Author Topic: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread  (Read 33893 times)

Online Chris Bergin

As part of our increasing coverage to cover more on the spacecraft - as opposed to mainly the rockets - here's a dedicated thread for the SES-8 satellite, by Orbital.

I've written an article based on the confirmation of its shipping, with as much details on the bird as I could muster:

SES-8 heads to Florida for next Falcon 9 v1.1 launch
http://www.nasaspaceflight.com/2013/10/ses-8-florida-next-falcon-9-v1-1-launch/

So this thread can cover discussion on this spacecraft. Anything on the launch vehicle can be covered in the relevant SpaceX threads.
« Last Edit: 10/02/2013 10:42 PM by Chris Bergin »

Offline StarryKnight

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Thanks for starting this, Chris. I'm a spacecraft kind of guy, not so much a rocket man. So I appreciate a thread like this.
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Offline dsobin

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Great thread Chris! I'd like to see more like this.

We heard Elon say that the SpaceX contract with SES requires full expendable-style performance. Does this mean
that SES will be able to load more prop into its tanks? If some performance had been reserved for booster stage re-lights, would the SES-8 tanks have been only partly full? What would this do to spacecraft lifetime?

What other considerations go into this requirement as a contract consideration, as opposed to a technical necessity?


Offline Joffan

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Orbital's fact sheet

Quote
SES-8, a hybrid Ku- and Ka-band spacecraft, is the sixth GEOStar-2™ satellite ordered by SES S.A. The satellite is based on Orbital’s Enhanced GEOStar-2 bus, and will carry 24 active Ku-band transponders of 36 or 54 Mhz capacity switchable amongst 33 channels and two beams. Certain channels in each beam are cross-strapped to multiple frequency bands, enabling flexibility for new services. In addition, the spacecraft features a Ka-band payload. The spacecraft will generate approximately five kilowatts of payload power and will feature two 2.5 x 2.7 meter super elliptical deployable reflectors and a 1.45 meter fixed, deck-mounted antenna.
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Offline kevin-rf

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Looking at the satellite simulated image, one thing just bugs the heck out of me (and everyone manufacture seems to do it).

In flight the solar panels looking from the ground are located above and below (north and south) of the satellite body and orbital plane, the two dishes are located to the left and right (east and west) of the satellite body and orbital plane.

They (like everyone else) are depicting the satellite on it's side!

End mini rant... Sorry Chris, I'll go get some coffee now.
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Online pippin

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For Ariane dual launches, will we then have a dedicated spacecraft thread for both sats or one combined for both in the future?
There's one of these Orbital StarBus babies on almost every Ariane 5 launch since they are the typical "secondary" candidate due to their small size and weight (they fit into Sylda).

Offline Lurker Steve

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Interesting that this is the "smaller" of the GEOstar family, although that does seem to be a fairly decent number of transponders on this comm stat.

What is the mix of GEOstar sats launched to date ? How many GEOstar-2 vs GEOstar-3 for instance ?

I wonder if the GEOstar-3 is too heavy for a F9.

Offline parham55

Looking at the satellite simulated image, one thing just bugs the heck out of me (and everyone manufacture seems to do it).

In flight the solar panels looking from the ground are located above and below (north and south) of the satellite body and orbital plane, the two dishes are located to the left and right (east and west) of the satellite body and orbital plane.

They (like everyone else) are depicting the satellite on it's side!

End mini rant... Sorry Chris, I'll go get some coffee now.

Now for a very basic spacecraft question, why are the spacecraft oriented this way in flight and not the other? Thanks.

Offline kevin-rf

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It has to do with the sun and the solar panels. The panels rotate about the satellite body from east to west (Clockwise?) to track the sun. To do this the axis of rotation has to be north to south, leaving the east, west (right,left) sides of the satellite available for large antenna.
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Offline StarryKnight

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Lot's of good questions so far. I'll do my best to answer them as many as I can.

We heard Elon say that the SpaceX contract with SES requires full expendable-style performance. Does this mean
that SES will be able to load more prop into its tanks? If some performance had been reserved for booster stage re-lights, would the SES-8 tanks have been only partly full? What would this do to spacecraft lifetime?

What other considerations go into this requirement as a contract consideration, as opposed to a technical necessity?

