13337.40768818 -.00000413  00000-0  00000+0 0    37
2 39460  20.5531 242.7832 8534855 179.4250 185.5374  0.87290738    01

So it looks like 397 km by 79341 km at 20.55 degrees.

[QuantumG]

CelesTrack is showing something labeled "Object A" with a launch date of 12/3/2013 from Florida.  It has international designator 2013-071A and NORAD catalog number 39460.

The TLE for this object is:

1 39460U 13071A   13337.40768818 -.00000413  00000-0  00000+0 0    37
2 39460  20.5531 242.7832 8534855 179.4250 185.5374  0.87290738    01

So it looks like 397 km by 79341 km at 20.55 degrees.

Neat. Decay is estimated to be on 25 Mar 2014.. after 174 orbits. The lifetime is 112 days.

Using the same (wrong) guesses as before for drag.

[jeff.findley]

Congrats to SpaceX!  The big achievement here isn't so much a "first" in anything, other than the low cost to the customer.  This success ought to boost SpaceX's sales of Falcon 9 launches.  Right now, no other launch provider on the planet can compete with them in terms of launch costs.

[Jim]

That is not known

[fatjohn1408]

CelesTrack is showing something labeled "Object A" with a launch date of 12/3/2013 from Florida.  It has international designator 2013-071A and NORAD catalog number 39460.

The TLE for this object is:

1 39460U 13071A   13337.40768818 -.00000413  00000-0  00000+0 0    37
2 39460  20.5531 242.7832 8534855 179.4250 185.5374  0.87290738    01

So it looks like 397 km by 79341 km at 20.55 degrees.

It's fairly off from their "intended" orbit. Should we assume they missed it or that they did not want to publicize the exact orbit for anyone to know for some reason?

[AnjaZoe]

You have to differentiate between cost and price. I am pretty sure that the actual launch costs are not the same as the launch price advertised on their web site. I might even go out on a limb and assume that the actually paid sum for a launch is not the same as the value given at the web site 

Zoe

[dante2308]

CelesTrack is showing something labeled "Object A" with a launch date of 12/3/2013 from Florida.  It has international designator 2013-071A and NORAD catalog number 39460.

The TLE for this object is:

1 39460U 13071A   13337.40768818 -.00000413  00000-0  00000+0 0    37
2 39460  20.5531 242.7832 8534855 179.4250 185.5374  0.87290738    01

So it looks like 397 km by 79341 km at 20.55 degrees.

It's fairly off from their "intended" orbit. Should we assume they missed it or that they did not want to publicize the exact orbit for anyone to know for some reason?

This orbit is fairly better for the client than the target orbit.

[bjornl]

So, was the final burn a "burn to depletion", intended to get the best possible orbit for their customer, and did they just underestimate the performance?

[ugordan]

CelesTrack is showing something labeled "Object A" with a launch date of 12/3/2013 from Florida.  It has international designator 2013-071A and NORAD catalog number 39460.

The TLE for this object is:

1 39460U 13071A   13337.40768818 -.00000413  00000-0  00000+0 0    37
2 39460  20.5531 242.7832 8534855 179.4250 185.5374  0.87290738    01

So it looks like 397 km by 79341 km at 20.55 degrees.

It's fairly off from their "intended" orbit. Should we assume they missed it or that they did not want to publicize the exact orbit for anyone to know for some reason?

Do we even know if that's SES-8 or the 2nd stage after propellant venting?

[Antares]

That could easily be debris after a CCAM, so it's imprecise speculation to wonder if something is amiss.

[Mike_1179]

If orbital energy is inversely proportional to the semi-major axis of the ellipse (really getting into the way-back machine for my brain here), you need to see how different the semi-major axes are between the planned and actual orbit.

The planned orbit has a semi-major axis of 39869 km, actual is 40148 km.  The actual orbit has a semi-major axis that is 0.7% larger than plan.   The inclination is close to the planned as well – the satellite needs to get to an inclination of 0 anyway, and it’s not terribly expensive to do these plane changes at larger perigees.

Sticker shock from “They missed the target by over 100 km!” doesn’t mean as much here.  What really matters is what they told the customer so how much fuel will the satellite have left after maneuvering to where it needs to go.  If they are within that range, then they met the customer requirements. 

[dante2308]

If orbital energy is inversely proportional to the semi-major axis of the ellipse (really getting into the way-back machine for my brain here), you need to see how different the semi-major axes are between the planned and actual orbit.

The planned orbit has a semi-major axis of 39869 km, actual is 40148 km.  The actual orbit has a semi-major axis that is 0.7% larger than plan.   The inclination is close to the planned as well – the satellite needs to get to an inclination of 0 anyway, and it’s not terribly expensive to do these plane changes at larger perigees.

Sticker shock from “They missed the target by over 100 km!” doesn’t mean as much here.  What really matters is what they told the customer so how much fuel will the satellite have left after maneuvering to where it needs to go.  If they are within that range, then they met the customer requirements.

Just to clarify, zero energy is escape and the energy you're talking about is negative meaning that the longer the semi-major axis, the higher the energy (of course) {E = -mu/(2*a)}.

A

So, was the final burn a "burn to depletion", intended to get the best possible orbit for their customer, and did they just underestimate the performance?

You can't raise the perigee at perigee. The 100km discrepancy happened during the initial burn of the second stage.

[kevin-rf]

It's also an initial TLE with limited tracking data. We do not know how noisy the tracking data that created it is. It might have very wide error bars.

It will be interesting to look at the TLE's after they have some history tracking the device.

[jabe]

AIUI  They waited for 2nd stage relight so the perigee happens when the satellite is at the equator.  Then when the satellite gets to apogee, it has a very low velocity so an equatorial plane change is easier.  Then I am guessing they will raise the perigee first  to GEO altitude and then lower the apogee to GEO.
jb

[kevin-rf]

CelesTrack is showing something labeled "Object A" with a launch date of 12/3/2013 from Florida.  It has international designator 2013-071A and NORAD catalog number 39460.

The TLE for this object is:

1 39460U 13071A   13337.40768818 -.00000413  00000-0  00000+0 0    37
2 39460  20.5531 242.7832 8534855 179.4250 185.5374  0.87290738    01

So it looks like 397 km by 79341 km at 20.55 degrees.

What is the source of that TLE? IT exactly matches the current TLE on the space-track.org site and I thought rules existed about publishing space-track.org TLE's.

[dante2308]

AIUI  They waited for 2nd stage relight so the perigee happens when the satellite is at the equator.  Then when the satellite gets to apogee, it has a very low velocity so an equatorial plane change is easier.  Then I am guessing they will raise the perigee first  to GEO altitude and then lower the apogee to GEO.
jb

Yeah. I think that was most of the point of the high apogee.