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

[QuantumG]

Here's a title

Long Days and Sleepless Nights........

Cherish them.

[R7]

Open SESame

[input~2]

From SES press release dated Sept 30, 2013

The next SES launch is scheduled for October 2013, when a SpaceX Falcon 9 booster will orbit the SES-8 spacecraft, manufactured by Orbital, from Cape Canaveral, Florida.

[Galactic Penguin SST]

Anyone knows the rough launch window for this launch? Evening time (like most geosynchronous-transfer bound satellites from the Cape) I guess?

[fatjohn1408]

In honour of the geostationary orbit, I'll suggest "The Day the Earth Stood Still" for the party thread.

I like this better than anything I've come up with.

I'll third that

[fatjohn1408]

Right now the question has to be what happened during yesterdays second stage relight? If there was a failure, would I allow my super expensive satellite to take a ride on a vehicle that is dependent on a relight of the second stage? If I had booked a secondary launch vehicle provider would I take my business there and cancel the current contract? I'm pretty sure that these conversations are going on.

Is this really the case? Any reference, or just going by the low staging velocity?

[ugordan]

Is this really the case? Any reference, or just going by the low staging velocity?

Orbital mechanics. You insert into a low parking orbit (low to minimize gravity losses) and then once you cross equator you do the 2nd burn for the GTO transfer. You want to do that 2nd burn near the equator because then a prograde burn will also make the apogee be located over the equator - which is where you want it to be. That's the best case, performance-wise.

You could, in theory, do the same GTO orbit injection with a single burn, but since CCAFS is at 28 deg latitutde, you would need to go really high to insert into into the descending node of an orbit equivalent to that original GTO transfer. Since a GTO transfer orbit is fairly eccentric, it picks up altitude fairly quickly away from perigee (equator) so the groundtrack over the launch site would be at a high altitude. My W.A.G. is several hundred km.

[Prober]

Is this really the case? Any reference, or just going by the low staging velocity?

Orbital mechanics. You insert into a low parking orbit (low to minimize gravity losses) and then once you cross equator you do the 2nd burn for the GTO transfer. You want to do that 2nd burn near the equator because then a prograde burn will also make the apogee be located over the equator - which is where you want it to be. That's the best case, performance-wise.

You could, in theory, do the same GTO orbit injection with a single burn, but since CCAFS is at 28 deg latitutde, you would need to go really high to insert into into the descending node of an orbit equivalent to that original GTO transfer. Since a GTO transfer orbit is fairly eccentric, it picks up altitude fairly quickly away from perigee (equator) so the groundtrack over the launch site would be at a high altitude. My W.A.G. is several hundred km.

Well written and easy to understand thx. 

[Galactic Penguin SST]

We've got the new exact launch date (launch time included!) on L2!  I'll leave the formal announcement to Chris for that....... 

[Lars_J]

Right now the question has to be what happened during yesterdays second stage relight? If there was a failure, would I allow my super expensive satellite to take a ride on a vehicle that is dependent on a relight of the second stage? If I had booked a secondary launch vehicle provider would I take my business there and cancel the current contract? I'm pretty sure that these conversations are going on.

Is this really the case? Any reference, or just going by the low staging velocity?

Aren't GTO launches from most launch providers accomplished using multiple upper stage burns? (Ariane 5 may be an exception due to their favourable launch location)

[aga]

will the shutdown somehow influence the ses-8 launch? or not at all? ccafs?

[pippin]

Is this really the case? Any reference, or just going by the low staging velocity?

Orbital mechanics. You insert into a low parking orbit (low to minimize gravity losses) and then once you cross equator you do the 2nd burn for the GTO transfer. You want to do that 2nd burn near the equator because then a prograde burn will also make the apogee be located over the equator - which is where you want it to be. That's the best case, performance-wise.

You could, in theory, do the same GTO orbit injection with a single burn, but since CCAFS is at 28 deg latitutde, you would need to go really high to insert into into the descending node of an orbit equivalent to that original GTO transfer. Since a GTO transfer orbit is fairly eccentric, it picks up altitude fairly quickly away from perigee (equator) so the groundtrack over the launch site would be at a high altitude. My W.A.G. is several hundred km.

Well, I actually have no information in whether they will use two burns but didn't they announce that they plan to insert into a supersynchronous orbit? That could get them into a GTO with the required delta-v even without a plane change so that they might indeed only need a single burn.

I also assumed they'd need two burns so far but thinking about it I'm not so sure anymore.

[mr. mark]

I guess SpaceX just gave confirmation that there was no rupture to the second stage on the Cassiope mission. Good to know.

[ChefPat]

I guess SpaceX just gave confirmation that there was no rupture to the second stage on the Cassiope mission. Good to know.

Where did they give confirmation?

[mr. mark]

https://twitter.com/flatoday_jdean/status/385079753922736128

Here...

[ugordan]

Well, I actually have no information in whether they will use two burns but didn't they announce that they plan to insert into a supersynchronous orbit?

Pretty much the same scenario, just the apogee is above GEO altitude. You still want the apogee to happen at an equatorial crossing.

[Lars_J]

https://twitter.com/flatoday_jdean/status/385079753922736128

Here...

It is always useful to quote in case of tweets being deleted:

James Dean
‏@flatoday_jdean
SpaceX statement re. speculation about F9 upper stage anomaly: "our data confirms there was no rupture of any kind on the second stage."

[malu5531]

My performance calculations for this mission.

As usual, since we don't have all specs, there are some assumptions made for best fit with other data.

I calculate a delta-v margin of 574 m/s for GTO in this mission (no fuel margin in first stage for RTLS). After releasing the payload, the second stage has an extra 980 m/s delta-v (1.6% residual fuel), which ought to be enough for earth departure (TMI? ), hope they go for that! (might require second restart?)

When I calculate using ~10% residual fuel for RTLS there is a negative delta-v margin for the mission (~-200 m/s). My guess is that SpaceX wanted/had planned to try reuse (as per post CRS2 conference), but could not fully determine the performance of the stack during CASSIOPE launch, and thus decided (perhaps forced through contracts with customers) not to try for reuse on upcoming GTO missions.

[ugordan]

which ought to be enough for earth departure (TMI? ), hope they go for that! (might require second restart?)

As per Elon's press conference, the Cassiope burn to depletion was to have been directed sideways, not prograde. Similar to what they did with Falcon 1 depletion burns. Makes it even less likely they'd do a prograde burn after SES-8. At this point, they'll probably be happy just to get that one engine restart required by the mission.

[ugordan]

So soon? I am surprised problem with upper stage did not caused bigger delay.

Give it time, it probably didn't have a chance to propagate around to all the schedules and plans, yet.