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

[nacnud]

I don't know. The Everyday Astronaut mentioned in his coverage of the launch that having the sat be it's own third stage allowed it to be about 500kg heavier than if the Falcon 9 second stage did all the work. I don't know the source of those numbers.

[LouScheffer]

I don't know. The Everyday Astronaut mentioned in his coverage of the launch that having the sat be it's own third stage allowed it to be about 500kg heavier than if the Falcon 9 second stage did all the work. I don't know the source of those numbers.

The source is fairly straightforward orbital mechanics.  A post upthread goes through the numbers.

[LouScheffer]

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?

Assuming generic engines with an ISP of 320, it takes a factor of exp(2267/(320*9.8 )) = 2.06 in mass.  So if it starts at 7050 kg, it will end up at about 3422 kg at GEO.  So about 3628 kg of fuel.

However, this should all go in Discussion, not updates.  Maybe a mod can move it?

[Steven Pietrobon]

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

I get 2266.7 m/s without a plane change for the first burn. With a plane change I get 2263.1 m/s.

Enter initial perigee height (km): 259
Enter initial apogee height (km): 18060
Enter required inclination change (deg): 26.95
Enter final orbit height (km): -1

theta1 =  0.00 deg, dv1 =  468.1 m/s
theta2 = 26.95 deg, dv2 = 1798.6 m/s
dv = 2266.7 m/s

theta1 =  0.34 deg, dv1 =  471.8 m/s
theta2 = 26.61 deg, dv2 = 1791.3 m/s
dv = 2263.1 m/s

[Ben the Space Brit]

Was it me or was the booster quite far off of the centre mark on OISLY's pad this time?

[Shanuson]

Was it me or was the booster quite far off of the centre mark on OISLY's pad this time?

Last view before landing. Landing confirmed!

Taking the image posted by Chris, it seems to me that it is of less than the diameter of the rocket.

[vanoord]

It's within the circle - a couple of years ago, we were celebrating when the cores didn't explode!

[speedevil]

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.

259-150km, from a 18060km orbit, I get as 18m/s or so, or a hundred kilos or so of nitrogen from cold gas, assuming 5000kg.

The main tanks likely also have well over a hundred kilos of helium and oxygen gas, as well as a notable residual volume of liquid which will be boiling off due to solar heating.
The initial helium pressurisation, if to 3 bar, would be enough naively for 20-40m/s.

Leading to the conclusion that if they can keep pointing, propulsive venting of the tank blowdown soon after satellite release may be enough to deorbit.
(They may choose not to do this for many reasons)

[blaze79]

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.

It does make sense. Was the Telstar 18V specially designed for F9 Block 5?

[CorvusCorax]

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.

259-150km, from a 18060km orbit, I get as 18m/s or so, or a hundred kilos or so of nitrogen from cold gas, assuming 5000kg.

The main tanks likely also have well over a hundred kilos of helium and oxygen gas, as well as a notable residual volume of liquid which will be boiling off due to solar heating.
The initial helium pressurisation, if to 3 bar, would be enough naively for 20-40m/s.

Leading to the conclusion that if they can keep pointing, propulsive venting of the tank blowdown soon after satellite release may be enough to deorbit.
(They may choose not to do this for many reasons)

This is under the assumption that they vent at apogee, for which the stage would have to coast first for 6 hours, THEN orient and vent. I don't know if it has enough battery power for that long coast unless they installed the long-coast package.

If they vent right after sat separation, lowering perigee is extremely inefficient since they are still close to said perigee.

[deadman719]

Getting close! #SpaceX booster 1049 entering port.

https://twitter.com/cygnusx112/status/1039873782608027649

Booster 1049 is back @PortCanaveral after delivering #TelStar18 to orbit. @SpaceX @NASASpaceflight

https://twitter.com/cygnusx112/status/1039878628849410048

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

[Joffan]

Getting close! #SpaceX booster 1049 entering port.

https://twitter.com/cygnusx112/status/1039873782608027649

Booster 1049 is back @PortCanaveral after delivering #TelStar18 to orbit. @SpaceX @NASASpaceflight

https://twitter.com/cygnusx112/status/1039878628849410048

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

I think you're misinterpreting the shadow being cast on the gridfin.

