SpaceX Falcon 9 v1.1/Thaicom-6 Pad Thai Party Thread

[sanman]

Why do they need to coast in between? Why can't they just burn until they get into the right orbit?

[butters]

Why do they need to coast in between? Why can't they just burn until they get into the right orbit?

Because LC-40 isn't on the equator

[e of pi]

Why do they need to coast in between? Why can't they just burn until they get into the right orbit?

It's more efficient this way. They could do it that way, but it'd yield less payload.

[sanman]

Since this is the party thread, I need to ask an important question that shouldn't have asked on the updates thread... whatever happened to the original Sci-Fi Rocket Chick?

You mean that perky blonde lady? Maybe they needed her for engineering-related stuff.

I'm just glad that Mr Bartles & James is still there as MC. 

[Lars_J]

Why do they need to coast in between? Why can't they just burn until they get into the right orbit?

Because that is the most efficient way to do it.

[NovaSilisko]

It's not a straight-up prograde burn, either. They're changing inclination too, as Lars said. Part of that is done by the second stage, and the rest is done by the spacecraft at apoapsis (to my knowledge)

Doing the GTO burn straight after launch at Canaveral would leave the ascending nodes of the orbit at the wrong positions, as well.

[Ben the Space Brit]

Why do they need to coast in between? Why can't they just burn until they get into the right orbit?

Because the launch site and SECO1 are fixed points, the final orbital alignment of the spacecraft is not. The SEI2 burn can thus be timed to allow a spacecraft from CCAFS to reach a GEO position over any point over the equator. If you burned all the way from launch, it could only reach more or less one point over the equator.

[cambrianera]

Good thing: SpaceX learning how to make launches boring.
Fortunately they have some hidden aces to keep us excited 

[StephenB]

Think of a swingset. It's easier to change the direction of the person on the swing when it is at the top of the arc. In the case of the satellite, the analogous spot would be at apogee over the equator.

[Sohl]

Great countdown and launch!  Hope the 2nd burn of 2nd stage goes well. 

[Wetmelon]

There is a second upper stage burn (due to start at 22:33UT) that will push the apogee up into the range of 40,000km. The spacecraft is only separated after that is complete.

This is going to supersync ~ 90,000km iirc.  But yeah same reason.

[Lars_J]

Why do they need to coast in between? Why can't they just burn until they get into the right orbit?

Because the launch site and SECO1 are fixed points, the final orbital alignment of the spacecraft is not. The SEI2 burn can thus be timed to allow a spacecraft from CCAFS to reach a GEO position over any point over the equator. If you burned all the way from launch, it could only reach more or less one point over the equator.

Not quite correct. The timing of the SECO1 and restart will be the same on ALL GTO launches from CCAFS - independent of the final destination in geosynchronous orbit. The engine restart will happen as it crosses the equator.

The GTO orbit that the satellite is released to is gradually tweaked by the satellite through multiple burns to arrive at the proper location.

[NovaSilisko]

There is a second upper stage burn (due to start at 22:33UT) that will push the apogee up into the range of 40,000km. The spacecraft is only separated after that is complete.

This is going to supersync ~ 90,000km iirc.  But yeah same reason.

What was SES-8? Wasn't that only 80,000?

[Ben the Space Brit]

Good thing: SpaceX learning how to make launches boring.

Yeah, I've long said that SpaceX's real arrival as a launch service provider would be when their launches are as boring, predictable and routine as ULA's.

[Wetmelon]

There is a second upper stage burn (due to start at 22:33UT) that will push the apogee up into the range of 40,000km. The spacecraft is only separated after that is complete.

This is going to supersync ~ 90,000km iirc.  But yeah same reason.

What was SES-8? Wasn't that only 80,000?

Yes.

[Sesquipedalian]

Well, that was easy. Sooooo... Lurker Steve, 'bout that beer.

I bet he's cursing the ISS pump issue right about now.  Orb-1 could have beaten Thaicom-6 if that hadn't happened.

[Chris Bergin]

Hey, I think we just got retweeted by the drummer from Green Day!

[Mader Levap]

Yeah, I've long said that SpaceX's real arrival as a launch service provider would be when their launches are as boring, predictable and routine as ULA's.

Don't worry, we will have plenty things to be excited about. Abort tests, stage recovery, in next years FH launch, first launch with reused stage, crew launch...

[Lar]

Not quite correct. The timing of the SECO1 and restart will be the same on ALL GTO launches from CCAFS - independent of the final destination in geosynchronous orbit. The engine restart will happen as it crosses the equator.

Another minor quibble, wouldn't the time that the vehicle crosses the equator (measured in seconds post launch) be determined by things such as when the vehicle pitched over, how long the first stage burn was, what the elements of the initial orbit are, and so forth?

That is, the time is going to be "roughly" the same but may vary a bit due to these factors, no?

I may be confused.

[Norm38]

I'm wearing my lucky SpaceX shirt. 3 for 3 now on v1.1 launches, and no I wasn't wearing it for both SES-8 scrubs. So that clinches it. I have to wear it for every launch this year.