SpaceX Falcon 9 : Telstar 18 Vantage/Apstar-5C : Sept 10, 2018 - DISCUSSION

[ZachS09]

Second part of the Telstar 18V launch photos taken from ERAU Daytona Beach.

There was a big cloud deck that obstructed the rest of the flight from T+90 seconds onward.

[jbenton]

I liked how they used a graphic of Martian terraforming as a placeholder for their webcast long prior to the launch:



They've probably been doing that for awhile, but this is the first SpaceX launch I've watched live in some time.

[amarkit]

A first object has been cataloged:

2018-069B/43612 in 259 x 18060 km x 26.95°

Which works out to GTO-2267. Very similar to Telstar 19V (243 x 17863 km x 27.00º orbit, GTO-2277).

[Lar]

I liked how they used a graphic of Martian terraforming as a placeholder for their webcast long prior to the launch:

They've probably been doing that for awhile, but this is the first SpaceX launch I've watched live in some time.

yep, standard. And awesome.

[wannamoonbase]

Congrats SpaceX on a clock work like launch.  I didn't think the weather was going to cooperate.

It's amazing that the F9 can deliver such a heavy payload, even with reduced delta V. 

I wonder if these big birds move over to the FH in a year or two.

Well done SpaceX, next up RTLS on the west coast

[blaze79]

Which works out to GTO-2267. Very similar to Telstar 19V (243 x 17863 km x 27.00º orbit, GTO-2277).

Can anybody explain why they used orbits with so large delta-v? Is it  advantageous for satellite company to built heavy satellite with large amount of fuel to make ~2200 m/s maneuvr?

[e of pi]

Which works out to GTO-2267. Very similar to Telstar 19V (243 x 17863 km x 27.00º orbit, GTO-2277).

Can anybody explain why they used orbits with so large delta-v? Is it  advantageous for satellite company to built heavy satellite with large amount of fuel to make ~2200 m/s maneuvr?

Because Falcon 9 has a kerosene upper stage, it's performance changes pretty rapidly with the delta-v required. Customers really, really want to get the price from SpaceX they can get from letting SpaceX recover the core, so they need to let SpaceX have the margin for propellant to land on the barge. That means lower first-stage delta-v and higher second stage delta-v, which drops payload pretty quickly.

For instance, while F9 with ASDS landing can deliver about 7 metric tons to this GTO-2270 orbit, it can only deliver about 4 metric tons to GTO-1800. That's the difference between the satellite making it to GTO with a beginning-of-life mass of 3.05 metric tons or 3.35 metric tons. Thus, by loading the satellite with more propellant and having it act more as its own "third stage," you can more efficiently split the delta-v and get almost 10% more mass to geostationary orbit--and more importantly launch a bus of a commercially standard size while still allowing the core to be recovered.

Given how well this size fits on F9 with this mission mode, I'm not sure I'd see satellites of this size switching to Falcon Heavy. However, anything larger would need to, as there's not much further the technique can be pushed.

EDIT: Numbers adjusted per correction below by envy887.

[LouScheffer]

Which works out to GTO-2267. Very similar to Telstar 19V (243 x 17863 km x 27.00º orbit, GTO-2277).

Can anybody explain why they used orbits with so large delta-v? Is it  advantageous for satellite company to built heavy satellite with large amount of fuel to make ~2200 m/s maneuvr?

Sure.  It's more efficient since there is no need to push the dead mass of the second stage into a high orbit.

The Falcon 9 can push about 5500 kg to a typical GTO orbit with an apogee of 35,768 km.

The orbit here (18,000 km apogee) needs about 468 m/s to match this orbit.  From the rocket equation, and using a typical satellite motor ISP of 320, the mass ratio needed is exp(468/(320*9.8 )) = 1.161.   So if the initial mass is 7050 kg, then after the apogee raising burn the spacecraft mass is 7050/1.161, or about 6081 kg.  This mass advantage will be somewhat reduced by the need for larger tanks, but it's still a net win.

So overall, by using this strategy, the satellite manufacturer gets about 500 kg more to a GEO-apogee GTO than they would have gotten from the F9 directly.

[envy887]

Which works out to GTO-2267. Very similar to Telstar 19V (243 x 17863 km x 27.00º orbit, GTO-2277).

Can anybody explain why they used orbits with so large delta-v? Is it  advantageous for satellite company to built heavy satellite with large amount of fuel to make ~2200 m/s maneuvr?

Because Falcon 9 has a kerosene upper stage, it's performance changes pretty rapidly with the delta-v required. Customers really, really want to get the price from SpaceX they can get from letting SpaceX recover the core, so they need to let SpaceX have the margin for propellant to land on the barge. That means lower first-stage delta-v and higher second stage delta-v, which drops payload pretty quickly.

