SpaceX Falcon 9 : Telstar 19 Vantage : July 22, 2018 - DISCUSSION

[rickl]

It looked to me like the second stage was moving oddly after the second engine cutoff.

[Lars-J]

Little bit of tumble on the payload?

Happened for the last launch too, looks like the whole F9US and payload was spun slightly - presumably to ensure that separation would occur even if some pushers failed?

[Elthiryel]

If I remember correctly, many satellites manufactured by SSL were released this way, but I would have to check previous webcasts to confirm.

[edkyle99]

Looked like a subsynchronous injection to me (32,670 - 26,504 km/hr ~=1,712 m/s delta-v) on that second burn, though the stage had already slowed by the time they showed the last velocity so the actual delta-v should be a bit larger. 

 - Ed Kyle

[LouScheffer]

Looked very sub-synchronous.  Telemetry froze for a while, but when it resumed (at 30:43) it showed 32835 km/hr = 9120 m/s.   Add in the 402 m/s from Earth's rotation, to get 9522 m/s.  That's about a 14000 km apogee (assuming no inclination reduction), and another 600 m/s to go to get to a nominal GTO.  So GEO - 2400 m/s.     

[DigitalMan]

That was quite a long trail of green as S2 lit up.  I guess I hadn't noticed that before.  I didn't see a jellyfish plume on S2 this time, perhaps it needs light reflecting off it from the sun or moon. 

Great launch.

[Robotbeat]

I don’t remember seeing that much tumble on previous launches. I doubt it’s a concern but is different.

[DigitalMan]

I don’t remember seeing that much tumble on previous launches. I doubt it’s a concern but is different.

Tumble of the satellite, yea.  Perhaps the CG is in a peculiar place.

[Elthiryel]

Hispasat 30W-6 was also based on SSL-1300 platform and separation looks almost the same (from 44:54).

https://www.youtube.com/watch?v=Kpfrp-GMKKM?t=44m54s

[Nehkara]

I remember hearing/reading that it's intentional.  As you could see, right before the satellite was deployed, stage 2 purposefully altered its orientation and then released it.

[Lars-J]

That was quite a long trail of green as S2 lit up.  I guess I hadn't noticed that before.  I didn't see a jellyfish plume on S2 this time, perhaps it needs light reflecting off it from the sun or moon. 

Great launch.

You'll only see a jellyfish if the launch is just before dawn or after sunset. The 2nd stage plume needs to be illuminated by the sun to create that effect, and in this case the 2nd stage did not get into sunlight until a couple of minutes after engine cutoff.

[DigitalMan]

That was quite a long trail of green as S2 lit up.  I guess I hadn't noticed that before.  I didn't see a jellyfish plume on S2 this time, perhaps it needs light reflecting off it from the sun or moon. 

Great launch.

You'll only see a jellyfish if the launch is just before dawn or after sunset. The 2nd stage plume needs to be illuminated by the sun to create that effect, and in this case the 2nd stage did not get into sunlight until a couple of minutes after engine cutoff.

Yea, too far away by then for me to see it with my binoculars.

[Steven Pietrobon]

Some interesting screen grabs.

Interstage gets a toasting.
A blue plume during fin deployment.
First stage goes below the horizon.
Drone ship.
Picture brightens from first stage engine.
Can just see engine flame before loss of signal.
Unstable video connection.
Landed vehicle in better focus.

[edkyle99]

Looked very sub-synchronous.  Telemetry froze for a while, but when it resumed (at 30:43) it showed 32835 km/hr = 9120 m/s.   Add in the 402 m/s from Earth's rotation, to get 9522 m/s.  That's about a 14000 km apogee (assuming no inclination reduction), and another 600 m/s to go to get to a nominal GTO.  So GEO - 2400 m/s.     

That's what I'm getting too, something like a 250 x 14,000 km (or less) orbit.  I think we expected subsynchronous, but I wonder about the "very" part. 

 - Ed Kyle

[Alexphysics]

First stage cutoff was at 8170 km/hr = 2270 m/s.

This is exactly what we've seen on previous GTO with recovery missions.   So no big performance boost for block 5.

But keep in mind that this booster shut down at 2:30, other GTO missions had MECO a few seconds later. Block 5 makes a difference here, same speed but earlier in the flight

[Alexphysics]

Am I misremembering, or is MECO normally at around 2.24, whereas today it was about 10 seconds later at 2.34? Is there any significance to this, as in a correlation to increased peformance, or is this an optional cutoff point based on mission profile?

GTO missions have MECO around 2:35, the last Block 5 had the MECO time at 2:30 like this one (per the press kit), Block 5 makes difference being at the same speed but a few seconds earlier than with Block 4. What you think about MECO times being around 2:25 is for RTLS missions.

[Rebel44]

Looked very sub-synchronous.  Telemetry froze for a while, but when it resumed (at 30:43) it showed 32835 km/hr = 9120 m/s.   Add in the 402 m/s from Earth's rotation, to get 9522 m/s.  That's about a 14000 km apogee (assuming no inclination reduction), and another 600 m/s to go to get to a nominal GTO.  So GEO - 2400 m/s.     

That's what I'm getting too, something like a 250 x 14,000 km (or less) orbit.  I think we expected subsynchronous, but I wonder about the "very" part. 

 - Ed Kyle

 HISPASAT 30W-6 (with its smaller mass of 6,092 kg) was launched by Falcon 9 Block 4 to 184 x 22,261 km, 26.97°

[docmordrid]

F9 brought out a fan...

Buzz Aldrin ✓ @TheRealBuzz
#Falcon @NASAKennedy @SpaceX https://t.co/VPQ5uL3CFK

[Lars-J]

That was quite a long trail of green as S2 lit up.  I guess I hadn't noticed that before.  I didn't see a jellyfish plume on S2 this time, perhaps it needs light reflecting off it from the sun or moon. 

Great launch.

You'll only see a jellyfish if the launch is just before dawn or after sunset. The 2nd stage plume needs to be illuminated by the sun to create that effect, and in this case the 2nd stage did not get into sunlight until a couple of minutes after engine cutoff.

Yea, too far away by then for me to see it with my binoculars.

Binoculars would have made no difference :-), the stage was way over the horizon and practically over Africa before it hit sunlight.

[yokem55]

Looked very sub-synchronous.  Telemetry froze for a while, but when it resumed (at 30:43) it showed 32835 km/hr = 9120 m/s.   Add in the 402 m/s from Earth's rotation, to get 9522 m/s.  That's about a 14000 km apogee (assuming no inclination reduction), and another 600 m/s to go to get to a nominal GTO.  So GEO - 2400 m/s.   

The variable we won't know until we get TLE's is the inclination. There could be a bunch of inclination reduction in that burn as well that won't show up in the final velocity.