Author Topic: Does anybody know why Soyuz from Kourou was chosen for Galileo?  (Read 4922 times)

Offline pippin

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I'm just wondering, maybe somebody has some background on this.

Is this mainly to have demonstration flights for Soyuz out of Kourou or is it to have more options? Or more capacity? Or because they don't want to deliver the Galileo sats to Kazakhstan (ITAR-like)?
From what you officially hear out of Arianespace, cost wise it's a draw (4 sats on Ariane 5 cost twice as much as 2 on Soyuz) and I thought (might be wrong) that they do plan some Galileo flights on Ariane 5, too.

The low inclination doesn't help with Galileo, actually it's probably even a slight penalty so you could launch out of Baikonur as well.

Offline Ben the Space Brit

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(Transplanted from Soyus launch live thread)

I'm no expert but I think it's because Soyuz's payload range is more optimal for the launch of Galileo than Ariane-5.  There are probably cost issues too as Soyuz is kerolox and ground ops are likely cheaper than the hydolox/solid Ariane.
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Offline pippin

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But the prices communicated (don't remember the figures exactly, have to dig that out) were roughly a draw. 4 sats on A5 cost twice as much as two sats on Soyuz.
That's per launch so should include ground ops.
Actually ground ops could of course be an argument against Baikonour if they have special stuff that they only have to set up once in Kourou now.

Offline Alpha_Centauri

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I sincerely doubt a Soyuz launch (even from Kourou) costs as much as half an Ariane 5. The latest figures I can find, which admittedly come from a few years ago, was that it would cost ~$50million.
« Last Edit: 10/20/2011 12:37 PM by Alpha_Centauri »

Offline baldusi

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Well, for starts, this are validation vehicles. I guess they want to make sure they work. Second, if I'm not mistaken, the second pair (the ones to launch on an 2-1A) will go to a different orbital plane. So you couldn't put four of them on an Ariane 5. You could do only that if you were populating a whole orbital plane.
Regarding the efficiency. For anything less than 80 degrees or so, Kourou will give you better performance. Simply do the vector sum of delta-v needed, and as long as the longitudinal component of delta-v needed is less than the rotational speed at Kourou (i.e. very close to polar), you will gain some performance from there. That's why Alcantara is the best launch place until you hit 87degrees. It's obvious that the gains of a few percent, but you still came ahead.

Offline pippin

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Hm. Antonio Elias has a different opinion on that and I would have thought that he should know...
http://forum.nasaspaceflight.com/index.php?topic=11939.msg248915#msg248915

I believe the misunderstanding is that part of the rotational energy just goes into the rotation of the orbital plane and doesn't contibute to the delta-v needed to reach orbital velocity.

The two-sats-per-plane explanation makes a lot of sense, though.
« Last Edit: 10/20/2011 01:30 PM by pippin »

Offline Nicolas PILLET

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Is this mainly to have demonstration flights for Soyuz out of Kourou

Soyouz is not launched from Kourou, but from Sinnamary...
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Offline baldusi

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There was a posterior discussion about the Soyuz from Kourou to the ISS where, I think Danderman, proved that it was more efficient. I think that statement from Dr Elias was calculated on a fixed frame of reference, when it should have been done a rotational one. Even Jim admitted that it had better performance.

Offline SIM city

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I think the answer is much more simply cost.  The marginal flight cost for an Ariane 5 with 4 s/c was more than twice that of a Soyuz launch of 2 s/c, and doesn't include the 70-100M euros in mods needed on the Ariane 5 ES. 

Offline pippin

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So I see that there don't seem to be any Galileo sats left on the Ariane manifest, right?

Found a statement by Le Gall stating that the launch cost per kg would be similar for Ariane 5 and Soyuz with Ariane having three times the payload (which of course could be just their pricing structure; and yes, if you look at their numbers at least the payload figures for GTO are about that). This would of course mean that Soyuz is indeed cheaper if it launches half as many sats at a time...

Offline ChileVerde

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Is this mainly to have demonstration flights for Soyuz out of Kourou

Soyouz is not launched from Kourou, but from Sinnamary...

A quick search indicates that the pad is in the vicinity of 5.297 N, 52.838 W, but the Google Earth picture of the area is too old to confirm that.  I'll see if the location can be confirmed on DigitalGlobe or GeoEye browse imagery.

Add: Pretty close. The Arianespace Soyuz users manual of June 2006 says  5d 18m 18s N, 52d 50m 04s  W, which is 5.3050 N, 52.8344 W in decimalspeak.
« Last Edit: 10/20/2011 03:55 PM by ChileVerde »
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Offline asdert

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Is this mainly to have demonstration flights for Soyuz out of Kourou

Soyouz is not launched from Kourou, but from Sinnamary...

A quick search indicates that the pad is in the vicinity of 5.297 N, 52.838 W, but the Google Earth picture of the area is too old to confirm that.  I'll see if the location can be confirmed on DigitalGlobe or GeoEye browse imagery.

Add: Pretty close. The Arianespace Soyuz users manual of June 2006 says  5d 18m 18s N, 52d 50m 04s  W, which is 5.3050 N, 52.8344 W in decimalspeak.

Another quick search shows what CNES says in http://www.cnes-csg.fr/web/CNES-CSG-en/4690-the-soyuz-launch-complex.php:

Quote
The launch site was to be located in the north-west part of the European Space Port. This 120 hectare zone falls under the administrative authority of the city of Sinnamary.

Tags: Ariane  Soyuz  Galileo