The injection orbit for SES-8 is called a super-synchronous GTO (GTO = Geosynchronous Transfer Orbit) which means that the apogee is above the GEO synchronous altitude of 35,786 km. (A satellite in a circular orbit at GEO altitude has an orbit period of 1 day, matching the Earth's rotation rate). A typical GTO (like you get off of Ariane, Land Launch, Sea Launch, and some other launchers) is an ellipse that has apogee at or near GEO altitude and perigee altitude of somewhers between a couple of hundred kilometers to a few thousand kilometers. It is then up to the satellite to use onboard thrusting to raise perigee up to GEO.

The super-synch GTO also has a fairly low perigee, but it's apogee is usually 10's of kilometers above GEO. This means the satellite's orbit has higher energy. So even though you have to now both raise perigee to GEO and lower apogee to GEO, there is still a fuel savings. For the SES-8 mission, most of the Falcon 9's performance will go into putting the spacecraft in an orbit over 80,000 km altitude at apogee. Some of the rocket's performance will also lower the orbit inclination from about 28 degrees (the lattitude of Cape Canaveral) to a little under 21 degrees, also reducing the amount of fuel that the satellite will require to get to its final orbital slot.

The SES-8 satellite's propellant tanks will be loaded as full as possible for the Falcon 9 to acheive the desired injection orbit. Again, since this is a high energy orbit, less proplellant will be required in the satellite than for a typical GTO to get the satellite to the desired orbit.


Kevin-rf - Yeah those drawings always bug me, too. The Earth is also always too big for a satellite being at GEO altitude. All I can say is artistic license does not reflect physical reality. (maybe I should add that saying to my signature  :) ).  However there are some satellites (e.g. Loral's FS-1300) which do deploy solar arrays very soon after launch and remain like that throughout the orbit raising period. But I don't know if the reflectors are deployed at that time or if they wait until the satellite gets to GEO.


LurkerSteve - 27 STAR-2's and no STAR-3's, yet. The STAR-3 will be fine on an F9. But the injection orbit won't be as high as the SES-8 or Thaicom-6 missions. It still may be able to reach super-synch, just not as high as 80,000+ km.
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Offline Star One

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #10 on: 10/03/2013 03:05 PM »

Lot's of good questions so far. I'll do my best to answer them as many as I can.

We heard Elon say that the SpaceX contract with SES requires full expendable-style performance. Does this mean
that SES will be able to load more prop into its tanks? If some performance had been reserved for booster stage re-lights, would the SES-8 tanks have been only partly full? What would this do to spacecraft lifetime?

What other considerations go into this requirement as a contract consideration, as opposed to a technical necessity?

The injection orbit for SES-8 is called a super-synchronous GTO (GTO = Geosynchronous Transfer Orbit) which means that the apogee is above the GEO synchronous altitude of 35,786 km. (A satellite in a circular orbit at GEO altitude has an orbit period of 1 day, matching the Earth's rotation rate). A typical GTO (like you get off of Ariane, Land Launch, Sea Launch, and some other launchers) is an ellipse that has apogee at or near GEO altitude and perigee altitude of somewhers between a couple of hundred kilometers to a few thousand kilometers. It is then up to the satellite to use onboard thrusting to raise perigee up to GEO.

The super-synch GTO also has a fairly low perigee, but it's apogee is usually 10's of kilometers above GEO. This means the satellite's orbit has higher energy. So even though you have to now both raise perigee to GEO and lower apogee to GEO, there is still a fuel savings. For the SES-8 mission, most of the Falcon 9's performance will go into putting the spacecraft in an orbit over 80,000 km altitude at apogee. Some of the rocket's performance will also lower the orbit inclination from about 28 degrees (the lattitude of Cape Canaveral) to a little under 21 degrees, also reducing the amount of fuel that the satellite will require to get to its final orbital slot.

The SES-8 satellite's propellant tanks will be loaded as full as possible for the Falcon 9 to acheive the desired injection orbit. Again, since this is a high energy orbit, less proplellant will be required in the satellite than for a typical GTO to get the satellite to the desired orbit.


Kevin-rf - Yeah those drawings always bug me, too. The Earth is also always too big for a satellite being at GEO altitude. All I can say is artistic license does not reflect physical reality. (maybe I should add that saying to my signature  :) ).  However there are some satellites (e.g. Loral's FS-1300) which do deploy solar arrays very soon after launch and remain like that throughout the orbit raising period. But I don't know if the reflectors are deployed at that time or if they wait until the satellite gets to GEO.