[groknull]

Getting close! #SpaceX booster 1049 entering port.

https://twitter.com/cygnusx112/status/1039873782608027649

Booster 1049 is back @PortCanaveral after delivering #TelStar18 to orbit. @SpaceX @NASASpaceflight

https://twitter.com/cygnusx112/status/1039878628849410048

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

I think you're misinterpreting the shadow being cast on the gridfin.

Shadow likely cast by the thruster pod between the two grid fins.

[deadman719]

Getting close! #SpaceX booster 1049 entering port.

https://twitter.com/cygnusx112/status/1039873782608027649

Booster 1049 is back @PortCanaveral after delivering #TelStar18 to orbit. @SpaceX @NASASpaceflight

https://twitter.com/cygnusx112/status/1039878628849410048

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

I think you're misinterpreting the shadow being cast on the gridfin.

Shadow likely cast by the thruster pod between the two grid fins.

I dont think it is a shadow because one can follow the panel shape under the area that appears to be missing material. This wouldn't be possible if it was a shadow cast on the grid fin. 

[ZachF]

Getting close! #SpaceX booster 1049 entering port.

https://twitter.com/cygnusx112/status/1039873782608027649

Booster 1049 is back @PortCanaveral after delivering #TelStar18 to orbit. @SpaceX @NASASpaceflight

https://twitter.com/cygnusx112/status/1039878628849410048

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

I think you're misinterpreting the shadow being cast on the gridfin.

Shadow likely cast by the thruster pod between the two grid fins.

I dont think it is a shadow because one can follow the panel shape under the area that appears to be missing material. This wouldn't be possible if it was a shadow cast on the grid fin.

It is 100.000% a shadow.

[Joffan]

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

I think you're misinterpreting the shadow being cast on the gridfin.

Shadow likely cast by the thruster pod between the two grid fins.

I dont think it is a shadow because one can follow the panel shape under the area that appears to be missing material. This wouldn't be possible if it was a shadow cast on the grid fin. 

Without spending a lot of time on it, here's contrast/brightness modified version where the true edge of the gridfin is more visible.

[Pete]

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

Only defect is in the eye of the beholder.

Look again, it is right there, same as it has always been.

[meekGee]

Getting close! #SpaceX booster 1049 entering port.

https://twitter.com/cygnusx112/status/1039873782608027649

Booster 1049 is back @PortCanaveral after delivering #TelStar18 to orbit. @SpaceX @NASASpaceflight

https://twitter.com/cygnusx112/status/1039878628849410048

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

I think you're misinterpreting the shadow being cast on the gridfin.

Shadow likely cast by the thruster pod between the two grid fins.

I dont think it is a shadow because one can follow the panel shape under the area that appears to be missing material. This wouldn't be possible if it was a shadow cast on the grid fin.

You can see the "missing" scallop, it's just gray and similar to the body.  All the places where you see body features within the fin area are where the scallop pattern naturally recedes.

Also, draw a line parallel the shadow direction from the gas thruster to the fin... Voila.

[deadman719]

Does any care to guess why the right side of the left gridfin, in the cropped photo, have a different leading edge pattern than previously seen? Could it be the result of a manufacturing defect?

Only defect is in the eye of the beholder.

Look again, it is right there, same as it has always been.

Yep...my eyes failed me. Grid fin 1, me...0.

[ZachS09]

If SpaceX says they’re gonna transport Block 5 boosters from Port Canaveral to its hangar with the legs folded up, how come they’ve been removing the legs after temporarily folding up one of the legs?

I ask that because in the Telstar 18V Update Thread, what I mentioned above was what happened.