For instance, while F9 with ASDS landing can deliver about 7 metric tons to this GTO-2270 orbit, it can only deliver about 4 metric tons to GTO-1800. That's the difference between the satellite making it to GTO with a beginning-of-life mass of 2.25 metric tons or 3.35 metric tons. Thus, by loading the satellite with more propellant and having it act more as its own "third stage," you can more efficiently split the delta-v and get almost 50% more mass to geostationary orbit--and more importantly launch a bus of a commercially standard size while still allowing the core to be recovered.

Given how well this size fits on F9 with this mission mode, I'm not sure I'd see satellites of this size switching to Falcon Heavy. However, anything larger would need to, as there's not much further the technique can be pushed.

Block 5 can do much better than 4,000 kg to GEO-1800 with a landing. F9 Block 3 has delivered 5200 kg to a super synchronous GEO-1773 with ASDS landing, and Block 5 is substantially more powerful. It can do at least 5,500 kg to GEO-1800, and probably more, depending how hot they want to let the booster get on entry.

https://forum.nasaspaceflight.com/index.php?topic=40725.msg1735694#msg1735694

[e of pi]

Block 5 can do much better than 4,000 kg to GEO-1800 with a landing. F9 Block 3 has delivered 5200 kg to a super synchronous GEO-1773 with ASDS landing, and Block 5 is substantially more powerful. It can do at least 5,500 kg to GEO-1800, and probably more, depending how hot they want to let the booster get on entry.

https://forum.nasaspaceflight.com/index.php?topic=40725.msg1735694#msg1735694

It looks like I misread the NLS II tool outputs, and read the line for "F9 Full Thrust with ASDS landing, 2000 km perigee." Thanks for pointing out that error...I'm a little unsure why they even have that option in the table? The actual value should be about 5450 from the NLS-II tool, and I'll edit my earlier post.

[JimO]

A first object has been cataloged:

2018-069B/43612 in 259 x 18060 km x 26.95°

Then about 2267 m/s to get to GEO.  468 m/s at perigee to raise apogee to GEO , then 1799 m/s at apogee to circularize and remove inclination.

Any idea when the perigee burn will be made? Since it will use s/c thrusters I have no hope it would make a visible plume.

Did stage-2 do a small apogee slow-down burp to deorbit?

[input~2]

A first object has been cataloged:

2018-069B/43612 in 259 x 18060 km x 26.95°

and Object A has now been cataloged:

2018-069A/43611 in 259 x 18098 km x 26.93°

[input~2]

Did stage-2 do a small apogee slow-down burp to deorbit?

Apparently yes

[John Alan]

A first object has been cataloged:

2018-069B/43612 in 259 x 18060 km x 26.95°

and Object A has now been cataloged:

2018-069A/43611 in 259 x 18098 km x 26.93°

Did stage-2 do a small apogee slow-down burp to deorbit?

Apparently yes

It may have burped a little... but with two objects being cataloged... was not enough to deorbit...
And at 259km... S2 will be up there a few years... 

[Alexphysics]

A first object has been cataloged:

2018-069B/43612 in 259 x 18060 km x 26.95°

Then about 2267 m/s to get to GEO.  468 m/s at perigee to raise apogee to GEO , then 1799 m/s at apogee to circularize and remove inclination.

Any idea when the perigee burn will be made? Since it will use s/c thrusters I have no hope it would make a visible plume.

Did stage-2 do a small apogee slow-down burp to deorbit?

They don't have the capacity right now to deorbit second stages on GTO missions and this should be on the discussion thread.

[spacetraveler]

I wonder if these big birds move over to the FH in a year or two.

Why would they do that?

It seems obvious that Telstar decided to trade launcher performance for lower cost with these launches in electing to put up a heavy fuel mass in the sat to a subsynchronous GTO. Switching to FH would be going in the opposite direction.

[John Alan]

I wonder if these big birds move over to the FH in a year or two.

Why would they do that?

It seems obvious that Telstar decided to trade launcher performance for lower cost with these launches in electing to put up a heavy fuel mass in the sat to a subsynchronous GTO. Switching to FH would be going in the opposite direction.

SSL had $28 million reasons to put another ~500m/s on the bird and make it work on F9 ASDS single stick... 
https://www.spacex.com/about/capabilities

[nacnud]

I tried to look up the cost delta, thanks. Seeing the trade between hypergol, ion thrusters, cost and revenue would be interesting.

[Lar]

I tried to look up the cost delta, thanks. Seeing the trade between hypergol, ion thrusters, cost and revenue would be interesting.

Was the bird built on a bus that allows swapping out hypergol vs ion thrusters? What about adding larger fuel tanks?

[Targeteer]

A first object has been cataloged:

2018-069B/43612 in 259 x 18060 km x 26.95°

Then about 2267 m/s to get to GEO.  468 m/s at perigee to raise apogee to GEO , then 1799 m/s at apogee to circularize and remove inclination.

How much fuel does 2267 m/s require?