LurkerSteve - 27 STAR-2's and no STAR-3's, yet. The STAR-3 will be fine on an F9. But the injection orbit won't be as high as the SES-8 or Thaicom-6 missions. It still may be able to reach super-synch, just not as high as 80,000+ km.

How big would the Earth look if you were an astronaut perched on top of a GEO satellite & looked down?

Offline smoliarm

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #11 on: 10/03/2013 03:16 PM »
Looking at the satellite simulated image, one thing just bugs the heck out of me (and everyone manufacture seems to do it).

In flight the solar panels looking from the ground are located above and below (north and south) of the satellite body and orbital plane, the two dishes are located to the left and right (east and west) of the satellite body and orbital plane.

They (like everyone else) are depicting the satellite on it's side!

End mini rant... Sorry Chris, I'll go get some coffee now.

Kevin,
note that -- if you look at GEO satellite from some point at equator and 90° off (to West or East) from satellite's longitude -- you see it in this very orientation: solar panels are horizontal (left and right) and dishes are vertical (top and bottom). So, they just showed the view from some equatorial paradise ;)

Offline StarryKnight

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #12 on: 10/03/2013 03:22 PM »
Star One,

The Earth as seen from GEO is approximately 17 degrees in diameter.
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Offline kevin-rf

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #13 on: 10/03/2013 03:36 PM »
Kevin,
note that -- if you look at GEO satellite from some point at equator and 90° off (to West or East) from satellite's longitude -- you see it in this very orientation: solar panels are horizontal (left and right) and dishes are vertical (top and bottom). So, they just showed the view from some equatorial paradise ;)

Aaah, so the satellite art work is for business execs. pontificating from tropical paradises while the rest of us slave away in the cubical mines of the northern rust belts. Now it all makes sense ;)
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Offline smoliarm

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #14 on: 10/03/2013 03:36 PM »

...
How big would the Earth look if you were an astronaut perched on top of a GEO satellite & looked down?

Yes :) I got the same number :) 17°
And it's pretty damn big, e.g. angular size of the Moon from Earth is about 0.5 deg
or some 30+ times smaller.

Offline smoliarm

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #15 on: 10/03/2013 03:49 PM »
Kevin,
note that -- if you look at GEO satellite from some point at equator and 90° off (to West or East) from satellite's longitude -- you see it in this very orientation: solar panels are horizontal (left and right) and dishes are vertical (top and bottom). So, they just showed the view from some equatorial paradise ;)

Aaah, so the satellite art work is for business execs. pontificating from tropical paradises while the rest of us slave away in the cubical mines of the northern rust belts. Now it all makes sense ;)

Of course it makes sense - "must be funny in a rich man's world!!"
It's always sunny there too, unlike in the cubical mines ...

Offline kwan3217

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #16 on: 10/03/2013 05:59 PM »
It says in the news article that the spacecraft will be parked in an undisclosed location in Florida until the shutdown lifts, because Astrotech is unavailable. Why is that? I thought Astrotech was a private company with it's facilities off-base.

Offline Antares

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #17 on: 10/03/2013 09:07 PM »
Astrotech already has its processing bays booked?
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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #18 on: 10/03/2013 09:32 PM »
Article says
Quote
... the immediate post-flight discussions revolved around the potential to tweak the second stage, following an anomaly relating to a secondary task to attempt a re-entry, per SpaceX’s reusability ambitions.

I didn't think the 2nd stage anomaly had anything to do with any secondary task for it to attempt re-entry - I thought stage ONE was the only one trying to do re-entry, and stage TWO had a secondary task to burn-to-depletion - thus all the discussion about whether it could make it to Mars or not...

Did I miss something?

Offline Jim

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Re: SES-8 - for launch on F9 v1.1 - Dedicated Spacecraft Thread
« Reply #19 on: 10/04/2013 12:04 AM »
It says in the news article that the spacecraft will be parked in an undisclosed location in Florida until the shutdown lifts, because Astrotech is unavailable. Why is that? I thought Astrotech was a private company with it's facilities off-base.

I thought it was going to Spacex facilities and with KSC shutdown access is only via the south gate which might not be able to take the transporter.

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