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

[Robotbeat]

Inclination changes are cheap at high altitudes. 27 degrees is fine.

[sdsds]

Inclination changes are cheap at high altitudes. 27 degrees is fine.

I'm not certain how to do the math to quantify "cheap" in this context. StarryKnight wrote that F9 would leave SES-8 in an orbit inclined at "a little under 21 degrees." If the orbit were 250x80000 km the apogee velocity would be 811 m/s. Assuming that's at the equator, is the required delta-v to get to 0 degrees the orbital velocity times twice the sine of half the angle?

811 * 0.3645 = 295.6 m/s?

Plus the Hohmann transfer costs to raise perigee and lower apogee....

[Jim]

Would it be possible to inject the satellite into the super-synchronous transfer orbit with just one burn of the second stage?

there are RAAN considerations and that is another reason for the two burns

[Galactic Penguin SST]

Would it be possible to inject the satellite into the super-synchronous transfer orbit with just one burn of the second stage?

there are RAAN considerations and that is another reason for the two burns

Wasn't it the argument of perigee instead (for orienting the apogee of the orbit at the ascending or descending node for best performance for plane changes)? RAAN is instead vital for ISS/rendezvous launches (as it specifies the position of one satellite's orbital plane).

[Jim]

RAAN is instead vital for ISS/rendezvous launches (as it specifies the position of one satellite's orbital plane).

It is applicable for GTO missions too, so that the spacecraft is inserted close to its final position, to minimize the need to drift.

[mlindner]

Will be toughest mission to date. Requires coast + upper stage restart + going to 80,000 km altitude (~1/4 way to moon).

Looks like the apogee is going to be 80,000 km. I'd known that SES-8 was being sent to a super-GTO orbit, but was the apogee known before this?

http://forum.nasaspaceflight.com/index.php?topic=32990.msg1105331#msg1105331

"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."

So I've been wondering about this. Is the process: Launch --> coast to equator --> flatten orbital inclination while going to 80km elliptical --> payload release --> spacecraft completes 2nd half of bielliptic transfer by moving perigee to GEO altitude --> circularizes at GEO?

[mlindner]

Inclination changes are cheap at high altitudes. 27 degrees is fine.

Not possible. If you go to GTO in one engine run you end up with a highly elliptical orbit with the appogee at roughly the negative of the starting inclination. You can't change inclination to 0 from apogee.

[ChefPat]

How many restarts will SES-8 do?

[smoliarm]

How many restarts will SES-8 do?

just one

[deltaV]

Inclination changes are cheap at high altitudes. 27 degrees is fine.

Not possible. If you go to GTO in one engine run you end up with a highly elliptical orbit with the appogee at roughly the negative of the starting inclination. You can't change inclination to 0 from apogee.

That's true if perigee is near the launch site (which occurs if burnout velocity has little or no vertical component) but not in general. An extreme example is a "GTO" launching straight up, where (ignoring rotation of the Earth) apogee occurs above the launch site. Pick the appropriate initial velocity somewhere between straight up and straight sideways and you get apogee in the equatorial plane.

(IANARS but I'm pretty sure this is right.)

Edit: SES's orbit and alternatives are discussed in the SES spacecraft thread (Orbital section of forum).

[WHAP]

How many restarts will SES-8 do?

just one

What's the smiley for?  Don't spacecraft typically perform multiple burns to get from GTO to GSO?  More so if they need to lower apogee?  It it true that SES-8 will only burn twice (one burn, one restart  ?

[hrissan]

How many restarts will SES-8 do?

just one

What's the smiley for?  Don't spacecraft typically perform multiple burns to get from GTO to GSO?  More so if they need to lower apogee?  It it true that SES-8 will only burn twice (one burn, one restart  ?

The question contains too bold statement, that invites a smile.
Compare to "How many restarts SES-8 flight profile requires"?, the answer is "just one", without smile.

Lots of people will feel uneasy until the engine actually restarts. The only previous attempt failed.

Edit: better English.

[Jason1701]

How many restarts will SES-8 do?

just one

What's the smiley for?  Don't spacecraft typically perform multiple burns to get from GTO to GSO?  More so if they need to lower apogee?  It it true that SES-8 will only burn twice (one burn, one restart  ?

The question contains too bold statement, that invites a smile.
Compare to "How many restarts SES-8 flight profile requires"?, the answer is "just one", without smile.

Lots of people will feel uneasy until the engine actually restarts. The only previous attempt failed.

Edit: better English.

The answer to "how many restarts will SES-8 do" will probably be tens of thousands, over ~15 years.

[corrodedNut]

SES posted a few pictures of the satellite arriving at the Cape: https://www.facebook.com/media/set/?set=a.677725285592988.1073741840.257596920939162&type=1

The payload adapter doesn't look very big, does it?

[russianhalo117]

SES posted a few pictures of the satellite arriving at the Cape: https://www.facebook.com/media/set/?set=a.677725285592988.1073741840.257596920939162&type=1

The payload adapter doesn't look very big, does it?

it could be due to the camera distance and angle.

[kch]

How many restarts will SES-8 do?

just one

What's the smiley for?  Don't spacecraft typically perform multiple burns to get from GTO to GSO?  More so if they need to lower apogee?  It it true that SES-8 will only burn twice (one burn, one restart  ?

The question contains too bold statement, that invites a smile.
Compare to "How many restarts SES-8 flight profile requires"?, the answer is "just one", without smile.

Lots of people will feel uneasy until the engine actually restarts. The only previous attempt failed.

Edit: better English.

The answer to "how many restarts will SES-8 do" will probably be tens of thousands, over ~15 years.

Oh, this is too funny (and so typical)!  You guys are using the same name -- SES-8 -- for two different things (the satellite (correct) and the booster (Incorrect™)), and talking past each other.  Oh, well ... as Dark Helmet once said, "Keep firing!" 

[kevin-rf]

And I assume the combination on your luggage is 1-2-3-4

[kch]

And I assume the combination on your luggage is 1-2-3-4

"So, at last we meet for the first time for the last time."   

[Jason1701]

SES posted a few pictures of the satellite arriving at the Cape: https://www.facebook.com/media/set/?set=a.677725285592988.1073741840.257596920939162&type=1

The payload adapter doesn't look very big, does it?

it could be due to the camera distance and angle.

There's a larger frustum-shaped Payload Attach Fitting that's not shown.

[sdsds]

SES posted a few pictures of the satellite arriving at the Cape: https://www.facebook.com/media/set/?set=a.677725285592988.1073741840.257596920939162&type=1

Are we seeing in the photos both halves of the payload fairing, one marked with the "SES^" logo and one marked with an American flag?